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GEOL6363 Carbonate Sedimentalogy - Day2 08-28-2021-Part2 (Lectures 6 (from Freshwater Diagenesis) to Lecture 8 (Porosity) Recordings
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00:08 Okay, this is a continuation of six, starting with the second
00:15 uh digest environment that we call the water hygienic environment. And you can
00:23 from the schematic cartoon here that it near surface, uh not deeply
00:29 It's comprised of three hydrological systems. V. A dose in orange occurs
00:36 the water table, Only sees fresh when it rains and it percolates down
00:41 the 7th or water. And then blue is the main component that is
00:46 fresh water for addicts zone below the table. Always saturated sector freshwater and
00:53 there's a infamous mixing zone that occurs uh the marine environment and the freshwater
01:03 zone where you mix marine and And when we talk about models for
01:09 dolomite later today, you'll see a of people want to make it in
01:13 so called mixing zone. But in with the mixing zone represents is uh
01:19 especially on the landward side, is a continuation of the freshwater free attic
01:24 . With respect to die genetic processes products. So let's get right into
01:33 relationships associated with the freshwater diabetic Freshwater means drinkable water. Alright,
01:40 low salinity and low dissolved the solids under saturated with respect to calcium
01:50 So you can see where the most the die genetic alteration is going to
01:57 in the frantic zone below the water because it's always saturated with respect to
02:02 fresh water Nevada's own mostly sits high dry where the poor system is filled
02:09 air with a little bit of water by capillary action. So the processes
02:16 come into play for this diet, environment our dissolution And there are two
02:21 of dissolution here. On a finer . There's fabric selective dissolution where the
02:27 material dissolves out because it's unstable and respect to fresh water. But if
02:35 have longer term exposure you develop you develop vegetation where The vegetation can
02:42 create soil gas and increase the amount co two in the water. Then
02:47 can get hostal dissolution that we call . And this is leads obviously to
02:53 development of cave systems and the associated deposits in those cave systems. So
03:01 when you think about it, both these mechanisms are linked back to
03:07 Right? Neither fabric selective dissolution of scene that removes calcium carbonate has to
03:12 somewhere else. So it goes back the system as a precipitated calcite
03:20 So donna receptor die genesis and the with respect to the finer scale fabric
03:29 die genesis are now more stable. . Made calcite the crystals, the
03:34 are clear inclusion free. They're relatively crystalline. And by finally Kristen I'm
03:41 about tens of microns and hundreds of in terms of scale and they're mostly
03:48 dimensional calcite crystals with the similar lengthen although initially some of the cement start
03:55 with this study pointed doctors are like then evolved into course or of course
04:02 crystals. Right. The cal sites definition are pre compaction. All that
04:08 they start before the onset of pressure . And if you can put some
04:12 around these grains and freeze that then that's another way to impede later
04:18 die genesis. That's another classical way preserve reservoir quality long enough to entrap
04:23 hydrocarbons. So the key controls obviously you need an adequate time of exposure
04:31 fresh water, you need a rainy and you're not going to do a
04:36 of damage in an arid climate with little rainfall. Uh, you need
04:40 sediment that is highly uh magnetic, ? In order to respond because Lomax
04:48 will not dissolve in fresh water. buy fabric selector dissolution or will high
04:54 side. Okay. And then you recharge. Just like we talked about
04:58 marine sedimentation, you've got to bring literally thousands and thousands of poor volumes
05:03 fresh water in order to substantially alter of these sequences by fresh water.
05:10 there are a lot of ways to carbonate systems to fresh water.
05:15 you can have a major drop in level, right? Major low stand
05:20 sea level, but even during high or during rising sea level, if
05:25 carbonate production outpaces that sea level you can build local islands. And
05:31 it's Iranian of climate, you can rainfall. That's the upper example
05:36 And uh this is basically I showed that island right before lunch that had
05:41 beach rock. Well, that island a little fresh water lens to,
05:44 about five ft thick. And so not very big scale. It doesn't
05:49 very much right. It yo yo's and down Every 12 hours with the
05:54 exchange, So it only moves about ft up and down Every title
05:59 which is every 12 hours in the . All right, that's not a
06:04 of movement contrast that with the regional system where you have up dip recharge
06:10 then you move water down, dip a large area. Uh here in
06:14 U. S. We have a of big aquifer systems like that here
06:20 texas. We have the Edwards aquifer that recharges north of san Antonio and
06:25 that water flows down to san Antonio past san Antonio. And then we
06:30 a big floor. It we have big aquifer system in florida, the
06:33 aquifer starts in lake Lake Okeechobee and down uh through the Everglades toward Miami
06:41 goes offshore of Miami. He goes 50 miles offshore of Miami bubbles up
06:46 100 ft of water. So that's different kind of system in terms of
06:50 of water. That's a lot more and you would expect perhaps a lot
06:54 response to that moving freshwater compared to static system like you see here and
07:00 course we can accentuate this water movement tectonic lee uplifting some of these exposed
07:06 . Again, if you have you can again move this water well
07:10 offshore. Alright, so the discussion I want to have here is first
07:16 all, how do you know that carbonate rocks have been exposed summarily to
07:24 die genesis? And there are two to evaluate this. One is on
07:28 thin section level by looking at the of secondary porosity and in the
07:35 But on a bigger scale, there physical expressions of long term several exposure
07:40 should be present in the carbonate system be much better expression in a carbon
07:45 system that you ever get. And classics I think. And uh this
07:51 how you try to prove long term longer term. So, burial
07:55 All right, can you, the why I'm saying this is we're going
08:00 get into discussions sequences and cyclists it little bit in the sequence photography and
08:05 couple of weekends. And this is controversy right about whether these these systems
08:11 exposed to verily uh, Exxon model sequence photography is grounded in straddle geometries
08:18 seismic data and how they interpret what seismic geometries mean in terms of see
08:24 little fall and I'm gonna show you this course. If that's not good
08:29 and carbonates to prove several exposure. have to look at the Roc
08:34 So these are the kinds of things I would want to see uh demonstrated
08:39 these sequences to say definitively, they've severely exposed for relatively long period of
08:46 . So, Tower cursed the red rossa soils micro pressed on a finer
08:53 that covers more of the exposed limestone . The soil Crestor college E soil
08:59 , click the profile that I showed earlier in the sedimentary structures lecture.
09:05 then soil pies, lights that come with us. These are die genetic
09:12 , fabrics. Okay, not not . Alpizar lights, cavernous paparazzi.
09:18 I'm going to show you the cavernous by itself, doesn't mean anything in
09:22 of what kind of fluid went through rock in appreciation. And I'm going
09:26 show you also in this course, Brescia doesn't necessarily just mean exposure to
09:31 water. So to me, just you what some of these fabrics look
09:36 to get a feel for what I'm about. I mean, this is
09:40 area from south central china and This is the famous tower cursed
09:47 the li river runs through this part china. You can take a rafting
09:51 . Well, it's not even a trip. It's uh it's a you
09:55 a boat. Yeah, they actually you while you're while you're strolling through
10:01 Karst topography. But what you're looking in this photograph are um Mississippian Devonian
10:09 , lime stones have been some burial for about 600,000 years. And then
10:14 response is this tower Karst topography. of these peaks are up to 2000
10:19 above the river level. And then their number of major cave systems developed
10:25 , including the number of commercial Okay, so that's a physical expression
10:30 long term several exposure. Another classical would be the terra rossa soil.
10:36 see this example from the cretaceous in , the lighter colored limestone here,
10:42 exposure surface up here, you can the reddish soil profile. The
10:47 This is what you expect to get you have aerosol iron introduced into your
10:52 succession. So that's evidence of long several exposure. And then even in
10:59 caribbean and our places seeing successions, have place to see successions to go
11:05 to two million years. We've had four major up and down episodes of
11:09 level change every one of those uh stands a sea level results in shallow
11:16 carbonate deposition and every time we drop level, excuse me, have long
11:22 several exposure. And wherever you look the tops of these exposed surfaces,
11:28 is about 100,000 years of several You see the fine scale microcars developed
11:34 . So the microcar dissolution here is to not just the freshwater charged with
11:40 . Two, but uh also the of bacteria reworked the surface and some
11:44 the plants rework the surface and generate of the CO two charged or generate
11:51 gas that charges some of the water promote the dissolution. Alright, so
11:56 can see this irregular surface. This characteristic of all the lime stones in
12:00 caribbean. The benefits very exposed uh each low stand of sea level.
12:05 right. And then right below the is where you developed the so called
12:10 crete were so oppressed that I talked before. So I mentioned that this
12:14 a die genetic fabric. It looks de positional Mick. Right. But
12:18 has a reddish brown color again because the iron add mixed into it.
12:23 in thin section you can clearly see replacing the politic grain stone fabric.
12:29 , so it's fine scale dissolution re mechanism is relatively thin but it's dense
12:37 it occurs everywhere on top of these lime stones. So in the rock
12:43 it actually ends up being a permeability . As you'll see for some examples
12:47 gonna talk about later. And then that right above it or is the
12:52 where you get the soil pies These are concretions essentially where some of
12:56 political sand is dissolved sen trip italy from all edge and produces these golf
13:03 like features here with with a dark rim that looks just like this and
13:10 either that you would sand is still in the middle or it's actually dissolved
13:14 sort of like a geo that doesn't any cement on the insides.
13:19 so these are die genetic soil pies that form above the soil crust.
13:25 sometimes some of this gets reworked and re deposited. If you have any
13:29 topography, sometimes the pies the lights roll down the hill and re deposit
13:34 other place. But and then if breach this soil crust and you can
13:39 a joint here cutting through the soil crust. If you can bring fresh
13:45 further down into the exposed limestone surface you have time and recharge and you
13:51 the vegetation again. Playing a role to to to increase the acidity of
13:56 fluid. Then you can develop the uh Carson related fabric which is first
14:03 cave systems like you see here both of these are examples of cave
14:08 developed in rock that's about 100,000 years . And you know, caves are
14:14 just big holes. Right? That a person can walk into it.
14:20 the definition of cavernous ferocity. But also backfill those holes. Right?
14:26 dissolved carbon a material will locally re as poor filling cement. Well,
14:32 is the cement? It's a stalactites stalagmites. It's a flow stone that
14:37 along the the edges of the of cave. All right. And so
14:42 donor receptor Dia genesis But on a scale. All right. So these
14:48 physical expressions All right. And then what will happen to the roots of
14:52 caves? They will collapse and then get the classical solution collapse, Brett
14:58 like I showed a picture of All right, again, uh The
15:04 is the host tool of the grain and now the reddish the critic material
15:09 acting as a cement to buy this together. of course this is probably
15:16 one fabric that people rely on in rock record to interpret karst in older
15:23 or Dulles stone sequences. Okay, Now what you need to appreciate and
15:31 only get this by doing field work the in the pleistocene of the caribbean
15:36 that these cave systems are not just giant hole that goes forever.
15:41 Everything is controlled by topography. They about ridge and valley topography on these
15:46 , right? The ridges are de ridges and then low areas in between
15:50 valleys and it's the valleys where you the fresh water and And so you
15:57 get cave systems everywhere. You get cave systems distributed along a regional jointer
16:03 system. But there might be a system over here and then you might
16:06 several kilometres before there's another cave Okay, so not the whole place
16:12 seen sequences undergoing Kearse ification. Most the places seen uh is undergoing what
16:19 call fabric selective dissolution where the individual grains dissolve out when exposed to fresh
16:27 . They create the secondary pores that see in this diagram here.
16:31 And we call that molding ferocity. then what happens to that leached calcium
16:37 goes back in a solution and locally precipitates within that rock as poor
16:44 but stable, Low mag calcite Mostly that echo dimensional calcite that I've
16:49 about. Okay, now I can't to you that you leech right here
16:55 re precipitate right next door. But will prove to you in a minute
16:59 this dissolved carbonate doesn't travel more than or 15 cm before locally re
17:05 So it really is local donor receptor genesis. Okay, and you can
17:11 what we're doing here. We're doing we call Parisian version. We're going
17:15 a high porosity, high permeability grain , to a high porosity, low
17:22 grain stone. Right. And what the mud loggers call this fabric?
17:26 call it heartbreak ferocity. Right. ferocity. No permeability. Not going
17:32 yield any hydrocarbon. Okay, so is your first introduction to the,
17:38 a uh to the caveats about interpreting off of well, logs off the
17:45 logs, it's not enough to know have high porosity, You need to
17:49 what the permeability is too. And you can't get that off of
17:54 off of these processes logs. And , you can have their carbonate reservoirs
18:00 have overall relatively lower bulk ferocity, still produce hydrocarbon because they have associated
18:07 permeability, right? Whatever the cause that is. So that's a lesson
18:12 be learned about using logs for processing . Alright. Yeah. So here's
18:19 country rock and the caribbean that occurs those the cave systems that I just
18:24 you the country rock Hewlett gravestones undergoing selective dissolution. The regulated goods and
18:31 lloyds are being variably dissolved out. is all a reaganite dominated sediment to
18:37 with. It's now there's not an of a reaganite left in the
18:41 Everything has been converted to low mag side and the cement are all mad
18:46 . Alright, sort of classical porosity . So having said that, let's
18:53 down to a finer scale and talk the cement fabrics and and look at
18:58 they differ between the videos and the . And uh fly this back to
19:04 rock record. All right. Remember video zone sits above the fresh water
19:11 , right? Only sees water when rains and the water passes through.
19:16 most of the time in the vato system is unfilled with water. The
19:20 water this air is water trapped at of contact or on the undersides of
19:25 of these grains. And so that's you focus your segmentation. All right
19:31 you start to dissolve some of these , you start to re precipitate that
19:36 at points of contact or as gravitational . Look at the scale of these
19:42 , their tiny, there are tens microns across for scale and some of
19:47 so called meniscus cements occurred points of where the calcite cement has a curvature
19:55 it. So where does that And this has come from? If
19:58 remember Chemistry one On 1, you the test tube with water. And
20:04 do you get right at the You get a curvature of that water
20:07 the capillary force on the edges. , that's exactly what happens here with
20:12 with the water that leads to cement and the cement takes on that same
20:17 . Okay, so that's the vague not a lot of dissolution. Not
20:22 lot of segmentation because the two are together. More of the damage is
20:26 in the forensic zone. And more the grains dissolve out here. I'm
20:31 showing them dissolved here, but they dissolve out. And what precipitates first
20:37 a poor filling cement, his alpacas bladed lome calcite crystals. Then
20:44 crystals start to grow out into the four system. A few larger crystals
20:49 out, but they evolved into an morphology. And so this classical Aisa
20:55 bladed to equine mosaic. Mhm. always attributed to the fresh water for
21:02 zone. All right. Again, dissolution is driven by fresh water.
21:08 reacting with a reaganite and the cement coming from the dissolved or a genetic
21:13 . Okay. And so most of cement send up with the secret service
21:19 called the spurring blocky morphology. basically the you can see the dimensions
21:27 for the crystals. All right now one unique type of calcite crystal that
21:33 in this die genetic environment called a real, moreover, gross cement.
21:40 And this occurs whenever are fragments that present in this. Greenstone are a
21:46 of germ related. Remember the kind different pieces were all one single crystal
21:51 calcium carbonate. So any dissolved carbonate the in the water is going to
21:56 to jump on these single crystals of oid zork, retinoids, whatever is
22:01 the system. And very quickly grow that as an overgrowth. An optical
22:08 with the host crystal. So these can get really big. You can
22:13 the scale here, millimeter scale. right, so this is unique in
22:17 of the size of the crystals because the crystals are tiny. But this
22:22 the first environment where you can get in textual over gross cement developed if
22:27 have Quran oid host or a kind term host nuclear it on. And
22:32 show you what these look like in minute. Okay, so let's look
22:36 some examples. This is a thin from the top Of that island.
22:42 showed you before lunch for the head the beach rock, 500 year old
22:47 . So, you know, it's explosive to fresh water for 500 years
22:53 roughly. And you can see the sound there is a little bit of
22:59 . Okay, you can see some the dissolving Iraq genetic material. And
23:03 , correspondingly you see a little bit calcite cement. Where is it?
23:07 focuses mostly focused the points of contact some of those crystals show that
23:12 That's that Meniscus cement fabric. so you're not going to do a
23:16 of damage in the fresh water Vegas unless you have long term several
23:24 Okay, because you don't have enough movement through the system to do a
23:29 of damage. So, going back this sample, I just showed you
23:33 is a That was vetoes, Die two. But for 100,000 years.
23:40 , so you see how the time works in helps you write more and
23:43 fresh water, more dissolution, More . But this is, you
23:49 less than 500 years of freshwater dissolution . Most of the damage is done
23:58 the free zone below the water And the first phases cement that develops
24:04 eyes. A pakis, stubby bladed calcite crystals. Okay, let's back
24:11 on this photograph and you can see ice. A packers crystals great end
24:16 slightly coarser equity mosaic, calcite crystals the centers of pores. So that
24:22 for my cPAc is bladed to equal . That's considered again to be classical
24:29 fanatic die genesis. Alright again, are these cements coming from? They're
24:34 from dissolution of the Iraqi genetic So this is hala meter. You
24:38 all these Alamitos Alameda. Remember Those are magnetic. And what else
24:44 there a genetic in this rock? a coral here. They're mollusk.
24:48 are all the sources of material to dissolved out. That provide the cement
24:53 the for this fabric that you see . Okay, so you're going to
24:58 a lot more damage in a frantic for a given period of time than
25:02 ever would do in the video sound . Okay, yeah, Secret Isil
25:13 . Nice. Sifakis nice to practice it goes all the way around the
25:18 with the uniform thickness except where the were touching. All right.
