Time-difference Based Microseismic Traveltime Inversion

Microseismic monitoring of well stimulation by hydraulic fracturing is now a routine commercially-applied technology. A thorough knowledge of the velocity structure between the treatment well and monitoring well is essential to achieve the most accurate microseismic event location. Currently, this velocity model is oftenbuilt from dipole-sonic data or from a combination of sonic data and perforation shot (or string shot, even drop ball data from latest technology). Theoretically, the origin time of perforation shot must be known, and itaffects the accuracy of velocity structure, consequently the accuracy of subsequent location results. Unfortunately, it’s very difficult to obtainthe origin time.Therefore, we demonstrate an inversion procedure to calibrate the velocity model without origin time but using differential arrival times. Comparing with traditional methods, we combine traveltime data, such as differential P-P arrival times, differential S-S arrival times, and differential S-P arrival times. Using these three types of data information could help reduce the dependence on the event origin time.Both synthetic examples and real data results show the improvement and effectiveness of the microseismic traveltime inversion method, which will be instructive and meaningful to industrial production.