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  2. Sweet Spots

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- [Voiceover] So, let's look at sweet spots in shale plays, what we know now. We know that, and this is cited before, liquids-rich shales, that maturity is a key determinant. Vitrinite reflectance of more than 85% in marine facies, and more than 0.9% in continental facies, they do have sufficient hydrocarbon generating capacity, and they have been subjected to enough heat. So, other things that you should have in a shale play, TOC, obviously, organic porosity development, should have a favorable migration pathway, favorable conditions for natural fracturing , and also favorable pore pressures. There are many different types of sweet spots. There are geological, engineering, and economic. Let's just take a look at the geological ones. Basically that has to do with heterogeneity of the lithofacies that can be mineralogical as well as depositional. Engineering really has to do with the rock properties, the pore pressure, it's brittle, ductile, Poisson's ratio, Young's modulus, less relative heterogeneity, and isotropic crustal stress. Then, finally, we look at economic sweet spots. They usually need to have economies of scale, and the quality has to be uniformal, adequate, it has to be accessibility in terms of access to infrastructure as well as being able to drill it. It has to be amenable to pad drilling, and it can't be too deep, and it can't be too shallow, primarily due to pressures and temperatures. Now, we'll look at reservoir heterogeneity types, and these are mainly sandstones, and let's say, "Well, what do they have to do with shales?" Well, they have a lot to do with it because of let's say diagenesis and reservoir fluid Also, fracture networks, pore architecture, structure and lithofacies changes. So, there are many different kinds and I put a diagram here that has different kinds of heterogeneity in the sands, but in terms of shale heterogeneity, I think it's most useful to take a look at pore architecture and how that changes, and then also diagenetic changes in the facies themselves. And we also need to look at migration pathways. It's really important to have a good migration pathway that you can actually identify, and that means understanding the tectonic history, understanding the basement structure, the fracture networks, and also the direction of flow from the so-called kitchen, and understanding the source so that as you're ranking your areas, the proximity to a proposed migration pathway's extremely helpful. This is the most evasive, but I'd like to mention anticlines on the Antarctic Basin, and which is just absolutely outstanding. And this was published in the USGS that Jay and her team worked have worked on extensive modeling of the Antarctic Base and the generation and expulsion of oil and where it went in theory all the way from Sun Eagle Summit through to Kansas, which is pretty amazing, and I also like to mention Brian Cardott's work on the geological survey. He's done a lot with kerogen typing, immaturation, and geochemistry just to give an idea, again, of the depositional history but, more than anything, the thermal maturation history and the travel of the way that the hydrocarbons moved. Also, we need to understand the different kinds of connectivity. Connectivity is critical for sweet spots, because it's not just about storage and the amount of oil or gas that can be stored, it's also about how to get it out, and on the nanoscale, the pores are actually connected. Now, there's a different kind of conductivity that occurs during induced fracturing, and you want to have good conductivity because of fractures that move, open up, stay open due to propping, and that they allow, or even stimulate, movement of reservoir fluids. But, what you need to understand is that there can be frac interference. Frac interference can be positive and it can be negative. It can lead to pathways watering out or not connecting, and also lead to reservoir damage. So, it's definitely useful to try to model what happens in the fracture, what the frac heights are, the extent of the fracturing, and any potential frac interference. So, if we look at engineering sweet spots and we look at what we know now about oil and gas and shale plays, what we know is that the Bakken is much, much more efficient. The operations are much more efficient. So, just have a slide that gives you lots of details, but also gives you the classic Oreo cookie configuration of the shale and the different formations. Three Forks, Milwaukee, and Lower Lodgepole being the sweet spots. The Upper Bakken Shale and the Lower Bakken Shale being the barriers that actually help in creating reservoir pressure.