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GEOL 6381 Petroleum Geology - Feb 20 2023
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00:01 See this way, you guys can this too. If you really think
00:05 need to. Uh when I, I've done a professional Masters program,
00:09 always do this. We had recordings face to face. We didn't always
00:14 streaming until COVID. Of course, came up with a good way and
00:17 teams picked up on it. And for some reason, this, there
00:21 go. OK. It looks like there. Oh How do I get
00:37 of that? Oh They don't give handles to. OK. That's close
00:58 . OK. So don't want to this for the reporter. OK.
01:12 that matter of that, OK. the first two uh basic logs that
01:25 looked at were of course the S log and the gamma log and
01:29 the general characterization for them is they're rock tools. They're trying to
01:34 us discriminate primarily between sandstones and but they can also help, help
01:39 with some other things like carbonates and and all that kind of thing.
01:43 uh but mainly they were designed for sand shale sequences in the Gulf of
01:48 coastal point and uh historically and uh everything else has been kind of
01:55 a learning and modification from that original . And now there's all sorts of
02:01 and, and computer programs to uh all that information together. They've created
02:07 things called nomograms that helped you read different values. Uh If you had
02:13 uh variables in your, in your , uh depending on the rock types
02:19 have been complicated, the fluids might been complicated. They may have been
02:23 phase um that sort of thing, , wet, oil, wet
02:29 all sorts of things to help to help them, uh figure out
02:32 exactly what it is. I'm not if the new algorithms these days are
02:38 better than when we had them uh they got back into uh Schlumberger or
02:44 Atlas or somebody like that. And uh started doing things. But uh
02:50 , uh uh you can run a now, get it printed out,
02:54 interprets everything, the mythology, all of stuff. And most of the
02:57 it's right, but I gotta tell it's not always right to remember
03:02 So it's always good to look at uh the mud loggers uh log and
03:06 sort of thing to make sure the are hitting it uh with all the
03:10 that you uh that you need. . And of course, if you
03:16 um archive data from some of these wells, they often call legacy
03:24 Or just, just really old they may or may not have had
03:28 digitized. We do have tools now digitizing, uh, raster logs or
03:34 copies. And, uh, the is relatively simple. A but over
03:40 past 20 years I've been trying to one graduate student to digitize the set
03:46 logs that they're gonna work on and can't get one to do it.
03:49 just, it's just too much work the modern person and, uh,
03:54 sure why. But, uh, know, they have these things where
03:56 just feed it in there and then pull it up and, you
03:58 you have to adjust these logs because slip, they slip on the tractor
04:02 and all that kind of stuff. if you have, and if you
04:04 digital, it's, uh, L S files. It's, it's all
04:07 . It's, you know, it's all straight and, uh,
04:11 uh, justified. But, if you have a digitization of
04:15 of a log that was printed out , then, you know, you
04:19 to do some, a little shifting whatnot to, to log sometimes goes
04:24 this and then a couple of pages it's gone like that. And,
04:28 , they call, I guess they it justify. It's kind of like
04:30 you're doing, um, G I and, uh, you get different
04:34 maps and you're trying to put them in one map, same kind of
04:40 . OK. So, but the thing is the fluid tools and the
04:43 tools, just like the rock they can help you figure out some
04:48 about rocks and some things about But the primary purpose of these originally
04:52 fluid tools. And uh and of , uh the most important thing was
05:00 be able to distinguish a formation that oil and, or gas versus a
05:05 that had just uh salt water, is what we normally see at the
05:10 that we're gonna be drilling. And I mentioned the San Jorge Basin reverses
05:15 lot of the lacustrine basins have reverse and, and uh any time you
05:21 uh something near a coastline, you have uh especially where there's tides.
05:26 can have uh uh the groundwater can incursions of saltwater. They have saltwater
05:31 just like you get in an It's uh not quite as pervasive,
05:36 doesn't move as far in as something in a river or an estuary,
05:40 channel of an estuary. Uh but still can permeate through the rocks
05:44 and affect it. So you could have alternating layers of salt and fresh
05:49 . Um I worked uh in South . I probably had um The subsurface
05:56 I was doing. I probably had and 40 water wells uh with uh
06:01 P gamma and resistivity. And uh had uh lots of uh freshwater
06:09 uh kind of layered between um sometimes salt saltwater uh aquifers. And so
06:17 , it made it complicated when you it, especially the S P log
06:21 it just reverses the signal. And we did have uh a fellow
06:27 he was a first from Cambridge. may have heard of it. It's
06:31 in the UK. And um he correlating pliocene sediments to cretaceous sediments because
06:39 log looked right, but it had reversal in it. And uh when
06:45 try to explain it to me, says, it says something like
06:50 Uh I'm a first from Cambridge and not gonna try to fake his
06:55 Uh a first from Cambridge and I think wrong things. And I
07:00 well, how about this? It's bad idea to correlate those 22 units
07:05 . Can you go with that? kind of broke him down a little
07:09 . But uh but nevertheless, um isn't always, but there always will
07:17 a certain amount of log interpretation is art. And uh and it,
07:23 it, it's uh highly dependent upon every variable, including the ones you
07:29 think are important. And uh any you see a log, uh for
07:35 , if you work out in say the, the shelf of the
07:38 of Mexico, you're gonna have great the, all of these tools work
07:43 for that. And you can see gas, see sand shale, no
07:47 . But in other parts of the . Um and even in different parts
07:51 the, the coastal plain, uh can have issues with it.
