| 00:00 | I can't, as before I can't half of you. And Utah right |
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| 00:10 | is rescinding it. And what it , it's the final quiz. |
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| 00:16 | it's, it's a study guide or to 75% of the final is gonna |
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| 00:25 | taken from that study guide, similar of problems. Uh And I've been |
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| 00:36 | , how am I gonna get the ? You know, this is the |
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| 00:41 | time I've had so many folks away the, the quiz. So I |
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| 00:48 | I'd do the same as some of other professors do and give you the |
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| 00:53 | in the morning and you have to it in by midnight. I assume |
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| 00:58 | of you have the ability to print then be it because it's gonna be |
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| 01:06 | difficult. I think it is difficult draw on graphs that I send you |
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| 01:12 | it looking like it came off with etro sketch. Uh Does anybody have |
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| 01:22 | and be able to print the quiz then scan it and email it back |
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| 01:28 | me? Or, or you could ahead just physically bring it down to |
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| 01:36 | university and give it to yo, mean, that's that's another option as |
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| 01:44 | preferred because actually I usually have to out all the, uh, PDF |
|
| 01:52 | . Did I get, is that with the class in here? What |
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| 01:58 | just said that you'd be given a about nine in the morning and then |
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| 02:06 | had to return it by midnight or o'clock, something like that. |
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| 02:14 | I said, I guess midnight because folks work during the day and makes |
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| 02:19 | difficult. Ok. Um, are any questions or comments? Yes. |
|
| 02:28 | What about the other 25 to 50% the final? That's not on the |
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| 02:31 | exam. What about it? Do want me to tell you the answers |
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| 02:37 | it? Well, I'll tell I'll tell you the answers now. |
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| 02:40 | got to figure out what questions they to. Ok. Yes. |
|
| 02:43 | No, no. Ok. Ah, the other 25% is just |
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| 02:53 | choice over all the material that I've given. Mhm. Any questions |
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| 03:02 | I can answer? Um, are gonna have to be using, like |
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| 03:10 | any difficult math equations or I'm assuming will be some math, but I |
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| 03:15 | know there are some of the equations seen are, are pretty intensive. |
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| 03:20 | we gonna be doing any math using or more? So, some of |
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| 03:25 | more straightforward equations it's going to I'll tell you on this quiz that |
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| 03:30 | sending you. I went, there's of them that make up 50% of |
|
| 03:36 | quiz and there'll be just be different . What I will give you is |
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| 03:44 | gonna give you the velocity density of sand and shell and it might be |
|
| 03:57 | filled the sand. And I'm going ask you to draw the avo |
|
| 04:04 | Z response. That's a graph R plus and minus for the what? |
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| 04:12 | for the gas charged, you're gonna to be able to use, incorporate |
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| 04:21 | saturation in there because you're gonna have be able to compute a density gas |
|
| 04:29 | then fill with Brian. So it's lot of uh math, but it's |
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| 04:38 | calculator math. And I mentioned to make sure you show your math cause |
|
| 04:49 | you give me an answer and it's , I, I can't get |
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| 04:53 | I can't give any credit. But you show me what you're doing and |
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| 04:57 | wrong, then I can give you credit. And also anything that depends |
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| 05:04 | that answer, I can give you credit to going forward. Just go |
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| 05:10 | and uh compute to find out what uh see what the answer should |
|
| 05:18 | Any other comments or questions, you're able to scan a paper to get |
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| 05:27 | into a total PDF. OK. another one. I absolutely do not |
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| 05:38 | any PDF S that are single A PDF better be all put together |
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| 05:46 | one. So because I print or you have them, if you have |
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| 05:57 | seven or eight pages. I'm not put it together because I don't know |
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| 06:04 | I assume you'd be much younger than am. If you know how, |
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| 06:08 | you don't find your eight year old , they'll do it for you. |
|
| 06:17 | ? Any other questions about the Ok. Now we, we don't |
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| 06:27 | everything. I intentionally I have like last they are parts of my lecture |
|
| 06:38 | you don't need me to say here's my comments and what's coming |
|
| 06:43 | the future. That's not really I think. But we had to |
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| 06:47 | the course somehow. So there's a sections. I do skip when you |
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| 07:00 | those of you, when you get study guide. Very first question is |
|
| 07:06 | be a little questionable on how, do you know this? It's gonna |
|
| 07:14 | you about 20 different answers such as a vo in 1990 or was the |
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| 07:30 | to recognize what a class one a was and publish excellent results. And |
|
| 07:37 | be asked who's the author? And get, you'll be given a list |
|
| 07:42 | 20 names and you, you have associate those names with the comments that |
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| 07:49 | made. No, here's the bad . You haven't been assigned those |
|
| 07:58 | but theyre in your PDF file. so I'll try not to give too |
|
| 08:07 | you go ever rip, but the class reads all those papers and |
|
| 08:16 | the way your schedule is set you actually have, you have six |
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| 08:28 | on each weekend, three hours is classes and I used to sign an |
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| 08:36 | per class minimum. And so that up, we start seeing how many |
|
| 08:45 | you have to take. Usually they 3040 articles. You only get one |
|
| 08:52 | two. It'll be tough. I a question. Uh, you were |
|
| 09:04 | there's some of the end lecture material you don't quite get to. |
|
| 09:09 | are you saying that's still game to all that? That is not game |
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| 09:14 | the, for instance, I'm not question you on uh section, let's |
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| 09:27 | . Uh Section 62 wave equation and uh that starts getting into things such |
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| 09:51 | taking a derivative of an equation and the derivative to make predictions of what |
|
| 09:59 | error is and then modeling that error forward. It's a, that's one |
|
| 10:08 | those articles, items that you wanna behind closed doors. You heard that |
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| 10:16 | story, didn't you? Something you're to be do behind closed doors? |
|
| 10:23 | wife does not allow me to write on the board anymore. I can't |
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| 10:29 | equations on the blackboard anymore. And says you're too old for that. |
|
| 10:36 | said that's like sex. You do behind closed doors in case you make |
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| 10:42 | mistake, nobody laughs at you, , you're too damn old. |
|
| 10:47 | So a lot of these like it's something you wanna do behind closed |
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| 10:55 | because it requires a lot of concentration rereading articles several times. Anything else |
|
| 11:06 | have. Ok. If not, see what we can do. Did |
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| 11:21 | find that, that article, the email just, just posted on |
|
| 11:30 | Ok, let's see. Now how I get, how do I get |
|
| 11:49 | to them? Uh Let's see. me guess. Zoom. Now he |
|
| 11:56 | first the the Yeah, that yes go to Zoom and click the window |
|
| 12:06 | and chill. Zoo and he shared . Sure. It's the green button |
|
| 12:15 | select screen two and share. folks. Can you see my screen |
|
| 12:25 | you can't see my screen? Don't anything. We can see your |
|
| 12:32 | Ok, thank you. What does mean? Then should be a closed |
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| 13:00 | for those at home and those you know, I'd even challenge you |
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| 13:12 | you, I'd even challenge you to at and still you still get it |
|
| 13:17 | . Oh, I'm a, that's arrogant. Uh Yeah. Ok. |
|
| 15:21 | . Oh. Oh God, I realize that creamer stuff turns it |
|
| 16:53 | Yeah. Yeah, it makes Oh, if I stirred it, |
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| 17:03 | it goes away. Oh, that's . That's right. You're right. |
|
| 17:26 | my eyes closed. Anybody watch the Friday Night Lights, West Texas football |
|
| 17:42 | school when I was in high I never, I, I don't |
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| 17:48 | those dramatic scenes, you know, and Robbie. Well, the only |
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| 18:25 | that got correct, a certain portion this exam. Oh, put your |
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| 18:42 | on it. Ok? I assume all send it in already. Not |
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| 18:56 | . I am missing right. Almost . Ok, let's send a |
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| 19:49 | That's all 1. 22. I accepting. You have 30 seconds. |
|
| 20:05 | ? Let's see what we can I'm gonna need some help here |
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| 20:12 | You're done. I'm I'm gonna get of this mode. I guess I |
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| 20:16 | do it here. Ok? We off with class one and it goes |
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| 20:24 | like that. We start off class and it could be on either side |
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| 20:31 | this angle here. I mean, side of, of the zero line |
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| 20:42 | then the class three and actually the two, let me do that again |
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| 20:56 | be down here this year. Does notice something? It might be different |
|
| 21:09 | what you put up? What? ? Well, class two also supposed |
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| 21:22 | be. Well, class three has probably obvious. What is it? |
|
| 21:34 | , no, not that I thought gonna give me something else. You |
|
| 21:38 | came into it fast. What did say? What did they say she |
|
| 21:44 | ? She said something about minus 0.1 that's what we weren't looking for. |
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| 21:49 | wasn't looking for you. You see most of you drew is, what |
|
| 21:56 | in Rutherford and Williams paper. But you go to the article, my |
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| 22:04 | four book, you find that Rutherford was not correct. And there's the |
|
| 22:13 | why as Tess I thought I was to mention class three, which is |
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| 22:23 | the bottom here. This is it's flatter then the class 12. |
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| 22:35 | we, we gotta find out why a very important reason why on |
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| 22:44 | And it has to do with an by Ford Feld that we're soon gonna |
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| 22:56 | with that. And I can see all anxious. I'm going to go |
|
| 23:00 | . Are there any questions on No. Ok. This will be |
|
| 23:08 | the quiz. But additional to this the quiz is I'm gonna ask you |
|
| 23:16 | put not only the gas charged but wet response because geoscientists are very greedy |
|
| 23:29 | , they never have enough information. so if you know what the seismic |
|
| 23:35 | is for a gas, you have ask, well, maybe the wet |
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| 23:41 | is the same way. So you to have the right response. What |
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| 23:46 | if there's water in and these are important? Ok. Now, with |
|
| 23:57 | , I can get out of Oh let me do some. |
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| 24:19 | Hang on, hang on. Can hear me? Ok? You just |
|
| 24:25 | see it. See how far along get on this right here. She |
|
| 24:59 | am now this red window Alton. . Go to Zoom. Let me |
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| 25:07 | which windows you'll share the screen Oh, sweet. Thank you. |
|
| 25:18 | like to get back. It's a but and then it was what was |
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| 25:29 | windows but just tell me windows No, I got, yeah, |
|
| 25:43 | gotta look at the screen. the interesting thing on this one is |
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| 25:50 | everybody picked number three. Not There were a couple that were very |
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| 25:58 | and picked number one. Now, can see why you would like to |
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| 26:04 | number three maybe because it has a amplitude of a. So why did |
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| 26:15 | pick one and three? That was two that were picked? So anybody |
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| 26:22 | tell me why you picked whatever you , if you pick three, that |