25:24 if you see the grains touching like here, obviously you can't form cement
25:29 there where they're touching. But it everywhere else that goes around completely around
25:34 grain. And that's to be expected . If the whole poor system is
25:38 with water, unless there's some way inhibit segmentation here, you expect it
25:43 be uniformly distributed all the way around grains. Okay, yeah,
25:55 Sequent mosaic. That would be the that occurs in the centers of the
26:03 between these grains as you make a from the ice pack is bladed,
26:09 will go up to where the black point. That would be the transition
26:13 equal mosaic. So all the crystals off is isil pakis, little bladed
26:19 and they all start growing out in open pore system, but only a
26:22 bigger crystals survive. And they evolve that equal morphology and that's what we
26:29 time and time again and all of modern day or replace the scene,
26:34 periodic systems. Okay. Yeah. here's the ancient analog Jurassic smack
26:43 Um I don't know if this is Arkansas is probably southern Arkansas. The
26:50 is buried several 1000 ft. And do you notice here? You notice
26:56 grain stone fabric? There's no mud system, these were dudes and
27:00 Lloyds. And what got selectively dissolved the U. S. And
27:04 Lloyd's. Right, so the inference that these were magnetic boots and
27:08 Lloyds. They got fabric selectively dissolved . And then what do we put
27:14 these grains? We put around first ice, a pack, a stubby
27:19 calcite crystals, right, white color what we call clear, right,
27:27 , no inclusions. And then see it grades into a slightly coarser equal
27:33 . But again, these crystals are that big. I mean, look
27:35 the scale bar here, That's 300 . I said, these are tens
27:39 microns to a few 100 microns across scale. They don't get very big
27:44 they latch onto those kind of terms they have space to grow bigger overgrowth
27:51 . Okay. And you see how the ice a pack of cements go
27:57 the way around the grains except where touching. Well, what does that
28:01 ? That means these cements are pre , their pre pressure solution.
28:06 This sample is not deep enough for solution But I have other samples in
28:10 smack over from 9000 ft of burial are more than deep enough for pressure
28:15 and they look just like this. so the implication is that these early
28:20 cements, just like the early marine we talked about before, create a
28:25 framework that resists later pressure solution. if you can hold on to enough
28:30 this primary porosity, then you have for good reservoir development. Okay
28:39 All right. Let me show you the syntax real uh calcite cements look
28:44 . But I'll do that by showing an example from the Mississippi in the
28:49 is a major geological time period with of Quran lloyds and you can see
28:54 pieces of criminal, it's all through and here's a Quran oid in the
28:59 with a cement around it. And is one of those overgrowth calcite
29:04 And you prove it by going to Nichols, which we're at right
29:08 But then you rotate the stage 90° you see how the overlying cal side
29:14 black at the same time. The crystal of kind of during goes
29:20 That optical continuity. That means they an optical continuity. That's the definition
29:25 overgrowth syntax real cement. Okay, expect to see this a lot in
29:31 criminal little rich or a kind of rich deposits. Okay, They're always
29:36 to attract that cement first because it's for for count side to precipitate on
29:43 single crystal of of the That makes the cry annoyed. Okay, so
29:49 appreciate that's that's what the syntax real look like. And that's how we
29:53 them in the rock. All right , I mentioned re crystallization as part
29:59 the freshwater diet. Next story. And I've said now that re crystallization
30:05 involve two different uh processes. One to change the mineralogy to go from
30:12 reaganite to Lomax calcite. And the way is to do what to change
30:17 fabric and sometimes you do both So, here's an example fred,
30:23 place is seen of a magnetic mollusc . This is uh you probably heard
30:29 the uh the big strong the shells people eat right for for Mhm.
30:43 mind's gone blank here. Um I'll of it a minute. Anyway,
30:47 are regulated shells. All right. these shells were uh the question here
30:55 we see the sparkle side. so uh the question is, what
31:00 the sparkles I represent? Is it pour filling cement, which means that
31:06 dissolved out on a big scale. of that shell. And then we
31:10 it back in with cement. Or this a re crystallized fabric where the
31:15 Alice. I just replaced some of Iraq genetic of coral. It's
31:21 sorry. So if that's the case it is a change in meteorology and
31:26 also a change in the texture. , so conch fritters. Right.
31:37 you ever had conch fritters? You concrete. So if conquer is a
31:41 big mollusc shell that they they farm the caribbean and they pulled the muscle
31:46 and that's what they eat. Really . Right, cracked conch khan
31:53 Yeah, if you go to the you'll have to have it next time
31:57 go. Okay, so these are shells basically regulated. So the answer
32:04 that this is a re crystallization effect you see the growth lines of the
32:11 are preserved in the calcite. See you wouldn't do that if you dissolved
32:17 the entire whole right? So this re crystallization on a fine scale,
32:26 changing the mineralogy but you're also changing texture from the original regulated micro structure
32:31 these more equal dimensional low magnesium calcite . Okay, that's re crystallization and
32:39 can see the problem with re crystallization there's no porosity story really developed
32:45 But what are you doing? You're the deposition of fabric. Right.
32:48 masking some of the deposition of fabric here's a good example of that from
32:54 Jurassic sequence in the North sea. sorry in the english channel? Uh
33:00 are thin section. this is a section of some well cuttings from a
33:05 in the english channel. And you see this is all limestone. All
33:11 . And you can see the once the skull of rain here in the
33:17 . Little benthic foraminifera still visible. see the darker MMA critic fabric.
33:22 then you see a lot of the calcite, right? The secret dimensional
33:27 . This randomly distributed all through So, the question is, what's
33:32 on, right? Is that is calcite pour filling cement? In other
33:36 that we leach out some of the and Mick. Right. And then
33:40 filled them with port filling cement. is this a re crystallization effect.
33:45 again, historically it's been very difficult answer this question. But one of
33:49 ways we try to answer it is the fluorescent microscope. So, remember
33:55 you this yesterday. And so this is taken with the blue fluorescent
34:01 The microscope attachment on a regular Petra graphic microscope. All right.
34:07 is the benthic foraminifera. All Still preserved. But then look,
34:15 you pick up the matrix? All . Let me go back. I
34:18 think you see any of those grains than this brain in this view.
34:23 then here's the view with the fluorescent . What is it picking up?
34:27 picking up foods and p lloyds. can see preserve coatings around the edges
34:32 a number of these grains. so this is re crystallization that actually
34:38 some of the deposition of fabric. now this is important because it helps
34:43 to see what's your deposition. All is right. You've got loads and
34:47 . Right? Well, this is a factory for making new is
34:52 That's low energy. So that implies somewhere nearby there was an active with
34:58 body system and some of those dudes shut off into the more stable part
35:02 the environment. So this is the equivalent to the act of shoal.
35:08 it changes your understanding of the regional geography, right? If you can
35:12 something like that. But again, you look at the this view,
35:16 no way you would know that that uh would bearing. Okay, so
35:22 really crystallization. Okay, let's finish , let me summarize the freshwater dia
35:28 . We have the two diabetic whereas most of the damage done as
35:32 expect. It's done in the fresh for addicts zone, major dissolution,
35:37 segmentation, major porosity modification, leading that process. The inversion that we
35:42 about. And so almost always what's to happen in your rocks, the
35:49 is going to be lowered, Because you're filling, you're filling the
35:53 throats associate with the primary porosity. choking off those pore throats and reducing
35:59 . Alright. And that's important to all right, because the older
36:08 Older literature being back in the 60s, early 70s, uh made
36:13 big point about freshwater die genesis. . Go find carbonates are just some
36:17 exposed and you'll find ferocity. yeah, you might find ferocity,
36:22 it might not have any permeability and a has sort of been proven out
36:28 with the subsequent research, right? these exposure surfaces or while they may
36:35 some secondary process, they're not always productive secondary porosity. Okay, and
36:43 appreciate that. What I've tried to here is that the, the response
36:49 these carbonates to exposure to fresh water pretty quick, right happens pretty
36:54 Doesn't take long for these trucks to reacting and generating poor filling cement.
37:01 uh, how quick that is. , we can demonstrate that with an
37:05 from the, from the northern Uh this is the area that I
37:13 , I work for my masters where showed you the shuttle photograph yesterday.
37:17 is that you would sand body This is the island next to that
37:24 two or 3 km away from that . I just showed you that had
37:27 beach rock and this is a Luther . And this is a peninsula on
37:32 island that used to have a resort of course the resort was built on
37:37 wrong side of the island. And their beaches would wash away every winter
37:42 winter storms. And so they were for ways to replenish their beach.
37:46 also had a golf course and they Sand for their for their traps on
37:51 golf course? And so what they in 1972 when they were building this
37:57 , as they went offshore and they up the offshore analytics sand. And
38:02 what you're looking at here. A of modern politics sand that was taken
38:06 from under water and several exposed in 72. Okay. And then I
38:14 this photograph in 1980, In less 10 years. The entire surface of
38:20 exposed sand body is completely case hardened dissolution cement. Ation. It's a
38:27 hard surface. Okay. And so tells you how quickly this stuff stabilizes
38:33 segmentation. And then What's the extent dissolution? Segmentation is just the upper
38:39 or 20 cm of the sand So this tells you when the fresh
38:44 hits the top of the sand body reacting. It doesn't travel very far
38:49 it re precipitates poor filling calcite cement all the rest of the sand body
38:55 completely and cemented. Once you dig the rebel blocks that fell down,
39:01 all in cemented. Okay, so see a reference to the paper here
39:09 posted, I don't know if you , but I posted a bunch of
39:12 on blackboard yesterday that uh are related our diet genesis discussions today and other
39:20 that are related to the deposition? story That I'm going to develop over
39:24 next weekend or two. Okay. right. What if this is a
39:33 court sand? It would still be pile of unconsolidated court sand.
39:38 This is the difference between carbons and and this is why in the world
39:43 carbonates, unlike plastics, most of shedding of carbonate material is not during
39:50 stands and several exposure is during high . Okay. So I think most
39:56 you would agree the norm for classic is that we shed most of our
40:01 grain classics during low stands when sea drops below the so called shelf
40:07 All right. Although you can still high standard shedding that's happening today off
40:12 California and you know in san Diego canyon. But the norm contrary to
40:20 Exxon sequence strata graphic model says the for carbonates is just the opposite.
40:25 don't shut a lot of material during stance because that's what happens. What
40:30 when I just showed you is what to these carbonates, right? They
40:33 up? They freeze up. They be blown around anymore. They're frozen
40:38 . So the only way you can during a low stand is to erode
40:41 of that cemented rock along the Okay, But that's what you want
40:46 be shedding in a carbonate system is sand out into the basin.
40:52 To get a good on laughing wedge has hydrocarbon potential hydrocarbon productivity. All
41:00 . That's going to happen during the stance when you're carbonate platform is
41:05 your carbon a machine is going full . That's when things like hurricanes and
41:10 , presumably things like that, take of that material and shut it out
41:15 deeper water. Okay, so this a major difference between carbonates and plastics
41:22 Exxon failed to recognize that. All , if you look at their model
41:27 carbonates and classics terms of sequence they argue in both cases, drops
41:32 sea level are the principal ties for material, even though they knew
41:39 even though they were told that wasn't , that there are major differences.
41:44 was already literature to show that you have to understand how big corporations work
41:49 the politics that take over right? wanted to solve encompassing model that applied
41:54 to carbonate sand classics that was tied to sea level and straddle geometries.
42:02 right, that's freshwater die genesis. , let me finish up by throwing
42:07 wrench in this whole discussion by showing another way two ah, dissolve a
42:16 and potentially create processing version, but it without exposure to fresh water.
42:23 , and the mechanism is called marine die genesis. Alright, so when
42:31 go back to the marine traumatic but you look at Stuff that's buried
42:37 about a 100 To less than a m where the poor food is still
42:44 . Okay, it's possible in those burial settings for that reaganite to dissolve
42:51 re crystallize. Okay. And the is what drives that, right?
42:57 that could be just increasing heat because it becomes more unstable with increasing
43:04 but it could be due to some processes that I've listed on. I
43:07 the next slide. Okay, so want you to appreciate this is another
43:12 to create secondary porosity. That has to do with fresh water.
43:18 and here's the summary of the Right? So, shallow burial
43:24 it's before the onset of pressure which I'm going to define In a
43:29 is roughly a 1000 m. All . The dye genesis occurs in the
43:35 of seawater marine fluid. It leaches , fabric selectively. A reaganite
43:42 the secondary porosity generates the pre compaction cements the look almost identical to what
43:48 just showed you for freshwater die Okay. And then these are some
43:53 the uh mechanisms that might be driving dragon eye dissolution that have been offered
44:00 the, in the literature. So, let me just show you
44:04 case study. All right. This study comes from the northern Bahamas city
44:10 Miami would be right here. And can see the this is part of
44:16 we call great bahama Bank and back the mid 19 eighties, Western geophysics
44:21 a number of seismic lines across parts this platform and you can see one
44:26 the seismic lines underneath and you can these off flapping straddle geometries here that
44:31 the interest of the University of Miami out of florida, the research group
44:39 they raised about $1 million dollars and a Mississippi River barge type drilling rig
44:48 to the Bahamas and they drilled to cord wells, Uganda and klein Oh
44:55 . And you can see how far they went. Good core recovery and
45:00 thing uh that they didn't see was solution. So neither of these wells
45:06 deep enough for pressure solution. And most of this material, and
45:12 see why next weekend, when I you through the modern most of this
45:17 that makes makes up the kind of that come off of that platform.
45:20 the to the east is fine grained materials. Shut off by the day
45:25 day, weak easterly trade winds that by coarser grain material that comes off
45:31 major storm activity. And when they at the coarser grain fabric, the
45:37 stone fabric, they saw this relationship saw sometimes the regulated grains dissolved out
45:45 to give you secondary multi ferocity. then you can see the placement of
45:48 pre compaction cements. Sometimes some of secondary pores were filled in with calcite
45:56 or just re crystallized directly to sparring . But the point is that this
46:00 early pre compaction digested digested die genesis mimics the fresh water fabrics that I
46:09 showed you. But when they analyzed cement biochemically no evidence of the involvement
46:14 fresh water. So fresh water these unique geochemical imprints from uh from
46:21 stable isotope uh trace element point of . Okay, so nobody appreciate what
46:28 saying here. This is second way make secondary process has nothing to do
46:33 exposure to fresh water. It's driven marine fluids during shallow burial. Before
46:39 onset of pressure solution. It generates compaction cal sites that are gonna preserve
46:45 at death. Okay, so here's application. This is a one of
46:51 Permian debris flows. I showed you core this morning with the sedimentary
46:57 Well, within those sedimentary brunches are carbonate grain stones that are made up
47:03 the fabric that looks like this. are druids and some skeletal material and
47:07 lloyds. And you can see we're , almost 6000 ft of burial.
47:14 this is reservoir rock out in the of the midland basin. So these
47:20 and those branches that I just showed are actually in case the non cal
47:24 black shale. Okay, yet they this kind of die genesis. And
47:29 how did people always interpret this kind die genesis? Oh, that's freshwater
47:34 genesis. Look at the secondary Look at the early cements, but
47:39 never made any sense. Right, the setting you're out in the middle
47:43 the midland basin, how would you get fresh water out there? Much
47:47 out between the black shell? See I'm saying? So this bothered a
47:52 of us for a long period of , until this marine barrel die genesis
47:56 was published about 20 years ago. right. So, I think the
48:02 explanation for this fabric is marine barrel genesis were out in the middle of
48:07 and just during shallow burial, the agonize starts to go to give you
48:11 secondary process to generate the pre compaction and uh, and you can preserve
48:18 that way because you've got enough primary preserved to have good permeability.
48:23 and, and this does produce All right, Everybody understand that.
48:30 the second way. And I'm gonna you a third way to make secondary
48:34 . So, you see the problem in the old literature, as soon
48:37 , as soon as somebody saw a porosity, they immediately related to freshwater
48:41 genesis. And you couldn't fault them doing that because that was the only
48:46 back then, we knew how to secondary porosity, but sometimes it wasn't
48:51 by the other fabrics and the And uh, so this is nice
48:56 have this second mechanism. Okay, , The last, the last
49:01 last three slides here, therefore slides are have to do with the role
49:07 climate and driving freshwater die genesis. want you to appreciate how quickly these
49:13 belts change and what effect they have the rocks. Okay, so this
49:21 came out of a big a PG conference back in the nineties,
49:26 things held up in colorado. And , the purpose of the meeting was
49:32 . First was to evaluate Exxon sigma graphic model where they claim that you
49:37 find the un conformity is off of straddle geometries, you'll find reservoirs.
49:43 . And then the second part of meeting was to evaluate, well what
49:46 comes into play for freshwater die Okay. And so what came out
49:51 that meeting was uh, some listing all the controls that are important in
49:57 freshwater die genesis. And what's the one control of the key control of
50:01 ? Right. And then the second control, it holds everything together is
50:06 of several exposure. Right? If stuff never gets a barrel exposed or
50:11 period of time involved in exposure, you're not going to do a lot
50:15 freshwater die genesis. Okay, I want to play up this influence
50:20 the climate by taking you and showing two parts of the Bahamas that are
50:26 two different climatic belts today. so here's a, Here's the map
50:32 the Bahama five Foreign Complex. The line. I just showed you that
50:37 worked out the marine barrel died genesis is right here on this part of
50:41 great bomb a bank, here's the that I worked for. My master's
50:45 bank and right next to it is Luther island that I alluded to on
50:50 shuttle photograph. And the rocks that up The upper flies to seeing rocks
50:56 are 100,000 years old, Right? their five day meters above present a
51:03 level because that's where the high stand sea level was that back and then
51:08 sea level went down. Never came up tire than it is today,
51:13 . All right. And then I'm show you rock from there. Then
51:17 going to contrast it with rock from platform, same age rock. All
51:22 . And we'll look at the prostate to digest alteration. What are we
51:27 ? We're going from about 25° north the equator, which is in the
51:34 , general easterly trade wind belt. is also the humid part of the
51:38 platform complex. There's no, they 80,220 cm of rainfall a year.
51:44 no evidence of evaporates up here in north. Then I'm going to take
51:48 down here to keiko's platform in West island. West Caicos Island gets 10
51:52 20 cm of rainfall a year at most. So, it's by definition
51:57 semi arid. Okay, so here's northern Bahamas example. I've actually already
52:02 this to you. This is that that had complete frosting version. Not
52:08 ounce of Aragon I left in Okay, sort of makes sense.
