Improving Coal Gas Recovery with Microbially Enhanced Coalbed Methane

Microbially enhanced coalbed methane (MECoM) imitates and enhances the natural process of secondary biogenic gas generation in coal beds that occurs in coal basins worldwide. MECoM involves the introduction of anaerobic bacterial consortia, which consists of hydrolyzers, acetogens and methanogens, and/or nutrients into coalbed methane wells. Coalbed methane production may increase through generation of additional methane, removal of pore-plugging coal waxes, and permeability enhancement as cleat-aperture size increases during biogasification. The amount of coal gas potentially generated by MECoM is large. If only one-hundredth of 1% (1/10,000) of U.S. (lower 48) coal resources were converted into methane using MECoM, gas resources would increase by 23 Tcf, or approximately 16% of current lower 48 nonassociated reserves. However, coal surface area and biogasification reaction rates in the subsurface may potentially limit gas generation, indicating that permeability enhancement may be the most significant benefit of MECoM. Additional research, including microbial sampling of deeply buried bituminous coals to identify genetically unique bacterial consortia, is required to fully evaluate MECoM and determine if the process will improve coalbed methane producibility. Successful implementation of MECoM requires an integrated approach towards understanding the geologic, hydrologic, organic and inorganic geochemistry, microbiological, and engineering factors that may limit MECoM in the subsurface. If economically feasible, MECoM can generate methane in coal beds that currently have limited coalbed methane potential, and thereby provide cheap, environmentally clean energy for many parts of the world.