水力压裂微地震震源定位与震源机制联合反演研究

Joint inversion of source location and microseismic focal mechanism

传统地面微地震监测资料处理流程中通常先进行震源定位然后进行震源机制反演,这样做会将震源定位误差引入到震源机制反演中去;而采用同时离散位置与震源机制空间的反演方法由于搜索格点太多而影响计算效率。介绍了一种迭代的震源定位与震源机制联合反演方法,在迭代过程中利用P波初动震源机制反演结果校正定位的目标函数,校正定位后采用P波辐射花样约束反演震源机制。该方法在提高震源定位和震源机制反演精度的同时大大降低了计算量。理论模型和四川盆地某压裂井微地震地面监测应用结果表明,该方法在实际应用中稳定、可靠且高效。

In the traditional workflow for microseismic monitoring,location comes first and focal mechanism inversion second;however,this workflow may introduce location errors into the focal mechanism inversion.The method for the joint inversion of a location and focal mechanism involves discretizing the space of the location and focal mechanism simultaneously,and its computing efficiency is affected due to the large number of search grids required.Therefore,an iterative joint inversion of the location and focal mechanism is proposed.In this iterative process,the inversion result of the P-wave first-kinetic focal mechanism is used to correct the target function of the location,and then the focal mechanism is inverted using the P-wave radiation pattern as a constraint.This method can improve the accuracy of the location and focal mechanism inversion while reducing the calculation required.Tests of synthetic data and microseismic monitoring data from a fracturing well in the Sichuan Basin,China,have verified the robustness,accuracy,and efficiency of the proposed method.