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.

Credit: (foreground photo) Andrea Church and Technology Review

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.

Story continues below

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.