微地震监测技术是水力压裂过程监测及压裂效果评价的重要手段。P波初动震源机制解是研究震源参数的有效工具。基于格点搜索算法求解水力压裂裂缝的P波初动震源机制解,进而得到其方位参数——方位角、倾角和滑动角,为压裂裂缝的解释和压裂效果评价提供有效依据。简单介绍了利用P波初动极性信息反演水力压裂裂缝参数的方法原理,并通过水力压裂裂缝模型对该方法的应用效果进行了测试,最后将该方法应用于四川某页岩气压裂井的实际地面微地震监测资料,得到了合理的单裂缝解释结果。
Microseismic monitoring technology is very important for hydraulic fracturing monitoring and hydraulic fracturing response evaluation.P-wave first-motion focal mechanism solution is an efficient tool for focal parameters study.P-wave first-motion focal mechanism solutions for hydraulic fracture are derived with grid search method.The fracture azimuthal parameters that are strike angle,dip angle and slip angle are calculated to serve the hydraulic fracture interpretation and hydraulic fracturing response evaluation.After a brief introduction to the principles of hydraulic fracturing parameters inversion based on P-wave first-motion polarity information,the reliability of the method is demonstrated by numerical simulation data of hydraulic fracturing models.The method is applied on surface microseismic data acquired during the hydraulic fracturing of some shale gas reservoir in Sichuan province,and reasonable hydraulic fracture interpretation result is achieved based on the P-wave first-motion solutions.