- [Voiceover] I want to continue the discussion and move on to the work on the Bakken Mudrocks and the upper and lower organic-rich shale intervals. This particular well just illustrates some total organic carbon content analysis that was done in those wells, increasing TOC numbers to the right and the depth being on the vertical axis in each of these cases. Well you can see, I think, from these plots that the TOC content is not uniform throughout the shale interval but quite variable. So depending on where you take a shale sample and have it analyzed, you may or may not encounter high TOC content. Overall, we see pretty high numbers though for the total organic carbon content and the average across the basin again for both the upper and lower organic-rich shales end up being about 11 weight percent then for the Bakken interval. Murray, back to his classic 1968 AAPG article, a couple of comments that he had on the Bakken shales which perhaps are significant. First one, any restricted reservoir in direct contact with either of the two shale units should be productive anywhere in the deeper part of the basin, regardless of structural position. Then, one of the most important conclusions is the recognition that the upper and lower Bakken shales are supercharged oil shales and are the source of most of the oil. So some fairly strong statements in this article written back in the 1960s. Continuing on with the shale, the mudrocks, we have a device here at the Colorado School of Mines, a QEMSCAN device which is a quantitative electron microscope scanning device. A souped up SCM device, if you will, able to do rapid mineral mapping on thin sections and can also come up with mineral percentages quite fast. In our analysis of the upper shale and lower shale in just one of these wells within the Sanish Field area illustrates the composition of the shales themselves. Main components are quartz, some feldspar, illite, clays, and then minor amounts of carbonate and of course pyrite being present. In these particular two shale intervals, we see the amount of silica content increases toward the middle part of the shale and then decreases in both upward and downward direction for both the lower and the upper shale. Quartz content itself is of the detrital silt grains, but also a biogenic radiolaria aspect to the shales. And one of the items in that we see for the shales is the very high siliceous content that they have and that makes them brittle and perhaps able to fracture much easier. We think those shales are deposited under anoxic conditions. It doesn't have to be anoxic all the time, but largely anoxic conditions. In the model proposed by Smith and Bustin, modified by Meissner et al, illustrates the idea of high productivity of simple plants and animals in a stratified water column. The upper part of that water column, upon death, if those plants and animals die, fall to the bottom, consume the oxygen, create anoxic conditions, and that results then in the deposition of an organic ooze in the deeper parts then of the basin. We can look at modified van Krevelen diagrams. The Bakken shale has been analyzed for many years by many workers and there's an abundance of Rock-Eval pyrolysis data, that's been previously published on the unit, not quite plotted up like this with the van Krevelen diagram. So we took those data and we'd plot them up and in this particular case, hydrogen index versus oxygen index. You can see that the data from the Bakken plot in a Type I/Type II kerogen where the shales are fairly shallow and then with increasing burial depth field approach the origin in a plot, which you would expect with increasing thermal maturity then of the kerogen. Some indication of some of the shallower Bakken at the 4,000-foot interval being a mixture of Type II/Type III, and I'll talk about that in just a couple more slides, that occurs on the flanks of the basin where you probably would expect to see more of a mixing of kerogen types as you get to the shallower areas. There's an abundance of plots that we've made, but I'm only just gonna show you a couple of the plots today and some of the Rock-Eval pyrolysis data, but we can also, using those data, plot production index versus Tmax. When we do that, we see that most of the production then, with the intense generation of hydrocarbons from the Bakken come from areas on the plot where you're greater than 425 degrees C and greater than .08 for the Bakken system. These are different numbers than you see from other shale basins. Most people use a .1 for production index, but we think the .08 is probably more realistic for the Bakken. Then the 425 number is lower than the normal number stated at 435. Anyway, in general, depths greater than about 8,000 feet where the Bakken is in intense hydrocarbon generation mode based on the Rock-Eval pyrolysis data. A couple slides then on the distribution of the shales themselves. This is an Isopach of the lower Bakken shale and it ranges in thickness from zero to over 50 feet, the thickest area being located on the east flank of the Nesson anticline. The red dash lines just illustrates some of the producing trends. The upper northeast red dash line would be the Parshall-Sanish greater producing area. Then over in Montana in Richland County, that one is deep where the Elm Coulee Field is located, so very little lower Bakken shale associated with Elm Coulee but very thick lower Bakken associated with the Parshall trend area. If you look at this similar type of map for the upper Bakken shale and its distribution, it ranges in thickness from zero to over 20 feet. It's more broad. It doesn't appear to be affected by any paleo-structure elements. The Nesson anticline being a paleo-structural element, by the way, and a fairly widespread distribution of the upper Bakken shale. Across the Williston Basin, the temperature anomalies change or temperatures change and the geothermal gradient changes. And it's well-known that the Nesson anticline corresponds to a high paleogeothermal gradient area and that area continues to the south. It was mapped out by Lee, Price and others. We also know as we go off to the northwest into Richland County in Montana, the temperature gradients are still high over there and so the bottom hole temperatures at the Bakken level are greater than 200 degrees Fahrenheit. Resistivity has been used as an indicator of maturity within the shales. And onset of maturity generally we thought to be about 25 ohmmeters and clearly mature or intense generation where you had 100 ohmmeter resistivity within the shales. So I put those lines on this map. Those were taken from paper by Hester and Schmoker, they're USGS workers. When you look at the distribution then of the mature area, it covers an enormous area and extends on up perhaps then into Canada too. So the cooking pot in this particular case being quite large for the Bakken Petroleum System. The change in resistivity as we see it from the low resistivities to the high resistivities paper by Fred Meissner, plastic paper, published by the Montana Geological Society in 1978, suggesting that we go from a water wet shale system to a oil wet system, and that's what gives you the very abrupt and significant change in resistivities. Associated with those resistivity changes, we also have abnormal pressure, so where we have thermally mature Bakken source rocks, we also see very significant pressures and this particular plot from the Antelope Field area illustrating formation pressures of .7 psi per foot of it. Formation pressure's quite less than that, the normal one is .46 psi per foot, and below it, .46 psi per foot gradient. The Bakken being the abnormal pressure unit within Williston Basin. I wanted to just look at maps which illustrate the distribution of hydrogen index for the lower and upper Bakken shale and those would be the only geochemistry kind of maps that I'll illustrate for you. The hydrogen index, again, the highest values which we think correspond to a Type I/Type II are located in the deeper part of the Williston Basin and hydrogen index and immature kerogens getting over 600 in values. As we go to the east part of the Williston Basin, we see those numbers drop down quite a bit. That's where I think we have a mixture of Type II/Type III kerogen. In the central part of this diagram where we have the high geothermal gradient area, and that's documented by bottom hole temperatures on logs and such, we have a dramatic diminishment in hydrogen index too and that's because of the thermal maturity of course of the kerogen. Dominantly Type I/Type II kerogen across the Williston Basin for the lower Bakken shale and the same applies to the upper Bakken shale, Type I/Type II kerogen, but as we go off to the northeast, perhaps a mixture of the Type II/Type III kerogens as we approach the limits of the depositional basin. Within the high geothermal gradient area, again we see the diminishment of those hydrogen index numbers as you would expect with thermal maturity then of the kerogen.