| 00:00 | You can, you can see Yes, I can see it. |
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| 00:06 | . So just for review and then we'll go into, I'm just |
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| 00:10 | immediately, uh we'll just review this and if you've got any questions, |
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| 00:13 | we'll just give you a little, , give you a little quiz and |
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| 00:17 | , I'm not gonna watch you I've been talking to some people who |
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| 00:20 | online instructors. I, I know , uh, I know it's hard |
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| 00:25 | do something in real time when somebody's at you through a screen or |
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| 00:28 | So, um, I'll give you little bit of a bit of time |
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| 00:33 | , to do the, to do little quiz, a little exercise. |
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| 00:37 | here we've got um, one that were looking at before and our standard |
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| 00:44 | to, to do visual analysis and a little bit of quantitative analysis with |
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| 00:49 | logs as we did a lot of I recollect last Saturday, uh you |
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| 00:55 | recollect too. We had, typically logs are plotted from left to right |
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| 01:00 | they're usually plotted with uh some drilling , some bit size on the left |
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| 01:07 | , uh tracks. There might be caliper. So we talked about caliper |
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| 01:12 | we want the caliper to be just , you know, plus or minus |
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| 01:15 | couple of inches. Uh We don't to see a, a 12 inch |
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| 01:19 | out or anything with respect to our . So we quickly check the |
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| 01:23 | make sure that that's not too variable it is. We're just going to |
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| 01:28 | of flag that as a less reliable for the logs. So we look |
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| 01:32 | the caliber and then we've been looking the gamma ray and typically gamma ray |
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| 01:37 | we're regarding it as clean or radioactive . And then depending on the local |
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| 01:46 | , we interpret clean as being sandy maybe uh some of the pure carbonates |
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| 01:53 | , and hydrates or salt, but interpret it as not shale. Then |
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| 02:00 | go into the S P N S is a little bit complicated. It's |
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| 02:03 | simple, simple measurement, but it's in uh its uh result. But |
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| 02:10 | , we imagine that the S P developed because there's a full a voltage |
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| 02:14 | across an interface. And generally, regard that as a permeable area. |
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| 02:18 | when we see it kick, we permeability and it's also attached to uh |
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| 02:25 | shale, the shales are not permeable general. So we sort of attach |
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| 02:30 | S P to a permeability measurement when kicks to the left or if it |
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| 02:35 | to the right, depending on the relative salinity of the drilling mud |
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| 02:39 | uh formation. So big kick one or the other tells us about uh |
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| 02:45 | and generally not shale. Then we we kind of jump to the money |
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| 02:51 | , which is the resistivity and we at the resistivity. Most rocks are |
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| 02:57 | , but almost all rocks you saturate brine, which is conductive. So |
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| 03:01 | we see a big resistivity, we're , and that's generally going to be |
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| 03:10 | or if we're shallow, maybe fresh or the one other possibility is that |
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| 03:17 | just about no porosity. So the might be conductive. But if there's |
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| 03:25 | porosity, there's generally no permeability. we can't get any current flow. |
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| 03:34 | um it's conceivable if we have very porosity that we can also have high |
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| 03:40 | , but that's kind of a pathological case. So we look at the |
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| 03:45 | , uh we would immediately go then to the porosity. And generally, |
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| 03:52 | we have to tell the instruments what of rock we're dealing with because one's |
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| 04:00 | measuring neutron flux, the other one's gamma ray flux and those physical phenomena |
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| 04:08 | to be calibrated to actual porosity. we gotta tell the instrument what kind |
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| 04:14 | rock we're dealing with. We do sand dola or limestone. And the |
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| 04:19 | is that it's brain saturated. So what's built into the conversion of the |
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| 04:26 | physics measurements into a prostate. when that's true, the logs agree |
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| 04:34 | , when that doesn't describe the Then the logs typically disagree. But |
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| 04:40 | use that disagreement to understand um a bit about what the porosity is and |
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| 04:47 | also what kind of rocking. So , we talked mainly about this big |
