Shale oil: the boom heard around the world

• By Prof. Scott L. Montgomery, University of Washington • The US is in the midst of an oil boom. Shale gas has grabbed much attention, and rightly so. But it is shale oil (a light, crude oil found in shale or tight sandstone, and also known also as tight oil) that could more radically redraw the geopolitical map. What factors might determine this? There are global alternatives to natural gas (coal, nuclear, renewables) in its key area of growth, power generation. But there are none for oil. This is changing, but it will take time. So if tight oil development spreads to other nations in the next 10-15 years, we could see big changes. Import needs for consuming centers — the US, China, the EU, India — could fall significantly, and thus so would the power of petrostates like Russia, Iran, and Venezuela. The geological uncertainties But there are uncertainties. Some relate to geology. Tight oil resides in rock with oil-bearing pores that are unconnected. Fracturing connects the pores and creates pathways for it to flow to the well. Shale is only one type of rock where this works. It can work especially well, because shales are primary source rocks for petroleum and thus can contain much oil. Fracking, however, has limits. Fracked wells decline rapidly. Oil directly contacted by the larger, more open fractures flows first to the wellbore and is quickly produced. Thereafter, oil further out in the fracture network leaks more slowly to the well. Shale wells can go from 1,000 to 100 barrels per day or less in the first year, then to 30-50 barrels in another two years, as decline slows. These wells pay for themselves in that first year, but to keep production high, more wells must be constantly drilled. In some shales, this is changing, as new techniques succeed in reducing early decline. Still, depending on rules about well spacing, many thousands of new wells might result ...Zum vollständigen Artikel

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