Numerical simulation of the influence of no-flow recharge aquifer on CBM drainage

Coalbed methane wells in southern Qinshui Basin have the characteristics of high water yield and low gas yield, while some wells present high water yield and high gas yield characteristics. Generally speaking, the high water yield of coalbed methane wells is mostly related to the aquifer with recharge. In this case, based on the coal reservoir geological condition of Shizhuangnan Block and the actual situation of coalbed methane vertical well production, the influence of non-flow recharge aquifer on reservoir pressure variation and CBM outflow rule was simulated by using a three-dimensional coal reservoir simulation software (SIMEDWin) with gas and water two phases and multiple components. The simulation results show that compared with the CBM Wells without connected aquifer, the CBM Wells that communicate with the confined aquifer without leakage water complement have significant pressure drop range in the far well zone, the time of high gas production is long, with large cumulative gas production and water discharge, but late gas discovery time. The higher the permeability of aquifer, the higher the peak value of gas production of the CBM Wells. The higher the daily water discharge of a gas well, the faster the gas will be produced, but the production rate will not increase when water discharge reaches a certain value. Considering comprehensively, similar to the high-permeability aquifer(lens aquifer) in Shizhuangnan Block, increasing the daily displacement to a certain value is more conducive to the increase of CBM production.