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| 26:28 | wrong, I sent you an But why, why did you pick |
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| 26:37 | ? Surely you had some logic and say what I thought. Yeah, |
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| 26:45 | ahead. I, I wasn't sure one and three, but I ended |
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| 26:52 | picking three because I saw that the of the A was larger than BNC |
|
| 27:08 | it changed from 50 Hertz to 25 . And I think I, and |
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| 27:15 | assume that the, um, that amplitude of the thin bed should be |
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| 27:24 | than the amplitude of the sick But I, I think I was |
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| 27:30 | that in the case of the thin underneath the thick bed. Ok. |
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| 27:37 | , let me, let me, , you got it pretty good. |
|
| 27:40 | one thing. The amplitude of the bed does not have to be lower |
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| 27:45 | the amplitude of the thick bed. can. But if it's above, |
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| 27:49 | it's, if it's, if the bed is underneath the thick bed, |
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| 27:53 | needs to be lower, right? , not necessarily. No. |
|
| 27:58 | Well, the the thin bed can an amplitude of almost zero to about |
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| 28:08 | times the amplitude of a thick Remember there's that toy worship that it |
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| 28:15 | over and that tuning is about 40% than the flat thin thick bed. |
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| 28:22 | you're you, you got it right that when you brought in frequency. |
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| 28:31 | Because the response of the thin bed be the derivate of the um speak |
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| 28:40 | , right. Yeah. But what I say down here? Yes, |
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| 28:45 | what I was confused. But at end, I, I didn't care |
|
| 28:50 | it doesn't mean that I can put phase a different phase on the |
|
| 28:56 | So you do not, you do know what the phase of the wavelet |
|
| 29:00 | . I might be sending a wavelet looks like this. That's my primary |
|
| 29:07 | . When that reflects off of a bit, it'll be the 12 type |
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| 29:13 | response, not three. That's, is a minimum phase type of a |
|
| 29:19 | should be another low. But if sent that as my initial wavelet, |
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| 29:25 | this could be a reflection off the and the bottom of a bed. |
|
| 29:39 | both of these and B and C the same amplitude here as B and |
|
| 29:49 | has the amplitude, the same on response. Now, this event in |
|
| 29:58 | event can be bigger than this. within those two amplitudes are the |
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| 30:04 | those two amplitudes are the same. the first thing to tell you that |
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| 30:10 | they're the same amplitude, it, know, it has a chance of |
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| 30:13 | a thick bed. The other thing polarity wise, this might have a |
|
| 30:20 | polarity first, then the plus polarity . So that's the top of the |
|
| 30:26 | and bottom of the bed. it could have a plus minus here |
|
| 30:30 | a minus plus and still be a bed. We haven't. This satisfies |
|
| 30:39 | criteria. The top and the bottom the same magnitude. Yep, the |
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| 30:47 | and the bottom are opposite polarity over the same way, opposite polarity. |
|
| 30:54 | has a third, a third It doesn't matter if it's 25 Hertz |
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| 31:03 | it's 50 Hertz here. They both the same relative magnitude. The amplitude |
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| 31:11 | in there. Now, we come to here and this is where this |
|
| 31:16 | falls apart. It appears that the of the pulse depends upon the |
|
| 31:30 | A higher frequency is giving you a amplitude than this over here. |
|
| 31:38 | that, that kind of tells you that's kind of an interesting. And |
|
| 31:43 | is if you have a seismic data front of you and you're interested in |
|
| 31:52 | a particular formation, say the top the salt, you're going to find |
|
| 31:58 | where the top of the salt You know that salt is gonna be |
|
| 32:02 | real thick bed. That's one thing kind of know of. So what |
|
| 32:06 | you do? You go ahead and start filtering your stack data filter it |
|
| 32:15 | cutting out high frequencies all of a the maximum frequency is 50 hertz. |
|
| 32:20 | you try 40 then you try And as you do that, what |
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| 32:25 | is all the thin beds will start decrease in aude, but the thick |
|
| 32:34 | will hold their amplitude as you decrease frequency filtering. And it kind of |
|
| 32:39 | you these are the thick beds. are the one you wanna tie with |
|
| 32:44 | synthetic first. That's why the low kind of gives you a good tie |
|
| 32:49 | your synthetics. So several different criteria to go in your and trying to |
|
| 32:58 | which was the thick bet, which good. But that, that's a |
|
| 33:01 | good distinction that you, you should of remember the various principles we talked |
|
| 33:10 | thin beds. Did you change your ? They get higher amplitude, the |
|
| 33:17 | frequency thick beds as you lower your , they tend to stay and the |
|
| 33:26 | beds tend to disappear as you get you start lowering your frequency. And |
|
| 33:33 | good is that you can come to synthetic and find where the thick beds |
|
| 33:38 | and say, I now know how adjust my synthetic. To say this |
|
| 33:43 | the top of this, this particular you shake your head and no, |
|
| 33:50 | don't believe it. You didn't read anywhere, did you? No, |
|
| 34:04 | the thing is we, we're trying , there's not so much the, |
|
| 34:10 | know, the equation but it And the question is what does this |
|
| 34:15 | when I'm doing seismic interpretation? What's implications of this equation? That's, |
|
| 34:23 | the part we want to get Questions in the comments. I told |
|
| 34:31 | this is gonna be hard. Oh uh questions. Yeah, I was |
|
| 34:40 | little OK. I ended up putting number one but the I was really |
|
| 34:46 | about the polarity of the theme bed in most of the examples that because |
|
| 34:52 | did not tell you what the phase the reflecting wavelet is. Yeah, |
|
| 35:01 | you did not, if you had dynamite source, dynamite source, it's |
|
| 35:07 | have a minimum phase pulse and that's look like a 90 degrees face |
|
| 35:13 | So it comes down and hits a bed which already has a 90 degree |
|
| 35:18 | shift. You get 290 degrees phase . Guess what? They're either gonna |
|
| 35:22 | to give zero or they're gonna add give 180 a zero phase pulse. |
|
| 35:27 | So it's, yep. Yeah, to be to be clear uh kind |
|
| 35:37 | like the the standard is at the of your processing to, to typically |
|
| 35:43 | it into zero phase. Is that what people like to look at people |
|
| 35:48 | to look at zero phase that is . There's another reason. And when |
|
| 35:55 | was going over the concept of a Seismo gram with the cartoons that Mike |
|
| 36:04 | Drew, there were three beds that got three reflections. And he convolved |
|
| 36:12 | first with the minimum phase wavelength and right beneath it, he convolved it |
|
| 36:18 | a zero face. What happened was you convolve with a zero phase, |
|
| 36:25 | the best chance you have of picking that bed reflection is. You can |
|
| 36:32 | the reflection points and you can see spike where it occurred with a minimum |
|
| 36:40 | or a mixed phase. You, can't see them. That's that's one |
|
| 36:44 | . The other reason is you have resolution. If you're interested in seeing |
|
| 36:52 | top and the bottom reflections off of bet, you want the best |
|
| 36:59 | you can, you want the pulse be real, really narrow. If |
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| 37:04 | have a zero face, you have best chance of seeing two different peak |
|
| 37:11 | the trough at the top and the or vice versa, trough peak, |
|
| 37:17 | zero phase gives you what's called the resolution, your ability to pick the |
|
| 37:25 | and the bottom of a bed. , if everybody uses zero phase, |
|
| 37:36 | could take the data that slumber, processed it and compare it to the |
|
| 37:43 | data or data that process it, processed by Shearwater say two different |
|
| 37:52 | they both said zero phase. So should be able to just pick a |
|
| 37:57 | on this sta where the lines merge cross over on the other data. |
|
| 38:03 | should be a trough. Also any questions or comments? OK. Was |
|
| 38:58 | . Let's see. Can you see ? Do you see the screen? |
|
| 39:28 | you believe that's how I did it by myself. I'm such a big |
|
| 39:40 | . OK? I wanna go over as a reminder where we were when |
|
| 39:46 | quit last week, Cooper Basin, of Australia, which, which section |
|
| 40:01 | this again? For the notes? three point four, 3.33 point |
|
| 40:27 | Does anybody have open three point? , what's, what's the number? |
|
| 40:31 | does 3.3 say? It doesn't look it's which is number 43.4 A vo |
|
| 40:44 | . It's 3.3 slide 81. thanks. What's that slide? 69 |
|
| 41:09 | sorry. 81 is where I left last time. Got it. |
|
| 41:15 | I'm with you. Thanks. Um These over here indicate there's a |
|
| 41:22 | of cool beds. You look at acoustic and PS there's big differences |
|
| 41:27 | This is not one cool bed, are many cool beds, two or |
|
| 41:31 | , probably each one. They just average that they so much that they |
|
| 41:36 | like there's only 20 or so a bit more resolution to show you lots |
|
| 41:42 | cool beds in there, the velocity the sand and shells about twice that |
|
| 41:48 | the core velocity. The density of and show about two times that gives |
|
| 41:54 | reflection coefficients of about 0.6. That a big number 0.6. The permian |
|
| 42:08 | are right where the red arrow says is a synthetic seismo gram and it |
|
| 42:13 | like it wants to match somewhat right . And oh, it does OK |
|
| 42:19 | . And maybe you just can kind pull this down or stretch it a |
|
| 42:23 | bit. But we don't like stretch squeeze. We like to know the |
|
| 42:30 | why if you are going to stretch squeeze fine, make sure you put |
|
| 42:35 | synthetic seismic gram match without the stretch squeeze because the interpreter needs to know |
|
| 42:43 | because if interpreter runs into problem further the line, they gotta know that |
|
| 42:49 | match was not pure. The stretch squeeze was in there. No will |
|
| 42:56 | help? What we've done before? did a stretch and squeeze, did |
|
| 43:02 | couple things. One is we made velocity and the density the same whatever |
|
| 43:08 | indicating a coal bed. We realized thin beds are not gonna give you |
|
| 43:14 | right amplitude. They, they're gonna smeared with the beds around them. |
|
| 43:20 | the fast cool will make the velocity a fast sand will make the velocity |
|
| 43:27 | the slow cool, become faster because being averaged over 4 to 6 ft |
|
| 43:35 | the coolest might be only 2 ft . So let's see what happens when |
|
| 43:43 | get that last time I showed you nice way of going ahead and making |
|
| 43:56 | synthetic that matched like a velocity The velocity log is in time here |
|
| 44:04 | this is your seismic data. And mean, they're synthetic and what the |
|
| 44:09 | has it has a wavel that's the filter as it, it's sort of |
|
| 44:16 | a boxcar. But the easy way do that is to put a 270 |
|
| 44:21 | face shift on it. And a dominant frequency, we also see that |
|
| 44:31 | synthetic is a longer in time. the actually velocity sonic log is this |
|
| 44:44 | displaced. This is put to time the sonic lo this goes from depth |
|
| 44:49 | time using the seismic excuse me, is using the sonic velocity. This |
|
| 45:02 | using the seismic velocity, seismic velocity slower and it's therefore gonna be longer |
|
| 45:12 | people have these synthetics, they think taking this and stretching it down. |
|
| 45:22 | we're going to look at what the is. We have a, we |
|
| 45:27 | a couple slides. It's gonna show the front of the wave propagating is |
|
| 45:35 | low frequency. And so if we this propagating way which we generated in |
|
| 45:42 | , the catalog, we see that has a spectrum, it kind of |
|
| 45:48 | this, which is that over And this is the signal portion. |
|
| 45:54 | the portion where we get from the period to multiples. Here's the here |
|
| 46:05 | the propagating way if you send a down and that spike gets to this |
|
| 46:15 | . This is acoustic and pains. now just going to go ahead and |
|
| 46:20 | a constant acoustic impedance right there. make that a constant. So when |
|
| 46:25 | energy is done, when it gets this point, it'll continue, but |
|
| 46:30 | never come back. There's no So, whatever we do the wavelet |
|
| 46:35 | before going into there, it can back to the surface and it is |
|
| 46:41 | wavelet right there going down there, propagating wavelet, blow it up a |
|
| 46:47 | bit. When I get down to this two way time, this is |
|
| 46:54 | propagating wavel of one that's really interested tell you more is going all the |
|
| 47:00 | down to here there. Stop Fred. Don't go into the cold |
|
| 47:04 | . Ok? I stop right Don't go into the cold beds and |
|
| 47:08 | this wavelet right here and time is down here. So you'll notice that |
|
| 47:16 | peak, it's all black for about milliseconds. Now, let the energy |
|
| 47:23 | through the gold beds and get back the surface and look at what comes |
|
| 47:28 | to the surface. A very low pulse. What does that mean? |
|
| 47:34 | means this if you have a reflection here and this is some depth Z |
|
| 47:42 | I'm gonna allow it to be this here. Here's here is the wave |
|
| 47:47 | you're gonna get, you're gonna get that looks like this, that's gonna |
|
| 47:55 | the reflection off of this right That's gonna be this wavelength. |
|
| 48:00 | if you look beneath right here and get a reflection down there at this |
|
| 48:15 | rating here. Now, this is same seismic, here's what's gonna |
|
| 48:28 | You're gonna get this reflection, it occur right up here. This is |
|
| 48:35 | zero, but you're gonna see this right here because it's an amplitude. |
|
| 48:42 | can't see times zero here. You'll this amplitude. That means this pulse |
|
| 48:50 | been delayed by 2030 milliseconds. The test these cool beds put a |
|
| 48:58 | Now that's because of all the inter bouncing, the inter bed bouncing, |
|
| 49:03 | the wavel it get fatter. If look at it, it looks like |
|
| 49:11 | a phase shift sitting in here compared zero up at the top. Anybody |
|
| 49:22 | heard of the geophysicist, geoscientist that's an inversion. Have you ever heard |
|
| 49:28 | word inversion talking about, take my data and invert it. What are |
