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GEOL6363 Carbonate Sedimentalogy - Day2 01-21-2023 PM
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00:00 Hey you time. Okay. We're to continue our discussion of the three
00:10 carbonate hygienic environments. We've gone through marine environment where you've seen because of
00:16 nature of seawater chemistry that if anything , die genetically. It's gonna involve
00:24 the precipitation. Alright. But I'm show you a variation on the theme
00:29 for this a little bit later. the second conventional near surface digest
00:37 the so called freshwater digest environment. obviously to get your marine carbonates exposed
00:43 freshwater normally, you have to drop level to some degree or you have
00:48 have a carbon A system build topography sea level to create an island.
00:53 I showed you before lunch where that with the beach rock was developed.
01:00 island actually has a freshwater lance on . So in a classical freshwater di
01:07 environment, there are three elements. is the bait ozone above the water
01:14 , which is right here, there a shallow freshwater frantic zone. The
01:19 table would be the top of frantic again. Just means that the
01:24 system is completely saturated by freshwater Bezos it sits above the water table only
01:31 fresh water when it rains and the percolates down through the sediment or rock
01:36 then there's a mixing between the offshore and shallow water. Uh shallow freshwater
01:44 environment that's called the mixing zone. this is where people were going to
01:49 about Dolomites later today, this is people want to make dolomite. But
01:54 turns out and all the modern mixing environments. The die genesis and the
01:59 mixing zone basically behaves just like the genesis and the blue free attic uh
02:06 of that fresh water system. Okay all of this die genesis is by
02:12 occurs before the onset of pressure Okay so let's talk about some of
02:19 conditions and processes associated with the freshwater . Fresh water means drinkable water so
02:27 under saturated with respect to calcium Again in the beta zone above the
02:32 table the pores are filled with air a little bit of water trapped by
02:36 force. Okay because it is above water table and then the fractal zone
02:43 the water table of pores are always with fresh water. So if anything's
02:48 to happen die genetically, it's gonna dissolution of carbonate material that's unstable and
02:55 water and that is initially a Right? So reaganite will start to
03:02 when exposed to fresh water. That's we call fabric selective dissolution. But
03:08 you give the system time and you vegetation involved where the vegetation can create
03:12 . 02 and charge some of that water to make it a little bit
03:16 acidic. You can start to get your your dissolution and that's what creates
03:21 car certification that we see associated with of these exposed carbonates of course with
03:28 solution comes segmentation because of donor Dia genesis. Now the cement are
03:34 different than what I showed you for marine environment. They are clear inclusion
03:40 , so they're white and reflected They're relatively finely crystalline and by that
03:46 mean we're talking tens of microns to few 100 microns across for scale.
03:52 are mostly equal dimensional. Although some them start off with that stubby bladed
03:59 . The dog to spar morphology I about and now there are more stable
04:04 of low matt calcite which is highly in fresh water. Okay, and
04:11 , the good thing about this style dia genesis is that if you can
04:14 the cement, they are pre compaction by definition they occur before the onset
04:19 pressure solution and that can help impede pressure solution and preserve prostate depth.
04:26 exposure to fresh water processes and products the second way to preserve brosius
04:33 Okay, if that's your strategy trying hold on to that process. E
04:37 would be another way to do All right. Obviously, there are
04:42 number of controls that have to be here. You need some period of
04:47 to fresh water and don't assume every a succession gets exposed to freshwater.
04:53 they just get buried progressively because you're more highly subsiding basin. But even
04:59 they do get exposed, they still some length of time to allow reaction
05:04 the fresh water. Usually that means have to be in a pretty rainy
05:09 where you can generate freshwater lenses and like that. So in a dry
05:13 climate, you would not expect to as much freshwater alteration. The starting
05:19 is a major control here because Aragon is much more prone to dissolution.
05:24 arrogant. I dominated systems are more to see the effects of fresh water
05:30 to the pure cal civic uh Some of this ties again back to
05:36 strategic graffiti, the age of the , right? Some geological time
05:41 We had more calcified material, some time periods. We had more magnetic
05:47 and some of this is also faces for example are deep water carbonates in
05:52 Mesozoic and tertiary are dominated by low calcite constituents. The plank for a
05:58 for the plastic microfossils that make up chalk uh sediments. Right? They're
06:06 gonna dissolve in freshwater. And we that from, we know that from
06:13 famous white cliffs of Dover in They're made up of the White Chalk
06:19 . They've been exposed to barely for million years and they still have essentially
06:24 deposition of ferocity. Okay, so they have not been buried. All
06:29 , so they don't dissolve in fresh . Alright, and then you need
06:35 , You can't just like with the Dia genesis, you have to have
06:39 , the wave has to break across reef every 10 seconds or so or
06:44 have to have recharged related to tidal . Same relationship here with fresh
06:49 you can't dissolve and cement to the we see from one poor volume of
06:54 . So you have to have recharged promote that. So there are a
07:00 of different ways to move fresh water these sediments. Alright. Uh one
07:06 , probably one of the least effective to be a situation like I showed
07:09 before lunch with that island that had beach rock That island has, as
07:14 said, has a freshwater lens, about five ft thick. And how
07:18 does it move? It moves two three ft up during high tide,
07:22 or three ft down during low tide that's the extent of the movement.
07:27 , that's not a lot of And so it's gonna take some time
07:30 alter highly those carbonates that are exposed that fresh water contrast that to a
07:36 aquifer system like we have here in , the Edwards aquifer in central texas
07:44 about 100 miles north of san Antonio down south of san Antonio, that's
07:50 hydrological feature. We have the same of thing in florida. The florida
07:56 charges in lake Okeechobee in central florida all the way down through the
08:02 down to Miami goes offshore and 50 offshore, bubbles up in 100 ft
08:08 water. Okay, so that's a different way of moving freshwater compared to
08:13 more isolated freshwater lenses like this bottle . So that's something you'd want to
08:18 in to your evaluation. Alright, course, if you tectonic lee
08:23 then you have the potential to push stuff further offshore by creating a stronger
08:31 . Okay, so what I want do with this discussion is first,
08:37 want to talk about the physical expressions long term severe real exposure. You
08:44 or may not know this, but a lot of controversy in the carbonate
08:47 over the effects of sea level on only carbonate faces development, sequence photography
08:54 die genesis and also die genesis. right. And and the controversy comes
09:01 the fact that some people approach this from the strata graphical side of things
09:07 other people come at it from the or die genetic side. But you
09:13 , there's we'll get into this a bit uh probably next week that the
09:21 photography and carbonates, the Exxon model the C level as a driver for
09:27 carbonates and classics. And the strategy are a byproduct of the changes in
09:33 level. And they turn that around seismic. They used strategy geometries to
09:38 you what sea level is doing through time and of course they try to
09:42 plays off of that relationship. And some problems with that in the carbonate
09:51 of things that we need to talk , we will talk about uh next
09:56 weekend. But irrespective of that. somebody wants to tell you, I've
10:03 a type one on conformity based on I see on straddle geometries of
10:08 which implies that the whole carbonate platform severely exposed for some longer period of
10:14 . Then they should be able to that with Iraq created right? Especially
10:18 carbonate succession because carbonates are very Several exposure and freshwater dia genesis.
10:25 , the way you would answer this is the first come at it from
10:29 physical expression of long term severe real . What are the kinds of things
10:34 want to see an outcrop in It would tell you that that carbonated
10:39 was exposed severely for some period of . And that would include everything from
10:45 cars, to terra rossa, to micro cars on a finer scale
10:50 the soil crust. Colicky profiles that talked briefly about soil pies,
10:56 I mentioned these pies allergic concretions can in some of these soil profiles.
11:02 the cavernous porosity results from long term exposure and sometimes the roots of these
11:07 collapsed. And you get ingratiation like talked about in our first lecture this
11:12 . Okay, So if somebody tells this carbonate succession was exposed severely over
11:19 area for a long period of I want to see the physical evidence
11:24 . And then I want to see dye genetic evidence. So let's talk
11:27 the physical evidence first, then we'll about the dye genetic evidence.
11:32 Alright, so some of the long-term expressions of of subdural exposure would be
11:38 classical tower karst. So this is south central china. The li river
11:46 through this terrain. And what you're at here are Mississippian and Devonian aged
11:52 stones. They've been severely exposed over years. Okay, and so you
12:00 see the tower cars that have Some of these are up to 2,000ft
12:04 above the river level and internally there major and sometimes commercial caves developed in
12:11 limestone. Alright, so that's obviously term, that's an effective long term
12:17 exposure. Another classical long term effect be what people called terra rosa
12:24 I mentioned when you incorporate any kind aerosol iron into your carbonate succession and
12:30 gets tied up in the freshwater dia , it's going to oxidize to red
12:35 brownish color. So not only do see the dissolution of the carbonate,
12:39 you see the emplacement of these reddish . Okay, so that's a classical
12:45 that's terra rosa soil. Classical expression long term several exposure. This is
12:52 , every place has seen sequence in the caribbean which basically represents these
13:00 something 1000 year old cycles of sedimentation about 100,000 years of several exposure on
13:06 cycle, every one of these sequences capped by fabric that looks like
13:11 This is micro karst. Okay, is the fine scale micro karst
13:16 This is this is created by this related to rain water, but it's
13:21 related to cyanobacteria. Reworking the surface some of this stuff. And of
13:27 , vegetation is part of the story it adds CO two to create soul
13:31 and help drive some of the Okay, so this is what we
13:36 micro cars. And you're looking basically surface of 100,000 years of several exposure
13:43 below the surface, if you develop on the surface below the surface,
13:48 going to develop the soil crust that talked about before. All right.
13:53 that die genetic reddish brown fabric. looks like nick right and thin
13:58 It's not deposition als die genetic It's mag calcite, it's not a
14:04 It's a replacement of the analytic host grain, stone host rock. And
14:11 , that that material, that fluid material is created by freshwater reacting with
14:17 soil above this and passing through the and dissolving and precipitating that material.
14:25 within that profile, this is where get the so called soil pits.
14:29 these look like coated grains. they're coated but they're coated by this
14:34 of fabric here. So it's like concretions that just eats away at part
14:38 the rock to give you these golf like fabrics. Alright. And eventually
14:43 centers of these things will actually dissolve and you're just left with basically what
14:48 like an olive golf ball for a P shaped grain. So sometimes they're
14:53 as api sometimes they're as big as golf ball. Okay? And they
14:57 weather out of these rocks and get cemented back into these rocks as little
15:02 , elliptic deposits. Okay, so of this takes time. Alright.
15:09 have we have modern, we have we call holocene or modern day
15:14 by definition less than 10,000 years We have island development in the Bahamas
15:20 we think some of the islands are to 8000 years old and they're starting
15:24 develop a soil profile, but they show anything like what you see here
15:30 the screen. So we think minimally takes 10 or 20,000 years of several
15:36 to create something like this or to to create something like this.
15:41 and you're not gonna do it with term several exposure. So that's part
15:46 the significance of finding this in the record. And then you'll notice that
15:52 joints or regional fracture patterns will break this stuff. You see an open
15:59 cutting through some of this. But is the joint gonna do? It's
16:02 bring fresh water down into the underlying and that's gonna help promote larger scale
16:09 and cave development. Okay, uh crust really is an impermeable surface.
16:16 , we know this, you'll see from other data later. So you've
16:20 to breach that with some sort of joint or fracture system in order to
16:25 fresh water to occur further down in exposed sequence. But if you can
16:29 that and recharge then you can you do what you can broaden the
16:34 You can go from fabric selected grain to more wholesale dissolution and you can
16:40 fabric that looks like this even in younger pleistocene carbonates. Alright,
16:45 these are cave systems. This is Bahamas definition of a cave is a
16:52 bug. Right, big hole, big enough for a person to walk
16:58 . You can see the people with um the cats on with the miner's
17:04 and you know, cave systems are just big dissolution holes. When you
17:09 this carbonate material, you put it into the system as poor filling
17:15 Right? So, stalactites and See it here in the southern cave
17:19 in the southern Bahamas, that's about m to give you a feel for
17:24 . All right, so, Donna Dia genesis supplies to these case systems
17:30 . Uh I've done a lot of . I did a lot of caving
17:34 I was an undergraduate. I've never a cave system that didn't have stalactites
17:38 stalagmites flow stone, Right. It put some of that material back into
17:44 hole. Alright. It's not just whole All right. If it was
17:49 want to go in it. tourists wouldn't want to go in it
17:52 it looks so ugly. All All right. So donor receptor dia
17:57 obviously operates on a bigger scale to these cave uh formations and the cave
18:04 . Alright, now this is so then what will happen with the roots
18:09 these, of these cave systems? will collapse and this is where you
18:13 the classical grecia. Alright. This called the white rock you see here
18:19 the host dualistic grain stone and that tied up. You graduate that fabric
18:26 you deposit it at the floor of cave and then it can be cemented
18:31 place by the same fabric that The soil crust here acts as support
18:37 cement and has this characteristic reddish brown again, because the iron is being
18:44 by fresh water. Okay, and I said earlier today, when people
18:49 this in the rock record, they interpret this to be several cars,
18:53 related to this phenomenon whenever they see Brexit. Right, okay, so
19:00 just showed you all these what I to be the grander expressions of long
19:03 severe real exposure, the kinds of I would want to see along a
19:08 on conformity that's created by several What Exxon would call a Type one
19:14 . Alright, now, what you to appreciate is that some of these
19:19 like the cave systems here do not everywhere in that exposed sequence Right?
19:27 a really limited Because they're controlled by regional joint patterns. Alright, so
19:34 you look at these islands today in Caribbean, you have a island that
19:38 be you know, five or six in length. And the joint patterns
19:42 sort of North South. And you topography that goes like this up and
19:47 created to pleistocene ridges. Where do collect the water? You collect the
19:52 in the low zones. Right. if you have a regional joint system
19:56 like that, you'll get a cave , then you might go a
19:59 So get another cave and another All right. So what I'm saying
20:04 the whole island is not a big of swiss cheese. All right,
20:07 there's a cave here and then what's between is the country rock? The
20:13 brain stone. It's undergoing a different of dia genesis. And you need
20:18 appreciate that as well. So, country rock is actually undergoing this type
20:25 die genesis where the individual magnetic grains or magnetic fossil material when it gets
20:35 to fresh water, it selectively dissolves . Right, So this is what
20:39 call fabric selective dissolution. Alright. if you give it time, what
20:46 you end up creating what we call bolding ferocity. Okay. And what
20:53 that generate? It generates pore calcite cements that start out like this
20:59 then grate into slightly coarse or echo calcite cement. So basically this is
21:06 representation of donor receptor die genesis you by dissolution and then you locally re
21:14 this material nearby. Okay, local receptor dia genesis. Alright,
21:21 I can't prove to you that we that dude right there and we make
21:25 cement right next door. But I prove you This cemented this cement or
21:32 fluid that this concentrated calcium carbonate doesn't more than 10 or 15 cm before
21:38 re precipitates. Okay, I can that to you and I will here
21:42 a minute. So that's it really Local donor receptor dia genesis. These
21:48 don't travel very far before they re and re precipitate core filling calcite
21:54 So what's the lesson to be learned this Dia genesis here, This is
21:58 cursed, this is fabric selective We're doing what we call porosity
22:05 We're going from a grain stone with principal primary porosity, high permeability to
22:12 leeched grain stone with high porosity and permeability. Okay, so there's a
22:20 to be learned here, right? you're into the world of petro
22:24 right? Where you where you rely the logs to help you interpret a
22:28 of relationships. Petro physicist would read high porosity and maybe in the classic
22:35 you'd assume. Oh that's probably a reservoir, right? But this is
22:39 the mud loggers call heartbreak ferocity. great ferocity, no permeability.
22:46 And so that's your first lesson to learned about log response and carbonates get
22:50 this in more detail later. Just you have ferocity doesn't mean you're gonna
22:56 permeability. And another lesson you're gonna later is just because I have relatively
23:03 porosity. That doesn't mean I don't potential for good reservoir quality because it
23:07 on the type of ferocity and what comes along with that. And I'll
23:13 that later with the case study. , So this is the country
23:19 All right. And so when people things right, they should be,
23:22 should look not just at the cave , but they should look at the
23:26 rock nearby to confirm a comparable timing for dia genesis. All right.
23:32 , just to prove that, excuse , just to, just to prove
23:39 Dragon Knight really is susceptible to freshwater . Here's a thin section of another
23:46 grain stone in the Pleistocene and a a benthic foraminifera as a nucleus.
23:55 look at the this is high mag , Right? I told you these
23:59 don't dissolve in freshwater. And here not dissolved. Right? But look
24:03 all the coatings, they're starting to , okay, so that all the
24:08 stuff is starting to be leached out calcium stuff. Whether it's high mag
24:12 low mag cal side does not dissolve fresh water. Okay, so it
24:16 is fabric selective disillusion. So the rock uh in the upper pleistocene all
24:24 the caribbean generally looks like this for of the islands, it's a little
24:29 stone. All right. This is years of several exposure. Okay,
24:34 is not this is fabric selective Classical processing version, not an ounce
24:40 calcite left in the system. I'm , not an ounce of Iraqi
24:44 Sorry, Iraq and I left in zoo IDs. And look at all
24:48 cement are filled with a more stable of eco dimensional Lomax calcite cement.
24:55 , this is what you would expect see and look at the semester,
24:58 all the way around the grains except they're touching. That's a that's an
25:03 that implies pre compaction segmentation, There's no collapse of the porosity,
25:08 no suturing. Of course these rocks never been deeply buried, but but
25:12 fact that they're not suitor okay, you that this cement was placed early
25:18 their history. Alright, that's the indicator that we want to pay attention
25:25 . Alright, everybody appreciate that So, now let's jump into the
25:30 of cement because the cement do vary terms of the of the cement morphology
25:37 and the distributions depending on which part the freshwater system you're dealing with.
25:43 , if you're in the beta zone the water table. Remember these sediments
25:48 rocks don't see a lot of water when it rains and quickly passes through
25:53 its way down to the freshwater And so you only have time to
25:59 with short time period, you only you can only make a little bit
26:02 secondary process. You can only dissolve parts of these grains here. It's
26:06 take 100,000 years to completely dissolve that out like I just showed you.
26:12 , so get a little bit of dissolution. That provides a potential source
26:17 a little bit of calcite cement. correspondingly we just have a little bit
26:21 calcite cement. And where is it place? It's in place that points
26:26 contact or it's in place on the sides of grains where water gets trapped
26:31 capillary force. Okay, so that a lot like the B truck stuff
26:37 showed you earlier, except it's a style of cement. It's not a
26:42 calcite. Now it's a more stable Micale side fabric. Okay, And
26:47 is where you get the classical meniscus with the curvature, you trap the
26:52 by capillary force and that's where you your precipitation. Right? So actually
26:57 don't do a lot of damage in freshwater vato zone unless you have the
27:01 factor, you have a long time recharge and passage of water through that
27:07 environment and then appreciate the scale of cement. Their tiny. Typically these
27:14 cement are, as I said, of microns too rarely, no more
27:19 a few 100 microns across for This is going to be much finer
27:24 crystals that I'm going to show you the burial setting. Okay. And
27:28 the morphology is mostly eco dimensional and a more stable form of Lomax health
27:34 . All right. That's the vetoes of the story. The free zone
27:40 the water table, obviously the whole system is completely saturated with fresh
27:45 longer residence time with respect to fresh . So the first thing you get
27:51 a grander or greater degree of fabric dissolution the irregular grains dissolve out and
27:58 generates these early pre compaction, Aisa bladed Lomax calcite cement. Okay,
28:06 always the first phase of segmentation. expect it to be icy packets because
28:11 whole poor system is saturated with fresh . And then what happens is these
28:17 start to grow out and they start for that larger pore space and only
28:22 few larger crystals went out and they into more of an equal equal dimensional
28:29 like you see there. So the in the literature, the classical freshwater
28:36 profile is with dissolution is ice. pack is bladed to equal mosaic.
