A greenhouse gas goes underground

It may seem like sweeping the problem under the rug. But at a partially depleted oil reservoir in the flatlands of southeastern Saskatchewan, Canadian researchers have found a cheap solution to global warming: burial.

By injecting carbon dioxide (CO2) into the underground oil field, the researchers are not only cutting emissions of the greenhouse gas, they're also boosting oil production. The extra oil generates enough revenue to substantially offset the cost of burying the CO2.

"We have been able to show that you can safely capture carbon dioxide that would otherwise go back into the atmosphere," says Ben Rostron, a coordinator of the University of Alberta project. "Everything we've done has shown us this is a good place to store carbon dioxide."

While underground storage of CO2 won't solve the problem of global warming by itself, it could dramatically reduce the amount of heat-trapping greenhouse gases spewing into the atmosphere, experts say. It's already part of President Bush's energy plan. And the idea is gaining momentum in other parts of the world.

The $28 million demonstration project in Saskatchewan began in 2000 to investigate the feasibility of storing CO2 in the 44-year-old Weyburn Field. The CO2 is shipped in via a 220-mile pipeline from the Dakota Gasification Company's plant in Beulah, N.D. (The plant converts coal to clean-burning natural gas.)

One big reason to choose old oil fields for underground CO2 storage is the economics. The pressure created by injection of the gas into the permeable rock drives more crude oil to the production wells. In addition, the injected CO2 emulsifies and partially dissolves the crude, allowing it to flow more easily to the production wells. This process produces additional oil, which offsets the costs of separating CO2 from industrial smokestack gases, transporting it, and pumping it deep underground. These costs are substantial, about $30 per ton of CO2. (The US Department of Energy is funding research to reduce separation costs to $8 a ton.)

Another reason: The geology of old oil fields has been studied intensively. This knowledge enables operators to avoid two potential problems: water pollution and CO2 leaks.

CO2 injection repressurizes the oil reservoir. This step could force briny water up, polluting surface waters and aquifers. In addition, CO2 could leak to the surface and escape into the atmosphere, defeating the whole purpose of the project. So far, none of the CO2 injected into the Weyburn Field has escaped to the surface nor is there evidence of polluted water in the area, says project manager Michael Monea of Canada's Petroleum Technology Research Center.

About 21 million tons will be injected over the 25 years of the project. Saskatchewan's oil fields are large enough to store all the province's carbon-dioxide emissions over the next 30 years, according to the research center, which manages the Weyburn project.

In addition, oil production at the field has increased 50 percent since CO2 injection began four years ago. The project aims to recover an additional 130 million barrels of oil worth over $5 billion.

The US Department of Energy is planning a similar project in Wyoming. The 10,000-acre Teapot Dome oil field would store CO2 piped in from a natural-gas processing plant more than 300 miles away.

For more than 20 years, CO2 injections have helped recover hundreds of millions of barrels of oil from old west Texas fields that otherwise could not be produced economically. But the CO2 used in these projects comes from deposits deep underground. So there is no net reduction in greenhouse gasses.

Under Mr. Bush's energy plan, power plants would capture 90 percent of their emissions for underground storage by 2012. Since the plants are a major producer of CO2, the plan would reduce by about 40 percent the 1.6 billion tons of CO2 the US emits annually, about one-quarter of the world's total.

Underground CO2 storage could have wide application globally. "Countries around the world are spending millions to investigate this same technique," says Dr. Rostron.

For example, the Research Institute of Innovative Technology for the Earth (RITE) started an underground CO2 storage project in Nagaoka, Japan, in July using government funding. The goal is to develop technology for routine use by 2015. RITE estimates Japan can store about 70 billion tons of CO2 underground. According to Japan's Environmental Ministry, this is more than 50 times the country's 2001 CO2 emissions. But Japan does not have enough oil fields to offset the costs of CO2 storage underground.

While underground storage of CO2 would achieve "deep reductions" in emissions, long-term solutions must include increased use of renewable energy sources and improved energy efficiency, says David Hawkins, director of the climate center for the Natural Resources Defense Council, a US environmental group.

Underground CO2 storage, combined with conservation and wind, solar, and nuclear, could make major contributions to reducing global CO2 emissions, says Robert Socolow of Princeton University's Carbon Mitigation Initiative in New Jersey.

Global emissions of the gas could triple over the next 100 years, if something isn't done, says the United Nations Intergovernmental Panel on Climate Change.

"Fortunately, we have the tools to do this," Dr. Socolow says, "especially if we think in terms of 50-year campaigns, not instant solutions."

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