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| 04:52 | . If we're in a uh a area, the neutrons are not going |
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| 04:57 | see the gas. And so the is gonna say there's low porosity in |
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| 05:04 | density log, the gamma rays are zip through the gas too and tell |
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| 05:10 | that the bulk density is low. we're going to interpret that as a |
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| 05:14 | porosity. So when the density logs high porosity and the neutrons says low |
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| 05:23 | , that's typically a strong gas When the logs agree, that's typically |
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| 05:33 | it's a brine saturated whatever rock we it was. And so they're gonna |
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| 05:39 | often there is a little bit of between the neutron porosity, which can |
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| 05:47 | be a bit lower than the dens . That's because there can be clay |
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| 05:55 | shali. So when there's shali, actually there is um hydrogen and clay |
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| 06:05 | the shale. And so that can , can push the um the neutron |
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| 06:14 | maybe a little bit lower than the well, sorry, I I'm |
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| 06:22 | I'm gonna restate that stuff. If look at, for example, if |
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| 06:25 | look at this uh red, you see that the neutron porosity is actually |
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| 06:30 | than the density porosity. And that's again, there is some water in |
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| 06:36 | shale and there is some other So the uh the neutron is saying |
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| 06:43 | the porosity is a little bit higher the shales, then the density pros |
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| 06:50 | that's going the opposite way of, our crossover. So it does not |
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| 06:54 | us with gas. So generally, we see that the neutron porosity is |
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| 07:03 | bit higher than the density process. the opposite of what we said with |
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| 07:07 | gas, then usually we're gonna see that's due to clay because there is |
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| 07:13 | in the clay. And uh the and the shells might be still relatively |
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| 07:21 | bulk density, but there is a amount of porosity in them. And |
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| 07:25 | the neutron log is picking that porosity density log might not be because once |
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| 07:30 | , the density log, we told was sand, Dola or um |
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| 07:37 | it's not, it's shale. And the logs are mis misrepresenting the associated |
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| 07:49 | So once again, just look at set of logs you can see in |
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| 07:52 | shay area, the neutron porosity is than the density porosity. But then |
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| 07:59 | we go into the uh the gas , there's a, a complete |
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| 08:04 | the red log or the neutron it's very low. It says there's |
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| 08:08 | , there, there's no water, is true. The uh the bulk |
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| 08:14 | says, oh no, it's my bulk density is getting lower because of |
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| 08:17 | gas. So I interpret that as high porosity and they have very different |
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| 08:22 | . That's our crossover neutron low density . OK. Now, uh it |
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| 08:31 | turns out in this case, we to have a P in a, |
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| 08:34 | a um a P wave log and in a density log. And we |
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| 08:40 | them, the uh the P wave decreased a little bit because of the |
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| 08:45 | density gas effect and the density has dropped. And we imagine that if |
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| 08:57 | were to put those logs together multiply times density that gives us impedance gives |
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| 09:03 | acoustic impedance. And then I just sketched uh what could be an acoustic |
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| 09:09 | log there and then we could block Z B to make it simpler. |
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| 09:15 | then I could compute a change in or the reflectivity and then I could |
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| 09:22 | a wavelet or convolve a wavelet or limit that response as an echo from |
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| 09:27 | surface would see. And I'd get seismic ground that would look something like |
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| 09:30 | little sketch ass on the right. . Any, any questions about |
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| 09:40 | So for the Z B, I see why it blocks to the left |
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| 09:45 | . Um For R why does the go to the right? Like we |
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| 09:50 | like the one that I understand and it goes back to the right? |
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| 09:52 | it because it's just going back Yeah. So here, as |
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| 10:01 | you've mentioned, we've got a decrease impedance. So remember the reflection coefficient |
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| 10:08 | the change in impedance over the sum the impedance. So the change of |
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| 10:16 | is negative as I go from here here and then as we go |
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| 10:22 | nothing happens, then I hit this and now I've got the impedance is |