28:44 , but the crystals are still relatively . Alright now there's one unique style
28:51 cement that comes into play first for freshwater system and that is a cement
28:59 syntax ciel or overgrowth cement. And is a larger single crystal of calcium
29:06 , that the scale bar one And it is unique because it precipitates
29:13 around single crystal kind of term Remember the kind of terms we talked
29:19 every piece of anaconda term whether it's plate or spawn spine is one
29:25 And so it's easy for dissolved calcium precipitate on one single crystal. And
29:31 prefer to do that first. so oftentimes in these rocks you'll see
29:37 and segmentation of of these Quran annoyed this kind of cement. Alright,
29:44 this bucks the size of the crystal . Right. These are bigger,
29:49 bigger crystals than what you normally see the standard picture for the freshwater
29:55 Okay And how do we prove These are syntax overgrowth. We go
30:00 cross nipples, we rotate the stage The host brain goes black at the
30:05 time, the overlying crystal goes Black, White, Black,
30:09 every 90° you rotate the microscope stage that is the definition of syntax real
30:17 . Okay, I'll show you a of this in a minute.
30:21 so let's take a look. We'll first with the potatoes and I'm gonna
30:24 you the vato zone from that younger . I showed you with the beach
30:29 . We think that island is only 500 years old. I told you
30:33 developed a freshwater lens. So it a free attic has a water
30:38 Azevedo's above it. This is some the superficial crust or sanitation effect at
30:45 top of the Vegas. You see little bit of dissolution of the woods
30:50 exposure to fresh water correspondingly just a bit of calcite cement. And whereas
30:56 of the cement points of contact, ? Where water is trapped by capillary
31:01 and some of these have the So that's the meniscus style of
31:06 Okay, so again, and in absence of a lot of time,
31:10 don't expect there to be a lot modification to the vetoes. Okay,
31:15 . Fresh water, you gotta give a lot of time. Okay,
31:19 , contrast that with the, with frantic zone, this is from
31:23 Different location and bermuda. This is this is a freshwater aquifer system in
31:32 place of scene. And you can you're gonna see a lot more grain
31:37 here, where the dragon eyes starts dissolve out to a greater extent.
31:41 look at the first phase of pakis, stubby bladed, relatively clear
31:48 white conclusion. Free crystals. And if we back off on
31:53 you can see how decisive. Packers grades into a equipped mosaic toward the
31:59 of the poor. All right, , you notice a greater degree of
32:04 process development here, halal meat is magnetic. It's being dissolved out
32:10 corals also a magnetic being dissolved That's creating a secondary process. But
32:16 creating the cement profile that you see is a pack is bladed creating into
32:21 equal mosaic. But again, these never get bigger than a few 100
32:27 at the most. Okay, everybody what I'm saying. So most of
32:32 alteration occurs below the water table in fresh water for attic because of the
32:37 residence time and fresh water. So are all younger samples. Because obviously
32:43 can we can we can study these at earth's surface conditions or near the
32:49 surface and see what's going on here an ancient analog Again, this is
32:53 Jurassic smack over sequence that occurs on northern side of the ancestral gulf of
33:01 smack over is famous as a carbonate play type that will obviously talk about
33:08 . But I want you to appreciate genetically that we see patterns of dissolution
33:15 . They're identical to what I just you from these younger carbonates.
33:20 you see the US getting selectively dissolved . Again, referred to be a
33:25 genetic and then that becomes the source the pore filling cement and the cement
33:31 off with an ice, a pakis bladed clear white attribute or characteristic
33:41 has plated morphology grading into slightly coarser dimensional mosaic toward the centers of
33:47 So on this basis historically, everybody this to be a byproduct of freshwater
33:53 dia genesis. Okay, so we're comparative sediment ology again, right?
34:00 on relationships. We see in these carbonates. Understand this example here from
34:05 Jurassic and then santa axial cements look this in thin section there they only
34:14 around a kind of germ or Quran pieces. Here's an example from the
34:20 and this is a piece of a oid. And you see the cement
34:23 goes around it and you can prove is a taxi or by going to
34:28 Nichols and rotating the stage. And see the overgrowth cement goes black at
34:33 same time, the host brain goes . That means they precipitate optical
34:38 which is the definition of syntax, , overgrowth cement. Okay. And
34:46 can see a problem here in the record, right? For those geological
34:51 periods where there were lots of Quran and probably the famous sequence would be
34:57 Mississippian, where we had tons of oid all all over the world.
35:02 these carbonates successions. And you don't a lot of good reservoir quality in
35:06 , in these lime stones because of reason. Right here, they tend
35:10 cement up relatively early and lose their quality. Right? Because of the
35:16 , the liver gross event. Alright I we talked a little bit about
35:22 crystallization. I said it's a multiple of one mineral type to another.
35:29 Knight. Excuse me, cal side it is a textural change where you
35:38 from one fabric to another without wholesale . And so in the rock
35:45 we're always faced with situations like this you see this safari calcite sort of
35:52 dimensional calcified fabric. And the question is is this pore filling cement or
35:58 this a replacement of some precursor And if it's the latter, obviously
36:04 like to know what it replaced? , just like you'd like to know
36:06 dolomite replaced in the light and the . So how do you get a
36:12 on that? So there's a couple to try to do this. This
36:16 example is a younger pleistocene rock. This is an era genetic mollusk,
36:23 of a conch shell. And you see that adjacent to it. Is
36:29 low back calcite fabric. And the question is, do we dissolve
36:35 the shell to create a big hole then we filled it back in?
36:39 is this more of a more formal of one mineral by another? And
36:45 answer is, see the growth ridges the shell. Are they preserved into
36:52 calcite? If you dissolve this you would not preserve those growth
36:57 Right? So this is fine scale crystallization that preserves some of that
37:03 all fabric multiple replacement are agonized by by that crystal structure to this crystal
37:12 . That's re crystallization. Everybody appreciate I'm saying. This is what we
37:16 by re crystallization. Usually doesn't play role in risk for quality development.
37:21 it obviously can alter the texture or mineralogy of the of the sediments of
37:28 . Here's another example the thin section some well cuttings from a Jurassic age
37:36 that was drilled in the english Alright. And what you see here
37:43 some nick, right? And you one scalable particle here, that's a
37:47 multi chamber benthic foraminifera, That's what yellow arrow points to. And then
37:52 speak see all the secret dimensional light calcium material. That's what the red
37:57 are pointing to in this photograph. so the question here again is what's
38:04 origin of that sparky calcite? Spar just means of course it means
38:11 calcite. Alright. So what's what's origin of that? Is that a
38:15 filling cement? Or did it replace some sort of some of the fabric
38:20 that limestone? And if so you , what was it? Because right
38:24 it's hard to understand the deposition You know, you're probably relatively low
38:29 because you've got enough nick right but you don't see a lot of
38:33 material to see that one grain. photograph is taken with the blue fluorescent
38:40 microscopy technique that we talked about Okay, so in this view,
38:47 yellow arrow, it's going to be to the same grain as in this
38:53 . Alright. There's a benthic foraminifera look what we pick up here.
39:02 you can actually see the coating still around some of these grains.
39:08 this is the beauty of the This technique. When it works,
39:11 picks up Israeli grains. Alright. don't think you see any of those
39:15 in this view here. Right. you do let me know because I
39:19 found them yet. Yeah. And here's here's the fluorescent view. So
39:26 , this this shows you that the people probably would expect it that that
39:32 calcite was just reacting with the Right? But in fact, it
39:36 the U. S. And Lloyd's. Okay. And then look
39:39 this changes your whole story here. really had no clue about your deposition
39:45 . Now, you know, you're somewhere a new social system,
39:50 Because ooh, it's didn't form They formed somewhere nearby, you
39:54 Was that 100 m away? Was a couple of kilometers away? We
39:58 know. But at least, you , you're in the neighborhood of a
40:01 sand body system. And so you start thinking about that you're prospecting in
40:06 area. Okay, So, that's we try to always look through the
40:11 effects of some of these diabetic fabrics sometimes you're wildly wildly surprised by what
40:18 see with this with this tech All right. And again, the
40:22 paper technique can sometimes achieve the same of fabric that you see here.
40:29 . All right. So, let's summarize what I've just said here.
40:33 right, we have a situation of water system where we get exposure to
40:41 water and relatively rainy climate vato zone the water table for added zone below
40:46 . Very little alteration in the vato . Unless we add a lot of
40:51 to the system At 50,000 years of , that might make a difference.
40:57 historically most of the modification occurs in free arctic zone, greater degree of
41:03 selective dissolution, more cement, more prostate prayer, modification. Can
41:09 soffit leads to complete processing version. you're lucky to hold on to that
41:15 that you started with usually decrease it some degree. And what always happens
41:19 permeability, it has to go down you're plugging the inter particle pores that
41:25 the good permeability with cement. Which is ironic because the old literature
41:31 you want to find good reservoir Go find areas that were exposed to
41:35 water. That's the old mindset, ? All you've got to do is
41:39 porosity. Secondary process. You find quality. Well, not if you
41:44 have any permeability, Right? And the problem with this freshwater system is
41:48 it goes too far, you choke all that good permeability. Okay,
41:58 give you a feel for how quick dissolution is and how far the dissolved
42:03 doesn't travel before. Re precipitates. a photograph of a dredge pile of
42:10 , sand on Luther island. So showed you yesterday that that google photograph
42:19 the Luther to the island that I for my thesis. All right.
42:26 This is this is what it looked in 1980. Alright, this is
42:31 , this is about eight years after local, Sorry, that's the
42:40 This is a lucha island. So this is uh Luther is
42:48 Most of the bombers have resorts, ? And this is a resort area
42:53 they needed sand to replenish their They needed sand for their golf
42:59 sand traps and things like that. , they went offshore a couple of
43:04 and they dredged a modern day and pumped it up on the land.
43:09 right. So, we know when took it out of marine water and
43:12 it to freshwater, 1972. When they were building the resort and
43:18 I took this photograph in 1980 when uh teaching a seminar on this
43:27 Okay. And this is what you , the whole top of this analytics
43:32 body system is completely cemented. It's rock hard Case hardened substrate.
43:40 And then you go down about 10 20 cm below that surface. The
43:44 of this fabric is completely un So this tells you when rainwater hits
43:50 magnetic goods, they react very they start dissolving the stuff goes into
43:55 , but that's a travel more than or 20 cm before it re precipitates
44:00 give you that hard substrate and then it. Right. Fresh water doesn't
44:07 it basically you seal off the top this and there's hardly any dye genesis
44:12 in this stuff below it. So that tells you how quickly this
44:17 gets gets dissolved and cemented when several . Okay. It tells you that
44:24 stuff doesn't travel very far in solution recharges and re precipitates. Okay,
44:32 I'll post some papers on blackboard or them to you a female to relate
44:38 some of the stuff we're talking about . So you can you can get
44:41 better feel for some of the stuff the road. So, appreciate the
44:47 here. Right. How quickly these cement up? All right, But
44:51 is a pile of quartz sand. would be a pile of court stand
44:56 unscented, Right. Because there's nothing react with fresh water. Okay,
45:01 the difference between carbonates and plastics. let's take that relationship to the world
45:08 sequence photography. Right. And and way carbonate systems respond to changes in
45:13 level. So, most of you familiar with the classics model.
45:19 Where you have a so called which is a horrible term? And
45:24 . Try not to use that but basically a shallow water platform dropping
45:29 into deeper water. Alright. And high stands, where where do you
45:35 do you tend to pond your course plastics back up here. Right.
45:40 it's very difficult to push that stuff during a high stand. Okay.
45:45 people would say during low stands, when you bring out your coarse grain
45:49 as turbine sites or wind blown deposits the basin. Okay. To create
45:54 sandstone play out here. All And unfortunately, if you look at
46:02 sequence strata, graphic model for And then you look at their model
46:07 carbonates, it's identical. They treat systems re finding like this because they
46:14 determined to come up with a model could be applied equally to both carbonates
46:18 plastics. And they refused to accept fact that the systems respond differently.
46:25 deposition aly and die genetically. And we'll get into this discussion
46:30 Okay. I mean, I know because I was all that I was
46:34 when all this happened At Exxon. right. This is all during the
46:38 80s. So, I sort of stuck in the middle between the sequence
46:42 coming out from the seismic and then coming at it from the rock based
46:48 . And of course, I I know if it's by accident or
46:52 I probably wanted to do this, I came at it also from the
46:56 genetic standpoint. Right? Because like said, that's the way you test
47:01 every exposure surfaces due to see whether sequence boundaries due to exposure or
47:07 You prove that by looking at the underneath the exposure surface. Right.
47:12 so there are problems with that. see this come out in our discussion
47:15 on. Okay, The carbonate system 180° out of phase with the classic
47:22 . Okay. It's during high stands you're carbonate platform is flooded, your
47:28 machines going full blast producing a lot sediment rights being broken up by major
47:34 activity. That's when you shed material the basin. Okay, it's Hiestand
47:40 . Not low stand shedding. Hiestand . Okay. And what happens when
47:45 drop sea level on a carbonate First thing that happens is those poor
47:50 die, right? You take them of water. They die, you
47:53 your carbonate production. And then what ? What I just showed you with
47:58 previous photograph, right stuff starts to up, right? And then water
48:04 to go this way, right? wants to go into that carbonate,
48:08 ? And create aquifers and things like . So there's not a good way
48:12 shed a lot of material during the stands. They don't stuff doesn't magically
48:17 off, which is what the Exxon photographers wanted to argue right, That
48:22 could just blow it all out into base and bring it out by flu
48:26 deposition. No, the water goes way, right, and the stuff
48:31 anyway, so you can't blow it the adjacent basin. So, I'm
48:35 to prove this timing relationship to you weekend and show you there have been
48:40 case studies done now around the world the holocene and Pleistocene to prove the
48:45 of Hiestand shedding. That's the norm carbonates. Low stand shedding is the
48:50 for classics, but it's not unequivocal . Okay, my son lives in
48:58 Diego. All right. And every we go to san Diego, we
49:03 to the beach and I can, can look off and see La Hoya
49:08 all right. And the canyon is . And it's shutting classics today during
49:13 high stand, right, stuff is coming into the deep water basin during
49:17 stand. So even a classic you can shed classics from shallow to
49:22 , even during a high stand. , but I would agree this is
49:25 norm for classics, but this is norm for carpets. Okay. And
49:31 , I'll continue to prove this to as we go along. But
49:34 but this is one of the major in the carbonate community that was essentially
49:39 by exile publishing their sequence data, model and treating carbonates behaving the same
49:46 as classics. So completely different approach two trying to answer the question right
49:55 , Coming at it from the seismic straddle geometries. Right. And they
50:01 worked for a guy named Pete You heard of Pete veil? The
50:07 of the Pete Bell was the chief at Exxon. And he got a
50:12 of notoriety because he pushed the sea concept as a driver for sedimentation.
50:18 . And uh, he worked his career at Exxon. He was determined
50:24 prove that sea level was a major for both carbonates and plastics. And
50:29 actually taught him within Exon. He through one of my five day courses
50:35 Exxon and he came out, he , Jeff, that's really interesting.
50:37 I see no differences between carbonates and . I mean if you can't see
50:45 difference is that you don't want to the differences. And so I could
50:49 convince him. And then he went Rice University where I was an adjunct
50:54 and, and I can never convince there either. So I just gave
50:59 . Some people are just, they've up their mind. This is the
51:02 it is and every sequence is like . There's not much you can do
51:07 people like that. All right. right. Why don't we, why
51:14 we take a short break here? , we can take our 15 minute
51:19 here and then we'll come back and talk about uh, a variation on
51:23 theme for the marine for attic and we'll finish up with the barrel Dia
51:27 . Okay, so let's start back at the quarter till two.
51:33 online guys and gals. Okay, going to continue our discussion and carbonate
51:43 Dia genesis. And I'm going to throw a wrench in this whole discussion
51:49 introducing you to this concept of what call marine barrel die genesis. This
51:54 a relatively new phenomenon that was documented in the late 19 nineties by a
52:02 out of the University of Miami. uh, it's a phenomena that I
52:08 people suspected for a long time. fact, I actually address this issue
52:13 my dissertation uh, well before then I was delighted to see this work
52:19 get published. And basically what the is here is that there's another way
52:25 make secondary porosity early before the onset pressure solution that has nothing to do
52:32 fresh water. So the concept is barrel die genesis. So we come
52:38 to the marine free attic environment and I've drawn the blue line here from
52:44 of meters down to less than 1000 is an area where you get dissolution
52:52 or a genetic material during shallow Alright, nobody fully understands what's driving
52:59 , but we observe it. And the geochemistry that's been done on
53:04 , the coexisting calcite cement proves that is not part of the story.
53:10 something's happening during shallow burial that causes arrogant night to start to dissolve
53:15 And what's interesting is it ends up fabric that looks identical to what I
53:20 showed you for the freshwater free attic genetic environment. Okay, so you
53:26 to be familiar with this relationship So we're talking hundreds of meters of
53:32 before the onset of pressure solution. dissolution segmentation is all related to marine
53:40 . The only thing that dissolves is rag a night. Okay. But
53:44 I said, fabrics are almost identical what I showed you for the freshwater
53:49 attic die genetic environment. Okay, these are some of the ideas that
53:55 in the literature about what causes what causes the dissolution. You
54:01 we know that our agonizes as it warmer and warmer. There's a temperature
54:06 on the conversion of arrogance. The . Anyway, it's the temperature increases
54:11 wants to start converting to a more form of calcite. So it may
54:15 just something simple like that or maybe that involves, you know, sulfate
54:21 bacterial oxidation of the, of the . But irrespective, let me show
54:27 the case study the case studies based seismic lines that were drilled in the
54:32 19 eighties off this part of the Bahamas. This is called Great bahama
54:38 city of Miami's right here. And this is one of the seismic
54:44 that piqued the interest of a group of the University of Miami and they
54:50 a million dollars and research money and brought a drilling barge over here.
54:55 , you're up on the platform. it's very shallow, less than 10
54:58 of water depth. And they drill two continuous cord wells, Klin.
55:03 and Linda. And you can see drill down to those depths.
55:09 And the first thing they did encounter any of these carbonates is pressure
55:13 So a couple 1000 ft is not enough for pressure solution yet.
55:19 And you know they were interested in what the these off flapping client forms
55:26 , what they represented deposition early. , they mostly represent fine grained carbonate
55:30 pushed off but some of the debris coarser grain that is pushed off by
55:36 hurricane activity. And when they looked those coarser grain fabrics in the
55:42 they saw this, they saw fabric dissolution where the magnetic material dissolved
55:49 That generated the pre compaction packets, calcite cement, Sometimes those cement graded
55:56 an equal mosaic. Okay, so lot of variability in terms of dissolution
56:01 ation. But when they analyzed these cements with the isotopes with trace
56:07 they could not prove that fresh water a role here. All the signatures
56:11 marine. Okay, so appreciate the of this. This is pre compaction
56:19 . Uh Okay. And it has to do with with fresh water.
