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GEOL7323 Borehole Geophysics - Day6 03-04-2023 PM
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00:31 Hi, Stephanie, how are you ? I'm doing ok. Good,
00:37 . Um, I'm just having a at this little case that,
00:42 Alan Campbell provided. Um, as quickly look at these logs, this
00:55 part looks kind of funky, doesn't ? Mhm. So, as a
01:05 at first you think, well, they, maybe something messed up.
01:12 if you look closer, what would other, uh, what's our other
01:16 for this big kind of uniform I ? Hm. Let's see that
01:31 And, I mean, I don't , it's like a huge change.
01:38 it is, I don't know what cause that big of a, unless
01:47 like a wash out or something. I don't think so. So
01:52 it kind of looks like a wash or that they're bad logs. But
01:57 we look at the seismic, there's a seismic response you can see this
02:07 the top and in fact, there to be a seismic response here and
02:15 logs seem to show it and it like there's a seismic response here.
02:22 . So, the logs actually look . There's pretty much only one thing
02:34 generally comes in that uniform of a salt. Oh OK. So,
02:55 sure enough, if we went in , I can't see all this,
02:59 uh pink is probably, yeah, is the density log. You can
03:05 that the density log is quite And then the acoustic impedance in Ballo
03:17 the basic sonic log. So what just done is taken the density here
03:22 multiplied it by the sonic log as do to get this impedance. Um
03:32 is now the the blue guy is the impedance log. So and he
03:36 the impedance and it looks like they've that here. This is the
03:40 the change in impedance and then convolving with the wavelet gives this, which
03:49 our synthetic sio gram, which seems this area to tie pretty well.
03:55 , and they do have annotated out barely top salt base salt.
04:02 so sure enough, that's, that's story. And then they uh they
04:09 apply uh checks shot corrections to this . And now you can see that
04:14 synthetic ties the seismic much better. this is actually pretty beautiful. You
04:27 really see the effect of the big live changes, big impedance
04:37 nice reflectivity. And then the real shows us up quite uh definitively.
04:45 a nice little case there. Now can uh look another V S P
04:57 once again, here is depth, deeper, time, getting longer.
05:02 this guy coming in there. That one is the P wave.
05:10 that's our P wave downgoing first And then this event is high amplitude
05:18 very, very linear. See the wave we've got these little kinks
05:24 So we know there's a layer, layer, a layer, but this
05:29 is going right through. So that's of unnatural. That's the tube wave
05:36 propagating down the fluid. So we like that, but there it
05:49 And this well looks like it's drilled to 8, 20 m deep.
05:57 we can see that, as you imagine, the tube wave goes down
06:00 fluid in the well hits the bottom the well and bounces back. So
06:20 that's that. So that's just one the uh one of the noisy things
06:29 happen can happen in, in uh the V S P. So let's
06:35 at how we're gonna process this whole . Now, now we're moving toward
06:40 interpretive product. So just schematically, um we have that depth and time
06:57 went in and we looked at this arrival, we got time to depth
07:01 the P wave, we got interval , we got Q maybe we got
07:07 the source wavelet looked like. We the frequency content. So we've looked
07:13 thoroughly at that first breaking downgoing So we understand that now we want
07:21 be able to use this data to it directly to surface seismic So here's
07:27 little conceptual step I wanna make this S P data look like surface
07:40 So we remember that surface seismic is to be zero offset reflection. So
07:46 surface seismic is a shot and a energy down back cool zero offset source
07:55 receiver in the same position in two normal instance, travel time. So
08:01 the energy is going down into the and back, that's it. And
08:04 how we plot out our whole section volume, the surface seismic section or
08:08 . So now our job is to that we're going to interpret it with
08:11 logs and the V S P. we have to make the V S
08:15 somehow correspond to the surface seism. means that we've got to make the
08:22 S P look like pure reflections, ? So this is how we make
08:28 V S P uh look like and and be very similar to surface
08:38 So number one, we've got all downgoing energy and now I wanna look
08:42 reflections because that's all that the surface is surface se is just reflections.
08:47 that means I want to get rid the downgoing wave. No, this
08:55 a, a view that's good for kind of filter, but it's what
09:00 use in BS P. So the ways carrying most of the energy remember
09:05 the reflections are just the change in impedance over two times the impedance.
09:11 the reflection energy is just a small of the downgoing energy. So
09:19 the downgoing energy is taking all the down their impedance contrast that's reflecting a
09:26 bit back. But we said the , the amount going back is the
09:32 , which is the change in impedance two times the impedance. So that's
09:37 gonna be about .01 or something. very small. So these upgoing reflections
09:50 very small compared to the downgoing That means it's hard to suppress the
09:58 energy and get the upgoing energy So what we do is kind of
10:08 tai chi ta method of beating up succeeding against a much bigger opponent.
10:21 might remember if you ever took any arts, some of them, if
10:25 dealing with an opponent who's really if you go right at the
10:30 that's probably not gonna work out too for you. They're just a lot
10:35 than you are. So the classic kind of tai chi approach is to
10:42 the opponent's strength to your advantage. a simple case of that would be
10:50 approach the opponent, the opponent lunges you, you step out of the
10:55 and trip them and that's the kind move that a Tai chi person would
11:00 . They're not gonna try to hit directly. They're gonna step out of
11:03 way and trick you and use your energy for you to fall over.
11:08 so in a sense that's the kind filter we're gonna use here. What
11:12 gonna do is pick the downgoing wave then just subtract those first break picks
11:27 effectively align the data. This is to flatten it. So we're gonna
11:40 it. And now we've got all big energy that's aligned horizontally and then
11:47 got our little reflected energy that's kind stretched out. And is that
11:59 a high angle dip with respect? I've done is just shifted these,
12:04 of these traces up to 100 just a bulk shift with just
12:10 a constant value. So I've just the trace and then I've aligned
12:16 And now what I can do is is all big stuff, high energy
12:20 aligned horizontally. Now, I can run a horizontal enhancement filter across
12:29 So even just a running average at time everywhere to just sum the stuff
12:36 horizontally line. So we've got big that are summing and I'm just taking
12:46 average. And then there are these numbers that are the little reflections that
12:53 amount to much when we average So effectively, what happens is we
13:00 out all this highly dipping stuff and end up with just horizontal events.
13:24 this is where the tight chief filter in that. Now I've got this
13:30 horizontal stuff and I strictly subtract it the shifted unenhanced. And when I
13:54 that subtraction, it just leaves me the residual. So I've, I've
14:08 this really big guy and then little that said, OK, big
14:12 I'm just gonna make you even I'm gonna make you so beautiful.
14:17 then I'm gonna cancel you subtracted and gonna leave this little residual stuff and
14:25 what happens. So we're left with little residual. And now this is
14:33 reflection energy. That is what we're in. Now, even at this
14:45 right here, we could say we could say that this has been
14:50 downgoing wave and this is the signature the source that's going into the
14:56 What's being reflected is the outgoing But this energy that's coming up is
15:04 a scaler times what went down. upcoming is just the reflection coefficient times
15:13 downgoing. That's where we got the , the upcoming was just the amount
15:19 small amount of the downgoing that's So what that also means is that
15:29 reality, this whole downgoing character of that we talked about is its
15:39 The upgoing is just the reflection coefficient this. So if I've got
15:43 this signature here, I can actually suppress that signature everywhere via de
15:54 So any time I see this I'm gonna collapse that to a
15:58 that's what the convolution is. So have this big long rever toy
16:04 which I do not want because that like layering or it looks like geology
16:09 it's not, it's a reverberating downward with multiples and all kinds of junk
16:19 it. So we don't like So I can basically, whenever I
16:23 that I'm gonna spike it or I'm divide this signature out of the
16:29 which is the de convolution process. I'm gonna devolve these upgoing to just
16:36 a sharp reflection that's gotten rid of wavelength. So that's where we're
16:44 So here you can see it. an example. Um O V S
16:52 align enhance subtract to get the, residual, you can see all this
17:01 stuff here. Now we've got it here and then I'm gonna move this
17:07 two way time and we'll talk about does that mean? So now we're
17:18 beat our way through all these And as I said, at any
17:27 position, the trace of the seismic we get is the sum of the
17:32 plus the upgoing. So we saw downgoing and all the upgoing. So
17:37 imagine that the total signal is downgoing upgoing. But we said the upgoing
17:46 really just a reflection times the It's like if I'm standing beside a
17:57 outside or something, I can scream that wall, scream a sentence at
18:02 wall, that's the way of going , going or out and then it
18:08 the wall and it bounces back and gonna hear what I said with a
18:13 amplitude. So this is the back is exactly the outgoing times the reflection
18:21 of the wall. Similarly, in earth, the, what's coming back
18:25 us is just the reflection coefficient times , went down the down going.
18:37 if the total is the downgoing plus upgoing and then I estimate the downgoing
18:44 it. And I've just got the , but the upgoing is the reflection
18:48 the downgoing. So I just divide upgoing by the downgoing. And I
18:53 the pure reflectivity. Now, when do that in the frequency domain,
19:01 called frequency domain de convolution. It's deterministic because I measured the downgoing,
19:15 have determined the downgoing already, I'm guessing at it. I measured
19:19 I extracted it. And so the convolution is done in the spectral
19:26 the freer domain. So I take 48 transform of the upgoing 48 transform
19:30 the downgoing, divide them get the transform of the reflectivity do the inverse
19:35 transform. And that is my de trace that it's all sharp and
19:44 right? Good. So there we it a game the the total trace
19:56 the sum of downgoing upgoing reflected waves devolve and then I get my sharpen
20:05 . So here's, here's a little uh say we had a check
20:10 So just a very sparse V S , we can see these waves going
20:15 into the earth. This is all and horrible. But let's see if
20:19 can get anything out of it. we align enhance, subtract devolve shift
20:29 two way time, stack it all . And then that's my BS P
20:34 trace that's by reflectivity. And surprisingly , it actually works. So this
20:50 assembling our data into something called an plot because it's looks sort of like
20:57 . Um So we've got depth actually way. So DEA now plotting this
21:07 , our logs are going down, is the sonic log. So here's
21:11 energy going into the earth move to way time, we stack this
21:16 I get this and then I I repeat it and then I can
21:25 it to the surface. And sure , even this uh lousy data that's
21:29 sparse. When we stack it we get something that really compares not
21:36 badly with the real surface se and might uh just change the character of
21:43 surface seism like a little bit to the BS P. So now where
21:49 we? Well, suppose I say an event on surface size like
21:58 Is that meaningful? Well, here is at 1/2. What does that
22:05 to? Well, yeah, that corresponds to the sun verst sandstone at
22:18 stuff. So that's how we use outlot. So the is is what
22:36 been looking for. I've been looking a mapping that takes my surface seismic
22:42 time goes back and brings that into well log in depth. So this
23:06 starting to tie everything together for We've looked at analyzing well logs.
