| 00:01 | Um yesterday, we were looking some at getting down into the earth and |
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| 00:14 | was just gonna try to clean my up here and here's a colleague, |
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| 00:19 | Campbell, some of his uh some his thoughts Allen worked for slummer for |
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| 00:24 | years. I got to know him long time ago and quite a |
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| 00:28 | He's still, he has his own company now V S P consultants and |
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| 00:33 | the E A G E s courses um borehole seismic. But um once |
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| 00:41 | , what's, here's some of the that he puts down as V S |
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| 00:47 | advantage. I'm happy to say that look surprisingly similar to mine probably for |
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| 00:52 | reason. But the uh so that's good. What's the game uh for |
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| 00:57 | rock properties? Figuring out how waves in the earth? And we talk |
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| 01:02 | why waves, why that's important because of our exploration is done the |
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| 01:07 | So we need to know everything about . And then of course, interpreting |
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| 01:12 | seismic, we need to put everything so we can help with that and |
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| 01:17 | finally making the picture because ultimately, really what we provide in general is |
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| 01:23 | here or perforate here or this is where something's happening here. So we |
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| 01:30 | to try and help with the So here's what uh what Alan |
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| 01:35 | has mentioned. And uh for me , the first aspect of designing. |
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| 01:44 | when we think of all of all geophysical uh techniques, we're always |
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| 01:51 | but number one, what's the Of course, how big is |
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| 01:53 | where do we think it, it be? So all those factors. |
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| 01:57 | just the geometry of the target that interested in. And then uh of |
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| 02:02 | , as a geophysicist, my opinion how do you design your survey? |
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| 02:06 | it's just to get as much data possible for, for the amount of |
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| 02:11 | that you can uh imagine. So want to just gather everything we |
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| 02:18 | So that's, that's our idea. Now we have to uh we have |
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| 02:27 | try to gather as big and a of areas of coverage as possible. |
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| 02:34 | like we've said, almost always, will be uh the well is |
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| 02:37 | So we're in that world already. the wells drilled, there's probably |
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| 02:42 | there will definitely be well logs, will be geologic tops, there will |
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| 02:46 | all of that idea. So our job to me is really to provide |
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| 02:51 | a seismic well log. And that that we want a, a fairly |
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| 02:56 | offset one dimensional type of survey. often in design first of all, |
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| 03:02 | sure you get the easy stuff and goes back to the, um, |
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| 03:09 | know, one of, one of students came in and he was kind |
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| 03:12 | looking at where to go with his . And there's, um, there's |
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| 03:18 | analogy that helps me that we're gonna about a little bit today. It's |
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| 03:21 | billiards or pool. And the, older game is that they're a bunch |
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| 03:25 | red balls. I don't know. you ever played billiards or pool? |
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| 03:30 | ? Yes. Ok. Uh, student wasn't, he was familiar with |
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| 03:35 | spots and stripes game, but we to play a game that had, |
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| 03:39 | , red balls and then colored the yellow green, brown, |
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| 03:46 | pink and black ball. Have you played that game with the red? |
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| 03:51 | a little bit like chess. I've heard of it. Um, |
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| 03:56 | never played it myself though. Well, the game is that you |
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| 04:02 | to sink a red ball first. there are a lot of red balls |
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| 04:05 | they're, uh, you have to one first and then, and then |
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| 04:09 | get to sink a colored ball So the red balls are worth two |
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| 04:13 | . They're cheap and then the colored are more, uh, give you |
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| 04:16 | points, but you're always thinking about the colored ball, but you have |
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| 04:20 | sink the red ball first. So been a guiding principle in my |
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| 04:24 | It's always to, uh, you to sink the red ball first. |
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| 04:28 | have to do the cheap hard stuff and then you get to the |
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| 04:31 | expensive, good stuff. So, a sense with these survey designs, |
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| 04:37 | really want to get the simple make sure we nail the simple stuff |
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| 04:41 | that um so that we can get the more expensive stuff. I remember |
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| 04:46 | first job uh full time working for . We were actually going out to |
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| 04:51 | a BS P survey and I I was assigned the survey and so |
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| 04:56 | made a couple of uh errors. first error is I went into my |
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| 05:03 | and I said, I can guarantee that we'll get this, this, |
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| 05:06 | , this, I was full of vinegar and all kinds of other |
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| 05:10 | And he said, ok, first is never guarantee me anything ever. |
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| 05:16 | said, excuse me, he said a lot that can go wrong and |
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| 05:20 | don't want to sully your reputation. never guarantee me anything. Oh, |
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| 05:27 | . I'll try, I'll try worse time. So that was one |
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| 05:31 | Um So we're gonna get this, gonna do our zero offset E S |
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| 05:36 | to make it look like a That's great. Then we're going to |
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| 05:42 | much as budgets and space and everything allow get offset sources because we're trying |
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| 05:47 | create a, an offset picture or volume or say more about wave propagation |
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| 05:51 | properties. So we'll try to step our sources. And then the uh |
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| 05:59 | there's lots of good news about the S P but the bad news is |
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| 06:03 | uh generally speaking on the surface, we've got a shot and a |
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| 06:12 | as you know, the mid point the imaging point more or less. |
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| 06:18 | if I've got the V S P shot in a receiver, then the |
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| 06:22 | point is not the midpoint because it's . So the, the reflection point |
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| 06:27 | toward the receiver. And so we with a given offset, we, |
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| 06:33 | don't get coverage out to half the , we just get out to a |
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| 06:37 | . So we don't see quite as away as we would with surface. |
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| 06:44 | that's, that's some of our Um We can get pretty complicated pretty |
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| 06:53 | . And here Allen is showing some his sort of high end real world |
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| 07:04 | design. You've got the uh you've the surface, we've got our, |
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| 07:08 | borehole, uh we can have shots over and then typically you're gonna ray |
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| 07:15 | from uh a surface, you think the V S P and he's got |
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| 07:20 | the coverage shown here. So you see very uh had a very blotchy |
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| 07:30 | and fold is, is the number points that we imagine bouncing off a |
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| 07:36 | uh area or B A bin is uh a sub, just a subsurface |
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| 07:44 | or a surface area. So this is jumping into kind of the |
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| 07:54 | the higher level professional design. We're , we're gonna design things a lot |
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| 08:00 | simply because in the field all of sudden somebody's gonna say, hey, |
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| 08:02 | at, we just got told by farmer that he changed his mind and |
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| 08:06 | can't go on his property. Um are you gonna do now? |
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| 08:10 | well, I'm gonna go back and a 3d finite different algorithm. |
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| 08:14 | you're not. I need to know now. So we have to have |
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| 08:18 | rules of thumb. So, but is ideally what we would do. |
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| 08:24 | We would guess the surface often we know it, but if we had |
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| 08:27 | , we would guess it and then would re trace from a surface shot |
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| 08:31 | to that back and just see where coverage is. But we could, |
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| 08:36 | points that we could hope to So that's the high end where we |
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| 08:44 | like to go. Um In terms , of shooting often we'll just, |
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| 08:52 | there's a, well, the wells the middle here um or here often |
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| 08:57 | just gonna get one shot. So gonna get a zero offset V S |
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| 09:01 | one of these shots or we might a few shots or we might piggyback |
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| 09:09 | a 3d seismic survey and get a of shot points. These are aerial |
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| 09:12 | just the surface or we might be the North Sea and there's a, |
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| 09:18 | , and we've got a boat and gonna do these walk arounds and just |
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| 09:24 | in a circular survey. Um, was on the survey in the |
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| 09:30 | I were really happy that I was on the survey on the left in |
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| 09:35 | North Sea going around in circles on boat, but they didn't. And |
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| 09:44 | if we look at the kind of we would get. So I suppose |
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| 09:47 | had a surface, an orthogonal type line coverage and the rays are gonna |
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| 09:52 | down, they're gonna bounce. And we look at the coverage subsurface from |
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| 09:57 | surface shots, we're gonna get something this tent or pagoda or bell shaped |
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| 10:06 | . Uh Likewise, if we had , a deviated or horizontal, |
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| 10:09 | and we were shooting above it, would get coverage sort of like in |
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| 10:14 | trumpet or corn shaped area. Then , in the more complicated world, |
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| 10:24 | can try to design for different kind sensors. We looked at the |
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| 10:28 | we could have dynamite, we can vibes in the surface. We have |
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| 10:30 | guns in the marine case that's on source side, we'll use whatever we've |
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| 10:37 | whatever is the best source where, we can get, look at the |
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| 10:41 | . But then we also wanted to at the down hall and we saw |
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| 10:46 | we could have strings of geophones or of accelerometers or cemented in chip |
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| 10:55 | But the exciting thing in the last years has really been fiber optics. |
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| 10:59 | so the idea is to have a optic cable in the well, and |
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| 11:08 | example, here's what we were asked design. This is with Apache in |
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| 11:15 | Texas. So they said, you've got vibes, we're gonna shoot |
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| 11:27 | vibe points. So that's pretty Not just one, they're gonna shoot |
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| 11:32 | . The target was at 10,000 West Texas um shale. The horizontal |
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| 11:41 | is gonna go 5500 ft horizontally and gonna put fiber outside the well casing |
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| 11:51 | cemented and then they want fairly high . So each output image point, |
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| 12:01 | output pixel should have at least 100 . So those are the kind of |
