全干涉成像的微地震定位方法研究

基于偏移成像的微地震定位方法由于可避免走时拾取误差以及可实现自动化定位等优点被广泛应用.绕射叠加方法将能量沿走时曲线聚焦到空间网格点上,进行成像时需要搜索发震时刻.干涉成像方法利用互相关提取的走时差信息可避免搜索发震时刻,但定位结果受数据信噪比的影响较大.为了进一步提高干涉成像法的定位精度,本文提出一种同时使用互相关和自相关道集的全干涉成像方法,增加的自相关道集提取的S-P走时差可降低震源-检波器方向的定位误差,提高定位精度.单井监测的理论测试和实际数据的研究结果表明,全干涉成像的定位精度高于仅使用互相关道集的干涉成像方法,同时计算效率高于绕射叠加方法.

Full-interferometry imaging method for microseismic location

The migration-based source location methods have been widely used due to their robustness and automatism for detecting and locating weak microseismic events. Of them, the diffraction stacking method locates the event by stacking the amplitudes of seismic traces along the diffraction travel time curve, while it needs searching the origin time. The interferometry imaging method utilizes differential arrival times obtained by the cross-correlograms, which can avoid searching the origin time. However, its location results are sensitive to the signal-to-noise ratio of data. To solve this problem, this work proposes a full-interferometry imaging method which combines cross-correlograms and auto-correlograms to improve the location accuracy. The S-P differential traveltimes obtained by auto-correlograms can reduce the location errors along the direction of source-receiver. The numerical tests on the downhole monitoring model and research on field data indicate that the full-interferometry imaging method can obtain more accurate locations compared with the interferometry imaging method, and also improve the computational efficiency compared with the diffraction stacking method.