Comparative Analysis of Coalbed Methane Well Productivity in Eastern Yunnan

The water produced from coalbed methane (CBM) wells contains abundant geochemical information; therefore, analyzing the geochemical information available therein is of great significance for the efficient exploitation of CBM wells. Based on the geochemical characteristics of water from four CBM wells in eastern Yunnan, this paper analyzes the relationship between the geochemical characteristics of the produced water and gas production. The results indicate that the underground environment in which water is produced in the four CBM wells in the study area exists in a closed state. The water sourced from wells L-1 and L-2 is of the Na-Cl-HCO₃ type, whereas the water sourced from wells L-3 and L-4 is of the Na-HCO₃ type. Gas production is approximately positively correlated with high concentrations of HCO₃⁻, up to concentrations of 2800 mg/L, beyond which gas production decreases. Both D drift and ¹⁸O isotope drift in the produced water are beneficial for the production of CBM. The trace element content of the well water is influenced by the trace elements found in the coal seams and surrounding rocks, especially at peak trace element contents. The dissolved inorganic carbon isotope (¹³C_DIC) in the well water is affected by microbial methanogenesis and carbonate dissolution, and gas production is high when ¹³C_DIC is approximately −4‰.