An integrated approach to characterize hydraulic fracturing-induced seismicity in shale reservoirs

Abstract

There has been a remarkable increase in induced seismicity in Western Canada and the majority of these events can be related to hydraulic fracturing operations applied to develop unconventional reservoirs. The underlying mechanism of such induced seismicity is still unclear and needs to be investigated to mitigate risks of future events. In this paper, we propose a new integrated approach to characterize hydraulic fracturing-induced seismicity. Inferred faults in the target area were first identified by the ant-tracking approach and hydraulic fractures were characterized by simulating hydraulic fracturing processes. The coupled flow-geomechanics modeling was then performed to compute the Coulomb Failure Stress and determine the reactivation of pre-existing faults. A case study was finally utilized to demonstrate the applicability of the integrated method. Four north-south-oriented faults were interpreted and half-length of hydraulic fractures were calculated from 84 to 127 m. The calculated results of the flow-geomechanics model were in good agreement with the actual induced seismicity spatially and temporally. Three types of triggering mechanisms were accounted for HF-induced seismicity, including hydraulic fractures propagation, the connection between hydraulic fractures and a fault and connections of hydraulic fractures with the natural fractures around the fault. The injection rate could be decreased to mitigate risks of future seismic events.