Geochemical characteristics and genetic types of coalbed methane in the Huainan and Huaibei Coalfields, China

This work targets the geochemical characteristic and genetic evolution of coalbed methane in the Huainan and Huaibei Coalfields. Gas samples were collected for component and stable isotope tests, with genetic discrimination charts and end-member mixing models adopted to identify gas types and quantify gas proportions. CH4 concentration is 70.25–98.58% (average of 87.17%). δ13CCH4 and δ13DCH4 values fall between −65.90 to −33.87‰ and −221.50 to −151.12‰ respectively. coalbed methane (CBM) samples are the mixtures of thermogenic and secondary biogenic gases, with the latter mainly generated by CO2 reduction. Quantitatively, thermogenic gas averages 61.56% and biogenic gas averages 38.44%. In addition, the gas experienced multi-stage evolution of thermal generation, uplift dissipation and microbial recharge. This study quantifies gas mixing signatures and elaborates on relevant geological controls, which provides basis for the favorable area prediction of coalbed methane in the Huainan and Huaibei Coalfields.