07:59 And uh these things are all you know, um formation water is
08:03 salty, especially at the depths we're at. And so it tends to
08:08 conductive, conductive means low, low , conductivity and resistivity are just the
08:13 of each other. Uh Sometimes I'll pointing at a conductivity log and telling
08:18 , look, the resistivity has gone or down. And that's because,
08:21 know, you just automatically read it . And uh they set it up
08:26 that uh it's kind of intuitive what looking at. OK. And then
08:32 three types, uh primarily three types resistivity logs. And uh, and
08:38 course, the latter log is something are using uh a lot. Now
08:42 dual ladder logs, uh this basically you have uh sources and then
08:49 got these um receivers uh helping you of figure out between the intervals pretty
08:55 what the average is across that but it's a moving, it's a
08:58 interval. And so, uh you're resistivity going up and that resistivity coming
09:05 as you go down that law, to get better bed resolution, they
09:10 up with ladder logs and um they're up with ones that can uh penetrate
09:16 lot deeper than, than the older . And, and basically, um
09:21 it relates to you, just send a current. And if you get
09:27 current into the rock, then it's conductive. If you can't get more
09:31 into the rock, then it's more and they have these guard cells,
09:36 to speak. And I'll show you complicated thing which kind of uh create
09:41 a little uh magnetic field that kind pushes it in so that, that
09:44 focuses the current into a very thin . And then of course, uh
09:51 the induction log which, Which uh know, would go out five
09:56 And one of the things it would is create a um a ground loop
10:00 of a magnetic field uh such that uh the transmitter would send it
10:05 it would have to go way out the formation and come back and hit
10:08 receiver so that, you know, getting uh resistivity measurement far away from
10:13 wealth. And that's kind of the important thing, you know,
10:18 in my um am I looking at resistivity close to the well log or
10:23 I looking at the resistivity farther away the well log? OK. And
10:28 a real critical thing uh that we're stuff that's close and stuff that's farther
10:34 the um the normal resistivity uh because the way it's designed is almost always
10:41 something that's going to be telling us what's closest to the well, but
10:46 also have a way to, to, um, modify it so
10:51 you can get a little bit. , you know, you can have
10:53 shallow and a deep, but it's not that straightforward. Like,
10:58 some of these other ones like the locks, we talk about um,
11:03 directional drilling and all that kind of . Um You know, a lot
11:09 people wanna know why, why we see ahead of the drill bit.
11:16 can't we see ahead of the drill ? It's because all the tools are
11:27 the drill bit and, and so can measure what's here, but they
11:33 , you know, we haven't figured a way to focus them, so
11:35 shoot out this way, we have out ways to make the lateral logs
11:39 long. So that when you have directional, well, you can kind
11:41 see what's going on because you see section uh the full section because rather
11:47 going across one bed, you're looking the Strat graphic section when you're at
11:52 angle or when you get like this that helps you kind of predict where
11:56 at relative to, to the Just because because you can see layers
12:03 layers below, it kind of helps guide where you're at. You
12:06 you can see that you go into layer and uh and interpreting uh those
12:13 of logs is really difficult to And I think a lot of times
12:17 left up to a computer algorithm to auto correlate it and you can run
12:23 trouble with that. So I I hope that uh more geologists spend
12:28 time trying to actually figure out what is they're seeing versus what the,
12:32 the algorithms telling them. And when teach this, I'm trying to get
12:37 to look at a log, given information that you know about the variables
12:43 try to make the best interpretation that may not even be right. But
12:47 might be the best interpretation that you make with the data that you
12:51 And um I know in uh the and the Jurassic gasses in gas fields
12:58 um Mobile Bay and some Cretaceous were discovered. It was, it was
13:03 tight sand and all the algorithms told there was nothing there and, but
13:09 looked a little bit weird based on fluids and based on the uh the
13:15 and whatnot and the, and the , the particular lithograph they had there
13:19 made one guy with a lot of at Mobile think, oh my
13:24 this can't be right. I'm gonna you this story again when we get
13:26 exploration. But uh is that the of the interpretation is really important,
13:33 It's especially important for geologists because we uh more in a broader way than
13:39 , a geophysicist or an engineer you know, they're very deterministic.
13:43 want to see numbers, calculate exactly same every time, whether it's right
13:48 wrong, it makes more sense to . And uh and that's uh kind
13:53 how I, I try to teach so that you kind of have a
13:55 on this is just another diagram showing the latter log. And uh some
14:01 the more um complex and compound ones we have where um you have a
14:07 that you're measuring here, but then currents to kind of push this so
14:11 it, so that it keeps it spreading out like this as just about
14:15 would to try to get it to and uh go farther into the um
14:23 in other words, make a current based on this traveling all the way
14:27 this section, all the way out uh where you might want to see
14:32 the salt water water again and see resistivity go down. OK. And
14:38 is, this is the uh induction does kind of the same thing,
14:42 instead of having the guard cells pushing together, it's got a ground loop
14:47 kind of pushes it apart. So has to go way out, it
14:51 to go way out past this, field and come back in and get
14:54 over here. So it just forces go farther out. OK. And
15:01 you're a um petro physicist, you have a better way to explain it
15:04 I just did. But it makes when I explain it the way I
15:08 . So, um anyway, we uh uh examples here looking at the
15:15 P log and basically what it's trying show us is we have something that's
15:19 and permeable like a sandstone here. uh and over here we're dealing with
15:26 something that might be a carbonate, which you can see that it has
15:32 here. Uh Probably because the formation been cemented up. And uh and
15:40 of that, because the formation has cemented up, the resistivity goes
15:44 Now, if that was a po , uh it wouldn't look like that
15:48 all. We would have low They can look almost like this continuous
15:54 . OK. And the continuous of course, the S P log
15:59 gonna be uh far to the right to the well bore rather than over
16:05 towards the left. And uh the um gonna in general be relatively
16:14 Why is it low? The exactly. It's got a lot of
16:24 water in it and the bound water has salt in it. So it's
16:28 , but if it was packed real , it could be different. So
16:31 have a real tight. Um um know, a, a lot of
16:36 we have, you know, this of permeability here from the S P
16:44 uh indicates, you know, flow current through that because of the pores
16:50 really wide here. Uh You have resistivity because in spite of that,
16:55 enough connecting uh for throats to get to go through. But you're not
16:59 a uh necessarily a flow, but electrons are making it OK.
