The U.S. Department of Energy (DOE) and its Southwest Regional Partnership (SWP) are testing a way to permanently store carbon dioxide (CO2) and simultaneously recover natural gas in a large coalbed methane (CBM) area in the San Juan Basin of New Mexico.

In a six-month demonstration, the SWP plans to inject up to 35,000 tons of CO2 in the basin near Navajo City, NM. Unlike other enhanced CBM recovery projects, the demonstration could show how to permanently store the greenhouse gas through geologic carbon sequestration.

Many coalbeds in the United States are saturated with methane but the gas is difficult to extract because methane chemically binds to coal. CO2 also has a tendency to bind to coal. Injecting CO2 into the coalbed essentially would displace the methane and make the gas easier to produce, according to the DOE.

The San Juan Basin was selected because the coals are considered exceptionally permeable, at least compared with other regional coalbeds, with “favorable geology, high methane content, available CO2 from nearby power plants, low capital and operating costs, and well developed natural gas and CO2 pipelines,” the DOE noted.

The injection site consists of three CBM-producing wells and a centrally located injection well. The coals, which occur at depths of about 3,000 feet, are 75 feet thick and are split among three seams over a 175-foot interval. The area selected previously has undergone “significant” CBM production, DOE noted.

Besides injecting CO2 into the coal seams, the SWP intends to make use of the project’s produced water. CBM production typically results in a lot of produced water, and the demonstration project would recover some of the produced water, desalinate it and use it to irrigate nearby riparian areas stressed by prolonged drought. Resulting vegetation growth should induce additional CO2 uptake, another form of carbon sequestration, said the DOE.

DOE’s Regional Carbon Sequestration Partnership Program, managed by the Office of Fossil Energy’s National Energy Technology Laboratory, includes seven partnering regions established to determine the best approaches to capture and permanently store CO2. The SWP is led by the New Mexico Institute of Mining and Technology and includes the states of Colorado, Oklahoma, New Mexico, Utah and portions of Arizona, Kansas, Texas and Wyoming.

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