23:10 done a little bit of VSP. we're correlating the VSP to surface
23:15 And I'm beginning to understand this relationship the two Or three or 4 when
23:22 add synthetic ses. So that's where going. Let's let's chip our way
23:30 this again. So we looked at uh this data we had oh somewhere
23:37 back here. Well, let's not through it. We were looking at
23:44 data before. Um Now we have the total data. We enhanced this
23:55 . Now I I plotted it we could plot it horizontally. Um
23:59 enhance this and subtract and then I up the left and this is what's
24:03 residual. Then I take this residual sharpen it or remove the wavelet or
24:16 de convolution. And this is what get. So you can see removing
24:29 lot of the wavelet, removing this energy via de convolution really makes the
24:36 become much more sharp and resolved. . So now let's think a little
24:46 more about this two way time A raw V S P we imagined
24:57 depth, we've got a shot, energy is going down bouncing back.
25:04 is the kind of the geometry, real geometry, the data that we
25:09 at every depth has waves going And again, we imagine we've got
25:16 all the way down here, the is going down, taking longer to
25:19 there and then bounces back symmetrically to surface in the ze- in this zero
25:26 case. So here's our raw data of schematic from a shot close direct
25:36 and then reflections. But I would to make all of this data looked
25:47 it was recorded at the surface. actually do have one trace that is
25:54 at the surface. So in the S P, if I've recorded uh
25:58 I put a G phone right at surface, then this is the two
26:02 normal incidence time to the surface. you can see it takes a while
26:08 the energy to get there. So of this stuff is not in two
26:12 time. It's just in raw experimental because this is where the reflection
26:26 This is where it ended. I'd to be able to use all of
26:30 reflection information to enhance the reflection that at the surface. So I gotta
26:38 out how to stack all this reflection coherently. So I get one beautiful
26:46 at the surface which is my two normal instance time to the surface,
26:53 is effectively the surface seismic trace. how can I move this? So
27:10 all that reflection information gets stacked that that to stack it, it has
27:15 be at the same time position. what do I have to do to
27:21 all that stuff look like it? , here's what we do. I've
27:39 the surface shot and I've got the it takes to go to the receiver
27:44 . So I know that so to the day to here look like it
27:53 recorded there, I just have to on the first break time and then
27:59 that brings the data up to the . So if I bulk shift the
28:04 here just by the first break which is equal to the time back
28:08 surface, I make the data into way normal incidence time for the zero
28:14 case. And then when there's a trace from deeper, again, I
28:18 the first break time, just add first break time on and then that
28:25 that into two way no lessons. I take this and I just add
28:30 red line time on to each And sure enough that aligns all the
28:40 reflections In two way time as it , we're adding on the the time
28:54 the depth where the trace is back the surface. That's just bringing all
29:03 data recorded here to the surface at level. All the data recorded here
29:10 by its first break time to the . So we do that when I
29:14 shift every trace, the reflections are all aligned in two way normal instance
29:20 and I can stack them. So is just a way to use all
29:25 this data to get a better reflection . So that's, that's the trick
29:40 we use for zero offset processing. the goal of making the extracted V
29:48 P look like surface seismic but with better signal to noise. So that's
30:07 we did here. We took this shifted it and then stacked it all
30:20 and that gave us this. So back through this process. Now
30:30 we took the raw data, we it enhanced the flattened stuff, subtracted
30:43 to get a residual designed a decon on this downgoing did the de convolution
30:56 it to two way normal incidence time it and then stacked it. And
31:09 is our V S P extracted trace is a map of the uh sharpened
31:21 activity. So this is really valuable . OK. Good. So now
31:33 talk a little bit more about how , how we did that horizontal
31:39 And you'll remember this. The, of the main techniques that we use
31:44 called a median filter. And how filter works is first of all,
31:57 remember what a meeting is. So we have these seven numbers, the
32:09 is the middle number when they have sorted in a sending order. So
32:22 take these numbers and we put them a sending order minus one minus
32:28 567, 10,000. So that gives this guy and then we just select
32:38 middle value median being middle. So this set of numbers, the median
32:45 six instantly. What's the average of numbers? Um, it's about 1
33:32 . What's that again? Um, about 100 and 46. Oh,
33:38 and 46. Yeah. Yeah, you can see that all these are
33:43 small and there's seven of them. seven into 1000 is About 140.
33:54 there are a couple of things that apparent. Just if you were given
33:59 numbers, we don't know anything about numbers. But if you were given
34:04 numbers and you were said you can have one, you got to describe
34:10 set of numbers with one number. what the statistics is. What number
34:17 you select to describe this set of ? I mean, I'm assuming the
34:26 but I don't know, six is such a weird number. Describe all
34:30 that. Yeah. Well, there's really a right answer. There's all
34:36 can tell you is that that's a of numbers. And if you only
34:40 me one, I can give you thoughts. One of the thoughts is
34:48 median, which is a standard I'll give you the median which is
34:52 or I'll give you the average, is 146. Which do I think
34:58 best? I think six is best We've only got one value that's really
35:05 . 146 doesn't describe any of the . But what do I know?
35:11 just a humble and poor, simple . So I don't know what I'm
35:19 . So we don't really know, we have a sense that there's a
35:23 of balance, that one number looks a real out layer. So if
35:29 think that this Set of numbers is to error, I might be saying
35:36 made these measurements was just having a Saturday afternoon. You know, all
35:40 other ones were Wednesday at 3:00 and was Saturday At 7:00 AM and I
35:48 it's screwed up. So in I want an estimator that does not
35:53 that number and the median does not that number, the average definitely emphasizes
36:01 number. So if I believe that , I would think that,
36:05 maybe 1 46 is a good If I don't believe the 1000 I
36:10 the median six is a way better both are valid. They have a
36:16 . So we just, we just to know more about where did you
36:19 those numbers? So how do we it though as a filter? This
36:25 concept is a filter. Well, I've got a sequence of numbers that
36:30 like this. This is just a binary sequence of numbers, zeros and
36:37 . And I'm coming along and I to enhance this binary sequence.
36:49 if I run a smoothing filter, average filter say that I have a
36:55 point running average filter by that. mean, I'm gonna take five points
37:00 , I'm gonna do something to I'm gonna output it, shift five
37:04 in, do something. Output the filter. If I had 00100 and
37:11 took the average of those values. would that be? Yeah, the
37:19 of these values? Oh, it's 001. So the average would
37:26 1/5. That's right. So So an averaging filter would output .2
37:35 I put .2 here and then it's run along and then when it has
37:44 , it's gonna put 0.4. So gonna smooth that and then it's gonna
37:53 up here and then by the time Output this guy it's gonna output
38:00 And so you can see what the filter will do. It'll just smooth
38:04 of this, which is OK. what a running average filter will
38:11 So that's all good. The median does something that's a little bit
38:20 It does not smooth. So you see that the median filter, if
38:38 a five point median filter, it's look at here. It's gonna take
38:44 , it's gonna take those input it's going to order them. And
38:49 I order those five values and increasing , what's that order going to be
38:59 sequence? That's just the, the order. Yeah. So what will
39:06 numbers be of that five value The input sequence? Well, we've
39:17 the input sequence, which is the I'm dealing with 00100. But what's
39:23 first step of the median filter? going to organize those. Oh It's
39:27 take the average. No, I know what you're asking. I've lost
39:31 . OK? So the median takes input points and it orders them in
39:39 value and then selects the middle OK? So that's the median selection
39:48 . This inputs these numbers which are just numbers. It's going to
39:53 them as in ascending value and then the middle value. OK? I'm
39:59 , sorry, I was overcomplicated. was like, no, that's not
40:02 he's asking me. OK? Yeah, this is really simple.
40:09 , I'm not gonna ask you complicated . It's in real time and it's
40:15 . So it just is gonna order guys. It's gonna go zero,
40:19 got these five numbers. It's gonna them 00001. So that was that
40:25 the the basket of values you gave . I just ordered them. So
40:29 I've got 00001. What's the middle ? Zero? And then I put
40:37 and then I move it. I've all the same. And in
40:40 even when I'm at this middle I've got 10001, it orders
40:45 00011. It's still output cereal. . Then when my midpoint moves over
40:54 I've got 001, What's the order those? The same? Yeah.
41:05 middle the meeting would be one. . And so it outputs this,
41:09 you can see what the median filtering has done, which is very interesting
41:15 unique. It completely rejected this point totally passed this edge. So this
41:39 not smooth those out layers, it rejects them. So this is a
41:46 filter. It complete because it's a process, it can completely reject
41:55 And that's why we like it because this is a noisy spiky glitch,
42:05 completely gets rid of it. So one, this kind of filter is
42:09 a de glitching filter. It'll get of little unusual outlier noises. But
42:21 might like to see this sharp change a lot of what we deal with
42:25 geophysics does have an impedance contrast or . So there's a sharp change I
42:32 want to smooth that I wanna keep . So this filter will pass an
42:41 or a sharp change or a step . So you used to hear of
42:50 image that might have said this is there's an image enhancement here we have
42:55 an edge enhancement filter. This is it's doing. It's taking that image
43:05 enhancing edges by a media filtering. as geophysicists, in contrary to some
43:22 fields, we do a lot of processing and this is a big,
43:28 part of geophysics is how do I , manage massage, enhanced data.
43:38 a big part of what we especially if you're in one of the
43:43 houses, this is what they So if you get a real kick
43:48 of making things prettier, then this a good place to be. If
43:52 don't get a kick out of then you should do something else because
43:55 that's really a big part of the . Uh If you like cleaning your
44:00 , then this is data processing is of a good place to be.
44:04 you hate that kind of stuff, there's probably another place that's better.
44:09 that's not a great analogy. I'm crazy about cleaning kitchens, but I
44:12 cleaning data. So I don't Anyway, it's a thought. So
44:19 can see what we've got here. I'm interested in the horizontal stuff.
44:24 this is a upgoing waves have been to two way time, but there's
44:30 lot of other garbage in here are we don't want. So the way
44:38 median filter works, a simple one just to take a specific time And
44:47 , say five traces at this Those traces have all values. It's
44:53 select the middle value of those when ordered and then output it, then
44:59 gonna move over one trace, take , the samples, order them an
45:04 artor output the middle and run across data horizontally. And this is the
45:12 . So we run across it, across it, run across it.
45:15 da da, that's, computers are at, here's that. But,
45:20 what do you think of the I mean, it looks a lot
45:27 , that's for sure. Yeah. there's stuff that we would anticipate that
45:33 would say is probably noise. I'm at this trace. I'm saying that
45:39 looks anomalous. How do you know noise? Well, I know from
45:45 measurement that I've got energy coming into earth and bouncing back and I know
45:50 the reflection should be aligned. So that looks like this and it's a
45:55 measurement of the reflection. I that's what I'm expecting. That's what
46:00 processed for so far. So this doesn't look like a nice reflection.
