Reformation of coal reservoirs by microorganisms and its significance in CBM exploitation

Abstract

The study investigates the variations in surface morphology and micro-nano-scale pore structure of coal matrix during the process of biodegradation. Comprehensive reservoir characterization techniques, including field emission scanning electron microscope, mercury intrusion porosimetry, and low-temperature N2 adsorption, are employed on four anthracite samples. The significance of the relationship between coal reservoir bio-reformation and coalbed methane (CBM) exploitation is proposed. The main findings indicate that organic matter on the surface of the coal matrix can undergo biodegradation, resulting in the generation of new pores. Microbial metabolism does not alter pore type but only modifies pore size and volume of coal. After microbial degradation, there is an increase in average pore width, while both Brunauer-Emmett-Teller specific surface area and Barrett-Joyner-Halenda pore volume decrease. Furthermore, bioconversion leads to a reduction in both surface and volume dimensions of coal, resulting in a smoother coal matrix surface and simplified complexity of its pore structure. This benefits desorption, migration, and exploitation of CBM. These findings further reinforce the pivotal role of microbial-enhanced coalbed methane production technology in improving CBM production and promoting the clean utilization of coal resources.