地面与井中观测条件下的微地震干涉逆时定位算法

Microseismic events location of surface and borehole observation with reverse-time focusing using interferometry technique

勘探和开发非常规油气藏已经成为国际油气工业界的新热点.由于这类油藏具有低渗透率的特点,开采过程中往往需要多级压裂形成能够使烃类自由流动的裂隙.通过定位分析压裂过程中诱导的微地震震源能够帮助人们刻画裂缝属性(走向、密度等),评价压裂效果,分析断裂模式,推定震源机制等.微地震定位可以采用波动方程逆时聚焦方法实现.由于微地震数据信噪比低,加之速度模型不准确、稀疏观测等诸多因素使得定位的精度大打折扣.本文将波动方程逆时聚焦定位原理与干涉"成像"原理相结合,探讨多源微地震信号的干涉逆时定位算法,尤其扩展该算法到三维多分量地面、井中以及井地联合观测条件下.通过理论合成数据与实际射孔资料的数值试验,展示了该微地震定位算法的精度优势与抗噪特点,并指出波场聚焦微地震定位方法在实际应用中的制约因素与应对策略.

Development and recovery of unconventional reservoir has become a new central issue of international hydrocarbon industry.For the unconventional reservoir has the characteristic of low-permeability usually,multiple stages of hydraulic fracturing are usually required to create connected cracks through which hydrocarbons can flow.We can characterize the crack attributes （i.e.,direction,density,etc.）,evaluate the effect of hydro-fracturing,analyze the rupture pattern,speculate the source mechanisms by locating and analyzing the induced microseismic events.Microseismic events locating can be achieved by using reverse-time focusing technique.But many factors such as high noise,velocity errors,and sparsely-sampled data will cause remarkable location errors.In this study,we focus on combining the reverse-time focusing technique with interferometric imaging condition,and investigate the multi-sources locating method using the multi-component data on the earth surface,in the well,and combined well and surface especially.Synthetic examples and case study reveal the advantage of suppressing artifacts and increasing accuracy.At the same time we point out the constraint of reverse-time focusing method in practical application,and provide some tactics.