46:07 looks like a bad trace. It . So I don't like that.
46:11 I like that. This filter has rid of it. So kudos to
46:17 filter and the thing is, how it get rid of this?
46:20 this represents, if I've got five across here, it might be 50.2
46:25 25.2 point two. So when the goes across here, it just sees
46:31 as an anomalous value and it just it out. So this filter is
46:39 automatic trace editor. It, it rid of bad traces. Plus we
46:50 see that there's some energy that's going here now that is coherent. So
47:01 know that there's something real physics going there. It's just that I don't
47:06 it. Uh What I want right is this nice, beautiful upgoing
47:12 This is some energy that's going In fact, it's, it's coming
47:15 at a very low velocity and it's a tube wave or a shear wave
47:20 something that I don't want. Plus downgoing, it's not upgoing. So
47:25 don't want this and the filter has rejected it. So that's good.
47:45 how did the filter reject all this ? Well, it was looking across
47:50 and it was seeing the reflection .2.2.2 then it hit this big downgoing
47:57 6.2.2 .2. So it only saw down going once across its horizontal
48:05 And so it just rejected it and got this. So I really like
48:11 because it's done my trace editing. gotten rid of residual waves that I'm
48:16 interested in. And now this is enhanced upgrade. Wait. And if
48:27 was being really strict, I should a dashing incidentally, I think uh
48:47 probably talked about grammar league and just reports and everything and we all use
48:52 and, uh, I was just with someone and she was saying all
48:58 our university con, um, Communications is not her first language. She
49:05 something called word tune. I'd actually heard of it before. Hm.
49:12 tune is sort of a chad a bought and she said she writes her
49:19 then to, it made me The word, the word, word
49:28 , word, tune. Completely corrects grammar and the spelling and then gives
49:34 a dozen alternative ways to say that . I heard on the radio there's
49:42 new, uh, something that a of the high school kids are
49:47 It's an A I kind of, , idea and they'll, you just
49:53 it, like, I want to a paper about, I don't know
49:59 , the, the Boston tea party it'll write the entire paper for
50:05 like, correct and everything. it was like, what? So
50:08 lot of teachers are having to, , flag that right now because it
50:11 pick up on, um, like, uh, what's it called
50:17 you steal somebody else's plagiarism. It doesn't pick up about plagiarism because
50:22 technically being, like, freshly So it's a, I don't remember
50:27 name of it. It's like chat . T, yeah. There it
50:31 . Yeah. Yeah. It's, , it's an A I writing tool
50:37 we've been testing it and using it to see, uh I asked him
50:42 give me hydrocarbon targets in the Gulf Mexico and to write me a story
50:48 it did do a good job, know, it was uh actually it
50:55 pretty good and I'll, I can why it was pretty good. It
51:00 me some background about the Gulf of and ex exploration of the Gulf of
51:04 . And then it, it recommended we talk to a licensed geoscientist about
51:10 specific targets. Did it solve the ? No, but it wrote uh
51:17 wrote about it and it gave some advice. Hm. But for
51:24 for certain things like you're posing write me a paragraph on the history
51:30 the events of the Boston Tea It will do that in a
51:36 Mhm. And so to be really at this stage, there's no point
51:43 anybody that assignment. Yeah, because JP T or any one of the
51:52 bots will nail that. Yeah, were talking about it on the
51:57 So this teacher called in and said makes all of her students um do
52:01 assignments in class now and she has like stay in there and watch everybody
52:06 their computers and everything to make sure using it. We kind of have
52:11 be uh you know, the uh of mine, Ken Tubman, who's
52:17 of the S C G right He wrote about this stuff and
52:21 is this stuff really happening in the ? Are you, how are you
52:26 this? Is it true that it's easy to respond to exams? And
52:31 are you doing? And I well, for certain kinds of
52:35 yes. Chat GP T will give superb answer. Uh, like for
52:42 , a descriptive well written answer. fact, I can, I can
52:50 that because virtually no students, none us write that well. So you
52:56 it and you say, you know English is your third language? There's
53:00 no way you wrote that. I tell you right now, you did
53:04 write that. In fact, I had a case of this. I
53:08 know that I mentioned it to but one of my students and she's
53:11 , uh love her to bits. We were writing a paper and it
53:19 good work. She did it She has a phd here and it
53:22 , it was OK. She wrote paper. I looked at the
53:25 It was, it was pretty I made a bunch of recommendations.
53:29 corrected, it was ok. Then had to submit it and she wrote
53:35 back and she sent me the paper its grammar was perfect and it was
53:43 sophisticated. The writing was very But when I was reading it,
53:48 was, I thought this is just little bit weird. It's like a
53:53 nerdy post phd graduate from Cambridge who's little whacked out. And so she
54:05 and she said I did, I the full paper and everything. I
54:08 all your recommendations. I thought about . I ran it through grammar league
54:14 then I ran it through chat T one of the processors and an
54:19 I processor. And here's the And I thought, oh my
54:25 And it's submitted. So, does get to be plagiarism? Well,
54:35 , it's close. Mhm. For , I tell everybody to use grammar
54:42 and I feel that's good. That your typos. I use it.
54:46 it catches a typo, it you might have changed tenses, you
54:50 have had something funky with your grammar whatever. So grammar is good.
54:55 your work. It's tuning it word tune can express things a little
55:01 differently. So if I submit an article to the leading ads or
55:06 of the magazines, typically their editor edit it and make recommendations, send
55:12 back to you. And typically I say, hey, you know
55:16 Thank you so much. It reads little bit better now and great.
55:23 I think all that's fair. Now take that and you submit it to
55:27 GP T and it searches the whole and everything, anything related to what
55:34 talking about and it can slightly alter writing to include everything in the world
55:41 is found. Now, that's getting little bit funky and that's with your
55:51 work. And so I don't think too bad but you have to go
55:54 and did it, did it include else that you don't know? Did
55:56 start to lie? one of our submitted um a question to chat
56:06 T that asked, why is earth away from the Sun than Mars?
56:13 of course is not true. And GP T wrote a beautiful paper that
56:20 totally wrong, but it was gloriously . Yeah. So it's a bit
56:32 Google. It's obviously the next stage Googling something. So normally we ask
56:36 question, Google gives us a bunch references and some answers and then we
56:41 that. So what chat GP T doing is it's writing you a whole
56:50 on that answer. It could be wrong. Yeah. It's just like
57:02 when I ask Google, what's the of salt? Google is gonna give
57:08 500 references on the density of I can look at them and then
57:13 decide because I know what the density . I decide which looks right and
57:17 check it with everything I know and da da and then maybe I'll take
57:21 number and I'll reference it. So like chat GP T you would
57:28 it something and it's gonna give you whole paragraph on that. Well,
57:36 everybody in the world was kind of the same way, would probably tell
57:39 the right answer. But if there whole poly guys in Russia or someplace
57:44 were trying to fake it and they the value salt as eight g per
57:50 C. It would start to write g per C C. Mhm.
57:56 we've trained it. We said that's right answer. And it says,
58:00 . Ok. Hm. So it's tricky place right now to fight.
58:10 is futile. It's like, it's a teacher saying, you know
58:19 You can't look up the value of on the internet. You have to
58:24 Encyclopedia Britannica in the printed version. , nobody's got that. And even
58:31 I did, I have to get my butt and go and find a
58:35 and then look it up and I'm gonna do that. So to say
58:41 people can't use chat GP T is . Everybody's gonna use it.
58:49 I had never, I had never heard of it. Yeah.
58:55 it's there. Uh, give it , give it a whirl. We're
58:59 to do it because we do You're doing exams and you've got to
59:07 exams that are fair for starters. got to get ex give exams that
59:12 , evaluate people so that they're certified that somebody else can trust them.
59:19 like you, if you give your to a babysitter, you sure want
59:22 make sure that you trust that Yeah. Uh, that's why most
59:28 don't give their kids to somebody who's a family. Why, you
59:30 I don't trust you or if I'm trust you, I wanna make sure
59:35 you've got some references and you've got certification and pediatric problems and whatever because
59:43 is valuable. I don't want you this up. So, we've got
59:47 figure out how do you certify people they, um, that they do
59:51 what they say they have and then do you protect an honest person from
59:57 dishonest person? Mhm. So that's we have to pay attention to evaluations
60:06 , you know, in a big , all the students are working away
60:08 one student might not be using chat T and everybody else is, and
60:13 all of a sudden everybody else's paragraphs in perfect and this honest person didn't
60:20 it and they're penalized and that's really happening. And so you're ripping off
60:27 honest guy and, and nobody wants do that. So we have to
60:32 to say, hey, look I know you've got access to
60:35 I know you've got access to I know you've got access to chat
60:38 BT. So, how else do demonstrate your knowledge? Mhm. And
60:47 teacher that was writing in and Yeah. How do you do
60:52 So, with that thought, let's a couple minutes break, uh,
60:56 can meditate on that and then we'll back and, uh, and do
60:59 more here. Ok. Ok. soon. Ok, great. Uh
61:06 continue on um thinking about artificial as as human intelligence here. So where
61:19 work stops and we start is But uh in a sense when we
61:23 of all this stuff, we're using to process data, to turn on
61:27 lights to pump our water. So that's all good. Um When a
61:34 refuses your credit card, that's So uh just in the research
61:41 this was a little bit of an . So I described how we could
61:47 the median concept as a filter to to get de glitching to passages.
61:55 uh we can also extend it to D and 3D and we did a
61:59 time ago um do some of these so that you could take a box
62:04 data, not just a line or could take a volume of data and
62:08 glitch the volume. And the basic is that whether I've got a line
62:13 data to uh order or a box data to order and put it in
62:20 center or a volume of data to . And then put in the
62:25 we could use the median concept for of those data sets because they're all
62:31 numbers. And if I've got a volume of numbers, I can
62:35 all those and then select the middle and I put it at the center
62:39 I could run this filter all over volume. Likewise, some of our
62:45 use weights. And so what I was that how we can make that
62:51 a medium filter? Say we want pass dips. I don't want to
62:56 rid of this dip, but I to pass the dip, then we
63:00 how to do that with dip, filters that have different weights. And
63:09 the concept there is that if I to pass dips, then I just
63:17 the number of times that data are the dipping of planes. So take
63:24 volume. And then if I want pass a dip or a couple of
63:30 , then I just repeat all of numbers to enhance the number that they
63:34 . Repeat them all, order them . And then I put that.
