An Integrated Method to Mitigate Hazards from Hydraulic Fracturing–Induced Earthquakes in the Duvernay Shale Play

Abstract

Summary In recent decades, a remarkable increase in induced seismicity in the Western Canada Sedimentary Basin (WCSB) has been largely attributed to hydraulic fracturing (HF) operations in unconventional plays. However, a mitigation strategy concerning geological, geomechanical, and operational susceptibilities to HF-induced seismicity has not been well understood. This work proposes an integrated method to mitigate potential risks from HF-induced seismicity in the Duvernay play near Crooked Lake. The geological susceptibility to induced seismicity is evaluated first from site-specific formation pressure and a distance to the Precambrian basement. The regional in-situ stress and rock mechanical properties are then assessed to determine the geomechanical susceptibility to induced seismicity. Next, the operational factors are determined by comparing induced seismicity with operational parameters such as total injection fluids and proppant mass. It is found that regions with a low formation pressure (<60 MPa), a great distance from the base Duvernay to the Precambrian basement (>260 m), a low minimum principal stress (<70 MPa), and a low brittleness index (<0.45) tend to be induced-seismicity-quiescent regions. Finally, a multiple linear regression (MLR)-based approach is proposed by considering the relative importance of different parameters. The MLR analysis indicates that brittleness index, formation pressure, and total injection volume are the top three controlling factors. Three new horizontal wells are drilled and the MLR analysis of these wells using the three most important parameters is conducted. High-resolution monitoring results indicated that 95% of the induced events had a local magnitude of less than 2.0 during and after the HF operations (3-month time window and 5-km well-event distance), among which the maximum magnitude reached ML3.05 (<red light magnitude ML4.0). Therefore, the MLR-based approach was successfully validated, suggesting that this approach can be applied to mitigate potential seismicity risks in upcoming wells in the Fox Creek region. Such a workflow can also be applied to other regions to guide seismicity-free fracturing operations in unconventional plays.