沁水盆地煤层气井压裂效果评估研究
Research on fracturing performance evaluation of coalbed methane well in Qinshui Basin
-
摘要: 为了分析评估煤层气井压裂增产后的生产效果,以沁水盆地煤层气井为实例,通过G函数曲线、时间平方根曲线和双对数函数曲线预测煤层压裂裂缝闭合压力,并建立了煤层气井的地应力模型。基于该地应力模型的结果,将注入摩阻及停泵裂缝净压力2项指标与煤层气井压裂前后产能进行对比,并拟合了煤层气井平均日产气量与该2项指标之间的关系模型。结果表明:预测的煤层地应力与测试结果的误差仅为0.75 MPa;注入摩阻及停泵裂缝净压力与煤层气产能存在较好的相关性,压裂注入摩阻和停泵裂缝净压力越高,裂缝的复杂程度越高且延伸越困难,导致煤层气井产能越低。该理论方法可为煤层气井的地应力模型和压裂后产能效果预测提供参考。Abstract: In order to evaluate productivity after fracturing of coal-bed methane wells, closure stress of coalbed fracture was predicted with Function Curve G, squa re root of time curve, double logarithmic function curve and in-situ stress model of coal was established based on the coalbed methane wells of Qinshui Basin. Accordin g to in-situ stress model, net pressure, fracture friction and production were contrasted. Then a model to evaluate the productivity after fracturing was established with fil tting the correlations between net pressure, fracture friction with productivity. The results showed that the error of the predicted stress and well testing result was 0.75 MPa. There were good relevance between the productivity with net pressure and friction. The higher net pressure and fracture friction were, the more complexity the fra cture would be and the more difficulty the fracture propagation would be. Then the productivity of coalbed methane wells would be low. The methods could provide the r eferences to in-situ stress and production prediction after fracturing of coalbed methane wells.