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| 12:06 | they gave us and this is hard see but wonder if I can make |
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| 12:13 | a little bit better. Oops, me see if I can lighten that |
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| 12:23 | a little bit. Uh You see that's, that's a little bit. |
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| 13:04 | . OK. That's a little bit . But they had, in this |
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| 13:07 | case, they had uh a, pad with a bunch of horizontal |
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| 13:11 | And as you can see in the right, this is more to scale |
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| 13:17 | um we go down, they start bend or kick off the, |
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| 13:24 | this is the heel of the horizontal , and then they drill horizontally. |
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| 13:31 | this is a kind of image in mind for these horizontal wells and they're |
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| 13:36 | gonna drill a bunch of them because have to hydraulically fracture um and try |
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| 13:43 | clean up as much of or extract much oil as possible. So you've |
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| 13:48 | this complicated. Well, and then did ray tracing. So this is |
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| 13:56 | circus picture again. And here's well on the top looking down plan |
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| 14:06 | . And so we advocated putting a of uh Lines of shots. So |
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| 14:11 | is how we're gonna try to distribute the 800 shot points they gave us |
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| 14:20 | the rays just go down and bounce hit the V S P string. |
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| 14:25 | then we imagine that the subsurface is into square bins in this case, |
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| 14:35 | ft by 55 ft, which is standard 110 ft. These are kind |
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| 14:39 | standard imperial units and then we just how many bounces given these shots, |
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| 14:45 | our um our V S P vertical , how many shots would bounce in |
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| 14:53 | bin. And then we'll try to to get lots of uh fold in |
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| 15:02 | area of interest. So you can the way down here, the wells |
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| 15:06 | up in the the top, these shots. Yeah, we don't get |
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| 15:15 | until we get halfway between the shot the receiver and then we start getting |
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| 15:20 | bounce. So once again, this when I've got a shot here and |
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| 15:25 | receiver here and a surface receiver then got receivers all the way down and |
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| 15:31 | looking at the bounces that go into one of those receivers in plan |
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| 15:36 | So this is a full map that use in surface seismic or in uh |
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| 15:43 | BS P. So here's more of I'm talking about that. We've got |
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| 15:50 | , a shot, we've got a far off. That shot energy is |
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| 16:09 | down, it's bouncing off our, imagined our target layer and then bouncing |
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| 16:14 | up into all the well receivers. once again, the, we imagine |
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| 16:35 | we've got receivers all the way down well Spaced at 50 ft or |
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| 16:43 | whatever the equipment provider could give So we've got receivers all the way |
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| 16:47 | the well, then I'm going to one shot. I've got a |
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| 16:57 | the energy is going out, it off our layer of interest. And |
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| 17:03 | each receiver, I've got a it bounces, bounces, bounces, |
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| 17:08 | . You can see that I have be uh within half the source offset |
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| 17:15 | get a bounce. I don't get balances out here. So I start |
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| 17:18 | get balances here. That's for one . And we imagine that again, |
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| 17:33 | divide up this surface into bins or intervals because I've got to give uh |
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| 17:47 | map the position of the bin and many of these rays bounce inside that |
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| 18:01 | . And so I just, first all, I, I want to |
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| 18:05 | where the rays are bouncing because that's be my coverage area. That's the |
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| 18:09 | that I could hope to make a out of. And then I'm gonna |
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| 18:22 | this ray tracing exercise for every shot an offset as all over the |
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| 18:33 | And then I'm gonna sum together all those, just count the number of |
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| 18:37 | the array bounces in each bin. then that's my ultimate fold. That's |
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| 18:44 | , the plan view map of this of interest, the surface of interest |
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| 18:49 | how many rays are gonna bounce in part of that. And that's gonna |
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| 18:53 | me whether I've got any hope to it. Have I covered it |
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| 18:55 | Have I put enough um bounce points it to be able to hopefully make |
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| 19:01 | picture of that. So that's the idea with it, with either surface |
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| 19:07 | . This is exactly what's done with seismic design. You'd put every shot |
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| 19:11 | every receiver look at all the bounce , then how many shots and receivers |
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| 19:15 | how do I, how do I them together? And similarly with V |
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| 19:19 | P. So this is the Now, the design is really generally |
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| 19:25 | on the reflections because that's how we the picture. But we're also alert |
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| 19:31 | the direct downgoing waves because this is different part about the DS P because |
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| 19:39 | got receivers in the, well down , we get the chance to measure |
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| 19:47 | waves going directly into the earth course seismic because I've just got receivers up |
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| 19:52 | . All I get are reflections and little bit of direct rival and |
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| 19:57 | But I don't get this beautiful whole of downgoing waves. So that's really |
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| 20:04 | in the V S P. So example, in this uh this Apache |
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| 20:10 | , we just advised them the numbers matter. This is just the process |
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| 20:15 | was going through. So we used , a shot line area. Uh |
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| 20:21 | trying to keep the fold high And we found that you don't have |
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| 20:29 | have the shots really close together in lines, spread them out, increase |
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| 20:33 | shot lines and uh keep the lines . And that gives you the |
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| 20:39 | So that, that's just the kind process that we would go through |
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| 20:44 | to design the survey. Now, a fairly complicated survey. Generally |
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| 20:50 | you don't have surveys that complicated they say look at, you've got |
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| 20:56 | you can go in and, and one survey, one shot. That's |
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| 21:00 | . Oh, OK. So here's kind of data that we would get |
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| 21:08 | just a single shot. So in case, there's a source that's pretty |
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| 21:17 | to the well head 100 ft we're gonna call it zero offset because |
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| 21:26 | m is pretty close to the, , when I'm walking down 1100 |
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| 21:33 | that's if we look at the that's just a little offset compared to |
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| 21:37 | . Well, plus all of the is going to assume one dimensions. |
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| 21:42 | so we'll call this zero offset. here's basically what we're gonna do with |
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| 21:48 | . So if I just had this shot gather, which isn't too |
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| 21:51 | And you can see we went from from 225 to 1500, over 1500 |
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| 21:59 | took a shot, arrival, arrival, arrival. So we're going |
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| 22:06 | , it takes longer to get Uh They there might have been |
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| 22:12 | multiple casings uh out of budget because this day, this day is gonna |
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| 22:18 | shot from the bottom up. Like of our logs, we log from |
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| 22:21 | bottom of the well up. And , the reason for that is that |
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| 22:26 | there might not be adequate tension on wire line as we go down, |
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| 22:31 | equipment might fail. So we'll take test shots on the way down. |
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| 22:35 | ultimately, for uniformity, we're gonna and do everything up because now my |
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| 22:43 | line is calibrated. I know I get to the bottom of the well |
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| 22:48 | we want to keep all the equipment tension uh while we're pulling it |
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| 22:55 | So we want to generally get a of things out of this. Uh |
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| 23:01 | mentioned before that the first thing we to get is a seismic log. |
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| 23:10 | really, really fundamentally, I want know that the time it takes for |
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| 23:14 | wave to go into the earth. , for example, how long does |
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| 23:24 | take the wave to the wave just propagate to Say 700 m? Can |
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| 23:35 | pick that Stephanie? Um, it'd a little Like a little less than |
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| 23:46 | milliseconds. Yeah. So probably 2 . Mhm. So, if that's |
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| 23:55 | long the way it takes to get 700 m, what's the average velocity |
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| 24:01 | the surface to 700 m? Wouldn't Just be about 250? Yeah, |
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| 24:17 | takes a quarter of a second oh of a second, A quarter of |
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| 24:21 | second to go 700 m. So a full second, it's gonna take |
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| 24:29 | gonna go at 2800 m. So divided by .25 seconds, it's just |
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| 24:39 | times one over a quarter, which 700 times 4 2800 m per |
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| 24:45 | So in this area, it takes quarter of a second or 250 milliseconds |
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| 24:53 | get 700 m. So average velocity just 2800 m per second. So |
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| 24:58 | first looked at that and I did I screw up a deba |
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| 25:01 | Should it be 28,000 m/s? no rocks go that fast. Should |
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| 25:10 | be 280 m/s? No, we that the velocity of P wave velocity |
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| 25:17 | air is already 300 m per So the velocity in rock is certainly |
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| 25:23 | lot more. So. No, didn't screw up. It's 2800 |
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| 25:32 | But let's do the same thing. down to 1500 among friends. So |
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| 25:37 | energy is going into the earth one , write that down and it reaches |
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| 25:40 | bottom at 1551. So what's the velocity to the bottom of the? |
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| 25:47 | , here, just approximately, Let's say that's about like 4.10. |
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| 26:04 | , yeah, um about 3 78 . Well, here's the bottom. |
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| 26:28 | on, let me move us. , so you've got the energy coming |
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| 26:39 | into the earth. There's the bottom 1551 m. Mhm How long did |
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| 26:50 | take to get there? And that's right at that line. So let's |
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| 26:56 | that line. Oh, just take line. So that's 500. |
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| 27:00 | So what's the velocity to the the velocity to the bottom of the, |
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| 27:04 | , at 1551, just more or . Um About what is it like |
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| 27:12 | by 500? So that's three So the 3000, Right? What |
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| 27:22 | you just divided by 51 x Yeah, That's 3.1. That's |
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| 27:30 | 3.1 watt that's milliseconds And then that and thousands, that's 31:02. What |
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| 27:40 | ? 02. What? Meters per ? Perfect. You got it. |
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| 27:48 | yeah, this, so just in this is half a second. It |
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| 27:53 | 0.5. Which is amazing. You , this is going down a mile |
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| 28:03 | it takes 0.5 to go a So that's pretty fast. So, |