56:24 , so this is the second way make secondary processing and carbonate. And
56:28 think you know this is important to about the application here because there are
56:34 in the world like the permian and texas, right? We have the
56:39 and midland basins that are surrounded by water carbonate platform systems and there's evidence
56:46 shedding of shallow water material like these brain stones into the deeper water parts
56:53 these basins. In other words, stuff gets a case of deepwater shale
56:58 for years people have documented this kind ferocity evolution. And again,
57:03 how would people interpret this fabric? see fabric selective dissolution, pre compaction
57:09 a pack, a cement grading into equip mosaic. Always people would interpret
57:15 to be fresh water die genesis, ? Based on what I showed you
57:20 the modern Pleistocene, but that never any sense. Right? You're out
57:25 the middle of the basin, you're the world of non cal Correa's
57:29 How would you ever get fresh water into that basin? All right.
57:35 mean, you would, I mean just the fact that you would really
57:39 to drop sea level. Right? would also have to get that fresh
57:43 through the shale. Alright, so never made any sense. And
57:48 what makes sense is the marine barrel genesis story, right? You throw
57:53 arrogant and material out into deeper Okay, And then you bury it
58:01 recognize is gonna start to dissolve to the multi porosity. You're gonna generate
58:04 pre compaction cements the samples from 50 ft of barrel, that's enough for
58:10 solution, but you don't see any terrain, you don't see any collapse
58:13 the ferocity. Okay, so this where I think you think about the
58:18 of of this process to generating secondary . Okay, so you have to
58:25 really careful here because the literature, old literature is built around secondary porosity
58:31 freshwater. If I find secondary then I assume it's been due to
58:37 to fresh water. Well, here's second way to make it has nothing
58:41 do with fresh water. And I'm show you a third way in the
58:45 setting where you can make this porosity exposure to freshwater. So, secondary
58:52 by itself is not enough to say got some aerial exposure just like a
58:56 is not enough to say I've got I've got exposure to freshwater.
59:02 everybody appreciate that. So that's sort a variation on a theme here.
59:08 let me finish up here by getting to appreciate the role of climate and
59:12 of this. All right, coming to the freshwater die genetic story.
59:18 there's a a P. G. conference held back in the mid early
59:24 . Okay. And they were interested talking about porosity, development and nonconformity
59:30 . And part of that conference, of that discussion at the conference was
59:37 for reevaluating some of the controls on dia genesis and this is a ranking
59:43 the different controls. So the key is climate, obviously you've got to
59:48 in a more humid rainy climate to a lot of fresh water die genesis
59:53 then what's the second key controlled length exposure, that sort of holds everything
59:58 . Okay. And so I want to appreciate the role of climate and
60:02 quickly climatic belts can change geographically, I don't think people really realize that
60:09 I'm gonna do that by bringing you to the bahama platform complex.
60:16 there's Miami city of florida. I showed you the seismic line data from
60:20 here. This is what we call northern Bahamas. Okay, this is
60:25 area that's been historically studied going back the 30s. And then this is
60:30 platform that we did start to study until the late 80s, early
60:37 All right. And appreciate that this of the world here is humid climate
60:46 amounts of rainfall, 8200 and 20 of rainfall a year. And Novak
60:52 associated with this. And then keiko's is a sub arid climate, Just
60:59 know, 2030 cm of rainfall a , evaporates associated with the carbonates.
61:06 , on this platform, this is famous area for mining salt back in
61:11 back in the 15 16, 17 . Okay, salt for europe salt
61:17 the fledgling us. Right, I'm gonna contrast to places seen lime
61:24 , one from a Lutheran to up where I just talked about the dredge
61:31 . All right. And both of are the same age carbon-age sequences.
61:35 basically under 20,000 year old sequences. were exposed severely 100,000 years ago by
61:43 major drop in sea level, as as the ice sheets developed. Right
61:50 spread, they tied up all the . Right? So they dropped sea
61:55 regionally and sea level came up when ice sheets melted, but they never
61:59 up to the level of these So these outcrops are still exposed obviously
62:05 over 100,000 years. Okay, so evaluate the die genesis. The difference
62:11 die genesis. All right, so northern zone, which today is a
62:15 climate, The rocks look like I've already showed you the picture.
62:19 is that pleistocene limestone, 100,000 years vito's die genesis complete cross the
62:26 not an ounce of arrogant left in rock. All the all the permeability
62:30 off by that segmentation. Okay, the northern northern Bahamas. Okay,
62:37 me take you down to keiko's Same rock, same level above present day
62:42 level. Look at these grains are preserved 90% of this rock is still
62:47 rag genetic. Where's all the You really have to look hard to
62:51 any. All right. A little of dissolution. A little bit of
62:56 . Okay, primary porosity system See the difference today. This is
63:02 cemetery climate. I think you have conclude that even back in the
63:06 it was a similar climate. With less fresh water, more fresh
63:10 in the north. So, just back to that map, I mean
63:17 that's a distance of From here to . That's about 400 miles as the
63:23 flies to the south southeast. that's how quickly you're changing climatic
63:30 You're also changing. You're also going a tropical belt. This is the
63:34 reaches of the tropics to into the belt. And you're also changing trade
63:40 belts. This is a strong easterly wind belt and this is a weaker
63:45 easterly trade wind belt up in the . Okay. And probably all these
63:49 are entwined together. But appreciate how these things change in terms of their
63:55 of die genesis. Okay, that's climatic effect on freshwater. Dia
64:07 Alright, any any questions before we on to our last deep burial die
64:12 environment. All right. So, see in pink on this diagram,
64:19 so called deep aerial die genetic environment this is the I'll tell you a
64:27 here. I went to a research in Oklahoma city when I worked for
64:32 and conferences on deep barrel die Alright, so what they posted a
64:39 outside the outside the room where there's deep conference on deep barrel Dia
64:44 And I remember this old older lady up to me and said, is
64:48 a is this a meeting of He said no, this has nothing
64:56 do with barrel of bodies or anything that. Yeah, I got a
65:05 out of that. But anyway the , you notice all these diagrams have
65:09 squiggly line between these near surface digest and where the deep barrel starts.
65:15 the controversy has always been how deep have to be to initiate the barrel
65:20 genesis and I guess really what is barrel die genesis? Well I think
65:26 of us in the carbon a community would define this as die genesis coincident
65:31 or post stating the initial pressure solution that sequence. Okay. When do
65:38 start the style lights? When do start the grain to grain? Okay
65:43 I think we can agree on that . What we can agree is on
65:47 deep you have to be because I'm I'm gonna talk about this in in
65:52 minute but but that's a big Okay so I told you this is
65:59 least understood of the dia genic environments of the access to proper databases but
66:06 me share with you our best understanding going on again. Most of this
66:10 come out of Western Canada because of access to core databases. But obviously
66:16 a deep barrel digest environment we're dealing higher temperatures and pressures. So the
66:21 here by this time it's gonna be dissolution of calcite IQ material.
66:28 All the reaganite by this time it's be stabilized to a more stable form
66:33 calcium carbonate. It's either gonna be out or it's going to re precipitate
66:38 stable calcite cement. Right? That's gonna be because of freshwater die genesis
66:43 because of marine burial die genesis. as I said before, what's linked
66:51 pressure solution is sanitation. Now the are a little bit different. There's
66:59 inclusion free, clear, whitish and light. But now there of course
67:04 crystalline. Then I showed you for freshwater or marine burial. Now there
67:09 hundreds of microns to millimeters scale If they have the space to grow
67:14 that size, they're still echo dimensional there's still a magical sight.
67:20 so that's what dominates the deep barrel environment. But if you get the
67:26 kind of introduction of fluids, you do what you can create a third
67:31 to make secondary porosity. And the there is barrel dissolution where you can
67:38 petra graphically or geo chemically that that dissolved after the start of pressure
67:45 Okay, that's all it means, , that could be, you
67:49 1000 m. So that could be m whenever those fluids came in.
67:55 , so the key control obviously is of burial for carbonates are never deeply
68:00 . We don't worry about burial die very much. But most of our
68:04 is going deeper and deeper and Alright, so it becomes an
68:09 So think about the relationships here. ? I told you when we started
68:15 discussion, I talked about the process evolution, right, burial. Dia
68:20 tends to destroy ferocity with progressive And so the question is how do
68:27 preserve it? Well, these are two ways to preserve porosity long enough
68:32 entrap hydrocarbons. So that would be compaction, marine cements, pre
68:37 freshwater cements, re compaction, marine die genesis cement. Okay. Otherwise
68:44 left to something like over pressuring or pressuring. Okay. And we'll talk
68:50 this when we get to the play a couple of weekends down the road
68:55 . But if you can create a where you're poor pressure is higher than
68:59 overburden stress, then you stop pressure . Okay. And a lot of
69:04 big talk north north north sea fields off of Norway are over pressure.
69:13 why they have such high porosity ease though they're more deeply buried. All
69:18 now, if you want to create secondary process at depth, then you've
69:22 to come up with a mechanism where can generate acid fluids that pass through
69:27 rocks after they've been more deeply But while they still have permeability and
69:32 of this may tie back to the of the hydrocarbons and the cracking off
69:36 different gas species that we talked So if you don't know anything about
69:41 barrel history of the rocks, you're , you know, looking at outcrop
69:46 example, right. You don't know barrel history. Then you want to
69:50 look for expressions of pressure solution, you know that these rocks were buried
69:53 some degree to to create that pressure . So these are the fabrics,
69:59 would look for skylights, brain to surgery, whiskey micro style lights.
70:05 , the controversy is how deep you to be to initiate pressure solution.
70:11 . So you can go, you go cherry pick the literature and you
70:15 find papers where people talk about skylights under tens of meters of burial And
70:22 are they talking about? They're talking an outcrop that they're studying,
70:26 And they've gone to the top of outcrop and they worked their way down
70:30 10 m down they see a style , see only took 10 m of
70:36 and then you ask them, what was on top, I don't
70:41 , well maybe there was a mile ice sheet on top and it
70:47 okay. Or maybe there was a overburden that got stripped off. They
70:52 know. Okay, that's the problem the crop studies. Nobody knows precisely
70:57 barrel history And so believe it or , there's still only one case study
71:04 that proves the timing of pressure And it's this case study here that
71:09 published back in the early 90s, is from the ocean drilling project.
71:14 . The old deep sea drilling project they this is from the western part
71:21 the pacific ocean and they were they looking at these younger tertiary age
71:28 Okay. And if you know anything the deep sea drilling project, you
71:32 that they core from the sea floor to their target, right? They
71:38 continuously. Okay, then they pull core up and the first thing they
71:44 is a sub sample decor for bio graffiti. They want to know the
71:49 , They want to know gaps in of time. Right? Missing
71:55 Okay, so for this example no missing section, complete sedimentary
72:01 Okay, so no breaks in deposition idle. Ent what did she
72:08 She documented uh maybe some pressure solution 800 m below the sea floor.
72:17 . And I say maybe because even wasn't convinced that these were pressure
72:22 Seems she describes and photographs these It's very big. Wispy like
72:27 Right? So it's not clear. didn't document whether stuff was being dissolved
72:31 that seam or not. So it's clear whether that's a physical compaction effect
72:35 not. But look where the style kick in that have any amplitude.
72:41 , mostly below. About 1000 That's where you get the good well
72:46 style lights. So, I'll give 800 m. Okay, I'll give
72:50 that number 802,000 m. Okay, not gonna give you tens of meters
72:56 burial until somebody can show you can that. Okay, so when I
73:01 about barrel die genesis, this is of for me I get tired of
73:06 802,000 m. I just rounded up 1000 m or so. Okay,
73:12 to me that's what defines the initiation for burial Dia genesis. All
73:18 Where you have the potential to start pressure solution. Right. And I
73:23 I may or may not have told this yesterday, but I, when
73:27 was a grad student at rice, worked the austin chalk here in texas
73:31 Mexico did a regional study and so got into the chalk literature for my
73:36 work and I came across the paper by a german who interestingly modeled pressure
73:43 is starting over 1000 m based on northwest european chalk deposits. So it's
73:50 that the numbers matched over a 20-year . Right? He published those numbers
73:55 basically she's saying about the same Okay, so don't assume pressure
74:02 A one shot deal. Alright, going to continue with burial as long
74:06 you can move fluid away from the of the grain to grain suture
74:11 Okay, so again, if you know anything about burial history, as
74:17 showed you this morning, we looked skylights and the grainier limestone fabrics.
74:22 mentioned the offset again, minimum amount pressure solution, minimum amount of carbonate
74:28 along that seam. Okay, most lights line up bed parallel because your
74:37 stress direction is like this, Your sigma one is like this.
74:41 your style light lines up like this that. You can have tectonic style
74:47 in full belts. Right? Where fold your rock like this and you
74:52 in from the side that can create solution this way. Right. Press
74:57 principal stress direction comes in from the . Okay. And then what
75:04 Where else can you do this? a branch of strikes the fault
75:08 Right lateral compressive stress can also create style lights. So tectonic style lights
75:14 vertical. Okay, and what would fractures be in a tectonic? They
75:23 horizontal. Right? Most most burial are vertical. Right? Because the
75:29 stress direction is top down from the setting. The fractures are horizontal for
75:35 cross cutting. Like this. well, I've learned to pay attention
75:41 the some of these tectonic fabrics because tell you locally what's going on.
75:46 that might have an effect on the genesis of these carbonates. And then
75:51 other expression ingrain stones is the grain suturing that I alluded to earlier.
75:55 then in the mormon critic lime whiskey micro style lights are the are
76:02 expression I told you they don't get by the borough structures. They actually
76:08 into style lights with relief. So establishes the genetic relationship. And in
76:15 , you see removal of part of borough along the swarm of whiskey Micro
76:21 lights or you see the micro style go right through the burrow. These
76:25 not early pre compaction, clay like I told you some of my
76:30 , people colleagues think is the right? That's how they interpreted a
76:35 rock. This is pressure solution. is again, you can't quantify how
76:41 material has been lost. Okay, what's happening if it seems as you're
76:46 calcium carbonate? Now? The question , where does it go?
76:52 donor receptor dia genesis. It doesn't very far from the style light.
76:58 , so if you you start off the limestone that has porosity, you
77:02 it and you you kick off a lights in this position right here.
77:07 at the distribution of the cement relative that style light. The black and
77:11 represent the calcite cements, the blue porosity. Look at this relationship here
77:18 the porosity is tight against the skylight the cement decreases away from the style
77:25 on both sides. That argues again local donor receptor die genesis,
77:30 That tells you your locally sourcing those smiths. And so that's the important
77:37 to take away from from uh this . Okay, and actually this creates
77:44 barriers to vertical flow. Alright, of the giant oil fields in abu
77:50 for example, in the Middle East own not by classical Stratan graffiti,
77:55 owned by these through going stylings, run miles across these reservoirs and their
78:01 vertical permeability barrier. Okay, because the segmentation effect, this is what
78:07 expect to see when the process is first before you bury it. Okay
78:13 start the pressure solution. So let's up by talking about the nature of
78:19 cement. Alright. And how we figure out the relative timing. So
78:25 we typically see is again all the arlo mag calcite and they tend to
78:30 equal dimensional cement. They tend to relatively coarser crystal and compared to what
78:36 showed you for the freshwater and marine attic. And so some of these
78:41 what we call inter particle cements where precipitate between the suture grains but they
78:48 occurred between the future grain contacts. the timing indicator, right? That
78:53 you they formed after the grains were sutured. That's what we look for
78:59 the rock record. Pet geographically, course we can verify this with the
79:04 or we look for something like this we have a bunch of grains encompassed
79:09 one big calcite crystal but the grains sutured. The only way for this
79:14 happen is for the sedimentation to occur the grains were sutured because if the
79:21 were not sutured and then they got that fabric would be frozen in
79:25 right? There would be no way suture those grains together. Alright.
79:29 are called politic cements and then you get syntactical cement again in the burial
79:37 and a lot of people actually think point politic is this where somewhere outside
79:43 plane of the rockets growing off a Oid and going out and capturing those
79:49 but doing it after they've already been to explain the pressure solution and then
79:56 the cement are not very big because poor, space is not very
80:00 Some people get hung up on the sides here, you know, they
80:04 the small crystal, they want to that an earlier phase of segmentation.
80:09 there's just no space to grow big like you could do here or here
80:13 here. Okay, so crystal size not a definitive by itself? Crystal
80:19 doesn't really mean anything, you have be really careful about that. I
80:23 you can still be in a burial have tiny crystals because you don't have
80:28 space to grow the bigger crystal Alright, so let's just look at
80:34 couple examples here and we'll stick with very simple analytic grain stone fabric.
80:40 is the Jurassic smack over again from northern gulf rim and you see the
80:46 is you see the blue porosity which primary process. You see the calcite
80:51 . Again, our question is, is the timing of the segmentation?
80:58 , so what else do you see these rocks that you can relate die
81:04 to see that. See that see grain suture together? Green suturing.
81:20 . Gotta account for that. Okay let's we we talked about all the
81:26 for making cement. Right? Marine water, marine burial D.
81:35 So why is this not marine Maurice . S. Were cloudy colored.
81:46 packers are bladed. Okay and that's the distribution here. And why are
81:54 not freshwater cow side, armory cow sides? What did you need
82:00 source them? The cement you needed dissolve the grains. Right. Are
82:07 grains dissolved? Are there holes in middle of the grains like we saw
82:11 ? No there's no multi ferocity. what are you left with burial?
82:18 look at these cement? They're always away from the future context.
82:22 So these are those coarser inter particle cement? They come in after you've
82:26 started the future the grains. The implication is that this is the
82:32 carbonate the suture grain contacts is the for for this cement. Okay.
82:40 not for all of it. It come in from somewhere else but certainly
82:43 initial phase would be related to Okay so you see how we're trying
82:48 get a handle on the timing. want to know? It's not a
82:54 department not marine cement. The S. Are marine, right?
82:59 were deposited marine setting but there's no sedimentation because there's no ice. A
83:04 of cement around the you is that fibrous or bladed? Right? The
83:13 we got in the grain stone. . And then there's no cement between
83:18 grains. So there's no early pre cement and then there's no dissolution of
83:25 that would source that early pre compaction . So that eliminates fresh water.
83:30 eliminates marine burial dissolution. So what you left with burial? Okay.
83:39 the fact that these cement don't occur the grains is consistent with that segmentation
83:44 after the grain to grain suturing. . And then related to this would
83:52 the those larger so called apocalyptic cements one large calcite crystal which shows unit
84:00 under cross Nichols encompasses a bunch of , but those grains are sutured
84:05 Okay, that's the timing indicator. this is another expression of burial calcite
84:15 . Alright, so let's let's finish this discussion here. The I think
84:20 can appreciate the norm here when we with any porosity, we inherent from
84:25 near surface setting. Whether it's just primary process off the sea floor or
84:30 prostate modified by early freshwater or marine . Dia genesis what's going to happen
84:36 that ferocity during barrel, it's going be occluded variably by pressure solution and
84:43 cement station. All right, so what everybody used to think was the
84:48 we modified ferocity during burial because nobody about burial dissolution. And so the
84:55 were well, let's inhibit pressure solution sanitation long enough to entrap the
85:01 And how are you going to do ? We're going to do it by
85:03 sanitation, marine freshwater, marine Right? Potentially. Those are the
85:10 mechanisms. If you don't have then you have to rely on
85:14 you have to rely on over pressuring geo, pressuring again before the onset
85:21 deep enough burial in order to create pore pressure that resists pressure solution.