17:06 you're dealing with molecules over here you're with. OK. And um
17:16 one of the things that's also really again is what's going on deep,
17:21 going on shallow. And uh and course, one of the things that
17:26 that uh the R M F of is the mud, the resistivity of
17:32 mud and the R W is the of the formation water. Um This
17:40 R X O is gonna be within the mud and then RT is
17:45 be out in the true rock. so what we see here is uh
17:51 resistivity is greater for the mud than is for the water and the
17:57 So, uh what kind of situation that be? So you excuse
18:12 Well, are you talking about oil mud? OK. Did you say
18:19 based or you say oil? Oh . It says, sorry about
18:30 Yeah, you're speaking English faster than can any anyway. Um Here is
18:38 here's showing you that the resistivity in shallow is high and uh the resistivity
18:47 the rock, the chew rock out , that's why it says t but
18:52 here without the mud infiltration uh is , which means it's got the marine
18:58 . And, and so then what figuring out is a sandstone, it's
19:01 of water. And, uh and there's no oil. So if this
19:07 uh had a lot of oil, uh you, it, it's never
19:14 the same, but if it had lot of oil and gas in
19:16 the resistivity on the deep one would been higher. Ok. And
19:21 it, it depends on the This is showing you if the mud
19:24 the rock and the uh the resistivity the mud and the resistivity and the
19:29 rock are close to the same. is what you would get in a
19:32 sandstone. It's almost the same And so, so what's in the
19:38 , what's in the invaded zone and out here in the true rock,
19:42 balance of those things has something to with how you get the overlap.
19:47 . And uh so you can have that are the wrong overlap, but
19:52 indicate resistivity in the formation. Here's again, here's showing you the shallow
20:00 and here's the uh the deeper And usually when we see um resistivity
20:05 the deeper log, that means there's but not always. So if,
20:12 you were to crank up the resistivity your mud and you were to crank
20:16 the resistivity of the rock, um would see, you know, a
20:22 to this is something I think is important to, to remember even though
20:26 almost sounds counterintuitive and wrong. but when uh whenever you see a
20:32 of resistivity, really high resistivity is lot higher than this, it's usually
20:38 regardless of which one is overlapping, oil in the uh in Iraq,
20:45 know, which is creating an enormous of resistivity, natural gas would create
20:49 more resistivity. So if it goes scale, you see resistivity that goes
20:54 scale, you know, even the and the, um, uh,
21:00 do you call it? The invaded is gonna have gas in it.
21:05 it's gonna have a high resistivity So when you see everything going flying
21:08 the thing, it's probably gas, see everything kicked way over. It's
21:12 what, OK, even though you have these things switching around because of
21:17 balance, the key too is that , like if you're in a field
21:22 you're drilling, like, say, know, you just set up a
21:25 down for uh uh 20 slots if even do that anymore, uh you're
21:31 drill 20 wells probably gonna use all same tools you're gonna use the same
21:36 and you're gonna, you know, gonna know what this balance is here
21:39 how it's going to affect you one or the other. Ok. And
21:45 is just showing you, um, , slightly, uh different ones and
21:54 a mud penetration into a formation uh makes the deeper log uh low
22:02 But here you can see in in the formation, it's higher resistivity
22:05 the closer the shallower. And here's reverse here, fresh water is low
22:12 . And uh and so um low conductivity or high resistivity. So
22:22 you can see the relatively high resistivity both of them just because something is
22:26 resistant, just like if you have and gas in there, you're
22:30 things are gonna wanna go to the . And uh, here's, here's
22:35 good one. Uh This one's kind the classic one where, um,
22:42 can see, uh the deep uh um has, has a lot
22:50 resist. Excuse me, this is shallow, has a lot of resistivity
22:53 the uh the invaded zone plus with the combination of the fluids uh
23:00 gonna be really high resistivity. And when you get farther out in the
23:05 , um, this, yeah, is, this has gotten all the
23:09 into the, uh you have resistivity out here deep, which means you've
23:15 the uh the hydrocarbons. But you also see you've had an infection here
23:19 the shallow because there's hydrocarbons uh in shallow. Ok. You know,
23:25 mixed in with the uh was just and so you can kind of look
23:33 these different responses and here's something that's important to know. And um,
23:38 normally our normal uh resistivity are looking something close here or the shell is
23:43 be looking uh right here in the stone. And it's gonna be uh
23:50 the, the resistivity here is gonna highly dependent upon the uh the resistivity
23:58 the mud. But it's also, you have, if you have hydrocarbons
24:03 there, it's gonna add to that resistivity, which is what you saw
24:10 . And this one, in other , it's not flat. The shallow
24:13 be flat, but it's not because shallows got hydrocarbons in it too.
24:21 . And, and again, I think this is a really good
24:24 and even, even, uh, , this, this is, you
24:29 , everything's tight here. So there's absolutely nothing going on except for
24:33 tight Roth. But this is a example of, um, you're seeing
24:39 high resistivity and sometimes depending on the . Plus the, the hydrocarbons,
24:45 know, if it's gas, you're see the thing go off scale and
24:47 hardly gonna be able to beat Uh, but, uh, that's
24:50 of the things that kind of indicates you have oil and gas and this
24:54 a really good one right here. This one is the, the simplest
24:58 to interpret and you can see there's lag between whatever this, uh,
25:04 interpretation is. I don't know if , uh, um, more or
25:09 , uh, somebody shifted something wrong what, but it, it's odd
25:12 this is opposite. OK. So the, on the left hand
25:19 we have the flush, the transition and the un invaded zone. So
25:24 went my deep resistivity to tell me there's water or salt, uh fresh
25:31 or salt water out there. If saltwater, um then the deep resistivity
25:39 gonna be low and there won't be oil of the formation is full of
25:46 and the resistivity will be high. , that's kind of the key to
25:51 at it this way. Then depending the balance between the formation letter,
25:57 the oil and gas that might be both the transition zone and the flutone
26:02 gonna have an impact on the shallower . And um when you calculate all
26:11 , it works out pretty well, if the permeability goes down, it's
26:16 make it a little bit different than is higher. OK. So um
26:25 we have the true rock which and this is um let me just
26:29 , this is what I hate Yeah, see in this diagram to
26:34 this shallow in the deepest solid. here it's just the opposite. And
26:44 so make sure that you read the and uh normally the scales are gonna
26:49 exactly the same on every log. uh these examples that we show you
26:53 , from textbooks, uh I like confuse students and professors but here you
27:00 see um you have this overlap. is a classic in a permeable
27:05 The classic thing to see is a zone where the resistivity, the true
27:13 is greater than the flesh for the . You really see that and that's
27:20 overlap we look for down here. just the opposite. So what's happening
27:30 here, you have um something that's resistant uh out here because there's no
27:38 and gas. So it brings that in closer to what it would be
27:42 the bound shale. Ok. And way out here, uh,
27:49 you can see, uh, it doesn't notice anything. Um, here
27:56 have the shallow and it's basically looking the invaded zone in the transition zone
28:05 on how far it reaches. Is everybody getting bored? How many
28:14 you already know this? Everybody in ? Yeah. Ok. Ok.