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| 28:10 | it goes 1500 m in half a , it goes 3000 m in a |
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| 28:14 | . So, um, Pretty And then once again, we look |
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| 28:19 | that now, we're fairly deep. around 5000 ft. We're at 1500 |
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| 28:24 | . So, 3000 m/s, is , is that in the game |
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| 28:28 | For rocks? Well, you said yesterday, the sandstones are what? |
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| 28:36 | 2200? Yeah, unconsolidated. So this would be something that's more. |
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| 28:46 | . Yeah. So it's in the 3000 m per second. I'd I'd |
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| 28:49 | that as some kind of consolidated sand or a shale and it's not too |
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| 28:58 | and it turns out that we're um this particular area, we're just about |
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| 29:03 | hit the carbonates, but we haven't the carbonates yet. So this is |
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| 29:07 | of a consolidated plastic sequence. So m/s is, is in the game |
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| 29:14 | that good. So that's where uh energy is going down into the |
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| 29:22 | And then, and you, you see that it's got this positive |
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| 29:26 | you go deeper, it takes I work more hours. I get |
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| 29:31 | more. Usually. Now this we see this other energy though that, |
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| 29:43 | has the opposite slope. And this is the energy going down into |
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| 29:49 | earth hitting an interface and then bouncing . So these are our reflections coming |
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| 29:57 | here, then the other, some the other character um We imagine that |
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| 30:20 | here, if we had recorded all way to the surface, we'd have |
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| 30:23 | energy coming down, it's hitting, bouncing. So this slope, what |
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| 30:30 | this slope indicate? Um Isn't this like the travel time? Yeah, |
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| 30:52 | if I go across some depth and takes, it takes a certain amount |
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| 31:04 | time, it's really weird. This is actually offset from where it's |
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| 31:20 | So we can uh as I come some the energies going into the |
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| 31:30 | this is a certain depth, taking certain time. And we said that |
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| 31:35 | course, depth over time is OK. Now, the, the |
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| 31:45 | thing to imagine here is that we've two, two concepts. We've got |
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| 31:53 | , the data here that of it's taking longer for energy to get |
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| 31:58 | as we propagate deeper. But the geometry is just a shot on the |
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| 32:04 | . So we've got one dimensional the the energy is going into the |
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| 32:08 | bouncing back up. So we see expanded in depth and time. But |
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| 32:16 | the geometry and the surfaces, I've got receivers going down into the |
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| 32:21 | So we've got the geometry in Z X X is at one point. |
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| 32:28 | Z is increasing, but I'm plotting out is actual data and the data |
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| 32:35 | evolving in time. So you have keep that concept in mind. This |
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| 32:46 | panel is really, really simple. just I've got all my receivers in |
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| 32:51 | . I whack the surface and this what the receivers in depth record. |
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| 32:55 | again, the first energy going down the earth and then reflections. But |
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| 33:00 | slope here is the depth over the , that's the slope. So I've |
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| 33:07 | Z over T so the slope is the velocity. Now you can kind |
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| 33:24 | see here, Is there one slope ? Is it uniform not really look |
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| 33:35 | it, you know, it's, increasing, it has to increase. |
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| 33:39 | we know that but there's some kinks it, we can see some obvious |
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| 33:45 | kinks. And so up here, it takes, it's taking longer to |
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| 33:52 | a certain depth. So is this higher than this velocity or vice |
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| 34:01 | There are different slopes here that are different velocities. Yeah, the steeper |
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| 34:08 | would be quicker. Which ones? first one? OK. Now pick |
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| 34:18 | way through that. Oh Wait, , because it's deeper. So it's |
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| 34:35 | technically. So, no. So the steeper would be slower. |
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| 34:42 | right because it's taking longer to go certain intervals. So the uh the |
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| 34:48 | thing we noticed that these steep slopes this plot when I've got depth increasing |
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| 34:55 | time increasing this way. Uh This means that depths increasing, but time |
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| 35:02 | increasing the slope is a lot So for a given depth, it's |
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| 35:06 | longer to do it. So it's when this is shallow. Well, |
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| 35:10 | can imagine if it was flat, would mean that it's going across at |
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| 35:14 | depth with no time which we can't . But the flatter we get the |
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| 35:20 | it is. So just some mental , what we're trying to do with |
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| 35:26 | is to get you to look at and now start to be able to |
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| 35:28 | the patterns in this and know what patterns mean. So uh steep slope |
|
| 35:36 | gets fast. Then in here what , starts to slow down again, |
|
| 35:43 | a little bit slower. We're but it's getting slower. So there's |
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| 35:50 | layer in there and then it gets little bit more shallow, so it's |
|
| 35:56 | little bit faster. No. So immediately gives us a velocity log. |
|
| 36:11 | can just take the slopes and plot slopes versus depth and that's our velocity |
|
| 36:16 | depth. So the very first thing just the time to a certain |
|
| 36:23 | So that's why we did that first exercise. How long does it take |
|
| 36:27 | energy to go down to 1500 Well, .46 seconds. Ok. |
|
| 36:36 | if I went to surface seismic, would know that it, from my |
|
| 36:39 | P, I've seen that it takes seconds to go to that layer of |
|
| 36:44 | . It's gonna take 0.46 seconds to back. So on surface seismic with |
|
| 36:49 | way time, I know that that at two times .46 comes from 1500 |
|
| 36:57 | . So when I look at Circus and I go to .9 or a |
|
| 37:04 | , I know that that's coming from 1500 m deep. So I immediately |
|
| 37:10 | my time to depth map and I stretch the surface seismic from the echo |
|
| 37:18 | to depth. So that's what you to use this time to depth map |
|
| 37:26 | . Then um I've also I can just from the slopes, the interval |
|
| 37:32 | , the velocities across these intervals. that's gonna give me again uh like |
|
| 37:37 | sonic log, it's gonna give me velocity in depth which I can use |
|
| 37:44 | rock type, gross porosity, uh processing a lot of stuff. |
|
| 37:53 | we also said that velocity um usually with density and vice versa. Density |
|
| 38:06 | with velocity. And we said that times velocity gives us impedance and a |
|
| 38:16 | in impedance going from above to below me a reflection coefficient and a reflection |
|
| 38:25 | gives rise to an echo or a . So given that logic, |
|
| 38:42 | what did it change in the slope here change in velocity change in |
|
| 38:48 | So if I've got a change in , what do I expect to happen |
|
| 38:52 | density to change? Also change in ? So if I've got a change |
|
| 38:58 | velocity and density. What do I with the impedance? Were there to |
|
| 39:05 | a change? Yeah, multiply the of them. So there should be |
|
| 39:08 | change in impedance. If I've got impedance change, do I expect to |
|
| 39:14 | a reflection? Yes, absolutely. it. So if I'm at a |
|
| 39:24 | where there's a change in velocity, is I'm gonna define as an |
|
| 39:28 | what also should I expect a reflection ? Yeah, you got it. |
|
| 39:34 | so what do I see here? points. Yeah. Wow. Seismic |
|
| 39:40 | . It's not all garbage. So can actually see effectively the waves coming |
|
| 39:48 | into the earth. It hits a change. That's probably gonna be a |
|
| 39:53 | change that's gonna give rise to an change which is gonna give rise to |
|
| 39:58 | . And at all these points where velocity changes, here's a really obvious |
|
| 40:03 | , there's a knee or a an in the velocity and boom, we |
|
| 40:10 | see a reflection coming off it. are all kinds of little changes down |
|
| 40:15 | . You can see we're going from slow velocity to a higher velocity. |
|
| 40:18 | are all kinds of little changes and just energy is bouncing back after off |
|
| 40:25 | those interfaces. So we can understand of the features on this the velocities |
|
| 40:48 | to death interval velocity giving rise to . Some of this other stuff is |
|
| 40:56 | to the first breaks and that's really from multi pathing in the near |
|
| 41:02 | So multi poles are also going down the earth that were generated in the |
|
| 41:07 | surface. So for example, looking this in this data world here, |
|
| 41:23 | can imagine that the energy is coming into the earth, down, down |
|
| 41:31 | say it hits an interface way down and it sends up a reflection, |
|
| 41:38 | ? But we said there's an interface this depth too. So now I've |
|
| 41:41 | this energy coming back, it hits the bottom side of that impedance change |
|
| 41:48 | it generates another reflection down. So is a multi pa it's got that |
|
| 41:55 | bounce in it and we can look all this stuff inside the earth from |
|
| 42:03 | V S P. So what we're do with a, with a set |
|
| 42:09 | data like this, this is just shot and typically we do just process |
|
| 42:13 | shot. It's it's sparse. So going to look at the data, |
|
| 42:18 | gonna extract the the velocity logs, going to process this to get the |
|
| 42:25 | . I'm gonna make them look like seismic. And then we're going to |
|
| 42:30 | that reflection information to surface seismic. I can interpret sur seismic better. |
|
| 42:41 | . So um we can ask, , uh how do we do |
|
| 42:56 | So the first thing that we're gonna is just go in and pick or |
|
| 43:04 | our first arrivals. Now that first , as I said, gives us |
|
| 43:10 | to depth. But we're also gonna that to get the interval velocity. |
|
| 43:21 | let's imagine this slightly differently. So got the V S P here's time |
|
| 43:28 | now I've plotted the V S P depth and there would have been wiggles |
|
| 43:32 | . I'm just picking the first break on the wiggle. And so there's |
|
| 43:48 | and depth. So this first break gives us our time to death. |
|
| 43:54 | remember the slope here actually gives us interval velocity in depth. Now, |
|
| 44:07 | simplest thing that we could do is like what we did, we would |
|
| 44:13 | uh a depth interval, some depth it will here and look at the |
|
| 44:21 | increment across that depth interval, take slope output that slope for every two |
|
| 44:29 | and extract an interval, velocity in . And so that's sort of what |
|
| 44:38 | done here. We got time to . We take two points at different |
|
| 44:45 | , just the velocity, at least uh the time increment, the time |
|
| 44:48 | takes to go across that depth And I would put that, that's |
|
| 44:53 | interval. Velocity, take the other points out, put two points I |
|
| 44:59 | . So that's just plotting a slope a function of depth and that slope |
|
| 45:03 | velocity. So that's our log. this this guy now is our seismic |
|
| 45:09 | log in depth. Now, we be a little bit um more sophisticated |
|
| 45:27 | that doesn't take into account noise. had to go in and pick these |
|
| 45:33 | and there's a bit of noise in and there's a bit of miss pick |
|
| 45:35 | everything. So I've got some error my hicks in the time. A |
|
| 45:43 | bit. Uh I know the, know the depths pretty well. So |
|
| 45:48 | not much error in the depth, there is a little bit of slop |
|
| 45:54 | measurement error and um instrument air, kinds of little things that limit my |
|
| 46:01 | to pick accurately. So I've got noise. Whenever we have noise and |
|
| 46:09 | , we usually try to do some of fitting like least squares fitting. |
|
| 46:19 | that's um that's the algorithm here. the the process is this is the |
|
| 46:31 | that were given to me, you in and this is what uh sort |
|
| 46:39 | a, an interpreter, a V P interpreter for Slummer J or Reed |
|
| 46:42 | Halliburton or somebody would do, they'd given this data, they'd like |
|
| 46:47 | say, OK, pick the first energy. OK. That gives me |
|
| 46:53 | data set like this depth first arriving from this, determine the velocities. |
|
| 47:03 | now I've got to get a way do that. Just the slopes, |
|
| 47:06 | instantaneous, the the small slope will it. But there's a lot |
|
| 47:09 | there's gonna be a lot of chatter that because there's noise. So let's |
|
| 47:13 | it in a better way. Um figure out a better way to do |
|
| 47:21 | . And the better way is to a least squares fit and inversion. |
|
| 47:30 | the reason to understand this a little is this is the basis of a |
|
| 47:33 | of algorithms of geophysics, this least fitting idea. So let me, |
|
| 48:13 | here's the basic problem. The basic is I've got any X and Y |
|
| 48:28 | of points and I want to draw line through them. And the question |
|
| 48:35 | how do I do that? And is really fundamental to virtually everything we |
|
| 48:50 | in science or psychology or anything. know, you would, you would |
|
| 48:57 | a sense have this with baby weight age and over small periods. It's |
|
| 49:05 | gonna be kind of linear. The the child gets, the heavier the |
|
| 49:08 | gets and that applies to us The older I get the heavier I |
|
| 49:16 | . So, um we want we want to do something that we |
|
| 49:21 | fit all kinds of complicated curves, the simplest curve that we always fit |
|
| 49:25 | just a straight line. So there is the problem, I've got |
|
| 49:31 | points that I think should be on straight line, but they're not and |
|
| 49:36 | not because there's a bit of error how I picked it. I |
|
| 49:44 | if a grandmother was doing this, might say, Oh, you know |
|
| 49:46 | , I can't remember exactly what the date of birth was. It was |