85:28 maybe you believe the hydrocarbons in early , they migrate up dip and displaced
85:35 of the water. If you displace of the water, you basically shut
85:39 your die genesis machine because you need and you know, this makes sense
85:48 . I don't think anybody's ever documented yet. All right, but it
85:52 makes sense that you could be one to preserve ferocity of death. Okay
85:58 the question becomes, can you generate barrel secondary porosity? Obviously the answer
86:03 that is yes. And how do do that? You do it by
86:08 either acidic fluids during the cracking of hydrocarbons. The normal maturation effect that
86:15 see with progressive burial as you go oil to gas or you can do
86:20 by this mechanism called thermo chemical sulfate . This is a sort of unique
86:27 reaction that's associated with bases that are with evaporates. So the sulfate is
86:34 also fake coming up from underlying deep evaporates or it's coming from local cannibalization
86:41 evaporates in that carbonate succession. And is that sulfate reacting with this reacting
86:47 organic material and the carbonate succession. that reaction creates H two s and
86:53 two S. Then becomes the agent carbon for carbon carbonate dissolution.
87:00 so we'll talk about this in more in the next lecture on demonization.
87:05 but this can apply to lime stones well. So let me just show
87:09 what I'm talking about here. Just some of these relationships here and show
87:13 couple of case studies to illustrate what been talking about. Alright, if
87:19 want to preserve process at depth, you want to generate early pre compaction
87:25 . Has one way to do And here's evidence of this from two
87:29 from an outcrop in uh France. , the paris basin in France is
87:35 hydrocarbon productive basin that produces from Jurassic . And then these carbonates are uplifted
87:42 the periphery of the basin. So french can take you out in the
87:47 and show you these outcrops. And so there are parts of two
87:53 we're late. You're going to call for showing sequences and the first one
87:58 up here into a little grain stone this point right here and then is
88:03 by a relatively rapid rise in sea . You go back into deeper subtitle
88:08 and then the whole system shallows up the high energy cross stratified grain
88:14 which in this case gets sober lane pro predate pro grading, lagoon.
88:19 back back show. Laguna carbonates. , So look at the look at
88:23 distance here, that's five m. , so it's not very far between
88:29 and this. Okay, so you at the look at the lower sequence
88:34 , it never was exposed to any see imitation marine or freshwater or anything
88:41 . Okay, and the upper zone evidence of exposure to fresh water.
88:46 see a soul profile developed here, can see some dissolution of the
88:50 Ids and generation of early pre compaction . Obviously both of these sequences were
88:57 into the realm of pressure solution, how close they are to each other
89:02 the lower zone is riddled with style . Okay, and so look what
89:08 here, You get the style you get the grain grain and you
89:11 the porosity, right? That's the . That's usually what happens when you
89:15 to preserve prostate death. But here ended up a good ferocity because you
89:20 enough pre compaction cement to resist pressure and preserve ferocity. Okay, so
89:27 always been one of the strategies that have thought of to preserve prostate.
89:32 here's a reservoir. Example in the smack over analytic grain stone fabric,
89:38 dissolution generates the secondary porosity. Look the cement, they are pre compaction
89:46 bladed white, clear crystals grading it an equal mosaic toward the centers of
89:53 . Okay, classical early dissolution Right? Everybody historically interpreted this to
90:03 freshwater free attic, but it could be the marine barrel die genesis
90:10 Okay, at least at this scale turns out so regional. Well,
90:17 mean, who knows? I mean thinks because it's such a regional phenomenon
90:21 probably due to freshwater lens system or freshwater land system, but but you
90:27 the point here, right, this is this sample I think is from
90:33 seven or 8000 ft of burial. deep enough for pressure solution. You
90:38 see any grain to grain suturing. don't see collapse of the prosperity that
90:42 cement basically freezes up the fabric and pressure solution. You didn't destroy all
90:48 porosity. So you've got enough permeability that you get a good reservoir.
90:55 . Everybody appreciate the timing relationship, ? It's critical to report to see
91:00 effect right here. Where the cement all the way around the grains except
91:05 they're touching somewhere in that rock. . And remember they don't touch
91:10 Right? Only four points for a . All right, okay, so
91:21 the Jurassic smacker, we have situations this that are perplexing because we see
91:27 see the U. S. And . Lloyds. We see grain to
91:29 suturing, but we have very little . And so people have always wondered
91:34 rock like this isn't a reflection of hydrocarbon migration into the system,
91:41 Where you displace the water and basically down your die genesis machine again makes
91:47 . But you know, proving I think it's really hard to
91:49 All right. So those are all strategies that I said people had,
91:55 had up to the late eighties, nineties. And then we started to
91:59 the barrel secondary process development. And this is a list of criteria
92:06 what you would want to look for graphically and then follow up geo chemically
92:11 prove the timing. And I've highlighted relationships that you see time and time
92:17 in thin section. That would tell this is burial dissolution. So preservation
92:24 secondary process up to and actually cutting pressure solution seems pressure solution seems that
92:32 to float and secondary porosity dissolution of cal city of stable calcified grains.
92:39 , I told you calcite doesn't dissolve freshwater, it's not gonna dissolve in
92:44 marine barrel die genesis. So that's red flag that tells you there's something
92:49 about the flu chemistry. So, me just finish up with a couple
92:53 here and we'll put this into a type discussion later. But this first
93:00 is from the Miocene complex in Southeast . It's called the tuna and it
93:10 It's moderately deeply buried. That's basically platform is the reservoir. Okay,
93:18 it's a 5000 ft thick platform and riddled with ferocity. Alright. And
93:26 gas in place, you can see 46 TCF of methane and 100 and
93:32 TCF of carbon dioxide and it's never put online. Okay. Because there's
93:39 guess there's there's not enough coca cola in Southeast Asia to support the
93:44 02. I don't know. I they're really afraid of this stuff leaking
93:49 . Okay, so there's a ton methane here, but it's never been
93:53 online. Alright, so Exxon, their straddle geometries and sequenced photography interpreted
94:01 whole top of the carbonate platform to sub aerially exposed. And they interpreted
94:05 of this process to be related to dia genesis. Okay, but this
94:11 what the fabric looks like. that's a style life. And here's
94:16 example of a stylized that appears to floating in the blue secondary ferocity.
94:22 makes absolutely no sense. That this early foreign ferocity. Why would you
94:26 a style lights in the middle of poor sound? See the problem and
94:33 what they're looking at here is they realize this. They're looking at one
94:36 here. One grain here, the were sutured together. And then what
94:41 you do? You leached out that ? You reached out that grain to
94:45 that floating fabric. Okay, and what else do you have? Well
94:51 , here's the other part of the . See the style I to see
94:54 parity preserved right up to and on sides of the style lights. What
94:59 we see when proxy was there first saw preferential segmentation around the skylight,
95:05 decreasing away from the style light on sides and here. It's just the
95:12 . See that makes no sense at . That this is early. Foreign
95:16 agreed. If you don't agree. me. And we can argue about
95:20 , but I hope you appreciate what saying because this is critical to the
95:25 . Okay. And you know that was there first you should have preferentially
95:31 this stuff up and you don't see . Okay. And then what else
95:36 you see in the rocks? You leaching of all the stable calcified
95:39 the calcification, oysters are being The kind of turns the red
95:43 the benthic foraminifera. Those are the I told you never leach in fresh
95:49 but in this sequence they're dissolved Okay, so c. 0.
95:53 is probably part of the story All right. Either to generate the
95:57 fluids or they're part of a byproduct that carbonate dissolution. Okay, that's
96:04 dissolution. Here's another example from east right here, the U. It's
96:11 with the blue epoxy uh taking with white paper technique. The DPL you
96:17 never see the blue epoxy and a in section view. Okay. And
96:22 course the earlier published papers on all this in east texas relate this to
96:27 major drop in sea level and they all of this process to be freshwater
96:32 genesis. What's the problem with If you leech the zoo, it's
96:39 you generate early pre compaction cements. are they? They're not there.
96:46 between your grain context. You see between any of those grain context.
96:54 . So that tells you the rock already been buried right? And you're
96:59 to generate the more classical burial calcite before a fluid came in to leach
97:05 the zoo is to create that micro . Okay, and then further argument
97:12 be if that process was there first then you buried, why didn't you
97:17 up the areas along the style You don't see that. Okay,
97:23 is barrel dissolution. We're gonna go this as a case study in a
97:26 of weekends. Okay. And then last example here is a from a
97:33 reservoir in western Canada. Uh The is called jean Marie. It's a
97:39 gas reservoir that produces from these little atop right buildups. And what do
97:45 see in terms of process evolution? see buggy porosity here that cuts the
97:50 lights. Well, that's a simple cutting relationship that tells you that frosty
97:55 during burial right after the skylight. then these little grains here are called
98:00 analysis. We haven't talked about but there are there's some sort of
98:04 dwelling organisms cal citic that grew into of the cavities of this reef.
98:10 and most lime stones, they never dissolved. You never seem dissolved out
98:15 where you see evidence of barrel dissolution you can see their micro leech.
98:20 , so those are the kinds of we look for to prove the
98:23 Petra graphically. If we need to more precise, then we jump to
98:27 geochemistry and try to pin down the timing relationships. Okay, so let's
98:36 what I'm saying here. Right, is critical and making porosity secondary process
98:42 it early formed your surface? That you're you're related. You're relating back
98:48 fluids that are associated with the right? Either marine fluids, purse
98:53 or fresh water. Marine barrel dia for disillusion. But if it's barrel
99:00 , where are the fluids coming Their deep seated sources right there,
99:04 out of the deeper part of the and they're coming out of basement.
99:08 the delivery system is either regional compaction or its local fault related teachers.
99:18 , basement faults providing the conduits for these fluids up. And that's why
99:23 said, you know, if you the timing, then you can start
99:26 maybe exploit some of these relationships, for the burial setting. If you
99:31 there's a structural control on the movement these fluids, right? Then you
99:35 looking along faults and stuff like that good rossi development. Okay, the
99:41 slide here just shows you the some the rules of thumb here, this
99:47 , this is for reinforcing some of stuff we talked about in terms of
99:51 cement morphology, these distributions and uh for the different digestive environments. We
99:58 talked about, okay, any questions comments? We're gonna take a short
100:04 here about check the let me check schedule here before we break 10
100:16 All right, so we'll start back quarter to three and we'll we'll contrast
100:22 limestone dia genesis with the now with demonization effects. Alright, So,
100:27 you're confused with this topic, it even more challenging with the demonization.
100:33 , so we'll take a 10 minute . All right, okay. We're
100:39 to shift gears now and talk about organization. This is the other aspect
100:45 carbonate dia genesis that we have to concerned with because as I said
100:50 about half of our reservoirs at least in north America end up being associated
100:56 dolar stones and they're pretty common around world. So the struggle here is
101:04 try to understand what controls the occurrence distribution of the stolen monetized fabric and
101:10 led to a number of models that been proposed over the years and
101:16 that's part of the issue that we're talk about. And then the other
101:20 of the issue which I think is important to our discussion, at least
101:23 those of you who want to get oil and gas or even something like
101:29 capture, right? Where you're concerned trying to put C. 02 back
101:34 the subsurface. You gotta find porosity do that. Right? Uh You
101:40 to think about reservoir quality development at stones. You need we need some
101:44 about that. So, you know mineral dolomite, It's been around,
101:52 recognized for a long time. A called Dolan, you characterized mineral dolomite
101:58 in the 1700s. Okay. and 200 years later, uh they had
102:05 big research conference in Northern Italy and all places, the Dolomite mountains.
102:13 , so north of Milan and uh from all over the world came to
102:19 research conference. I went to that conference and I came away from that
102:24 conference and thinking that, Jeez over years, we've hardly evolved our knowledge
102:30 dolomite In 200 years. All it's a tough nut to crack.
102:35 I think part of the problem has historically it's a tough nut to crack
102:40 until relatively recently we've never had a to really see through the masking effects
102:46 dehumanization, right? You could never what was being replaced. What was
102:51 timing of the replacement dolomite. You play all kinds of games with
102:56 but geochemistry by itself can be interpreted a lot of different ways and you
103:01 need to constrain that geochemistry with But if you can't see in thin
103:07 the rally grain fabric, then you a hard time constraining the fabric,
103:12 ? And the geochemistry. So let share the way way this is set
103:17 . This discussion is set up. going to make a few comments about
103:20 requirements for making dolomite, which I everybody agrees on. And then we're
103:26 go through the popular models that everybody compelled to apply to their dilemma ties
103:32 of interest, right? Everybody wants try to come up with some understanding
103:37 where the fluid came from, what timing relationship was. And then we're
103:42 finish up with a discussion about generation reservoir quality. What happens to porosity
103:47 permeability with demonization. How can you some of these fabrics? And I
103:53 that's more important to our discussion. again, we don't understand all of
103:57 relationships, especially with respect to property , but they keep recurring over and
104:03 again, that even if we don't and we still should be familiar with
104:08 going on. Okay, so let's this discussion with this diagram here.
104:15 just has three data points. But it shows you, I think is
104:19 is obvious to the rock record. younger carbonates don't have as much dolomite
104:25 older carbonates tend to be more progressively sized, right? And some people
104:31 say, well this is a function changing seawater through time or something like
104:36 . Uh, frankly in my mind that's total bs because the the I
104:43 you can argue that seawater really hasn't at all. In fact, most
104:46 doesn't come directly from seawater anyway, . It comes from a modified seawater
104:52 reacts with some sort of limestone fabric the subsurface. Question is how deeply
104:59 that process occurs. Okay, so , what what you see expressed here
105:04 this curve is a time effect. ? The longer a limestone succession sits
105:10 close to the earth's surface, eventually gonna it's more likely to see a
105:17 is capable of converting it to Alright, so let's talk about the
105:22 dolomite. It's a unique carbonate By definition is a calcium magnesium carbonate
105:31 and by definition it has 50% calcium 50% magnesium. But unlike calcite,
105:40 the magnesium was randomly distributed in the crystal lattice, there's now ordering to
105:46 distribution of the magnesium and calcium. the blue dots represent magnesium, alternating
105:52 of magnesium and calcium separated by the fork like features of carbonate an
106:01 Okay, so there's this beautiful ordering the distribution and perfect composition. That's
106:07 we call ideal stoking metric. You don't need to remember that term
106:12 metric. Uh but what that means if you took a took a real
106:19 mineral, pure dolomite mineral. And the X ray diffraction machine, you
106:23 these incredibly sharp peaks reflecting that perfect and perfect ordering to the cat
106:30 Okay, now here's the problem. early farming dolomite that we see today
106:38 nowhere near this. It's what we proto dolomite. It's poorly ordered calcium
106:45 . It only has 45, Okay, that's the stuff we're making
106:53 . And when you actually look at older lime stones, even in the
106:57 , they never achieve that perfect They're still a little bit poorly
107:02 they're a little bit maybe calcium Okay. And so even the older
107:07 Vice theoretically are still unstable. And that in mind when I when we
107:14 the story here that you know, that are not perfectly stable,
107:18 Have the potential to be altered if see the right kind of fluid
107:22 So um the other controversy is the for for converting limestone to dolomite.
107:34 . If you try to if you to go to the lab today and
107:38 synthetic dolomite, mix up a right? Try to precipitate it at
107:44 centigrade, and one atmosphere of You can't do it lisa geochemist can't
107:50 it. Okay, But if you up the temperature 200°C, you can make
107:56 dolomite in a few months. you can grow those crystals in a
107:59 months. So, clearly temperatures. control Right? Which normally is right
108:05 chemistry, right? You increase the that increases the reaction rate. Uh
108:10 makes sense. Alright, but what make sense is that most people in
108:14 rock record want to make dolomite early their surface conditions where you didn't have
108:20 high temperatures. We can't do it low temperature today in the lab at
108:27 . Like I said that geochemist can't it. There is one organism that
108:31 do it. A Dalmatian dog precipitated kidney stone, proto dolomite. This
108:39 in the literature. Alright. There's paper by Mansfield in the bibliography that
108:44 sent you that documents a dog making kidney stone probably not at 25°. What's
108:52 body temperature of a dog? It's closer to two. I don't know
108:58 it would be in centigrade, but to To what, 90° is it
109:03 our body 90 something degrees? I know. So, the dog was
109:07 to make the kidney stone of proto . But the geochemist can't do it
109:12 the lab without jacking the temperature Okay, so this is this is
109:18 of the problem here. The controversy is it a temperature control and
109:25 Or is it what we call kinetics rate? Right. Is the thermodynamics
109:31 or is it kinetics? That's a debate. All right. Maybe you
109:35 do it at lower temperature if you longer time period to slowly circulate some
109:40 these fluids through these limestone to converted dolomite. Okay, we're gonna go
109:46 and and and talk about this in minute. All right. And then
109:51 me just remind you about the We talked a little bit about this
109:55 . The techniques that we use and to identify minerals. So, you
110:02 , everybody thinks dolomite crystals make little big cubes like this all the
110:08 They actually don't do that all the . Most stolen. My crystals are
110:12 drill or sub federal and shape they a lot like quartz crystals.
110:19 And so we have to do what have to stay in the thin section
110:23 the lizard and red S. But that doesn't guarantee that all of these
110:27 are necessarily, uh, dolomite. have to go to cross Nichols and
110:33 at the buyer infringements. Okay, be careful of that because everybody,
110:40 know, calcite can also make a shaped crystal. So the rabbit shaped
110:44 is not unique to dolomite anyway. most dolomite as I said, is
110:49 and federal or sub federal in shape a lot like quartz. I mis
110:54 that a lot of times in court where I etched the rock. I
111:00 stuff standing up in relief and I , oh, that's dolomite. Then
111:03 get the thin section, this Okay, so you gotta, you
111:07 combine the two together. All And of course everybody thinks the demonization
111:13 the limestone is being a replacement which it is. Okay, But
111:18 organization can also precipitate direct directly into poor system as a cement, both
111:23 lime stones and both in Dulles So we need to talk about what
111:29 the requirements for making dolomite, irrespective what some of the key controls might
111:36 . So obviously if you start with limestone or cal curious sediment, you
111:41 , reaganite, calcite rich sediment, to convert it to dolomite. You
111:47 import magnesium because those carbonate particles don't enough magnesium to cannibalize and directly convert
111:54 dolomite. Okay, but tonight doesn't any magnesium Lomax. House side by
112:02 has 4% or less. I'm a grains vary. So we talked about
112:09 forums, they have 8 to 12% . We talked about red algae,
112:15 have like 12-16%. take that Not the not the red algae
112:24 the Kind of terms have 12 to Magnesium in their skeleton. Okay.