28:21 . So, um, anyway, helps you see what, what would
28:24 be right here? What would that be right there? The oil water
28:34 . Yeah, it'd be an oil contact or a gas, oil
28:38 And, uh, normally if it's , though, the resistivity is gonna
28:41 out, it's usually when you get and inflammation it's, it's,
28:46 just plain gas in there. it's not multi phase or anything,
28:50 not, um, uh, oil dissolve gas and it's just gas like
28:57 gas cap. It jumps out at or if it's a, its petroleum
29:02 only has gas charging the, the , OK? And this is
29:09 I'm, I'm not gonna uh walk through this, but I do want
29:13 to take a look at this and see uh how some of these things
29:16 look a little bit different. one the things that happens with logs and
29:22 see if I can draw something Where's my pin? OK. So
29:38 you have a log, it goes like this. OK? I'm not
30:10 an art major. OK? So have a log and see here the
30:14 the logs have channels. So when they exceed, when log,
30:18 log exceeds uh the channel width that been given, um you're gonna see
30:25 for example, it's really high but the scale is here and here
30:29 general for the log, uh this , this is gonna skip his
30:34 And what this means is that the on here would be additive where it
30:40 here. In other words, this , let me this part of the
30:51 here, hit the edge of the where it's recorded over here. And
31:00 and so did this. So it , it exceeded that scale. And
31:04 , so whatever the scale is, would add this to that and this
31:09 that. And if, if the was wider and you didn't have another
31:14 over there, it would have actually , gotta change the pin again,
31:25 part right here actually would fit over . So that, you know,
31:32 you have that channel, it's like one of these things. See,
31:35 the edge of a channel, here's edge of this is a scale
31:38 Here's a scale if it goes over scale, uh and it cycles
31:43 it cycles back to here. And with gas, you will see it
31:48 twice. And when you get a , a, a resistivity log that
31:52 several times, uh, it's gonna almost hard for you to read
31:55 but you don't need to read it you know what, it's all,
32:00 usually gets. Ok, because it's, it's tighter than tight
32:07 Usually it wasn't in Mobile pay. ? Um, and here's,
32:18 another one, uh, here it the deep induction and you can see
32:23 deep, there's less resistivity here. had shallow resistivity higher because the mud
32:30 and the hydrocarbons together uh made the one higher. But what I was
32:36 to tell you before is when you the resistivity go way over here to
32:40 right. It's almost always because there's in the system. Not because they're
32:44 out in the tree rock, but they're in the mud system, they're
32:48 the mud filtrate, they're in they're in the, um,
32:53 the invaded zone or in the transition and that oil is still out
32:57 And so sometimes you see that reverse , but looking at this a log
33:03 the resistivity jumps out this far, almost doesn't matter whether it's deep or
33:10 , whether you got the overlap the you would expect it, it's just
33:12 much resistivity from the hydrocarbons that it's all the regions. Does that make
33:18 to you guys? Because you're gonna a log on your exercise that does
33:22 like this. And, um, see, you know, I,
33:28 teach this to engineers. So they'll have a lot of Petro physics
33:32 the Petro physic dude, it sometimes them, but they uh they often
33:36 try to find the log where you see more of the inputs and interpret
33:42 by getting more data. But uh I'm trying to get you to do
33:46 , you know, again, when get these little raster logs or just
33:49 chunk of paper, um sometimes you have all the information you need to
33:53 a good interpretation and it takes a geologist to kind of think with
33:57 open mind and uh and that sort thing. So the next uh major
34:03 type that we're gonna look at out the porosity and the permeability tools and
34:10 get back to my pointer and of , the um Sonic log um looks
34:22 the velocity of the rock. And do you, what do you think
34:25 a higher velocity? Um What type rock would have a higher velocity than
34:32 type of rock. There's really there's really one factor that's really important
34:38 , right? The density of the . OK. And, uh,
34:45 the Sonic log, uh, will out energy and it, uh,
34:49 it does travel times. So if very dense is the travel time gonna
34:54 higher or lower, it's gonna be lower. Um, I don't know
35:00 I'm dyslexic or what, but it bugs me that the number goes
35:05 It's like a race car. If velocity goes up, I want the
35:08 to go up, you know, the MPH to go up. So
35:12 just kind of, we have that of mentality. But, uh,
35:15 you look at these logs, um, it's measured in usually in
35:21 way travel time or just one way time, but usually two way travel
35:24 and it's gonna be shorter if it's . Ok. So it's gonna be
35:28 little number. If it's fast, gonna be a big number if it's
35:32 . And, uh, and just to remember that a density log
35:37 uh uses uh a source that's trying figure out a way of trying to
35:45 density uh based on molecular density. the neutron tool is uh, is
35:52 little bit more focused. I, believe on the uh the density of
35:56 rock. The other one is more on the fluids. Uh But
36:01 but they're all trying to come up some way of measuring density in that
36:05 . Whereas density is um higher the , uh the faster it should
36:12 And what does high density usually mean terms of a reservoir cement?