|
| 49:51 | seven or was it May 10? . Well, take one of |
|
| 49:56 | Well, you were off a couple days. So there's, that's it |
|
| 49:58 | then I measured, I didn't have very good measurement device. So uh |
|
| 50:03 | was off that day and then somebody measured it and it was a little |
|
| 50:05 | off da da da. So we fit this thing. Um So first |
|
| 50:09 | all, we have to, we to define what are we trying to |
|
| 50:13 | fit, that's a line. Why equal to M X plus B? |
|
| 50:17 | I'm just trying to find the line then what are we going to try |
|
| 50:21 | minimize? And there are a lot different ways we could do this. |
|
| 50:25 | let's just say you knew exactly how the child was, for example, |
|
| 50:32 | this way scale was a bit So there's a measurement error there. |
|
| 50:36 | what we're gonna try to do is minimize the distance from the line to |
|
| 50:40 | Y value. So we're gonna say all the errors in the Y |
|
| 50:44 | we could say the errors in the value. And I'm gonna try to |
|
| 50:47 | this perpendicular distance. But I'm gonna no, I'm just gonna try to |
|
| 50:53 | this vertical distance. So just going to your, I, I'll uh |
|
| 51:03 | post this, it takes a little to do it. So what we |
|
| 51:08 | do is just like here, I to fit a line, Y is |
|
| 51:12 | to M X or beta two X B, that's my line. And |
|
| 51:19 | they're the Y values from the real . And I want to select B |
|
| 51:25 | and B two such that we have minimum error in Y. So let's |
|
| 51:40 | , I've got four points. If was no error, then um value |
|
| 51:50 | one times M the slope plus the with equal six. So here's my |
|
| 51:56 | equations and I've got to put beta and beta two to give the best |
|
| 52:03 | . So we're gonna say here's the of the line, here's the real |
|
| 52:10 | prediction of the line, real value of the line real value prediction da |
|
| 52:15 | da. So I'm gonna try to that misfit. So I'm taking the |
|
| 52:23 | , here's the, here's the, proposed line, here's the misfit I |
|
| 52:28 | it and I'm trying to find a of beta one and beta two that |
|
| 52:36 | minimize this. Now, you can that uh if we go down to |
|
| 52:42 | that out, we are taking the of the error with respect to beta |
|
| 52:50 | and beta two that gives us two and we're trying to set those to |
|
| 52:54 | . So that's strictly trying to We're trying to find the minimum value |
|
| 53:01 | solving for beta water B and beta M. So there we go, |
|
| 53:09 | go through all this kind of In the end, we're trying to |
|
| 53:15 | M and B or beta one and two and we get with this |
|
| 53:21 | So you kind of have to go that on your own. But that's |
|
| 53:24 | basic idea. The whole idea is got a bunch of data points. |
|
| 53:29 | trying to fit a line through I say that I'm trying to minimize |
|
| 53:32 | distance between the theoretical line and the data. When I minimize distance, |
|
| 53:39 | the least squares minimization. I take derivative of the error with respect to |
|
| 53:44 | two slope variables gives me two equations solve and I get the answer. |
|
| 53:53 | I'll, I'll post that you can through it. Um I simplified it |
|
| 53:57 | but I couldn't find it. But , that's, that's the idea. |
|
| 54:20 | , so you can imagine the way works. And if you were gonna |
|
| 54:25 | code to do it, which I this was a chapter in my thesis |
|
| 54:30 | time ago. Um So how we solving it? We imagine, first |
|
| 54:37 | all proposing just a velocity with death through it to get predicted travel |
|
| 54:53 | compare those predicted travel times to the ones and then just do the least |
|
| 55:00 | fit to upgrade the velocities to make match. So that's called an inverse |
|
| 55:06 | . So very simply I've got I'm gonna put try to produce a |
|
| 55:13 | that when I ray trace through it travel times that match. And I'm |
|
| 55:17 | keep on altering the little velocities until ray trace travel times match the |
|
| 55:26 | And then the error that I've got my simple velocity model, I'll plot |
|
| 55:31 | here. This is the mismatch between real data and the calculated. And |
|
| 55:35 | here's the wiggle room on the velocity these little error bars, I can |
|
| 55:40 | a velocity anywhere in there and it the observations. So those are really |
|
| 55:46 | things in an inverse problem. But our purposes here, that's the |
|
| 55:55 | And so that was the first algorithm ever sold after grad school. So |
|
| 56:03 | how you do it for our We just produce a velocity log from |
|
| 56:11 | travel time picks. Then that this log is like any of our other |
|
| 56:18 | . It's the seismic velocity in depth then we're gonna use it like we |
|
| 56:22 | all the sonic logs and um and for seismic data processing. So that |
|
| 56:33 | the first thing that we get out the BS P time to depth and |
|
| 56:40 | with death. Good. OK. , let's take 10 Stephanie, let |
|
| 56:47 | coagulate and meditate and uh marinate. , and we'll see, we'll see |
|
| 56:55 | shortly. OK. OK. Uh Welcome back. We were uh |
|
| 57:05 | were talking about this uh inverse problem by inverse really mean that we're taking |
|
| 57:12 | real data and determining what could have it. So uh as oppose of |
|
| 57:22 | opposed to taking uh properties and finding or simulating what they could produce in |
|
| 57:30 | of waves propagating through them or something . Now, we're taking real data |
|
| 57:34 | has gone through the medium and we're , what are the properties that could |
|
| 57:39 | caused that? And so that is reverse or inverse of the uh previous |
|
| 57:46 | . The forward problem knowing properties, observations. Now we're taking observations and |
|
| 57:51 | properties. So that's the inverse. or the inverse problem, this was |
|
| 57:55 | classic, simple or straightforward inverse that OK, I've got energy that's going |
|
| 58:01 | into the earth. I'm just seeing long it takes to get there. |
|
| 58:06 | from how long it gets to what velocity does it have to go |
|
| 58:10 | to produce those times? And that now called a travel time inverse for |
|
| 58:19 | . So for our purposes, what get out of that is we're gonna |
|
| 58:22 | our time to depth again and our velocities. And we've got a little |
|
| 58:27 | more because we know a little bit errors and a little bit more about |
|
| 58:34 | of possibilities and, and measurement uh and stuff like that. So that's |
|
| 58:41 | uh a start at understanding inversion a better. But now we've got some |
|
| 58:47 | . So that's one thing. The thing we got out of our uh |
|
| 58:50 | BS P. Now, once we, we talked about this, |
|
| 58:59 | got depth, this is looking at data and time and we've got energy |
|
| 59:04 | into the earth. And in what's the slope right here again, |
|
| 59:14 | a positive slope. Yeah. What this slope mean in terms? Oh |
|
| 59:20 | . Yeah. So it's just velocity change over time change gives us the |
|
| 59:27 | . But as I mentioned, we've all these other parallel uh events and |
|
| 59:31 | saw them in the data and we that that's just multi passing in the |
|
| 59:36 | surface that gives rise to this whole of stripes that are downgoing. So |
|
| 59:44 | we can understand that. And then we hit an interface, we set |
|
| 59:48 | a reflection. So we could say is a positive slope, this is |
|
| 59:52 | negative slope. The negative slope means the waves are coming back to the |
|
| 59:56 | , they're upgoing or upcoming. And positive slope means that they're downgoing. |
|
| 60:15 | let's uh let's do another little uh little exercise. Here's some more data |
|
| 60:24 | we've got depth going from 200 to m deep and time going to 600 |
|
| 60:31 | 6000.6 seconds. And you can see uh this is real data game energy |
|
| 60:38 | down into the earth. And so just as an exercise, we could |
|
| 60:44 | , what's the Interval velocity between 500 and 1000 m? And I Thoughtfully |
|
| 60:56 | you some of this. So what's p wave interval velocity between 500 and |
|
| 61:02 | m? You can just So at -125. Yeah. So .49 -1 |
|
| 61:18 | have done that in my head. . OK. And then what's the |
|
| 61:25 | velocity? Oh So then the interval would be. So that's 500 divided |
|
| 61:37 | 0.24. So 2083 m per Yeah, so that's the game we |
|
| 61:47 | and love that. But um now had a share wave V S P |
|
| 61:52 | too that used the share wave source you can see that we've picked, |
|
| 61:57 | got a shear wave coming down. what's the shear wave velocity? 500 |
|
| 62:08 | 1000? Let's see. So that's point that's 0.8 to one. So |
|
| 62:21 | point, let's say nine. So -0.9, 0.5. So that's about |
|
| 62:38 | . Yeah. So then I V S would just be 2083 divided |
|
| 62:48 | Wow. So two point oh Yeah, somewhere around there. And |
|
| 62:56 | and that's, that's a boat in ballpark. We expect that the, |
|
| 63:01 | P wave is about twice as fast the shear wave. So that uh |
|
| 63:10 | all makes sense. And now um we can immediately manipulate the state a |
|
| 63:16 | bit and understand it. So likewise uh I'm just looking at some more |
|
| 63:24 | . So we get to understand these . We can see that um This |
|
| 63:29 | with an 80 level A race. going down uh about 1500 m again |
|
| 63:39 | dynamite, Primacor P wave coming down likewise, if we could place the |
|
| 63:53 | uh side by side and blow one the other that creates a shear |
|
| 63:57 | And we could see the shear wave coming right down and reflecting back much |
|
| 64:03 | slopes because much lower blooms. So could quickly just think. Well, |
|
| 64:15 | , let me just this area, don't know where it is. It's |
|
| 64:18 | in California. Bjorn Paulson did a of his work in California. So |
|
| 64:23 | could see that uh we're going from surface to around 1500 m deep. |
|
| 64:32 | takes the P wave approximately 600 milliseconds go 1500 m. So 15000.6 into |
|
| 64:41 | is something like 2500 m/s. Then could see that the shear wave, |
|
| 64:52 | surface takes around 1600 milliseconds To go same depth down to 1500 m. |
|
| 65:08 | it's just less than 1000. So around 900 m per second. So |
|
| 65:15 | divided by 1600 gives us around 95 50 or somewhere around there meters per |
|
| 65:26 | . So in this area, The ratio is probably somewhere around 2.5. |
|
| 65:37 | probably mushier, mushier rock good. those are just some examples to the |
|
| 65:51 | home and we can get the uh P waves and its velocities and then |
|
| 65:55 | shear waves and their velocities. So again, uh if we just picked |
|
| 66:05 | first brakes, here's depth, here's , we just got the first |
|
| 66:09 | We'd see this kind of line. we said below, if we had |
|
| 66:18 | Sonic log, we could just sum of the microseconds per meter or per |
|
| 66:24 | together to get a time to So remember the Sonic log was giving |
|
| 66:32 | , we've got it in depth. then for every depth that said how |
|
| 66:37 | it took the wave to go across foot or a meter? That was |
|
| 66:41 | Sonic log. I would put microseconds time per meter. I could take |
|
| 66:46 | one of those microseconds per meter at point, add them all together. |
|
| 66:51 | that gives me a total time to . That's the way we did our |
|
| 66:57 | using the Sonic log. That's how got our time to depth estimate or |
|
| 67:01 | to time estimate. Now you could , well, why do you need |
|
| 67:08 | BS P? Well, because the logs don't go to the surface. |
|
| 67:13 | I don't know what the time was the surface to wherever the Sonic log |
|
| 67:19 | . Plus the Sonic log is just a foot or so into the |
|
| 67:25 | And seismic sees much further into the than that. Plus The vibration in |
|
| 67:33 | sonic log that we're using is around hertz. So it's a very, |
|
| 67:39 | fast vibration. We know that seismic somewhere around 50 Hz. So Sonic |
|
| 67:52 | times and seismic travel times are a bit different. So that's why we |
|
| 68:00 | actual seismic wave propagation to a point the well or the V S P |
|
| 68:07 | the sparse V S P is called check shot. And it's called a |
|
| 68:12 | shot because it's checking the sonic time death. It's actually calibrating it or |
|
| 68:21 | it. So, but it's called check shot to check the integrated |
|
| 68:34 | And remember the reason that we're doing of this is that we're trying to |
|
| 68:38 | surface seismic in time to well logs depth. So I need that depth |
|
| 68:44 | time mapping. We did it grossly just integrating the sonic log. But |
|
| 68:51 | I can use check shots from real to fix the sonic log a little |
|
| 68:58 | to make it more relevant to seismic . And so you can see that |
|
| 69:02 | integrated Sonic log or the sum, I mentioned is not too different than |
|
| 69:08 | actual check shots, but will force integrated Sonic log to agree with the |
|
| 69:14 | shots by slightly changing the sonic log and will change the sonic log |
|
| 69:24 | Such that when I add them all , they agree with the actual seismic |
|
| 69:30 | time to that depth. That's called the Sonic log using checks shots. |
|
| 69:39 | again, we're doing this because I seismic times to match the true |
|
| 69:48 | integrating the sonic log or summing the log, like I said, uh |
|
| 69:54 | these little problems and so we need fix them and we fix them by |
|
| 69:58 | the check shots. So again, our log started up here, we're |
|
| 70:04 | together we some, some, some we're off. So I paste the |
|
| 70:11 | log here and then I forced the velocities to be a little bit different |
|
| 70:18 | that they sum to be the actual . And that's the calibrated Sonic |
|
| 70:24 | And that's the sonic log we want then we can use it for synthetic |
|
| 70:27 | energy. So you can also get idea of a resolution here. Here's |
|
| 70:44 | actual measured sonic log with all the . And then you could see the |
|
| 70:51 | the V S P velocities match the log pretty well. And we could |
|
| 70:58 | maybe gasped velocities from previous work or surface seismic or something, but that |
|
| 71:04 | work quite as well. So the the BS P has worked quite |
|
| 71:18 | OK. And we can do that any measurement. We just need a |
|
| 71:23 | that creates a vibration uh strong enough that we can see it with our |
|
| 71:28 | in depth. And here's a little that uses a whack one way and |
|
| 71:32 | a whack the other way. And gives us a polarized sheer polarized one |
|
| 71:38 | , an up movement first or a movement, we can overlay them and |
|
| 71:41 | we can get a really good pick I know that I've got a share |
|
| 71:46 | pros that way and one that way they break the opposite way. So |
|
| 71:51 | breaks the opposite way. I know that's a share wave. So we |
|
| 71:57 | whack just down giving us a P , I can whack sideways with a |
|
| 72:01 | such as this that gives the shear pick the first break times P wave |
|
| 72:07 | wave and get the velocity log. , you might say, well, |
|
| 72:18 | what are these shear wave velocities used in the near surface? Like this |
|
| 72:22 | just not relevant to my life. , the reason that it, it |
|
| 72:30 | is is that any time we're going build such as a house up in |
|
| 72:35 | woodlands or a shopping mall or anything that, we actually have to know |
|
| 72:41 | properties of the near surface soils, sediments, we have to know their |
|
| 72:48 | and we have to know whether they're enough to build on. So if |
|
| 72:56 | gonna build a tower in downtown I have to know that the sediments |
|
| 73:03 | the, on which I'm building are enough to hold the building. And |
|
| 73:09 | best predictor of that is the shear velocity. And in fact, by |
|
| 73:18 | , we have to classify the sediments to their sheer strength because their sheer |
|
| 73:23 | tells us how well they can support building. So there's something called AVS |
|
| 73:31 | , the shear wave velocity down to m. And when we go out |
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| 73:37 | make these measurements, we're going to all these measurements, get the shear |
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| 73:41 | velocity averaging down to 30 m. then it has to be greater than |
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| 73:47 | certain value like three or 4 or m/s to qualify that soil as being |
|
| 73:56 | enough to support a building. So can see in the um and say |
|
| 74:13 | little case here We go down six and the first few meters of the |
