Colorado Scientists Test Cryogenic Fracturing

Petroleum Engineers in Colorado are Working on a Process which Replaces Water with Searing Cold Liquid Nitrogen or Liquid Carbon Dioxideto Get More Oil from Shale

Gas fields in Colorado soon may serve as a laboratory for testing a different way to fracture shale rock formations - one that doesn't pump millions of gallons of water underground or yield contaminated wastewater.

Even as environmentalists rekindle efforts to ban hydraulic fracturing in the state, petroleum engineers in Colorado are working out the kinks in a process called cryogenic fracturing, which replaces water with searing cold liquid nitrogen or liquid carbon dioxide.

Fracturing with water has turned the United States into one of the biggest energy producers in the world.

Scientists at the Colorado School of Mines in Golden hope that the ultra-cold thermal shocks that occur when liquid nitrogen meets shale rock will have a similar effect as water, creating enough stress to crack open the subterranean stores of oil and gas.

Swearing off water could calm some of the environmental opposition to fracturing.

And because the liquid nitrogen would evaporate underground, cryogenic fracturing could form bigger canals for oil and gas to flow through than water-based fracturing, boosting oil and gas production.

"Essentially, some shale absorbs water very quickly, and the entire formation swells in size and closes up any pathways," said Kent Perry, vice president of onshore programs at the Research Partnership to Secure Energy for America, which administered a $2.6 million Department of Energy research contract for the project.

"When you're using water in shale formations, even where you're successful with the development, recovery is still low, and part of that is water trapping."

Drastic difference

In concept, cryogenic fracturing works like hot water pouring onto a frozen car windshield - producing a sharp temperature change that can crack the glass.

In practice, liquid nitrogen or liquid carbon dioxide would be poured down a well through steel or fiberglass tubing as a fracturing fluid, in place of the water that typically is blasted underground along with chemicals and sand or man-made proppants to hold the fractured rock apart.

It's a spin on fracturing experiments with gaseous nitrogen that oil companies tried in the 1970s and 1980s, with disappointing results, and a follow-up to more recent attempts with liquefied nitrogen that proved too costly.

Seeking better results

Since the U.S. shale bonanza began a few years ago, oil companies have extracted only a small percentage of the hydrocarbons sitting in the sometimes mile-deep rock formations. And rapid decline rates in shale oil and gas production have prompted the industry to look for ways to enhance output.

In 2011, the Department of Energy chose 11 research projects worth a combined $12.4 million to bolster oil and gas recovery and cut into the environmental effects of fracturing. The engineers at the Colorado School of Mines, which was selected for one of the largest projects, partnered with a national lab and several companies, including Dallas-area oil producer Pioneer Natural Resources and Houston-based proppant maker Carbo Ceramics.

Though fundamental lab work still is being completed, Perry said, field testing has to begin next year to keep the project on schedule, probably at Pioneer Natural Resources' wells in the Pierre Shale in southeastern Colorado. Pioneer declined to comment.

Public domain

Rather than commercializing the cryogenic fracturing process, he said, the Research Partnership to Secure Energy for America would put the intellectual property into the public domain so that oil companies could use it and improve it.

Some energy and fracturing experts are skeptical about the cryogenic method.

Liquid nitrogen, like many of the alternatives to water that the oil industry has tried, lacks the energy capacity - called viscosity - to carry sand and proppants, said Ramanan Krishnamoorti, a professor of petroleum engineering at the University of Houston.

Source: Houston Chronicle

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