36:19 So for a reservoir, we want densities. Ok. So, and
36:26 anything that might be a seal, would want high density. And this
36:32 shows you uh you can read this your own, but this is just
36:35 you some of the material and the the travel times. Oh, this
36:40 actually feet per second. So this , this is like speed. And
36:47 and so, um you can see dolomite, for example, which might
36:52 uh recrystallized and you know, if wasn't cemented, it got recrystallized to
36:58 in even more spaces. So uh the fastest one. So this is
37:03 a race car, the bigger the um the greater the den density.
37:10 . And here, here again, think, I think each person
37:14 here in the class, whether you're or not, you need to kind
37:17 look at this log just to see what it is. But here you
37:21 see uh the interval transit time here uh 40 milliseconds, it's 100 and
37:29 . So uh this 1 40 might like 10 miles an hour and
37:34 that's a lot more than that. uh but uh again, the smaller
37:40 means that the sonic waves are moving . And uh there's a lot of
37:48 to get a sonic log, not especially when you're trying to uh sort
37:54 the interval velocities of the rock that uh whenever you do in seismic,
38:00 know, this really, he the , the sonic logs really help the
38:04 tie the uh the seismic response to rock record better by getting a better
38:10 model. Your velocity model is sort one where everything gets denser as you
38:14 deeper, you're gonna be messing up whole lot of, of uh you
38:18 , you're gonna have uh reflections or uh in terms of two-way travel time
38:24 are all off and uh it has be reprocessed and can be. And
38:32 and this is again, um here's fast ones, the fast ones tend
38:37 be tighter. Uh The slow ones to be more and uh looking on
38:44 density log. Um You can see as the bulk density goes up,
38:50 It depends on what it is here have. Uh uh Pola coal is
38:59 be um really low, you coal is really um relatively light compared
39:04 a lot of things. And, , and uh of the same volume
39:09 so that's really low. But uh , you can see uh the shale
39:13 uh be highly variable depending really on much water could be in. And
39:18 that's terms of, of uh uh and here here it has an active
39:24 source, Uh, caesium 1 37 , uh, it, uh,
39:31 can end up being a good gas . The, um, if you
39:38 one of these little caesium tablets into , well, like, uh I've
39:42 them doing in the North Sea in . It, it, uh,
39:44 know, you have to go in and pull the tool and do everything
39:46 can to get that back out. . I don't know why because if
39:50 very deep it's probably gonna be except that you start producing from
39:55 you might actually get, uh, some contamination in the product.
40:03 And, um, so, there's the Sonic log but here,
40:08 the density log. And, and at the same time I'm
40:14 um, and I'm not gonna read this out to you because there's a
40:17 here. But I want everybody to this. Um, if you see
40:22 typos, let me know. But , I've, uh, I've asked
40:25 that. Help a lot, somebody finds something but, uh, maybe
40:30 could give you a bonus point if find some. Anyway. Um,
40:36 gas, here's oil or water. that interesting? And, uh,
40:44 there's, there's a reason for, both of these things. But,
40:49 , oh, what, what I of what this really gets to
40:54 gets the point across to me better anything. Is that two errors in
41:00 tools? Both the density of the log have an error when they hit
41:07 . And because of that, they overlap, they overlap in the wrong
41:11 . One is too high and one way too low. One is like
41:15 low and one is ridiculously high. , um, it's because of,
41:21 , the way, uh, they measuring things and, um,
41:26 uh, and here you can see , um, we have, the
41:30 log is way too high. It's uh excuse me, it's uh way
41:38 low. Rather, it's minus, it has minus porosity and uh whatever
41:45 is here, uh It's, it's in the wrong direction. And uh
41:50 you get density is too high and porosity is too low and, and
41:55 logs way over here At uh you know, close to 30% ferocity
42:01 a limestone. And uh that could in some limestones. But uh but
42:06 a little bit too high for this . And here you can see uh
42:11 you just have oil and, or , oh uh for a lot of
42:17 , they're not impacted. Uh when get down and here the neutron again
42:21 affected by um the bound water which estimates porosity on a neutron light.
42:31 And when you get uh the lack that, then you have uh the
42:37 the process gets really low. So you can see the neutron log where
42:41 really low here is really high and is related to bound water and this
42:46 related to the, uh, Because that, that particular log
42:54 um, the amount of hydrogen in when you get hydrocarbons in there,
42:58 hydrogen goes up. It's normally it's normally reading the hydrocarbons.
43:05 as part of the H h2o But if you have gas, you're
43:09 have 4h, you're gonna have, , C H four. So you're
43:15 have 4h S in there. And really just, you know, just
43:18 it look like it's really dense. uh and you get that uh
43:26 uh incredible drop in uh in process . OK. And it's, it's
43:35 because the lot the scales are not . It's just that the um the
43:42 that they're measuring in, in the in the compounds uh in the uh
43:48 failings of each one of them cause overlap. In other words, it's
43:54 low porosity to the right. In cases, it's high porosity to the
43:59 in both cases. But one in , one has a higher porosity than
44:04 supposed to. And the other one a lower porosity because um here's another
44:11 to think of it too. We back here with oil or water in
44:17 , in a porous rock, they're same. But if you put gas
44:21 it, that change the uh the of hydrogen and, or water molecules
44:29 their uh the readings on those And makes them create an error.
44:33 that error. This overlap is one the most uh easily recognizable uh identifiers
44:40 natural gas in the system. Not to mention things that you might
44:46 in seismic. OK. And you take a look at this and just
44:53 and I want you to, you , visually, look at this,
44:56 trying to figure out how to interpret logs. So rather than have me
45:01 you what each one of these is you individually, I want you to
45:05 at it and see what happens when get water. Uh When you get
45:11 , uh the example before, didn't the separation, but sometimes you can
45:14 that separation. In other words, log that I just showed you oil
45:19 water were the same the whole way . OK? But when you hit
45:22 gas, the overlap was extensive rather limited. OK. And again,
45:28 depends on the four throats and the rock that you're looking. And uh
45:36 in this case, uh we're looking sands and shales and this is a
45:40 and not a limestone. And that an impact on it too. Look
45:46 happening down here in the shale. , it's that uh it's that uh
45:54 , bound water in there uh affects affects the uh um neutron denser.