52:13 . If you're an Iranian climate and here's the cake. For example,
52:17 age deposits, same sea level Look at look at the complete difference
52:23 . The utes are still preserved. still are magnetic, 90, of
52:27 rocks are still a reaganite. This very unusual for several exposed carbonates.
52:33 , but it reflects the drier climate you can see there's a little bit
52:38 dissolution here. You've got to look and and correspondingly there's a little bit
52:43 calcite cement. But what's the what's only difference here between these two
52:48 It's a climatic belt. Right, in the north and then semi retired
52:53 the south and their evaporates forming on platform. So that's a reflection of
52:58 different climate as well. So, , how quickly is that? Climatic
53:02 changing is changing over about three to of latitude. It'll change which is
53:07 400 450 miles distance. Okay. questions about the freshwater die genesis or
53:20 um marine burial? Yes. Why don't we take uh, why
53:28 we take our 15 minute break. , let's finish up our discussion by
53:37 about the last limestone, die genetic . This is the so called deep
53:44 die genetic environment. And again with barrel means or barrel die genesis means
53:53 die genesis coincident with or post stating start of pressure solution. All
54:00 So the debate and the carbonate community how deep do you have to be
54:04 initiate pressure solution and I'll address that a minute. Okay. But you
54:10 see the uncertainty here has always been by these diagrams. You see the
54:14 lines here. Nobody knows exactly how you have to be too to start
54:19 barrel die genesis. All right. obviously this is the least understood of
54:25 three diabetic environments out of sight, of mind. Right. You have
54:29 have subsurface databases in order to understand . And the problem has been that
54:36 industry, you know, collects the . Industry is basically disbanded.
54:43 their research companies. Right. Nobody's research. And these oil companies on
54:50 die genesis and carbonates about the only that's really being studied in detail is
54:56 Canada. And the reason for that the Canadian provinces like uh Alberta and
55:04 , Manitoba. All of these provinces the company core data to be archived
55:10 the government. So the government gets the core gets a copy of the
55:15 logs, gets the cutting, had of the cuttings data and all of
55:18 data after a certain time period becomes available for study. So all of
55:23 progress I think in the last 30 has really come out of Western Canada
55:29 of their accesses to these databases. , here in the US. The
55:34 is that most states don't require archiving the subsurface databases. Right? Companies
55:41 share data easily. And it's very to to get access to some of
55:47 uh subsurface databases. All right, let me share with you what I
55:51 is our best knowledge of uh the called deep barrel die genetic environment.
56:00 obviously we're in an environment now where temperature and pressure comes into play.
56:05 the press the processes that operate here going to be pressure dissolution.
56:11 And then what comes along with that ? Ation? Right, Because this
56:14 another expression of donor receptor die And what is the what are the
56:20 ? Now? There's still a low cal sites and they're still clear.
56:24 they're relatively core sequence cements. And course, I mean, hundreds of
56:29 , two millim scale, Not the of microns to a few 100
56:34 Mhm scale cement, like we talked for fresh water or marine barrel die
56:40 , Right. And then what's the process that can operate in this
56:45 If you if you generate the right of acidic fluid, you can get
56:49 dissolution. And now this dissolution attacks siddiq material. Because by this
56:55 all the reaganite and high medical side been stabilized. Okay. And so
57:00 is now low magical side in the . And if it sees the right
57:05 of acidic fluid, then you can barreled dissolution. So that's the third
57:09 to make secondary porosity. So, the critical controls our depth of
57:15 the pre compaction cement or another They can inhibit pressure solution. If
57:22 can put those icy packers cement surround grain. What's another way to preserve
57:27 depth, overpressure or geo pressure here right over pressuring you do this by
57:35 re deposition from one environment to You rapidly bury the carbonates and you
57:41 pore fluid in those rapidly buried carbonates poor pressure becomes higher than the overburden
57:47 . That basically shuts down your pressure . Okay. Right. And then
57:53 other control might be what's happening to nearby source rocks. If you're starting
58:00 crack off gas species like CO two H two S, then that becomes
58:06 way to create acidic fluids that could burial this solution. Okay, so
58:12 expressions of pressure solution that you would if you don't know anything about the
58:16 history of Iraq, if you see lights or green to green soup tureen
58:22 whiskey micro stylists in your lime you know you have been buried deep
58:27 to get pressure solution. So the again is the minimum barrelled up to
58:33 pressure solution. All right, so me share with you the only case
58:40 that still exists that proves the timing pressure solution. Alright? You can
58:46 to the literature and you can find from outcrops. Studies claiming that pressure
58:52 starts after tens of meters of They will go to an outcrop and
58:57 go down from the top of the . They'll go down 2030 m and
59:01 find style lights and they'll say, only took 30 m of burial to
59:06 a style light. And then you them, well, what was on
59:10 of the Ankara? I don't They don't know how much material has
59:16 stripped off. They don't know, there was a mile thick ice sheet
59:19 top of it that melted during the glaciation. You know, you see
59:24 problems here, nobody absolutely knows the depth of these outcrops to to know
59:29 much material was there to initiate pressure . So the only case study that
59:36 know of in the literature is this from the deep sea drilling project in
59:40 Western pacific. Excuse me. And you know anything about the ocean drilling
59:51 , um what they do is a from the set of water interface all
59:55 way down to their target. And so when they decide on a
59:59 site, they drill until they get their target. They pull the core
60:05 the first thing they do when they the core is they do bios treaty
60:09 , they want to know the they want to know what missing sections
60:13 , are gone. They want to if there's any breaks in deposition.
60:18 . And so they did that for for this area in western pacific no
60:23 section, right. Complete succession of to uh place the scene age
60:32 All right. So these are he's are there's no breaking deposition here.
60:40 right. And so look where the solution comes in. The first expression
60:45 pressure solution. These little vague wispy . And there's some controversy about whether
60:51 really precious solution or some type of compaction, But that occurs at about
60:56 m of burial. Okay. And good style lights that have any kind
61:00 amplitude where you could easily see him your eyeball in the core Really don't
61:05 until after about 1100 meters of So I'm willing to give you 800
61:11 . I'm not willing to give you of meters of burial to say that's
61:15 for pressure solution. I just showed a case study from the Bahamas right
61:19 they poured down Over 20 200 ft burial. I mean that's 7-800,
61:24 almost 800 m of burial. And didn't find any pressure solution. So
61:30 I talk about Minimum burial depth, rely on this case study which suggests
61:37 m. And so I just rounded to about 1000 m. Okay.
61:43 for my dissertation, I worked the chalk in south texas and Mexico and
61:50 . And I got into the chalk obviously. And I came across the
61:55 by a german called Neugebauer. And interesting that he modeled pressure solution from
62:02 northwest european chalk deposits and came up a Minimum barrel depth of 1000 m
62:08 initiate pressure solution. So 2020 years , after he published his paper lent
62:17 she basically just sort of proved I his model right? Because you're comparing
62:22 to chalks, These are de positional . And and he was talking about
62:27 deposition of talks, right? These not Curtis, these are tertiary
62:30 but it's the same kind of de system. All right, okay,
62:35 until somebody can prove we can do at shallower barrel depth. I think
62:38 have to honor the data 802,000 Okay, so that's what I mean
62:43 barrel dia genesis. And of course expressions are going to be uh then
62:49 stones are gonna be style lights. you see the offset here, This
62:53 called style ICT amplitude and the amount amplitude along the style light represents the
63:00 amount of material lost along that one . So you can see from this
63:05 here that's a offset of about 2.5 . That means all the way along
63:12 style light, you would have lost least 2.5 million 2.5 centimetres of
63:17 Okay, minimum. You can't prove just minimum. Alright, so you
63:23 the importance here, this is a source of for filling cement.
63:28 This stuff dissolves. It's gotta go else. Alright. And most skylights
63:33 you'd expect our bed parallel, They mimic the betting and they set
63:41 horizontally, right? Because the principal direction Yes, one or sigma one
63:48 is like this. Right? So expect your style lights to be like
63:52 . If the pressure is exerted this ? Now what if you get into
63:56 full belt or a strike sip or fault system. Right? We have
64:01 all stress. We have this kind compression stress. You can do what
64:06 can create. Hi Signal one This . Right? And make what vertical
64:13 . So we always pay attention to orientation of our style lights. Because
64:17 you encounter vertical skylights then you know into a setting influenced by compression.
64:22 stress related to folding or to wrench of faulting. Okay, now,
64:30 expression of grain stones. I showed this yesterday. It's a grain to
64:34 soup tureen. Okay, and then the expression in mormon critic lime
64:40 It's usually not the style lights. is what we call whiskey micro style
64:45 . The common name is horse tail lights. And you know, a
64:51 of my classic buddies look at this and they say, oh that's not
64:56 solution. Those are primary clay laminate have been physically compacted. And I
65:02 , well if that was the case why does this come right into a
65:06 light with amplitude, That sort of a genetic relationship. And then I
65:11 , look at this borough structure, never see the boroughs cut the style
65:17 , the micro style lights. The skylights always wrap around the borough.
65:23 suggests that they formed after the They weren't there first. And then
65:27 borrowing started. And to prove that can see fabric like this where there
65:32 a borough. And look at the solution seems to go right across the
65:36 . So that tells you this is genetic and not deposition all. And
65:40 you actually dissolve the boroughs like you here. So this is the,
65:45 we call the non structured whiskey micro light. This is common Democratic lime
65:51 . It's also a source for calcium . It's just hard to prove How
65:55 material has been lost along that Or that swarm of scenes.
66:00 you can prove it for a style , but you can't really quantify how
66:04 material has been lost along these Okay, but the point is that
66:10 , don't receptor diet genesis comes into for for this phenomena, right?
66:15 you set up your style light and start dissolving that carbonate gets released from
66:20 style light moves away from the style tree saturates that calcium carbonate and re
66:26 locally as a poor filling cement. this has been shown many, many
66:31 in the literature. uh this is famous example back in the early 80's
66:37 the Devonian in Western Canada where these carbonates were buried into the realm of
66:43 solution and look at the preservation of porosity or the degree of calcite cement
66:49 by the black and white, very porosity right along the style light and
66:54 increases away from the style light on sides. Conversely more intense segmentation,
67:00 along the style. Light decreasing away the style light on both sides.
67:06 argues again for local donor receptor die , right? It tells you that
67:12 , you know, once you dissolve the style light, that material doesn't
67:16 very far before re precipitates as a filling cement. And you see what
67:22 doing here from a reservoir ah standpoint . These through going style lights potentially
67:29 become vertical permeability barriers to flow. this is important when you're trying to
67:36 how to move fluid out of these or how to sweep other fluids into
67:41 reservoir to sweep out the hydrocarbon. talk about this in more detail our
67:46 last lecture on modeling or zoning carbonate . Okay, so everybody clear about
67:54 pressure solution story and how it links to cement ation. So let's just
67:59 at the cement very quickly. All , the cement tend to be much
68:04 crystalline, hundreds of microns, two scale. So that includes these larger
68:10 that occur between the grains that have been structured and that's the timing
68:15 Right? If you're if you never the cement across this sutra grain
68:21 then you know that they formed after surgery. Well, that's our definition
68:24 burial segmentation. Alright. And sometimes large calcite crystal that we called
68:31 Well, encompass a bunch of brains if those grains are already future by
68:36 solution that had to form after because that form first, those grains would
68:41 been frozen in place. There'd be way to search for them together.
68:46 . And a lot of people think point politic calcite cement is probably just
68:50 syntax ceo calcite cement. Alright, is somewhere out of the plane of
68:56 on a cry in order to All right now, sometimes the cement
69:01 not very big and this bothers some , right? They see these tiny
69:05 . Oh, that must be a diet genetic environment. No, this
69:09 still be burial calcite cement. You don't have big ferocity to grow bigger
69:15 . Okay, so that's the limiting . It's not that we've changed hygienic
69:21 that these are small tiny pores. so you can't grow bigger crystals.
69:25 , They're just going to be a 100 microns across for scale. All
69:29 , so let me just finish up a couple examples here and then I'll
69:33 you the third way to make secondary during burial. All right, So
69:39 is uh we'll stick with the Jurassic over because it's a nice little grain
69:43 . Simple grain shape. This is sample From about 7500 ft of
69:51 The blue is primary porosity. The are the calcite cements. You can
69:55 the woods, you're not dissolved Okay. And again, the question
70:01 always have is what's the timing of segmentation? Is this early calcite cement
70:07 is this later? And the answer earlier. Late. What's between the
70:24 ? The lettering? Right? And not between the grants? The white
70:29 cement? I don't think you find example there where there's calcite actually between
70:34 future grain or overlying the future grain or? No, it can overline
70:41 suit. It can overlay the super contact but not squeezed into the
70:45 S. Okay. So that tells the timing has to be after the
70:49 suit train. Right? So these those inter particle cal sites amounts that
70:54 away from the future grain contact. . Conversely, if this is why
71:01 this marine cement, why aren't these amounts the white crystals because they don't
71:12 the right shape and morphology. Did we see any marine cement?
71:16 rico dimensional? No, they were or bladed arm a critic. And
71:22 aren't they freshwater cements? Because there's source none of the grains are leached
71:28 here. All right, you would leached these grains to generate the cement
71:31 same. If it was marine barrel genesis. So where's the cement coming
71:36 ? It's coming from the dissolution at ST grain to grain contacts.
71:42 And sometimes these crystals are big. I said, they encompass a bunch
71:48 bunch of grains. And if those are already structured by pressure solution,
71:53 that's our timing indicator that this is apocalyptic cement. Okay. And it
72:02 could be in a syntax cell overgrowth . I wouldn't be surprised if it's
72:07 nuclear did off of the Quran Oid it grows out into the rock like
72:11 . Okay, so having said let's just summarize the barrel die
72:18 The norm is to take inherited ferocity destroy it during burial by pressure solution
72:25 associated carbonate sedimentation. So, the , An industry up until the early
72:32 was to find ways to inhibit the effects of pressure solution. So how
72:38 you do that? You do that inhibiting uh oh, you do that
72:48 inhibiting pressure solution by early segmentation. that could be marine cement. That
72:53 be freshwater die genic die genetic That could be marine burial segmentation.
73:01 could do it another way by over geo pressuring and conceptually you could do
73:06 by what? By early hydrocarbon Right. If you've got early primary
73:12 or part of your sequence is a rock, say the eagle food or
73:17 part of the austin chalk, you start bleeding some of these hydrocarbons into
73:21 poor system and removing the water. you remove the water, you shut
73:25 your diet genesis machine because you need water to exchange the dissolved material.
73:33 move that dissolved material away from the solution scene to the poor system.
73:39 , so makes sense that you can that. This would be a way
73:43 do that. Nobody's really proven that in a case study. Okay.
73:49 then the favorable die genetic effects on involves deep barrel secondary porosity development.
73:56 is the 3rd way to generate secondary and the way you do this is
74:00 by generating acidic fluids that are drive the cracking of the hydrocarbons. Are
74:06 generated by a process called thermo chemical reduction? The acronym is T.
74:12 . R. And I'm gonna explain in more detail in our next lecture
74:18 Dolomites. But essentially Uh what TSR is H two s. And it's
74:27 creates a sulfuric acid that that drives drives the dissolution. But it also
74:33 places some of these unique non carbonate back into the carbonate succession that are
74:40 a byproduct of this process. And sort of how you prove TSR.
74:45 , so let me finish up by on some of these relationships here.
74:49 the first example here illustrates the role really segmentation and inhibiting pressure solution and
74:57 reservoir quality of depth. This is uh to outcrops sequences around the periphery
75:03 the paris basin in France. The represents high energy utility Greenstone. The
75:09 represents deeper subtitle, my critic carbonate then the brown represents the lagoon.
75:14 sam Logan will show that pro graded the top of this upper who would
75:20 body system. Alright, so look the scale here. That's That's five
75:25 , I'm sorry, five m. , so there's not a lot of
75:29 difference between these two sequences. But look at the pressure solution.
75:35 all the pressure solution is in the grain stone? And very little pressure
75:41 in the upper grain stone. of , very little process preserved in the
75:45 one because of that pressure solution and prostate in the upper part. All
75:50 . So both of these sequences experienced same barrel history. But the lower
75:56 never experienced any really die genesis. , the upper sequence experienced a little
76:01 of dissolution and pre compaction segmentation enough create a rigid framework to resist later
76:08 solution. Okay, so that's an example. Here's a real world example
76:14 the subsurface. This is Again the smack over again. We're at about
76:20 700 ft of burial or so I . And what do we see?
76:25 see fabric selective dissolution to create the and then that generates the pre compaction
76:33 cements their ice A pack is bladed into an equal mosaic. So they
76:38 strikingly similar to what I said was people would call fresh water for attic
76:43 genesis, but it also now mimics marine barrel die genesis story as
76:50 Okay, so irrespective of whether it's to fresh water due to just shallow
76:56 die genesis of the reaganite. The is, is what you generate these
77:01 compaction cement. They resist later pressure . You don't see collapse of the
77:07 , You don't see grain to grain , you've frozen that fabric in
77:11 And if you preserve enough primary then you've got good reservoir quality.
77:17 . And this is what people used chase. Alright for finding reservoirs and
77:21 like the Jurassic. All right, . And then there are examples like
77:27 in the Jurassic that make absolutely no . I mean, we see lots
77:30 fluids, good ferocity, good reservoir . But where's the cement? There
77:35 seem to be as much cement There is Grain two grains featuring
77:39 But you would expect for this burial , which again, There's about 7800
77:43 of burial. You'd expect to see lot more cement. And these are
77:48 relationships. Alright. But maybe something this reflects what I was talking about
77:55 . Maybe this is a situation where during burial, after the onset of
78:00 solution, you've started to bring in hydrocarbons to sweep away the water to
78:06 rid of the water. That shuts your segmentation story. Shuts down everything
78:10 genetically. Okay, you don't have , you don't have carbonate die
78:15 right? So the historically, those the ways companies have tried to look
78:22 reservoirs, right? Trying to hold porosity long enough to trap the
78:27 But now we know from the late , early 90s and I think we're
78:31 this more and more, as we we drill deeper. that a lot
78:35 this process created after the onset of solution. And so this leads us
78:41 our last conversation about the deep barrel porosity and some of the criteria for
78:49 recognition of this porosity. How do , how do you prove the timing
78:54 ? And I've listed a bunch of here. I'm just going to focus
78:57 on the three that I highlighted in . First thing you look for is
79:02 high degree of secondary porosity preserved along cutting the style light. Right?
