Microseismic Location in EGS: Comparing Picking-based and Source-imaging Workflows on Downhole DAS Data

Abstract

Accurate microseismic locations are essential for developing and monitoring enhanced geothermal systems (EGS). Joint use of downhole geophones and distributed acoustic sensing (DAS) can boost detection and location performance, but conventional picking-based workflows perform sub-optimally on DAS data because individual channels are noisy. In addition, DAS’s unidirectional measurements cause blind spots that depend on acquisition geometry and source location, focal mechanism, and subsurface structure. We compare a traditional, picking-based locator with a picking-free source-imaging workflow that jointly exploits P- and S-wave phases on DAS and geophones. The source-imaging method applies an STA/LTA transform to enhance P-wave coherence and mitigate blind spots due to DAS directivity. Our analysis clarifies the strengths and downsides of each approach and shows that combining them improves catalog completeness and location accuracy and resolution, with specific benefits for real-time detection of shear onset and runaway slip. These results inform real-time monitoring, risk assessment, and stimulation planning in EGS operations.