|
| 49:34 | gonna invert it back to? you have wiggle traces. The goal |
|
| 49:43 | can you get back and tell me the wave propagation velocity was above and |
|
| 49:50 | that wiggle give me the, the propagation velocity. That would be an |
|
| 49:58 | . But that assumes that you have phase like you do right here. |
|
| 50:06 | down here, he got a 45 spaceship. Now it's OK just until |
|
| 50:13 | go into those schools as soon as go into those schools, bam, |
|
| 50:17 | gone. Any geophysicist in the that's, that's the processing a little |
|
| 50:26 | . This is gonna require what's called decon. You got to de involve |
|
| 50:32 | data one time all the way through back and then go a little bit |
|
| 50:39 | down to about here and interrogate this the second decom and you only apply |
|
| 50:47 | . So the first trace starting down , it's very important. Otherwise, |
|
| 50:53 | data is gonna be screwed up. the other thing we'll say it on |
|
| 51:07 | right here. And this is in paper, by the way that you |
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| 51:11 | is there are four synthetic seismograms that can get. The first thing you |
|
| 51:18 | start off with is I can make regular convolutional model of a synthetic seismic |
|
| 51:26 | . And that's this and that shows where the top of the coals and |
|
| 51:30 | base of the coal is or I for those bouncing back and forth multiples |
|
| 51:38 | scattering effect. It depends upon the gray. A word. Geologists often |
|
| 51:45 | if the stat gray varies quickly, quickly, um You have a hard |
|
| 51:56 | , be positive and uh all of sudden the sea level drops and now |
|
| 52:07 | putting the shield on uh oh sea rises. Here comes that thing and |
|
| 52:12 | . Another one. Oops it Here's more shell, the properties and |
|
| 52:17 | and shell are really drastically different. only place I know that's really, |
|
| 52:23 | , really, really bad is the Sea and that is just in hydrate |
|
| 52:30 | chill back and forth, back and . And even as early as the |
|
| 52:37 | seventies Midway Amico, who was out were wondering, is there a way |
|
| 52:44 | I can get an energy source that down very, very low frequencies so |
|
| 52:52 | can get my energy to pass through ? Oh, here is the primary |
|
| 53:02 | , but that primary has a time wavelength. And the thing that you |
|
| 53:06 | is at the base of the call you don't have the time during wa |
|
| 53:13 | . This is what it's really gonna like over here. This is what |
|
| 53:18 | seismic is gonna look like this So there are two additional synthetics that |
|
| 53:24 | get and one is all multiples and other one's all primary. You add |
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| 53:33 | two together, you get the one the left which is your seismic. |
|
| 53:45 | . It's time for a game. ever make match a synthetic size of |
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| 53:54 | Nazar chance. Are you ready? is a conventional synthetic seismo gram. |
|
| 54:03 | the field data at the well build data synthetic. This ties to |
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| 54:21 | . This ties that, this ties , this looks like it ties |
|
| 54:32 | So um that little time difference, might be a little bit more here |
|
| 54:39 | maybe stretch it a little bit, like that. Now you are going |
|
| 54:45 | a lot of calls. Why are doing seismic? Why would you be |
|
| 54:53 | seismic beneath the coal beds? What you be looking if you had a |
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| 54:57 | of cool bitch geologists? What are looking for? What's your target? |
|
| 55:03 | you have a whole bunch of cold ? What kind? What? |
|
| 55:12 | they're above the premium. They're, above the source. You got a |
|
| 55:21 | of shale but you don't have O only the risen in lowering sea |
|
| 55:26 | . You got sand there too. what would your goal be? Would |
|
| 55:33 | try to find shallow gas coming from cool? You're not gonna drill the |
|
| 55:39 | . You wanna drill a sand, in there. Now, the sand |
|
| 55:46 | gonna be in channels most likely. much does sand compact compared to |
|
| 55:56 | If you have 100 ft of coal you have 100 ft of shell, |
|
| 56:03 | have 100 ft of sand after 24 years. What's the thickness gonna be |
|
| 56:12 | the cold sand and chill? Do believe that the sediments will compact when |
|
| 56:29 | get other sediments on top of You believe in compaction? Now, |
|
| 56:35 | much are they gonna compact if you 100 ft of coal? What's |
|
| 56:40 | what's it gonna compact to 100 ft , shall 100 ft of sand? |
|
| 56:46 | much will it compact? Two 2 ft, 20 ft 80 |
|
| 56:53 | How much will pat? What is look like? How much do you |
|
| 57:03 | that's gonna compare a lot? how much somebody yell numbers? So |
|
| 57:12 | can say you're wrong. 60%. going for 7070 I got what? |
|
| 57:19 | ? 79 75 80 80? How about 80%? Ok. So |
|
| 57:25 | you have 100 ft of coal, gonna get down to be maybe 20 |
|
| 57:29 | thick. How about shell? How is she gonna compact? You |
|
| 57:39 | No shell is gonna go back to heck of a lot too. A |
|
| 57:43 | of pros in there when you deposit . What's your pros? 60 70% |
|
| 57:50 | , up that shallow bay? So gonna get done maybe 40%. |
|
| 57:58 | now you have 20 ft, 20 of coal, you have 60 ft |
|
| 58:07 | shell. How much is a sandy get back? Nice grains of |
|
| 58:15 | How much are they gonna compact? it another way. What's gonna compact |
|
| 58:22 | shale or sand chill? So the compacts, it goes to 90 |
|
| 58:32 | Now, all of a sudden you 90 ft of sand, 90 ft |
|
| 58:38 | sand, 60 ft of shell, ft of coal. And what is |
|
| 58:46 | game? Your game is to find sands and you want to find the |
|
| 58:53 | sands? Oh, it's easy. here, friend. Just find the |
|
| 58:59 | and the bottom right there and find where this is the thickest and that's |
|
| 59:06 | you're gonna have Sam. What, , what do you think the normal |
|
| 59:11 | is the normal procedure is to look this differential compaction. And where do |
|
| 59:18 | normally find it? The first thing done that they've done, done that |
|
| 59:22 | did for many years. If you the c top of the coal |
|
| 59:27 | they could be dipping and then you this little bump, guess what? |
|
| 59:33 | drill, you drill the bump because has the best probability of having, |
|
| 59:41 | , a sand that has a differential compared compared to the s that's your |
|
| 59:49 | . It's called bump policy. Oh you, we, we caught |
|
| 59:56 | This is, this is how a of the targets have been drilled in |
|
| 60:01 | bump drill the bumps when it comes cool. But all of a sudden |
|
| 60:06 | the bumps are drilled now they gotta those because this is shallow, |
|
| 60:15 | I'm in shallow sand. How about ones that are deeper down here? |
|
| 60:19 | of a sudden differential compaction is not bumps up at the top, but |
|
| 60:25 | have a change of thickness, differential changes. So that is why we |
|
| 60:32 | know this time versus that time. right here says that's a good target |
|
| 60:41 | finding extra san. It's thicker. might not be a bump on the |
|
| 60:47 | might be deeper. So that is the interpretation came in. Now, |
|
| 60:55 | , that is the new, the technology. The course problem is it's |
|
| 61:02 | good because let's take a look. is at the, well, this |
|
| 61:11 | the field data and this is a synthetic seismo gram and it only has |
|
| 61:20 | in it over here. This synthetic has primaries plus multiples and this is |
|
| 61:34 | primary event. And as I follow yellow across these are the, this |
|
| 61:39 | where the primary event is sitting over . This is a primary plus multiple |
|
| 61:46 | as we go and follow it to right following my cursor to the |
|
| 61:52 | it dies out that says this event a multiple. The base of the |
|
| 62:03 | is actually right up here, not here. And that is what that |
|
| 62:11 | you a mi a misdirection, you're drill this and it turned out to |
|
| 62:16 | a multiple. And so that's the , where are the multiples? |
|
| 62:21 | how do you find them? There are techniques called inverse scattering series |
|
| 62:33 | this has been promoted by actually a of H geophysicist. Anybody know who |
|
| 62:40 | is? Not me. I wouldn't this crap. Excuse me. I |
|
| 62:46 | this. Who's the U of H Art Weiglein in the physics department? |
|
| 62:52 | the one who proposed that and he, he gave several very nice |
|
| 63:00 | . It's very difficult. But one the things they showed is you can |
|
| 63:05 | your seismic data and you can predict the multiples are. So he shows |
|
| 63:12 | that when you go from primary only to your primary less multiples, these |
|
| 63:22 | multiples coming in and you can compare to your field data. And if |
|
| 63:28 | see them on your field data, know, there are multiples and |
|
| 63:37 | he showed methods where you can now search for primaries. And what this |
|
| 63:47 | comes out to show is using the , we actually took this point and |
|
| 63:58 | tied it to this point. And this point ties over here shallower. |
|
| 64:08 | other words, we overestimated the thickness about 20 milliseconds thir or 30 |
|
| 64:16 | something like that. Let's go take break for but to, to about |
|
| 64:28 | after two and we'll open the I think we can. Who, |
|
| 64:34 | the pretzels and peanuts who brought, was supposed to bring those? |
|
| 64:38 | I, I shouldn't say this in of those people away from here and |
|
| 64:43 | , never land. I'm sorry. regroup about 215. OK. Let's |
|
| 64:55 | one more time if I can get of that marker there. No, |
|
| 64:59 | can't. I get new to get of the new ones but not the |
|
| 65:08 | one. OK. We hope when quit this, it's the size. |
|
| 65:12 | you want to get rid of all markers you put on there? And |
|
| 65:15 | could say yes, I, I've that when you have a lot of |
|
| 65:23 | multiples, you can identify them. helps your interpretation. The question |
|
| 65:28 | can we get rid of the multiples answers? There are some methods. |
|
| 65:32 | first method I want to show you based on our art. We line |
|
| 65:37 | inverse scattering series. And I'm going show you that here are the coal |
|
| 65:45 | , there are 5060 coal beds sitting there. And this is a regional |
|
| 65:51 | called the cat nai and exists all the basin that were our interests and |
|
| 65:58 | the magic mouse. Now I'm coming , I'm gonna bounce off the coal |
|
| 66:05 | . I'm gonna bounce up to the . Now I'm gonna bounce back down |
|
| 66:10 | then when it bounce up to the , this is an internal multiple. |
|
| 66:17 | distance is gonna be an extra travel . So I take the length of |
|
| 66:23 | blue and I repeat it in I come over here, take the |
|
| 66:28 | travel time due to the multiple and and put it in green. Now |
|
| 66:36 | at the tip of the green, at that right there. What you |
|
| 66:41 | being flat is this extra bed that multiplied that multiple, the inner bent |
|
| 66:49 | there. That and that right there the same dip as you see right |
|
| 66:55 | . It's kind of neat because everything is dipping the other way. So |
|
| 67:00 | know, this isn't right. Something be wrong and that's a multiple. |
|
| 67:08 | we go ahead and apply inverse scattering and you see on the next slide |
|
| 67:14 | lo and behold, there's no Well, there is, it's not |
|
| 67:19 | because this is what they call a . We know even theoretically it cannot |
|
| 67:26 | rid of it. Exactly. Just , but it does get it |
|
| 67:30 | Maybe 20% it gets rid of maybe 40% of the amplitude. |
|
| 67:38 | one of the things you ought to me and we'll give five points of |
|
| 67:42 | to your next score. Is this , why is the multiple higher |
|
| 67:51 | Then the reflections at about the same , these deep reflections or low |
|
| 68:01 | the multiple is high frequency. why would that occur? Because where |
|
| 68:15 | the multiple come from? The multiple in? Because I go down and |
|
| 68:25 | this multiple right here its travel path up back and down again like |
|
| 68:31 | Is that right there? That's that time. So are you telling |
|
| 68:38 | Fred that this multiple never went through coal beds? Yeah, it might |
|
| 68:47 | that it went through the coal beds of the extra time, but it |
|
| 68:52 | went through the coal beds at actual . It's just the extra time. |
|
| 68:57 | , if it didn't go through the beds, what happened? Oh, |
|
| 69:01 | right. I remember you telling me bouncing back and forth on the cool |
|
| 69:06 | lowers the frequency. That's right. through the coal beds, you're gonna |
|
| 69:12 | a lower frequency. So all these they all came, you had to |
|
| 69:18 | through the cold bed and back up surface in order to get a |
|
| 69:23 | So lower frequency with the primary, multiple higher frequency. Let's show that |
|
| 69:35 | . Here's the full spectrum, all . Now, I'm only gonna look |
|
| 69:44 | 0 to 20 hertz. All the frequency gone away. Where's the multiple |
|
| 69:51 | here? Wow, that multiple surely been suppressed over here compared to on |
|
| 69:59 | other side. That's right. let's go the other way. Let's |
|
| 70:05 | look from 20 let's look at the frequency. So here I looked at |
|
| 70:11 | low, here we look at, , I'll be gone. See all |
|
| 70:15 | nice primary events come down here. did they go? Oh, they're |
|
| 70:21 | here in the low frequency. what is that? That's the |
|
| 70:26 | it's at the high frequency. Once , you enhance the primary event. |
|
| 70:35 | in a low frequency. Anybody ever of a processing geophysicist? Yes, |
|
| 70:44 | all are in the process processing A lot of them do not like |
|
| 70:51 | seismic because the land seismic has surface , land seismic boxes back and |
|
| 71:01 | obstacles on a near surface, a , a trench in the desert, |
|
| 71:11 | dunes, they bounce off back and and they all have this low |
|
| 71:16 | So what do they do? Processors to cut out the low frequency, |
|
| 71:23 | out the low frequency. What are cutting out the primary events and you're |
|
| 71:33 | the multiples? And this is why effort by the processor has to be |
|
| 71:41 | not to get rid of the low . Some of them might say, |
|
| 71:46 | Fred look really? It's only 10 20 Hertz probably that we got rid |
|
| 71:56 | . Oh yeah. Ok. going from five to 10 Hertz is |
|
| 72:05 | octave, going from five to 20 is two octaves. When you threw |
|
| 72:19 | 20 Hertz. Then there you threw one octave of my data. That |
|
| 72:27 | my wave is gonna ring more if have a very narrow bandwidth, if |
|
| 72:35 | wanna center all your energy right around , say at 30 Hertz, what |
|
| 72:40 | a 30 Hertz wave look like? it's a constant frequency. As I |
|
| 72:47 | before, out in L A, have a constant frequency at 60 |
|
| 72:54 | And all you see on the trace just the same sway over and over |
|
| 72:59 | over again, that's electrical. You put a filter to get rid of |
|
| 73:04 | notch. OK? Enough said he it too many times when you go |
|
| 73:13 | 40 to 100 Hertz over here. You could take a spectrum mirror but |
|
| 73:19 | very little signal and that high So let's summarize this in another |
|
| 73:31 | This is a multiple and the signal ra then as 5 to 20 |
|
| 73:44 | the multiple here it goes from 5 45 Hertz. When I get rid |
