Transition of biogenic coal-to-methane conversion from the laboratory to the field: A review of important parameters and studies

Coalbed methane (CBM) is an important unconventional natural gas resource in the U.S. and around the world. Many of the CBM containing coal formations are home to microbial communities producing the gas by converting coal to methane. Biogenically produced CBM provides an opportunity for developing technologies to enhance the microbial processes and increase the recoverable gas. To transfer strategies for biogenic CBM enhancement from small-scale laboratory studies to large-scale commercial applications in subsurface coal beds, there are several factors that should be considered to facilitate this transfer. Coal rank, chemistry and structure, formation water chemistry, as well as microbial communities can vary widely among coal formations, and matching these components in laboratory studies to each other and the coal bed of interest should be considered. More work is required to understand the effects of gas sorption, pressure, and water movement through coal formations on biogenic gas production. Additionally, methods for applying methane enhancement strategies in situ must be further investigated to develop commercial applications of enhanced microbial coalbed methane production.