The injection of nitrogen and/or carbon dioxide into coalbed methane reservoirs can materially improve gas recoveries. The reservoir mechanisms responsible for enhancing recovery, while based on similar principles, are fundamentally different for each gas. Nitrogen acts to strip the methane from the coal matrix resulting in an immediate production increase, but also leads to early breakthrough times. Carbon dioxide acts to displace the methane from the coal matrix, resulting in a slower response at the production well, but provides a delay in the time to breakthrough. While site specific, laboratory and simulation studies have indicated that field recoveries can be significantly improved with the application of enhanced coalbed methane recovery (ECBM) technology.
Integrated reservoir studies of multi-well pilot tests of ECBM technology in the San Juan basin, funded by the U.S. Department of Energy’s CO2 sequestration program, are now being performed to better understand the reservoi