63:38 you just repeat certain numbers if you to make them more important. And
63:44 was the basis of having these dip filters and they can work pretty
63:49 So we can take this medium concept um make other filters out of that
63:53 do more sophisticated things. So let's look at this processing again, we
64:00 our raw data on the left, it align it, enhance it,
64:11 the downgoing, put it back in original form. Now without the downgoing
64:16 and moved to two way time to the upgoing, then there might be
64:22 some junk left here. So I window about the first brakes stack the
64:30 and that's my V S P extracted . Now, why would we do
64:41 corridor windowing? And we can look this idea, we know that um
64:48 is where the downgoing energy was coming . Here, here are the primary
64:54 . But you can see as we back to the surface, we've tried
64:57 , but there's other junk in the , we're losing the amplitude. So
65:01 area is valuable, but we're losing . So the very simplest thing we
65:12 do that's mindless is saying, you what I don't really like what's going
65:20 here. So I'm just gonna zero . So in principle, the downgoing
65:28 is coming through here, it's sending our primary reflections. This is beautiful
65:33 close to where the reflections start, start to get into multi passing and
65:38 of signal through attenuation and everything. I'm just going to admit that,
65:43 , OK, well, that's just bad. Nothing I can do about
65:48 . I'm gonna mute all that stuff I'm just not gonna take it into
65:54 stock because it's degrading my stock. I'll take a corridor of good high
66:02 primary data and just zeroed all the and then stack this together and that's
66:09 my corridor stag. And it's getting of any residual bouncing around here or
66:19 loss of signal or attenuation or other stuff that I haven't been able
66:25 to filter well enough. So that's corridor mute and then corridor stack.
66:42 what does that look like? in a case like this, we've
66:47 depth again. Here's a log and is my Sonic log from 1400 m
66:55 2600 m. And it's plotted in per meter. So going from 100
67:02 to 400. So this area is fast or slow the transit. So
67:13 transit time, reciprocal. So it's . Yes. So it's got big
67:23 time. This is slowness. So got big slowness. It's slow,
67:30 a long time to transit and then get down into this area. What
67:35 this area down here? That's It's got a very small transit
67:42 So it's fast and then we get but is the sediment getting faster or
67:49 as we get deeper here? It's slower. Yeah, it's got this
67:53 slow, low velocity stuff which happens be a big shale And then we
67:59 down deep 2600 m. So pushing ft slower fast down here, it's
68:09 faster. Yeah. So if we Gardner's relationship, which says that density
68:21 proportional to velocity to one quarter. is this gonna be high or low
68:29 here? That's gonna be be faster low density. I asked him,
68:47 ? Hold on, stop. Um would be a low density.
68:56 is it slow or fast? It's . It's fast. So density relates
69:03 velocity they reverse. So it would a high density as a guess.
69:21 , in general, yes, and is this is quite high velocity.
69:29 it's almost it's 100 microseconds per So went over that one, over
69:46 . Yeah, I was just trying calculate the velocity in my mind.
69:50 So this is, this is pretty . We expect it to be pretty
69:56 and in fact, it is uh a carbonate. So yes, it
70:07 . So we've just had a quick at the uh the log.
70:16 if you were going down here, is the, this is effectively the
70:21 the velo high velocities down here, velocities up here. So really,
70:26 going in this section, we go a high velocity to a low
70:34 but that's fairly well defined. So here's our V S P, this
70:42 in depth Condaded to two way So if we go across this
70:57 should that cause a reflection? it certainly should. We've got a
71:04 velocity change. We expect a big desity change, we expect a big
71:09 change and we expect a reflection And so if I come down
71:17 here's depth, the same depth, plotted the log at the same depth
71:21 the DS P. So I come and I look here and sure
71:27 there's a pretty nice kick. So all good. Then as I come
71:47 farther. I see another slow, least high to slow velocity here.
71:54 there's another pretty big velocity change. I'm expecting to see a reflection and
72:03 , seismic looks like it's working. . So this is my corridor
72:09 And the way I got that was to take uh a chunk of this
72:13 P. Get rid of this stuff it's a little bit noisy. It's
72:17 bad, but it's a bit So I'll get rid of it and
72:20 stack that across this gives us our S P extracted trace or corridor
72:25 And now I'm gonna compare this guy surface seismic. So that's what we
72:32 do. Now, let's do precisely . So I've got my standard surface
72:50 here, a little chunk of P data. And I've got my logs
73:02 depth, the logs that we've now to know and love gamma ray
73:07 S P the impedance, the product density and velocity. So those are
73:16 logs in depth. My BS P in depth shifted to two way
73:22 kind of a lousy BS P. that's what we've got. We can
73:27 that there's not too much back So I'm just gonna mute that and
73:31 rid of it. So here's my , that's got fairly good data.
73:36 going to mute the rest of Stack the corridor to give this corridor
73:42 , which is just my best V P trace. Now, I'm gonna
73:50 that V S P to the surface and try to interpret the surface
74:00 Now, the way that I know is because I understand the logs pretty
74:08 , but we could take a look some of the logs. So the
74:18 ray is up at the top, going from 0 to 1 50 And
74:26 the SP is going from 0 to . It's pretty small. It's kind
74:34 hard to see. Oops. So you to interpret the logs,
74:59 can you interpret the logs for me from the top here, the shadow
75:04 deep. Just give me some gross of what's happening with the logs.
75:12 , we have a Loma right there about 2 50. Then where's
75:23 Around the, the gamma is going at like 250 right there between 2
75:31 and 2 75. Yeah, right . Yeah. But generally starting from
75:36 very top, it's a high Yeah. So this whole area looks
75:42 of what? Just, hi. , Shay. Yeah. So that
75:49 area looks pretty Shay. This is to get not too bad around 50
76:01 the very bottom of the, it looks like it really gets
76:07 Ok. So just, it's generally Shelley at the top. It's got
76:13 couple of nice little units. Gets a game down here and then it
76:21 and then the S P S I mean, it's relatively low
76:31 There's not a lot of change to . Well, we see a couple
76:36 here. So it, it looks there's a kick at 3:25. So
76:39 looks permeable. Some of these cases interesting. So they're, there are
76:47 permeability intervals. OK. So now we go down to the impedance,
76:54 this is plotted from four million to million. So this is getting greater
77:00 , which we would interpret it as velocity and higher density. So we're
77:10 from low impedance. Mushy mushy That's agrees with this crappy rock up
77:22 . We get some places where it's , it gets kind of crappy again
77:28 then gets harder. And this is . So we're thinking again, Clay
77:39 , maybe some more competent sands. so um we kind of understand the
77:46 a little bit plastic section pretty Then how does that manifest on
77:58 We expect these big impedance changes to a reflection? Mhm. So there's
78:09 nice reflection down here which we interpret can you see that? Mhm That
78:20 , that high impedance spike in Yes. So when I'm looking,
78:25 I'm coming down here, I oh, there's a high impedance
78:27 I should really see that on So I come down here here
78:31 Boom there it is. So I've a very good idea of what that
78:37 is. They've called It. The 20 so I definitely believe that
78:44 I can see it everywhere and I where it came from then from the
79:00 , we can, we can look some this this gets kind of
79:08 This is this mcmurray sand that's got the heavy oil in it.
79:15 But we can also see that this whole area is sitting on top
79:19 a Devonian carbonate. So this is the carbonate here. Now, I
79:23 see that in the surface seismic pretty and we definitely see it in the
79:30 S P and it's right at the bottom of the well. So the
79:36 just start to get into the top that. But we can see the
79:40 ray really cleans up, we're going the top of the carbonate and you
79:47 certainly see it. So this is into some of the interpretation how we're
79:56 to put the logs and the V P together to interpret surface seismic.
80:10 again, we would, when we're at this circus size, we just
80:15 its own, we don't really know going on here. But now with
80:18 correlations, I know that that the right there is gonna be the top
80:24 the Devonian. And so now I take that Devonian top if this was
80:38 volume and pick that surface, find surface auto pick it. I've given
80:44 some character right here and then have computer search around for that character and
80:49 the surface. And that is the top of the carbonate surface. And
80:56 gonna be looking for topography on maybe changes in character, maybe something
81:04 is there water on the top of ? Because that's what I'm worried about
81:07 . My oil is up here, I want to drill and produce this
81:11 area and I don't want to drill water. So there might be something
81:17 this um Seismic Amplitude that tells me we're going from uh brine saturated to
81:29 saturated or low porosity or something. I'm gonna pick this surface and then
81:34 looking at that surface in a lot detail to see if it makes me
81:38 drilling into water good. So once , just in a little bit more
81:49 , we've got the BS P in schematically and two way time energy is
81:56 down causing a reflection, there could some bouncing around in here. So
82:02 we just mute all this stuff, it gets rid of any possible
82:09 And so that's the simplest filter at of all is just to mute
82:23 OK. So that's, we've talked that. Once again, we'd have
82:28 energies coming down. So we're looking depth and time uh energy is coming
82:35 , we're just gonna mute and retain red spot because that, you
82:39 doesn't have this data problem in And so we just get a very
82:45 stack from it, cord, our . And that's typically what we're gonna
82:49 . Just an easy way to get of the stuff we don't like via
82:53 our simplest most effective filter. there's another thing that we've talked about
83:12 little bit back here was the, the multi, multi pathing. And
83:20 we said our direct rival is coming here. It bounces back to the
83:25 , primary reflection. We love but it can also bounce off the
83:30 and come back here, hit this bounce back and keep on doing
83:36 So in this area, there might multiples and that was one of the
83:40 to mute it. But and so were muting around the primary area.
83:48 if we stack this whole thing, all the data, then we include
83:54 the multiples. So if I stack all that has all the multiples and
83:58 I just stack this part, then has gotten rid of the multiples and
84:03 can see the difference. So where we, where are we gonna use
84:08 ? Well, in a lot of seismic, even when they try hard
84:12 process and get rid of multiple, there are multiples still left in the
84:16 seismic. So the V S P help us identify those because we can
84:21 mute the V S P to get of all the multiples. And we
84:24 what we're doing surface size, make often harder because they have the same
84:28 as other reflections. So here's an where from the V S P as
84:37 as the synthetic Seismo gram, we see a fairly coherent, consistent
84:47 But there's lots of other stuff that's on the surface seismic. And we
84:54 see that on the synthetic generated from sonic logs or the DS P generated
85:00 real seismic. So we tend to that this stuff, I don't see
85:08 . So I think that's multiple. surface se data processes go back in
85:15 look more closely at this guy and to get rid of that because we've
85:21 it and we know that there is in there. There are no events
85:26 there. This was an artifact of bouncing around inside the earth. So
85:33 identify it. This other stuff we see that these, that's beautiful primary
85:42 . It ties nicely to all the that's beautiful on everything. Synthetic V
85:50 P. Surface seismic logs beautiful. green guy really definitive on surface
86:01 a lip broken up nothing in nothing in V S P. That's
86:05 artifact. We look at this guy event on all the logs DS P
86:25 . I believe that right below There's an event I don't see that
86:29 V S P or synthetic or logs believe that this event is good.
