Nick Snow
Washington Editor
WASHINGTON, DC, Aug. 6 -- In a new program, the US Department of Energy and its Southwest Regional Partnership recently began to inject carbon dioxide into a large coal bed while simultaneously recovering natural gas, DOE's Fossil Energy Office reported Aug. 4.
It said the planned injection of CO2 in a 6-month demonstration near Navajo City, NM, differs from other enhanced coalbed methane (CBM) recovery projects because it will attempt to maximize permanent CO2 storage in a process called geologic carbon sequestration using enhanced coalbed methane recovery.
"Many coal beds in the United States are saturated with natural gas (methane), but the gas is difficult to produce because methane typically binds to coal. However, CO2 shares the same tendency … Injecting [it] into the coal bed essentially displaces the methane and makes the gas easier to produce," the report indicated.
The San Juan basin is considered one of the top-ranked basins worldwide for CBM. Favorable geology, high methane content, available CO2 from nearby power plants, low capital and operating costs, and well-developed natural gas and CO2 pipelines make it a prime candidate for value-added CO2 sequestration, according to DOE.
Some San Juan basin coals are exceptionally permeable, at least in comparison to other coal beds in the region, it continued. "Due to the tendency of coal to swell when in contact with CO2, high initial coal permeability is required to maintain CO2 injection rates (high injectivity) over time. DOE has established high injectivity as a sequestration program goal for large-scale, low-cost sequestration in coal," it said.
DOE said that the injection site consists of three CBM-producing wells and a centrally located injection well. The coals, which occur at about 3,000 ft, are about 75 ft thick and are split among three seams over a 175-ft interval. This San Juan coalbed fairway area previously underwent significant CBM production, DOE noted.
It said that in addition to the CO2 injection, the Southwest Regional Partnership plans to use the project's produced water. CBM production typically includes high volumes of produced water, and the project will desalinate some of it and use it to irrigate nearby riparian areas which have been parched by prolonged drought, DOE said. "Resulting vegetation growth should induce additional CO2 uptake, another form of carbon sequestration," it said.
The Southwest Regional Partnership is one of seven managed by the DOE Fossil Energy Office's National Energy Technology to determine the best carbon capture and storage approaches. It is led by the New Mexico Institute of Mining and Technology, and includes the states of Colorado, Oklahoma, New Mexico, Utah, and parts of Arizona, Kansas, and Wyoming. The partnership is conducting five field tests (three geologic and two terrestrial) at various stages of planning and execution, DOE said.
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