46:07 . And here is just an example showing you gamma logs resistivity density porosity
46:14 clay. Sometimes they call it the . Um When we use the word
46:21 of clay or volume of shale, type of rock are we talking
46:29 I don't think they ever tell you except we should automatically know, I
46:35 . Course, excuse me, the porous rock? Ok. Um
46:42 what is, what is, what the shale? What is V
46:45 What is, what would, what that telling you about the texture versus
47:02 ? OK. I got it. clay V shale. It's telling me
47:05 clay, V shale, what is distinction between those two things between a
47:11 and clay? V clay V shales of the same thing? Shales,
47:14 rock plays the particle, right? , how big are the, how
47:18 are the clay particles? They're very grain, right? five.
47:27 well, it's four point something microns smaller, right? OK.
47:34 So, so uh so hang on this thought. OK. It's two
47:40 to think about is the V shale fine grain carbonates. You have fine
47:52 carbonate that are less than five Sure. OK. But they don't
47:59 that shield. Why don't they call the shale? What type of rock
48:05 have V shale or V clay go in? What type of composition?
48:13 , yeah, but it um it's be silicates as opposed to carbonates.
48:18 gonna be silicate clays versus carbonates. if you're an unconventional exploration is,
48:26 you like to have and you're thinking natural fracturing. Would you like to
48:32 high v shale or low V shale you're thinking of natural fracture?
48:45 Exactly. So these little things about little mixed variables of texture and composition
48:55 critically important? You think that you uh known whether it's a clay or
49:00 sandstone and you know, you guys geologists, you need to know this
49:04 than the geophysics and the uh and course, it's always good when a
49:08 knows all this and a lot of they do, uh, Fred Hiltermann
49:12 me on this stuff when I walk his class every time. And,
49:15 I always come up with something to him. But, uh,
49:20 um, but anyway, uh it's important to understand these different relationships because
49:25 V shale number, uh it's not a, it's not just place size
49:31 , but it's silicate play size particles the, in uh fine grain carbonate
49:38 can be the result of cementation you know, really tight limestones,
49:44 , that have nothing to do with . And, uh, but go
49:49 again, what type of rock would like to have a high V
49:55 There's a certain type, there's a , certain type of rock in a
49:59 system that we would like to have high D ship exact well source
50:05 But, but what you huh this because a ductal seal is like having
50:14 . It got a plastic wrapper around , you know. You know,
50:18 earth goes like that, you I probably shouldn't have done that.
50:21 if the earth coughs, it fractures it's so brittle, the limestones but
50:26 the V shells, they, you , they're like, it's like
50:30 Uh the ice shell between the two sands was, um, in some
50:36 it was, you know, like thick and it was holding back over
50:41 sections on either side, uh with oil water contacts. When most of
50:46 time when you have uh two uh that are within a, even,
50:51 if they have a shelf, the petroleum system kind of sets up
50:55 they, and they sort of have same oil water contact, you
50:58 it's just like this and the oil contacts like that. But with uh
51:01 a really strong seal in between those , uh they started producing one
51:07 and the oil water contact went up top of the, over the lower
51:10 and it just freaked out the how can you have water on top
51:14 oil? And again, they were rocks, you know, the rocks
51:19 like this and they're correlating them here this and here like that. And
51:22 different water contacts in the wrong And uh and that was confusing to
51:28 too. And again, that's why have to think three dimensionally when we're
51:32 oil and gas. Ok. Um rock properties uh uh related to reservoir
51:44 and reservoir fluids were really important you know, we're looking at the
51:49 , we're looking at the fluid fluids we're looking at the porosity permeability.
51:53 of course, that density log, what we're trying to figure out with
51:57 density log is the denser, it the less porous it is. And
52:01 the higher the density should be. of course, some of these tools
52:05 measure the neutrons, others measure the . And depending on uh the fluids
52:11 there, you can get that overlap the density log and the uh and
52:16 neutron lock. So, um but else do we want to know?
52:29 other useful information? I think I you this question earlier on and
52:33 all, you guys got all the answers to it. What other things
52:37 we want? What other types of information can we get out of these
52:46 ? How about this? For we have two logs and we try
52:49 correlate them and we think we have pretty good correlation. What is it
52:54 tell me if there's a formation in ? Well, that's here in one
52:59 . Well, that's down here. does that tell you right away the
53:03 ? Right? There's a dip And say this is relative to sea
53:08 , this is relative to sea There's a difference, it tells you
53:12 don't go, don't look for this over here. It's that one,
53:17 an automatic thing. Ok. And a geologist should be thinking that all
53:20 time. Ok. Uh, what be another thing that we could get
53:26 looking at logs next to each And I'm gonna try really hard since
53:31 only eight people in this class, gonna try really hard to get you
53:34 understand how to pick a fault that size it. Ok. I've,
53:40 gotten all the way through class final . You can't do that. Doctor
53:45 N, who without seism, the is how do you pick a fault
53:52 , with two logs or how do pick a fault with logs? Part
53:56 the answer is you need to have least two to it. It helps
53:59 have three. Excuse me. You're looking for missing section. If
54:09 is missing, it's important. Uh thing that comes into play with this
54:13 you're talking about faults, people What about a pinch out?
54:17 one of things that happens with, basin infill, especially when your wells
54:22 pretty close to each other. You , you're either right in the middle
54:24 the epicenter or you're not. But way uh you're in an area where
54:29 rock accumulation rate, two wells are to each other. Rock accumulation rate
54:33 be pretty close to the same, if you're on depositional stripe. You
54:38 way down here on depositional dip. depot center may be down here and
54:42 coming up on a ramp over here you can see pinch outs like
54:46 But uh nevertheless, you'll see the from one well on strike to the
54:50 on another. Well on strike is be, it's gonna look like layer
54:53 geology. But if you have that in here, you're gonna expect more
54:58 space as you go down depositional Uh And so you're gonna have more
55:03 . It may not be sand, it might be shale because you have
55:07 , more space to fill in. uh and so in that sense,
55:13 it helps you figure out where a center might be and where, where
55:19 on lap surface might be. Uh when we're working with seismic,
55:23 we're working at a little stretch you know, wells that are two
55:29 apart or, or 200 ft you can't really see what's going
55:33 But when you get these logs that farther out, in terms of
55:37 you can get an idea of which the sandstones are thinning and which direction
55:43 thicker. And that's one of the you can do with well logs.
