Investigating reservoir pressure transmission for three types of coalbed methane reservoirs in the Qinshui Basin in Shan’xi Province, China

Based on the characteristics of seven representative coalbed reservoirs in the Qinshui Basin in Shan’xi Province, China, the reservoirs were classified as gas pressure reservoirs, water pressure reservoirs or hybrid pressure reservoirs. Reservoir modelling technology was adopted to study the 1000 day recoverability and reservoir pressure transmission process of three typical coalbed methane (CBM) wells, each of which represents one of the three coalbed reservoir classifications identified. The results indicate that the three reservoirs are quite different in terms of their drainage performance. For gas pressure reservoirs, reservoir pressure changes in a very small region around the well bore. The gas production of this type of reservoir is very low; hence, integrated coal and gas mining may be appropriate to enhance its recovery. Reservoir pressure propagates further in water pressure reservoirs but declines gradually. The gas recoverability in water pressure reservoirs is also low, which indicates that effective water drainage is the key technology for improving it. The pressure in hybrid pressure reservoirs propagates moderately in the whole effective region. This type of reservoir has the strongest gas recoverability and is suitable for CBM exploitation using surface to reservoir boreholes.