|
| 74:26 | surface Has shear wave velocities that are 240 m/s or 2 54. So |
|
| 74:38 | pretty low up here. So in jurisdiction, it might be that You |
|
| 74:46 | to build on something that has a wave velocity of 300m/s, which is |
|
| 74:57 | , this is 4 15, this 2 54. So what you're gonna |
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| 75:01 | to do is excavate 20 ft, the 1st 20 ft of soil off |
|
| 75:07 | this is pretty standard but take that 20 ft of soil off and then |
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| 75:12 | on this material here. So the 30 has to be above a certain |
|
| 75:20 | and we're gonna correlate all this up , to produce maps that show you |
|
| 75:26 | you have to do. How much do you have to remove to actually |
|
| 75:29 | on it. So around 10 years , after the big earthquake in |
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| 75:38 | you might remember that enormous earthquake in that killed all the people. We |
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| 75:44 | a uh a project, an S G I for the borders project. |
|
| 75:48 | we went down to Haiti and we the velocity of the sediments in a |
|
| 75:54 | of these areas and in the areas were destroyed, the velocity of the |
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| 76:00 | , the shoe velocity was really So the sediments are weak to begin |
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| 76:06 | . And then when you shake they become even weaker and they amplify |
|
| 76:11 | motion. So we made measurements down Haiti that showed, you know, |
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| 76:17 | a lot of these areas, the are just too weak to support |
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| 76:22 | And even in Port Au Prince where um the capital in those areas where |
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| 76:27 | excavated properly and removed the soil and built on decent rock. Uh The |
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| 76:35 | stood, there was a big actually, it was a Canadian tower |
|
| 76:38 | was uh built for and it it that massive earthquake, no problem. |
|
| 76:44 | was built in a decent area and also uh according to standards. So |
|
| 76:48 | problem. But if you build in poor area with poor construction, the |
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| 76:53 | are uh kind of predictable unfortunately and very good. So that's one of |
|
| 76:59 | uses of the shear wave near surface . It's for civil engineering and all |
|
| 77:06 | are zoned that you have to have certain rigidity strength of the material to |
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| 77:11 | up. So there we go, used to work at a uh geotechnical |
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| 77:19 | and we would do the Triax like shear tests or whatever. But I |
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| 77:26 | we mostly did it for um pipelines we did a lot of work for |
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| 77:30 | Fugro Kinder Morgan stuff like that. we would run a bunch of different |
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| 77:35 | to like classify soils and send everything to them. Oh, cool. |
|
| 77:40 | , you know all about that Well, that's great. So what |
|
| 77:44 | the, what was the company? , uh it was called, it |
|
| 77:47 | a small startup. It was geotechnical. Oh cool. And now |
|
| 77:53 | you take soil samples or do field or what it was all? Um |
|
| 77:59 | sent us the samples. So they literally just send us like bags of |
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| 78:04 | or they would send us like casings um we would have to run like |
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| 78:10 | . So for like liquid limit, limit analysis, um the tri axs |
|
| 78:17 | mini veins, stuff like that. it was, it was pretty |
|
| 78:19 | I really liked it but he was not, it was the company, |
|
| 78:24 | think it was almost out of So I had to, I had |
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| 78:26 | get out why I could. So it um great ideas, I |
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| 78:34 | you just, you just have to enough work and manage it well enough |
|
| 78:38 | yeah, so did they kind of out of work or they just |
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| 78:43 | the employee turnover rate was like In 90% like the the owner, he |
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| 78:50 | just um it was impossible to work . So he only had like, |
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| 78:56 | years of working experience and he's I'm gonna start my own company but |
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| 79:00 | didn't actually know how to run a . So he had never, it |
|
| 79:04 | really worked before. Yeah. yeah, that's, that's, that's |
|
| 79:16 | bad because great idea. Really interesting , really useful. Um, but |
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| 79:26 | manage. Right. No, I , I would still be working there |
|
| 79:30 | it wasn't, it wasn't for I really enjoy it. I was |
|
| 79:33 | , oh, I finally get to with, like, rocks and stuff |
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| 79:36 | that and it was cool. I liked it. Huh? Yeah, |
|
| 79:42 | , that's excellent. You know With our field cap this year? |
|
| 79:45 | trying to involve, uh, Emily and she's a soils person and that |
|
| 79:53 | be a, so she's got we're gonna have the students auger and |
|
| 79:59 | kind of do geochemical analysis of the . But it would be a really |
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| 80:05 | idea to do a mechanical test. , this, uh, Triax |
|
| 80:15 | How did, how, how did work? What was the equipment? |
|
| 80:18 | , well, you needed a, , what was it? It was |
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| 80:23 | actual, like, set up? , it's like a canister and then |
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| 80:27 | fill it with water and, it would be hooked up to the |
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| 80:33 | that you plug into and you can , you set, like the |
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| 80:36 | the customer would sell us. We this combining pressure and we want this |
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| 80:42 | and then you would just start it then as soon as the, because |
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| 80:45 | had to shave it a certain So it had to be a |
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| 80:48 | like a certain cylinder pretty much. then you would just wait until basically |
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| 80:55 | , your sample you would see the and like that would be like |
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| 81:00 | like the breaking limit pretty much. . So this was a, this |
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| 81:07 | was actually to kind of bring the under pressure to failure so that |
|
| 81:12 | Mhm. Yeah. The customer wanted know when is this gonna fail? |
|
| 81:17 | . Huh. Well, you know ? That's, that's exactly it. |
|
| 81:23 | it's, it's really the rigidity that you when it's gonna fail the rigidity |
|
| 81:28 | this material. Yeah, I, think it'd be great if we could |
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| 81:32 | some kind of, I'm just gonna that down some kind of mechanical soil |
|
| 81:42 | so that we could get a geophysical from uh from these sediments. |
|
| 81:49 | interesting. Well, so there you . Uh that would be kind of |
|
| 81:55 | truth thing or sample testing. So something like this, you make these |
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| 82:00 | measurements And you would get uh say m/s for the shear wave velocity, |
|
| 82:09 | take the density, you get the out of that. And then the |
|
| 82:13 | is something that you're gonna to correlate your lab measurement. So with the |
|
| 82:21 | measurements and this in situ measurement and what you're also gonna do is refraction |
|
| 82:29 | with uh a horizontal source. And you're gonna do the line surveys and |
|
| 82:37 | a map of all these wave velocities then calibrate them with uh well measurements |
|
| 82:44 | and then calibrate those with lab measurements you were doing. And that's a |
|
| 82:49 | thing and then put that all together map it for the whole area and |
|
| 82:55 | , here's your map for this This is where you can build, |
|
| 82:59 | is where you need to remediate. is uh what the remediation plan would |
|
| 83:05 | to be. So that's uh that's part of the whole thing. Part |
|
| 83:12 | the whole project would be to do . This is great because you've got |
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| 83:16 | lab tied into your in situ tied your broad surveys to create the map |
|
| 83:22 | people have confidence in. And so uh that's really useful and required. |
|
| 83:36 | brother is a developer and actually we building a part of a subdivision that |
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| 83:41 | went the other way. So we to excavate to put in the um |
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| 83:46 | facilities, the sewers, the the water and all that stuff. |
|
| 83:51 | it turned out that actually very hard would have periodically come to the |
|
| 83:57 | So you're building the subdivision, most it has excavated material for all the |
|
| 84:01 | sewers and pipes and stuff. But once in a while, hard rock |
|
| 84:06 | come up and you think, ok, but you have to go |
|
| 84:10 | that harder rock. And it means got to bring in excavators and all |
|
| 84:14 | of other equipment that will break hard . So in a sense, you |
|
| 84:18 | the other um surveying and mapping techniques get a map of the area that |
|
| 84:25 | , where is the rock really Because I gotta run facilities through it |
|
| 84:33 | why do you need to do Because when you're budgeting for the uh |
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| 84:37 | or the development of facilities just excavating improving the area, leveling it, |
|
| 84:46 | it. Da da da. That a huge cost. So when you |
|
| 84:54 | to budget that properly, you say at I need X dollars to put |
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| 85:00 | all the facilities here. So that's and how do I do it |
|
| 85:06 | where do I do it? And I should avoid this area a little |
|
| 85:09 | because the rock is so hard It's too expensive to put stuff |
|
| 85:12 | So let's just build uh a little right in that area or like they |
|
| 85:20 | in that huge subdivision near Premium Outlet in Hockley in Cyprus. There's the |
|
| 85:28 | that goes right beside Premium Island huge fault. They built an enormous |
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| 85:33 | right there. And fortunately they had good sense to make a bayou and |
|
| 85:43 | park out of that huge fault that right through the subdivision. Otherwise they |
|
| 85:48 | have had a lot of very, angry people with a great deal of |
|
| 85:57 | discussion and remediation because that fault And so you really want to know |
|
| 86:05 | . And they, they did, they put a, they put a |
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| 86:07 | kind of a park bayou feature right the fall to, uh, to |
|
| 86:12 | building anything on it. Oh, . Well, um, that's |
|
| 86:20 | It's great that you had some relevant and you really enjoyed that work. |
|
| 86:24 | , I think it's really interesting especially to tie it into all the |
|
| 86:27 | stuff. Mhm OK. So, here's another one that's trying to use |
|
| 86:39 | waves. You can see it says , Just down to 44 m, |
|
| 86:44 | can quickly look at this and immediately the velocity. And so I just |
|
| 87:09 | this data a few days ago. I thought I would include it. |
|
| 87:13 | Now, what I'm gonna let you is I'm just looking at this and |
|
| 87:20 | see that there's an error and your is to find, where did I |
|
| 87:30 | a mistake here? Is it the because it's already in seconds? |
|
| 87:46 | So if you look at this, coming down here and this is, |
|
| 87:51 | was just trying to annotate these so could see them. And so that's |
|
| 87:59 | correct. The answer is correct. you can see with this, I |
|
| 88:14 | a typo should have been milliseconds, seconds. So we'll now fix |
|
| 88:30 | There was a great seismologist called Kay . He's one of the most famous |
|
| 88:36 | . One of the most famous he wrote a two volume book on |
|
| 88:40 | seismology, huge two volumes that are of the uh the Bible for |
|
| 88:50 | And he was one of my advisors grad school and he had a course |
|
| 88:55 | inverse the and the whole chorus was seismic inverse theory. And he gave |
|
| 89:04 | his chapter of the book on And our job for the whole term |
|
| 89:11 | to find a mistake in it. he gave us the draft of the |
|
| 89:15 | . And so you've got all I want you to find a |
|
| 89:21 | And so they, there were 10 us in the course and we worked |
|
| 89:26 | three months going through everything red doing everything in that book trying to |
|
| 89:32 | a mistake because Kaya, again, is sort of like the Bible and |
|
| 89:38 | was sort of like the seismology So, and finally, I found |
|
| 89:42 | mistake in the chapter and I was happy. It was a typo like |
|
| 89:48 | . That's the only thing that we in the whole semester. So |
|
| 89:59 | that's still around. But you can just as another example. Now, |
|
| 90:03 | I was looking at this and this just uh We can see the first |
|
| 90:08 | wave arrival. It's got a ve of 1892 m/s. It's in the |
|
| 90:12 | surface that all makes sense. All . There's another wave that's coming down |
|
| 90:19 | that's probably a tube wave. In words, when we whack the |
|
| 90:26 | there's fluid in the bore hole and a wave that just propagates in the |
|
| 90:30 | in the bore hole, it's a slower than the P wave arrival. |
|
| 90:35 | very consistent. It's high amplitude and usually low frequency. So this is |
|
| 90:43 | slightly slower, high amplitude wave. I, I think that doesn't tell |
|
| 90:47 | much about the, the rock, tells us about the fluid. And |
|
| 90:53 | this is something we're always trying to rid of because it tells us about |
|
| 90:57 | flu in the borehole, but we really care about that. So, |
|
| 91:00 | we always try to get rid of , but it's, it's a source |
|
| 91:03 | noise. Ok. So let's, have a look at another one you |
|
| 91:14 | see now this is plotted the other we've got depth going down, beautiful |
|
| 91:21 | waves coming down. Can you see little bit of change in the slope |
|
| 91:28 | ? Uh Yeah, very slight. pretty small. Uh There's some change |
|
| 91:34 | around here and maybe a little bit here. But look at how those |
|
| 91:41 | represent. We've got air waves coming , little change, boom, little |
|
| 91:46 | , some around here. There's a and we get this huge reflection. |
|
| 91:54 | we're, this VSB just started at m. So there's normally it would |
|
| 91:58 | way back to the surface. We see lots of stuff bouncing around so |
|
| 92:03 | is downgoing energy but multi pa from up in the near surface, now |
|
| 92:15 | gonna take a step into the next . The, the G phone itself |
|
| 92:20 | a vertical component that we are familiar , but it also has a horizontal |
|
| 92:30 | and there's nothing magical about that. just senses horizontal motion, it senses |
|
| 92:35 | motion. But if we look at horizontal sensor, we can see that |
|
| 92:43 | not too much happening in the P . So we've got the vertical channel |
|
| 92:48 | is um depth and and say we it the Z channel and then the |
|
| 92:55 | channel is the horizontal channel. Now can imagine with the P wave is |
|
| 93:02 | down, it represents itself on the channel a lot because its particle motion |
|
| 93:07 | like this and that the vertical channel sensitive to that particle motion. The |
|
| 93:12 | channel is being oscillated up and But it doesn't feel anything you can |
|
