Study on coalbed methane accumulation characteristics and favorable areas in the Binchang area, southwestern Ordos Basin, China

Abstract

article The Binchang area of southwestern Ordos Basin is one of the most promising areas for low-rank coalbed methane (CBM) in China. This work investigates the Jurassic Yanan Formation coal and CBM geology and accumulation characteristics of CBM in the southwestern Ordos Basin based on data from 46 wells and labo- ratory measurements of 14 coal samples from 7 mines. The results show that coal rank in the Binchang area is mainly sub-bituminous A and high-volatile C bituminous (0.46%-0.73%Ro). Coals are dominated by inertinite (14.7-85.6%); less abundant are vitrinite (8.5-77.7%) and liptinite (1.5-15.2%). Minerals are found only in small amounts (0.4-8.3%). Permeability is between 0.04 and 25.3 mD, and porosity ranges from 2.4% to 20.1%. Most coal pores are less than 100 nm in diameter, making them favorable for gas adsorption but unfavorable for gas permeability. Pore morphology is represented mainly by micro- and mesopores with a well-connected and ink-bottle shaped (narrow throat and wide body) morphology. These coals are charac- terized by a high adsorption volume of more than 3.0×10 �3