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| 10:29 | . So the change of impedance over impedance is an increase positive reflection |
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| 10:34 | So it's just relative to itself pretty it's relative across the interface. |
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| 10:41 | So these um if we think of as layers and say this would be |
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| 10:48 | one layer two, layer three, four, the the reflectivity is the |
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| 10:56 | in layer one with layer two. Z W Z two minus Z |
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| 11:00 | So Z two minus Z one over two plus Z one is negative that |
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| 11:10 | Z two minus well, Z three we look at the deeper one over |
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| 11:16 | shallow one Z three minus Z two positive for the sum that gives a |
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| 11:22 | number. That means that the the are always going down because that's what |
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| 11:27 | wave of seeing the wave of seeing going down. I hit an interface |
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| 11:30 | I bounce back. How big is interface? Well, it's the difference |
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| 11:35 | the upper and the lower. So looking at imagining that there's an |
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| 11:41 | every one of these depths, every is potentially interfaced. Now, if |
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| 11:47 | really took the real logs here, , there are little interfaces all the |
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| 11:50 | down here. Every one of those an interface. The reflection is really |
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| 11:56 | derivative of this or the change as go from one level to the next |
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| 12:00 | er reflection, next level to the level reflection, next level. So |
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| 12:06 | point and its neighbor below it gives reflection value. I made it simple |
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| 12:14 | . I'm only showing uh say three values. One layer, two |
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| 12:19 | three layers, well, four The reflection is strictly the difference across |
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| 12:26 | interface. And then we put a vibration down. It hits that |
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| 12:32 | bounces back there. It also hits guy bounces back, hits this guy |
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| 12:38 | back and we sum those all together this is what we receive at the |
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| 12:43 | . We're gonna go into that some . Stopped here, we stopped |
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| 12:51 | OK? So let's just, I'm gonna give you a quick little exercise |
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| 12:58 | . Um If the great gods are . Oh That's not the one I |
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| 13:22 | . OK. Just hold everything. OK. Let me quickly find that |
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| 14:00 | . OK? Just stand by for second. Um I didn't, I |
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| 14:06 | an, I made a an exercise but I put it someplace safe, |
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| 14:11 | safe, very, very, very . So let me just OK. |
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| 14:44 | . Can you see this guy Yes. OK. So this |
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| 14:50 | this is just uh a quiz. another log suite. So uh I |
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| 14:59 | it's things you need to know. in a plastic section. The, |
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| 15:06 | mud was our standard resistive freshwater And, uh I would say |
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| 15:31 | for question six, um, I know whether we actually ran, I |
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| 15:37 | we ran through the, the But, um, what just, |
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| 15:42 | for question six, just write down equations for the, uh for that |
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| 15:47 | . I don't think you have to them right now. So just for |
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| 15:50 | , um, write down the I think everything else is kind of |
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| 15:55 | that we've, we've been through. . OK. Just, just take |
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| 16:07 | few minutes and uh, and do that. OK. Um |
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| 16:13 | uh, I think you just need probably write down the answers yourself and |
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| 16:20 | give those to me. I don't whether you can, um, whether |
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| 16:22 | can get a hard copy. Do have a hard copy ability or you |
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| 16:26 | uh maybe just copy this or I just screenshot, I can do a |
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| 16:31 | of my screen and just throw That's fine. OK. OK. |
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| 16:35 | . So just a screenshot, uh your annotations or whatever. And |
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| 16:38 | um, so I'll, I'll let take some minutes of that and |
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| 16:44 | we'll go from there. I'm, gonna go grab a coffee. |
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| 16:51 | Sounds good. How are you Stephanie? I'm almost done. I'm |
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| 17:12 | , I'm just finishing up five and I just gotta do six. |
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| 17:17 | Yeah, I've got one other little for you that, that reinforces |
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| 17:20 | So, no, no hurry Take your time, just get |
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| 17:23 | make sure it's all. Ok. . I'll, I'll be here. |
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| 5999:59 | |
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