Research Progress and Prospects on Microbial Response and Gas Potential in the Coal Gasification Process

As an essential unconventional natural gas resource, China's coalbed methane resources are only commercially exploited in a few areas, such as the Qinshui Basin and the Ordos. The rise of coalbed methane bioengineering makes it possible to realize the conversion and utilization of carbon dioxide through microbial action and the carbon cycle. According to the metabolic behavior of the underground microbial community, if the coal reservoir is modified, it may stimulate the microorganism to continuously produce biomethane to prolong the production life of depleted coalbed methane wells. This paper systematically discusses the microbial response to promoting microbial metabolism by nutrients (microbial stimulation), introducing exogenous microorganisms or domestication of in situ microorganisms (microbial enhancement), pretreating coal to change its physical or chemical properties to improve bioavailability, and improving environmental conditions. However, many problems must be solved before commercialization. The whole coal reservoir is regarded as a giant anaerobic fermentation system. Some issues still need to be solved during the implementation of coalbed methane bioengineering. Firstly, the metabolic mechanism of methanogenic microorganisms should be clarified. Secondly, it is urgent to study the optimization of high-efficiency hydrolysis bacteria and nutrient solutions in coal seams. Finally, the research on the underground microbial community ecosystem and biogeochemical cycle mechanism must be improved. The study provides a unique theory for the sustainable development of unconventional natural gas resources. Furthermore, it provides a scientific basis for realizing the carbon dioxide reuse and carbon element cycle in coalbed methane reservoirs.