沁水盆地寿阳区块煤层气井高产水影响因素

Controls on High Water Production of CBM Wells in Shouyang Block,Qinshui Basin

为揭示沁水盆地寿阳区块煤层气井产水异常高的主控因素,对该区的区域水文地质条件、煤层与顶底板及其含水层岩性组合关系以及不同压裂工艺对煤层气井产水特征的影响进行了系统分析,指出了导致寿阳区块煤层气井高产水的地质风险和工程风险,并提出了相应的规避措施。研究结果表明:压裂施工排量过大(>7 m3/min)形成的压裂缝高过大,沟通了煤层附近的含水层,这是导致煤层气井高产水的直接原因;煤系地层中发育的高角度裂缝性含水砂岩层以及断层是导致煤层气井高产水的关键地质风险。此外,顶底板岩性厚度以及区域水文地质条件也是造成该区煤层气井高产水的重要因素。因此,降低压裂施工排量、规避围岩中的高角度裂缝性含水层、远离断层、选择厚层的顶底板泥岩发育区是降低煤层气井高产水的重要手段。

In order to reveal the controlling factors causing high water production of coalbed methane（ CBM）wells in Shouyang block,Qinshui Basin,this paper makes a systematic analysis of the impacts of regional hydrogeological conditions,lithological association of coal seams and roofs and floors as well as aquifers,and fracturing techniques on water production of CBM wells,summarizes the geological risk and engineering risk leading to high water production,and finally brings in measures to avoid those risks.Results show that too high fracturing pumping rate is the immediate cause of high water production of CBM wells due to hydraulic connection between coal seams and aquifers,and high angle fractured aquifers nearby coal reservoirs in coal measure strata is the critical geological risk causing high water production of CBM wells.Additionally,unfavorable lithological association and regional hydrogeological conditions are the important factors causing high water production of CBM wells.Therefore,decreasing fracturing pumping rate,avoiding high angle fractured aquifers,and choosing coal seams which develops thick argillaceous roof and floors are the important measures to limit water production of CBM wells.