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Energy

Increasing Oil Supply

Novel extraction technologies could as much as double accessible world oil.

The amount of accessible oil worldwide could eventually be increased by roughly 30 percent with the help of new drilling, imaging, and oil extraction technologies, including the use of microbes, say MIT researchers. Theoretically, this number could be even higher; in a best-case scenario, the amount of oil that could be produced would double.

Rapidly heating many rock types causes them to break apart. This process could be the basis for a new, less expensive method of drilling for oil. (Photo courtesy of Jefferson Tester, MIT.)

On average, using current techniques, about two-thirds of the oil in an oil field gets left behind, says Richard Sears, a vice president at Shell International Exploration and Production, Houston, TX. “The fundamental problem is basic physics. It’s not like the oil is in big tanks. We produce oil from rock – sandstone. The oil is actually held in the very small spaces between the grains of sand. The problem is, when you try to move that oil out of the rocks, because of the size of the spaces, you end up with a layer of oil coating the insides of the rocks.” About one-third of the oil in fields will always be inaccessible. That leaves one-third that could be recovered with new technologies – which is equal to the amount that would have already been extracted.

Getting all of this oil out would be extremely ambitious, but Robert van der Hilst, earth, atmospheric, and planetary sciences (EAPS) professor at MIT, says much smaller gains would still be marked improvements. Increasing the percent of oil harvested from worldwide oil fields by even one percentage point would be the equivalent of adding a new oil-producing region as productive as the fields in the entire North Sea, he says.

To a certain extent, getting more oil out of existing fields is a question of economics. Oil, which resides underground in porous rock, can be forced out by injecting water, steam, or carbon dioxide, but these methods bring added costs that limit their use. If oil prices stay consistently high, these methods will be employed more than they are now, Sears says.

But significantly increasing oil recovery will require new technologies. At the top of the list are better oil field imaging techniques, says Nafi Toksöz, an EAPS professor at MIT. Improved imaging can help oil companies find and tap areas in an oil field that have become surrounded by water, and so cut off from oil wells, he says. It can also improve the effectiveness of existing methods such as using water or steam to extract oil.

As it is now, water pumped into a field, for example, might start to cut a channel through the oil, and so, rather than pushing oil out, would simply enter through an injection well and flow out through an extraction well in the place of oil. Better understanding of the dynamics of an oil field through imaging at regular intervals can help engineers know where best to inject water and steam, and how to control the pressure to prevent channels from forming.

Today, oil explorers image reservoirs of oil using seismic waves, generated by explosions or big vibrator machines. Thousands of sensors distributed around a oil field detect reflected waves, and from this information computers generate a three-dimensional image. They use low frequencies that penetrate miles into the earth, but the tradeoff for distance is low resolution.

One way to improve imaging is with better algorithms for sorting signal from noise in sensor measurements, something computer scientists at MIT are working on. For example, as seismic waves encounter geological formations, they can change form to a type of wave, called a sheer wave, that can produce more detailed information about a reservoir, if information about these waves can be sorted out from other incoming signals.

Also, less expensive drilling technology may make it feasible to use more sensors or vibration sources underground, closer to the oil, which makes it possible to use higher frequencies. Additional holes could also be used for pressure and chemical sensors. Jefferson Tester, professor of chemical engineering at MIT, has demonstrated a drilling technique that replaces mechanical drill bits with a flame for breaking apart the rock with heat. The technique can be more energy efficient and faster than mechanical drilling, and perhaps more importantly does not require that a drill bit be periodically raised to the surface and replaced – a major reason why drilling costs now rise exponentially with the depth of a well, Tester says. While his technology is not yet ready for full-scale deployment, in addition to allowing placement of more sensors, it could potentially allow energy oil companies to drill holes much deeper for economically recovering oil.

Future innovative technologies could include new methods for breaking the adhesion forces that trap oil inside tiny pores in rock. These include technologies for focusing acoustic and electromechanical energy to disrupt the surface forces between oil and rock; new chemicals and even microbes could also help. The microbes would work in part by digesting the long hydrocarbons of thick oil into shorter, lighter ones that flow more readily.

If the new technologies prove out, the results could be dramatic. “In the U.S., there could be as much as 40 billion barrels that could be produced, and global the figures are much, much more,” Toksöz says. The 40 billion barrels is about four times the amount thought to be recoverable from the controversial plan to drill in the Arctic National Wildlife Refuge.

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