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  5. Summary and Key Takeaways

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- [Instructor] So in summary, I'm just going to highlight the key takeaways, I think of the presentation. And if you know, if people, if people don't wanna read through the paper, these are the key things I'd like people to keep in their head when they think about core analysis and the valuable ways to keep becoming predictive as petrophysisists. So the reported porosities and saturations always, almost always are generated with corrections and assumptions that you're not necessarily going to agree with. So that could be water densities, that could be other densities, you know, as I mentioned brine and distilled water corrections. And even oil recovery. So the one thing that I didn't touch on too much here is the effect of oil recovery, and you know, there's a lot of work done by, it's actually an API standard that you, during retort, you do not effectively recover all of the oil. You leave a residual oil saturation. Do you need to make that correction? So we didn't make any corrections here, so everything's on an apples to apples basis. But it's just something to think about. What corrections do you wanna make to the raw weights and volumes that you have? And then how do you come up with the total porosity? With the corrections applied, the Dean-Stark and retort showed very good agreement. And then what we saw, through the presentation, is without, you do see that systematic shift. So if you're comparing analysis that you've done using Dean-Stark and then another area that you've done with retort, you almost, you pretty much have to go back to the weights and volumes and calculate pososity using an apples to apples way, using the same set of assumptions so that you compare area to area on a fair basis. And both vendors had very similar fluid recovery, especially in the water space. The oil space a little bit different, but the total oil recovery in retort, very, very low. But then the porosity and saturation, very, very different answers. So again you're seeing this assumptions and corrections that are propagating through the calculations and can lead to very, very different results at the end. And back to that 20-30% shift. The missing weight is really the big thing that I'd like people to think more and more about in terms of volume summations if you're using volumes and do you have a weight discrepancy that you're not accounting for in your volume recoveries. And then also, the inference in Dean-Stark, that you, that all the missing weight, minus your water weight, is oil weight. Is that true, or is it not true? Am I losing oil or water through the process because I, that also makes a big difference in the calculation and speaks to the difference in oil recoveries between the retort and the Dean-Stark. Critical retort temperature steps not the same from lab to lab and rock to rock. So as you move between equipment types, as you move between rock types, it can go from a very gassy clay to a very, say, water filled clay. You're probably gonna wanna do different temperature steps to separate out the mobile fractions and think, how important are these fractions to my specific clay. And then finally, you will see significant differences if you do not apply the same set of assumptions and corrections. Not all core data is apples to apples, and that's probably the simplest takeaway I can provide. So in what's next, more work on the temperature steps, I think is a very obvious one. So as we get more and more examples and ways to test this, you get, you can go in from equipment to equipment, start calibrating these temperature steps and try and figure out which temperature steps are important and how you calibrate that back to free and mobile. You know free and immobile water fractions, put that back in the rock under in-situ conditions. And then can we maintain in-situ saturations? So one of the things I mentioned is you see 30, 40, 50% gas filled porosity at the surface, so you've lost a significant amount of your in-situ fluid volume before you get to the surface. A lot of people assume that's 100% hydrocarbon loss, but is that true? How much water are you losing as you bring this to surface, and how do you minimize that effect? Can you use NMI measurements at the wellsite, NMI measurements down the hole, to compare to the surface? You know, pressurized core, things that can help you maintain the saturation as you bring them up to the surface. Wellsite measurements, I just mentioned with the NMI, but what can you do at the wellsite to help tack your fluid? We do a lot of tracking once we get to the lab, I'd like to see us improve the tracking as we go from, you know immediately being out of the hole at the wellsite, to getting it to the lab, tracking any water loss, weight loss, oil loss that might happen during that time. This mobile and immobile fluid volumes is a huge thing in terms of, you know, if you think about the Permian Basin, high water curtain, many, many wells. Just a difference between five and 10% water curtain can be difference between an economic and uneconomic well. And just separating that has a huge business drive to it. And then ultimately, how do we take some of these and upscale it to log level, this core analysis, upscale at the log level, even well level, but then significantly, field level, where you start stitching together this handful of core points you might have with pilot holes and try and become regionally predictive to try and get into acreage early. And really that's the predictive power that petrophysics should be providing to the industry. And then the other thing I have right at the end here is what do other operators, what do other service companies, what do you guys see as the gaps? I'd really like to see some other people chime in there and say, "Hey what's next in core analysis?" and, "How do we start minimizing the uncertainty "and get petrophysics to the predictive power "that I keep mentioning?" So with that I'll summarize it and take some questions. I just wanna acknowledge the vendors for working with us on this project, along with Shell management who ultimately paid the bills for all this stuff and keeps supporting this technical work. Sonja Perry, Nitin Chowdhury, Brice Peterson, Lisa Corder have all been instrumental in this. Along with other shell contributors from research and other departments of the company, Long Ma, and Anton Nikitin. Long Ma especially was a hydrologist on this. I worked very close with her through a large of this process and really helped and make with the core acquisition. And then finally SPWLA for many opportunities to present this, along with, you know, the webinar series, along with the symposium. It's been great.