| 93:18 | the horizontal channel up and down. only sensitive to horizontal motion. So |
|
| 93:25 | the horizontal channel, on the horizontal at all these depths, there's almost |
|
| 93:31 | happening with the P wave arrival because not sensitive to that vertical motion. |
|
| 93:49 | , this is slightly offset, we this velocity change and we're generating a |
|
| 93:57 | P wave reflection. But if the wave velocity changes, we said the |
|
| 94:03 | probably changes. And then we know the mud rock line of P wave |
|
| 94:09 | changes, shear wave velocity probably So we get conversion from P wave |
|
| 94:20 | P wave reflection but also from P to shear wave reflection. So getting |
|
| 94:27 | bit more sophisticated than what's really happening the earth, we have the P |
|
| 94:32 | come down, it hits this it transmits it converts to a shear |
|
| 94:37 | downgoing and it converts to a shear upgoing. And that is our energy |
|
| 94:51 | . Mhm And how a Mayo might mentioned, did anybody cover a B |
|
| 94:58 | A versus Assad and the Zots equations all that stuff? I think I |
|
| 95:06 | I do remember it, I mean I like can I like say |
|
| 95:09 | No, but I do remember going that, I think OK. So |
|
| 95:14 | again, when, when we've got P wave coming in at some |
|
| 95:19 | we get of course a P wave but we also get a shear wave |
|
| 95:24 | . And then some of the P energy goes through the interface as a |
|
| 95:27 | wave and some of it goes through interface as a shear wave. So |
|
| 95:32 | get this one P wave coming down it sprays out four waves upgoing |
|
| 95:39 | upgoing shear wave reflection, transmitted P transmitted. Sure. And that's what |
|
| 95:44 | Zots equations tell us. And that's the energy partitions or separates. And |
|
| 95:54 | that seems OK, those are all of funky equations. But does it |
|
| 96:00 | happen? And yes, it does real data. We've got the P |
|
| 96:05 | coming down. P wave transmits like talked about. It also reflects, |
|
| 96:14 | it also transmits with a shear wave it reflects with the shear wave |
|
| 96:20 | How do we know this is shear ? Well, you can see the |
|
| 96:24 | , this slope is much greater than slope. This slope is behind the |
|
| 96:32 | break. So P wave down got little bit of P wave up |
|
| 96:39 | Sheer wave bob P wave down and wave down. So this is a |
|
| 96:51 | example of Zots inaction. And this what happens at every interface. It's |
|
| 97:00 | more um more obvious here. So gotta leave this, this guy with |
|
| 97:24 | . Uh Just to do what we've talked about um annotating the direct |
|
| 97:30 | P and we're gonna show how to the dominant frequency of that and then |
|
| 97:38 | calculate the interval velocity across here. then the upgoing P wave reflection, |
|
| 97:44 | understand that uh downgoing shear wave, can see that there are lots of |
|
| 97:53 | downgoing shear waves here. And from slopes, we can calculate a share |
|
| 98:02 | velocity. This is the vertical channel shows us mostly P wave energy. |
|
| 98:18 | is the horizontal channel that shows us shear wave energy because remember a shear |
|
| 98:23 | propagating down like that its particle motion perpendicular. So on this horizontal |
|
| 98:33 | we see mainly shear waves because that's their motion is. So even a |
|
| 98:38 | shoe wave that's propagating vertically more or vertically. Its motion is more or |
|
| 98:44 | horizontal propagation particle motion. So these are picking up just particle motion. |
|
| 98:54 | the actual physical motion? P The particle motion is in the direction |
|
| 99:00 | propagation. So down shear wave, particle motion is perpendicular or or orthogonal |
|
| 99:07 | the direction of propagation. So we a lot of that data on the |
|
| 99:11 | or the horizontal channel. So do uh just annotate this guy |
|
| 99:25 | and um P wave velocity down where get reflections, shear wave velocities down |
|
| 99:33 | we get shear wave reflections and Now let's also uh start to pick |
|
| 99:42 | this seismic and this is important for seismic. So this is uh we |
|
| 99:47 | through this a few years ago and just to remind you how to get |
|
| 99:51 | dominant frequency. So if you're uh any seismic and somebody shows you |
|
| 99:58 | this is the first thing that I'm gonna look at. So any kind |
|
| 100:09 | seismic, whether it's earthquake ultrasonic I'm always gonna try to figure out |
|
| 100:15 | the frequency content of the data. , and, and the, the |
|
| 100:22 | simple way to do that is to look at how long does one cycle |
|
| 100:29 | ? And the number of cycles per is the frequency and we express that |
|
| 100:37 | hers cycles per second. So here's example, I've got some data. |
|
| 100:50 | just gonna look at a single trace a single seism ground and look at |
|
| 100:57 | full cycle. It could be peak peak trough to trough, zero crossing |
|
| 101:03 | second zero crossing. However, we to pick one cycle often peak to |
|
| 101:08 | is just the simplest way to do or trough to trough. But you |
|
| 101:14 | see here that say zero, second crossing one cycle, I look at |
|
| 101:22 | scale that's 1, 40, That's 75. So that's, that's 35 |
|
| 101:38 | right across there. So we're a bit shy of the full amount. |
|
| 101:45 | this one cycle is 33 milliseconds. one cycle takes 10.33 seconds, one |
|
| 101:59 | takes 10.33 seconds. And we could that that's actually the frequency one cycle |
|
| 102:08 | 33 milliseconds. But we don't usually that we usually say what's the number |
|
| 102:14 | cycles per second? Not how long cycle takes, but how many cycles |
|
| 102:21 | in a second. So if one takes 10.33 milliseconds, then 30 cycles |
|
| 102:32 | about one second. So this is period, our period takes 33 |
|
| 102:46 | That's the period. One over the is the frequency Which in this case |
|
| 102:54 | 30 hertz. So whenever you see data, I always look at |
|
| 103:01 | how long does one period take? then one over that is the number |
|
| 103:06 | cycles for a second and that you to be able to do immediately without |
|
| 103:18 | . So once again, just pick to peak, that's one cycle. |
|
| 103:22 | the period? Then one over that the frequency. Now, um so |
|
| 103:27 | done this quickly, this is called dominant frequency because there are a lot |
|
| 103:31 | frequencies in most wavelets, but the to peak period is the dominant |
|
| 103:39 | And one over that gives us the frequency. And if we actually do |
|
| 103:44 | furrier transform of this trace, which gonna give us all of the different |
|
| 103:52 | content, you can see that the frequency Or the maximum frequency is around |
|
| 104:00 | Hz. So we quickly look at uh the timescale get the period, |
|
| 104:13 | time of one cycle one over that the frequency. And that's a very |
|
| 104:18 | estimator for the frequency, the dominant of the data. And then there's |
|
| 104:26 | general rule that whatever the dominant frequency the band is about that wide |
|
| 104:37 | So in this case, the dominar is 30 hertz. Excuse me, |
|
| 104:41 | band is the the width of the of frequencies that are in there. |
|
| 104:48 | we can see that This is 30 a 30 Hertz band is about that |
|
| 104:58 | . And that's gonna capture most of data that's down 10 or 20 DB |
|
| 105:07 | very, very approximate. You might it on either side, you might |
|
| 105:10 | I'm gonna take 30 hertz on either and that's going to give me most |
|
| 105:17 | the frequencies And you can see this scale here again. So 20 DB |
|
| 105:30 | from the maximum is a factor of . So I've got 10 more 30 |
|
| 105:40 | Sinusoids, then I do 10 Hertz lines. So this is the amplitude |
|
| 105:49 | and we're saying that uh this is a value of 100 20 DB |
|
| 105:58 | I've got 10 of these guys. at this frequency, My total bandwidth |
|
| 106:03 | something like say 20 BB down. I'm gonna say that's my band. |
|
| 106:08 | usable band, it looks like the is down here. So 30 DB |
|
| 106:12 | is something like five Hertz out to , I don't know, maybe 100 |
|
| 106:20 | . So that's the band width of data. There's still energy out |
|
| 106:25 | but it looks kind of flat. I'm gonna think that that's more |
|
| 106:29 | This is real signal that's rising above background. So it, it looks |
|
| 106:35 | me that the noise floor noises. , somewhere around here. This is |
|
| 106:40 | signal. My real signal is something 5-100 Hz. So now we're dissecting |
|
| 106:49 | amplitude spectrum based on a really simple that gives us the dominant frequency and |
|
| 106:55 | the frequency bandwidth is gonna be around by somewhat like the same amount I |
|
| 107:06 | got this. But this is like , pretty blown up and stuff like |
|
| 107:11 | . So how would I do it something like the previous image works? |
|
| 107:14 | small? Like, how would I ? I mean, I can see |
|
| 107:18 | peaks and stuff like that but I , I would count more cycles. |
|
| 107:24 | it's a good question. You're exactly . Um, in a real case |
|
| 107:30 | the screen, I would just expand screen. It's digital data and you'd |
|
| 107:33 | fiddling around with this, on, the screen. But if you're given |
|
| 107:38 | or it wouldn't expand, I would take more cycles and I do this |
|
| 107:42 | the time. Somebody gives you a record or something and you're right, |
|
| 107:46 | can't see it. So what am gonna do? Like this data? |
|
| 107:51 | is a bit of a pain in butt. So we've got our scale |
|
| 107:55 | . So each one of these divisions , is how much uh 0.1 .1 |
|
| 108:04 | . How many milliseconds? Is that 0.1 2nd? Oh, it'd |
|
| 108:16 | wait milliseconds. Milliseconds is 1000. it be 1000 milliseconds. No |
|
| 108:23 | It could be 10. No, . I'm so bad at this. |
|
| 108:32 | 100. Yeah. Yeah, that to draw. Yeah. And that's |
|
| 108:39 | . Whatever it takes to get So um one second is 1000 |
|
| 108:44 | So 10000.1 of that, 1/10 of is 100. So this these division |
|
| 108:49 | and incidentally you just have to practice . It's, it's fine, just |
|
| 108:54 | it. You actually can't get around . You have to do this. |
|
| 108:59 | have to, you you have to facility in it and that I do |
|
| 109:04 | same thing, I think. ok. There's one second, |
|
| 109:12 | 10. I've got 10 divisions in second. These are all 100 milliseconds |
|
| 109:17 | .1.1 seconds. So this is 100 . And so I say, |
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| 109:23 | it's still gross. Well, I'm have to try to count these cycles |
|
| 109:28 | I would say how many cycles are in 100 milliseconds? Because like you're |
|
| 109:33 | , it's too small. So even a little tricky here. But I'm |
|
| 109:38 | go say 1, 23, I see that four. So there's something |
|
| 109:47 | Say four or 5 cycles per 100 . So for say four cycles per |
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| 110:03 | milliseconds, that's four cycles in 40.1 , that's 40 cycles in one |
|
| 110:08 | So 40 cycles in one second is Hertz. OK? That makes |
|
| 110:14 | So I'm just gonna count more of . And it's, you do that |
|
| 110:17 | the time because for example, first of all, I don't even |
|
| 110:25 | what this scale is because I didn't it out. But this is probably |
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| 110:32 | milliseconds. No, it's probably It's probably more than that. |
|
| 110:48 | it's not obvious. This might be milliseconds but not obvious. But here |
|
| 110:52 | go, here's practice for you. , what I'm gonna ask you to |
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| 111:01 | here is to calculate the dominant frequency this guy. Ok, So that |
|
| 111:33 | 95 2468. Sorry, Sorry. scale is just weird. So that's |
|
| 112:46 | . That is about so this one . So that takes about a little |
|
| 113:07 | than social community area she talking Mhm. 64932 cheese. I got |
|
| 113:57 | about 50 about, Oh, that's milliseconds. OK. I got |
|
| 114:14 | So that's just showing what the scale . Oh, I guess I could |
|
| 114:25 | just done it like that. That sense. So you can see here's |
|
| 114:31 | scale we're going .9, 6.98, 2nd. So the difference between this |
|
| 114:52 | is just a little bit funky. , I had that right before. |
|
| 114:56 | shouldn't have changed them. I was to like pick Like, oh, |
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| 116:07 | like 97 80 or something. I , I didn't realize I could just |
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| 116:12 | , oh, like this is 10 . That would be so much |
|
| 116:17 | Well, you can just, just the lines up. All you need |
|
| 116:23 | one cycle. So we're just trying say how long is one cycle. |
|
| 116:28 | about Like you have like 25-30. . So I can see that this |
|
| 116:38 | cycle is almost 20 milliseconds. This 20 milliseconds. So I can see |
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| 116:43 | that half a cycle is just slightly than 20 milliseconds. So that's a |
|
| 116:49 | . And then I picked this Yes. First part is almost halfway |
|
| 116:57 | these two. So that's at This is at .98. So how |
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| 117:06 | milliseconds? 30 or 30 milliseconds? so one on 1/30 milliseconds or one |
|
| 117:18 | ? 10.3 seconds is 33. So this dominant frequency is 33 |
|
| 117:29 | And if I put 33 hertz on side, I would guess that I'm |
|
| 117:34 | from something like zero to around 70 as my total bandwidth that's in that |
|
| 117:48 | . OK. So that's any Just take one cycle peak to |
|
| 117:55 | This is a bit harder because we're from a zero crossing to another zero |
|
| 118:00 | . But You know, I, could have said, OK. Uh |
|
| 118:06 | .95, here is one oh there's 123, maybe four cycles and |
|
| 118:22 | amount of time and then just divide . But in this case, I've |
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| 118:26 | one cycle takes about from 10.95 to . That's 0.3 seconds, 3, |
|
| 118:34 | mil milliseconds, 1/30 milliseconds is 33 . So immediately when you look at |
|
| 118:40 | , you say, yeah, that's 30 Hertz. Does that make |
|
| 118:43 | Yes, seism mix is normally around 30 40. Our band that we |
|
| 118:48 | deal with is about 100 Hertz to a 10 Hz. That's typically the |
|
| 118:54 | seismic band. We get a little higher values in V S P because |
|
| 118:59 | don't have to go back to the game. So that's how to compute |
|
| 119:05 | dominant period. Just the time one that is the dominant frequency. |
|
| 119:13 | OK. Let's, uh, let's take 10 Stephanie and then, um |
|
| 119:18 | come back and wrap up before OK. OK. Great. We |
|
| 119:28 | our heroes dangling with this picking And OK, so we got that |
|
| 119:45 | can push this a little bit It's probably a bit more detailed than |
|
| 119:48 | need to know. But um right , but if there's noise in |
|
| 119:53 | then that means it's harder, it's to do this pick exactly. And |
|
| 119:58 | we can estimate the noise and we estimate it by the amplitude of the |
|
| 120:02 | here versus the amplitude of the signal . And that gives us signal over |
|
| 120:09 | . And, and we usually use kind of idea of signal to noise |
|
| 120:15 | all different circuits, acoustics, everything, electronics. And then knowing |
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| 120:22 | that just says how much fuzziness is here. So that means how closely |
|
| 120:26 | I pick it? And then we get a, a picking error and |
|
| 120:31 | this little calculation, we get that can probably pick this within one little |
|
| 120:39 | because this is very, very clean . There's almost no noise here. |
|
| 120:43 | then boom, I get my signal it comes through. So we can |
|
| 120:48 | when is the onset of energy And in a causal system like normal |
|
| 120:55 | system, that's exactly when the energy arrive with a vibrating source. This |
|
| 121:02 | a uh a whack, a hammer or something with a vibrating source, |
|
| 121:06 | correlate the signals. So we get symmetric arrival, a zero phase |
|
| 121:12 | that's not causal, that's the So we don't pick the first energy |
|
| 121:16 | pick the maximum. So there are ways to pick whether I'm dealing with |
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| 121:21 | causal, a physical, a standard with distance uh no processing or if |
|
| 121:28 | dealing with uh a vir size sweep I actually process and it gives me |