112:33 then the red algae have up to 32-36% magnesium. Alright, but that's
112:40 not enough to get you to that threshold. Okay, so most people
112:46 you've got to import magnesium from Where's that somewhere? It's seawater or
112:52 seawater? I showed you a diagram the end of the first lecture yesterday
112:57 showed you how much magnesium occurs in ? It's a relatively major component in
113:03 . Okay, so all the models going to try to account for where
113:08 where the magnesium comes from. Okay you need an effective hydrological system,
113:15 gotta you've gotta recharge, you can't me from one standing poor volume of
113:20 , You've got to recharge and then need a host rock. Capably be
113:24 baptized, which means that that that had to have had some ferocity when
113:29 fluid and perm when the fluid came . Okay, it's already a limestone
113:35 , it's gonna stay that way. no way you're gonna convert that to
113:38 . Okay, So before I take through the models that try to account
113:43 all of this, let me take back to to when I would surmise
113:49 guys weren't even born. And this 19 this diagrams published in 1975,
113:56 actually they started talking about this relationship in the 1960s, they gave a
114:02 at the focal and gave a talk the late 60s on this relationship bob
114:09 was a famous photographer at the University texas, linton Land was a geochemist
114:15 his sidekick, those guys collaborated for whole career, uh you know,
114:20 passed away a couple of years linton land, I think is still
114:24 , retired in Maryland. Right. these guys were interested in in thinking
114:31 some of the requirements for converting limestone dolomite. And they wondered if the
114:36 to calcium ratio in the poor fluid by parts per billion would be a
114:42 control. Right? If you can the amount of calcium, magnesium,
114:49 magnesium and calcium. Sorry, that should make it easier to convert
114:55 dolomite. Right? You're adding magnesium the system. And so they took
115:00 these different hydrological systems. And you see Sakas, that's the Arabic term
115:06 an evaporative tidal flat like we have of abu Dhabi today, ocean water
115:12 , brian subsurface, freshwater aquifers, , rivers, they cross flooded the
115:17 magnesium to calcium ratio versus salinity. present day ocean water There's a 3-1
115:27 between magnesium and calcium For 35 parts 1000 salinity. Okay. And then
115:35 decided on a stability relationship here. thought obviously, as you move further
115:41 further to the right here with higher calcium ratio, that should make dolomite
115:48 prone to precipitation. And if you're the left, would be more in
115:52 calcite story. Right. And Back the 60s, they started to discover
116:01 forming dolomite off of Abu Dhabi. . And these are the proto Dolomites
116:06 was talking about. And so where they find the first modern form of
116:12 dolomite? Right here, which makes . Right, Highest magnesium and calcium
116:18 , Highest salinity. These are true a critic Sokka deposits. And that
116:24 sense. Okay, so if you're evaporates, that might be a great
116:29 to make some dolomite. Alright. that's proved to be the case in
116:35 , many scenarios. Alright, That realized very quickly in the rock
116:41 we have thick straddle dolomite developed in places where you're not close to any
116:46 formed evaporates yet. We still see massive demonization. And so people
116:52 they came back to this diagram, said, well, wait a
116:55 folks on land said, what if move down this way and we start
116:59 , say ocean water with with fresh , we can make dolomite at lower
117:06 ease and lower baggies and a calcium . And so this is what led
117:12 the next popular model, which is so called mixing zone model.
117:17 and so I'm going to get into models, but I just want you
117:19 appreciate the roots of some of the here. All right, it all
117:24 back to this diagram right here where surmise that there would be a stability
117:29 between those two minerals based on salinity magnesium to calcium ratio. Alright,
117:37 , I've listed the popular models and appearance. The first of the hyper
117:42 Brian models with two different ways to fluids through these sediments. This is
117:49 for link back to the evaporating tidal and then the mixing zone came into
117:54 , coming off of the folk land and then a thing called Cohade convection
118:01 then basil de watering. Okay, basically this is late sixties, early
118:07 , late sixties, early seventies as . Coop convection in the early
118:12 based on the watering? Mid And then deep aerial came out of
118:18 Canada and this would be the time would be late eighties, early
118:22 Okay. In terms of its Right, So let's just work through
118:29 and we'll start with the first hyper brian model. You're sourcing magnesium from
118:35 and you're you're increasing the magnesium to ratio by doing what? By precipitating
118:41 or sulfate minerals out of that So if you take a standing bucket
118:46 seawater, what's the first phase of ? It's not salt, It is
118:53 carbonate and then it is gypsum, in hydrate and then it is hey
119:00 . Okay, so the initial precipitation evaporation obviously precipitates calcite minerals or sulfate
119:09 and that's going to raise the calcium ratio. Alright then it's a question
119:15 how you move that fluid through the . Do you pull it up by
119:23 ? That's called evaporative evaporative pumping or you create denser brines and push this
119:30 downward? That's called reflex. so there are two aspects to this
119:35 but both models. The timing is to be early near surface before the
119:41 of pressure solution. So, graphically geo chemically you should be able
119:45 show that these are early form right? Not burial related. So
119:51 this is applied to evaporating tidal flats what we call coastal Selena's. And
119:59 we do have some analog today around world. All right. That are
120:04 replaced with have one analog at Okay, but again, what's the
120:09 here? You've got to be linked to these evaporate deposits. Okay,
120:14 here's the cartoon that shows these We're going to talk about carbonate tidal
120:21 next weekend. Carbonate title Flat occurs the juncture between shallow subtitle and land
120:28 you throw sediment up against that land by storm processes. The marine water
120:34 extends under the title flat. if you go to a modern day
120:38 flat today and dig down about a or so, you will encounter the
120:42 water table. And so the theory that either by evaporative pumping when we
120:49 out evaporate minerals or just by precipitation just by just by you don't need
120:55 minerals per se. But if you precipitate out the phases of calcium carbonate
121:00 evaporation, you can pull out a calcite. What are you doing to
121:04 magnesium calcium ratio? You're still Alright. And so some people think
121:09 would pull that fluid up this And what do we see today on
121:13 surface? We see these so called crust. So that would be a
121:17 of that dramatization. But other people no, the fluid should go this
121:23 and they should Delaema ties this So, let's evaluate this. All
121:27 . The dolomite crust story is a bit misleading. All right. You
121:34 go to all the tidal flats both in the arid climates like abu
121:40 or to the humid climate like in northern Bahamas or to the semi arid
121:45 like north Caicos that we talked about find or walk and you gladly walk
121:53 this stuff because you've been sinking up your knees and mud. Right?
121:57 you like these little firm substrates These are thin, little crust about
122:01 thick. They're only a couple of thick. All right. But these
122:06 the so called dolomite crust. And you if you're not familiar, if
122:10 not been in the field, you appreciate that. This is not a
122:14 crust of dolomite. This is a layer of colloidal grain stone or low
122:19 pack stone thrown up on the tidal and then interstitial e cemented by mostly
122:26 reaganite and high mag calcite and a bit of dolomite. Okay, but
122:33 this is the first area of the we found modern forming dolomite. What's
122:38 over the last 60 years dolomite Right? People, they convey this
122:44 like this is solid dolomite. This all these models are trying to account
122:49 replacement dolomite, This is not replacement . This is dolomite cement.
122:57 when you look at the, when look at this fabric and you have
123:00 do it with a scanning electron microscope the crystals are so tiny. That's
123:05 microns. You see these little rhombus crystals that's proto dolomite, but there's
123:12 needles of Aragon night some of these dimensional crystals are high mack calcite.
123:17 protocol um is just part of the and I saw cement, there's no
123:21 . Okay, so that actually on these modern tidal flats, we find
123:26 fabric, but none of it's replace . So that's the first strike against
123:30 model. Okay, And then the model which says you you generate these
123:37 brines that go down like this. dilemma ties down here. Nobody's ever
123:42 this underneath these modern tidal flats. , in fact, this model comes
123:48 the Permian reef complex in west texas you see a situation like this,
123:54 you have your platform margin reef. high energy grain stones developed here progressively
123:59 and lower energy, more restricted carbonate in the inner part of the
124:03 culminating in subtitle or tidal flat of writes. Okay, this is where
124:09 get the natural and hydrate or gypsum outcrop and then what do you see
124:14 dip from all of this in All the down dip rocks are converted
124:19 dolomite until you get to the platform . The reef is not delimit ties
124:25 our crowd and it's not delimit ties it's incapable of being demonetized, It
124:32 all its almost all of its ferocity perm on the sea floor because the
124:35 sedimentation. So basically acts as a barrier. And so this stuff doesn't
124:41 demonetized. So you see where the comes from. It comes from the
124:45 , graphical distribution. I've got up evaporates. I've got down dip.
124:51 must be this right? Must be flexing down dip. Okay, well
124:58 some problems with this model too because go to other parts of the
125:01 The reef actually is delimited. And some of the four slope is
125:06 dilemma ties in other parts of of the trend. Okay,
125:10 but but this is all built off the historical outcrops that you see in
125:14 texas and new Mexico. So there one example on keiko's platform of early
125:22 replacement dolomite linked back to these All right. But it's not a
125:27 flat. It's what we call a Selena. And that occurs on this
125:32 here called West Caicos. Alright. this is what it Look like
125:39 This is dredged out about 15 years to make a Marina. And this
125:46 what we call a coastal Selena. is a natural depression between a holocene
125:52 ridge which is about 25 ft above level and an older pleistocene bridge,
125:58 is about 70 ft above present day level. Right? So this is
126:03 natural depression that catches seawater uh either over during major storm activity or pushed
126:10 breaking waves through the porous sand. periodically the Selena will fill up with
126:17 . Okay. And look how close are to the basin margin, That's
126:22 drop off into the deep water That's 6000 ft of water right
126:26 Okay. And so that's how close are to these coastal Carolinas. And
126:34 periodically this stuff uh will evaporate will down to hey light. You can
126:41 there was some attempt here to mine salt. Okay. And so you
126:46 Haley periodically. All right. And this caught our eye and we started
126:52 core these sequences. We we thought would be a good place to to
126:58 the reflux model. Right? When called the upper part of the
127:03 you find gypsum gypsum layers. Like see here just have been some of
127:09 organic mat material at the top. we thought if if that's the
127:13 Right, We're pulling calcium out to gypsum. What should the Bryans
127:17 They should sink downward, right. they're truly dense, they should they
127:21 sink downward and somewhere down below. should find demonization. Right. And
127:28 thought we'd find demonization, the underlying sequences. Right? So you can
127:33 you can see how we core Modern sediments. We core with this
127:38 irrigation tubing. The tubes are about diameter here. Okay. And you
127:44 , we can push these cores down the sediment. We use the handles
127:49 . We can put a pounding weight top of that and we can core
127:53 , you know, tens of feet more depending on the type of stuff
127:56 pouring into and then we can create and pull it back out and open
128:01 up right and or extrude it. don't even have to cut the
128:05 We can extrude it. And then basically what we did here. That's
128:10 of the cores where we just broke in half. So you can see
128:13 the internal structure looks like. so this piqued our interest. And
128:18 what we did was we came back the drilling rig by colleague Harold Wanless
128:23 teaches at the University of Miami brought grad students over to west coast and
128:27 lived on the island for a month they cord into the holocene and
128:33 All right. We wanted to document vertical strategic fee. We also thought
128:37 find dolomite in the pleistocene and we dolomite. But we didn't find it
128:42 the pleistocene. We found it in base of the holocene. So the
128:46 here represents the whole the same Dolomites replaced some of these scalable grain stones
128:51 were thrown back by storms into that Selena. And there's not an ounce
128:57 dolomite. And the older pleistocene because the cow crete. The cow creek
129:02 is a permeability barrier. Those fluids pass through the cal crete so the
129:08 come down like this and they move like this. So the demonization occurs
129:12 the base of the sequence where those rich brines on on that cal
129:18 Okay, and then you lose the effect upward, you go through gypsum
129:25 uh grain stone, and then you into that organic mix of that mix
129:31 organic santa, bacteria, mats and fabric. Okay, so we think
129:37 is a good example of reflux we published on this, I'll post
129:42 paper on blackboard. Um but what want you to appreciate is that when
129:48 look at the dramatized fabric, it just like what we see in the
129:51 . Record its replacement dolomite. And gets replaced is the finer sand
129:58 Okay, that's just all of this here. This is not mud,
130:02 no mud in the system. It's a it's a poorly sorted grain
130:07 . So the finer carbonate sand gets by dolomite because it's more reactive.
130:12 then during the advanced stages of for reasons we'll talk about later.
130:17 happens to the bigger grains, like pieces of Alameda, pieces of
130:21 pieces of coral, they dissolve out that's how you create the secondary
130:27 Okay, and this is pre compaction , These pores, these larger grains
130:32 completely surrounded by dolomite, they're frozen place. There's no way you're going
130:37 suture this stuff later. The stolen even a stronger mineral than calcite.
130:43 , so appreciate the relationship here. , very deep. Go back to
130:53 m 2 m. Not even about m at the most. Okay,
130:58 not very deep. Okay. So that you know that that's reflux
131:07 . Alright. It just hasn't been any of these modern title. Flat
131:11 yet. Okay, so the next that came into place, the mixing
131:15 model as I said, people realized quickly that there's lots of thick straddled
131:21 in the rock record that has no to nearby evaporates. So building off
131:29 falcon land diagram, people started to this bottle here where let's mix seawater
131:36 freshwater along the edges of these islands land masses that have a freshwater
131:43 And that happens. I told you a mixing zone right at that
131:48 And so the idea is that by the two fluids you reduce the
131:54 which means you reduce psionic competition. theoretically you make it easier for magnesium
132:01 substitute into the calcite to create the . So you're effectively increasing the magnesium
132:08 ratio. Even though you aren't increasing if you understand what I'm saying,
132:12 not increasing the magnesium calcium ratio. just trying to get rid of all
132:17 other cat ions that want to compete this poor space. Okay, that's
132:22 theory. All right. I'm just messenger here. I'm just I don't
132:27 in this model. So full I've never bought into this model.
132:33 . And part of the problem is haven't bought into this model because you
132:39 there's no modern and locks. And trust me, people have looked
132:43 all these modern mixing zones all over world and nobody's been able to find
132:48 or at best, they've been able find one or two little crystals of
132:51 cement, but not replacement dolomite. , either the model doesn't work,
132:58 I have a hard time believing that on what I just showed you for
133:02 , right, where it just took few 1000 years to make it on
133:07 , then, you know, if doesn't, it doesn't work or we
133:12 given given enough time to make it . Okay. But boy, this
133:18 stop people from from applying this to rock record. And I think the
133:23 is this Alright? If you have kind of topography doesn't have to be
133:29 area, it can be a low island like I showed you earlier,
133:33 in the Bahamas, you generated freshwater , the height of that freshwater lens
133:38 sea level will dictate how far off freshwater lens gets pushed. That's the
133:44 called guy been Hertzberg principle that says generally every foot you build freshwater above
133:51 level and unconfined aquifer. You can it 40 ft downward. Okay.
133:57 I mentioned the florida aquifer, That flows from lake Okeechobee all the
134:01 down to Miami and offshore. So that's what we're talking about.
134:06 right, the potential to do So, where would your mixing zone
134:09 ? It would be along the edges the aquifer where the fresh water mixes
134:14 the surrounding marine water that's trapped in set of it. Ok. And
134:19 if you want to make that the area for Dolan ization, will this
134:24 in the sea level curves right? you raise sea level through time,
134:30 gonna migrate up and delimit ties this . When you drop sea level,
134:34 gonna migrate downward to see how this becomes. A convenient way to make
134:39 travel dole might in the absence of evaporates. And so this has become
134:44 very popular model. All right. what do people do in the rock
134:49 ? They look for geological relationships that be consistent for something like this.
134:55 , so, sorry, going the way. So, here's the famous
135:11 case study from the Mississippian and the basin. And uh Illinois.
135:23 And what did they see here? saw a upward what we're going to
135:28 an upward chilling sequence next weekend where carbonate shallow up into a high energy
135:34 grain stone, which then is over by its time equivalent back show laguna
135:41 . And they realized that the dolomite not in the US shoals, but
135:46 the um Rachel's. Ok. And they mapped out the distribution of the
135:51 relative to the US sand bodies. saw this relationship here. They mapped
135:56 the strike of the zoo. It's bodies. And that's where you found
135:59 dolomite underneath. So, the interpretation oh, I must have had a
136:05 and sand body build up above sea . Get rained on develop a fresh
136:10 lands. And where am I going mix underneath? Right. The Konate
136:15 and the settlement's gonna mix with that water. That's where I'm gonna make
136:18 dolomite. And that would explain the that you see here. Okay,
136:23 , they interpreted this to be mixing demonization and then you probably don't know
136:30 . But you know, to publish demonization requires geochemistry. Okay, editors
136:38 let you publish papers without some kind geochemistry. And back then it would
136:43 been stable isotopes that we talked Carbon and oxygen trace elements.
136:48 so they published their geochemistry data with interpretation. All right. The next
136:55 comes along. Oh, I have similar setting. Actually. A lot
137:00 people didn't even get to that point they showed a similar setting. They
137:04 looked at their geochemical numbers. my numbers look like their numbers.
137:08 going to interpret next things out. you see this has gone on for
137:13 . To me this is classical circular . All right. None of this
137:17 constrained by photography. It's all driven geochemistry and this has always been the
137:24 . Right. Nobody could see what being replaced in the Dolomites.
137:29 Nobody could see whether the decolonization occurred or after pressure solution. Okay,
137:35 because because they're all all interpret this be early. Your service dramatization.
137:42 , so that's the limitation to this here. But it's a very popular
137:46 still today. And then Cohade unique setting. You're you're dealing with
137:53 steep sided oceanic platforms or atolls like have in the pacific today, surrounded
137:59 deep water. The theory is that long term circulation you slowly circulate but
138:07 through the steep sided platforms. And think most people agree that's probably a
138:13 uh phenomena. Cohort was an oceanographer proposed this idea. Alright. And
138:22 it passes through, it just thermally . That sets up a long term
138:28 cells. Okay, so you're deriving magnesium from seawater. The timing could
138:33 relatively early, but it could be after you've built some thickness to that
138:39 . And so some of the analogs be the bohemian platforms today that are
138:44 replaced by dolomite or some of the atolls. So here's the cartoon that
138:49 that shallow water platforms, steep The requirement for Cohade convection is a
138:55 deep water basin. So this is not going to apply to the rap
139:00 for your basin is 80 or 100 m of water depth, but maybe
139:06 like the Bahamas or atolls in the set up the circulation effect here.
139:13 interesting when you core into the according to the northern Bahamas. There've
139:18 a number of detest wells have been once they get, you know,
139:22 the surface, you know, 100 or so below the surface, they
139:26 into thick, massive straddled a llama northern Bahamas don't have evaporates.
139:32 so this might be a viable model that kind of phenomenon. Alright,
139:37 you're limited paleo geographically to this kind setting and most of our basins weren't
139:42 this in the rock record, They shallow interpret onek basins where you have
139:48 been able to set up that kind circulation. Okay, so I think
139:54 has some viability to areas like the or specific atolls, but limited to
140:00 we mostly prospect for in the rock . So, the next model that
140:05 along as the base on the de model and in this model, the
140:10 is that you source the magnesium from of shales or lime stones or evaporates
140:15 in the basin. Excuse me. basically you squeeze the stuff up into
140:24 Jason carbonate platform and related to this a so called squeegee mechanism where you
140:30 this more effectively with tectonic loading on part of the basin that forces the
140:36 to move up to the other side the basin, timing again, could
140:39 earlier. Late you need this unique to base a transition where the basin
140:44 filled with these kinds of deposits, don't have that today in the
140:49 Okay, but if you're familiar with paleozoic, you know, it's very
140:54 in the paleozoic carbonate platform running the and filled in either with shale or
141:00 . That was very, very common the in the paleozoic. Okay,
141:04 just don't see that today because most our basins are too deep today.
