Tech Scientists Testing New Method of Sequestering Carbon Dioxide, Sept. 9, 2008

By Thomas Guengerich

SOCORRO, N.M., Sept. 9, 2008 – New Mexico Tech researchers are conducting a large-scale experiment near Aztec, N.M. that will have a dramatic impact on future outlook on greenhouses gases, fossil fuels and the oil and gas industry.

Tech researchers are leading a team sequestering carbon dioxide into coal beds, while simultaneously recovering natural gas. The total funding of the three phases is about $90 million in grants from the U.S. Department of Energy and more than $30 million from other sources. Tech scientists are leading the project, with more than 20 partners, including other universities, national labs and industrial subcontractors.

The San Juan Basin project is part of Phase II of a three-phase project. The goal of the San Juan Basin injection project is to inject 35,000 tons of carbon dioxide during a six-month demonstration near Navajo City, N.M. Phase III will involve a four-year injection project in Utah, sequestering up to 2.9 million tons of CO2 with a maximum rate of 1 million tons per year.

“Our purpose isn’t to make judgments about global warming,” said senior scientist Reid Grigg. “Our purpose is to engineer projects to sequester CO2. I believe what we are doing is sound engineering and sound science. If we inject CO2, we want to do it under sound scientific and sound engineering principles.”

The six-month injection project in the San Juan Basin is a precursor to a larger project near Price, Utah, with goal of injecting about 2.9 million tons of carbon dioxide to be injected into a geologic feature called the Farnham Dome.

“We need to do all sorts of things to solve the energy crisis,” he said. “To solve global warming, we need to look at carbon dioxide and we need to show that this can be done.”

Grigg, an engineer at New Mexico Tech, said the decade-long project is examining methods of sequestering CO2 into geological formations. The San Juan Basin coalbed methane site is one of three injection sites being used in Phase II.

In many coal deposits, methane or natural gas, is trapped within carbon deposits. When carbon dioxide is injected into the coal bed, the gas is absorbed by the coal, forcing methane out, Grigg said. Many coal beds in the United States are saturated with natural gas, but much of the gas is not extracted because methane is “stuck” in the coal. CO2 shares the same tendency to bind to coal. Laboratory tests show that coal preferentially absorbs CO2 over methane, with two molecules of carbon dioxide displacing one molecule of methane, Grigg said.

Until recently, the cost of injecting CO2 was more than the value of the produced methane. Recent price increases make the process cost-effective, Grigg said.“Just two years ago, the cost of injection was more than the price for methane,” Grigg said. “With the price of methane going up and people wanting to get rid of CO2, this process looks like a good sink to store CO2.”

At the San Juan Basin, there are three 20-foot layers of coal each separated by about 20 feet of rock at depths between 2,800 to 3,000 feet, Grigg said. One well was drilled, completed into the three coal zones where CO2 is presently being injecting into each layer, Grigg said.

As the San Juan Basin project proceeds, scientists are using pressure gauges, tiltmeters that record minute surface movement, tracers, seismic methods, and compositional sensors to track the movement of CO2, Grigg said.

“We have all kinds of nifty gadgets,” Grigg said. “One device was sensitive enough that we recorded the big earthquake in China on May 12.”

The project started with drilling the injection well in early May, with injection commencing on July 30. As the project proceeds, the rate of injection has been increasing, while project scientists track the surface pressure to ensure subsurface pressures do not exceed recommended levels.

Tech scientists at the Petroleum Research Recovery Center have been studying processes of injecting carbon dioxide into geological formations since the late 1970s, Grigg said. For the first 20 years, the studies concentrated on the industrial use of injected CO2 for enhanced oil recovery. In the late 1990s, the focus started to shift toward sequestration of CO2, using the same techniques. The long-term goal is to discover if carbon-dioxide can effectively be sequestered in geological formations. In cases like the San Juan Basin, the process is made more cost effective by the fact that the extracted natural gas is marketable.

Currently, researchers are using naturally-occurring carbon dioxide. Ultimately, Grigg said the process could be used to sequester manmade carbon dioxide – mostly from power plant emissions. Presently the largest problem is the cost of separating CO2 from other gases.

“We have a couple of methods of separating carbon dioxide from power plant emissions that work well,” he said. “The problem is that they cost a lot.”

Typically, power plant emissions are 85 percent nitrogen and 15 percent carbon dioxide. Scientists have devised methods to separate the two chemicals, but there is no market for nitrogen.

Grigg said the cost of separation is roughly 30 percent of the cost of power generation. In other words, for every 10 power plants, the industry would need three more power plants to produce enough energy to separate carbon dioxide from nitrogen.

New Mexico Institute of Mining and Technology is the lead organization of the U.S. Department of Energy’s Southwest Regional Partnership for Carbon Sequestration. The partnership includes the states of Colorado, New Mexico and Utah, as well as portions of Arizona, Kansas, Texas, Oklahoma, and Wyoming. The Southwest partnership is one of seven regional groups.

– NMT –