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| 121:35 | a symmetric output but the maximum of symmetric is the real arrival time. |
|
| 121:41 | then it's got wiggles on either that's just from the cross correlation. |
|
| 121:46 | we pick the first break differently. physics impulsive sign uh Saurus boom first |
|
| 121:55 | a vir size. So we're gonna the maximum. Now I can get |
|
| 122:07 | little bit more complicated. The um we talked about as the energy goes |
|
| 122:11 | the earth, it's spreading out. I've got one amount of energy that |
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| 122:16 | and then it's propagating and it's spreading and the energy decrease is just like |
|
| 122:22 | surface area of a balloon. The is spreading out and it's approximately a |
|
| 122:30 | of one over R. So just a balloon, the uh the energy |
|
| 122:35 | decreasing accordingly. OK. That's a more than we need to know. |
|
| 122:48 | We talked about this, that the is going down it's getting smaller as |
|
| 122:51 | spreads out. And then we've got reflection coefficient that returns some of the |
|
| 122:56 | back to the surface and then it out. So those are all the |
|
| 123:00 | factors that are influencing the amplitude. . Now, this is what I |
|
| 123:09 | talking about with uh a Viber size . And you can see that this |
|
| 123:18 | of has an emergent signal with a of noise and then it gets kind |
|
| 123:22 | symmetric and this is a Vibra size that's been cross correlated. So what |
|
| 123:32 | that mean? Well, we can that instead of just a um a |
|
| 123:39 | pulse going into the earth, we've got A whole sweep and the |
|
| 123:44 | might be 10 seconds itself. So going and that whole sweep or a |
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| 123:53 | of frequencies that whole chirp is going the earth. So when that |
|
| 123:58 | it reflects this whole set of So I, I don't want to |
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| 124:08 | all those reverberations, I wanted to just a spike. So the way |
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| 124:13 | get rid of all the reverberations is to take the sweep that I programmed |
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| 124:19 | to the vibe and then cross correlate with the whole return signal. So |
|
| 124:27 | I'm sweeping for 10 seconds, I'm be listening, my receivers are gonna |
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| 124:34 | on, I'm gonna be listening that sweep. Plus I'm gonna add a |
|
| 124:39 | of seconds for that whole sweep to down and come back so if my |
|
| 124:45 | is 10 seconds, that's got all down. If I want my record |
|
| 124:49 | be two seconds long, then I've to record for two more seconds. |
|
| 124:56 | if my vibe sweep is 10 seconds I want a two second record And |
|
| 125:01 | got to listen for 12 seconds. that's an important concept just in the |
|
| 125:23 | the surface seismic that shot that uses vibe. Does this, you record |
|
| 125:29 | time of the whole suite? Plus much section you really wanted? So |
|
| 125:37 | , if I was shooting dynamite and wanted to see down to two seconds |
|
| 125:41 | back, I would record for two . But that means that again, |
|
| 125:49 | reflector down here, it takes a to go down to it a second |
|
| 125:52 | come back. So my section is seconds long. Now with a |
|
| 126:00 | effectively, the energy still takes a to go down and a second to |
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| 126:04 | back. But my sweep is 10 long. So I've got energy coming |
|
| 126:12 | at zero, da da, da, da da. The sweep |
|
| 126:15 | at 10 seconds. That last piece down and back. So the last |
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| 126:20 | of the vibe sweep comes in at seconds. So with the Vibe, |
|
| 126:27 | have to record not two seconds, have to record 12 seconds. Then |
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| 126:36 | got that 12 2nd record and I'm take the Vibe Suite which is 10 |
|
| 126:41 | long and just correlate multiply multiply multiply shift, multiply multiply multiply output |
|
| 126:50 | And I can do that whole thing seconds down to 12 seconds. And |
|
| 126:55 | my correlation section is two seconds long that's the correlated sweep and that should |
|
| 127:05 | like dynamite. But whereas dynamite is sharp arrival, the the output vibe |
|
| 127:20 | is actually a correlation of the sweep itself called the auto correlation. And |
|
| 127:27 | is a symmetric looking um wavelength and zero time of that wavelet is at |
|
| 127:41 | maximum What's called zero phase or the peak. That's the correlation peak. |
|
| 127:48 | at the time of the arrival. it's called not causal or not physical |
|
| 127:57 | that the output arrival is the correlation the sweep with the response. So |
|
| 128:08 | all intents and purposes, it looks regular seismic. But this energy |
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| 128:13 | you can see that that's a little before the actual arrival time. The |
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| 128:20 | time is this big peak right That's the zero Phase Correlation Peak. |
|
| 128:28 | I shot this with dynamite, I see very similar data but it would |
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| 128:41 | down here flat. And then all a sudden there'd be a spike here |
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| 128:46 | that would be it with the, Viber size. I've got this big |
|
| 128:51 | symmetric wavelet you can see down here , here's uh the wavelet dynamite. |
|
| 128:59 | just have this guy fiber lets have guy. Well, that's not any |
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| 129:12 | big deal I can apply a filter make this look like dynamite, but |
|
| 129:21 | just interpret it this way. So I'm gonna pick this, I'm gonna |
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| 129:25 | this zero phase peak. This is uh the, the place where the |
|
| 129:30 | actually came in. Now, let's the same thing. Please tell me |
|
| 129:38 | the dominant frequency here? Calculate the frequency maybe at the surface. And |
|
| 129:46 | can see the the divine line, is milliseconds. So I get 0 |
|
| 129:52 | 1000 milliseconds. So 0 to 1 . And we're just looking for the |
|
| 129:58 | dominant frequency here again. Mhm I about 11 hertz Because down at the |
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| 131:07 | it's a little less than 100. I did like 90 Since the 4 |
|
| 131:13 | 500. Um So then I did over 0.09 seconds. Um I got |
|
| 131:23 | hurts. OK. So this is , uh a little tricky. So |
|
| 131:30 | looking down here, I see a here. Excuse me, that and |
|
| 131:35 | trough here. Oh, it would there. OK? I was going |
|
| 131:41 | the end of that trough. I I was getting both. Well, |
|
| 131:46 | gotta get one cycle. However you it, it's gotta be just one |
|
| 131:58 | because I was getting like right there the end because I was going off |
|
| 132:01 | like this picture where it like it both like it's the Whole thing. |
|
| 132:11 | that's why I grabbed that whole So it's like closer to the |
|
| 132:18 | Well, however you do it, could be trough to trough, peak |
|
| 132:21 | peak zero crossing the second zero However you do, it is all |
|
| 132:27 | , but you just have to have cycle. So it's a little bit |
|
| 132:35 | because this is not a perfect sinus . This is real data and it's |
|
| 132:38 | bad plot of real data, But like maybe closer to 4:50. Um |
|
| 132:49 | , so I I'm not saying you're , I'm just checking to make sure |
|
| 132:52 | you know what you're doing. Yeah. So here I would |
|
| 133:01 | there's a zero, there's a minimum at about 400 there's another minimum here |
|
| 133:07 | about 4 50 milliseconds. So among , I'm going to say that's about |
|
| 133:17 | milliseconds. OK? And at least little guy, so 50 milliseconds is |
|
| 133:26 | many hertz? It's uh uh about . Yeah. So that looks to |
|
| 133:36 | around 20 hertz. Now, that's one little measurement. Uh maybe I'd |
|
| 133:39 | up a little bit more and I , this is really hard data to |
|
| 133:50 | . So maybe I'm gonna try to some place that has a bunch of |
|
| 133:54 | . So say up here, that's right? 300 milliseconds, There's a |
|
| 134:04 | , another peak, another peak, peak. So that's 300, |
|
| 134:16 | 5, 6. So I've got cycles, 700 to where did I |
|
| 134:24 | ? 306 cycles and 400 milliseconds. say six cycles in around 500 milliseconds |
|
| 134:36 | to make it easy. That's 12 . Ok. So as a guess |
|
| 134:43 | gonna say that it's, it's something 12, 15, 20 Hz somewhere |
|
| 134:51 | there. Now we go and look our, that's just our, our |
|
| 134:59 | gas kind of excuse me. So go and look at this now and |
|
| 135:07 | the full Frequency analysis, the four spectrum and sure enough, the maximum |
|
| 135:15 | Somewhere around 13, 14. But got this whole area that's somewhere around |
|
| 135:22 | hertz. So in the real world the very, very top this |
|
| 135:29 | So in that case, we could here's a zero crossing 1, |
|
| 135:35 | 3, 4, five, 5 , 5.5 over around 400 milliseconds. |
|
| 135:48 | that's pretty close to say six, 15 Hertz. And so we look |
|
| 135:55 | the ferrier analysis, there's 10, 20 so boom 15 Hertz. So |
|
| 136:03 | dominant period, the dominant frequency calculation pretty well. So here's the real |
|
| 136:11 | spectrum. Now you can see in very top. First of all, |
|
| 136:17 | , it's in, it's in a band of frequencies. Where do you |
|
| 136:21 | most of the frequencies in what, what range um Like from, are |
|
| 136:34 | talking about like from 10 to No, what's the frequency range |
|
| 136:43 | Oh You're talking about the whole So like the turn to 80. |
|
| 136:49 | . OK. I thought you meant because all that noise right there. |
|
| 136:52 | was like maybe OK for the whole . Yeah. 10-80. Yeah. |
|
| 136:55 | most of the energy, this is amplitude. Again, Most of the |
|
| 137:00 | is in 10 To 80 Hz. . So we said that this is |
|
| 137:07 | vibrator. So what is the sweet of the vibe? It's sweeping across |
|
| 137:20 | Hz. So the vibe um just the field is gonna be sweeping from |
|
| 137:33 | Hertz, then up to 80 Hertz going into the earth and we monitor |
|
| 137:38 | . And sure enough, that's exactly we see. This is the signature |
|
| 137:42 | a vibe though because you can see very well defined inside two ranges. |
|
| 137:46 | I had dynamite or something, we're gonna see that perfect band unless it's |
|
| 137:50 | filtered. So we know that something we see something that's definitive and, |
|
| 137:54 | constrained something mechanical is going on and it is, that's the sweep range |
|
| 138:00 | the vibrating source. So this is , the kind of spectrum. |
|
| 138:04 | there's a lot of stuff happening in because the sweep isn't perfect. We've |
|
| 138:09 | absorption, we've got conversion to there's all kinds of stuff going |
|
| 138:15 | but generally the vibe would be trying sweep with a flat spectrum across |
|
| 138:23 | It is a mechanical source. It's have resonances, it's gonna have problems |
|
| 138:26 | the near surface, maybe it's a mucky in that shot point, |
|
| 138:30 | So it's sweeping, it's not inputting perfect amount but it's doing the best |
|
| 138:38 | can. So this is some all of bad data. So that's bad |
|
| 138:53 | . Now, we also had uh fiber optic data from West Texas. |
|
| 138:58 | was again very, very noisy This is in the early days of |
|
| 139:03 | systems, distribute acoustic fiber optic So with a fiber optic sensor, |
|
| 139:09 | just a fiber, that's it. then you shoot a laser down the |
|
| 139:14 | and they're all little impurities in the and it reflects just a little bit |
|
| 139:19 | light in that fiber. So you imagine we shoot a laser down, |
|
| 139:29 | laser goes down and it's reflecting back little bit of light that's just varying |
|
| 139:35 | the slight imperfections in that fiber. . So we recorded that reflected laser |
|
| 139:43 | . And then you can imagine suppose stretch the fiber and now we shoot |
|
| 139:49 | light back down in the game. can you imagine happens to the |
|
| 139:55 | What do we get back from that being shot down the, the stretched |
|
| 140:05 | just like like the reflection or Yeah, it is. But what |
|
| 140:10 | does it have compared to the uns fiber? Oh um Only a little |
|
| 140:24 | stretched. So then it would be . I'm not sure. So what |
|
| 140:33 | is that? And if you were you might get a Nobel Prize if |
|
| 140:37 | jumped to the answer. Hm. You can imagine that, say I've |
|
| 140:44 | the fiber horizontally. Right now, shine the laser down. It gives |
|
| 140:48 | this weak set of reflections from little of the fiber. So it say |
|
| 140:53 | reflections sort of look like this, points. Then I stretched the fiber |
|
| 140:58 | I shine the laser down of the . You can imagine that we get |
|
| 141:02 | same set of points back, but stretched. And so the the resultant |
|
| 141:11 | light has these little reflections. The is the same, but the pattern |
|
| 141:18 | stretched stretch, the fiber stretch, pattern. So that fiber stretch has |
|
| 141:32 | pattern and that pattern is coming back time. And that pattern has been |
|
| 141:39 | a little bit, which means that slightly lower frequency than the uns stretched |
|
| 141:47 | . So I compare just like we've here, I compare the dominant frequency |
|
| 141:54 | the stretched fiber response, the dominant of the uns stretched fiber. There's |
|
| 142:01 | , a little little frequency shift. you can imagine that frequency shift is |
|
| 142:07 | to the amount of stretch. So have a mapping from the slight frequency |
|
| 142:29 | at that point to the amount of at that point. Now, the |
|
| 142:34 | can fire really fast like billions of a second. So I'm gonna sample |
|
| 142:46 | we're stretching the fiber like this, could shoot the laser down and it |
|
| 142:54 | the pattern at this point and then stretch it at this point and then |
|
| 142:58 | this point and then this point and this point and the laser can sample |
|
| 143:03 | very fast. And so it outputs what a seism grab. So that's |
|
| 143:14 | the way a fiber optic sensor works what's called a da acid distributed acoustic |
|
| 143:20 | in the system. And so what can do is we can make that |
|
| 143:24 | all the way along the fiber. when a wave hits the fiber, |
|
| 143:30 | stretches it and I'm interrogating or getting response of that fiber with my fast |
|
| 143:35 | laser, the lasers can shoot way , way faster than seismic waves mechanically |
|
| 143:40 | because we're talking about mechanical waves Oscillated like 50 cycles per second. |
|
| 143:48 | that's infinite for a laser. A can sample that millions of times in |
|
| 143:54 | second. So it's no problem for laser to reconstruct seismic motion. Now |
|
| 144:14 | makes the fiber interesting is that we the fiber down the whole well, |
|
| 144:22 | every place on the fiber can be to give an output. So in |
|
| 144:29 | , we need to do this correlation I just talked across a certain area |
|
| 144:33 | I need a certain number of points correlate and that's called the gauge |
|
| 144:39 | And Typically it's gonna be something like m. But I can now take |
|
| 144:48 | fiber that's 10,000 m long and reconstruct motion all along that fiber and output |
|
| 144:55 | make it look like a very, densely sampled BS B. The applications |
|
| 145:06 | this are enormous because all of our and country and oceans have fiber optic |
|
| 145:15 | on them. So the original purpose the fiber was not to look at |
|
| 145:23 | reflected energy. It was to look just straight the digital transmission. Like |
|
| 145:30 | now with what we're doing, there's wire, there's hot fiber between me |
|
| 145:39 | you, lots of different segments of fiber that's transmitting this signal. So |
|
| 145:45 | of this signal is probably going along fiber. So that's straight transmission. |
|
| 145:50 | got little ones and zeros that are along. And there was input at |
|
| 145:54 | end, my camera is sampling. converting that to a digital stream that's |
|