141:09 , That's why we have no modern . So here's the cartoon, you've
141:14 to have shale or evaporate or our carbonate out here compacting. The theory
141:19 that you squeeze magnesium rich fluids out that deepwater succession. You push it
141:25 into the adjacent carbonate platform. Where's course, impermeable carbonate right here.
141:31 , high energy reefs or high energy stones are usually on that model and
141:36 where you tend to see preferential So, the famous case study is
141:42 outcrop Called Viet build up in the rockies. Okay, it's a you
141:49 the scale here, that's uh four across. It's not a big platform
141:55 it's surrounded by deeper water shales and delicious carbonates. Most of the decolonization
142:02 confined to the periphery. So the here represents again greater than 40% by
142:10 dolomite. The blue is not pure , there can be dolomite back here
142:16 , but it makes up less than of the rock. Okay, so
142:21 you look at this strata graphically, is what you see a greater degree
142:26 decolonization along the edge of the build our platform. The inferred sources are
142:32 two sequences here. The flume and formations are shale. The theory
142:39 you just squeeze the stuff up and don't monetize that porous and permeable
142:43 Okay, I've always found this diagram because these are debris sheets of
142:50 shut out into the basin, presumably to the inferred source of the dramatizing
142:58 and there's still limestone. So it you wonder here about the viability of
143:03 model. But I guarantee you in rock record whenever anybody sees the platform
143:09 the organization were greatly expressed along the and you see an offshore shale or
143:17 , they're going to interpret this as base de watering model. Okay,
143:23 do a lot of carbonate carbonate platforms to begin with because of basement block
143:29 . Right, that creates the initial and then the platforms develop on top
143:34 that. So the other alternative explanation would be full control dramatization where the
143:40 come up from underlying sequences. one variation on this then would be
143:47 vap right story. So michigan basin a situation where you have you come
143:54 the carbonate platform into a shallow interpret basin there, little pinnacle reefs developed
144:01 here that are going to talk about a play type later, but there
144:04 case in deep water carbonates and deep evaporates. And so the model here
144:10 a version of basil de watering, during burial. People interpret the magnesium
144:16 brian's to be pushed from the a evaporate into the reefs to throw
144:24 And so all of the oil productive gas productive reefs have to be
144:29 Ized but not all of the restart . So it's not an unequivocal
144:35 Okay, but again, this close of evaporates and limestone would lead many
144:41 to interpret this as a variation on reflux variation on the of the water
144:47 story. Okay, so those are the popular models in the literature
144:52 Okay, the least popular model, think in part because you have to
144:58 some effort into this to figure it . You have to look at the
145:01 , right? A lot of companies want to look at the rocks they
145:04 to prospect on the seismic and logs, right? They don't want
145:07 core. But the last model here the so called deep barrel demonization
145:13 which says that you cannibalize the magnesium either host limestone or dolomite or you
145:21 it from deeper basin all brines that reacting with evaporating sequences of death.
145:27 , and then you bring it bring it up either by regional compaction
145:31 flow. So this could be a of the basal de watering model.
145:36 after the onset of pressure solution or bring it up along fault and fracture
145:42 and I would argue you deliver it the system along things like style.
145:47 so the style, it's actually become conduit for these fluids. Okay,
145:53 that's what we mean by deep barrel coincident with pressure solution, onset of
145:59 solution or after. It doesn't matter the environmental association is. But you're
146:04 see for these case studies that all these Dolomites our faces control because you
146:10 need underlying processing permeability when these fluids in. Okay, so let me
146:18 up by showing you a couple examples , how we prove the timing relationship
146:23 the photography. This is a Devonian limestone staying with the lizard and red
146:30 . This is the normal thin section . This is the white paper
146:34 Uh you can see the benefits of white paper technique as they sharpen up
146:39 distribution of the red stain. But importantly, they reveal pressure solution.
146:44 that you have a hard time seen the right. Okay. And then
146:49 at the style lights and the dolomite you can see the Dolomites not only
146:54 along the style light, but it cuts parts of the style lights.
146:58 , it's a simple cross cutting relationship tells you some of that dolomite formed
147:03 that style line. Well, that's definition of barrel dolomite. Okay,
147:09 how you try to get a handle the timing. Okay. Here's another
147:13 you try to get a handle on timing. This is a thin section
147:17 a dull Estonia Jurassic Dulles stone from France in the Pyrenees Mountains? It's
147:23 of a gas reservoir, deeply buried reservoir about 16,000 ft of burial.
147:30 this is you know, you see dolomite here. I try to stay
147:34 this with the lizard. Red. takes no stain. You see the
147:38 , you see cloudy and light colored crystals. Look at the shape of
147:43 crystals, that's hardly Robin Wright. what he's talking about. And he
147:47 . Sub federal morphology. Okay. , you know, strata graphically this
147:54 this is the gas reservoir and it down dip from an up dip evaporate
147:59 faces. Alright, So what did french interpret the timing to be early
148:05 , Right? Just have those fluids down like we talked about. And
148:09 ties something down dip. But what this? Something, You can't tell
148:14 that fabric is. Right. this is actually the first thin section
148:20 revealed the ability of the fluorescence technology see through the masking effects of the
148:26 . We stumbled on this by We're actually looking for hydro hydrocarbon inclusions
148:32 inclusions in these Dolomites, which you to do it. Very high
148:37 very high magnification. And I backed the magnification to the lower magnification.
148:45 I went from this to this. . And what do you see,
148:51 see the outlines of these kids and Lloyd's Okay. The circular grains.
148:59 then what do you pick up in them, you see the sutra grain
149:03 And if you go back and forth these different light sources, you can
149:07 that the dolomite over lies the pressure contacts. So it's barrel dolomite.
149:12 have to conclude that anyway. This not early form dolomite because the US
149:17 future together. Right? I told when you get pre compaction stuff,
149:21 freeze that fabric. Okay, so is barreled organization. This is not
149:29 reflex organization. And then the porosity you would have called in her crystal
149:36 her buggy, which there's no relationship the deposition of fabric is actually what
149:43 call molding or partial moldy curiosity is to the centers of these grains.
149:49 you can argue about whether that was early or late by dolomite dissolution but
149:54 fabric selective ferocity. And then look else the fluorescence picks up. It
149:59 up some of the back selling of ferocity was cement. You see the
150:04 here. Like I showed you for luminescence but this is due to
150:09 Alright, so that's those are pork cement. And one last example here
150:16 I showed this photograph yesterday with the paper and fluorescence technique. All
150:21 This is the example from the Jurassic over in the gulf coast here.
150:26 see the dolomite crystals with a ton piracy but it's all filled with bitumen
150:31 here's the fluorescent view with the pill Lloyd's sutured together. I've highlighted the
150:37 . Grand contacts between the lloyds. the fact that the grains are suitor
150:42 you this is replacement Dolan night. , this is the kind of stuff
150:48 needs to be done before you throw geochemistry at these rocks. Okay.
150:52 this is what doesn't get done in literature. When if you ever get
150:57 the literature on decolonization, you'll see show one picture of dolomite with the
151:03 center Dolomites. They showed dolomite crystals a cloudy center dolomite and they say
151:09 colloidal. That's what got replaced. to wacky stone portal packs down.
151:16 not good enough. You need to to the next step which is the
151:19 technology or the white paper to prove that's actually a relic grain or
151:25 Okay. All replacement dolomite. Whether replaces mike, right? Or grain
151:31 creates a little cloudy center in the and then clear rims around it.
151:37 , so that doesn't prove that's a grain. Alright, so let's leave
151:41 at that. Okay, so let's a five minute break. We'll come
151:47 and we'll get into the what I is more important for our discussion,
151:52 is what are the effects of decolonization reservoir quality. Okay. Does it
151:58 ferocity. Does it include ferocity. ? You've already seen what the organization
152:03 to the deposition? All texture. it perfectly preserves it. Sometimes it
152:08 it. But let's get into this here. So we'll start back up
152:12 five minutes. So that's because let's our discussion about prophecy and perm evolution
152:25 Dulles stones, as I said we don't fully understand everything that we
152:30 , but we see it over and again, that you should be familiar
152:34 some of the different pathways for evolving and permeability. So, I want
152:38 start this discussion by taking you through wisdom and you all know what to
152:45 with conventional wisdom. Right? Some it's good, some of it's not
152:48 good. But conventional wisdom is that in Dola stones process is always thought
152:55 be early and your surface because most the biases toward the popular models that
153:01 just took you through, right. are mostly skewed toward early near surface
153:06 . Most people think that gets what replaced in the rock record. Esma
153:11 limestone because mike reid is more right? Higher surface area volume
153:18 And if you're gonna if you're gonna fluids into a Mc ride, you've
153:22 to do it early while it still the permeability. So that's why we
153:25 that bias toward early on their And then where you see the secondary
153:30 developed, its invariable related to leaching calcium material. Okay. And everybody
153:38 downplayed the deposition controls for the reasons just said, nobody looked at these
153:42 with the white paper or fluorescent But it turns out when you do
153:47 and you really put the effort into this, you can see that there's
153:50 underlying deposition control, that makes right? You had to have crossing
153:56 when those fluids came through, no what the timing relationship. And because
154:01 could establish a deposition control, everybody forced to describe that preserved ferocity is
154:07 crystalline or buggy, which is well in our last lecture today as it
154:13 either related to the growth of the crystals that center crystalline or the term
154:18 means I can't relate it to All right. You don't want to
154:22 that in the world of dolomite. want to be able to relate back
154:25 deposition all faces that you can map the subsurface. Right? That's how
154:29 extend these trends in the subsurface. then with respect to dolomite dissolution,
154:36 know, I told you how difficult is to just to dissolve calcite.
154:40 ? You can't do it in fresh ? Well, the mineral dolomite,
154:44 thinks is the most stable of all four carbonate minerals. And people don't
154:49 it's gonna dissolve and where it's been in literature as being dissolved out,
154:54 been described as this process called de where you take little isolated randy crystals
155:02 dolomite dissolve it out and then replace with calcite. Okay. And that's
155:08 been described as a near surface freshwater phenomena which I just find mind boggling
155:14 if you can't dissolve calcite and fresh and Dolomites more stable than calcite,
155:20 would you reach calcite? Why would reach dolomite in fresh water?
155:25 It turns out, you know, that turns out that dole dole,
155:30 dissolution actually is more common than we , but everybody's downplayed it as a
155:35 mechanism because of this perceived stability But what did I mention when we
155:42 ? I said dolomite starts off as poorly ordered calcium rich mineral.
155:48 Very unstable proto dolomite. But even older Dolomites never achieved perfect stability.
155:54 if they see the right kind of , the right kind of conditions,
155:57 carbonate mineral is prone to dissolution. , so let me share with you
156:05 relationships, we see time and time . I'll back this up with some
156:09 studies and then we'll finish up by about the potential of the leech
156:14 Ized fabric. Alright. And create quality. So the first relationship here
156:21 processing an increase or decrease depending on and texture and degree of demonization.
156:27 gonna take you through two case studies show this relationship. And then where
156:31 have by model or pollen mobile deposits we have poorly sorted fabric,
156:37 with finer grained material, it doesn't to be Mick. Right,
156:40 And larger grains. Okay, so wacky stone. Think pack stone,
156:46 root stone thing float stone. The finer grained stuff gets stigmatized first
156:53 then what happens you leech out the larger grains and everybody thinks that they
156:58 leeched out by their cal citic. . And I'd say that's pretty
157:03 Alright. And then dolomite, we there's a stronger mental than calcite.
157:08 if you can create process the early demonization, you're going to preserve it
157:12 much greater barrel depths. Okay, it's a stronger mineral, it's going
157:16 resist pressure solution where we do see of dramatized fabrics is commonly associated with
157:24 hygienic and hydrates or cal sites that passage of calcium rich fluids. So
157:31 you want to jump on the folk bandwagon and say increasing magnesium and calcium
157:38 makes dolomite, turn that around, the calcium to magnesium ratio theoretically should
157:47 what should make dolomite unstable and prone dissolution. That's exactly what we see
157:53 the rock record. Whether we understand relationship or not, where we see
157:58 solution, What do we have hanging in those sequences? We have late
158:03 and hydrates, calcium sulfate or late calcite. It's okay. And then
158:09 respect to fracturing, as I mentioned , you expect a higher degree of
158:14 and dolomite because it's a more brittle compared to calcite or compared to things
158:20 shale and stuff like that. so let's build on these points
158:24 we'll start with the first point about texture controlling and the degree of decolonization
158:29 the porosity development and this diagram came of a paper in the same volume
158:37 done and published his classification scheme. was a Powers was a chief geologist
158:45 Saudi Aramco. Okay. And he publish this diagram per se. But
158:51 published the data to to make this . All right. Talking about the
158:57 era B. All right. And don't know if you know anything about
159:01 Arabia but they're big oil fields like are produced from what's called the arab
159:06 sequence most of it is limestone But can get anywhere in that sequence.
159:12 can get up to 50 ft of massive dolomite that replaces those lime stones
159:18 if it has prostate yields hydrocarbon Okay, so we took his database
159:24 he published published tables of this data showed how changing the degree of decolonization
159:31 the process of evolution. So, plot here is percent volume of rock
159:38 I'm sorry porosity. Okay, let start all over again, percent volume
159:45 rock over here, percent volume of over here. Okay, so what's
159:50 zero point that would be a Pure limestone with no dolomite and 20%
159:56 . Okay, that's a typical araby reservoir today. Okay, The whole
160:07 today. The RV is a pure . Most of the reservoir is a
160:14 limestone with 20% porosity. Okay, what they're producing all their great volumes
160:21 hydrocarbon from principally. Alright. And what did they observe as you added
160:26 dolomite to the arab the limestone you increase the amount of dolomite to
160:31 right. What happens to porosity? actually decreases and it continues to decrease
160:38 you get to this point here, by Volume Dolomite. And then
160:44 you see the remaining calcite leaches out that gives you a bump in
160:49 Okay, that's when you create the arab d dola stone reservoir.
160:55 If you trap the hydrocarbons right you end up with a great
161:01 If you don't attract the hydrocarbons, keep bringing the dull monetizing fluid in
161:05 are you gonna do? You're gonna that process with dolomite cement and you're
161:09 to evolve to a dolo tombstone right . Okay, so timing is everything
161:17 geology, right? You've gotta, has to be meshed together,
161:22 The generation of the reservoir quality, trap the migration and uh but what
161:29 see here is very common in the record. Okay, I will attest
161:35 this because in my career, I've looked at thousands of thin sections of
161:41 limestone or Dulles stone. And you commonly this relationship here where you get
161:47 the advanced stages of this dramatization You see this bump in porosity where
161:53 remaining calc tick material, whether it's or grains dissolves out to create that
162:00 process, but I can also tell , I've looked at lots of sequences
162:05 the relationship goes like this, You see that process developed. Okay,
162:12 it's not unequivocal but it's common enough you should be familiar with what we're
162:17 about here. Okay, so let show you some of the arab d
162:21 again, you need a host limestone of being demonetized. It has to
162:26 porosity permeability. So the first dollarization through, it starts reacting with the
162:32 and matrix. And then what is , what do these crystals do they
162:36 into the pore space? That's why first phases of demonization of proxy destructive
162:42 replacing but also over growing as cement that ferocity. Alright, so porosity
162:49 down, you get to that 70 by volume Demonization boom, You reach
162:58 the remaining calcium material, that could the matrix, that could be remaining
163:03 grains, but that's what gives you 20% bump in ferocity. Okay,
163:08 if you entrapped the hydrocarbons right now end up with a good reservoir if
163:12 don't you're going to fill this process with dolomite cement and you're going to
163:17 to a dola tombstone at 100% by dolomite. Okay, I can tell
163:24 this is very common. Okay, again it's not unequivocal. Alright,
163:29 we don't fully understand what's going on but we see it time and time
163:33 . Okay, here's another example from Jurassic smack over sequence in east
163:39 we'll talk about this as a play our last weekend and you know,
163:45 of the classical production in the smack is limestone that I've alluded to.
163:50 sometimes in the more deeply very part the trend in east texas. Things
163:54 to be demonetized. And so we off with the host rock which in
163:59 texas analytic grain stone with some degree preserved primary porosity. And think you
164:06 see the grains are already buried before dolomite comes in. So sometimes this
164:11 occurs during burial. It doesn't have be early dolomite comes in. It
164:16 only go after the grains because there's mud in the system. So we
164:20 adding dolomite. It goes after the parts of the of the U.
164:25 . And P. Lloyds and then what grows into that poor system as
164:29 cement. If you're going to trap hydrocarbons before it goes too far,
164:34 end up with a good stone. , taking advantage of this porosity and
164:39 process that is created by beaching during advanced stage development station. So it's
164:45 same relationship I just showed you for but it's a different texture.
164:50 everybody appreciate what I'm saying. So is the storage for the gas and
164:56 happens to Dolomites is a fracture. you connect this process by fractures.
165:02 that you needed for for a good reservoir. But I think you see
165:06 relationship here, right? It's during advanced stages where the remaining calcifications leech
165:12 sometimes asthma critic matrix, sometimes that's centers of the zoo IDs or
165:17 Okay. And here's some of that filled in later with calcite and and
165:23 drank cement. Right. Okay. I mentioned the the texture of the
165:30 controlling the fabric by mobile texture means have big grains of small grains of
165:37 poorly sorted fabric. Right? Wacky ? Pack stones on a reef system
165:43 the LaDuke and the Devonian. This have been a rude stone. These
165:48 pieces of branching stream. It operate that was the dilemma ties matrix and
165:55 forever thought this was what mud. if you've ever been to a modern
166:00 flat, which this is behind the , you would feel the surge of
166:07 after the wave breaks. Right? be no mud in this environment.
166:11 ? This would be a grain stone in the modern but nobody could prove
166:16 the texture was until you looked at with fluorescent or white paper technique.
166:21 is a scalable colloidal grain step. is the breakdown product of the
166:28 so you had finer grain sand What's the definition of a root
166:34 Remember the big grains are touching in D. Okay, So what's going
166:39 get to acclimatize 1st? That and what leaches out there. The advanced
166:45 that presumably as calc text. Irma That gives you the secondary porosity.
166:53 what happens to the permeability. Look the permeability here. 125 Darcy's.
166:59 is incredibly rare. Okay. To that kind of Permeability, but it's
167:05 reflection of the fact that those holes all touching in three D.
167:10 remember the finger like or branching stem roids are touching in three D.
167:15 basically give you these little channels of . Alright, that's the beauty of
167:22 reef related degree. Okay, not do you get the good bumping
167:26 but you get a good bump in mobility. Okay. And then the
167:33 diagram talked about the strength of the dolomite resisting pressure solution. Here's another
167:40 of the smack over trend in Alabama florida. It's a deeper part of
167:45 trend. It's an oil field called field. And Jay Field is about
167:50 to 16,000 ft of burial today. you're used to all these circular roads
167:59 we've talked about before. Right in smack over. And so everybody thinks
168:03 circular holes or spherical holes are leeched ids. But this is not the
168:08 of the trend that have you with deposition. These were actually p Lloyd's
168:13 mostly fecal pellet fabric. All pal idol with the mud matrix.