|
| 73:55 | , if I apply iss the the signal, it's the same, |
|
| 74:03 | multiple, it still has the same here as it has here. The |
|
| 74:09 | of it over here. Is, doesn't have the amplitude here. The |
|
| 74:15 | is one signal we don't touch, is one but the multiple has been |
|
| 74:21 | down in amplitude. So the multiple is one third of it was originally |
|
| 74:28 | due to this process. Now, on, let's do another thing. |
|
| 74:36 | go ahead and look at what happens this multiple when we go ahead and |
|
| 74:43 | and only low allow the low Now the signal and multiple are the |
|
| 74:49 | there. But over here, we have low frequency. And what does |
|
| 74:53 | mean? You use half the See that's 5 to 45 5 to |
|
| 74:59 | you lost about half the spectrum. the multiples reduced by half. So |
|
| 75:06 | do we have? We had the slide that reduced it by a third |
|
| 75:17 | same spectrum and then this line reduces by a half. So taken together |
|
| 75:25 | have 1/6 multiple, you've reduced you've increased your signal to noise by |
|
| 75:31 | to 1 significant. This is what removed all these flat events that was |
|
| 75:45 | out of the data. Here's that again. OK. There it's |
|
| 76:00 | you got low frequency. What can do? One of the things we |
|
| 76:07 | do is find out where the spectrum . This is the spectrum, we |
|
| 76:16 | into this state right here. And says originally your data went up like |
|
| 76:24 | , it went over to about 40 and then done. But all this |
|
| 76:29 | right near all that is mostly So go ahead take this data that |
|
| 76:42 | all the way on here and only the signal. So we leave the |
|
| 76:48 | right here only. And we now have no multiples. So take the |
|
| 76:59 | and go up to the very high . So we now have a much |
|
| 77:03 | spectrum but it's all signal and that us this. So now look at |
|
| 77:10 | frequency that we we can use beautiful here. Look at the faults in |
|
| 77:18 | those two major reflectors. Very really helps your interpretation. These are |
|
| 77:26 | type of techniques that can be The idea is get rid of your |
|
| 77:33 | before you try to increase the I have a question, how do |
|
| 77:41 | know what the signal is like? see that you put a box around |
|
| 77:46 | on that last slide. But how do you know that's it? |
|
| 77:52 | because it's the higher pl good Let's see if I have each one |
|
| 78:20 | these right here represents what is the going down in? Coming back at |
|
| 78:31 | particular two way time? This is we call the propagating wavel as we |
|
| 78:38 | before. When I get closer and to this cool bed, the propagating |
|
| 78:46 | , it still stays the same. once I go through it, it |
|
| 78:51 | changes tremendously from right here to the , the cool beds ate all the |
|
| 78:58 | frequency how, when you go in cold bed, you bounce back and |
|
| 79:05 | , bouncing back and forth, broadens wavelet, every coal bed you m |
|
| 79:11 | bounces back and forth, it broadens more. This keeps on broadening. |
|
| 79:17 | finally, you can see how broad wave of is. So I'm drawing |
|
| 79:25 | line here and that line I'm drawing the signal portion of the uh |
|
| 79:40 | In other words, everything down here what we call long period multiples, |
|
| 79:49 | appear or the short period multiples, they are what reflects off of the |
|
| 79:56 | . So if I take, if take this right here, that right |
|
| 80:08 | the signal portion and I do a transform, I go from zero to |
|
| 80:15 | Hertz appear shallow red and yellow are big amplitude. It says that I |
|
| 80:28 | a lot of amplitude up in Everything hurts. I got a lot |
|
| 80:36 | frequency just in the propagating wav. going down here has a nice |
|
| 80:45 | But when I go through, go these cool beds, look at this |
|
| 80:53 | . All of a sudden I go something that had 50 Hertz in |
|
| 81:01 | No, I only have about 15 is very low amplitude. It says |
|
| 81:09 | you get in the cold beds, only signal you have is zero to |
|
| 81:15 | 15 hertz. That's this wavelet right . So we know it's in a |
|
| 81:23 | low frequency and here's the single the is from here out, that's |
|
| 81:49 | that's a signal, that's this spectrum here, the spectrum is gonna be |
|
| 81:56 | Gaussian wavelet. And so I kind picked the peaks what's in between. |
|
| 82:04 | do those peaks. That's the geology that gives me something like 20 Hertz |
|
| 82:12 | gonna be the maximum. That's how find it. Now, here's another |
|
| 82:24 | from uh Algeria, this is a thick salt sequence. And yet when |
|
| 82:35 | make a synthetic Seismo gram, there's salt reflection. But this is all |
|
| 82:44 | . Are there any variation? And two logs looks like the gamma log |
|
| 82:49 | the density log. But if I a synthetic with multiples, wow, |
|
| 82:56 | how this ties now very nicely. you put the multiples in nice |
|
| 83:06 | this is what you wanna get rid . This is the zone going all |
|
| 83:13 | way across. This is the these are the same input is a |
|
| 83:21 | time migrated data. I show there's multiple and there it is suppressed. |
|
| 83:27 | is against inverse scattering. The the but was that it's not this, |
|
| 83:34 | can see the higher frequency that you're out too. This is sort of |
|
| 83:41 | dramatic one, same area. Same . We know the signal, we |
|
| 83:49 | this red box. The signal says got from about 10 Hertz to about |
|
| 83:57 | Hertz. That's what it said. we know that everything above 40 is |
|
| 84:03 | noise. So again, go ahead it down save the low frequency and |
|
| 84:12 | expand the low frequency to the high zone of interest is in the |
|
| 84:20 | You want to delineate the faults. let's look where the faults are but |
|
| 84:28 | high frequency on there and there's no . Now, look at the fault |
|
| 84:32 | you have there. Very nice coming faults over here. Nice, hard |
|
| 84:39 | see the conventional data until you get of the multiples. This by |
|
| 84:45 | this is the salt. You don't to see faults going through the salt |
|
| 84:50 | you don't. OK. That's all this section. Are there any |
|
| 85:02 | I'm sorry. No. OK. . Professor, I, I got |
|
| 85:14 | question about this technique to like expand band. I mean, if you |
|
| 85:18 | the, your frequency that you want span III I don't get it. |
|
| 85:22 | mean, what is what we are with the software to expand the signal |
|
| 85:28 | the high frequencies? OK. it's, it's called spectral decomposition and |
|
| 85:36 | , you're, you're adding the fundamentals I'm trying to think in the back |
|
| 85:40 | my mind what slide I have that ? Um Let me uh uh raise |
|
| 85:57 | question whenever I get this finished with . OK. I I'll search it |
|
| 86:08 | I'll show you how it's done. ? And I, I have the |
|
| 86:12 | , it just can't remember if it's this section or not. Um I'm |
|
| 86:19 | take, take it away from you a second. Oh Are there any |
|
| 86:23 | questions? No. OK. I'm take it away from you and I'm |
|
| 86:31 | looking at looking and see if it's this. Ok. Let me try |
|
| 86:57 | again. We go there. Bye . Work. I say Zoom. |
|
| 87:11 | say sheer pick it. I share . Can you see my signal? |
|
| 87:20 | slide now? Yes. Yes. . OK. It's we call the |
|
| 87:38 | call frequency extension of signal. It's around for several years. Some people |
|
| 87:46 | it. John Castagna doesn't like He has his own methods. Here |
|
| 87:54 | a seismic trace and this is Uh I'm sorry which slide there is |
|
| 88:04 | , this is in the same section you were in on slide. 70 |
|
| 88:10 | OK. Thanks. Did you get it yet? Found it? |
|
| 88:20 | OK. Good. This is a actually but it it could be the |
|
| 88:27 | trace. It has primary and The way this is derived, you |
|
| 88:35 | a short window maybe 200 milliseconds This that energy that's in there. |
|
| 88:48 | take this and you do a fourier and what the fourier analysis says. |
|
| 88:54 | you look up at the top that's going from 2 to 72 Hertz. |
|
| 88:59 | says you got some energy that has high amplitude rate up here at this |
|
| 89:07 | . And there is the energy also little lower but it's at a higher |
|
| 89:14 | . And if you look at it turns out this low frequency which |
|
| 89:21 | we expect the signal here here Then down here. Now meanwhile, |
|
| 89:29 | I draw where the blue is, the multiples. So this trace over |
|
| 89:39 | , we can separate the primary energy the multiples by coming in here like |
|
| 89:50 | and filtering out this data here leaving the long period multiples. So I |
|
| 90:01 | taken this seismic data launch race and broke it into 80 traces and each |
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| 90:11 | is a different frequency. And then upon what the design of this curve |
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| 90:20 | , I went ahead and got rid the multiples, the blue stamps. |
|
| 90:25 | now I just have this day of year, but here's my multiple really |
|
| 90:32 | frequency and I want higher frequency. let's see if we can go ahead |
|
| 90:40 | remove that. This is, remember said get rid of the multiple with |
|
| 90:47 | multiples up here. Now we can you energy back here, give you |
|
| 90:53 | back here based on what we So this energy right in here in |
|
| 91:04 | time domain, it looks like So that spectrum is this right |
|
| 91:11 | What I have left is that spectrum this is this is called the, |
|
| 91:18 | harmonic. Now, I want the harmonic and what that is it. |
|
| 91:24 | remember I know this, I know , that's this portion. I know |
|
| 91:32 | I then take this portion right here I go down to double the frequency |
|
| 91:40 | I put that same amplitude, I this frequency up to here. And |
|
| 91:46 | take that amplitude and put it I do that for the third |
|
| 91:54 | take that triple that value and put amplitude that he had there at the |
|
| 92:01 | right here, triple this frequency to and put the amplitude up. Now |
|
| 92:07 | time I do this, I know the time response is because I got |
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| 92:13 | frequent, it's very important that this zero phase data. No, I'm |
|
| 92:21 | to do something with it. I these three right here, I sum |
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| 92:26 | together and I get this in the domain. It's just the summation of |
|
| 92:34 | these three spectrum add them together. get this what was only the low |
|
| 92:41 | now contains all the bunch of the . So I'm able to add some |
|
| 92:48 | energy right there. And so I've , I've, what I've done is |
|
| 92:54 | this got the wave that, that to and then went ahead created the |
|
| 93:04 | , adding them together, sum them then came back over the frequency domain |
|
| 93:10 | have extended the frequency. Well, I get the second harmonic, I'm |
|
| 93:21 | doing it for everything above it. do the whole, the whole, |
|
| 93:29 | whole time length is gonna have its harmonic computer. Not just that one |
|
| 93:35 | , I've taken the one window that can see what I did for one |
|
| 93:39 | . I can do it above that above that above that, but you |
|
| 93:42 | do it all in one slide, slice and that's what I've done right |
|
| 93:50 | . I've taken, gotten rid of noise component and we, you analyze |
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| 94:01 | by the propagating waver catalogs. I'm give you a new area. I |
|
| 94:11 | you to take this home, put on your computer, dial up the |
|
| 94:16 | to 3D interpretation package. And I you to tell me what's the main |
|
| 94:22 | ? What are you looking for in series? Oh, my God, |
|
| 94:25 | . Yeah, that's right. at 530 before you get your first |
|
| 94:32 | , bree beer, pick this point here and tell the computer. I'd |
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| 94:39 | you to follow that event all around 3D survey automatically pick it and then |
|
| 94:47 | a map. So I know what structure in the area. Well, |
|
| 94:51 | computer comes over here and says, where do I go? Do I |
|
| 94:56 | up where I go across? What the computer do? What should it |
|
| 95:04 | up here? All of a sudden at this, there's a lot of |
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| 95:08 | marks. So we do the same . What you're looking at is a |
|
| 95:16 | processor. Heard client said we were and we vibrated all the way to |
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| 95:24 | Hertz. I want my final I want my final section to have |
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| 95:28 | Hertz in it too. No matter you can show them that all those |
|
| 95:35 | reduced it. You don't have anything than 20 Hertz, everything is below |
|
| 95:40 | . And so taking this, getting of all the high frequency noise leaving |
|
| 95:48 | and then once you got the expand it back up to where your |
|
| 95:54 | red says your spectrum was in doing . That's what you get. |
|
| 96:01 | look at the continuity that you get the signal going across there, that |
|
| 96:08 | is gone. It's a phase And the high frequency is what |
|
| 96:16 | The processor was told you gotta have frequency. Well, the processor gave |
|
| 96:22 | high frequency in this section. You all the same frequency you have in |
|
| 96:27 | , but it's in random noise. because of random noise, you don't |
|
| 96:32 | begin to see the continuity, same the spectrum, just different face. |
|
| 96:44 | I think I showed you this this is the same area. But |
|
| 96:51 | , this is where the signal Would you rather interpret that very difficult |
|
| 96:59 | make a synthetic that matches? So would your first thing be a lot |
|
| 97:04 | times you can kind of look at spectrum and say, you know, |
|
| 97:11 | kind of believe this, I think was put on, I think it's |
|
| 97:16 | multiples. And so right in here filter it low pass filter it night |
|
| 97:25 | day difference, this seismic section right . Now look at the nice tie |
|
| 97:40 | getting with the synthetic, here's the data, here's the low frequency and |
|
| 97:52 | the high frequency you add these two together, you're gonna get the one |
|
| 97:57 | the left, but just looking at . So, you know, that's |
|
| 98:05 | pretty God darn structure to ignore. pretty hard to say that that's fake |
|
| 98:14 | I, I believe that was all over there. A lot of noise |
|
| 98:18 | super opposed. It still has some in it, but you got the |
|
| 98:23 | structure now you'd miss it totally. other comments. And the, the |
|
| 98:33 | I point these out is you can ahead and do an amplitude interpretation, |
|
| 98:38 | you gotta know what amplitude you get rid of that noise. This |
|
| 98:48 | taking the same original data giving up spectrum right here. Look on the |
|
| 98:56 | side. It's about the same, at the difference. This was the |
|
| 99:05 | noise that was replaced. No kinda . OK? Any other comments or |
|
| 99:27 | ? OK. I'm going to go another section. How are we doing |
|
| 100:54 | ? Do you have a screen, screen? OK. Thank you, |
|
| 100:58 | . Thank you, sir. Mm are the various sections but what I'm |
|
| 101:16 | to repeat is the quick overview was first day. This is the the |
|
| 101:23 | that I showed you the first day to bring us up. I told |
|
| 101:26 | at the very beginning we're gonna go the whole course and two hours or |