| 146:01 | through fiber and wireless to yours. that was all transmission, which was |
|
| 146:10 | . But the discovery was that guess ? There are losses in that fiber |
|
| 146:15 | because the light prop getting along in of those losses is because there's slave |
|
| 146:21 | in the fiber that are reflecting some the signal back. But nobody cared |
|
| 146:28 | that was just a problem that was decreasing my transmission rates. But it |
|
| 146:38 | out if you put a receiver, just a transmitter, but if you |
|
| 146:41 | a receiver to look at the reflected , you're getting the strain of that |
|
| 146:46 | fiber and the strain is vibrations along fiber that we can record. So |
|
| 146:56 | these fibers and they thousands of kilometers over Houston all over the campus. |
|
| 147:04 | hundreds of fibers that are going to airport all over the place, lots |
|
| 147:08 | fibers are laid on the ocean, fibers going to Europe to everywhere. |
|
| 147:17 | all of those fibers, if you A reflection receiver on one end and |
|
| 147:25 | can use them all as geophones. that's what people are doing, that's |
|
| 147:33 | , it's revolutionizing everything. And so lot of the installations now are are |
|
| 147:38 | with fiber, not just for but for temperature strain, all kinds |
|
| 147:42 | stuff. And this was data from of the early interrogator boxes. This |
|
| 147:51 | um early data, but even the data you can see in A V |
|
| 147:56 | P, we've got our downgoing P , there's just a lot of noise |
|
| 147:59 | it but it worked. So this one of the earlier tests with a |
|
| 148:06 | from a company called tech. That has since been bought, I think |
|
| 148:14 | um by B P. So there's other things that are really basic um |
|
| 148:33 | processing values that you might remember if have random noise and we just take |
|
| 148:41 | signal that has noise in it and take a measurement and then we take |
|
| 148:47 | signal, the same signal of noise it and keep on adding them together |
|
| 148:51 | stacking, then the random noise tends cancel and the signal tends to |
|
| 149:01 | So this is this just the point averaging. So again, yeah, |
|
| 149:11 | I take a shot and get then take another shot and then another |
|
| 149:16 | and then another shot, same same receivers and just keep on taking |
|
| 149:22 | exactly the same geometry that's called a stack. Or it's just a |
|
| 149:29 | And if I keep on stacking that , sooner or later the signal, |
|
| 149:33 | , the coherent, the consistent, same part is gonna get bigger and |
|
| 149:40 | . And if the noise is then it gets bigger by the root |
|
| 149:46 | N where N is the number of . So if I take that data |
|
| 149:55 | I record the same experiment nine times signal to noise ratio should improve by |
|
| 150:07 | . So the root of the number stacks. So in this case, |
|
| 150:37 | they, They stack 20 shots and if I estimate the signal by the |
|
| 150:49 | of this downgoing wave and then the by the amplitude of stuff before the |
|
| 150:56 | arrives. So the noise is out before the signal and then there's the |
|
| 151:01 | , I take the amplitude of this over the amplitude of the signal. |
|
| 151:07 | as I continue to stack And I nine times it, the signal that |
|
| 151:13 | should increase by three. And if stack 25 times the signal that I |
|
| 151:18 | increase by five. So in this , they stack 20 times. So |
|
| 151:22 | theory, the signal device should have by 4.5, Our estimate is the |
|
| 151:28 | that increased by around four. So enough for government work. That just |
|
| 151:35 | like that was, that was about . So just in general, getting |
|
| 151:48 | little bit more deeply into this, I looked at the spectrum and we've |
|
| 151:53 | looking at some of these spectrum, frequency content of the source here, |
|
| 152:00 | going to spherical spread. So one R, one over Z as we |
|
| 152:04 | down in depth, the deeper I , the farther it spreads. And |
|
| 152:08 | the amplitude is gonna decrease by one how far it's propagated. Then we |
|
| 152:28 | that a little bit of the signal lost as it goes down because some |
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| 152:32 | it's returned to the earth, that's reflection that we're interested in. So |
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| 152:36 | amount I'm getting at a certain depth multiplied by the transmission, how much |
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| 152:41 | being transmitted, then you know that you take just a ruler or |
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| 152:56 | and if you bend the ruler back forth, sooner or later it starts |
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| 153:02 | get hot, right? And if keep on bending it back and |
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| 153:06 | far enough it's going to break. with all materials, as we oscillate |
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| 153:19 | , a little bit of that energy into heat, just like bending something |
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| 153:26 | and forth. A little bit of going into the heat because all materials |
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| 153:30 | slightly imperfect, they're slightly non So when our waves are going through |
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| 153:39 | material, they're oscillating the material, material is not perfectly elastic. So |
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| 153:45 | little bit of that elastic wave energy converted to heat. And a big |
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| 153:54 | to look at that is the farther go, the more is converted to |
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| 153:58 | that's called the attenuation coefficient. So also decreases the amplitude. So in |
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| 154:14 | end, we take the amplitude that put into the earth as it goes |
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| 154:20 | to some depth, it spreads it suffers transmission loss and some of |
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| 154:28 | converted to heat. So that by time I'm at some depth, the |
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| 154:35 | are reduced. And so when I'm at a depth, I imagine that |
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| 154:40 | I receive down here at depth is you started with at the surface, |
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| 154:47 | transmission loss and spreads out. So just a little equation that predicts how |
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| 154:54 | of each frequency should be left at depths. And of course, we're |
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| 155:01 | use that equation to find out the coefficient or how much gets converted to |
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| 155:09 | . And this is called the spectral method. So I start off with |
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| 155:13 | equation that says this is what you off with at the surface. Here's |
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| 155:17 | you attenuated it. Here's what you up with the depth. So if |
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| 155:23 | know what I put into the surface I measure something at depth like we |
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| 155:30 | did in that, in all these SPS, then that's equal to this |
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| 155:37 | . I can take the logarithm of sides. That's the logarithm of the |
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| 155:45 | at depth. The spectrum at the and that's equal to this. And |
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| 155:51 | can plot this logarithmic ratio against And the slope of the result gives |
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| 156:04 | a measure of the attenuation coefficient. that's how I do it. That's |
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| 156:09 | it's called the spectral ratio. So is a spectrum, this is a |
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| 156:13 | ratio, the ratio of the two , that's our spectral ratio. And |
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| 156:17 | that's why it's called the spectra racial . And when we extract the waves |
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| 156:23 | into depth, this is the first going in depth. It's just been |
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| 156:31 | . You can see that the amplitude decreasing and then you may see that |
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| 156:36 | getting obviously aptitude is decreasing, but not as sharp anymore. It's spreading |
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| 156:44 | a little bit. So when the spreads out a little bit, what |
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| 156:51 | that say about our period and our frequency, what do you think unless |
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| 157:00 | spreads out, then it'll be, have a higher frequency. So if |
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| 157:10 | like will no, it'll be Yeah, that's what I'm what we're |
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| 157:21 | with spreading out means that it's getting . Oh OK. If it's getting |
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| 157:27 | , that means that the period is . If the period is increasing, |
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| 157:35 | one over the period, the frequency gruesome. Correct? OK. So |
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| 157:51 | we go deeper, we're going from frequencies to low frequencies and that is |
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| 157:57 | measure of how much attenuation there And so we can make a log |
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| 158:02 | it how attenuated are the sediments and not too precise or highly resolved, |
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| 158:08 | we can make a log of And so we do so we can |
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| 158:13 | the um the, the sweep So I was sweeping say from 20 |
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| 158:20 | to 100 and 20 Hertz and that's red line, that's the theoretical |
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| 158:26 | Then in my V S P I a receiver that would stay down a |
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| 158:29 | 100 m. This is what I the blue line in the spectrum. |
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| 158:34 | then I look at the deepest receiver this is what I received. So |
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| 158:39 | losing frequency, then I can take ratio of those spectra. Here's a |
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| 158:46 | , I get the line and that me a measurement of Q or attenuation |
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| 158:53 | . And so we can make a of that. So that's another |
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| 159:08 | So we're walking through just what I'm get from these first arrivals time to |
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| 159:13 | velocity. And now attenuation, this a little bit specific. But |
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| 159:24 | in the wave propagation world, if have attenuation, it means that different |
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| 159:35 | propagated slightly different velocities. So what means is that 10,000 hertz waves in |
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| 159:57 | earth Their velocity is slightly different than 50 Hz wave. And that's part |
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| 160:03 | why the integrated sonic or the subsonic quite agree with the seismic sonic waves |
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| 160:11 | just a little bit faster. They're wrong, they just travel at different |
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| 160:18 | . No. Um This is kind a second order effect to first order |
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| 160:27 | waves propagate all of the same velocity of frequency. If the earth is |
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| 160:32 | bit attenuated, then usually we have 123, 4% difference in values. |
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| 160:41 | it's not too much usually, but a little bit. And if we're |
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| 160:45 | careful, we have to take care it. And um you, we |
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| 160:50 | go into this more, this, is a little bit more detailed. |
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| 160:53 | um if we know what the difference between the checks shot time and the |
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| 160:59 | sonic time, then that can be to calculate Q or vice versa. |
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| 161:11 | . So I'm not, that's, why there is some of the difference |
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| 161:17 | velocities. What does it mean? just goes to support why we calibrate |
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| 161:23 | sonic logs. So I said before the sonic velocities when we add them |
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| 161:29 | together is slightly different, we found that that difference is kind of |
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| 161:35 | And if we want to know why based on attenuation, if we don't |
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| 161:40 | about why, but I just want fix it, then I just alter |
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| 161:45 | sonic velocities a little bit by a percent. So they agree with the |
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| 161:49 | ones. And when we do and then we generate a synthetic seism |
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| 161:56 | , we find that it agrees a better. So here's a synthetic seism |
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| 162:07 | just created with the sonic log and correlated with real surface seismic and the |
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| 162:19 | isn't quite right. You can see I stretched the sonic times to agree |
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| 162:28 | checks shot times the real seismic. we see that the correlation is quite |
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| 162:36 | . So it's just nudging a little but we do it and now we |
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| 162:40 | it and it makes everything better. we calibrate our sonic logs and we |
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| 162:49 | look at all these different uh cases uh where after the calibration it makes |
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| 162:57 | just work a little bit better. . Great. Well, that's uh |
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| 163:05 | a bunch of stuff. We're gonna on with the um with more of |
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| 163:13 | analysis of how we process this But at this stage now we've extracted |
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| 163:18 | much what we need out of the break of the V S P time |
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| 163:23 | adapt interval velocity Q. And now gonna start to further process the uh |
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| 163:29 | data. Great. OK. let's take an hour for lunch. |
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| 163:39 | Uh run around the block and uh see you at about 1 10. |
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| 163:46 | . Sounds good. Thank you. |
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