CO2 sequestration in deep coal seams:: Pilot results and worldwide potential

A new natural gas production technology has the potential to sequester carbon dioxide at a net profit. Injection of carbon dioxide into deep coal seams can enhance methane recovery, while simultaneously sequestering a greenhouse gas. Initial results from the world's first carbon dioxide - enhanced coalbed methane (CO2-ECBM) pilot in the southwestern United States show this new technology to be technically and economically feasible. Since 1996, operator Burlington Resources has sequestered over 57 million m(3) (2 Bcf) of CO2 in Cretaceous Fruitland coal seams at their Allison Unit production pilot, located in the northern San Juan basin. Methane recovery and dewatering of the reservoir also is improved. Based on current costs and performance, CO2-ECBM may be profitable in the San Juan and nearby basins at prevailing wellhead natural gas prices of US$0.06 to $0.07/m(3) ($1.75 to $2.00/Mcf), representing an estimated 8.5 Gt of CO2 sequestration potential. Geologic and reservoir conditions must be favorable for economic application of CO2-ECBM technology. It is not sufficient for a project simply to have a CO2 waste stream and nearby coal deposits. This is because most coal deposits have unfavorably low permeability, particularly in complex geologic settings such as Western Europe or northeastern China. Test sites should be selected primarily based on favorable site-specific reservoir and surface infrastructure conditions, as well as the applicability of the test to worldwide coal basins with similar geology. Reservoir screening criteria for successful application of CO2-ECBM include: laterally homogeneous and permeable coal seams, concentrated seam geometry, and minimal faulting and reservoir compartmentalization. The technology for implementing and operating CO2-ECBM recovery is based on demons:rated oilfield technology, although further refinements are needed. Apart from the San Juan basin, many other coal basins have significant CO2-ECBM potential. In the U.S., the Uinta and Raton basins are geologically most favorable, while additional potential exists in the Greater Green River, Appalachian and other coal basins. Coal basins in Australia, Russia, China, India, Indonesia, Canada and other countries also have large CO2-ECBM potential, estimated at 150 Gt. Cash-flow analysis of representative CO2-ECBM projects indicates that 5 to 15 Gt could conceivably be sequestered at a net profit, while about 60 Gt of sequestration capacity may be available at moderate costs of under $50/t, Many additional coal basins were not assessed and could add further sequestration potential.