|
| 101:31 | hour. So I went over the course in an hour and then I |
|
| 101:36 | we'll see it again later on We're seeing it. We're seeing these |
|
| 101:41 | a little later on, but we're expand a little bit on them. |
|
| 101:47 | I said before, you can drill these locations and they're all hydrocarbons, |
|
| 101:55 | all guests. The only reflections you're at are those that have reflect |
|
| 102:03 | So let's look at the gamma gamma curve that you put in. |
|
| 102:09 | well describes the pathology in a petro analysis. How do we describe |
|
| 102:17 | Mathematically we had a brine saturated a gas saturated sand. One of |
|
| 102:27 | things that we said, I'll always this, Fred. When you go |
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| 102:32 | a brine saturated to a gas saturated wave decreases, density decreases, poisons |
|
| 102:43 | they all three not the sheer weight the poison. We then said ah |
|
| 102:53 | need to talk about amplitude. So told you here's the basic equation that |
|
| 102:59 | have for the normal incidents. What the normal incidence that refers to the |
|
| 103:07 | of the reflective way to the amplitude the incident? And what is |
|
| 103:13 | It's the particle velocity? It's a displacement. It's a particle acceleration or |
|
| 103:22 | could be stress, particle stress. in there. Particle velocity. Oh |
|
| 103:31 | that like limestone? 16,000 ft per ? No, no, no, |
|
| 103:35 | , no. That's the wave propagation . A Fred. You got too |
|
| 103:41 | . You got wave propagation. You particle velocity. Take one. Oh |
|
| 103:46 | can't. So what's the difference? the difference between particle velocity? And |
|
| 103:52 | propagating. What differentiates them? Very . Very who knows the answer. |
|
| 104:04 | velocity, wave propagation? Oh Let's ready. We got the bus. |
|
| 104:13 | go take a field trip, take field trip and do a little |
|
| 104:16 | We're rolling down and is a, crop of the Austin shark limestone. |
|
| 104:22 | got c called limestone. We're gonna ahead and measure the velocity, the |
|
| 104:29 | velocity. Yes, we come back and we'll go back 20 million years |
|
| 104:35 | now. OK. We have the road c major particle velocity. |
|
| 104:42 | no, no. It's gonna be ft per second. That's the way |
|
| 104:47 | , it then depend upon time. the particle velocity does depend upon time |
|
| 104:55 | as the eighth earth shakes, you see that that particle, that one |
|
| 105:00 | there. It's moving back and And how much is it moving back |
|
| 105:03 | forth with respect to that original Well, that's displace it. Take |
|
| 105:08 | to the river to displace it. velocity. So the particle velocity, |
|
| 105:14 | depends upon time. Wave velocity But you said particle that means take |
|
| 105:20 | little selected point if the particle velocity greater than 16,000 ft per second, |
|
| 105:29 | for someplace to shelter. Because what is you're getting, you're beginning a |
|
| 105:36 | because all the material behind the first gonna come ahead of it. Particle |
|
| 105:41 | becomes faster. This whole thing moving and forth is faster than it's supposedly |
|
| 105:46 | projected as a tsunami. We measured normal incidence reflection coefficient. We |
|
| 105:59 | look at that, that's Brian and get how about that? My little |
|
| 106:04 | here, you could just look at normal incidence and tell the difference between |
|
| 106:09 | saturated and guess saturated. That's Maybe not be able to do that |
|
| 106:14 | the time or are interesting because somebody gonna say maybe a vo should be |
|
| 106:24 | determines the fluid. So we what is Aviel? Well, we |
|
| 106:30 | a guy by the name of Cod , look at that amplitude a little |
|
| 106:37 | differently. This is a stack section , take this trace right here, |
|
| 106:45 | that trace and that's stacked. What the amplitudes of each trace going into |
|
| 106:54 | ? That looks like it's a 10 . So that's called tenfold and stack |
|
| 107:00 | horizontally and you get this trace. said, go ahead and look down |
|
| 107:05 | do that now at your normally, The near trace is small x bigger |
|
| 107:12 | the far or the small near traces smaller than the far. We found |
|
| 107:20 | all three of these skin exists, was mostly indicative most of the time |
|
| 107:28 | one right here. Case two. was all of Cofield 1955. The |
|
| 107:38 | thing he said, I don't think gonna use it in the near |
|
| 107:44 | He wrote that in the article and was right, it took over 20 |
|
| 107:48 | before we started to use it but important thing for us is here's a |
|
| 107:55 | ray log, this is done inside borehole. You put that against the |
|
| 108:04 | and you can measure the amount of ray that comes out of this. |
|
| 108:10 | , we also measured the P wave shear wave and we found out there's |
|
| 108:15 | way to combine the P wave and wave. I think it was called |
|
| 108:19 | poisons ratio law. Oh my Look how similar it is to the |
|
| 108:25 | log. That poisons ratio curve is mythology. Why? Because that's what |
|
| 108:32 | gamma log the gamma log says here the share part and here's everything else |
|
| 108:38 | here. So we need an Remember the geophysicists, they're really |
|
| 108:52 | You know that geophysicists say if you write an equation for it, it |
|
| 108:57 | exist. Well, here we we need an equation. The first |
|
| 109:02 | we do is we write out what know, we know the normal |
|
| 109:07 | its reflection coefficient, we know that this is as an, as |
|
| 109:13 | as a variable that depends upon the angle theta and I don't have any |
|
| 109:21 | . OK? Put cosine square the , OK, we'll do that. |
|
| 109:27 | we need another portion and this one the difference in poisons ratio sine squared |
|
| 109:35 | and this is called the poisons As we're gonna find out your pore |
|
| 109:44 | analysis comes from this, your lithology from this. So how do we |
|
| 109:53 | other equations for that or how do use this? We broke this down |
|
| 109:58 | said, everybody can remember what the incidence equation is this, we call |
|
| 110:03 | poisons reflectivity. So you can't remember reflectivity. OK? I will help |
|
| 110:10 | . This is basically 2.25 times the in poison's ratio, the change in |
|
| 110:17 | ratio, it's always the lower minus upper the change in P wave |
|
| 110:23 | the lower minus the upper we went and asked you to do the A |
|
| 110:35 | based on this equation and you And a couple of things you noticed |
|
| 110:41 | curve is flat near the incident Uh This is an alert from the |
|
| 110:51 | of Houston campus. Fred's gonna put on the quiz. OK? That's |
|
| 110:56 | be on the quiz because you're gonna to draw this and when you draw |
|
| 111:00 | , you gotta make it smooth flat equals zero. Now, why would |
|
| 111:05 | do that? Because on seismic a lot of times the traces near |
|
| 111:13 | offset aren't any good. Well, says, OK, go out to |
|
| 111:20 | out to 10 degrees and you don't that. So you still got most |
|
| 111:27 | the information, you got all the so you can go out to 10 |
|
| 111:31 | . You don't have to force yourself take zero degrees. That's gonna be |
|
| 111:35 | good A vo is still very What other thing did we learn from |
|
| 111:42 | ? You're gonna need this too. is in one of the questions, |
|
| 111:45 | worth 30 points. You need to that the hydro garb the hydrocarbon charged |
|
| 111:53 | the same shape as the wed, the same close enough to us that |
|
| 112:01 | using the computer right now. Just this by hand. And it's more |
|
| 112:10 | negative is a amplitude. Amplitude is and minus. Don't get confused with |
|
| 112:17 | word magnitude. Magnitude is just, the absolute difference? We look at |
|
| 112:29 | up here. Let me see. see what this looks like here. |
|
| 112:34 | have a plus 0.05. That's this right there. The plus value in |
|
| 112:41 | curve goes down to the right and is the zero line oh at the |
|
| 112:48 | offset. It. Yep, it all amplitude. So this decreases empathy |
|
| 112:54 | offset and when we look at the , it says, well, it |
|
| 113:02 | has the same curve, right? look, I'm starting off negative and |
|
| 113:08 | curve is getting more negative. you start off negative, you get |
|
| 113:14 | negative, you increase, you're getting big amplitude here compared to the zero |
|
| 113:21 | . Oh Well, this is 0.05 this is minus 0.04. This and |
|
| 113:32 | or about the same 92. Fuck second term. That second term almost |
|
| 113:41 | is decreasing amplitude with offset. It's more negative. So I make this |
|
| 113:48 | negative. Yeah, it just gets in magnitude. It hasn't reached zero |
|
| 113:53 | . This starts negative, you make more negative, it becomes something easy |
|
| 113:59 | see what makes this visually attractive is a lot of time your amplitude at |
|
| 114:10 | offset has a very small value. this change in slope this and this |
|
| 114:18 | in slope, they're about the but this starts off as a positive |
|
| 114:27 | . This starts off as a And with your change in slope, |
|
| 114:32 | right there is a lot easier to against this and that right there against |
|
| 114:44 | . We said, let's look at field data. This is on Billy |
|
| 114:48 | Strander presentation. He said on the fill, you start off a small |
|
| 114:55 | , you get big on the far on the gas field. Here, |
|
| 115:00 | is a small offset with offset amplitude about the same. So our first |
|
| 115:15 | , this is what we saw this and I guarantee you, you need |
|
| 115:27 | know that equation that's gonna be on quiz several different times just to, |
|
| 115:34 | ask you what's your interpretation? The version of the equation. This version |
|
| 115:45 | here, the simplified version at the . That's the one just a simplified |
|
| 115:51 | . OK. Now you're also gonna , hey, reflection coefficient is a |
|
| 116:04 | of theta. You're gonna see something goes like this. The normal incidents |
|
| 116:13 | B sin square theta. The previous was normal incidents, cosine squared data |
|
| 116:32 | pr Science square. These are very related pr is simply related to |
|
| 116:47 | also different, just a different And we'll, we'll cover that. |
|
| 116:55 | need to know that. Let's take , ah, oh, go back |
|
| 117:04 | 20 minutes after three and finish We ordered pizza. Did you get |
|
| 117:14 | ordered? I just don't know about people over in Germany. Now, |
|
| 117:35 | all important media that we have to at. The one we do. |
|
| 117:40 | lot of exploration is water over Ok. Let's look, take a |
|
| 117:47 | at that. That's a fluid. waves don't propagate in water and they |
|
| 117:57 | propagate in jelly Jello either. But reflection coefficient at any incident angle can |
|
| 118:06 | expressed very simply as this right Now we do run into a little |
|
| 118:12 | of problems and that is once we past this critical angle, we get |
|
| 118:22 | of the zone where the face is longer zero, it starts to |
|
| 118:32 | What does that mean? That means reflection coefficient is gonna become imaginary. |
|
| 118:41 | gonna have a real part and then part and the relationship of the real |
|
| 118:51 | to the imaginary is how we get . OK. Now everybody used to |
|
| 118:57 | the trigonometry. They, they, , they, they got in high |
|
| 119:01 | and everybody remembers it right? Everybody that the inverse tangent and you, |
|
| 119:08 | got that function, you got that . By the way, on your |
|
| 119:15 | , the inverse tangent of the imaginary over the reel is equal to the |
|
| 119:21 | angle. So when we talk about , you have to come in |
|
| 119:27 | you compute this. But when you it, it can reach an imaginary |
|
| 119:33 | . Once it gets past say 32 here, now we can look at |
|
| 119:41 | you'd get out of it. And the PP reflection coming by this red |
|
| 119:46 | going up over all the way That's the P reflection based on this |
|
| 119:57 | , this plot right here. And know, it's about 32 degrees, |
|
| 120:03 | stops and maintains the amplitude of one the way across there. Interesting. |
|
| 120:12 | starting about 32 degrees right there, get a great big amplitude, it |
|
| 120:19 | up real fast. And yet when look at this, you say, |
|
| 120:28 | the high amplitude is way out not in here. And we will |
|
| 120:35 | what happened is there's another wave you barely see in here. And that |
|
| 120:41 | the head wave but it is coming and it gets bigger, bigger and |
|
| 120:47 | coming in here and you'll hear this and over. Not only do you |
|
| 120:54 | on this reflected wave, do you a P going down the P coming |
|
| 120:59 | ? But after a certain offset, get the refraction and that refraction superimposes |
|
| 121:06 | the conventional reflection, which is what drawing out. Said another way is |
|
| 121:14 | we look at it, the big is not necessarily gonna be at the |
|
| 121:20 | angle, but beyond. Now, does say something, it says after |
|
| 121:27 | incident wave, if this angle here bigger than 34 degrees right there |
|
| 121:42 | then there's no energy that goes into subsurface, everything greater than that is |
|
| 121:52 | reflect. Now, I wanna look this curve right here and I'm going |
|
| 122:05 | correct it, move it all the up to here. So that little |
|
| 122:11 | has been moved up to here and right here, I move it up |
|
| 122:16 | there. I, I do that what's called a static correction so that |
|
| 122:21 | should have the same wavelength all the across. Now. It's pretty close |
|
| 122:26 | the same wavelength right there. These all the same wavel thats but I |
|
| 122:33 | that wavelet it's distorted, it's not . This is a symmetrical zero phase |
|
| 122:42 | but not here. It looks like has a derivative or 90 degrees |
|
| 122:48 | Oh It says it's 63. So that particular angle we were at your |
|
| 122:57 | was 6063 degree. Well, no sitting in here almost close to pie |
|
| 123:04 | two. Yeah, the angle is degrees. So your reflection changed shape |
|
| 123:16 | you get past what's called the critical . Well, we don't have many |
|
| 123:21 | over fluid boundaries. We do have over solid though. Let's take a |
|
| 123:26 | at it. Ah Fred. Come . Oh All right. Let's take |
|
| 123:31 | . Here comes the P wave down the boundary. This is a ray |
|
| 123:35 | . The energy traveled down that ray , it hits the boundary and gazing |
|
| 123:41 | the old pool shooting pool angle, equals the angle of reflection. But |
|
| 123:47 | another wave that goes off. It's reflected she wa now P wave as |
|
| 123:55 | travels here, it grabs a hold a particle and moves it back and |
|
| 123:58 | in this directs the sheer wave, goes sideways. So when it continues |
|
| 124:05 | propagate, it grabs this particle and it sideways like that. Yeah, |
|
| 124:12 | wanna see a good P wave I mean, a sheer wave, |
|
| 124:17 | some salt on the table, make shrill on the table with salt. |
|
| 124:23 | take a piece of sandpaper and glue to the front side of the |
|
| 124:30 | then take not your fingernail. you could use a scrape down on |
|
| 124:35 | sandpaper. So you're creating an up down motion and watch the salt travel |
|
| 124:42 | , but it goes up and down the wave travels down there, not |
|
| 124:46 | and forth. So there's a sheer . It's actually more of a |
|