79:09 just the opposite of what I Normally that should be preferentially cemented.
79:13 here is just the opposite. so that implies that that process that
79:19 after the skylight was already there. second situation be where pressure solution seems
79:25 to float in secondary process. I'll you this in a minute and then
79:30 of normal, stable calcified grants. the red flag. I talked about
79:35 calcification rain being dissolved out as a flag because those minerals don't usually dissolve
79:41 the subsurface. Hi matt calcite loses magnesium re crystallizes but it doesn't dissolve
79:47 on a wholesale scale. And the with the cal city grants.
79:52 But if you see a leech brock which is low mag cal cider,
79:56 see a leached cry annoyed, that's red flag. That tells you there's
80:01 unique about the fluid chemistry. so let me just finish up with
80:05 few examples here. And uh there several papers on the on the blackboard
80:13 the document some of these relationships and lime stones. First example here is
80:21 big giant gas field from Southeast Asia never been put online because while it
80:28 a ton of of methane has what four times as much C.
80:36 And so there's no market for Two and china yet right? Or
80:42 Asia. So uh it's called the field but it's not a producing gas
80:47 . And the tuna field is basically carbonate platform platforms about 5000 ft
80:56 The reservoir is about 5000 ft thick this is what the rock looks
81:00 Okay. And of course, Exxon on this back in the Back in
81:06 early 80s and they interpreted all this to be related to conformity die
81:12 All right. They put a major they call type one conformity on top
81:16 the platform based on the way they the straddle geometries and they related all
81:21 porosity to exposure to fresh water? , here's the problem. First thing
81:27 see is leaching of all these stable city grants, calcification, oysters,
81:34 algae, benthic, foraminifera kind of are all being leached out. But
81:39 clincher is something like this. Here's style light and it appears to be
81:44 in the secondary porosity. That makes sense. If that was process was
81:48 first and then you buried. why would you put a style
81:52 Right in the middle of ferocity makes sense what you're looking at here are
81:58 grants that were suited together to set the micro style light and then later
82:04 fluid came through to dissolve out part this grain and part of this grain
82:08 create this apparent floating style light. the timing indicator that tells you that
82:14 dissolution. Okay, right. And here's the second example. This is
82:20 east texas. The Jurassic Haynesville. are not the shales that Angela is
82:27 to be working the Haynesville carbonates. also called Gilmer lime stones uh in
82:34 texas. But these are these produced exclusively from Hewlett grain stones and you
82:41 see the blue hue of the This is taken with the white paper
82:46 . The DPL you would never see prostate with a normal thin section
82:51 Okay, but what's the timing indicator ? That tells you this is not
82:56 formed secondary porosity six. Okay, . But let me turn this
83:07 There are many papers that have interpret to be freshwater die genesis. So
83:12 is it not freshwater die genesis? did we see in freshwater? Fanatic
83:19 genesis? Okay, we saw leach the grains. Okay, I'll give
83:23 that. But what's missing? We have developed pre compaction, right.
83:33 should have seen the pre compaction. packers cement. Right? You don't
83:37 that and you don't see any cement the grains. All right. You
83:40 see any of that cement fabric. . In fact, there's there's porosity
83:46 on both sides of the stylistic Again, that's an indicator that that
83:50 that formed after the grains had already featured. So this is barrel
83:55 Alright, This occurred after the rocks been buried. Uh This will be
83:59 of a case study we go through . So, I won't go into
84:03 detail right now because I'll explain this quite a bit of detail. But
84:08 just want to appreciate the timing And then the last example here is
84:12 the Devonian, Western Canada, there's sequence called the Zhaan Marie formation and
84:19 Alberta and in british Columbia. And produces from these under pressured gas
84:28 Uh So these are strongly to operate and they have cavities developed in some
84:34 the some of the so called bounced fabric. And those cavities are sometimes
84:40 filled with the little micro fossil called analysis. We haven't talked about reanalysis
84:45 it's sort of unique to the devonian salary in. And it's a cavity
84:52 organism. That's slow mag calcite almost . You never see it dissolved out
84:57 of that stable mineralogy. But here the white paper technique you can see
85:01 this micro leached that's all blue secondary molding ferocity. So that's the red
85:08 that tells you there's something going on terms of fluid chemistry. But then
85:12 clincher is this the style. I at the style light coming along here
85:17 out by secondary buggy porosity. Pick the style light on the other
85:21 Now that buggy poor had to be after the style light. Well that's
85:26 definition of burial dissolution. Right? I just want you to appreciate these
85:31 the kinds of things we try to for first and then if you need
85:35 be more precise in terms of then you throw the geochemistry at the
85:39 cements, right? You do isotopes fluid inclusions and things like that.
85:45 think you can you can work out timing just from the photography.
85:51 The thin sections. So everybody appreciate I've said here. Now we've got
85:57 dia genetic environments to or near surface by definition pre compaction and then the
86:02 burial. And I've showed you how can make secondary process the early by
86:08 or marine barrel die genesis. But showed you a third way for making
86:13 at depth. Okay, so you the implications if you if you're making
86:18 porosity early, everything is linked to surface, right there, close to
86:24 surface. But if you're making prostate , what's the implication for fluid
86:30 Where's the fluid coming from? It's from a deeper source or it's being
86:34 along fault fracture systems. If you figure that out, then this is
86:39 you can exploit in the subsurface. ? If you understand your regional faulting
86:44 you understand how the faces are tied to that structural framework, maybe that's
86:48 you can exploit in the subsurface. , last slide here is just the
86:55 of the carbonate cement recognition. The of cement we get in the different
87:01 environments. This is just for lime . Okay, so ah if we
87:06 the lab exercise, this is coming play for your lab exercise, but
87:11 . We don't have time for Any questions? We'll take a little
87:15 minute break here before we get into world of dolomite. No questions.
87:31 . Okay, the next thing on agenda is lecture seven and we're going
87:37 talk now about demonization. Make some out of that because approximately half of
87:44 carbonate reservoirs around the world are associated Dola stones. So, there's obviously
87:50 economic significance there and it turns out most of our major lead zinc deposits
87:55 also associated with with dramatized sequences. right, So what I'm going to
88:01 here is I'm going to make a comments about the mineral dolomite and what
88:05 think are the key controls for making . And uh they're gonna see there
88:10 a lot of issues here. The was discovered by a Frenchman dull um
88:16 Back in the 1700s and uh I that was well over 200 years ago
88:23 uh sometimes I wonder if we made progress in understanding how to make this
88:30 and and how to replace the limestone dolomite. But anyway, we'll we'll
88:36 some general comments here first and then take you through the popular models that
88:42 have come up with over the years explain how you take a limestone and
88:46 convert it to dolomite. All because everybody feels compelled to try to
88:51 that. But then I'm going to up by talking about cross the evolution
88:55 dola stones. And even though we understand all of these relationships, some
89:00 these things we see time and time , that if you work at Dulles
89:04 reservoir, you should be familiar with of these pathways for porosity and permeability
89:10 . Okay, so we'll start with diagram here, which has three data
89:15 . So, the I guess three points and says in 9000, but
89:21 can see the three, three data with, I guess they're a bunch
89:25 samples for each of these. But , what you see is what everybody
89:30 is seen with the dolomite trend. ? Our younger carbonate systems don't have
89:34 much dolomite as our older paleozoic systems . And so you can interpret this
89:41 of two ways you could say, , there was something different about the
89:46 water back in the paleozoic compared but that assumes that the Dolomites coming
89:51 out of seawater. And I'm not I'd make that assumption to begin
89:56 And then the other way to explain is that what you're seeing here is
89:59 time effect. The longer limestone sit on their near the earth's surface,
90:05 more likely they are eventually going to a fluid is capable of converting get
90:10 a to a dollar stone. so the mineral dolomite Is this unique
90:18 magnesium carbonate mineral. By definition 50% , 50% magnesium. But now,
90:24 heimat calcite, where the magnesium was distributed here in this mineral there's a
90:30 a uh there's an ordering to the of these catamarans, the blue magnesium
90:37 irons. And in the black calcium are distributed as individual planes separated by
90:44 of the carbonate and iron, which little fork lock structure here. And
90:50 we call ideal stoke geometric dolomite Would a dolomite crystal with 50% calcium 50%
90:59 with this perfect ordering. Which means if you ran that minerals through X
91:04 diffraction machine, you get these incredibly peaks. Okay, that would reflect
91:09 well ordered nature to the crystal. , well, here's the problem.
91:14 right. None of the dolomite that today had earth's surface temperature and pressure
91:20 stoking metric dolomite. It's calcium It only has 45, magnesium.
91:28 call it proto dolomite and is poorly . Okay, so right off the
91:35 , we're starting off with something that have great stability. So, just
91:39 that in mind. For a later , it turns out that even a
91:44 of our ancient Dolomites never achieved this stability. They never achieve ideal state
91:50 there are 50, 50 and with ordering. Okay, now the controversy
91:56 the carbonate community is how do you this? How do you make
92:00 Well, obviously you have to increase magnesium concentration of your fluid. All
92:06 , In order to get up to . Alright, because none of our
92:09 minerals are sure. Hi, I'm doesn't have any magnesium Calcite has a
92:17 percent heimat calcite has up to I the highest is 38% for some of
92:23 kind of terms. Right? there's not enough magnesium around. You've
92:26 to bring magnesium in. Right. the question is, what are the
92:30 controls for making dolomite is the temperature is it kinetics right time.
92:39 all of our early form dolomite that see today around the world is not
92:45 with normal marine settings. It's associated these marginal marine often evaporate IQ.
92:50 restricted environments. Okay. And the is, is that temperature factor,
92:58 that uh, kinetic effect? All . If you try to go to
93:03 lab today and make synthetic dolomite at C and one atmosphere pressure, you
93:09 do it at least a geochemist can't it. Okay, now there's a
93:15 dog that precipitated a kidney stone of dolomite. So presumably the dog knows
93:22 to do it. But the geochemist figured out how to do it.
93:25 relatively low temperature. All right. all of the models, almost all
93:30 the models that I talked to you are skewed toward low temperature dehumanization because
93:37 think what's happening is that the the limestone is that get demonetized our
93:43 and they can't be too deeply buried to be dull noticed or they wouldn't
93:50 any permeability to let the fluid come . So everybody thinks that these Dolomites
93:54 forming it early near surface, lower surface temperatures. But Geochemist can't make
94:02 in the lab unless you jack up temperature 200°C. If you jack up the
94:06 100°C. You can make synthetic dolomite in few months. Okay. So this
94:12 the controversy in the carbonate community and been there forever. Certainly from my
94:18 . Right. People debating on whether stolen my forms earlier forms late.
94:22 controls the currency distribution? All So, I want to make a
94:28 about the recognition of dolomite. Of you can you can powder a sample
94:32 run it through the X ray diffraction identify dolomite dolomite that way. But
94:37 quicker way is to try to stay your thin section. So, I
94:41 about this before you see the reddish staying here. That's for calcite.
94:46 had a staying called the lizard red . And I'll send you that information
94:52 later this weekend. And the stuff not stained uh in a carbonate succession
94:58 usually taken to be dolomite. But courts would not stay in like
95:03 and hydrate would not staying like this . And, you know, everybody
95:08 everybody thinks the dolomite only precipitates as little sugar cubes. Like you see
95:14 . Right, nice little rabbit Well, that's not true because calcite
95:19 also precipitate with that morphology. So, you can't use the shape
95:23 the unstained crystal to say necessarily that is dollar mike. All right.
95:30 then look at a lot of these crystals. They're actually sub federal to
95:34 federal in shape, which is not uncommon. So, you you should
95:38 be surprised by ah some of these crystals lacking that good Romberg shape.
95:44 again, the only way to really this and then the rocks is
95:50 Of course the well logs can break sounds like a store. The only
95:57 you can uh you can use the logs to differentiate between limestone and dolomite
96:03 , but on a finer scale you to stay in like, like I've
96:05 here. Okay, so let's talk the requirements for making geochemical reactions for
96:15 . Most of what we talked about the rock record is replacement of a
96:20 by dolomite. Right, So some of some sort of fluid comes into
96:25 rock and replaces the dole. Might remember dolomite could be a direct precipitate
96:30 of poor fluid. Okay, it be a cement and lime stones.
96:35 can be a cement in dollar All right, now, the conventional
96:40 dictates that if you want to start the limestone and converted to dolomite,
96:46 have to, first of all have nearby source of magnesium. Sea water
96:56 a lot of magnesium. Okay, you've got to do what you gotta
97:04 a second, you've got to have hydrological system that effectively moves that water
97:11 you have to have recharge, there's enough magnesium in one poor volume of
97:15 to account for decolonization. So, I recharge again, right, that's
97:18 common theme for all these diabetic reactions then you need a host limestone capable
97:25 being demonetized. And what that means that limestone still has to have some
97:31 when those fluids come through or there's way you're going to dramatize it,
97:35 ? If it's a tight non porous tombstone, then you're not going to
97:42 . Alright, So you're gonna see all the popular models that have been
97:46 now for the last 50 or 60 . um excuse me? Um Try
97:52 account for these three relationships, They have a source for their
97:59 they have a hydrological system, what call the pump, right way to
98:03 that fluid from the source to the , and then they need a host
98:08 that's still capable of being dramatized, implies what implies the faces control,
98:14 I think is pretty common. so let me take you back to
98:20 long time ago before you guys were . I presume you're not that
98:25 certainly don't look that old to So, uh Let's go back to
98:30 mid 1960s. Okay. and uh famous geologists that worked at the University
98:37 texas? I mentioned bob folks this . Folk was a photographer where carbonates
98:42 plastics. His sidekick was linton who was a geochemist. Okay,
98:47 focus passed away, Lindland is still in Maryland, I think he still
98:52 Maryland. But anyway, Back in 60s, before this paper was
98:58 they started talking about this relationship between and the magnesium to calcium ratio as
99:05 control on dehumanization. And they put little diagram together where they cross plotted
99:12 calcium ratio versus solemnity of the And they superimpose these different hydrological
99:19 Okay. So what's up here? do you all know what is sapa
99:26 heard that term before? South africa an Arabic term for arid evaporated title
99:31 . All right. So, high , high magnesium to calcium ratio In
99:36 60s. This is where they found first modern example of dolomite cement in
99:41 of these tidal flats. Okay, it makes sense. Right? You've
99:45 a high magnesium and calcium ratio. got a lot of dissolved solids in
99:50 water. All right. And then superimpose the other hydrogen hydrogen hydrological
100:00 So you can see rivers and lakes subsurface Kobe Bryant Seawater, there's seawater
100:06 parts per 1000 uh 321 magnesium and calcium ratio. Okay. And then
100:13 superimpose what they thought was a stability between calcite and dolomite based on the
100:21 and magnesium calcium ratio. All So, if it looks like it
100:27 for this relationship up here, That's where they found the first modern
100:31 dolomite. If you believe their then theoretically you should do what you
100:35 be able to come down this way maybe get in a situation where you
100:40 ocean water with fresh water? Remember mixing zone I talked about before and
100:47 make dola minus setting like that. this had a pronounced influence on some
100:51 the later models that were developed. they finally, in the 70s got
100:56 to two publishing this this paper? right. So, I want you
101:00 keep that in mind because when we at the the popular models which I've
101:05 in their historical appearance, a lot these early models were influenced by that
101:11 . And there are inferred stability relationship calcite and dolomite. Okay, so
101:18 are the popular models Hyper Saline Brian with two two variations on the team
101:24 moving the fluids, mixing zone that hydrological boundary between marine and freshwater
101:33 conviction. I'll explain all these in a minute Based on the de
101:36 All right. These are all the models that have been in the literature
101:41 back in the late 60s, all way up to the 80s.
101:46 And then what God added later In 90s and this is work that came
101:50 of Western Canada because of their core . The deep barreled organization model which
101:55 that the Dolomites replaced the lime stones they'd already undergone some degree of pressure
102:01 . Okay, so most of these are early near surface models. And
102:06 this is obviously a deep barrel colonization . Okay, so let's go through
102:12 . And uh I'll show you some of how people have used these.
102:17 , the hyper saline brian model, source of magnesium is seawater modified by
102:23 . And when you take a bucket water of seawater and you evaporated,
102:28 know what the first medal that comes is? That's all it's calcium
102:36 Okay, calcium carbonate. All And that includes that can include
102:44 And then what else what comes after is gypsum or and hydrate. If
102:51 no water and then it would be light. Okay. So,
102:55 let's actually comes in comes in All right. So if you start
103:01 now calcium carbonate during the evaporation of , what are you doing to your
103:05 calcium ratio? You're increasing it, , because you're pulling calcium out to
103:09 al side. Okay, And or pulling out to make a gypsum.
103:16 , gypsum calcium sulfate. All So that's the way that they think
103:21 , that's the way people think you the the magnesium calcium ratio then it's
103:26 matter. How do you pump that through the sediment? Do you pull
103:31 up by evaporation that's called evaporative pumping do you push it downwards? Creative
103:36 that's denser then the underlying seawater and displace this way? That's called
103:42 Okay. And in either case we'll about either case in a minute.
103:47 case the timing is early in near . So, that made you should
103:50 able to show petra graphically and geo that that dolomite formed early.
103:56 It's relatively low temperature and before the of pressure solution, in fact it
104:02 have inhibited pressure solution. All So what are the environmental associations today
104:07 modern evaporated tidal flats is where we the dolomite forming some of the coastal
104:12 that I'll show you the southern Alright, so here's the cartoon.
104:19 next weekend I will get into our of modern carbonate environments and we will
104:24 some time talking about carbon a tidal . And I said the other day
104:29 tidal flats are really storm flats. sediment that's up on the title flat
104:35 mean high tide. It gets there the storm process is pushing sediment from
104:41 to left. Okay. And if go to any modern title flat today
104:46 you dig a trench down about a or so, you will encounter the
104:50 water table. So the marine water extends under that sediment surface.