86:39 a reflector, big, big, , high velocity change. Nice on
86:48 synthetic, nice on the V S great on the surface size. So
86:52 believe all that. Now, in case, the uh we've um calibrated
87:01 , the sonic logs. So the synthetic and the V S P
87:05 pretty closely. So that really increases confidence. So I can understand the
87:17 , I understand the synthetic response of log, I understand all that.
87:23 when I compare it to the BS which is real data, the response
87:28 very, very similar. So I like that and I believe it now
87:34 I believe our interpretation and then when correlate that all to surface se I
87:41 there's a good tie in areas but in, in other places. So
87:44 tend to think that the surface seismic has artifacts in it. And I
87:48 believe those and I'm not gonna correlate up and say that there's a play
87:52 there. So when we have the and the synthetic seism gram and the
88:04 S P and the surface seismic, can start to come out with very
88:09 stories. So in, in a of cases, you might get dumped
88:20 Venezuela or Algeria or some other which is all places I've been dumped
88:25 . And then you're asked to interpret data. And if they've got logs
88:30 A V S P, then the it can be pretty straightforward and you
88:35 make an interpretation in half an even if you don't know anything about
88:39 geology. So say, you don't anything about the geology here, but
88:48 can interpret these logs and say more less what's going on, give these
88:52 some names, correlate them up and this fairly fast. Likewise, with
89:02 guy, if I start to give formations names, I understand their seismic
89:13 that I can start to pick these and extract them. And I'm pretty
89:20 what it is. So again, lot of this stuff is not to
89:29 that this is the only interpretation. just to say that I've got a
89:36 of evidence that this is what's supporting interpretation. Plus, you might have
89:46 and the partners have processed this data and it might have a different
89:51 But you can go in and look at here is the log,
89:56 our simple response to the log. my straightforward process in the E S
90:01 I know this signature and I'm gonna the middle of this and I know
90:06 the correct interface and here's my So your partner might have done things
90:16 little bit differently. But when you all this evidence, this is pretty
90:33 . So once again, we could through this and we've got our gamma
90:37 , we've got S P. So example, you could see S P
90:44 here. That's evidence Gava is a bit low. So that looks like
90:49 top of a sand come down come across. This is looking like
90:55 seismic response to the top of that . So that's how we would,
91:02 interpret it. Now, this is , pretty crummy data, but that's
91:08 what it is because there's Musca and kinds of marshy stuff up here.
91:11 it's hard to get really good So you really need to work on
91:14 interpretation and that's what's what's key here have the V S P. So
91:23 another case logs in time synthetic seism , BS P and then the uh
91:41 V S P put into the surface So now we can start to
91:50 I'd be a little bit worried about guy, maybe nice, tight,
91:59 good ties all the way down. that gives us confidence to interpret what
92:05 these horizons are and to go back the logs. So once again,
92:14 has been mapped to uniform time, each one of those times to eight
92:22 corresponds to a depth. So remember , we said very approximately if the
92:34 was around 2000 m per second, is, it is a lot of
92:37 time that the time in milliseconds is equal to the time, at least
92:45 depth and meters. So you can another case here, 3100 milliseconds,
92:51 seconds around 3000 m. So you ask, well, if you've
93:07 well, logs and synthetic seism Why do you need the V S
93:11 ? And that's a good question. we've talked a little bit about that
93:15 partly it's the logs only around, about a foot around the,
93:20 that's one reason. So they might correlate in the more macroscopic sense.
93:26 sonic velocities are a little bit different the seismic velocities. The well,
93:30 only go to the bottom of well, the V S P is
93:33 reflections from below the bottom of the . And the V S P is
93:42 seismic and the surface seismic is real . So they're a little bit,
93:49 more or less brothers and sisters as to second cousins, all related,
93:56 some more closely than others. So to just summarizing, we've been
94:04 a little bit about the uh how acquire V S P data. Uh
94:10 original tools were geophones. Then we into accelerometers like M MS micro electromechanical
94:16 that were electric sensors. And now moved also into fiber optic systems that
94:27 making a big difference. So that's way we acquire the data with impulsive
94:33 , whackers or vibratory sources. We uh about how we extract rock properties
94:40 well logs from the seismic and then we make these interpretive tools uh with
94:46 reflectivity. OK. So that, finishes the basic um zero Offset DSP
95:12 . Any questions on, on most that Stephanie Immediate questions. I don't
95:18 any immediate questions. I just need let it digest. Yeah.
95:22 definitely. Oh, and I sent an email with the, um that's
95:43 Tria, I sent you an email a link to the Triax um,
95:48 equipment he used to use for those tests. Yeah, thank you.
95:52 , I got that. I had quick look at it. Thanks.
95:56 It's, oh, I might have look for some of that, see
96:02 we could read it or, or there might be a cheap version of
96:08 that, that we could do something , but I'll, I'll have a
96:13 at that. It just started me that uh we begin with our field
96:18 . We uh we had this opportunity spend a day doing soil testing.
96:25 , you know, we were originally kind of Strat graphic description and uh
96:31 chemical testing, but it'd be nice do some mechanical tests too. You
96:38 , there's some other simple tests that use called penne meters and it's just
96:42 you whack a spike and see how it goes. And that's believe it
96:49 not, that's a fairly good test soil strength. We used to have
96:55 , it was called a miniature vein test. And it was literally just
97:00 it was a thing that had some on it into the clay and you
97:05 turn it a little bit and when stops increasing there's your moment of failure
97:13 that was it? Oh, that's great. That's, uh,
97:18 , that's, that's the kind of . Thank you. That,
97:21 that I was looking for, that'd great because that's really inexpensive and pretty
97:28 . And it's, it's understandable Mhm. Yeah, that would
97:36 that might be something to, to at at. Huh? Oh,
97:43 . Ok. Um, let's, continue on just for a couple of
97:50 and then we'll take a break. We had this concept that uh we've
98:00 dealing with zero offset and we've been of imagining that everything's flat. And
98:05 developed uh an interpretive set of tools allow us to take well, logs
98:12 them into time and then see what seismic response would be and then tie
98:16 all together with surface seismic. So all good. But we all also
98:21 to start making a picture and we starting to make a picture from reflections
98:33 are away from the, away from well itself. So for example,
98:40 might remember this type of construction if had a source here that created a
98:49 and that vibration went down and, hit a dipping plane and we received
98:54 at this receiver. And I got seismic data here. Where does most
98:59 that energy come from? Where on surface? I mean, it would
99:08 the point where it hits on that , right? It is, but
99:14 on this interface. How can I that out? Say I've got this
99:22 but how do I figure out where hits? Um oh, it's that
99:33 not the Python. Well, Pythagorus would probably tell us somehow.
99:45 , but there's an easier way to it. And it's called the method
99:49 images. And it's to take the point and the dipping plane and just
99:59 a perpendicular that goes from the receiver the plane. And then put that
100:05 on the opposite side, connect the and then that gives you your reflection
100:20 . And so why it's called the of images is that this is the
100:25 receiver, but you make an image reflection of that receiver in the plane
100:32 this is just a way to construct . So what does that do?
100:39 this case, we would take our here construct a line perpendicular to the
100:47 , get the length of that just put it on the other
100:51 And then where that line ends join to the source and where it intersects
100:59 plane, that's your exact reflection So this is just assuming that angle
101:09 incidence is equal to angle of So that's what's assumed here, which
101:16 our normal maximum specular reflection. So if this little particle was coming down
101:27 , if we were shooting particles, , boom, boom, all different
101:32 , the one that hit right here bounced would be the one that bounces
101:36 to the receiver. Now, I a practical application. This is what
101:52 was mentioning. So this is the game of pool and this is I'm
102:05 gonna change that a little bit. , there it is. Are these
102:12 posted that you're uh, yeah, , they should be Because I'm looking
102:18 10 and I'm not seeing, never mind. It's like for whatever
102:24 it's my slide 11. OK. , I, I jumped ahead a
102:28 bit. There's a I'm just gonna this before we break because this
102:35 uh this is kind of key to all the offset mapping. Uh
102:43 I don't know why that I can get that billiard ball to be
102:47 It should be white. No. , I'll have to work on
103:00 Um So this is, this is way, uh the way pool
103:10 the cue ball, that's the ball hit and then you have these other
103:14 balls and then these are counted as . Actually, I said to these
103:19 counted as one. The pink is black or seven. So the idea
103:25 this game of billiards is you take cue ball and you've got a
103:29 a red. Then when you sink red, you can sink any of
103:33 colored balls and then you sink another , then you can sink a colored
103:38 . The colored balls always come back the reds just get sunk and they're
103:43 . And so you're all playing the game, uh, you're all trying
103:50 sink reds and then colored balls and game is just once, all,
103:54 , once all the balls are the game's over and whoever has the
103:58 points wins. But once again, you can touch a colored ball,
104:03 have to sink a red ball. in a sense in the game,
104:16 both, you're trying to play your game, which is to sink as
104:22 balls as possible. That's your But you're also trying to make it
104:28 for your opponents in this game to balls. So you're always trying
104:35 what's called hook or snooker or have your opponent block. And those
104:44 all terms for blockage. It's called the opponent or snookering the opponent or
104:51 the opponent blocked. So if if I took a shot, I'm
104:54 try to leave the cue ball behind colored ball so that the next person
105:01 hit a red ball that makes it . So when you play the
105:07 you've got to get, figure out to get out of this problem.
105:10 do I hit a red ball without a colored ball? So what do
105:16 think? What are you gonna You gotta hit a red ball and
105:21 cannot hit a colored ball hit off the side and try to hit it
105:31 like do a bounce bounce off. . So these are called rails.
105:36 you go. I'm gonna think of name. Yeah, the rails of
105:39 cushion. So we're gonna somehow try hit off the cushion, but you're
105:46 geophysicist. So you know the method images. So this is just exactly
105:57 the seismic bounce. So we can the distance from the cue ball perpendicular
106:04 the rail or the cushion position ourselves closely as we can that distance away
106:13 then have a look and then just try to mark the place on the
106:20 to hit and that's gonna go hit red ball. And if you're kind
106:29 a sly and diplomatic, you can this when you're playing a real
106:35 So I'll, I'll sometimes do this you're not gonna get beaten up.
106:42 . If it's tough people, they're not gonna let you do this.
106:46 , but you can casually walk around mark your mark your cues. So
106:49 again, distance to the rail, distance, just take a look more
106:54 less that distance away. Sight the you want to hit, mark the
106:59 on the rail or the cushion and go back and hit the ball and
107:05 works pretty well. And it this is just angle of incidence equals
107:13 of reflection. And if there's no on the ball and you don't slide
107:17 on the cushion too much, then going to hit. So this is
107:23 the, uh, the, the application of how to figure out where
107:31 reflection point is. So that's how figured out. Ok. Um,
107:44 just going to, um, jump show how we use that now.