55:47 uh and what is, what is telling you again if uh I have
55:52 sand deposition here and I have greater deposition here. What part,
55:57 which hand am I gonna start doing drilling uh um pattern where, where
56:04 I gonna drill the most Over here this 1? Right? OK.
56:08 to my left hand and not my hand. Ok. Where, where
56:12 have that greater accommodation space, you're have uh more sands. And also
56:19 to that as you get into the center, the sediments are gonna be
56:24 deeper and there's a greater chance that of the shells underneath it has matured
56:27 the ones that are up on a . Ok. What else? Uh
56:34 else can I get out of There's so many things, actually,
56:38 could have 17, these SIS, , I'll show you what some of
56:44 are. Ok. Um, here can see structure with the,
56:50 um, we already talked about this between logs is another thing because that
56:57 us figure out which units really are same reservoir units and not, and
57:02 problem with auto correlation and, and somebody just looking at things as
57:08 sections is it really throws you Uh, when I, when I
57:11 a class with a lot of engineers you give them 10 logs and you
57:18 , ok, here in this the 5400 ft sand correlated to the
57:22 ft sand in the other ones. they start correlating all the logs at
57:26 ft. Um And even if you Kelly bushing, you're still gonna be
57:32 . And if there's no, unless no structure whatsoever and uh and that
57:37 a problem. So correlation is very too. Also, uh we're gonna
57:41 about sequence photography but uh just on basis of finding upwards coursing upwards type
57:48 and truncation that happen, uh we figure out uh some of the um
57:55 like flooding surfaces and sequence photography. all based on surfaces. You can
58:00 sometimes see transgressive surfaces, you can regressive surfaces and you can see maximum
58:06 surfaces. And those are the key to uh to doing uh sequence photography
58:11 you can see those on logs. It helps to have more information than
58:15 a log. Uh It's always good have sort of the structure figured out
58:20 uh and maybe have a little bit seismic. But when you get,
58:24 that and put it together with, all of these logs, you can
58:27 a whole lot more than just find porous and the uh impermeable uh rocks
58:33 you're looking for for the petroleum system really localized. But another one that
58:39 think is important um as uh fay's is another thing and here's just an
58:51 of it and we'll talk about this little bit more uh with, with
58:55 examples, but here you see um here's, here's the mythology log
59:05 uh sometimes when people draw these, stretching their imagination to make it
59:10 But what you see here, what is this right in here? But
59:17 this uh interval? Mostly this is um it looks like it's a,
59:22 gamma log. It's a little bit active to be an S P
59:27 But what is uh yeah, it log right there. Uh Anyway,
59:33 So what would this rock be right ? We're looking at, it's gonna
59:37 shale and this is gonna be a , right? And so what they're
59:41 you here is that here, I've the um this low gamma, really
59:47 gamma over here. So these are relatively clean sandstones. And as I
59:52 into this direction, what's happening, upwards and it's finding upwards sort of
60:01 like this would be the base of channel and this would be uh the
60:06 of a bar and then we're getting higher and higher in a bar where
60:10 starting to get fine same grades. then you may get something like a
60:16 a shale plug sitting on top of when it's an abandoned uh river
60:21 And then right on top of you start seeing something uh that might
60:27 , it's not real obvious here. if you get a transgression, you
60:30 also get um a really high This is, this is actually higher
60:36 this non marine thing. So this sort of marine I looking shale
60:42 is very subtle compared to, to over here um where this is a
60:53 . Um This right here is a um excuse me, this is an
61:02 surface of something cutting into the flood . And here we have a flooding
61:07 where you have a transgression. So maximum flooding surface is there. And
61:12 they have this pathetic little spike. , if you get an M F
61:14 , you're gonna have a really sharp relative to what you see in these
61:18 plates. OK. So, so looking at this curve, you can
61:24 of sense something that looks like an river cha. OK. And you
61:30 also see flooding surface and doesn't have be a maximum flooding surface. But
61:35 , you know, with that character would just be the flooding surface of
61:39 pair sequence and not a full third slash fourth order sequence depending on whose
61:45 you're using that kind of. But the these shapes here that we
61:52 like this when we look at these shapes. And uh sometimes uh we
62:00 at what could happen with one of other logs over here relative to that
62:03 in mythology as well, like maybe Sonic log or a density log.
62:07 We call those types of logs You know, that's, it's sort
62:12 the pattern is a motif. So this pattern here where um there's
62:17 abrupt surface at the bottom, uh bring in a coarse grain material.
62:23 this is from low energy to high . So it's usually, you
62:27 something that's an erosional surface and they a little thing there. And uh
62:33 they have a small erosional surface And uh but you have this uh
62:40 filling in and then as the bar and migrates, uh we get to
62:46 end and you uh terminate when when the uh when the uh shale
62:51 comes in, this isn't the shale here. It's, this is sort
62:54 interferring shall flood and flood over the . Uh Uh An old, a
63:00 channel would put some sandstones on top it. In this case, they're
63:04 this as, as a green Uh It's again, it's not real
63:09 , but uh if you had this , it would be explainable by that
63:16 . In other words, if you a core to compare it. So
63:19 we, whenever we come up with , it's really important that because there
63:25 be a lot of different faces uh Depending on whether you're sort of
63:32 up depositional dip in a fluvial system if you're at the delta front,
63:37 gonna see completely different things at the front than what you would see
63:41 And sometimes they look exactly the So you have to be very,
63:44 careful how you interpret them. Um anyway, uh this is just showing
63:50 some of these, um if you for logs that look exactly like this
63:57 your area, you're gonna be dumbfounded it doesn't always work out the way
64:02 expect it. If you, here in this log you're clearly
64:10 um, the main channel sands, , when it's nice, good,
64:14 traction. And, uh, here got the cross beds, but
64:18 then you see the, uh, getting finer and finer great. I
64:23 , in other words, um, point bar that this represents is,
64:27 know, the tops of the point are gonna be finer grain. You
64:30 high energy at the bottom and they keep accreting like that. Uh because
64:35 highest energy is always down here up the, you're gonna get uh finer
64:40 stuff across the top because it's winnowed . And uh it's kind of like
64:44 it gets to the size of a an infilled channel, you're dropping some
64:49 out and you're still transporting some But then as it starts to
64:52 you get the fine grain stuff and uh ends up down here, but
64:56 keeps moving and traction flow after the phase happens. Uh But if you
65:02 to be in a part of uh distributor channel where it's almost jet flowed
65:07 the whole thing, that thing is fill up eventually when you have a
65:12 that channel gets cut off and you're gonna have that sand that's filling it
65:16 the whole time. And so it blocky, it would look like this
65:21 opposed to that. And here they're you this could be a titled channel
65:26 uh this could be a tidal sand , which is also true.