104:56 And so one aspect of the model that by evaporation, you pull
105:02 you draw up these calcium rich brian's way. And what do you find
105:07 the surface? You find a so dolomite crust. Well, what are
105:11 still in my crest? If you've been in the field, you think
105:15 the literature, these are solid masses dolomite. No, they are storm
105:20 of colloidal grain stone with a little of dolomite cement and actually more a
105:26 and hi matt calcite cement, because is where they found the first occurrence
105:32 modern forming dolomite. It's become dolomite . Right? So, it gives
105:37 the false impression that this is massive . This is not. And by
105:43 way, all these models are trying explain replacement bill amortization. This is
105:48 , this is no replacement here. is poor filling cement. Okay,
105:53 getting replaced your with this model in modern. Okay, now the other
105:59 of the model is that people would that by pulling out the calcium to
106:03 calcite or gypsum depending on however the is you're going to create these magnesium
106:10 brian's that are denser and they're going go down like this and react with
106:14 sediment underneath. Trust me, people looked all over these modern tidal flats
106:21 nobody has been able to find dehumanization , under these tidal flats.
106:26 Replacement organization is not there. But there is one example in a
106:31 Selena where we think we have re going on today. So here's the
106:37 the here's the area in the southern , this is keiko's platform. This
106:43 the title flat. We have major flat complex developed uh, up against
106:50 of these older places seen islands and enjoy walking on these firm surfaces because
106:56 is the dolomite crust. These are storm layers of political sand that were
107:01 up by hurricanes or the occasional winter and then interstitial. He cemented by
107:08 little bit of dolomite. Otherwise you sink up to your knees in the
107:12 all right. But I want you appreciate, you're not dramatizing the whole
107:17 . It's very patchy. So it's at any one point in time this
107:21 . And if you were to core trench and be patchy in the in
107:25 subsurface, right. So there's not not extensive demonization of these tidal
107:31 I guess that's what I'm saying. there's no replacement dehumanization. Because when
107:36 look at these dolomite crushed, you to do this with the scanning electron
107:41 . Look at, look at the of these cement. These are all
107:44 tiny cement. So little rhombus shaped here are pro to dolomite. All
107:50 . Look at there are only a microns across the scale. The little
107:53 shape features here are the reaganite needles we talked about before and then some
107:58 these equant crystals here are high mack . So there's just a little bit
108:03 dolomite here and it's all cement. no replacement of anything in this in
108:09 model. Right. And this has true for all the uh Jared,
108:16 arid and even rainy title flat complexes the world. Nobody's been able to
108:20 replacement dolomite. All right. The model says that the fluids should go
108:28 like this and dramatized underlying carbonate off these tidal flats. The roots of
108:34 model don't come from the modern, come from the Permian in west
108:39 If you ever get a chance to, to dissect the Permian reef
108:43 in west texas. What you can from walking up some of these canyons
108:47 then driving back to the inner part the time equivalent faces is you see
108:52 the permian we have this relatively broad platform dropping abruptly off into the deep
108:59 Delaware basin. And we had reef grain stones developed along the margin.
109:05 showed you what those reef deposits look today. Right with the marine
109:08 I showed you those Zula carbonate sands it with some marines cements.
109:14 remember the the buckled up carbonate this ? The TP structures that's in the
109:20 called orange carbon A bar. These piss a lot of goods.
109:26 but then what is the rest of profile? It's more and more restricted
109:29 as you go back in and eventually get into an evaporated setting back
109:35 subtitle evaporates and then title flat And so when people look at the
109:41 of dolomite, they saw down dip these up dip evaporates. Everything was
109:47 except the reef In the Upper four of that reef complex. And so
109:54 wasn't the reef dramatized because it lost this process on the sea floor by
109:59 big fibrous marine cement. Okay, the model was the intuitive model was
110:05 these these dense brian's up here must moved down dip and dramatized everything down
110:12 until they got to the reef that no porosity and permeability. Okay,
110:17 that's where this model comes from. it's never been shown to operate in
110:22 modern title flat system. But we an example. We think on keiko's
110:28 in the southern Bahamas, I was a little bit about the pleistocene here
110:33 the climatic effect where the grains are leached. But this little island here
110:40 west Caicos, the northwestern part of Caicos. Prior to about 15 years
110:46 looked like this, it was a coastal Selena. That's a whole
110:53 Beach Ridge 25 ft of elevation. a pleistocene high ridge up to 70
110:59 of elevation. You've created a natural between the two and that depression periodically
111:05 in with seawater either pushed in by or pushed in by strong oceanic
111:13 Either going over the ridge or pushing the permeable carbonate sand. And so
111:19 the salon was filled with seawater and would evaporate out. All right.
111:24 you can see there was some attempt to uh mind this commercially. They
111:29 mind it on other islands on on platform, but they never never got
111:34 the ground here. And look how we are to the open ocean.
111:39 the platform margin right there. Somebody a good arm could throw a baseball
111:44 rock from the beach to the Okay, that's how close you are
111:50 the open ocean. All right. what happens periodically on the Selena,
111:57 fills in with water and then it out, right and evaporates down to
112:02 light. But what's evaporating in the ? It is gypsum. Ok.
112:09 the way gypsum here, the dark of bacteria mats with little gypsum
112:15 Okay, so when we when we this back in the early 80s,
112:20 thought this would be a great place test the reflux model, right?
112:24 if you're pulling out calcium to make up here, theoretically those magnesium rich
112:29 go down and dramatize the underlying So we came back and we drilled
112:37 succession back here. So there's a of same beach ridge. There is
112:41 of the place to sing ridge. drill the number of boreholes across the
112:46 . We drill in with the irrigation . You see this pipe here?
112:50 aluminum tube that we can push in AD. And we were pushing it
112:54 and we're hitting this hard rock that thought was places in bedrock. And
113:00 course we were interested in according to . So after we did this,
113:05 came back and said casing and we rotary drilled into the Pleistocene. And
113:11 drilled all of these holes here and didn't realize that the hard rock we
113:15 hitting was the top of the stolen body right here and the top of
113:21 places scene is actually right here. the cal creed that defines the top
113:25 the placing. All right. So dollar might is occurring at the base
113:30 the whole same succession. The fluid to be moving down and out like
113:35 . They react to these grain stones the base. The longer they sit
113:39 the more dolomite we have. And you go further up becomes diplomatic sand
113:44 then just gypsum cemented sand and then mush of organic material and gypsum.
113:52 , so we think there's a we there's a good analog for the reflux
113:58 . Okay. And more importantly, you look and we dated the
114:02 it dates out this whole scene. we know that this is relatively young
114:07 delight replacement. We look at the looks identical to what you see in
114:11 rock record. These are poorly sorted deposits that were thrown back from the
114:16 rich. All right. So it's mixture of fine and coarse sand.
114:21 course of sand pieces are things like and mollusc shells and the finer sand
114:29 is smaller pieces of coral and and material. All right. So this
114:34 not in the critic. This is This is what you would call what
114:38 a floats down, right? Because reached your eye from offshore uh float
114:43 with a Greenstone matrix. And so did the dull monetizing fluids go after
114:49 they go after the finer sand as going to talk about in a
114:53 And then what happens the larger grains all about to give you that molding
114:58 . Okay. And this is going be identical to what I show you
115:02 the rock record. All right. a reflex model. But what's the
115:12 for the reflux model? The linkages to evaporates, Right. You've got
115:16 have evaporates, but people back in 60s and 70s realized very quickly wait
115:21 minute. I got all this thick dolomite in the rock record, but
115:25 no nearby evaporates. So, I another model. So, what was
115:29 next model to come into play? zone model? All right. Where
115:33 model argues that by diluting seawater with water, you reduce the honest competition
115:40 make it easier for magnesium to substitute the limestone to convert it to
115:46 Okay, so even though the magnesium ratio is going down because you've removed
115:53 those other cat ions, it makes easier for magnesium to replace there are
115:59 into the limestone to give you the . That's the model. Okay,
116:03 just the messenger here. All So, I don't believe this model
116:08 have but it doesn't really matter. , the hydrology here would be mixing
116:15 coastal mixing zones, like I alluded earlier. Right. And the diagrams
116:20 you build island topography, you mix water with the offshore marine. All
116:25 . You could also be an evaporated where you have catastrophic rainfall periodically.
116:30 mixes with those evaporates, right? either case, the timing would be
116:35 in near surface. So, the is generally a human climate with a
116:39 more rainfall. And unfortunately, the modern analog, and trust me,
116:45 have been looking at modern coastal mixing for 40, 50 years now,
116:52 the only thing I've been able to is Dolomites cement off the yucatan and
116:58 mixing, no replacement all night. , either it takes more time than
117:03 think or doesn't work. Okay, , but it's a popular model and
117:10 show you why in a minute. , so here's the cartoon that people
117:15 for, for mixing zone dehumanization, ? Either build topography or you create
117:24 by lowering sea level. If you a humid climate, you generate a
117:29 lens in your higher topography. That is going to be displaced offshore.
117:36 may have heard of the guy been principle for hydrology, right?
117:41 for every foot of fresh water, then I confined aquifer above sea
117:45 You'll displace that fresh water Roughly 40 down. Okay, so if you
117:50 a lot of elevation, you can push that water offshore. And I
117:54 the florida biographer this morning, where water goes off 50 miles offshore of
118:00 before bubbles up. Okay, so you think the mixing zone,
118:06 this transition zone between the black freshwater zone and the yellow sea water free
118:14 , marine free attic, do you that's where you make dolomite factor in
118:19 sea level. Right? All these steelworkers have sea level yo yoing up
118:25 down through geological time. So when level goes up, you're mixing zone
118:30 up and dramatizes this fluid, the level drops. That dramatizes this fluid
118:36 this is a great way to create dolomite without invoking nearby evaporates.
118:43 And this is why it's become so . So, people go back to
118:47 rock records. The famous first case was from the Mississippi in in the
118:53 basin and uh they look for geological where they could create a case for
119:01 a mixing zone. All right, that's exactly what Choquette Einstein and did
119:06 in 1980, they looked at the that went from deeper water, McCready
119:13 up into a high energy. You sand body system overlaying by it's
119:19 the critic Laguna carbonates, alright, you can see where the dolomite is
119:23 purple, it's mostly where it's it's not in the U.
119:27 Shoals, it's below the US shoals these McCready carbonates, okay, And
119:32 not in the Laguna stuff above So, when they mapped out the
119:36 of the zoo it sands and the of the Dolomites shown in purple,
119:41 saw a good relationship between the Zula bodies and the dolomite. And so
119:49 invoked that desire. These sewage souls have built up above sea level to
119:55 little islands. Like I showed you lunch that had the beach rock
120:00 They must have build up above sea . They must have got rained on
120:03 generator freshwater lance. And where were freshwater lands mix with marine water underneath
120:09 give you the dollar might beneath the . All right. So that's how
120:15 interpreted the distribution of the dolomite. of course it's very difficult to publish
120:20 without a lot of geochemistry when you about Dolomites. And so they published
120:25 geochemistry back then. Back then it mostly stable isotopes and trace elements.
120:31 , But they published that data with interpretation. And so what's happened for
120:35 next 40 years basically is that people out there geochemistry when they start comparing
120:43 numbers to other case studies. Oh my numbers look just like Choquette and
120:48 and stuff. I'm going to interpret thing, zone dehumanization and this is
120:54 been happening for the last four Right? To me, it's a
120:59 reasoning, but but this is how have done it. All right.
121:03 what they haven't done is look at rocks, they become so enamored with
121:07 geochemical technology that they stopped looking at rocks and you should be looking at
121:14 rocks now because we have the fluorescence and the white paper technique to see
121:20 the masking effects of the dolomite and prove the timing right, prove.
121:24 whether it's early or late. The don't do that. All right.
121:29 that's that's this a popular model, . It's easy to come up with
121:33 scenario to account for mixing of freshwater marine water and invoke the mixing zone
121:40 . Next model came into play in early 80s was a kohat conviction
121:46 This is limited to these uh to steep margin, steep sided platform
121:52 like we haven't in the Bahamas or pacific atolls. These are surrounded by
121:58 deep water and cohort confection cohort was that works for the for Noah,
122:08 National Oceanic and atmospheric Administration for the . And and I think everybody,
122:16 don't think there's much disagreement that there long term circulation of cold oceanic water
122:23 the sides of these platforms and then get geo thermally heated. And you
122:28 up this long term circulation of seawater these platforms. Okay. And so
122:34 is what the cartoon shows here, long term circulation effect. But you've
122:40 to be in a situation where the is surrounded by thousands of feet of
122:44 in order to set that up. . And it's interesting that when you
122:50 at the deeper drilling in the Bahamas the pacific atolls, it turns out
122:56 most of these platforms are pretty pervasively . Alright, so this might be
123:00 viable model for something like this. is where the time works in your
123:04 . Right. You've got a lot time to circulate seawater through here and
123:08 the magnesium from seawater to rack with limestone to give you the the Dulles
123:13 fabric. But the limitation in terms application of the rock record is most
123:20 our basins in the rock record that prospect for are shallower basins or even
123:27 intricate tonic basins where this relationship would never been set up. Okay,
123:33 it could be a good model for Bahamas or for some of the pacific
123:38 . But I think the application is when you think about taking it back
123:44 say, the cretaceous and texas or . Right up on these shallow interpret
123:51 basins. Maverick basin. Right? East Sex assault basin, Mississippi salt
124:02 . There's no way you're gonna set kind of circulation up in that kind
124:06 uh, setting. Okay. And what came after that a little bit
124:11 was the so called basal de watering . Uh it's very common in the
124:16 record in the paleozoic to see these platforms drop off into a deeper water
124:23 , but the basin fill our shales evaporates or are delicious carbonates.
124:31 And in this model, they invoke of those kinds of sediments out in
124:37 basin as the source for their Okay, so this is compaction driven
124:44 , which could be driven by tectonic in some parts of the world have
124:49 invoked in Western Canada, for to squeeze some of the these magnesium
124:54 brides out of the basin fill. the timing here could be early to
125:01 given the thickness of your carbonate But the problem here here is
125:07 this unique platform to basin transition with evaporates out in the basin. We
125:12 have any modern analog because our basins too deep. Okay, the closest
125:18 we have to something like this might the ramp model and the Arabian gulf
125:24 the deeper part of the basin They are delicious carbonate. Alright,
125:29 if you've worked any paleozoic, you , it's very common to find shales
125:33 of these carbonate platforms. It's not to find thick basins evaporates off of
125:38 of these carbonate platforms. So, there's no good modern analog to
125:42 All right. So here's the cartoon squeeze his stuff up into the adjacent
125:49 the adjacent carbonate platform where your high faces with the best reservoir potential right
125:56 . So, where do you normally preferential demonization along the platform margin.
126:02 , you'd expect that. Okay, the famous case study for this is
126:08 devonian miyet build up that occurs in crop in the Canadian rockies. All
126:16 . So, you can see this an isolated carbonate platform that was reef
126:20 by Strome atop around reefs with the lagoon in the middle. The purple
126:26 out greater than 40 told the The blue is not pure limestone is
126:32 than 40 Dolomites. So there is back here in the inner part of
126:37 of the complex. But you can preferential harmonization around the periphery. And
126:42 , how do they interpret this They interpreted the magnesium rich brian's coming
126:48 the shell sequences down here, the influence formations and by compaction driven flow
126:56 up into the adjacent carbonate platform with greater degree of demonization along the platform
127:02 . All right. But the Dolomites occurred back here. Okay,
127:07 when people see this kind of relationship the rock record where you've got offshore
127:12 or shales and you've got preferential decolonization the platform margin. Almost always,
127:17 will invoke this de watering model. , now, what I find intriguing
127:24 this model is here, these displaced sheets coming off the reef that are
127:28 limestone, they sit closer to the source of of of demonization, but
127:34 still limestone. Okay, so, makes you wonder why do a lot
127:40 carbonate platforms exist to begin with because faulting? Right, basement block faulting
127:47 based on black faults can reactivate and up fluids later on the condolence
127:52 So, the other explanation for something this could be fall control demonization.
127:57 right, But this is the way have interpreted this model replied this model
128:03 an offshoot to that would be something we have in the michigan basin during
128:07 salary in, we have carbonate platform then isolated pinnacle reefs out in the
128:13 that are encased in deep water carbonate deep water evaporates. And again,
128:19 of these pinnacle reefs are preferentially delay , but not all of them.
128:24 it's not unequivocal, but they have be demonetized in order to be
128:30 Again, the theory is that you magnesium rich brian's through compaction into these
128:35 to cause the harmonization. Okay, those are the popular models. They've
128:42 around forever and everybody feels compelled to onto one of these models to explain
128:49 massive straddle dolomite, that they Okay. The last potential model has
128:56 to do with near surface conditions. the deep barreled organization model.
129:02 what it's saying is that you cannibalize magnesium from other limestone or Dulles stones
129:08 have undergone dissolution or you bring it from deeper baseball brian's. All
129:14 So, think about the gulf of basin, right. We have the
129:17 and weren't around hydrate. That would an example of a potential source of
129:22 based on grinds. All right. then you just move it up into
129:26 overlying carbonate succession. You do that by compaction all flow or by fault
129:32 systems. And and people have argued even on a finer scale, the
129:37 ites become a conduit when they're intersected fractures carrying these fluids, they can
129:42 the fluid sideways to delay metis and try to convince you that in a
129:47 . All right. Yeah. Can dilemma ties if they already have
129:56 No, there's no water I mean speak of and there's no water
130:02 Right? So, yeah. Uh Yeah, yeah. And then you
130:11 you can you can actually later do phase of die genesis on the Dolomites
130:20 maybe destroy some of the hydrocarbon or it off and then bring another phase
130:24 oil and again, So, there a lot of different scenarios, but
130:28 usually the stuff has to be dramatized before it can be charged.