| 124:51 | but we'll call it a sheer. I transmitted a sheer wave P wave |
|
| 124:58 | wave shear wave. Wow, we we, we know we have a |
|
| 125:04 | in the group and a physicist as . We got to somehow tell what |
|
| 125:09 | amplitude is. What do you want know? Well, all these |
|
| 125:17 | one reflected cheer, two reflected P P transmitted. I wanna know what |
|
| 125:25 | , if I give an amplitude of over here, what does it |
|
| 125:29 | Well as you know, we use is something we're gonna continuity, |
|
| 125:36 | continuity of stress. When we get with that for P wave and she |
|
| 125:43 | , we would have four equations. so these are the unknowns do, |
|
| 125:49 | do these. This is all this is all known. So we |
|
| 125:56 | real numbers or imaginary numbers throughout this yellow box and throughout this whole white |
|
| 126:05 | that when you try to solve these using algebra, this is not a |
|
| 126:24 | problem. You're gonna want a computer this, but it becomes a really |
|
| 126:30 | little problem. So somebody did it us. A guy by the name |
|
| 126:41 | and Rev Rendra and they published Zr's . This is Carl Zep. Now |
|
| 126:49 | going to give us the exact, see, everybody's forearm, show me |
|
| 126:56 | forearm. You have that equation written reflection coefficient, the function of |
|
| 127:03 | Let me hear it again. It's of like a football game. You |
|
| 127:07 | , you gotta get the team in locker room, go, team, |
|
| 127:09 | team. Yeah. OK. Reflection is equal to normal incident cosine squared |
|
| 127:17 | plus coones reflectivity sine squared data. an approximation. You can do it |
|
| 127:23 | your head. But Carl Zeren 1990 , no, no, no. |
|
| 127:29 | me give you the exact solution. he said if you wanna find a |
|
| 127:36 | reflection going down right in here as function of the P wave velocity, |
|
| 127:42 | wave velocity and density of the upper lower medium. Here's the equation you |
|
| 127:46 | to have. Oh, that's not bad for it. I mean, |
|
| 127:50 | some date, isn't it? you got ad minus one there minus |
|
| 127:56 | means divide by. OK. so before you do all those |
|
| 128:02 | you gotta compute D oops. Now gotta do all these multiplications for D |
|
| 128:08 | By the way before you d before do DC, these status and |
|
| 128:14 | you gotta do that first. So , you've done two separate things before |
|
| 128:21 | can actually get this number right This is very easy to put in |
|
| 128:27 | . By the way there, it's not simple. It might take |
|
| 128:32 | a day just to figure out remember to use complex numbers, but it's |
|
| 128:38 | to program. And if you want program the P going down over the |
|
| 128:49 | , that was the previous slide And if you wanna complete the P |
|
| 128:55 | down and the sheer going up, subscript one too, that's this one |
|
| 129:02 | here. There's what you need to . And as it turns out there |
|
| 129:08 | 16 different ways you can have a wave going down or shear wave going |
|
| 129:16 | or P wave coming up and or you could have the transmitted |
|
| 129:23 | So these are all the various scenarios you can have the red we |
|
| 129:33 | that's the PP, let's do Simple examples. Here is the model |
|
| 129:46 | this is the ju just so, know, we don't have some of |
|
| 129:51 | slides too. So I think there's issue with the hidden slides in a |
|
| 129:56 | of these sections. OK. What that was was I put those |
|
| 130:04 | uh h when I made the PDF again, I came through and uh |
|
| 130:16 | , oh, I'll show those anyhow I have time. Um This is |
|
| 130:24 | , 3.4. OK. We will those to you. I hope there |
|
| 130:35 | been too many. Has there been lot? Uh It's not a ton |
|
| 130:41 | there's, they've definitely been scattered throughout different sections. We're surviving. All |
|
| 130:50 | . Do you have this one? , this one, this one that's |
|
| 131:03 | there. It is there or No, that one. Mhm. |
|
| 131:13 | . No, I think the previous . What's that? The, the |
|
| 131:19 | one? I think it was Yes. Yes, we have |
|
| 131:29 | Let me, let me tell you you missed. OK. You'll |
|
| 131:42 | you'll get that. I, I . Here's a model and here is |
|
| 131:53 | amplitude, I should say magnitude and angle and look how it goes |
|
| 132:00 | down, back, down, All right. This is all very |
|
| 132:06 | . But then again to over here look at what the model is. |
|
| 132:12 | 10,000 ft per second, over 25,000 per second. That's like cream cheese |
|
| 132:20 | top of stainless steel. It gives a sh this would be your shot |
|
| 132:29 | out and function of offset shot You move that up, take the |
|
| 132:40 | that's here, you move it That'll be over here. So flattening |
|
| 132:47 | , it's called Norma Mova. But move this up with a static shift |
|
| 132:52 | I don't stretch it and I get shown right in here. I guarantee |
|
| 132:59 | never see this. I mean, order even to do this in the |
|
| 133:05 | model, it takes a lot of to get rid of all the other |
|
| 133:12 | that's gonna be there. There's stuff here that only theoretically is is what |
|
| 133:18 | gonna drive. And that's why I to this. This is more |
|
| 133:24 | It has a P wave of over 13,000. The amplitude decreases with |
|
| 133:31 | . Here's the critical angle and it at the critical angle, you get |
|
| 133:36 | high amplitude sitting out there, I at the model and here is the |
|
| 133:42 | angle right here and there's absolutely no amplitude there. Your big amplitudes out |
|
| 133:50 | . Where's the big amplitude that Carl told us is gonna be there? |
|
| 133:57 | If you look closely there is the weight, the refraction coming in coming |
|
| 134:04 | and it starts right there at the at the critical angle. And as |
|
| 134:11 | turns out, it has a different than the flat event right here. |
|
| 134:17 | therefore the amplitude is not maximum the maximum is back there. So |
|
| 134:23 | idea that critical angle as the maximum , that's correct. If he didn't |
|
| 134:29 | the head wave coming in which it's always gonna be there. You |
|
| 134:34 | separate it physically, physically, it's . I can separate it because |
|
| 134:39 | I'm plotting these one ray at a PP reflection. I could then do |
|
| 134:45 | P headway. So did you have plot? He had this plot? |
|
| 134:59 | . This is Zebras solution and that by uh Excel. And then this |
|
| 135:17 | using a code called the reflectivity That means everything is computed headways surface |
|
| 135:28 | everything. So that head wave and reflection there come about to say at |
|
| 135:35 | critical angle, your total elastic This red says your maximum amplitude is |
|
| 135:44 | there almost twice, not twice but further out than at the critical |
|
| 135:52 | What do I get out of Fred? What you get out of |
|
| 135:56 | is this right here? And this where people that do a vo oh |
|
| 136:05 | me the far offset. I'm gonna you. Yes, again, this |
|
| 136:13 | from this green to this green cannot used for a vo. In other |
|
| 136:20 | , this amplitude going up cannot be to predict because it has the head |
|
| 136:29 | . Well, Fred, you went critical A yeah, your head wave |
|
| 136:35 | does come in before because it's a band that you're measuring. So you |
|
| 136:44 | use it until this distance out here the head wave refraction and the reflection |
|
| 136:59 | time or you come back in here the amplitude starts going up. So |
|
| 137:09 | no way to process out the head . E I I wish I could |
|
| 137:18 | yes. But you see the head is coming in right over top of |
|
| 137:28 | reflected wave. I I, you then the, the head wave, |
|
| 137:41 | you look at the seismic reflection, head wave comes in here, it's |
|
| 137:49 | . This is the reflected wave time down here offset going across there. |
|
| 137:55 | is the reflected wave, this hyperbolic it's ta the refraction is tangent to |
|
| 138:03 | reflective. And when you say you say I suck, I can't |
|
| 138:07 | that. There's no time there's no offset separation. So you have to |
|
| 138:16 | predict it, which I can't No, I don't, I don't |
|
| 138:25 | what, what it leads to is talk about being able to separate velocity |
|
| 138:34 | from density by looking at the very offset. And the answer is you |
|
| 138:41 | , that portion is, don't go . The headway screwing you up. |
|
| 138:54 | we? We didn't pass any did we? We had two |
|
| 138:59 | haven't we? Yeah. Yeah. . OK. Good. All |
|
| 139:07 | I think it's Newton's time. I picked on him yet today. Are |
|
| 139:11 | ready? You're a mathematician. What you shaking your head? You are |
|
| 139:19 | , I just told you a you gotta see what these people had |
|
| 139:23 | be. OK? Here it Newton, everything, everything in here |
|
| 139:34 | gonna be a number, everything right . It's gonna be a number. |
|
| 139:42 | ? No, your job as a is to be able to predict what |
|
| 139:52 | reflection would look like if it's bri versus if it's gas. That's |
|
| 140:00 | So that means the density and P velocity going from Brian, the gas |
|
| 140:10 | are gonna be reduced by about And in doing that, going from |
|
| 140:20 | to guess how much will RP vary reflected P wave? The question |
|
| 140:30 | is there any insight gathered from the equation which I display here? In |
|
| 140:38 | to answer this, please don't say and make me feel bad. I |
|
| 140:45 | see any. It's, it's, an ugly question for it. So |
|
| 140:50 | we have to do is ask our Reinhardt BFD and this goes back to |
|
| 141:05 | sixties or so, German professor. here's this equation, I simplified it |
|
| 141:13 | bit but uh modified it slightly. said, if you want to look |
|
| 141:22 | a PP reflection, you can go and use Carl Z's equations. He |
|
| 141:31 | , but let me give you a method. Now, in 1960 we |
|
| 141:37 | didn't FP CS, we didn't have , main computers. So he's doing |
|
| 141:43 | by hand. He basically says, that I'm making a simpler solution. |
|
| 141:49 | is too bad, man. I'm gonna do many. And so |
|
| 141:52 | he comes up with this approximation, interesting thing is we look at this |
|
| 141:59 | approximation. That term I saw that water over jello. You know, |
|
| 142:07 | the fluid fluid part. And what this? That's the rigidity part? |
|
| 142:14 | I'll be darn what does the word mean to you? Oh, I |
|
| 142:20 | there was a, there was a coefficient friend. The sheer wave of |
|
| 142:28 | , I think it was called sheer . Oh Is that why I'm seeing |
|
| 142:34 | these beta in there? Yeah, got a little Alpha Don here. |
|
| 142:40 | that's, that's immaterial there. this term right here. Al |
|
| 142:50 | Look at that. That is with . It says this term right here |
|
| 142:59 | what you're gonna use with offset depending contribution. OK? We can do |
|
| 143:07 | interesting. Do you have these OK. No. Did everybody bring |
|
| 143:24 | sand and chill ba trends with What are you talking about, |
|
| 143:28 | Well, you got in, you're into a new area. You tell |
|
| 143:33 | what the rock properties are as a , you know, rock property says |
|
| 143:39 | wave velocity and density. If I to do sheer a velocity, I'll |
|
| 143:45 | it. I'll use the Greenberg Gusto equations that you showed a little bit |
|
| 143:50 | . OK. So you go ahead you're gonna pick three different depths in |
|
| 143:57 | three different depths. We review cast and three A vo you don't know |
|
| 144:04 | they are, but they are So here are the properties of the |
|
| 144:11 | and density. Ok. Now, break this up into team, we're |
|
| 144:19 | compute the A vo response as a exercised using this equation. Who knows |
|
| 144:33 | one? Anybody else who in out of the world? Oh, |
|
| 144:39 | just out of Houston. Who knows Taylor? Ok. Taylor, you're |
|
| 144:47 | team captain from away from home. of this SD Friday night lights or |
|
| 144:58 | they call that movie. Ok. the team captain. He, he |
|
| 145:08 | out 70. You're always answering the , right? Don't pick on |
|
| 145:17 | Fred. You're the team captain. ? I'll be the team captain for |
|
| 145:25 | three. Who wants to be on team anybody? No, you can't |
|
| 145:31 | on my team. Stephanie, you're , you're on team one. |
|
| 145:35 | that's ok. Don't worry, I this underhand. You ready? Here |
|
| 145:40 | goes. So what I want you do? Hey, there, are |
|
| 145:50 | ready? See this equation, I want you to compute the fluid |
|
| 146:08 | . I want you to compute that this class two is 9000 ft |
|
| 146:26 | They are the rock properties that you're have. And now here's your equation |
|
| 146:36 | gonna use. So when you go , they want, oh, by |
|
| 146:41 | way, you could do this 50 from one degree to 51 degrees. |
|
| 146:49 | you have just p way density lower medium. OK. Stephanie, you |
|
| 146:57 | your team, you got the whole , you and your team are gonna |
|
| 147:02 | the rigidity factor for 51 different 0 to 50 Tessa is gonna help |
|
| 147:11 | . She knows Python, are you only one? Nobody else is raising |
|
| 147:19 | hand but they know Excel and that work too. Ok? So let's |
|
| 147:26 | ready. No, Taylor, you figure out how to do this. |
|
| 147:32 | the commander there, Stephanie, I turn around and start looking at |
|
| 147:38 | group see if they're gonna help OK. Anybody done yet? |
|
| 147:58 | Let's have the group now time to your data in Taylor. You're in |
|
| 148:03 | of the fluid part, right? . So for that 9000 ft depth |
|
| 148:10 | just sent me an email and he me these values right here. That's |
|
| 148:16 | fluid term for Bord Fell. Stephanie, she just handed it to |
|
| 148:23 | . The rigidity term had hardly had time to get this done. |
|
| 148:29 | Bor Feld says my total response is sum of the blue in a |
|
| 148:37 | So add these together. I get brown. Do you have a copy |
|
| 148:41 | this? You should have a copy them. You have the brown curve |
|
| 148:45 | in the middle now just behind or that is a black line. That's |
|
| 148:52 | exact Z. Hey, that's not . I mean word fell's approximation. |
|
| 148:58 | exact Z are almost overlays not bad all. But here we go |
|
| 149:07 | Geoscientists what you're greedy then why are greedy? Because you say what is |
|
| 149:14 | enough. Let's do the gas So get ready ta them. I'm |
|
| 149:20 | need your term for the gas, fluid term. So, oh here |
|
| 149:24 | his email. Let me get So here's the first one Taylor gave |
|
| 149:29 | for the web. Oh Look at the fluid term went down to this |
|
| 149:34 | curve over here again. Stephanie, gonna give me the rigidity to? |
|
| 149:42 | . So give me the rigidity. , hey, hey, just a |
|
| 149:48 | . Stephanie, that's the same thing you gave me before. Come |
|
| 149:53 | Now we asked, you're, you're me that the rigidity term for the |
|
| 150:03 | is the same as the rigidity term the what? Uh let's go back |
|
| 150:12 | . Yeah, Fred, don't you sheer wave velocity isn't affected by what's |
|
| 150:19 | the portal much at all? So of a sudden these are about the |
|
| 150:26 | for gas or for what that Discrimination lies in this poor fluid |
|
| 150:39 | Oh my gosh. And what is ? That's the normal incidence term. |
|
| 150:45 | where the poor fluid discrimination is not avi re interesting. So, rigidity |
|
| 150:59 | is identical for wet and gas The fluid response identifies the poor fluid |
|