168:19 these are political pack stones. And know this because you can trace this
168:24 old Exxon field. I've seen the for jay field, you can trace
168:28 dolma ties equivalent. You can see transition into delimited colloidal uh pack stone
168:35 then into paxton. Okay, so , it's here but a by mobile
168:41 . Right, So fine grained larger sand sized grains. What got
168:47 first democratic matrix around the pill And then during the advanced stages of
168:53 . Ization you leech out the remaining of those calcified P lloyds.
168:59 now This is 15 16,000 ft of , no collapse of the porosity,
169:07 pressure solution between the grains, no to green suit. This represents excuse
169:15 a minute. This represents the strength the mineral dolomite and resisting pressure
169:26 Okay, There are examples like this the Mississippian of the Williston Basin in
169:33 Western us where this fabric is preserved to 25,000 ft. Okay, You
169:42 never do this with an early form cement. Okay. In my
169:47 once you get down to about ft, everything starts to give that
169:53 process will start to collapse on its . Okay, But here in the
169:57 of Dolomite, you can hold on this to over 20,000 ft of
170:01 Okay, that's the beauty of democratizing early and preserving Torossian depth.
170:10 and then one of the last points the fracturing relationship. This is an
170:17 diagram published in 1972 that states the forgiven burial depth forgiven tectonic stress,
170:25 the degree of fracturing between dolomite and . It's greater than four times in
170:33 color stone compared to the limestone. . I taught a course for
170:39 the National Oil Company of Mexico Got 10 years ago now and you
170:45 I went to Mexico and I presented course. I present not this course
170:51 this, but with the samples and exercises and at the end of the
170:56 instead of doing a core exercise which normally do when I teach in the
171:00 I had them pull out some of they wanted to pull out some of
171:05 core examples from some of their big fields. Alright. And this is
171:10 of one of their big fields and can see deeply buried. Right?
171:14 over 15,000 ft of burial. And saw this relationship with this darker fabric
171:20 lighter fabric. And uh you I asked him to give me some
171:29 and so I put acid on this . It fizzes right off the
171:32 That's limestone. I put acid on and nothing fizzed until I scratched it
171:37 a knife. Then it started to . Okay, that's dolomite, that's
171:43 . I don't know if you can this but this is riddled with vertical
171:47 . There's hardly any fractures in the limestone so that just restates the
171:52 Okay, that you're gonna get a degree of fracturing in edelstone.
171:57 if you have ferocity, even if not well connected porosity may be connected
172:02 fractures. Okay, Alright, so finish up this discussion by talking about
172:11 the evolution and dolar stones. Matrix we expect to be replaced first
172:19 it's more reactive. And then what is we often see later. Not
172:24 , but later the larger grains is about. And most people would say
172:29 larger grains dissolve when there cal city I actually don't disagree with that.
172:34 think that's the norm. Okay, when that's the case, where do
172:38 see the secondary process? It's always to the centers of those larger grains
172:44 you go after the matrix first and you come after the outer parts of
172:47 grains until you get to that threshold 75, by volume and then you
172:54 out the centers of those holes. , so the controversy is can you
172:59 this from one fluid or do you to fluids? One to delimit ties
173:04 to leach. Of course you can people that will argue both cases.
173:09 , clearly you can do this from fluid because we see this phenomena operating
173:15 basins where the fabric is encased in . There's no way you would get
173:21 fluid in there like fresh water. ? But other people say no,
173:26 need to fluids one to delimit ties then you need to sweep another fluid
173:30 . Of course they would invoke which I said to me is mind
173:36 because calcite is not going to dissolve freshwater. But that's the old mindset
173:41 the literature. All dissolution equates to to fresh water. Okay, now
173:47 either even bigger controversy now is, you take a limestone and replace it
173:53 dolomite and obviously create some porosity or ferocity and then bring another fluid in
174:02 dissolve some of that dramatized fabric to the final reservoir quality. That would
174:08 two fluids. One to delimit ties to leech the dramatized fabric and the
174:14 is yes, sorry, the answer yes. And here's the example from
174:29 Canada. Okay, the the deadbolt is a mississippian sequence, a gas
174:38 in the subsurface. And look at fabric here, the bluest porosity.
174:45 at some of the dolomite crystals are unaltered and then see a transition from
174:51 dissolution. Two more complete dissolution to removal to create the liver.
174:58 big pores like you see there, don't know how you do that unless
175:02 you say that ferocity was created by leaching. Abdullah might. Okay,
175:09 not an ounce of calcite in these . The transition from this to this
175:15 progressive bleaching of that dramatized fabric. , so that's the controversy. All
175:21 , so let me convince you of we would tell the difference between what
175:26 started with with the Arab D and I'm going to show you for some
175:29 this devonian stuff. So let me me start this discussion by showing you
175:35 fabric from the an outcrop in Western . Outside of Calgary, there's a
175:41 town called Can more and you can up the side of some of the
175:46 outside of Can more and see these strom atop right Pat trees in outcrop
175:52 have been replaced by dolomite. and that's what this is a picture
175:57 . All right, And what I'm to show you here is what I
176:00 is the norm that we normally see the in the rock record, both
176:04 outcrop and the subsurface. So we a bimodal texture. Again, these
176:11 features here are called bulbous drama Top . They're like the modern head corals
176:17 terms of their des positional setting. . And then everybody thinks that darker
176:23 fabric here is mud between the grains now Delaema ties. Everything has been
176:29 by dolomite. But it turns out you look at this with the white
176:32 fluorescence technique, this is what we political grain stone. The P Lloyd's
176:37 the breakdown product of the remote They're broken down by boring activity by
176:43 action on the sea floor. so this is actually what people would
176:47 a float stone or arguably root depending if you think this stuff is
176:54 with with a little grain stone Okay, so we've got that fabric
176:59 start with. There'll be piracy associated the grains with the matrix in perm
177:06 comes in. What's it going to after first? It's going to go
177:09 the gray stuff because that's finer Okay. And then after a
177:14 notices the finer grain stuff. What it going to go after next?
177:18 going to go after the outer parts the grain of the bulb. Instrument
177:22 from all sides, Right? like a centripetal effect, right?
177:26 gonna come out the grains all Until what? Until you get to
177:31 magical point of 75, demonization. then what happens, the cal
177:37 centers of those remaining strom's leach out give you that ferocity. Okay.
177:44 I would say that's the norm. ? And when you look at the
177:47 of that ferocity, the dolomite crystals the edge show no signs of
177:53 There. Nice little you. He'd dolomite crystals that replaced the storm atop
177:58 . Until you reached out the center the cal Civic. Okay, Everybody
178:04 what I'm saying? That's right, here. Yeah, you're you're where
178:17 get the bump in ferocity, You feel you feel this porosity and
178:25 feel some of the there might be porosity in the matrix that you would
178:30 . All right, but that hasn't yet. Okay, Okay, So
178:38 open. All that black is open always confined to the centers of the
178:42 . Alright. In other words, not randomly distributed. It's always confined
178:47 the centers of the grains and you no evidence of dolomite crystal dissolution.
178:53 , that's the norm. Okay, basically this is the this is the
179:00 that most people apply for. Dramatization a precursor limestone. You start off
179:06 uh with limestone fabric, alright, and matrix and porosity. The dolomite
179:15 comes in and the demonization does what starts to go after the matrix.
179:22 starts to create first micro porosity within of the grain fabric. But what
179:28 at the end towards that, 75 by vine dolomite, you leech out
179:33 remaining centers of those calcified grains. basically what I showed you now,
179:37 . Okay, now let me take to a different sequence in the Western
179:43 , it's a little bit older than I just showed you for that
179:47 This is called the keg river and is subsurface data now. Okay,
179:53 the bulbous troma. Top roid. the political grain stone matrix.
179:58 And the black color, darker There is a bit um effect that
180:03 some of the ferocity. Okay, this rock has been replaced completely by
180:11 and then look at the porosity, porosity in the center of that dilemma
180:16 fabric. There's actually a greater degree secondary process around the edges. There's
180:21 porosity here. Okay. In other , the process is not confined to
180:25 center of the grain, it's all the place and when you look at
180:30 process in detail, you'll see these in a minute. You see evidence
180:34 dolomite. Crystal dissolution. Okay, this is dolomite dissolution on a bigger
180:41 . In other words, it took fluids to do this. One to
180:44 ties this fabric and then one to through and start leeching this fabric in
180:49 matrix and randomly in that dramatized So it's a different story.
180:58 here's another faces where you see the relationship these little grains here, our
181:04 of storm boat operate called amphora. and to Pora is a little stick
181:11 branching storm a top that looks like red algae I showed you this morning
181:16 we're talking about the classification. Same . Okay. And this rock is
181:24 by a rapport with the critic colloidal and this rock has been replaced completely
181:30 dolomite. There's no calcite in these . But look at some of these
181:34 top roids. The green arrows point the perfectly preserved dramatized fabric. You
181:40 the center that little center hole that's part of its micro structure.
181:45 not dissolution. Okay, and then at the transition from the green arrows
181:50 the red arrows. You see partial . But sometimes it's on the
181:56 Sometimes it's at the center and then what happens is the grains get completely
182:01 out. Okay, so it's random because you've already gone past that point
182:09 the calcite is gone. Okay, been replaced by dolomite. And now
182:14 fluids coming through to randomly attack those and create that ferocity. And when
182:19 look at the thin section, you the corrosion and dissolution. Other replacement
182:24 . Okay, That creates that random the effect that you see there.
182:29 , you wouldn't see this in the example I showed you from that
182:33 Okay, everybody under. You don't to agree with what I'm saying,
182:37 least appreciate what I'm saying here is this is Dolan my dissolution on a
182:43 scale that creates the final reservoir Okay. And it took two fluids
182:49 do this. One to delimit ties to leach and we'll talk about the
182:54 that create the leaching in a Okay. But the timing here is
183:00 always burial based on the relationship of processing. The style lights, but
183:05 based on on geochemistry. So, the same story that I developed for
183:11 limestone burial dissolution. We can develop this dull, dull, dull metalized
183:18 as well. Okay, we see dissolved after they've already been sutured.
183:24 see secondary process preserved longer cutting style . We see burial fractures that cut
183:30 lights and we see along the edges those fractures, the dolomite being
183:35 So, we know we're delivering fluids of dissolving. So, think back
183:42 that core piece. I just showed with the alfa Pora. And you
183:45 at the finder matrix in between those amphora grains are smaller pieces of amphora
183:51 this is But this is what the thin section looks like. You just
183:56 the porosity and you see cloudy and dolomite. But you don't see any
184:01 of really grains in the normal thin view. But you do see evidence
184:06 dolomite crystal disillusion. You see the . Okay? So you know there's
184:11 some gold, some some dolomite dissolution it's hard to see the timing relationship
184:22 you can see the timing relationship with white paper technique. All right.
184:27 what are you looking at here? looking at smaller pieces of amphora.
184:34 . And you can see the relic boundary of the grains and then what
184:37 that? Obviously a super grain So the fact that those grains are
184:42 . First of all, it tells that replacement dolomite was burial.
184:48 And then the process was created by of that dolma ties fabric after some
184:54 of burial. And look at the of process is not confined to the
184:58 of the grains. It's all over place. It's random. That's the
185:02 observation. It's random secondary process. not mold it right at the center
185:07 those grains. Like we saw when leech the calcium material. Okay?
185:12 if if you could do this at scale, there's no reason why you
185:17 expand it to a greater extent and creating larger scale buggy porosity like you
185:24 here. All right, these are famous zebra Dolomites that people talk about
185:30 you get the skylight, it's dissolved along the style light to create the
185:36 ferocity. It back fills with these Saville Dolomites. I'll explain this a
185:41 . Okay. And this is why think the skylights control the fluid flow
185:46 of this crosscutting relationship, but it works where the fractures intersect these skylights
185:52 bring up the fluids and then they moved laterally. Okay. And then
185:57 you could do it on this why can't you solution? And large
186:02 these dolar stones to a bigger extent you get solution collapse. Okay.
186:11 this is what we call burial appreciation this is the by product. All
186:17 . This is the dullest own sequence rotated to class. And why is
186:22 burial appreciation? Because these classes are with skylights. But the style lights
186:28 all different angles to each other and horizon. You can't do this in
186:33 air surface setting. Okay. If did it early, it's just an
186:38 breakfast, which is everybody what everybody to be your style. It should
186:42 line up like this right principle to perpendicular principal stress direction. In other
186:49 , you should see this all these class and the skylight should line up
186:55 this. If that's an early form . But this is what we see
186:59 is modeled off of that photograph. , everybody appreciate what I'm saying.
187:04 key observation is the fact that these all different angles to each other and
187:09 horizon. That means that that limestone buried into the realm of pressure solution
187:17 got replaced by dolomite and then got to the big enough scale where you
187:22 a hole where things collapsed into that . Okay, that's barrel graduation.
187:29 sometimes you actually preserve the porosity and have reservoir quality associated with it.
187:37 , so this is burial appreciation. the caveat here, is that just
187:43 I have a Brescia, you can't the Brexit by itself to say that's
187:47 surface cursed because you can also do to death. Okay, just like
187:54 said, you can't use secondary porosity to equate the fresh water because I
187:59 you three different ways to make secondary . Okay, we're gonna put this
188:05 into context later, but I just you to appreciate the timing relationship and
188:10 all of this graduation. All of stolen my dissolution on a grander scale
188:15 related to fractures. The fractures deliver fluids that promote dissolution because you see
188:23 of dolomite crystals along the edge of fracture plane. Okay, so let's
188:28 up by talking about what drives There are two ways to drive
188:32 One is past calcium rich fluids or rich fluids through the rock to create
188:39 conditions for that promote delimit dissolution or bring acid fluids and that's where the
188:45 we call TSR thermo chemical sulfate reduction into play. Okay, so here's
188:53 simple equation for TSR you need dissolved in the system. Either bring it
189:00 from underlying evaporated successions or you locally out sulfate minerals. It reacts with
189:07 , hydrocarbon doesn't mean oil and hydrocarbons and organic material. Right?
189:12 it can be organic material to start react. And you know, any
189:17 of organic material is going to generate two S. Well that's the catalyst
189:22 kicks off this process and you do at high temperature. So the cut
189:27 is about 80 C. So we're talking about bacterial sulfate reduction, that's
189:33 going to generate this phenomena. And do you do in these sequences?
189:37 produce a series of policy sulfide So in all these goldstone sequences you
189:43 galina fallow, right, Marcus site . Right, okay. But then
189:49 reduced to data sulfur. And then do you do at the end?
189:53 produce more H two s. So two s. is a byproduct And
189:58 of these reservoirs have up to 1213% two s. And it's that H2
190:04 reacting with water that creates sulfuric acid not only destroys the steel casing of
190:09 reservoirs, it creates the ferocity. . And most of these fluids are
190:17 be what we call hydrothermal or D. People talk about hydrothermal
190:24 HTV Alright again, hydrothermal dolomite beans you could show geo chemically that dolomite
190:31 the temperatures at least 5 to 10 higher than you would predict for that
190:37 temperature burial depth. Okay. And is the by product? It's saddle
190:44 . That was that white crystalline dolomite showed you in that previous core photo
190:49 we call it saddle dolomite because the lattice is distorted. That's the temperature
190:55 that creates that distortion. Okay, all the geochemistry that's been published for
191:00 dolomite shows that it never precipitates at temperature lower than about 80 C.
191:07 the way up to over 200 Okay, so what does that mean
191:12 the rock record? If you see dolomite, it is not always a
191:17 dolomite, but it's always a barrel , whether it's in limestone or Dulles
191:22 . Okay, and to prove that truly hydrothermal, you have to do
191:28 inclusion studies here to show precipitated at l temperature elevated above what you would
191:34 for that barrel depth. Okay, appreciate the benefits of salad dolomite.
191:42 , so to finish up here, do we see fabric stone fabrics dissolved
191:46 a grander scale. It's always where get late stage cal sites or anhydride
191:52 or we see direct or indirect evidence the TSR phenomenon. Okay, so
192:00 indirect evidence Would be high amount of . two s right Or the sulfide
192:08 that we talked about before that are place alongside the dolomite dissolution. And
192:16 that would be you know that or would be where we see evidence of
192:20 calcium rich fluids coming into the So this is the keg river again
192:25 we had the dullest in Brescia. here you see the late stage and
192:29 cements that zebra fabric that I showed earlier with the horizontal saddle. Dole
192:35 I are fed by fractures and they're with the and hydrate. In fact
192:41 lot of times you get a late and hydrate cement that plug some of
192:44 zebra ferocity. Okay, so always attention to the late stage the minerals
192:51 come into these rocks because sometimes they're of the story for driving dolomite
192:58 On the finer scale. Here's a example from Russia where the dolomite crystals
193:04 clearly dissolved out And then back filled late stage cal sites we've analyzed these
193:09 chemically to infer high temperatures of So high hotter calcium rich fluids,
193:16 see this dolomite dissolution. And then last example here is a permian
193:23 this used to be a fuel cell it. Remember those big cigar shaped
193:29 and the upper paleozoic centimeter scale, get demonetized in west texas and then
193:38 , what happens is that replacing dolomite to dissolve out. We have late
193:43 on hydroids coming in and eventually all this will, will reach out to
193:48 a mold of a fuel cell in . Okay, so that's late stage
193:57 solution of gold metalized fabric, that's common link, calcium rich fluids,
194:02 , This solution, elevated temperatures, this reaction. Okay, questions or
194:10 about that. Alright, so we to take a little stretch break
194:19 short little stretch break or you want just wrap it up. The last
194:27 is on ferocity, it's not gonna that long. So we'll actually get
194:30 before 5:00. So let me just out the slides here and we'll finish
194:38 with the last lecture nine prostate Okay, can you see this
195:01 Okay, yes, we can see . Okay, thank you. So
195:06 uh let's wrap this up again, lot of the stuff discussion we've had
195:13 these first two days is, is of out of context, right?
195:17 respect the faces and plays and things that. And it's gonna be the
195:22 here for the prostate classification scheme. already, I've already started using terms
195:27 bug and mold IQ. Alright, let me just formally classified this fabric
195:32 you. Okay, and I'm gonna it by taking you through this older
195:38 classification scheme that dates back to but it's still valid because the implication
195:44 these poor types, there are important for permeability associated with these poor
195:51 So this is sort of like the approach here. You have to ask
195:55 a couple of questions to use this scheme. And the first question is
196:00 the porosity? Primary or secondary. , Primary means that exist at the
196:06 of deposition. Secondary means is created dissolution. So it's die genetically
196:12 Okay, that's the first question, . The second question is the fabric
196:17 or not fabric selective. And what fabric selective mean? It means it's
196:21 back to de positional or digest And non fabric means I can't relate
196:27 to anything in the rock. so the non fabric stuff by definition
196:33 on the right and is all secondary terms of timing. Okay, Fractures
196:41 the role of fractures is not to a lot of ferocity. It doesn't
196:46 maybe increase your ferocity by one or at the most. So, when
196:51 talk about fractured carbonate reservoirs, that's misnomer because fractures don't add enough space
196:57 account for the production of the fractures, improve the permeability up to
197:02 times. Okay, that's the role fractures, fractures that get solution
197:07 It's called channel pores. Okay, never seen a channel poor, so
197:12 can't show you a picture. Channel to get solution large big enough for
197:17 person to walk into is called cavernous . Okay, and then there's this
197:23 buck the most misused term in carbon . I told you earlier that mud
197:29 call any funny shaped hole or That's not the definition there's no size
197:36 to a bug. So there could micro buggy proxy, there could be
197:41 buggy proxy leading the cavernous Prasit. . Okay. The definition of bug
197:47 secondary, but I can't relate it any deposition or digest fabric.