130:34 okay, Okay. So let me me just show you what I mean
130:37 and then we'll take another short break we finish up talking about porosity,
130:42 and dolomite. Uh This this relationship is very common in the rock
130:48 You see this in a lot of diplomatic lime stones. I've prepared the
130:52 photographs here. The one on the is the uh you can see the
130:57 for calcite and then everything that's not as dolomite. And you can see
131:02 of the fabric here, the p and the calcium sphere. Here's the
131:05 paper technique. The same view, taken with the white paper technique under
131:09 thin section. So, the first it does is it sharpens up the
131:13 distribution, right? But more look at what you pick up here
131:17 you didn't see so easily over You pick up the style lights.
131:21 see that? And these skylights are places overland by dolomite. So that's
131:27 timing indicator that that dolomite formed after style light. So that's barreled
131:33 Okay. And this is how you prove your general timing relationship. If
131:40 need to be more precise than you the geochemistry and the Dolomites.
131:45 so let me show you a couple . First example Jurassic smack over this
131:50 the I'm sorry Jurassic from uh parodies France. Okay, let me set
131:56 the street Igra fee here these porous sit down dip from an up dip
132:02 IQ faces. So what was interpreted . Early reflux right of brian's to
132:10 for the demonization. Nobody knew what Dolomites were replacing because here's the normal
132:17 section view. What do you You see cloudy and light. Dolomite
132:23 Where the rams, do you see rooms? Maybe one here, see
132:27 sub angular. This is very typical the crystal shape of Dolomites.
132:32 Very regular shape. Like you see and then you have ferocity of
132:36 But because you can't relate this to positional digest texture. What are you
132:41 to call this porosity? You're forced call it buggy porosity which means it
132:46 nothing to do with anything. You want that pendulum. Might you want
132:51 be able to attach that ferocity back the faces that you can map and
132:56 the boundaries of. Okay, so is actually the this is the sample
133:04 revealed the use of fluorescent microscopy to through the masking effects of the
133:10 Okay. We were actually looking for inclusions in these Dolomites. When And
133:16 have to do that. It really power right to see the these tiny
133:20 oil inclusions. We were looking for oil inclusions. We backed off on
133:24 photo backed off on the on the . And uh this is what we
133:36 . Arrow points to the same Pick up these relic grains. These
133:41 druids and P Lloyd's. Okay. then look at the contact between these
133:47 . There's the future green contact. right off the bat. That tells
133:52 these grains did not get dramatized early pressure solution. Right? Because they
133:58 not be future together after they got . I'll prove that to you in
134:02 minute. All right. So that's first time an indicator. You can
134:06 go back and forth between these lights show that the dolomite crystals overlay the
134:12 of the pressure solution seems So that the timing. Okay. And then
134:18 at the implications here. This is new with sand body. All
134:22 It has a trend. All And it has ferocity. This is
134:26 buggy ferocity. This is what we partial molded ferocity. This is faces
134:31 ferocity. Alright, and then look the fluorescence also picks up on some
134:36 the Dolomites cement. So some of stuff was dissolved. But some of
134:41 dolomite re precipitated the backfilling dolomite All right. So you pick up
134:47 donation effect here of the poor filling . All right. So you see
134:53 we try to work out the We relate everything back to the pressure
134:57 fabrics because we know the relative timing their formation, right? And then
135:03 last example here this is Jurassic smack . This is the lower part of
135:07 Jurassic sequence in Mississippi. This is field called but you do creek.
135:14 sample doesn't have any porosity because it's filled with black bitumen. That's what
135:19 black material is. Normally. The smack over is limestone. It's a
135:25 called brown dense, which is these water pelagic carbonates mixed in with the
135:31 still stones that come from the ancestral of Mexico and but here is stolen
135:37 . All right. And look at dolomite crystals. Uh they there's porosity
135:43 the crystals. But I think you to agree that some of these crystals
135:47 been dissolved to varying degrees. Look the the regular nature of those crystal
135:55 . Right? That's the solution. dissolution fabric here. So if you
136:00 prove the time and organization, you prove that some of this fabric was
136:05 by dolomite dissolution had depth. but here again, I challenge you
136:10 the faces. You can't see any or anything. Here's the here's the
136:15 view again. And what does it up? It picks up all of
136:18 little P. Lloyds and these payloads been future together and I've marked some
136:23 the super grain contacts between the Lloyds. Okay, so the fact
136:28 these P lloyds are structured again means that organization had occurred after the grains
136:34 already been future. Okay, so is barreled organization and some of this
136:40 burial secondary porosity due to dole my . Alright, and again, this
136:46 how we try to get a handle the fabric. All right, So
136:51 gonna I'm gonna take you through a of case studies here later in
136:56 And you'll see I'll build on this . Okay, this is actually more
137:01 than people are given a credit Because they haven't tried to see through
137:05 masking effects of the of the right? Yeah. This is what
137:10 me to no end when I read , these die genesis papers on the
137:17 . They show one picture of the . It's usually just a plain live
137:21 right where they see a cloudy center the dolomite crystals, they say,
137:25 , that's that's all political. Well , but that's not political necessarily.
137:30 mean, you'll never know unless you to look through the masking effects.
137:35 ? But nobody ever tries to do . They just jump on the geochemistry
137:39 they run with the geochemistry to build story. Okay, okay, so
137:47 slide here, we'll take a five break effects of decolonization. Obviously you've
137:52 examples now we're in massive deposition of . I showed you one example this
137:58 this morning. We're perfectly preserved that political Pakistan fabric. Why you get
138:05 versus preservation? That's the $64 I have no idea. Maybe it
138:11 to do with rate of flow through rocks, but nobody's figured that
138:16 And then with respect to porosity every manager that I've come up
138:21 it has no carbonate training thinks that time you go from limestone and
138:26 you get ferocity and there's a diagram your, in your notes and your
138:31 set that I'm skipping over. That the volume change from Dolan from
138:36 Dolomite. When you go from 2.72 gravity to 2.85 In a closed
138:44 you would get 13% porosity and that's managers have this idea that all Dolomites
138:50 porous. Unfortunately, it's not that . Okay, so sometimes we do
138:56 bumps and ferocity. Sometimes we just progressive loss of ferocity with burials.
139:02 that's the challenge. So let's take break. Then we'll come back and
139:06 talk about process development. I think is the most important part of the
139:10 here. Not the models, but uh how the different pathways to across
139:16 evolution. Alright, okay, let's up this discussion by talking about ferocity
139:27 and Dolomites and I'm going to start discussion by taking you through so called
139:33 wisdom to show you what's been established the literature Over the last roughly 40
139:39 in terms of the thoughts about porosity . And then I'll show you some
139:46 of what I'm talking about. And though we don't understand all of these
139:52 , we see him time and time . That, as I said
139:55 if you ever work at Dulles Stone , you should be familiar with some
139:58 these potential pathways for porosity and by permeability development. Okay, so historically
140:08 view porosity development and Dolomites as forming early. Everybody thinks this happens early
140:16 all the models that I just took through our skewed toward early neuro surface
140:21 . Right, So the implication is the the decolonization should be pre compaction
140:29 therefore the ferocity that comes with it be pre compaction. Alright, and
140:34 you do see secondary process he developed the stolen stones, everybody relates it
140:39 leaching of calcium material toward the end the line with respect to dehumanization.
140:45 other words, as you start to dramatize the limestone fabric. The thought
140:50 that during the advanced stages of the remaining calcified material will dissolve
140:56 And that's what gives you you're bumping porosity. Historically, we've downplayed deposition
141:01 controls on ferocity because we couldn't see relic fabric. Right? But now
141:06 have the tools that I showed you see through that fabric and see if
141:11 is an underlying faces controlled and it's more common than people have given it
141:16 for in the older literature. All . And because of that, we've
141:20 forced to describe the associated porosity. secondary porosity as in a crystalline or
141:26 enter crystalline means it's related to the of the dolomite crystals, thug means
141:31 related to nothing. I can't relate to anything. That's why I use
141:34 term bug. All right. But of those terms have no have no
141:40 faces association. Right? As I , you want to be able to
141:44 a relationship of reservoir quality back to deposition of texture. And then with
141:54 to dissolution of dolomite crystals, I've to a little bit of it
141:59 Uh everybody's downplayed. This is a minor fabric. And the rock record
142:05 where is described, it's called digital . Where people say, we start
142:10 with little Romberg dolomite crystals and we leach them out and then immediately back
142:17 him with calcite cement. And where see that they describe that as d
142:23 . And they always related to near fresh water, which I just find
142:28 boggling because I've just said, Heimat cal side and lo my calc
142:34 dissolve in fresh water dole. Am supposed to be more stable than
142:39 So why would calcite dissolved in fresh ? This never made any sense to
142:45 . Okay. Mhm. And for reason, dissolution of dolomite crystals has
142:50 been considered, especially a depth has been considered unlikely because everybody thought dolomite
142:58 such a stable mineral that can never altered. Well, I told you
143:02 doesn't start out with perfect stability. ? Proto dolomite is very unstable
143:08 And even ancient Dolomites never achieve that stability. So uh yeah, I
143:16 given the right conditions, the right of fluid chemistry, elevated temperature.
143:21 older replacement dolomite could potentially be prone dissolution to create reservoir quality. And
143:28 going to I'm going to argue in segment later. I'm gonna do a
143:32 bit of it today, but show on a case study basis that dolomite
143:38 can create major reservoir equality. All . That it's not just early demonization
143:44 leaching of calcite that creates the reservoir . So, having said that,
143:50 me share with you some relationships, see time and time again. Some
143:54 these we understand pretty well. Some these are not so well understood,
143:58 they and they're not unequivocal but there common enough in the rock record that
144:02 should be familiar with these different So, the first point here is
144:08 can increase or decrease, but it on the texture that you start within
144:12 degree of dehumanization and I'm gonna take through a case study or two that
144:17 this. Okay, and then where have what we call by model or
144:23 mobile deposits. This would be of stones that have larger elements and a
144:30 matrix and matrix doesn't have to be . It could be a finer
144:36 So think so. The terms we about rude stone float stone, uh
144:42 sorted grain stone, a pack Right where you have big brains and
144:47 and even a wacky stone. So you have that texture to start
144:52 ? An adult monetizing fluids come What are they going to go after
144:57 ? They're always going to go after final grade material. Right, higher
145:00 area to volume ratio, controls the . This is going to go after
145:05 finer grained material is going to react that with that material and presumably dramatize
145:11 . And then I'm going to show examples where later the larger remaining cal
145:15 grains dissolve out. And if those brains are touching in three D,
145:20 how you create super permissible reservoir Okay, the mineral dolomite is much
145:27 than calcite. So if you can massive demonization with early, relatively early
145:34 development and then you bury that it's going to hold on to that
145:38 a much greater barrel depths than you could do with porosity formed by early
145:44 for marine burial die genesis. And just to jump ahead here.
145:51 is much more brutal than fracture than stones. So it fractures at least
145:58 times more in a limestone. So you can generate the porosity, you're
146:04 going to superimpose fracturing on top of , which enhances the permeability even
146:08 Okay, that's why a lot of goldstone reservoirs are so great. And
146:14 we do see dissolution of the dilemma fabric and I'm going to argue that
146:20 almost always burial and it can be great enough scale to create reservoir quality
146:26 where we see that developed, it's where we have emplacement of late stage
146:31 and hydrates or cal sites. if going back to that initial folk
146:36 land diagram I showed you, they a big point about increasing the magnesium
146:41 ratio to make dolomite, we'll turn around, bring in calcium rich fluids
146:47 where the calcium to magnesium ratio is into a dollar stone, theoretically,
146:53 should make the dolomite unstable and prone dissolution. In fact, that's what
146:57 see, where we see major dissolution fabric. There are always these late
147:03 and hydrates or cal sites hanging around calcium rich fluids coming in. And
147:09 where we see the door of my . Okay, so let me build
147:13 each of these points here and we'll with this diagram, which is not
147:18 like this in the literature, but can put this together from the data
147:21 was published from this paper, which what we did here. So,
147:26 was a chief geologist for Saudi Aramco he published the Aramco classification scheme for
147:34 Jurassic arab D in the same volume done and published his classification scheme.
147:42 right. And so they had their terminology. But it's interesting that towards
147:47 end of his paper, he got a discussion of what happens to the
147:51 D as you progressively dolma ties All right. Because not all the
147:55 D production is from lime stones there can be anywhere from 20 to
148:01 ft of massive Dola stone associated with Arab D in places. All
148:06 And some of that can have great quality. So he discussed what they
148:11 with respect to the demonization effect of arab D. All right, So
148:15 starting point here in this diagram Would a pure limestone here with no dolomite
148:21 20% ferocity. Alright, so capable being dramatized and what they observed was
148:27 the demonization starts to come in. do you see, you see the
148:31 might increase to the right, but at the porosity. The initial phase
148:35 ferocity. Uh evolution is what to the ferocity. So the first phase
148:41 the decolonization actually decreased the ferocity Until get to this magical point of about
148:48 , by volume dolomite. And then , the price increases and what's happening
148:53 there, What's happening right there is remaining calcified material, whether that's matrix
148:58 whether that's larger grains dissolves out, gives you your reservoir quality.
149:05 now that's where you have to entrap hydrocarbons if you don't do that and
149:09 keep bringing in dramatizing fluids, what ? You just plug that ferocity with
149:14 cement and you evolved to dolo tombstone 100%. Okay, so timing is
149:21 . It's always time. Is everything this business, right? Everything has
149:26 be perfectly juxtaposed in terms of setting the reservoir, setting up the
149:32 setting up the migration the hydrocarbons. , so this is interesting. All
149:38 . And there's some more recent papers blogs now where people are saying you
149:42 have to be up to 70, by volume. It could be Over
149:47 around 50 or 6:55 or 60%. the point is the process, He
149:53 you're not creating the process the early you don't have enough dolomite yet.
149:57 right. You've got to dramatize this some degree before you get this bump
150:01 ferocity. Now, I can tell because I've looked at literally I've looked
150:07 thousands of thin sections of Dulles Alright, in my career, and
150:12 can tell you that this is very relationship. Okay, I can also
150:18 you that sometimes you see the do this And it just goes to
150:24 . Okay, You don't see that . Okay, so that's the question
150:30 here is what's causing the bump. ? Do you need to bring another
150:34 in to leach that cal citic Some people would say yes and other
150:41 would say no. You can all it from one fluid or maybe you
150:45 do it at all. All Maybe it's all porosity destructive. Sometimes
150:48 is the challenge. This is a . Okay, so this is a
150:52 relationship but it's not unequivocal in the record. So let me show you
150:57 ahead. Yes. Mhm. 100%. That rock would be the
151:09 would be 80% Limestone would be 80% and 20% ferocity. Right? We're
151:18 off with a pure limestone right? . That has 20% ferocity,
151:23 It's pores and limestone fabric. And we start to bring the fluid
151:29 We start dramatizing and your porosity goes . The amount of calcite goes
151:34 Right? Because you're adding dolomite. it's not till you get to this
151:39 by volume dolomite. That you see increase in ferocity. Okay, that's
151:45 it's saying. Let me show you let me show you the samples.
151:53 right, So you need a host capable of being dramatized in the Arab
151:58 . Arab de deposits that have reservoir are pack stones with ferocity. Mostly
152:03 stones. A mixture of p. skeletal analytic material. You can see
152:08 porosity here to start with the dramatizing comes in, you start to go
152:13 the fabric. Democratic fabric is dramatized . Either matrix or grains. But
152:19 what do the Dolomite crystals do? grow out into the adjacent poor
152:23 So they replaced But they expand by , cement, ation and they start
152:28 the ferocity. So that's why the phases of dehumanization are ferocity destructive.
152:35 . And then you reach this magical of in this case 75,
152:42 And then what do you get? get fabric that looks like this?
152:47 , you get fabric, it looks this. So the implication is that
152:50 remaining cal civic fabric, whether it's or small grains dissolved out for whatever
152:56 to create that ferocity. Okay. course everybody called the center crystal and
153:01 because it's between the the dolomite But I would actually think I think
153:06 actually secondary molding process because you're removing . All right by dissolution. But
153:14 that's a nitpicky point. But this where you create the reservoir quality.
153:18 right in the Dulles stone. Now got to charge it with hydrocarbon.
153:24 if you don't do that, then evolve to this fabric right here,
153:29 ? That's a that's a rock with dolomite note ferocity dollar tombstone.
153:37 And you see you see these little centers here, everybody would say this
153:42 political fabric. Those cloudy centers. huh. You see the cloudy centers
153:52 and that's not political fabric. That's of a P. Lloyd or critic
153:56 has been replaced by dolomite. But you see this in the literature
154:01 the time. People see these little centers, every replacement dolomite starts out
154:05 a cloudy center whether replaces a grain or mud stone and then it grows
154:11 to conclusion free parts of crystals. ? To give you that pattern.
154:18 , you see this in literature, be really wary when somebody tells you
154:22 employable something Pakistan or grain stone or . And we we we've proven this
154:29 several times with the white paper and technique. Yes. 7%.
154:43 Well, that's that's that's maybe you , there's microprocessor all three here too
154:47 you don't see So maybe 15-20% ferocity begin with. All right. And
154:56 you lose goes down as you grow that prostate by overgrowth demonization. And
155:03 you'd leach out the remaining parasitic Yeah. Yeah. And this is
155:10 is very common. I'm not downplaying at all. I'm just saying that
155:15 is a common relationship but it's not . Okay, sometimes this process never
155:21 . You just keep replacing that in critic Matrix or P Lloyd's with with
155:26 and you never evolve any proxy tournament . Yeah, No, this is
155:34 norm. I say this is the for what we see for progressive
155:39 Ization of a of a limestone. . I just want you to know
155:46 doesn't happen every time. That's Okay. No, I would say
155:51 is the norm right now. The is going to be the timing,
155:55 . Everybody wants to interpret this as dehumanization. But let me show you
156:00 from the snack over where it's more . This is the upper part of
156:05 smack over where you get to the sand body systems developed and you can
156:09 the limestone fabric, your moods and cement. And here comes the
156:16 These brighter white crystals here. and they're coming in at burial because
156:24 was already future. In fact, of these crystals overlying the future
156:28 So this is barreled organization. what's it going after? It's going
156:33 the you is because that's all there right. The words are made up
156:36 smaller crystals so they are more reactive respect to replacement dolomite. And so
156:42 go after the outer parts of the . Ids you don't notice that some
156:48 the dolomite extends into the process as cement. So this ferocity is not
156:54 to decolonization. This is the primary . It was modified first by calcite
156:59 and then by some dolomite over gross . When you get again to that
157:05 . I'm sorry that higher degree of . What sometimes happens to the remaining
157:12 material. It leaches out to give fabric that looks like this.