| 151:07 | bingo. We can go up now collect our price. Now we'll do |
|
| 151:13 | same thing for the board F class . Here is the two terms and |
|
| 151:23 | , on the wet. Look how bra, that's the total response and |
|
| 151:30 | fluid just about overlap. I come here to the gas again, the |
|
| 151:42 | and Bord Feld's total expression overlap. rigidity term is about the same sitting |
|
| 151:50 | here. No, this has It means something does lapse. It |
|
| 152:00 | that, oh, and this is a bright spot. They called class |
|
| 152:08 | . We're gonna find out it's a amplitude. Mm. It says those |
|
| 152:15 | amplitude you see, look at that compare that to this over there. |
|
| 152:19 | mean, that's 20 times bigger. gonna be so big. It's gonna |
|
| 152:23 | a hole on your monitor screen. will come through so much. |
|
| 152:35 | Isn't that interesting? It says these spots that you're looking at, they |
|
| 152:42 | care what the rigidity term is. basically kind of flat. Wow, |
|
| 152:52 | means those bright spots or like fluid fluid type of the terms rigidity is |
|
| 153:00 | needed. Interesting. OK. Let's a look at those that are very |
|
| 153:11 | . Now, the deep ones at good separation between the velocities 24,000. |
|
| 153:26 | remember linear approximations probably has some assumptions with it. And what are those |
|
| 153:37 | ? There's not a big change in wave, there's not a big change |
|
| 153:40 | density, simple stuff. What's not big, well, going from 10 |
|
| 153:48 | 14,000, that's a 40% change. big. What does that mean in |
|
| 153:55 | linear approximation? Well, has a of an important thing for us. |
|
| 154:01 | it says if you look at 14,000 depth, the Bord Feld's response is |
|
| 154:11 | brand. Now, look at the right here compared to the exact |
|
| 154:24 | And let's put the gas in it see what that has there. There's |
|
| 154:28 | board fill and there is a ZR Fred. They're not off by much |
|
| 154:37 | maybe 0.03. That's not my is . You don't have the slide. |
|
| 154:50 | the one this year. 0000 I know. OK. Once |
|
| 155:03 | muscle. Um Don't have animation on slides. God, you gotta, |
|
| 155:18 | gotta put every animation. OK? attention to my little thought. That's |
|
| 155:27 | one I have to do. It says that Fred, don't worry |
|
| 155:35 | that. It's only 0.02. There's , I mean, look at, |
|
| 155:45 | much different than this. Much different that. What more do you |
|
| 155:51 | Well, but more I want is want you to look down here at |
|
| 155:58 | and I want you to go back what you read on Rutherford and |
|
| 156:02 | And what did they say? We're Oklahoma, we're drilling for the hard |
|
| 156:09 | in the hard shore. What we for is when the amplitude in the |
|
| 156:14 | goes to zero. Yeah. So amplitude I'm following this event. Seismic |
|
| 156:21 | event. All of a sudden it and you tell me to drill. |
|
| 156:27 | , no boss is gonna drill where amplitude disappears. The plude is supposed |
|
| 156:32 | increase when you get hydrocarbons, not what we're seeing here. It |
|
| 156:39 | but more importantly, what happened? came da and goes through the zero |
|
| 156:50 | . It reverses polarity on the CD . Gather that multitrace set of data |
|
| 157:00 | represents one trace. When you stack together, you have an area or |
|
| 157:09 | amplitude is going to go through zero here. The real data says you |
|
| 157:16 | go through zero, your amplitude Well, that is a great and |
|
| 157:21 | show you real data in a little on where that's significant. It tells |
|
| 157:27 | where to drill. So you gotta the exact solution. The conclusions here's |
|
| 157:41 | that we can reach. First conclusion it's time for a break. Let's |
|
| 157:46 | about a five minute break till we to about 10 after four. All |
|
| 158:05 | . Conclusions from Reinhardt Borel. They hate to keep saying this but the |
|
| 158:17 | are on the quiz. Uh and Ron Quist, the class three which |
|
| 158:27 | are going to call bright spots. rigidity term is small in fluid fluid |
|
| 158:34 | dominates for those of you. that are in processing. It says |
|
| 158:44 | implication, Avio is approximately flat for and hydrocarbon saturates. What does that |
|
| 158:58 | when you're processing seismic data? There's a problem. How do you balance |
|
| 159:04 | traces? How do you balance the offset compared to the near offset? |
|
| 159:11 | , what this says is dominant at that you can see. They should |
|
| 159:18 | the same amplitude magnitude going from near far on a class three bright |
|
| 159:25 | So if you know you're in class environment, you're gonna do this. |
|
| 159:30 | a little bit tell a little bit , we tell you what is a |
|
| 159:35 | three environment based on your velocity profile on what you can see in seismic |
|
| 159:45 | if you get a large increase or in the A vo and you |
|
| 159:52 | you're in a class three environment. class three? Basically, it means |
|
| 159:59 | velocity is less than seven or 8000 per second. When you're 7 8000 |
|
| 160:05 | per second interval, velocity expect to in class three. So any large |
|
| 160:11 | or decrease and the A vo not brighten the increase expect that that's not |
|
| 160:19 | shall, that's gonna be salt, gonna be limestone, it's gonna be |
|
| 160:23 | else. The stack provides the most estimate of poor floor. That's |
|
| 160:37 | Well, of course, if you this, if you're expecting the same |
|
| 160:42 | on every trace stack, it that your signal to noise ratio. |
|
| 160:48 | who ever say something like that? That was a as it turned out |
|
| 160:53 | is a fly by night company Shell that actually wrote this paper. So |
|
| 160:59 | wants to believe shell, very good and it's very basic and a lot |
|
| 161:05 | good God. It's actually called stacked ac ked stack. And uh I |
|
| 161:13 | I gave you a copy of them linear approximation equation namely tips. |
|
| 161:24 | log Maler tips in Bend Mahler works . We're near in class 20 By |
|
| 161:32 | way, look at the bottom this is an example, you have |
|
| 161:38 | wet small amplitude gas bait. So your stack section, you're gonna see |
|
| 161:44 | that burns right through the monitor, amplitude flat amplitude. Now, in |
|
| 161:50 | class two, often called phase this was the 9000 ft depth. |
|
| 161:59 | we looked at the wet response, amplitude died with offset. When we |
|
| 162:04 | at the gas, it increased with . Just looking at these two |
|
| 162:11 | Would you be able to say one's magnitude and the other, you |
|
| 162:15 | even looking at it, would you , oh, that's negative and this |
|
| 162:18 | positive or vice versa, this is and that's positive. Would you see |
|
| 162:25 | ? I don't know, but I would notice this. I sure would |
|
| 162:31 | starting with zero offset to the far here and that amplitude decreases and here |
|
| 162:38 | amplitude increases. I would not miss . So that definitely is a very |
|
| 162:45 | idea. This is what Bill Ostrander talking about, having been able to |
|
| 162:55 | the amplitude increase like that Avio rigidity . One here it is the rigidity |
|
| 163:13 | has the same weight as the fluid . The fluid fluid term must be |
|
| 163:22 | from rigidity to say it. Another you gotta be able to get what |
|
| 163:27 | normal incidence is. You gotta be to get how the amplitude slopes with |
|
| 163:32 | two important features. You gotta get AVIA was invented for class two. |
|
| 163:39 | prospect might not even be recognized on stack section. So you gotta have |
|
| 163:44 | type of Avio modeling or it's Avio in class one rigidity term dominates the |
|
| 163:59 | fluid term Avio decreases with offset. looked at the wet Avio decreases with |
|
| 164:09 | . We looked at the gas Avio with offset. The linear approximation equation |
|
| 164:16 | inadequate. We're going to have to the full lasted. We need more |
|
| 164:25 | than conventional Avio attributes. Well, , we try to show one and |
|
| 164:33 | is on the what case if you the amplitude magnitude was approaching zero. |
|
| 164:44 | is a CD P gather and we at the amplitude of magnitude. It |
|
| 164:51 | from my gosh, it went from to minus over here. That's a |
|
| 164:58 | on the timing line and that's plus got a zone of excuse me, |
|
| 165:08 | phase reversal or reverse polarity. This our big signature where we need more |
|
| 165:16 | . That is one way. This what Rutherford and Williams, you're talking |
|
| 165:23 | looking for the dead zone. the Avio equation mathematically those of you |
|
| 165:34 | Excel very simple to program. Let's at each term delta alpha. What |
|
| 165:44 | delta mean? Delta means change in PD wave or whatever property it means |
|
| 165:54 | minus upper, lower minus upper, minus upper density P wave velocity. |
|
| 166:03 | does row mean? What does alpha itself row alpha sitting by itself are |
|
| 166:11 | properties if you see alpha by that means the P wave of the |
|
| 166:17 | medium plus the P wave of the medium divided by two. OK. |
|
| 166:24 | is the, what is PP is incident angle? Ding ding ding alert |
|
| 166:32 | Houston. This is your Houston City sending an alert message. Watch out |
|
| 166:38 | theta you notice incident was fee, don't have fee there. You have |
|
| 166:46 | though the the is the average of incident and the transmitted absolutely essential that |
|
| 166:58 | go there because what will happen for in literature, we saw these big |
|
| 167:05 | on the far offset. They were false because they didn't use the average |
|
| 167:21 | you, you have, you come here with the large Anglesey and then |
|
| 167:29 | it might be a short angle and it goes to a big angle |
|
| 167:37 | So this might be the incident angle but the theta is you take the |
|
| 167:44 | angle and then this lower angle right there you take the average. |
|
| 167:50 | isn't that the same down here? , they're just kind of reversed but |
|
| 167:55 | average angle, the top and the are the same. So what does |
|
| 168:01 | mean? Well, let's come up the top and take a look delta |
|
| 168:10 | . What's delta row? Let's consider top interface, delta row would be |
|
| 168:19 | two minus row one. OK. about this boundary? Oh, it |
|
| 168:28 | still be the lower minus the Oh, but that's just opposite. |
|
| 168:34 | other words, that might be plus the talk, but it would be |
|
| 168:40 | minus for the bottom if you happen have medium one, medium two, |
|
| 168:51 | one again, shill upon shill. this might be plus delta row, |
|
| 169:00 | this would be minus delta road, same for delta alpha, delta beta |
|
| 169:07 | delta right there. These are averages here. So it doesn't make any |
|
| 169:14 | . All of a sudden you can they were reflection coefficient for the upper |
|
| 169:23 | is equal to the reflection coefficient of lower bed with the minus sign. |
|
| 169:33 | this means is as your two reflections closer, closer, closer and closer |
|
| 169:42 | as they get closer, they merge they go to zero because the upper |
|
| 169:50 | coefficient is equal to the minus the . And so as they approach one |
|
| 169:55 | , you get zero reflection, add together. They're at the same location |
|
| 170:02 | it wasn't there, there was always residual left over. Now comes a |
|
| 170:12 | by the name of Ralph Shy Ralph a research geophysicist at Gulf Oil Armor |
|
| 170:20 | . Beautiful time. He said I where the other people like their |
|
| 170:30 | So, but I I'm gonna give something a little bit different. And |
|
| 170:34 | way I present it is a way geoscientists would like, cause I'm gonna |
|
| 170:43 | you what constitutes the amplitude from the traces, what constitutes the amplitude from |
|
| 170:52 | mid and afar? I want to you that this is the acoustic and |
|
| 170:58 | on the air traces the mid to ratio. We already know that because |
|
| 171:04 | pr or so's reflectivity and the far a function of the P wave |
|
| 171:10 | So let's see what that means. said, if you go ahead, |
|
| 171:19 | competes, goes from 0 to 9 . Poison starts at 15 and goes |
|
| 171:24 | 90 pw 30 good. What do mean from? Look at the low |
|
| 171:29 | here, you see angle of zero right along this. So your 10 |
|
| 171:34 | angle of incident fall something like You're 15 degree lower like that and |
|
| 171:42 | maybe you're 40 degree out like something like that. And then p |
|
| 171:51 | for the very far offset. Isn't interesting at the farther offsets? Look |
|
| 172:00 | this garbage that's coming in. What that? They all hydrocarbons? |
|
| 172:08 | let's, let's take these far Take a look at those, put |
|
| 172:15 | in the middle, here's the the P wave velocity and this is |
|
| 172:23 | middle term and I, I put resistivity curve right beside it and this |
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| 172:29 | typical Gulf coast and every time you a resistivity that's lower than the other |
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| 172:36 | that's a sand. Sand has lower than the shell. So every place |
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| 172:42 | a sand, the resistivity changes look , oh, that's hydrops. Look |
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| 172:48 | that. Every time I got a sand, the middle term in Chuy's |
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| 172:54 | has a big amplitude. Well, be darned. That's interesting. |
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| 173:02 | let's look at how we apply This is Australia and I'm looking at |
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| 173:12 | and I see this term right That angle, that event is not |
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| 173:19 | the near offset. This goes from to 2400 m and there's nothing on |
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| 173:26 | near offset for that reflection. this doesn't have anything on the near |
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| 173:34 | what is happening here. But we're go back and take a look at |
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| 173:41 | . This is the normal shale curve yellow or sands, grayer shells. |
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| 173:55 | replace all the sands with shale. I replaced them. Look at that |
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| 174:02 | shall, right. OK. Compared the previous right? No, let's |
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| 174:10 | at three regions right here. The mid and far. What happened |
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| 174:21 | Look at this song right here. at that song. When I put |
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| 174:31 | of sand and shale, you get here go like yeah. Holy mackerel |
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| 174:38 | telling you, it says that there a difference between sand and shale and |
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| 174:48 | gives you your poisons ratio difference in middle. No, I make it |
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| 174:55 | sand, I don't think don't have sly. There is all sand and |
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| 175:02 | , there's nothing in the middle. the difference in mythology. They give |
