Comparison of Migration-based Detection and Location Methods for Microseismic Events

Microseismic monitoring in the oil and gas industry commonly uses migration-based methods to locate very weak microseismic events. The objective of this study is to compare the most popular migration-based methods on a synthetic dataset which simulates a strike-slip source mechanism event with low signal-to-noise ratio recorded by surface receivers (vertical components). The results show the significance of including source mechanism inversion in the event detection and location procedure. For detection and location without such a correction the ability to detect weak events is reduced. We show both numerically as well as theoretically that neglecting source mechanism reduces noise suppression during stacking and consequently limits the possibility to retrieve weak microseismic events. On the other hand, even a simple correction to the data polarization used together with otherwise ineffective methods can significantly improve detections and locations. A simple stacking of the data with polarization correction provides clear event detection and location but even better results are obtained using polarization corrected data combined with methods based on semblance and cross-correlation.