Calculation model for water influx and controlled reserves for CBM wells with high water yield

Abstract

Compared with conventional gas reservoir, percolation mechanism of coalbed methane (CBM) is completely different, it is remarkably affected by adsorption/desorption performance, pressure variation and coalbed characteristics. Then it is difficult to calculate the controlled reserves of CBM wells. Moreover, the connection of edge-bottom water or interbedded water by fractures or faults may largely increase the water yield and drainage period, leading to obvious water invasion in some CBM wells. There are few literature about the predicted production for CBM wells with high water yield. Focusing on the unconventional CBM reservoir, methods of pseudo geological reserves and production index curves are adopted to establish the calculation model of water influx and controlled reserves. It further confirms that the calculation model is successfully applicated on the CBM wells at the middle part of Qinshui Basin in China. Keywords: CBM well, High water yield, Water influx, Controlled reserves, Calculation model