157:18 this is how Greenstone responds to progressive . Whether it's early or late and
157:25 I'm arguing it's late because the grains already future. Okay, when all
157:30 got are grains and no matrix. dramatizing fluids are going to go after
157:35 grains but they're going to go after outer parts of the grains first because
157:40 adjacent to the poor fluid. So that's why you saw preferential demonization
157:46 the outer parts of the U. like you see here and then later
157:50 inner parts they're still cal acidic. you get to that magical,
157:55 They leach out. Okay, so go ahead. It's like 46.
158:06 . Some processes. No, this inner part. This is what we
158:10 inter particle, primary prostate. Between grants. This is deposition of ferocity
158:18 by a little bit of calcite cement by the pressure solution. That's our
158:23 to begin with. And then the come through to dramatize and they go
158:29 the two words and not the calcite because the U. S. Are
158:34 up of tiny little crystals, They're much more reactive than a bigger
158:37 side cement. And then they modify porosity. By by growing dolomite crystals
158:45 extend out and plug some of that to so to make a good reservoir
158:50 you see here you have to hold to some of this primary porosity.
158:55 you plug it all with dolomite you have no reservoir quality most
158:59 Right. Unless somehow you can you tie these isolated molds together by
159:06 which you could sometimes. Right? Dolomites more brittle words. Yeah.
159:13 huh. Everybody says this is cal material, remnant parasitic goods. This
159:19 what's left over. When you get that 80 80% by volume dolomite,
159:24 saying the stuff goes, it becomes , forced to dissolve out or you
159:30 another fluid through to leech it That's the big debate. Okay,
159:36 . That's sick. It could be or 15% porosity to write most of
159:42 here in. This view has been with later and hide writer calcite
159:47 But there are other parts of the going to see these reservoir rocks in
159:50 minute from other parts of the smack where you've got a higher degree of
159:54 process preserved. All right, so this, no molding. Okay,
160:03 you've leeched out something. Okay, ahead. That the last thing I
160:09 to talk about today is the prostate scheme. Sure, yeah,
160:15 So let's let's make time for I hope I think I can be
160:18 by five and get it all but okay, so, I just
160:24 to appreciate this relationship. I'm gonna on all of this with the case
160:27 later. Uh, so, we'll back to this relationship. All
160:32 And then I mentioned the when you by model or poly mobile deposits and
160:37 example from the devonian. These holes to be strom atop roids, branching
160:43 atop rides that were touching in three . So, this is a rude
160:47 with a political grain stone matrix. , So what got demonetized first?
160:53 finer grained matrix and then what leached later. When you get to that
160:58 stage of the organization, the cal stream, it operates. So those
161:03 secondary molds. Again, that's not process molding process because it's controlled by
161:08 dissolution of storm atop words. But grains are touching in three D.
161:12 the definition of a root stone. because of that, these holes communicate
161:17 you end up with what? 1-5 of permeability in these kinds of oil
161:22 . All right. So, this the famous LaDuke reefs in Western Canada
161:27 were discovered back in the 40s. right. This is the re flat
161:33 . This is the beauty of dramatizing of this coarser grain, but by
161:37 or polymer solo for the sorted carbonate . All right. So that's the
161:45 control on decolonization and ferocity. And I mentioned the strength of the mineral
161:51 . If you can create the porosity , you can hold on to it
161:55 much deeper barrel depths. This is example from another smack over field in
162:00 called J field, it's a giant field Over 600 million barrels of oil
162:05 place. And uh, this is old Exxon field. So I've seen
162:10 from jay field, we used to these cores for our training and I
162:18 you see the circular holes. So you think immediately these are what
162:21 woods because I showed you other foods the smack over. But actually this
162:26 a part of the trend that was capable of creating high energy conditions.
162:31 is a restricted and payment uh, this part of the trend and these
162:36 actually P Lloyd's. Okay. And can trace this rock into the undocumented
162:41 equivalent and show that this is originally political Pakistan. So we had P
162:47 right. Most of these are probably pellets. Some of these could have
162:50 me critized dudes With um a critic . What God dramatized 1st. Democratic
162:57 . Right. And you appreciate this early dolomite because it goes all the
163:02 around the grains. What people call informally? They call these necklace
163:08 Right? They go all the way the grains. So this is like
163:11 ice a pack of cement we talked and limestone die genesis. All
163:16 But this is not cement. This replacement dolomite of the Mc.
163:21 And then when we get to that stage. Well, each out the
163:25 parasitic P Lloyd's. Okay. Now at the burial depths here. All
163:31 . The sample is an excess of ft of burial. They're examples like
163:36 in the Mississippi and Montana Of this of fabric preserved to 25,000 ft.
163:45 , This would never happen if this a limestone. In my experience,
163:49 stones get down to about 13, with this kind of early prostate,
163:55 whole system collapses. Okay, so the beauty of democratizing some of this
164:02 . You do it early enough. going to hold on to it to
164:05 greater barrel depths than you ever could with fresh water die genesis or marine
164:12 . Dia genesis. Okay, like , thank you. So it's always
164:20 a misnomer. Yeah, no, , there, there may be my
164:27 do ids. There may be a , it shows somewhere nearby that accounts
164:31 some of these micro ties do is they, if that's what they
164:35 But the core, the core that seen, you can see a transition
164:39 of the field and the same strata level and you don't find dudes,
164:46 find P Lloyd's right burrows political Right? Yeah, that's jay field
164:54 unique to jay field. Most of other upper the upper part of the
165:00 over is mostly productive from melodic For sure. There's no doubt about
165:04 . Okay. And then with respect fracturing the ah, It's pretty,
165:13 well established in the literature going back the 70s that if you take a
165:18 and dolomite and you buried to the depth or you put it in the
165:23 tectonic dealt with compression, the dolomite fracture greater than four times out of
165:29 lime stones. Okay. Uh, is core from one of the,
165:35 of Mexico's giant oilfields. Uh, forget the name. I'm not sure
165:41 even told me, but I taught course down there for pemex back maybe
165:46 years ago. And then at the of the course, they laid out
165:49 bunch of their core for us to at as a group. And I
165:53 this relationship here with the lighter fabric the darker fabric and I asked him
165:59 get some acid. We put acid the lighter stuff into fist, right
166:03 the bat. It's limestone. Put on this, it didn't fizz until
166:06 scratched it. All right, says made and look at all the look
166:11 the high intensity of fractures here, any fracturing in the adjacent limestone.
166:16 good fracturing in this dark for Dulles fabric, it just states the obvious
166:21 this diagram. Right, that the stone fabric will fracture to a greater
166:26 . So, if you can generate , right? Even if it's isolated
166:31 porosity in the subsurface, you could that stuff together with fractures and have
166:37 reservoir quality. Okay, pretty deeply . Okay. All right, so
166:49 me just summarize what I've said here we have a by mobile textured fabric
166:54 finer grained matrix, whether it's mud find sand sized material gets replaced first
166:59 dolomite, and then later during the stages we see the Green speech
167:04 And most people, including me would most of that stuff that leaches out
167:09 cal siddiq. Okay. For whatever . All right. And when you
167:13 the leaching, you always see the of the pores leached out with no
167:19 of dolomite crystal dissolution. Alright, , you see what's happening here?
167:24 the fluid goes after the matrix and it starts to go out after the
167:28 parts of the grains. And that's you see the centers of the brain
167:32 always leached out at the end of line. Okay. Because of that
167:36 front coming through. All right. I think in your notes, I
167:40 a model there from Western Canada, shows that. All right. And
167:44 course, the controversy in the carbonate is can you do this from one
167:50 ? Or do you need to One to delimit ties and one to
167:55 . And I think you can do from one fluid because sometimes, you
167:59 that the other fluid everybody invokes is water, which makes again, Absolutely
168:03 sense. Why would the calcite leach in fresh water? But that's what
168:07 always invoked. But certainly they're evaporating where some of these dola stones have
168:13 process development. How would you ever another fluid in there. Right.
168:17 all one fluid during the course of . So, I think you can
168:21 it from one fluid. All But some people think you need to
168:26 , the bigger controversy is, can completely dolma ties the limestone and then
168:32 another fluid through to leach out some that dramatized fabric to create reservoir
168:39 And the the uh the answer to I think has to be yes.
168:43 right. Because you see it right in this Mississippi an example, you
168:48 the dolomite crystals that replaced the precursor and then look at the look at
168:53 . Some of the crystals are not at all. Then you see parcel
168:57 , more complete dissolution and then total . How can you do that without
169:03 the dolomite? I don't see how can do that. Okay, without
169:07 fluids being involved here, One to monetized, and then another fluid to
169:12 through and create that reservoir quality. , so let me just show you
169:18 quick example of of of the barrel on a bigger scale. But let
169:23 start this discussion by going back to standard or norm that I think operates
169:28 the rock record. And I'll do by this example right here from the
169:33 in Western Canada. This an outcrop a little devonian reef complex. These
169:40 what we call boldest Strama top They're the equivalent morphology to the head
169:45 will talk about for modern reefs later . And then you see a darker
169:50 in here. This pendulum monetized. , so the white is dolomite and
169:56 darkest dolomite and the matrix. And course everybody assumed because it's a darker
170:01 , that this is Mick. Right. To spend dramatized, except
170:05 you look at it with a white technique, that's a political grain
170:09 Okay, and so this is just of those polly mobile or by mobile
170:15 with bigger skeletal grains and a finer of carbonate sand. So, what
170:20 to acclimatize 1st? That Right? then the fluids go after the outer
170:26 of the grains. And that's why get this rind of dolomite around the
170:30 of these storm atop roids. And what happens? You leach out the
170:35 , presumably while they're parasitic during that stage. Okay, so to
170:40 that's the norm. All right, expect the center to be leached out
170:45 I would have expected this to be acidic. And when you look along
170:48 edges of that porosity, you look the dolomite crystals there conform herbal,
170:54 don't see any dissolution of the Okay, so to me this is
170:59 norm. Okay, now, let show your case study from Western
171:04 where we have identical fabric. But think you have to conclude that after
171:09 rock was demonetized. It got leached to varying degrees. So here's the
171:17 example. It's a different age sequence it's the same kind of faces bulbous
171:23 . Top roids, political Greenstone This whole rock is completely replaced by
171:31 . The black is a bitumen Right? That lines some of the
171:35 . Now remember in our previous where was the big ferocity was in
171:39 center? The strong must operate. more of the process on the outer
171:44 of the grain. Alright. It's confined to the center. And when
171:48 look at the look at the look adjacent to the ferocity, you
171:55 evidence of dolomite dissolution and you see random distribution to the secondary process.
172:01 not confined to the centers of the . Okay, so that observation and
172:06 dolomite crystal dissolution suggests that this rock first dramatized and then another fluid came
172:13 to dissolve it out. Okay, another faces in the devonian that shows
172:19 same relationship. These are the remnants little stick like branching storm atop where
172:24 called amphora. They sit in a political matrix. So you can see
172:31 the matrix has been demonetized and all the grains have been demonetized.
172:38 there's not an ounce of calcite in rock. But then look at what's
172:42 to the anthem flora. Some of um for Pora, the green arrows
172:46 to that some of the alfa Pora pristine preserved micro structure where there is
172:53 no dissolution effects. So the whole just got replaced by dolomite. But
172:58 look at the transition. Look at red arrows. You see partial
173:03 But it's random, right? It's sometimes in the centre sometimes on the
173:08 , and then look how it transitions the blue. All right. We
173:12 more complete dissolution. All right. , the dissolution is not confined to
173:18 centers of the brains. It's all the place within the grains.
173:23 you see evidence of dolomite dissolution. the corrosion of the dolomite here.
173:28 would not see this in that previous that I showed you with the storm
173:32 red cross in the middle of the atop. Right, Okay. Everybody
173:38 what I'm trying to say here. trying to say that these rocks got
173:43 first to varying degrees. I they got dramatized all the way.
173:48 right. Because you don't see an of calcite left in those rocks and
173:51 had variable amounts of ferocity. They to have ferocity and perm And then
173:56 fluid came through capable of dissolving that . Okay. To create the final
174:03 that now is oil and gas Alright, so, that's stolen my
174:09 . And this is a big scale give you reservoir quality, right?
174:15 if you play the game of working patrol graffiti and you can support this
174:21 the geochemistry. The timing of all this dissolution is burial. Which really
174:27 sense when you think about it, , burial conditions of water is going
174:30 be warm or hot or hydrothermal. right? And if you get the
174:35 degree of acidity or you get a rich fluid, then you're going to
174:40 this solution of these dramatized fabrics. you can prove that his burial because
174:44 see the secondary processing, the stolen again, is preserved along the style
174:49 or cuts the style lights. It's same timing relationship we talked about
174:54 Sometimes you see the grains are already future together, right? But then
175:00 . So we said that had to barreled all night. So the subsequent
175:04 of those brains has to be a dissolution. And fractures are a big
175:10 of the story. The fractures feed these areas of secondary porosity development.
175:16 when you look along the fracture you see the dissolution of the
175:20 So that tells you you're delivering fluids were capable of dissolving dolomite.
175:26 so you see the sample here. you look at them a critic
175:30 the finer matrix in here and thin , it looks like this. And
175:36 see cloudy and light dolomite, you the porosity. I think you have
175:40 agree there's still in my dissolution You see the corrosion the dolomite
175:45 but you can't see any rally grain . But here you use the white
175:50 technique. Look at the what you up, you pick up the outline
175:54 the smaller fragments of an for poor democratic matrix. They are future
176:00 So that's the key timing indicator that is burial replacement dolomite. And then
176:06 come in and you leech it out look at the random dissolution is not
176:10 to the center of the grain. all over the place. And you
176:14 the evidence of dolomite dissolution. See what I'm saying here to
176:20 burial, dissolution of that dramatized Okay, on a big enough scale
176:26 create reservoir quality. And if you do it at this scale, why
176:31 you expand it to a bigger Like you see here and create the
176:36 what are called zebra dola stones? dolomite. Is this alternating light and
176:42 dolomite? The dark dolomite is riddle style lights and look what happens to
176:49 skylights. The style lights just die into this buggy porosity. Then you
176:54 them up on the other on the side. All right, so this
176:59 the grander expression of dolomite dissolution. this is where I think the style
177:04 play a role here. The fractures in, they intersect the style lights
177:09 dissolving fluids move sideways and they promote fabric. And this must be the
177:15 because we have tectonic vertical skylights with fractures and intersect like this and the
177:23 fabric goes this way. Okay, I'll talk about zebra dolomite in a
177:31 . All right. I mean saddle saddle Dolomites, a definitive barrel
177:36 All right. It's not all It can be replacement and poor filling
177:42 . But if you agree that you do it at this scale, why
177:45 you continue to grow a bigger dissolution ? In other words, grow bigger
177:50 in the subsurface. In other evolved to a situation like this where
177:56 process system was big enough to get collapse. So here's the Brescia that
178:02 see associated with the sequence and These were interpreted as early near surface
178:09 . But the fabrics don't make any because these these dolomite classed are riddled
178:16 style lights, but the style lights all different angles to each other and
178:20 the horizon. So the arrows are to the style lights and the different
178:26 . Okay, you can't do this early cursed and early appreciation. You
178:33 if you do that and bury what's your sigma? One direction?
178:37 like this. Right? All your light should end up parallel to that
178:43 perpendicular to that principle stress direction. the style lights are all different angles
178:49 each other and they're rising. So implication here is that this rock got
178:55 as a limestone underwent pressure solution got by dolomite. God leached out to
179:01 enough scale to create a hole big for solution collapse. So if that's
179:07 case this is a burial Brescia. . And this is why I said
179:11 have to be careful about appreciation in rock record by itself. Now it
179:16 prove anything. Just like secondary Doesn't prove freshwater die genesis.
179:23 Yeah. So this is this is you differentiate the relationship. Look I
179:31 are off of his name. Uh . Mhm. And then this is
179:41 this is what I'm talking about. right, here's the cartoon,
179:45 This is what we see in the . The breadth of class at
179:48 Different angles to each other with the lights at all different angles. If
179:52 is early for in Britain you buried . The style. It should all
179:56 up uniformly like this right Perpendicular This direction. The only way you can
180:02 , the only way you can explain is being early cursed is too bury
180:07 rock right, pressure, solve dramatize it and then pop it back
180:12 to the surface and do near surface . But not in Western Canada.
180:17 no evidence of yo yo tectonics. , everybody appreciate what I'm saying,
180:23 don't have to believe me but at appreciate what I'm saying here. This
180:27 barrel appreciation. And the caveat here when you go back to the rock
180:32 and you look at these burial breaches some of these have ferocity still and
180:36 and produce. You have to be about saying that's near surface curse.
180:41 not good enough anymore. Just like process is not good enough to say
180:45 all fresh water die genesis right? I showed you three different ways to
180:50 it now. Now I'm showing you way to make barrel Brescia.
180:55 so the details are published. Uh got those on blackboard if you're interested
181:01 going and looking at the core in section data that proves these relationships.
181:06 the key part of the story here all of the stolen my dissolution is
181:11 . They feed in the fluid. know that they're either acidic or calcium
181:16 because we see this solution of France lot of dolomite along the fracture
181:21 Okay, so that's a key part the story. Uh huh. And
181:27 to finish up what are the drivers barrel this solution? All right.