197:52 so I don't know what it relates , but it's not big enough for
197:56 person to walk into. Okay then here this is all fabric selective and
198:01 of this is primary inter particle between grains. Intra party intra particle within
198:08 fossil fragment. And then the next poor type would be finessed rel which
198:14 said often gets mischaracterized as buggy because funny shaped. But what was the
198:19 of financial prosperity really? The poor too big to be explained by the
198:26 of the grains. Something held open grain. That ferocity long enough to
198:33 be preserved. Okay, in other , is trapped gas trap air on
198:36 beach or trapped gas on the tidal . Do disintegration of organic material,
198:43 porosity, a big clamshell falls down the seat floor, you trap air
198:48 . That shelter process is not very . It's not very common. Usually
198:52 preserved, usually filled with cement. then for recall systems where you have
198:57 stones or what call a brownstone, ? Where stuff grows together. You
199:03 call this inter particle porosity between the corals or storm atop roids. But
199:08 people use the term growth framework for . Okay. And then to fabric
199:16 four types here that are secondary Baltic you reach out the grain and the
199:23 of the grain reflects the the whole the shape of the grain.
199:29 that's fabric selective secondary porosity. And inter crystalline is thrown into this category
199:36 . In other words, they're saying process is created by the inner growth
199:39 the dolomite crystals. I actually don't that's true. I think it's if
199:45 think back to our discussion, you start delaema ties in carbonate to
199:50 magical point. Right? What You reach out stuff between? So
199:56 wasn't created by the inner growth that created by removal of calcified material.
200:03 , So, but I'm not gonna this point because when people see porosity
200:08 dolomite crystals, they're gonna call that crystalline, but just appreciate that it's
200:12 due to the inner growth of the . It's due to removal of probably
200:17 material. Okay, Everybody appreciate the and I'm gonna go through and show
200:23 of this. Okay, And then see down on the bottom here,
200:26 are four types shrinkage cracks. They're fabric selected but their primary because they
200:33 basically send deposition early, but they across fabric on a tidal flat.
200:39 same with burrows. They cut through but their primary but they're not fabric
200:44 boring is primary but fabric selected, ? Individual grain being attacked by boring
200:51 . Again, burrow Prosky will preserve prostate can be preserved and never seen
200:56 cracks preserved in the subsurface. And Brescia. I've showed you Greta prostate
201:03 . Okay. The question is the right. Is it early formed or
201:07 it burial? That's the big Okay, so a lot of high
201:14 cartoons here to illustrate the relationship primary et inter particle prostate doesn't start off
201:21 the high grain stones. Don't start with the highest prostate but they start
201:25 with the highest permeability. Darcy scale . Okay. Usually that gets modified
201:31 some type of segmentation event. Whether it's early formed or burial.
201:39 . But that's primary inter particle process by calcite cement. That is not
201:46 crystalline ferocity here between this grain these because that was their first right modified
201:54 sanitation. So you don't call that all of this process in this
202:00 And with the exception of the moldy here at the northwest northeast northeast corner
202:05 is primary porosity. Okay. Inter and then molding. Sorry intra particle
202:15 the primary process that exists within the space of the skeleton, that's where
202:20 organism lived, then it dies and organic material disintegrates. So here's an
202:27 of a gaster pot again, all these holes would be primary intra particle
202:34 . Okay, modified a little bit cement but that's what existed at the
202:39 of deposition. Alright. Another example tabulate corals we talked about yesterday in
202:45 position, upright position. All that is primary prostate. E. Those
202:51 the subdivisions the horizontal subdivisions of the coral. Okay. And then growth
202:59 is applied to situations in the subsurface outcrop where you can demonstrate the reef
203:05 is created by institute corals or storm roids here, you can see an
203:10 growth. They intertwined, They preserved between some of that growth fabric.
203:17 can call that inter particle porosity, people will use the term growth framework
203:21 characterize that. Okay. And then pores? I said a clamshell falls
203:28 on the sea floor. Here's an from an outcrop and the price is
203:33 a big conch shell falls down on sea floor. That is shelter ferocity
203:39 usually gets filled in later with It's not connected to anything, so
203:44 not usually effective. Alright. And finessed reciprocity. Most finesse street tend
203:52 line up with horizontal orientation because they tied back to either general seaward dipping
204:01 on a beach where they're related to parallel lamination. Storm catalytic fabric right
204:08 to the to the uh the And when those organisms disintegrate, they
204:15 these horizontal pores. But sometimes that goes vertical. Like you see here
204:21 of gas escape effect. Right? the gas that was generated by the
204:26 of the organic material goes vertical. . And usually that's what happens on
204:33 tidal flat don't usually see that on beach, but the air will escape
204:37 the way to the top of the succession. All right. But there
204:41 only two environments where you can make preserve finessed ferocity. That's on these
204:47 flats with the crypt album or some fabric. Alright, So all these
204:52 holes you see here are primary finesse pores and most of them are
204:59 but you can see where some of go a little bit vertical.
205:03 again, this is not academic. stuff can entrap hydrocarbon. You're going
205:08 see this in some of our case later. And then the other environment
205:12 be the beach that we talked about we get the general seaward dipping
205:18 The breaking ways force air into that , sand. A lot of it
205:22 entrapped in the sediment and that's financial . All right. That is not
205:28 ferocity. Primary no dissolution involved And then the two fabrics selective but
205:37 poor types would be multi process et an individual grain gets fabric lee fabric
205:43 dissolved out. So the whole reflects shape of the precursor grain. When
205:49 walk out of the building today. at the building stone on campus,
205:55 . This is famous Tregoe Nia limestone was the type of clam shell and
206:04 gets leached out. Okay. And gastro pods that are associated with it
206:09 leeched out. So this is fabric but secondary holding ferocity. Okay,
206:17 that's a famous shell building stone. the all the shell buildings here in
206:21 are constructed with this limestone and here campus a lot of the buildings have
206:27 same rock. Okay, this is it looks like in thin section.
206:33 ferocity would be the leaching of the pod. Okay, and what would
206:38 cross dB That's not dissolution, That's intra particle. Right, That's where
206:49 gastro pod would have lived. so it's a mixture of molding and
206:56 primary inter particle. And really, know when you think about it,
207:01 best reservoirs in the subsurface are we a mixture of secondary porosity where the
207:07 get leeched out to variable degrees C mic, right envelope that goes around
207:12 grain and then primary porosity between the . That's inter particle that provides the
207:19 that provides the storage. That's these of rocks that make the best reservoirs
207:25 in the subsurface. Okay, Especially you have early cement or early dolomite
207:31 resist later compaction and preserve that Okay, so let me make a
207:38 about multi porosity here because sometimes molded occurs on a macro scale. Like
207:43 just saw where you remove most of grain, but sometimes the dissolution occurs
207:49 a micro scale, you create micro ferocity. Okay. And you can
207:55 of see a faint blue hue that through the zoo IDs and P
207:59 that is gas productive micro molding ferocity now, micro molding is not part
208:05 their classification scheme, but you want describe what this fabric is,
208:10 So we use the term micro molding . But here's the problem in the
208:15 . People see this porosity and they that is intra particle processes within the
208:24 . Right? And why is that ? Inter particle intra particle was
208:38 This is secondary dissolution. So you why you don't call it? The
208:43 is to recognize whether it's primary or . So this is not inter particle
208:48 , this is secondary micro multi Okay. And this is really important
208:55 a petro physical standpoint because if you off with a with a grain stone
209:03 with grains and porosity and initially right burial it's all filled with ferocity.
209:11 sorry, all the crosses filled with . Right? And you develop microprocessing
209:17 grains and you have inter particle process the grains. Alright, all of
209:24 process is going to be filled with . The grain, the microprocessor and
209:27 grains can be filled with water. inter particle process between the grains is
209:33 be filled with water right before the of hydrocarbons and the migration of the
209:40 . So then what happens after you up that micro porosity. Inter particle
209:46 poor system. Alright. You sweep oil in represented by the black,
209:53 water in the inter particle process is to be displaced by the hydrocarbon,
209:58 ? But you can't move that water the microprocessor because it's irreducible. The
210:04 force is so strong you can't sweep water out. Okay? So what
210:10 you end up with, you end with a grain stone that has oil
210:13 the inter particle, prostate the water the grain stones. And when you
210:18 your resistive the logs in the what are the recent activity logs going
210:23 respond to? They're going to respond the water in the who is your
210:29 Lloyd's? Right? They're going to up in that water and they're gonna
210:35 gonna read these really low resistive It okay. Which are going to lead
210:41 to calculate high water saturation. But famous examples in east texas that have
210:49 ferocity, they have microprocessor in the . It's have effective inter particle porosity
210:54 the grains that are saturated with The logs suggested these were all water
211:00 because of that microprocessing effect. But are the famous examples that produced oil
211:05 free Even though they calculated water saturation 60-80% 80% water saturation. Okay so
211:16 other words a lot of companies bypass reservoir because they thought they were water
211:22 but in fact they produce soil water . Okay so here's another well log
211:28 here that you need to be familiar . Right? When you're talking about
211:32 the logs because you know resist high . It ease occur when you pick
211:39 the oil. That low res activities when you respond to the water.
211:44 here's an example where the oil comes of this stuff water free because all
211:50 water stays behind in the micro Okay. And then inter crystalline
211:57 Again, when people see secondary process between the dolomite crystals, they're gonna
212:03 that inner crystalline. Here's an example a gas reservoir. Often nova Scotia
212:09 the Jurassic um Dulles stone fabric and the dolomite crystals. You can see
212:14 faded blue ferocity. That's what people gonna call inter crystalline ferocity. Okay
212:21 look what's happened to some of these crystals? They've actually been partially dissolved
212:26 . Okay. You see that? what would you call that partial dissolution
212:30 the dolomite crystal using Choquette. And , what would you have to call
212:38 fabric selective right individual dolomite crystals being out to varying degrees. What do
212:45 have to call it holding? Right ? Right, that's the only thing
212:56 can call it partial moment right sometimes we don't completely dissolve out these
213:02 . So people informally use the term multi porosity to characterize some of this
213:09 of the dolomite crystals. Okay up and look look what's around here,
213:17 stage calcite cement. Again, talking dolomite crystal dissolution. Well the common
213:23 here again is late stage cal Okay, calcium rich fluids.
213:29 And then doug no size connotation. the classical buggy process would be like
213:36 I showed you for the zebra where you reach out in this case
213:40 dolomite matrix to create these large holes cut across, deposition all fabric.
213:45 would be an example of buggy Okay. And then fractures most
213:52 as we've talked about line up with vertical orientation because your principal stress direction
213:57 from the top down. But I to the horizontal fractures that are tectonic
214:03 cross cutting fractures. Sometimes fractures get and they're curved like this. They're
214:10 contorted. That's a reflection of compression as well. So, sometimes we'll
214:15 that in these tectonic lee active right? Influenced by folding or influenced
214:21 strikes, slipper wrench faulting and then vertical fractures that gets solution enlarged.
214:29 be channel pores, but I have picture to show you and channel pores
214:34 bugs to get solution enlarged and are enough for a person to walk
214:41 Would be what we call cavernous Okay, all right, now,
214:50 of you may be familiar with some classification schemes or some earlier classification
214:58 Alright, there's a thing called the Crossing Classification scheme that was published in
215:03 50s, that shell used for a time and people actually still used today
215:09 Western Canada to characterize some of these fabrics. And so sometimes you'll see
215:16 terminology in the rock record or in literature. But the Archie Archie approach
215:25 is trying to get a better understanding permeability, which has implications for fluid
215:31 and resistive Itty response to the Itty logs. Okay. And what
215:37 they trying to describe? They're they're to describe the texture of the matrix
215:41 they're trying to describe visible pore So you will see people try to
215:49 the texture of the matrix Breakout. one, Type two, Type
215:55 Okay. And Type one would be visible ferocity. Okay. And so
216:03 I see this used in Western where there's a cottage community of people
216:08 photographers, where they go to the warehouse every day. And they look
216:12 cuttings because the cuttings have to be with the government to and they will
216:17 will go through these cuttings and try high grade the cuttings looking for areas
216:22 better porosity and permeability. And they'll this approach, right, No
216:28 chalky micro porosity. Okay. Or effective, bigger scale process. Either
216:34 particle or uh some type of interconnected porosity. Right. And so they
216:41 characterize that ferocity with this approach And this is this is how companies
216:47 Western Canada work. This is how high, great areas for prospecting
216:52 Once the photographers have done that, they'll they'll go back and start pulling
216:57 from those parts of the basin that migrated to try to see what the
217:02 and reservoir quality is. And that's a lot of people actually define prospects
217:07 Western Canada. Okay. They don't at it from the seismic. They
217:11 at it from the rock data. . And then probably more popular,
217:18 , certainly after the Choquette and pray scheme was a very loose a classification
217:25 that was published in the nineties. he's basically trying to do the same
217:29 . Right, Lucia worked for shell well. Right. So he was
217:33 with the Archie classification scheme and he to build on this and he came
217:39 it from the standpoint of these Okay, you can see the class
217:44 . Class two. Class three, what is class won its class one
217:49 has the better porosity and permeability. , grain stones with inter particle porosity
217:54 low, but pack stones, wood , inter particle proxy or coarser crystalline
218:01 stones with better permeability. That would class one. And then that would
218:06 class two would be the more muddier . And then class three would be
218:10 tighter stuff. Okay, and so how that's the approach that he tried
218:16 use, which is a good Right? You're trying to get a
218:19 on permeability. And so I'm going make a comment about this in a
218:25 about the application of this. And so you can, you can
218:31 how he tried to put this together a grain dominated fabric or a mud
218:35 fabric. Right? And he would the dolomite crystal size to the different
218:42 which you have to be careful Right? He assumed that the finer
218:46 would be associated with the muddier He assumed the course of crystals were
218:51 grain stone. That's not always the . Okay. And you can prove
218:55 now with the white paper and uh techniques. All right. But the
219:02 with jerry is that you went a further and he started he started to
219:08 any macro porosity of but how did prior defined bug a secondary poor
219:16 Right. Your respected that how it back to deposition, digest fabric.
219:22 so the problem with jerry is that took established poor types that we've already
219:31 right there already ingrained in literature and started calling them thugs right? And
219:37 called them separate bugs or he called touching books and you can see what
219:40 trying to do here. Right, gonna be low permeability, right?
219:44 it's separate, that's going to be permeability when it's touching. But he
219:49 have come up with his own terms . Right. So he's just confused
219:55 by doing this right? Because we already defined what fractures and Brescia prophecy
220:00 what molded prophecy is. And now calling all of this stuff lucky.
220:07 . And worse is he's asking you go from a to D. Observation
220:13 project into the rock to decide whether holes touch in three D. Or
220:19 . Okay so in the write up I gave you I made some comments
220:24 uh my experience uh I think this what I wrote up in the in
220:31 handout that I gave you right. got involved in a major study in
220:36 Middle East in the Permian. You have heard of the giant gas field
220:42 Northfield that occurs between Qatar and Alright in the Arabian gulf they share
220:50 gas field. Okay. And the part is part of a cutter.
220:56 when the Qataris opened up explorations for back in the mid two thousands they
221:02 all the western oil companies come in they told them that they had to
221:10 and core all of their expiration not just in the reservoir but the
221:15 permit. Okay so you're talking about to 1500 ft course. Okay.
221:24 then the Qatari government required that each take a sample every foot and do
221:32 and P analysis. Okay. And make a thin section and have somebody
221:38 the thin section. Okay. And you can see there were thousands of
221:42 sections that these companies had to generate document and I got to look at
221:47 lot of this stuff for one Okay I didn't look at all the
221:51 sections for their six or seven expiration wells. But I probably looked at
221:56 1000 thin sections from the Permian. . And then my client asked me
222:03 try to use jerry lucy's classification scheme they wanted to do a double blind
222:10 . Right? Because they'd already done process and permeability analysis on the core
222:16 . Right. And then we're making thin section off the edge of the
222:19 plug. So let's compare and let's how well lucius stuff works here.
222:24 , so we did a double blind for every thin section. I had
222:29 look at the thin section and judge pours are separate books, right?
222:35 his terminology, which pours were Right, come up with a classification
222:42 . And when we did that compared results. It was all over the
222:47 because it's almost impossible To know how stuff projects back into the rock three
222:54 . That's why we do plug analysis permeability. Right? It's very hard
223:00 work out. Perm from a thin . Okay. That's basically what I'm
223:04 because of the complexity of the Dia . Right? Some of these samples
223:08 limestone. Most of the Permian is . Some of it is just into
223:14 ferocity. Some of it is fabric ferocity. Some there's a dissolution
223:20 And then what complicates the whole story late stage and hydrates. They come
223:25 and plug that porosity variably. so just be careful of that.
223:32 then the last diagram is uh, , Illinois as a carbon a geologist
223:38 worked for statoil, who's now called . Okay. And Ecuador came up
223:43 statoil came up with their own classification . He complicated the story even more
223:49 thankfully this never caught on. but it's out in the literature.
223:54 some people, I'm sure that statoil use this terminology, but okay,
224:02 nothing wrong with the choke in praise . Okay. And you can see
224:06 some good implications, implications for permeability the choke it and pray. And
224:11 can see there's some problems with lucy's . Okay. But again, we
224:17 to always try to establish whether the ties back to something we can map
224:22 the subsurface. Right? That's usually all fabric. So that's always the
224:26 . Whether you work limestone, you all the stones. Okay.
224:33 So before we stop here, let just tell you, um, I'm
224:38 to uh send you something by I'm going to probably post some papers
224:44 relate to the stuff we talked about die genesis today. Okay. And
224:50 , you know, I, you , I know you don't have time
224:56 do a lot of reading here, especially if you're working full time,
225:01 try to scan some of those get a sense for for what the
225:05 of some of those papers are. then I'm gonna, I'm gonna send
225:09 some guidelines for the first quiz. ? I'll try to do that either
225:14 or monday. So I'll post that or send it to you directly by
225:19 . And then we'll have our first first thing next friday. So our
225:27 the quiz. Alright. And I to work out with Dr don about
225:31 much weight we give to these Okay. Because of the badge format
225:37 uh I'll let you know about that soon as I can. Okay.
225:42 . And then next week we're gonna into the second so called badge,
225:46 gets us into a discussion about carbonate and then how we translate this to
225:52 rock record. This gets us into discussion of carbonate sequences and de positional
225:57 city. And then we're gonna build that with the discussion about well,
226:01 and seismic data. Okay. Not pure geophysics of seismic but the application
226:07 seismic data To looking for porosity or . Looking for play types and things
226:12 that. Okay. And that'll be weekend. All right, so I'll
226:17 you guys. Next friday. One . Right. One o'clock to six
226:24 . Next friday. And then 8 5. Next saturday. Alright.
226:28 a good
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