基于横波分裂的井中微地震资料三分量波场特征分析

Characteristics Analysis of Three-Component Wave Field Based on Borehole Microseismic Data of Shear Wave Splitting

井中微地震压裂裂缝监测资料波场复杂,尤其当横波遇到裂缝时会分裂为偏振方向互相垂直的快、慢两种横波,而如果纵波波场与横波波场及横波分裂后的快、慢横波波场识别错误,会直接影响解释成果的准确性。为了提高井中微地震资料解释成果的准确性,在前人分析的不同裂缝尺度对快、慢横波传播速度影响的基础上,根据不同入射角与检波器三分量之间的关系,分析了纵波、横波、快横波、慢横波在三分量检波器的波场特征,得出利用横波分裂事件定位反演结果会造成压裂裂缝解释误差过大。以新平XX井微地震压裂监测资料为例,分别拾取了纵波、横波、快横波、慢横波微地震记录,通过纵、横波初至拾取的走时反演定位算法,完成了纵波+横波、快横波+慢横波、纵波+快横波+慢横波等波场的微地震定位反演。经对比发现,利用纵波+横波微地震事件定位结果判定事件方位、距离更可靠,其解释的裂缝形态更符合压裂裂缝生长规律,同时也证明了快、慢横波影响井中微地震定位反演结果。

The wave field data which is monitored the fracturing crack by micro seismic in the well is complex,especially when the shear wave(S-wave) encounters the fracture.The shear wave will split into the fast or slow wave.The polarization directions of the two kinds waves are perpendicular to each other.The identification of the shear wave field,the longitudinal wave(P-wave) field and fast or slow wave field,will directly affect the accuracy of the interpretation results.In order to improve the accuracy of interpretation results of microseismic data in wells,the wave field characteristics of waves in three-component geophone are analyzed according to the relationship between different incidence angles and the three components of the geophone,and it is concluded that the inversion results of the S-wave splitting event will cause fracture interpretation errors.Taking the micro-seismic fracture monitoring data of the Xinping XX well as an example,collect the micro-seismic records data of the P-wave,S-wave and fast/slow shear waves separately.Using the travel time inversion positioning algorithm of the first break collecting of the P/S waves,complete the micro-seismic positioning inversion of the P-wave + S-wave,fast S-wave + slow S-wave,P-wave + fast S-wave + slow S-wave fields.Through comparison,it is found that the orientation and distance of microseismic event localization results using only P-wave and S-wave are more reliable,and the fracture morphology is more consistent with the fracture growth law.At the same time,the influence of fast and slow S-wave on microseismic localization inversion results is fully explained.