TY - JOUR
T1 - Temperature and Fluid Pressurization Effects on Frictional Stability of Shale Faults Reactivated by Hydraulic Fracturing in the Changning Block, Southwest China
AU - An, Mengke
AU - Zhang, Fengshou
AU - Chen, Zhaowei
AU - Elsworth, Derek
AU - Zhang, Lianyang
N1 - Funding Information:
This research is supported by the key innovation team program of innovation talents promotion plan by Ministry of Science and Technology of the People's Republic of China (2016RA4059), National Natural Science Foundation of China (41672268 and 41941018), and Fundamental Research Funds for the Central Universities (22120200081). We thank Changrong He, Jianye Chen, Lei Zhang, Xi Ma, Wenming Yao, and Yang Liu for their technical support in conducting the friction experiments and SEM observations and calculating the friction parameters. Useful discussions with Yi Fang and Chris Marone are also greatly appreciated. We thank the editors and two reviewers for their instructive suggestions to improve the manuscript.
PY - 2020/8/1
Y1 - 2020/8/1
N2 - A shale fault reactivated during multistage hydraulic fracturing in the Changning block in the Sichuan Basin, southwest China, accompanied a cluster of small earthquakes with the largest reaching ML ~ 0.8. We illuminate the underlying mechanisms of fault reactivation through measurements of frictional properties on simulated fault gouge under hydrothermal conditions. Velocity-stepping experiments were performed at a confining pressure of 60 MPa, temperatures from 30 to 300°C, pore fluid pressures from 10 to 55 MPa, and shear velocities between 0.122 and 1.22 μm/s. Results show that the gouge is frictionally strong with coefficient of friction of 0.6–0.7 across all experimental conditions. At observed in situ pore fluid pressure (30 MPa), the slip stability response is characterized by velocity strengthening at temperatures of 30–200°C and velocity weakening at temperatures of 250–300°C. Increasing the pore fluid pressure can increase values of (a − b) at temperatures ≥200°C, narrowing the temperature range where velocity weakening occurs. At the in situ temperature (90°C), the simulated gouge shows only velocity strengthening behavior and aseismic slip at elevated pore fluid pressures, contrary to the observed seismicity. We postulate that the aseismic slip at elevated pore fluid pressures may trigger seismicity by activating adjacent earthquake-prone faults.
AB - A shale fault reactivated during multistage hydraulic fracturing in the Changning block in the Sichuan Basin, southwest China, accompanied a cluster of small earthquakes with the largest reaching ML ~ 0.8. We illuminate the underlying mechanisms of fault reactivation through measurements of frictional properties on simulated fault gouge under hydrothermal conditions. Velocity-stepping experiments were performed at a confining pressure of 60 MPa, temperatures from 30 to 300°C, pore fluid pressures from 10 to 55 MPa, and shear velocities between 0.122 and 1.22 μm/s. Results show that the gouge is frictionally strong with coefficient of friction of 0.6–0.7 across all experimental conditions. At observed in situ pore fluid pressure (30 MPa), the slip stability response is characterized by velocity strengthening at temperatures of 30–200°C and velocity weakening at temperatures of 250–300°C. Increasing the pore fluid pressure can increase values of (a − b) at temperatures ≥200°C, narrowing the temperature range where velocity weakening occurs. At the in situ temperature (90°C), the simulated gouge shows only velocity strengthening behavior and aseismic slip at elevated pore fluid pressures, contrary to the observed seismicity. We postulate that the aseismic slip at elevated pore fluid pressures may trigger seismicity by activating adjacent earthquake-prone faults.
KW - fluid pressurization
KW - frictional stability
KW - high temperature
KW - hydraulic fracturing
KW - reactivated shale fault
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U2 - 10.1029/2020JB019584
DO - 10.1029/2020JB019584
M3 - Article
AN - SCOPUS:85089847674
VL - 125
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
SN - 2169-9380
IS - 8
M1 - e2020JB019584
ER -