181:31 got really two mechanisms here passage of rich or sulfate rich brian's right to
181:42 either late stage cal sites or late and hydrates. Alright, calcium
181:49 And if they do it late they're to be warm or hot or hydrothermal
181:53 increases the reactivity or thermo chemical sulfate Which generates H two s. generate
182:00 create sulfuric acid. Okay, so let me introduce you to TSR the
182:09 , this is very simple equation is . You need sulfate in the
182:14 You either bleed it in from an evaporated sequence or you locally dissolve some
182:19 your evaporated minerals. You need hydrocarbon the system. That doesn't mean you
182:26 mature oil. Any organic material is hydrocarbon. Right? And on the
182:32 of its composition. And so if have that any organic material, it's
182:37 to react with the sulfate because you're to and you need an H.
182:41 . S. Catalyst to do But you're going to start generating that
182:44 the breakdown of any hydrocarbon In the . And so this is considered a
182:49 temperature reaction, 80° is the minimum . What do you do? What
182:56 you do is you generate more H S. So HS is both a
183:01 interaction byproduct. But then you do you produce a series of policy sulfide
183:07 . This is where minerals like Marcus site galina, Saleh.
183:12 come into play. Okay. And some of these policy sulfides get down
183:17 down to native sulfur. Okay, when we invoke TSR usually we see
183:24 of late stage dissolution. We have these relationships met. But then we
183:30 see these associated sulfide minerals or native associated with that. Okay. And
183:36 people think TSR is associated with hydrothermal . All right. Remember the definition
183:43 hydrothermal dolomite is that you have to geo chemically that that dolomite which is
183:49 saddle dolomite precipitated at least 5 to degrees At a temperature 5° or 10°
183:57 than you would expect for that burial . Right? So that implies hot
184:02 coming through. Don't fall into the of saying because I have saddle
184:08 I had hydrothermal fluid. All everybody does this in the literature and
184:13 bogus. Alright. That's not proof . All right. There's no question
184:18 dolomite is a barrel dolomite. And it never on the geochemistry shows
184:25 it never precipitates lower than about 80 , but that's not necessarily hydrothermal.
184:31 , so don't assume a saddle dolomite always hydrothermal and we call the saddle
184:37 because the curvature of the crystal that is not due to pressure,
184:42 due to a temperature effect. That's distortion of these barrel Dolomites as they
184:49 at depth. Okay. All And then, so dolomite dissolution fabrics
184:55 we see it in these, in dollar stone sequences. Sometimes it's related
185:00 emplacement of late stage and hydrates. right, we get the stolen stone
185:06 with the emplacement of late stage and . We get fracture planes that feed
185:10 that zebra dolomite that are filled with . That's a common thread. Another
185:16 thread here from Devonian and Russia. see obvious crystal dolomite dissolution and then
185:23 cores are filled in with late stage hydrates, we know they're coming in
185:27 because we've analyzed them biochemically and then last example here from the Permian in
185:32 texas, this is part of the Andreas, which is the big oil
185:37 from a carbonate perspective. And this to be part of a large few
185:44 foraminifera, the God dramatized and then can see all the replacement Dolomites started
185:51 leach out and eventually all of this to create complete molds of the
185:56 Well, the common thread again is stage and hydrate cement, where we
186:01 see a lot of anhydrous cement, don't get the dissolution of the dramatized
186:06 . Okay, so food for thought , you need drivers for the
186:11 You either do that with the civic or you do that with calcium rich
186:15 that are hot or hydrothermal. All , All right. I'm gonna apply
186:23 of this to our case studies, just laying it out here.
186:28 Let's take a little stretch break. got about 20 minutes, I think
186:31 minutes, I think I can get our discussion of the porosity and we'll
186:36 it a day. Okay? But a little stretch break for a few
186:39 and then we'll finish up and we'll on schedule, believe it or
186:44 So, that's great. The Last on the agenda is lecture eight,
186:56 is carbonate porosity classification schemes and this uh they're they're a bunch of different
187:04 that have been published since Choquette and 1970. And uh I've alluded to
187:11 of this in the right up that gave you. All right. And
187:14 talked about some of the pitfalls of other classification schemes. I'm going to
187:19 through the Choquette. And pray scheme it's even though it's old, it
187:23 has valuable, provides valuable information about quality, reservoir potential. And
187:30 you can see the layout here. you have to ask yourself a couple
187:34 questions. First question you ask is porosity primary or secondary. Alright.
187:41 means that forms by di genetic All right, pressed. Primary means
187:46 exist at the time of deposition. then the second question you need to
187:50 is that fabric selective or not fabric ? Is it tied back to deposition
187:55 dietetic fabric or it's formed irrespective of and die genetic fabric? All
188:01 So, let's start over here by . All non fabric selective ferocity is
188:07 . So fractures. Okay. And don't contribute a lot of porosity
188:13 Their role is to improve the permeability to 10 times. So, this
188:18 of fractured reservoirs, like people apply the time to the austin chalk.
188:23 a misnomer because the fractures don't add ferocity to account for the amount of
188:29 produced out of those rocks. All . And you see the symbology on
188:33 right here, people use this encore and things like that fractures that gets
188:38 larger called channel pours channel pores, gets solution large, big enough for
188:42 person to walk into cavernous ferocity. . And then there's this term
188:48 the most misused term in carbonate but blogger calls any funny shaped hole
188:53 bug. First of all shape is the criterion, right? That's secondary
189:00 . Where you cannot demonstrate any relationship deposition or diabetic fabric. There's no
189:06 connotation. So you can have micro porosity, you can have macro fungi
189:13 leading to what cavernous ferocity. So that's how you should use the
189:18 bug. All right. And then here, fabric selective most of these
189:24 most of these terms are primary inter between the grains at the time of
189:31 . Enterprise particle within the fossil fossil itself. And then what would
189:37 the next primary port type finessed Remember I defined us as a primary
189:42 type. Some sort of gas or holds up in that process at the
189:47 of deposition shelter porosity of big shell down on the sea floor. He
189:52 , parachute underneath the shell. Who . It's so uncommon. It's usually
189:58 with calcite cement, but it's part the classification scheme. And then growth
190:03 is a modified form of inter That some people will apply to the
190:07 structures where they see intertwining of the with ferocity between that it's more than
190:14 to call that inter particle. But people will say it's growth framework.
190:19 . And then to secondary port types that are fabrics selected melodic where the
190:23 of the dissolved grain is still Right? You've seen lots of molded
190:29 now and then enter crystalline is also to be fabric selective. What they're
190:34 is the growth of the crystals in replace of limestone creates the ferocity and
190:41 why they call it fabric selective. I told you, I actually think
190:45 porosity is secondary melodic related to dissolution matrix. But you know, let's
190:54 leave it simple here and call it crystalline due to the processing between the
191:00 crystals guarantee. United 5% of the published. You're going to call that
191:05 crystal and ferocity. Okay. And you see some down here that are
191:10 selective or not. Some are some are secondary. So shrinkage cracks
191:15 tidal flats. That's primary but not selective borough structures. Not fabric
191:21 The primary I've never seen shrinkage cracks in the rock record. You do
191:26 bureau porosity preserves sometimes. And then . Right? That would be fabric
191:32 where the board goes after individual That would be primary fabric selective.
191:37 then Brescia would be non fabric secondary . All right. So let's just
191:42 through the cartoons here to illustrate Right? Very simple relationship. Inter
191:49 . Excellent reservoir potential. Right. the reasons we said before, not
191:53 highest ferocity is, but the greatest is to begin with. Here's another
191:57 modified by uh some freshwater calcite sedimentation talked about before. So this would
192:04 inter particle porosity correct? It was there before the cement grew into
192:11 This every particle, there's no. crystalline. it's not in a
192:19 right? Because it was their first the cement just grew into it.
192:24 there's still primary inter particle porosity. . And then the inter particle porosity
192:32 showed you this example before with the pod. The black is all primary
192:38 . Inter particle over here. Intra here may not be as effective
192:43 Because it's isolated. So sometimes you to connect it with fractures or you
192:47 to dissolve out some of that Another example the tabulate corals intra particle
192:54 . Okay. And then growth framework an example from the devonian. These
193:00 branching stream atop roids in growth And you see ferocity preserved between that
193:07 by a little bit of segmentation. can call that inter particle porosity,
193:11 people will more specifically call it growth . Okay, so that jews almost
193:17 just limited to these riffle frame stone . All right. And then shelter
193:26 . There's a big conch shell that down on the sea floor. You
193:29 air underneath it. That shelter Okay. Usually as I said,
193:34 in with cement later on. Not effective anyway because it's not well connected
193:39 then financial porosity. Most financial ferocity funny shape. So it gets mischaracterized
193:45 the time as buggy ferocity because of funny shapes, most financial processes horizontally
193:52 . It tracks the bedding planes, sometimes it goes vertical. So don't
193:57 surprised to see that that's like a escape structure where the gas goes
194:03 And as I said before, there only two environments where you can produce
194:07 proxy. One is on tidal flats you have the crinkly laminated, strong
194:13 fabric where the sign of bacteria dissolves creates gas and some of that gas
194:19 trapped along the bedding plane. Or of it goes vertical like you see
194:24 . Okay, so that's one environment make finessed real ferocity. The other
194:29 is in a beach complex. Remember beaches general seaward dipping beaches parallel plane
194:36 stratification. Right? But the waves across that beach profile. They forced
194:42 into the sediment. So most of trapped air lines up again, mimicking
194:48 parallel stratification. This is finessed real . Again the mud loggers call this
194:54 all the time because it's funny Right? And then fabric selective mold
195:01 shape of the grain that's been dissolved is still preserved. You can tell
195:04 was a gaster pot or a Here's the building stone. When you
195:09 out of here. Today, you take a look at the outer part
195:11 the U. H. Buildings. all this cretaceous limestone from central
195:16 These are big pecan shells and you see little gastro pods. Here's another
195:21 that shows some of the dissolution of both the gastro pods and the clam
195:29 then section view. All right, a gastro pod leached out.
195:34 So, the leech part is called molding ferocity. And then what would
195:38 part of the what would this process be called? Primary intra particle
195:48 Right. A mixture of both. , so, you see that that's
195:52 problem. That's where the organism That was the skeleton that got leached
195:57 . So, that's the secondary molding . That's the primary inter particle
196:03 Alright, yeah, yeah, mold . Secondary processes due to die genesis
196:18 . Yes. Primary inter particle and Molik. Okay, so, and
196:25 here's another example from a reservoir in Asia. These are molluscs and coral
196:31 with the mc right envelopes, molding or to be more precise, you
196:37 , maybe you want to say personal process if it's not completely leached out
196:42 , you're trying to convey what you . All right. And then what
196:45 this be right here, correct? inter particle process. The that's what
196:53 is the ideal reservoir, right? got secondary processes for storage and then
196:57 got primary porosity with permeability between the to deliver some of that hydro
197:03 Okay, sure. Cross Yeah, almost yeah, there's a possibility that
197:12 isolated that that's not connected. But this stuff gets connected. Usually their
197:17 to leak the hydrocarbon out. So, I mean, this is
197:21 really good reservoir in Southeast Asia and tertiary. Alright. All right.
197:27 let me make a comment about this porosity development a lot of times.
197:32 confined to the grains like you see . And this is a finer scale
197:37 effect. All right. So this molding ferocity, But it's 10 point
197:41 ferocity or more precisely, I would it micro multi prostate. Okay.
197:47 some of this you can't see without white paper technique here in the sense
197:51 you can see this slightly darker blue . Now, here's the issue in
197:58 the literature, right? People see porosity confined to the grains and what
198:03 they call that, correct? And incorrect. Alright, why is it
198:10 enter part intra particle ferocity all Right. That's right. It's secondary
198:20 . Right? You It's don't start with ferocity like this on the sea
198:24 . That's why you don't call it particle. But this happens all the
198:29 in the literature. Just drives me . All right. That you see
198:32 call this intra particle, which means That's not primary that there is no
198:40 is no secondary enter particle, It's defined as a primary port
198:46 It exists at the time of This did not exist at the time
198:50 deposition. Okay, this is In fact, this is burial this
198:55 because the woods were already future right? And there's no cement between
199:00 grains. There's no cement around the solution seems All right. And and
199:07 is this is important phenomena that you to be aware of. This is
199:11 to get us into our log response later on a couple of weekends down
199:16 road, but I want you to in some of these grain stones that
199:22 you evolve a bi modal porosity system you develop microprocessing the grains and you
199:29 effective inter particle process in between the before the system gets charged with
199:36 All of this process is filled with . Right? The microprocessor filled with
199:41 . The inter particle process filled with and then when you sweep in your
199:46 is going to displace the water. the only water that gets displaced is
199:51 water and the inter particle porosity and doesn't get displaced in the micro porosity
199:58 of capillary effect. Alright, it's water. And so what do you
200:03 up with, you end up with in the inter particle porosity? Water
200:08 the micro porosity. But when you your resisted any logs, right,
200:13 is the current going to react It's going to react to the water
200:16 the micro porosity. It's going to it's going to calculate low resistive,
200:21 ease and you're going to back out high water saturation. Yet these are
200:26 famous examples where where look at the at the numbers here, uh They
200:36 1-10 OEMs right, but they produce water free. Okay, it's irreducible
200:45 . A lot of companies walked away these rocks and this is you're asking
200:48 the Sligo? This is the Sligo east texas and Louisiana. All
200:56 And a number of companies walked away these reservoirs. They found the
201:02 But when they looked at their reasons long stern, that's water wet.
201:06 . We thought that's water wet. then Amoco figured this this relationship out
201:11 in the 70's people realize, wait minute. All this water is bound
201:15 the micro porosity in the you it's not going to produce The oil comes
201:21 water free. Okay. Even though calculating 70, water saturation.
201:28 So that's an important relationship to to aware of in these carbonates systems.
201:34 then enter crystalline is what it right? They say the porosity is
201:38 by the undergrowth of the dolomite Here's an example from a big gas
201:44 off of nova Scotia called panic And you can see the dolomite crystals
201:51 the purple here is a faded blue . All right. And it's been
201:57 by some calcite cement which is the looking or register looking material here.
202:03 whenever you see porosity between the dolomite , everybody's going to call that inner
202:08 and ferocity. And I don't I care. I mean I don't have
202:11 problem with that. But what else going on here? What's happened to
202:17 dolomite. Look at that. See . See the dolomite crystals being partially
202:24 out. What would you call that . Okay. Mhm. Good,
202:31 . There's no term called intra Okay, so in using their classification
202:38 , you have to call that molded and you would tell people what it
202:42 . Right? The secondary molding process by partial dissolution of dolomite, it's
202:47 common in this view. Look at all of us, for us to
202:50 his secondary personal melodic dissolution some of dramatized fabric. Okay. And look
202:56 the common thread again, late stage sites told my dissolution, but I
203:01 talking about before. Right. And analyzed these are these are high temperature
203:06 sites. They come in very So hot fluid, calcium rich fluid
203:12 dissolution. And then McGee ferocity, I said, there's no size connotation
203:18 uh g ferocity. It's just you establish a relationship between the ferocity and
203:25 deposition or diabetic fabric. So, good example of buggy process, you
203:30 be the zebra Dolomites that we just about from the devonian. You can't
203:35 this back to de positional grain fabric anything. Right? It's just part
203:41 scale. This solution cuts across the of digest fabric and if that gets
203:48 large enough that will evolve into the process that we're going to talk about
203:53 a minute. Okay, so this non fabric selective secondary property development fractures
204:00 same thing. Right. And most are vertical, sub vertical because your
204:06 stress direction again is like this. . And again, most fractures don't
204:12 a lot of ferocity. They improve permeability and then realize that not all
204:18 of vertical sub vertical, they can what horizontal or they can be cross
204:24 if they're tectonic in origin. When you see cross cutting fractures,
204:31 has to be a compression stress component create that. If you see horizontal
204:36 like that that are filled with cement natural fractures, that's tectonic. Sometimes
204:43 see fracture planes that are cemented that contorted like that. That's compression will
204:48 . Okay, So if you're not a full belt, where are
204:53 You're close to a major strike slip wrench fault. Okay, so we
204:58 actually use the tectonic fractures to get clue about our local tectonics and what
205:04 they may have on the carbonates. . Not just from an entrapment
205:08 but maybe from a die genesis vertical fractures do not add a lot
205:17 enough volume of ferocity. They only one or 2% porosity units.
205:24 not enough to account for the hydrocarbon . Mhm. Excuse me. In
205:32 so called fractured reservoirs. Their role to improve the permeability up to 10
205:37 . Okay, you still have to matrix porosity that's drained by these fractures
205:43 account for the amount of oil and produced. Okay. And then fractures
205:50 gets solution larger called channel pours. never seen one in my life.
205:54 I don't have a picture to show . I've never seen anybody show a
205:57 The so called Channel four channel pores bugs that gets solution large big enough
206:03 people to walk into would be example of cavernous porosity. Okay.
206:13 . Mhm. I want to see comments that the channel ferocity.
206:26 If it's connected. Sure. It's I've never seen anybody demonstrate that,
206:31 it's part of the classification scheme and I can show you is a cartoon
206:35 I've never seen a natural example of . But certainly I think there could
206:41 situations where some of the fractures are acidic fluid. Right? And they
206:46 solution enlarge and continue on and be . Good permeability. Yes.
206:55 All right. Let's leave it at . I think we've covered what we
206:58 to cover for the for the the point point. The seminar were caught
207:04 . We're on schedule. Okay. hopefully I'll remember to keep my computer
207:12 . So yeah, what I'm gonna is I'm going to load some more
207:18 onto blackboard. Okay. And uh either tomorrow night or sometime early next
207:28 . We have we have a first on saturday. Right. So,
207:31 will I will tell you what I'm to expect you to have a firm
207:37 of. All right. It will related to everything we've talked about up
207:41 this point in the seminar, Yeah. Nothing that we talk about
207:45 friday will be on the exam next . Okay. So nothing next friday
207:51 be on the exam the next We're just going to cover these first
207:55 sessions. Okay? And will be combination of you write the answers or
208:01 will be some multiple choice. And like to do bonus stuff too.
208:06 right. So, you know, see how well you paid attention to
208:12 of my stuff, but uh, just take it from there. It's
208:17 20% of your great. All So, yeah. Right. So
208:26 a good week and let me turn
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