Migration-based event location for DAS-geophone hybrid microseismic monitoring from a single monitoring well: Hydraulic stimulation case studies for oil/gas and geothermal applications

Single-well microseismic monitoring is a cost-effective option when considering downhole microseismic monitoring of hydraulic treatments et al. in nearby wells. We study the feasibility of a 1C Distributed Acoustic Sensing– 3C geophone hybrid configuration in terms of the event location problem using two datasets: one acquired during the monitoring of a traditional hydraulic stimulation in oil and gas and one in relation to the monitoring of an injection linked to a geothermal field. Both datasets show satisfactory accuracy of the data time-stamping of both the 3C geophone and 1C DAS systems, thus enabling the joint event location process. We used a migration-based approach to determine hypocenters without time picks. As a result of leveraging such a hybrid system, we observe a reduction in event location uncertainty as opposed to when relying on a traditional 3C geophone-only array. The 1C DAS–3C geophone hybrid system has all the characteristics required to successfully replace 3C geophone-only arrays for microseismic event locations.