108:05 for P waves that we can do and in fact, that's a really
108:09 exercise. We've got a source say got, um, I'm just gonna
108:21 this on, um, and oh, it's uh not cooperating.
109:06 , suppose we have a, suppose have a layer right across here.
109:22 I could imagine the source radiating So the energy is coming down,
109:26 gonna bounce off that layer and it's be captured here. We could ask
109:32 question given all different layers say let's this one receiver given all different
109:43 where is the reflection point that's captured this receiver in all the different
109:54 And what you'll find is that suppose was a layer right below here,
109:59 I would just do the method of , connect the dots and find that
110:03 a layer right about here, the point is gonna be there. So
110:07 I've got energy that's I've recorded at level, I find that it came
110:14 this set of curves. So once , if I had a source here
110:29 a receiver here, and I imagine the earth has all kinds of
110:34 then where does the reflection occur for receiver? And this trajectory is where
110:45 the reflections come from. And I find that just by using the method
110:52 images. In fact, a woman Cono Phillips was the first person,
111:02 , way, way back to figure how to do this. And she
111:07 , it was called the V S CD P map, Kate Wyatt.
111:14 she got the patent and the Pat in the back for it. But
111:20 all based just on that very simple idea of the method of images.
111:27 that's how the BS P CD P works. So when I've got a
111:32 trace in the V S P, is where all the reflections came
111:38 So from every one of those traces take the energy and I just put
111:47 back on this locus on this trajectory then that makes a picture and then
111:54 don't like all that stuff. So gonna put bins and just stack across
111:58 bins and then it's going to look regular seismic but with a funny half
112:04 , half tooth shaped coverage. So I had BS P receivers at this
112:17 of the, well that the energy the top receiver gets is down
112:24 the mid receive, excuse me, these receivers have energy here, I'm
112:29 bind like this stack into the So now it looks like vertical
112:35 So this is my V S P . I've got receivers along here.
112:42 got a shot up here. And is the kind of picture that I
112:47 from the reflected V S P data jumping, jumping on just so we
113:02 this. Then you can take a break when I do that, I
113:08 start to make a more enhanced composite . And in this case, once
113:17 , I've got my p wave logs 15, 50 m to 34,
113:22 m. So all the different logs we've talked about. Well, some
113:25 them, my BS P in two normal this time, my V S
113:32 extracted trace from the corridor and then data that's mapped with an offset
113:39 This gives me a little part of picture. OK. Here's another one
114:07 let's spend a little bit more time this guy. So here are our
114:23 logs again, gamma ray from 0 1 50 or so Slowness from 100
114:34 per meter to 500. And then depth of the well is 600 m
114:39 to 1800 m. So please describe me as we go from the surface
114:46 here, what's happening? Well, have at the surface we have a
114:58 gamma and then we go really So what's that high gamma tell
115:07 Maybe. Yeah. And then we to maybe sand, certainly clean.
115:17 Mary. Yeah. And then we maybe a small shale layer again.
115:25 . And then we drop back to like very clean. Yeah, it's
115:32 a really big section too. And what does, what does the P
115:40 , what does the slowness tell us ? So, we are.
115:47 it's opposite of what I think it . So that's a high transit
115:52 So it's very slow in the Yeah. And then it gets very
115:59 . Yeah. So the fast transit then where we have that shall layer
116:10 , it slows down again. And then in that sand it
116:18 it's very fast again. Ok. then, so would this be
116:34 Where or would we need more information tell whether or not it's gas?
116:43 , where are you thinking in the ? Even this, this area
116:48 Yeah. Uh Yeah, we we don't have any resistivity log or
116:57 here. So there is, you , in this area where if there
117:09 gas in here, what should it to the, the P wave
117:15 Oh, it would make it Yeah, never mind. Yeah.
117:21 I would say no, there's no there. Ok. I, I
117:24 mix up the slowness and the Yeah. So now this area though
117:32 getting slower and dirtier. So I know. There could be something saying
117:42 , we don't really know right now then it's slower down here. So
117:50 , and it's clean. So actually , this is a very good
118:01 Ok. In fact, this is the well was drilled Oh OK.
118:07 you're right in trying to think about . So once again, we can
118:13 a kind of a dirty, slowish consolidated area. These are all cretaceous
118:19 , they're younger sediments. And then go into primarily a carbonate section.
118:27 , in this carbonate section, there a couple little sandy shales. So
118:34 can see all that. Now, , what I'm gonna do is we
118:41 take a break. But what I'd you to do is think what should
118:46 if I've got this P wave Sonic this kind of rock change, there's
118:51 big change here. So what should see? And how would that
118:57 Well, you would, you should a reflection because it's like an interface
119:01 big time. Mhm So the V P is in depth here and these
119:07 the same depth scale. So if drop down here, what should I
119:14 in the V S P? You see a reflection right there. There
119:19 is huge. So that's at that and I'm getting this reflection and I
119:28 it in the synthetic, I see in the V S P. And
119:31 I take a little chunk of seize, guess what I see it
119:35 the surface. And then when I an offset processing, I see it
119:54 the offset too. So this is is a very, very strong reflector
120:00 it sure should be because the mythology the all the properties are changing big
120:08 . We're going from the Cretaceous in top of the Mississippian. So,
120:12 a plastic section that's mushy gooey to hard carbonate limestone. So it's getting
120:24 and it's getting very fast. Now, it, it turns out
120:40 all the, the explorers in this , we know that this is a
120:44 section. We know that this is a carbonate section and there's this anomaly
120:53 we've said it's clean. But before well was drilled, all I had
120:57 the surface and the surface seismic said down here there is this event and
121:03 can see that event. Yeah, huge. So people went out and
121:10 shot seismic all over the area and thought that this could be a huge
121:15 field because we know that this is uniform carbonate and there's a boomer of
121:23 event. And so that means there's big impedance change and we don't really
121:36 that that maybe is lih it sure like there's maybe Doma organization of the
121:43 which creates fractures which can become porous permeable and gas saturated. So this
121:52 looking like it could be a big field. Mhm So that's why the
121:59 was drilled. Then the well was and you can see what really
122:09 So yeah, so there is, a carbonate area, but it's also
122:15 evaporate, you know, they there other marine kinds of sediments in
122:25 So it turned out that yes, is a boomer of a reflection and
122:34 , it is a low velocity layer is salt low velocity or high velocity
122:44 question. Well, it's not a question. It's a complicated question.
122:51 , it's a, isn't it a velocity? It's a high transit
122:57 but slow velocity Salts a little bit . It's a fairly high velocity,
123:08 600 m/s. So that's a fairly velocity in the near surface. It's
123:15 very high velocity because what, what we say was a good number for
123:18 wave velocity in the near surface? 2200 m per second. So 4600
123:25 per second, relatively fast or fast, fast. So if I
123:32 a salt dough out around humble or or um Hockley or Pierce junction,
123:46 rock is really fast compared to the sediments. However, if I'm down
123:56 13,000 ft in a carbonate section, carbonates or even faster, They might
124:08 6000 m/s. So they're fast. down deep salt is relatively slow if
124:15 in a carbonate section. So at surface it's high uh down it's
124:20 Sorry, you, so you're saying surface it's a fast velocity and as
124:25 get deeper, it's a slower Well, no, the salt itself
124:30 always about 40 600 m/s. It change velocity but comparatively the near surface
124:39 are usually classic, they're usually unconsolidated they're relatively slow compared to salt.
124:46 always stays at the same velocity. much. It changed a little bit
124:51 not very much. Yeah. So was like, wait, what?
124:53 . I was like you were I was like, hold on
124:56 Yeah. So when we go the salt is still the same
125:00 the same old guy and it's relatively compared to those really high velocity
125:07 OK. And you can see that that we've got our high velocity carbonates
125:15 then the salt gets relatively slow and we go back into high velocity
125:21 OK. That makes sense. So, but you can see the
125:25 here if I compare that to the surface, this is not as slow
125:30 the near surface. OK. So incidentally on the P wave, this
125:58 a real boomer and we can see it's got a very different velocity and
126:03 extremely different density. So it relatively here which have velocities around 6000 m
126:11 second plus are high density. So have a very high impedance. The
126:18 has a low density and a relatively velocity compared to these sediments. So
126:25 gives rise to a huge impedance which is right on seismic. You
126:29 this enormous event. So that got excited thinking this could be gas
126:37 but it's not, it's. So the P wave world, it looks
126:45 it. We were advocating because when shot the DS P afterward, we
126:49 that the converted wave show is a strong signature too. And if this
126:57 strictly gas saturation, we know that doesn't affect the shear wave properties that
127:04 . So if this were gas, shouldn't see that much of an effect
127:08 the converted wave. But we see huge effect in the converted wave which
127:14 us that the shear wave velocity has a lot in general. Therefore,
127:20 you had converted wave surface seismic, they didn't. But if you
127:25 we'd be able to see that And we could tell you this is
127:28 not gas, it's probably so. that was part of the point of
127:35 whole work. This is a post , but we can understand all the
127:43 . Great. OK. Let's take few minutes, Stephanie and then we'll
127:47 back and finish off. OK. see you in a little bit.
127:59 . Great. Great. Stephanie. Yeah, so we've, we've done
128:04 little sketch through of uh the zero DS P uh what it's good for
128:09 the interpretation. And then we started some pictures of um of using an
128:16 source and gave some hints at how would be uh constructed. So that
128:26 just our uh our reflection point, specular reflection point and how we do
128:31 mapping. I'm gonna just jump through in a slightly different order because we're
128:44 about imaging right now and we talked mapping that was just taking the reflection
129:02 and for all different layers and how can put back the trace on its
129:06 point. And the main, as can imagine, the main energy in
129:12 reflection is just from what's called the reflection point or the angle of incidence
129:16 angle of reflection. So that's where energy comes from. But as you
129:22 , it, it we can think the earth differently and we can think
129:27 each point in the earth can be of a scatter or or reflector.