65:31 you know, you kind of have figure out where the coastline is,
65:34 the river system, the fluvial systems and where the delta are to use
65:38 motives. Ok. And now we're to go to the exercise and I
65:46 load this yet because I didn't um, give it all away.
65:54 we'll, we'll talk about this a bit on. I'm gonna post it
65:59 you can start working on it. , uh, it's gonna be two
66:03 . Let me just pull them up show you real quick. The lecture
66:20 I just gave will help you interpret . And again, I want you
66:23 interpret them. I don't want you , uh, look in, look
66:28 it as a deterministic problem. But is one that's one that you try
66:32 interpret what it should mean. uh, if, uh, if
66:37 can invest in some, um, pencils or even crayons, if you
66:43 , this is the color scheme I like you to use. And,
66:49 , uh, some people, one that a lot of folks want to
66:53 is go and get a software package do and make it look pretty.
66:56 don't want it to look pretty. want it to look like you interpret
66:59 I want it, want it to like you got your head into the
67:03 , not into the software, but the problem to understand why you made
67:08 interpretation you did. And uh some the things that we're gonna look at
67:13 gonna be the uh static S P um um the S P that you
67:21 , we talked about this a little , but that's gonna be really
67:24 And uh you're gonna be uh measuring thing called alpha uh in with Gama
67:34 , they like to do the but just go ahead and do it
67:38 itself on a, on a, a uh S P log. Uh
67:42 you do your cutoffs and stuff like . And um before you get started
67:47 it, I'm definitely gonna go over Real obvious shale breaks like this one
67:57 I know I mentioned this earlier on is why I left it out of
68:00 lecture. But you're gonna have uh in the exercise, it's important to
68:05 that that's a real jail break. I think I told you early on
68:11 When it first started out at I reevaluated a field and we lost
68:14 million barrels of oil. And the president who exploration came down uh of
68:20 whole company was the head of exploration down and chewed me out for losing
68:25 million barrels of oil. And as turned out, I was being optimistic
68:29 he didn't know it. Uh But here, these little inflections to the
68:35 , you know, the, the cleanest sand is here and the really
68:38 sand is there. These little inflections with this Gama uh suggest that there
68:43 some shale parties. So sometimes you as an interpreter, not a Petro
68:49 with an algorithm, but as an , you would add some d shale
68:53 that, you would say, you know, there's a little bit
68:56 shale in there. So it's not uh this interval right here. This
69:01 a good uh when I get to little point right here, that's
69:04 that's a good however many how much uh sandstone is like 100% net,
69:10 is gonna be less than 100% net gonna be more. And I want
69:13 to look at it in that, that kind of sense. So that
69:16 only can you say this is a , this whole thing's a poor
69:20 but where is it tighter? Um uh how much, how much net
69:27 is is in this? In other , I have to move a little
69:29 out because it's not just a straight that comes over like this also what's
69:33 on over here? Remember when I drew something on this and uh things
69:45 off scale. And so the the tips of these resistivity logs are
69:52 and here you can see the dash here and the solid is here
69:59 um, guess what? You can't tell which one is overlapping which one
70:05 you. But what's happening to the log in general and look at the
70:11 log over here it's gone, you , I mean, it's just wiped
70:15 . Um, you still have Come on guys. Uh But
70:24 the, uh what do you think is out here? I just wanna
70:28 everybody in the class where you think is right there is hydro serum.
70:37 . This is, this is definitely be hydrocarbon. Sure. I'm not
70:40 tell you which one, but I you, you could figure that out
70:43 you think about it for a You know, when you,
70:48 when you have gas in there, remove all the fluids. And so
70:55 , it's almost like air. how conductive is air. So,
71:05 when, so when we see a of lightning that is a gap
71:10 that's a charge that jumps across a conductive gap, which is why it's
71:15 powerful. That's why, you there's a lot of bolts and you
71:19 want to get hit by it. . Ok. So, uh
71:24 and then, then there's these things here and it'll look a little
71:28 but I'm gonna ask a bunch of . Uh You can start reading it
71:31 you want, but I'll, I'll over this in a little bit more
71:33 detail on Wednesday. I think I'll it due Wednesday a week from
71:38 And, uh, I always like give you at least, uh,
71:41 , a week to work on Uh, since we have a whole
71:47 . If it was, uh, this was a professional master program,
71:50 give you three hours. I'm It's not there yet. And with
71:58 , I'll let you guys go. , does anybody have any questions?
72:08 , um, let me just say I cut, cut off this,
72:11 , recording, uh, Nicole Daniel , uh, k uh,
72:18 um, I hope you guys are better soon or get whatever is broken
72:23 your truck fixed and, uh, can see us in class on Wednesday
72:28 , get better and, uh, get everything sorted out. Thank
72:34 Yeah, we'll, we'll be doing again anyway. Uh, regardless just
72:38 case somebody, you know, who one of these guys may,
72:41 get in a car wreck or something , yeah, knock on and,
72:49 , take care. Thank you. , there's my
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