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Energy

Oil Left in the Ground

High prices still haven’t prompted companies to use advanced extraction methods.

Even with record-high oil prices, about two-thirds of the oil in known oil fields is being left in the ground. That’s because existing technologies that could extract far more oil–as much as about 75 percent of the oil in some oil fields–aren’t being widely used, according to experts in the petroleum industry.

Several well-established technologies, including “smart oil fields,” exist that could significantly boost the supply of petroleum from oil reservoirs. But a lack of investment in such technologies, particularly by the national oil companies that control the vast majority of the world’s oil reserves, is holding back implementation. When oil is drawn from a field too quickly, or from a bad location, or with the wrong kind of well, large amounts of oil can be left behind, says Richard Sears, a visiting scientist at MIT who has served as a vice president for exploration at Royal Dutch Shell, based in the Netherlands. But the best technologies for managing an oil field require up-front investment–when an oil field is mapped and characterized and the first wells are drilled–and the payoff can take decades.

In most oil reservoirs, the oil resides in porous rock in geologic layers that are tens of meters thick but stretch for miles. A conventional oil well is a vertical shaft, so it is in contact with only a narrow cross section of the reservoir. Such a well depends on oil percolating through microscopic pores over long distances. That can slow production, and often oil can be stranded inside the irregular geometry of the oil field.

For 15 to 20 years, however, it’s been possible to drill horizontal wells. These follow along the length of an oil field, so that the well is in contact with oil for miles, rather than for just several meters. What’s more, advanced imaging technologies and new drilling rigs have made it possible in recent years to drill to an accuracy of one or two meters, Sears says. The increased precision in drilling allows oil companies to stay close to the top of the reservoir, where the oil is, and away from the water that can exist in the reservoir.

It has also become possible to make “smart wells” that include sensors that can survive the extreme temperatures and pressures found deep underground. These allow oil companies to detect, for example, when water, instead of oil, is being pulled into the well, and to quickly shut off production from that area, while continuing to produce from other sections of the well.

Such smart oil fields have started to become more common for international oil companies such as Shell, Exxon-Mobil, and BP. But they still aren’t used in most oil fields. And their use is particularly low in fields run by national oil companies, says Larry Schwartz, a longtime researcher and scientific advisor for Schlumberger, a Houston-based company that provides various services to oil companies.

Schlumberger historically focused on providing services at the “front end,” he says, which includes taking measurements, such as of the amount of oil and how easy the oil will be to produce, and “drilling sophisticated wells.” But since oil prices have been high, the company’s biggest revenue stream has come from projects related to improving existing wells, such as by fracturing rock underground to try to improve oil production at conventional wells that have stopped producing as much as they used to.

Steven Koonin, BP’s chief scientist, says that cutting-edge research could lead to automated oil rigs on the sea floor, ultra-deep-water ocean drilling, and arctic exploration and production, as well as to technology for extracting oil from unconventional sources, such as shale. But although oil prices have been higher than $60 a barrel for almost three years, Koonin says that for the most advanced technologies, “oil prices will have to stay high for a couple of years longer before companies think they can make big investments.”

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