129:33 we think of the plane angle of angle of reflection, that's where most
129:38 the energy comes. But it turns when the energy hits the interface,
129:44 we imagine he's principle is that it ra radiates everywhere. Most of
129:50 sums together at the specular or the distance point, but not all of
129:56 . So another way to look at and this is the migration view is
130:05 each point in the subsurface really re the energy. So in other
130:11 I can imagine that I have a from a disturbance, we know that
130:16 propagates out. But I can imagine every point here actually re radiates the
130:27 . So say we thought of the as kind of a fluid and I
130:36 tapioca everywhere in it. Then the would go on each tapioca or what's
130:44 Vietnamese drink called? That has is it Baba that has the
130:49 no. Yeah. The boba Yeah. So imagine that we've got
130:56 , a beautiful glass full of boba you have a wave started at the
131:04 . The energy goes down and it's reflect or scatter from each one of
131:08 little boba nodules. So we we kind of imagine. and this
131:17 the, this is the basis of migration or Kirkoff migration or any of
131:25 migrations or the slightly more sophisticated ways do imaging. We imagine that the
131:35 is going into the earth and every in the earth will reradiate that
131:46 OK. So how can we make picture? That's not just a
131:50 that's not just an angle of ray angle of reflection. But now
131:53 we think that there's a wave field down and that whole way field is
131:56 re radiated. And we don't know structure down here. It could be
132:02 , it could be a pod, could be a dip, it could
132:06 a fracture, it could be All I, all I know is
132:10 I've got energy going into the earth I'm gonna receive it and I'm gonna
132:15 to create anything that could have caused or reflection or diffraction or anything of
132:23 signals. So how do I do ? And the procedure is PRESTA
132:32 And conceptually this is how it We imagine that we've got energy going
132:42 the subsurface and this is in offset death. And this is schematic.
132:49 you can imagine that it takes a amount of time to go into the
132:54 . So in in this area, taken .8 seconds to get anywhere on
133:02 line. Now, we can also , in fact, we could use
133:07 same little codes. We could imagine if I had a receiver here from
133:18 can energy come to that receiver in certain amount of time? So anywhere
133:27 this line Energy can come from anywhere this line to the receiver in .7
133:39 . Or equivalently, we could kind think of if I took this receiver
133:44 imagined it as a source Energy from receiver goes out to here in .7
133:52 time. So we could imagine it either way but one way or the
134:08 , we imagine that we've had a here and I've got a receiver
134:34 you could it have come from. what do you think you froze for
134:46 a couple of seconds? So are you asking me what I
134:52 Yeah, I just gotta know here my internet is unstable or there's some
134:57 in the internet somewhere? OK. suppose this receiver, I recorded some
135:07 1.2 seconds after the shot. So the question is I know how
135:14 it takes for energy to go from shot to anywhere in the subsurface?
136:16 . Ask me what I think one time. Ok. So suppose,
136:31 we got At this receiver, I some energy at 1.2 seconds,
136:37 OK. We know how long it to get from every point in the
136:42 . We know how long it takes go from every point in the Earth
136:45 the receiver. So if my total time from the shot to a position
136:51 the receiver is 1.2 seconds, where that have come from the 0.6?
137:09 , so that's, that's one place that the only place is there only
137:14 place where the energy could have come ? Oh, well, no,
137:17 mean, it could come from Well, not anywhere. It,
137:23 took 1.2 seconds to get there. , could it be from every,
137:33 , From the receiver to the Like any of those lines?
137:38 the, the rule is going to that The total travel time from the
137:45 to the point from the point to receiver has to be 1.2 seconds.
137:51 any combination of shot to point From point to receiver that equals 1.2 is
137:59 be fine? OK, so pick couple points where that, where that
138:09 . So where are the shot to point Plus the point to the receiver
138:21 equal to 1.2. Where are some those points? Um, so Like
138:29 said, the .6 and back. where, where would that be
138:33 Exactly? Um, would, couldn't, it just be anywhere along
138:46 line Of that .6? OK. that takes .6, but it's got
138:53 be .6 from there to the Now that the 3.6 from there to
139:16 , well, then it would only , I know you're probably asking me
139:22 simple question. No, it's not simple but OK, there's the
139:32 Oh, so the the energy is out. So say the energy goes
139:43 .4. Well, it's .8 seconds this locus to the receiver. So
139:52 intersection point of .4 with .8. . Oh I see total energy that
140:00 sir. So in fact, anywhere this line, The total travel time
140:07 the energy sums up to be 1.2 . OK. So if all I've
140:14 in the real world, all I have or this little semi real
140:17 I've got a shot and I've got data that shows up an event that
140:21 up 1.2 seconds later. Where could have come from If this is all
140:27 got, I don't know, but proposed a velocity model here already,
140:35 ray trace through. So I know the travel times from this shot to
140:39 point and from every point to this . I know the travel times.
140:45 I've just got to overlay these two and see where they both sum up
140:50 1.2. OK. That makes a of sense. OK? Instantly if
140:56 understand this, you're, you're gonna PRESTA migration because this is how it
141:09 . So the construction process is, don't really know which of these points
141:16 is because all I know is when showed up. So as far as
141:20 concerned, it could have been 0.4 0.8, it could have been 0.5
141:24 0.7. It could have been 0.6 0.6 da da da. I don't
141:30 . And I'm just a poor processor at C G G trying to make
141:33 living for my two new kids. I've just gotta get this done and
141:37 some money and go home. And what I'm gonna do is put it
141:46 there. So I'm gonna take this and I'm gonna put it everywhere right
141:54 this whole locus along this whole So if you tell me, I
142:02 a shot, I had one shot I had one receiver and this is
142:06 I got then for that time, gonna put it everywhere there. And
142:13 is my picture. You gave me shot, you gave me one
142:18 I only saw one event on I put that event everywhere where,
142:22 it could have come from. And my picture for you. And that
142:31 a pres stacked migration. We it's PRESTA because I haven't stacked anything
142:36 yet. This is raw data. migration because I have migrated. I've
142:42 this amplitude all along here. And is my first picture. And in
142:51 , for only this data, that the best picture I can give to
143:16 . So, of course, what going to do is we have a
143:20 of different receivers that are gonna receive energy As well as we're going to
143:31 received energy at different times. So I received energy at say 1.0,
143:36 suppose I had a blip here, do the same thing. What's the
143:40 receiver combination that gives me 1.0, would have been say .3 Plus
143:50 So there is that point .4 Plus . So I'm gonna see that if
143:58 had an event at 1.0 seconds, could have come from anywhere in here
144:08 I'm gonna put it there. So all kinds of different data here,
144:18 are gonna go on ellipses, they're that. And then that's just that
144:24 receiver, I'm gonna have all these receivers. And so I'm gonna have
144:28 for all these receivers of putting their where it could have come from.
144:33 then I'm just gonna stack all that together and this is going to rely
144:42 things that are not possible where it not come from canceling out. And
144:47 how Kirkoff this PRESTA migration works. have to have enough receiver positions that
144:56 of these ellipses or possible places, stack them all together and where it
145:03 come from, they'll stack in phase they'll stack together constructively where they didn't
145:09 from, they'll cancel it. So is just brute mindlessness, but that's
145:17 you make a pre stack migration And that's for structural areas. That's
145:25 the, the V S P It's also why in areas of low
145:32 , we see these migration artifacts which the tails because if I don't have
145:37 data, then it doesn't stack out . And I'm just left with these
145:42 . But that's what my, my did. It just put data everywhere
145:46 because it was possible. And if don't have enough coverage to cancel it
145:51 , it's gonna still be left So we can potentially build a
146:04 And then just the way I've said trace through to see how long it
146:11 to get to every place, ray through to see how long it takes
146:15 every place to the receiver and then this data and plot it back and
146:22 it where it could have come So you can see that I've got
146:27 artifacts, these and that is what in migration. They've got these artifacts
146:35 I don't have enough coverage here to a picture. But from ray
146:46 I know that this is where most the fold would come from. So
146:50 gonna mute that picture, its low and just keep the picture. That's
146:57 highest F. Now I could do with a, With a threshold algorithm
147:01 said just look at all this If it's above say 10, keep
147:05 . If it's below 10, don't it. And that'll be an automatic
147:08 for me. And that would be way to mute. And we're gonna
147:16 making pictures like this. So here's BS P, we've got this migrated
147:25 from receivers that are down in the and that's gonna compare to surface seismic
147:34 you've got much poor resolution. So because we're grabbing this data right in
147:40 well, we've got high frequencies and can position it. And now I've
147:45 this nice high frequency picture from the , so that is the migrated image
148:06 we could do that repeatedly. I have make this picture. No one
148:14 another picture, make another picture, another picture and then look at the
148:20 between these pictures and then start to how have things changed. And that
148:26 be a time lapse image. So the concept of making the picture in
148:35 structural environment. And then the beauty DAS is that the sensors are always
148:41 the, well, we can make picture any time we want, we
148:44 have to put an interrogator box on and shoot some sources. So then
148:48 can look at the time lapse of and see what's happening with injection.
149:01 . Does that start to make a bit of sense of how we can
149:04 pictures? Yes, we're getting. . No, the, the other
149:19 thing to talk about is amplitude versus and then that throws a lot of
149:39 a lot of the, the the at us. This is all uh
150:01 be all there. I'm just jumping a little bit to uh to try
150:04 fit this into the next few So we've talked about making the
150:17 but uh we can also talk a bit because the amplitudes of the seismic
150:24 change with angle of incidence. And that is shown here. So we
150:33 imagine that we've got energy coming it bounces and I've got a certain
150:38 of incidence here. If I go here energy bounces and it's got a
150:43 angle of incidence. So you can that in the V S P
150:47 if we have multiple source offsets, have the opportunity to say something substantial
150:54 amplitude versus offset. But before we that, let's just go back a
151:02 bit and remember what we're talking So we're talking about a P wave
151:17 in to an interface hitting the interface it sets off four different waves.
151:29 there's just the standard angle of incidence angle of reflection, that's our normal
151:34 . But because there's a little bit sheer on the interface, it also
151:38 up a shear wave reflection. we get energy that transmits to the
151:46 . Most of the energy is in P wave transmission. But we also
151:51 a little bit of she wave And just for the records when we
152:05 all those constraints together, that's the set of equations that we get or
152:10 does energy partition across the interface as function of angled incident. So in
152:18 this guy, we can just say if I have a certain angle of
152:23 , that's here. And I say got the number, I've got an
152:28 of one coming in. What are amplitudes of all these outgoing guys?
152:32 if I've got one coming in the wave is some fraction of that wave
152:39 in some fraction transmission and we can these and it depends on the V
152:47 ratios. And of course, the of incidence. Now what people do
152:55 that this is a pain. That's lot of stuff. It's good for
152:59 , but it's hard for us to what's going on. So a lot
153:02 people tried to make this simpler and said that for P waves, for
153:10 , that reflectivity as a function of is just a fraction of P wave
153:16 change, the fraction of shear wave change or the fraction of density velocity
153:22 . So 20 years ago, everybody trying to come up with simplified forms
153:26 the Zots equations to help us understand . So the reflectivity as a function
153:37 angle really depends on the P wave change, the fraction the shear wave
153:46 change and the density change. So any of these changes across an interface
153:51 give rise to reflection. And the of the reply depends on what angle
154:00 started with. And what are the properties across the interface. So this
154:07 our P wave reflectivity coming off the as a function of the angle of
154:19 incident energy. Now, in very cases at zero offset, the shear
154:37 goes away and this becomes really The P wave reflection coalition at zero
154:43 are normal incidents. As we it's just the, the change in
154:48 , the change in P and the in density At 30°. If the P
154:59 hits the interface at 30°, it's more . The change in the den uh
155:05 P wave velocity has an effect. change in the shear wave velocity has
155:08 effect on the amplitude and the change the density has an effect too.