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| 175:07 | the reflections. Hey reflection coefficient function theta. You think what I'm supposed |
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| 175:15 | remember? Cosine squared and N I the difference of poor sos ratio, |
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| 175:23 | part of the poison reflectivity. That's it's said. The difference of poison |
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| 175:28 | . The different lithology Poisson's ratio gives mythology. OK? Some thin bed |
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| 175:44 | . This is a graduate student You ready? I challenge you. |
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| 175:55 | ? I wanna do this modeling. is real earth. Well, almost |
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| 175:59 | earth. Real earth and French make mind. Ok? But don't look |
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| 176:04 | your, you got the answer on . No, no, no. |
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| 176:08 | at that. How do you get single reflection all by itself? What |
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| 176:16 | your earth look like? I just one reflection pp tell me what your |
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| 176:23 | is. So I it's acoustic Did anybody know what the word acoustic |
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| 176:32 | ? We talk about modeling? No wave velocity, shear wave velocity goes |
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| 176:37 | zero. Acoustic is air sheer doesn't in air. OK? Acoustic but |
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| 176:43 | good. I'm not gonna thank you . You're not done yet. You |
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| 176:49 | to tell me where's the source and . OK. What type of receiver |
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| 176:54 | you have? That's what explosive thoughts like 51 it's like what kind of |
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| 177:07 | or an explosive source. OK. type of receiver do you have? |
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| 177:14 | It's a matter what? Well, it's a hydrophilic matter wouldn't it. |
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| 177:20 | if you had a hydrophone sitting out , when the explosion goes off, |
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| 177:27 | gonna get a direct arrival. You have a direct arrival on this |
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| 177:33 | Oh, so any better help how get rid of the director of? |
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| 177:48 | trying to take a peek at his . That's ok. It took me |
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| 177:51 | though. You have vertical geophones. if you have a vertical geo filme |
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| 177:59 | the energy comes sideways, theoretically, phone doesn't move. Now, let's |
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| 178:12 | the explosive source and geophones are on surface of the ground. We got |
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| 178:19 | problem. We got an airwave, ground rule, maybe. So what |
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| 178:33 | we do? We make this an medium? In other words, it's |
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| 178:42 | made up of a sand that has share way velocity but then somewhere in |
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| 178:50 | he cannot make up little hole in and put your earphones in the receivers |
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| 178:57 | the same de say it another way it, you have this model where |
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| 179:04 | of air, it's replaced by the weathering zone all the way up to |
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| 179:09 | middle air is replaced by solid This is what you get, |
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| 179:14 | OK. So looks like this, have source. Now let's go ahead |
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| 179:25 | the next one and move the source a little bit. So it's no |
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| 179:35 | on the surface and air replaces that that went to the moon. Now |
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| 179:44 | what you get, you get a arrival coming in and you get your |
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| 179:53 | again like you had before. But you're beginning to see a head wave |
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| 180:03 | across there very faint. But at critical distance there begins the head wave |
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| 180:10 | in this event right here is done to back a multiple very heavy out |
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| 180:23 | , big amplitude. But here's the angle. What what they do way |
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| 180:29 | there. Let's you take a look that. Remember that critical angle, |
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| 180:38 | reflects with the amplitude of one. magenta re going down there, we |
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| 180:48 | the critical ray. That angle right at angle is a critical angle. |
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| 180:55 | if I come down with an amplitude one, I reflect up with an |
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| 181:00 | of 0.3. But the white ray coming from the dynamite source, it |
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| 181:05 | its boundary, it reflects with a of one. Now another multiple, |
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| 181:12 | ray that started inside this critical it bounces again comes off of minus |
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| 181:19 | bounces here. It's 0.09 but the one still maintains an amplitude of |
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| 181:26 | And so for it, everything all a sudden that's going along the surface |
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| 181:32 | gets gigantic amplitude while the multiple decreases time this is the trapped energy. |
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| 181:42 | the low velocity zone. That's the I told you about all the low |
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| 181:46 | zones that we have in our Now, they're called leaky modes and |
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| 181:58 | modes, the leaky modes or all where the race starts inside this magenta |
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| 182:07 | , the trap modes, obviously they're , they have big amplitudes. So |
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| 182:13 | we look at our record again, are are multiples. And here, |
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| 182:26 | are the P one P one P means in the first layer P down |
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| 182:33 | back up two P one means P P one P one P one. |
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| 182:39 | this is a little different P one two. So you get down in |
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| 182:44 | one layer you travel in the second and up in the one layer. |
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| 182:48 | what that means. You can see various headways. No, not |
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| 182:56 | Here's the interesting one. This line down here which is associated with a |
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| 183:04 | called the pre critical. Look at amplitude inside on the far traces big |
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| 183:12 | , but look inside the leaky You have this tremendous amplitude sitting out |
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| 183:19 | . Yeah. By the way, tremendous amplitude because it was called your |
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| 183:25 | waves. Now, we do everything same except to go from the |
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| 183:34 | we go to the elastic. I have a sheer wave. Lets |
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| 183:41 | e who look at all the extra I'm getting. Wow. Just because |
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| 183:48 | added the other velocity. Oh Now you're getting sheer type of a |
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| 183:56 | that's A P going down, maybe , going back up and so |
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| 184:02 | So all of a sudden what we off with the simple model, all |
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| 184:08 | gotta do is add air, give elasticity. And all of a sudden |
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| 184:13 | got this boundary of rays coming in yet they're very simple. The geology |
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| 184:22 | is so simple and look at all noise that you get unbelievable. Let's |
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| 184:32 | you the difference between ray theory and . This is the Gulf of Mexico |
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| 184:40 | Canyon, deep water. And this the ray theory solution. Ray means |
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| 184:49 | gotta send a ray down, keep of which of our bets and keep |
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| 184:54 | of the amplitude coming up. When compare that to the reflectivity, which |
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| 185:02 | the elastic model, these two look good with that compares very nicely to |
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| 185:10 | . And a lot of care has go into the ray theory to make |
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| 185:16 | look like the reflectivity model. But than that, you have to have |
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| 185:24 | sediments to illustrate that if you have sentiments, you you normally have the |
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| 185:33 | any reflectivity the same. Say it way you can believe you're modeling, |
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| 185:39 | can believe tips modeling. But if go to more consolidated sediments, there's |
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| 185:48 | ray theory on the left and there's reflectivity all of a sudden they match |
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| 185:59 | where they're unconsolidated. But when you to big reflection coefficient, everything goes |
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| 186:07 | just really big, very bad. , to show you the difference. |
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| 186:15 | an elastic, this has sheer wave in there. This is the |
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| 186:23 | there's no sheer weight in here. how clean it looks, look how |
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| 186:30 | you get in here if the sheer goes to zero and I give you |
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| 186:36 | elastic mono acoustic, all the all this noise, it's from the |
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| 186:48 | way. Think if we could understand that noise really means, think of |
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| 187:00 | we could define our real earth. , there's just a lot of energy |
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| 187:06 | there that we are not able to it, decipher it. What do |
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| 187:15 | think we'll ever be able to do ? I don't know. Maybe A |
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| 187:19 | one of these days would be something would help, but there's still something |
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| 187:24 | to aim for in our computer I told you what Carl Savit said |
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| 187:32 | time, he was a scientific advisor one of the presidents, Executive vice |
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| 187:45 | for Western Geophysical. Uh Everybody still combat. There's not a computer system |
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| 187:53 | can be built that a geophysicist won't it to its knees. We will |
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| 188:00 | make it so we can handle our . And I guess we're kind of |
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| 188:07 | . Now, when you look at kind of recording that Saudi Arabia |
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| 188:16 | when you look at the fact that have 24 vibrators going simultaneously, the |
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| 188:25 | never stops. They have to take data. It consists of 24 different |
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| 188:33 | located all the way around your Sir. They do what they call |
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| 188:38 | lend them. In other words, a record for each one of those |
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| 188:43 | . What is the record? 5 100,000 channels. You have 500,000 receivers |
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| 188:50 | their drive. You have 24 So every 28 seconds, 30 |
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| 188:59 | you're getting another 500,000 records that have be de blended, broken apart. |
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| 189:10 | only process the data one time. can't afford to do it. I |
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| 189:16 | can't make a mistake and they can't a lot of the today's current |
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| 189:23 | It's just too expensive. It, brings the computer to its knees. |
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| 189:32 | . I have the n tomorrow is to be full surprises. The biggest |
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| 189:40 | is going to be rain. He me. Ok. Um I, |
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| 189:48 | can't say cancel the class. We're gonna have to hope that we get |
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| 189:54 | when it's not raining too hard and pack an extra suit of clothes and |
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| 190:03 | nice garbage bag and wrap it and tape on it. Hey, you |
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| 190:10 | float, float. Yeah. any comments or questions? What |
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| 190:24 | What about it? That |
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