煤层气水平井产能控制因素分析及排采实践

摘要

To demonstrate the productivity control factors in coalbed methane （CBM） horizontal wells, based on the method of theoretical analyses, the factors, such as critical desorption pressure, gas saturation and permeability which control CBM horizontal wells＇ productivity were analyzed. Three stages bottom hole pressure （BHP） control method were put forward, the first stage is BHP greater than critical desorption pressure, the second stage is BHP less than critical desorption pressure but greater than 0. 5 times critical desorption pressure, and the third stage is BHP less than 0. 5 times critical desorption pressure. Bottom hole pressure control according to the following principles：the first stage to implement the formation fluid supply capacity,liquid descending amplitude less than 3 m/d;the second stage to implementation of coalbed methane well gas production capacity slowly, liquid descending amplitude 1 m/d;the third stage with stable production, maintenance of bottom hole pressure, when gas production rate decline should descending liquid amplitude 0. 5 m/d. The field application results demonstrate three stages BHP control method can reduce regional pressure, and full improve the CBM well productivity.%为了揭示煤层气水平井产能控制因素，采用理论分析方法分析了临界解吸压力、含气饱和度及渗透率对水平井产能的控制作用。通过山西沁水盆地南部水平井排采实践，提出了三段式管理井底压力的排采方法，即将排采制度分为井底压力大于临界解吸压力阶段、介于临界解吸压力至0．5倍，I盏界解吸压力阶段、小于0．5倍临界解吸压力阶段分别制定降压幅度。井底压力控制遵循：第l阶段落实地层供液能力，降液幅度小于3m／d；第2阶段缓慢提产，落实煤层气井产气能力，降液幅度为1rn／d；第3阶段稳定配产，维持井底压力，产气量出现下降时缓慢降液，降液幅度为0．5m／d。结果表明：三段式管理井底压力的排采方法有利于区域压降扩展和充分释放煤层气井产能。