155:17 the the thing here is that the amplitude is changing depending on how,
155:26 the angle of incidence hollow it um what direction at what tilt, we
155:34 our wave hits the interface. Now a good piece of code and this
155:41 uh you can just log on to cruise website at, at University of
155:52 . And there are and we can dial in changes of the elastic properties
156:00 the interface. And what kind of coefficient does that give rise do
156:09 for example, we imagine that there's an upper layer and a lower label
156:14 separated by an interface. And if give the upper layer a density and
156:21 , the lower layer densities and then we can calculate the reflection coefficients
156:27 a function of the incidence angle. just as an example case here,
156:38 we've got a fairly substantial Change across interface 2-2.2, the p wave velocity
156:47 increasing by 30%. What does that ? Well, Our total reflection coefficient
156:55 .2 in the P wave. And when we get to the critical
156:59 it goes crazy. There's also some wave we've got shear wave reflection as
157:08 function of angle. So this is we can use this converted wave and
157:13 we get ad o in the P , the P wave is changing amplitude
157:17 reflection because some of the energy is into a shear wave conversion. So
157:25 can use modeling packages because we can't the Zor equations on our head very
157:33 . So that's that's a B Now what do people do with A
157:39 O? Yes, they're gonna try take this little change across here and
157:46 that little change infer the velocity So once again, we're gonna try
157:52 take an amplitude seismic reflection and infer that means in terms of velocity difference
157:59 in the velocity difference, we're gonna to infer what that says about the
158:20 . So the first thing that we try to do is take real logs
158:25 . And now using the Zots I'm gonna model how the seismic data
158:31 change as a function of offset. can see when we hit the critical
158:35 , it all goes crazy. And typically in seismic, if you've got
158:41 , very wide offset and shallow then the phase and the character of
158:47 wave all changes and goes wonky. normally we just mute all that
158:52 It's too complicated. I'm a simple . It's Saturday, just mute
158:55 I wanna go home and we're just mute all that stuff. OK?
159:02 already at home. So I have stay, stay working. So,
159:08 you can see that there are little in the amplitude. So we're gonna
159:11 that and then try to process the change and figure out something about
159:16 You can see it's a formidable B because this is the real Earth more
159:21 less with the logs. We get very low resolution. Look at that
159:25 seismic, it's better than nothing, there are limits to what we can
159:30 . So I can look at the wave reflectivity and the converted wave reflectivity
159:34 try to extract some amplitude versus This is zero offset to 2000 m
159:42 source receiver on the surface. And that variation, I can try to
159:47 something about the real rock properties. I could say something from that A
160:02 O, if I can interpret that a P wave velocity drop and the
160:07 wave change and a density change, I can extract that from A B
160:13 that I know, for example, gas should have drops in both those
160:19 I can get my A B O look at where we get big drops
160:25 then map that and say that's a indicator as extracted from A B
160:32 So that's why we want to do . Now in the V S P
160:40 , I can calibrate all of So I can take receivers down
160:44 I can walk away a source and directly, get A V O.
160:54 when I process the BS P from different shot, so I got different
160:59 offsets here with receivers at depth. I can see that when I process
161:09 V S P with all these different offsets for these depths, I see
161:13 little bit of change in the converted , I see a little bit of
161:17 . So it turns out there's a porous layer in here and I can
161:22 it going from very small amplitude to amplitude in the P wave V S
161:27 . Likewise with a converted wave, put that all together with my other
161:37 S P and I can invert this make an estimate of the rock and
161:43 porosity and the poor film. And that's what we're gonna, that's what
161:47 do with the, with the BS . OK. So that's a big
161:59 through um all of this. So again, just to summarize what we've
162:08 doing, I'm just gonna jump down and we've got a little exercise for
162:50 . So this is from some data Algeria where we were working a few
162:54 back. So, so practice, the dominant frequency? We've, here's
163:04 V S P in death here. the time. So, you
163:09 and love this. So please compute uh the dominant period and then the
163:17 frequency here And then looking for 2100 say 3000. What's the interval velocity
163:29 ? Then with some log analysis, look down here and we've got an
163:36 a right here. What kind of is that in this interval? Then
163:49 got an interface right here and I've the V S P image into surface
164:03 . So here's the V S P and the surface seismic. The surface
164:07 is pretty ratty, but the horizons been identified on the surface size.
164:23 which one of those corresponds to So here are some horizons identified in
164:30 surfaces. The V S P is into the surface and this B
164:40 which one of those is it? again, that's just a little exercise
164:57 . Yeah. Sorry for B is the quirk side Hamra? Uh It
165:08 be, that's your exercise. this is like a homework for me
165:12 send you. Yeah. Ok. thought we were doing it right
165:15 Thank goodness. Ok. Well, we can do it right now if
165:19 want to. It shouldn't take you long. It's kind of nice for
165:28 to, to take a bit of on it though so that you've got
165:31 . Yeah. No, I, can, I'll do it tonight.
165:34 . It's just gonna, this should take you five or 10 minutes to
165:38 . Ok. So, it's good sketch it out, just, just
165:41 do it. And then, and then you've got a, you've
165:44 a record of a, another little . I'll do better on this
165:51 I'm sure you will if you you get some time and,
165:56 nice to look at it. Have good look at the logs. These
165:58 real logs. This was a real . They, uh, we were
166:02 on it there. So it's, an interesting case. Ok. Get
166:10 some more again. With the, these actual log values we've hammered in
166:15 quite a bit. So, you , get your interpretation of how you
166:20 the logs are, make sure that understand, uh you know what we're
166:25 in this offset V S P and , uh the synthetics and the other
166:29 S P and then here's the surface and the V S P have been
166:34 in on top of the surface And the well is right here.
166:47 . Yeah. OK. Oh Great . Um we've worked our way through
166:54 physics, uh log analysis. We've a quick um rob through V S
167:07 and so do this little exercise and questions you've got, let me
167:12 And then uh next Friday, we'll up with a little bit of review
167:16 the V S P and the um bit about micro seismic, a bit
167:22 it crosswell some other geometries and then we integrate some of this stuff into
167:28 seismic. So we'll, we'll take of the um the other cases that
167:35 become important and people use this and branch out. I just saw that
167:42 seismic ink incidentally is hiring. So sent out a note on linkedin.
167:48 might have seen that micro seismic Inc Peter Duncan's company, former S C
167:55 president and they do micro seismic monitoring hydraulic tracks. But I just saw
168:01 he started a new company that I is called Micro the and it's for
168:06 geothermal mapping too and they set out note on linkedin that they're hiring and
168:16 least several of our students have been there too. So he's, as
168:20 as I know he's taking two or of my former students, master
168:27 So you might have a, since I actually had a phone interview
168:32 a recruiter for S L B. . So they asked me to send
168:38 like, my actual, like, and stuff like that and hopefully
168:41 they'll reach back out to me, I actually got to talk to
168:44 So that was cool. Well, great. Well, and you know
168:47 , especially with slumber Jay. they're gonna ask you a lot about
168:54 and V S P probably they've got , of course, but it might
168:58 for the seismic. But if it's anything to do there as, you
169:00 , their history, they were the . They started it all.
169:06 So, um, somebody was just me about, uh, interviewing for
169:14 company and there was a full on that they wrote to even get in
169:19 door. So that, that was . I've had to take a
169:24 there's been a couple that I've applied on indeed that you have to take
169:27 an Excel quiz. Like, there's bunch of different things that you have
169:30 prove you can do in Excel. . Oh, well, it's
169:36 As I, um, as I , it just depends what the,
169:40 , what the entrance is. They've to get this kind of scan and
169:44 somehow. So, um, you know what might happen. As I
169:50 before. One of, one of students went in and they said,
169:53 you know anything about logs and And he said, well a little
169:58 and they slapped down a whole set logs and said, well, interpret
170:02 and give me a plate that, was his interview. And he
170:07 fortunately, I was familiar with the logs and basic seismic and he said
170:11 was able to at least tell a and he got the job. So
170:14 was nice. Ok, good. . Well, great. Um,
170:22 just do this little exercise and then , um, anything, any questions
170:27 in touch through the week and then see you Friday. Maybe we
170:31 maybe we should go in person next . I don't know the,
170:34 what? Because I think Friday is last class, isn't it? It
170:43 . Yeah. Ok. And are we gonna go in on for
170:48 exam on that Wednesday? Um, know, maybe that's, Um,
170:58 think it's like 6-9 or something. , I think it's actually better.
171:06 the uh, yeah, maybe, it's just, um, I may
171:15 out of town so that might be Utah arrangement too. Well, I've
171:21 everything I all the other professors. just been doing it online. They'll
171:25 send it to me the day before I send it by end of
171:28 the next day or however whatever I don't care. Ok.
171:33 we'll, That might be the, the easiest way to do it.
171:36 we'll just, um, have you it, say 6-9 or something on
171:40 Wednesday? I think I spoke to about that. I, I
171:44 uh, they, I guess they to have a certain time,
171:51 period when you can do it. , but I, I did
171:54 I did hear. Yeah. So most people just sent you a
171:57 a full exam and then you just a day to write it or something
172:02 because I work during the day. they'll just before and, yeah.
172:07 . Uh, ok. Well, , we'll figure something out. So
172:09 got 22 other sessions. There's next afternoon and then the exam shortly
172:18 So, uh, well, Google I'm talking to it. It just
172:22 on. Ah, it's listening, , Google, turn it off.
172:32 , ok. Well, we'll figure out. Stephanie. So,
172:34 your preference is probably to, to do this. Continued being
172:40 Yeah. I just don't like being campus that late. Yeah.
172:45 you're probably right. But I if I just, because,
172:49 I'm by myself and it's just me the class. Um, but I
172:54 , like I said, like I'm open to whatever. Just,
172:56 don't, I don't like being there myself that late. Just, you
173:00 , that's, I, I agree that. That's, that's sensible.
173:03 . Well, well, that's good me to know too. Um,
173:09 we'll, uh, we'll make arrangements are all comfortable and stuff one way
173:13 the other. Ok. So we'll, uh, we'll organize
173:17 uh, uh, early next Ok. No problem. Ok.
173:21 . Enjoy the rest of the evening we'll chat early next week.
173:25 Thank you so much. So, person Friday, uh, I guess
173:34 because it's earlier. So we, finish about 4 30. Yeah,
173:38 fine. I just, the Wednesday to 9 I one kind of.
173:42 . Well, why don't we do then? Um, we'll, we'll
173:45 in person on Friday and then we'll the, uh, the, the
173:48 to 9, the, uh, stuff you'll do at home.
173:55 All right. Great stuff. All . See you then. See
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