Microseismic Event Location Using Migration-Based Stacking With Effective Parameters’ Optimization

Microseismic monitoring has emerged as a critical technique for exploiting tight reservoirs, particularly those involving hydraulic fracturing, such as shale gas and coalbed methane. The conventional migration-based stacking location method for surface microseismic events relies heavily on the accuracy of the velocity model. However, obtaining an accurate 3-D velocity model is often challenging, prompting the common use of 1-D layered velocity models derived from well-logging data or constant velocity models calibrated through perforation shots. To enhance the precision of microseismic event localization and improve practical applicability, we introduce a refined migration-based stacking location method incorporating two depth-dependent effective parameters: stacking velocity and heterogeneity factor. Two effective parameters were found to describe wave raypath through heterogeneity media, which can be estimated by semblance-based scanning technology. Furthermore, to address potential errors in the velocity model and residual statics arising from topographical variations, we incorporate microseismic event moveout-corrected gathers for residual static corrections. This additional step further refines the accuracy of microseismic event locations. Another advantage of our proposed method is its ability to directly compute the theoretical travel time during the migration-based location process, eliminating the need for precomputing and storing a traveltime table. The efficacy and practicality of our method are demonstrated through applications to both synthetic model data and field data examples.