An Efficient Method for Velocity Calibration and Prediction of Microseismic Event Location Using very Fast Simulated Annealing

摘要

Velocity calibration and estimation of microseismic event location are two important ingredients in microseismic monitoring. It is generally considered that the accurate estimation of microseismic event location depends on the accurate velocity structure. In this paper, very fast simulated annealing (VFSA) is first applied to invert velocity structure between the treatments well and the monitoring well by using perforation shot travel time data, and then is implemented to locate the microseismic events using the velocity structure obtained above. Unlike previous applications of VFSA using the objective function of misfit between the theoretical travel time and the observed travel time, we propose a novel objective function for VFSA which consists of the travel time differences of P-wave first arrivals between seismic traces. The P-wave first arrival travel time is calculated by means of a shooting ray tracing method. To illustrate the efficiency of the proposed method, a flat-layered model test is performed by considering the uncertainty of travel time picking. The numerical results indicate that the predicted microseismic event locations have a good match with the true values although the inverted velocity structure is not so accurate.