首页|Implications for fault reactivation and seismicity induced by hydraulic fracturing
Implications for fault reactivation and seismicity induced by hydraulic fracturing
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Evaluating the physical mechanisms that link hydraulic fracturing(HF)operations to induced earth-quakes and the anticipated form of the resulting events is significant in informing subsurface fluid in-jection operations.Current understanding supports the overriding role of the effective stress magnitude in triggering earthquakes,while the impact of change rate of effective stress has not been systematically addressed.In this work,a modified critical stiffness was brought up to investigate the likelihood,impact,and mitigation of induced seismicity during and after hydraulic fracturing by developing a poroelastic model based on rate-and-state fraction law and linear stability analysis.In the new criterion,the change rate of effective stress was considered a key variable to explore the evolution of this criterion and hence the likelihood of instability slip of fault.A coupled fluid flow-deformation model was used to represent the entire hydraulic fracturing process in COMSOL Multiphysics.The possibility of triggering an earth-quake throughout the entire hydraulic fracturing process,from fracturing to cessation,was investigated considering different fault locations,orientations,and positions along the fault.The competition between the effects of the magnitude and change rate of effective stress was notable at each fracturing stage.The effective stress magnitude is a significant controlling factor during fracturing events,with the change rate dominating when fracturing is suddenly started or stopped.Instability dominates when the magnitude of the effective stress increases(constant injection at each fracturing stage)and the change rate of effective stress decreases(the injection process is suddenly stopped).Fracturing with a high in-jection rate,a fault adjacent to the hydraulic fracturing location and the position of the junction between the reservoir and fault are important to reduce the Coulomb failure stress(CFS)and enhance the critical stiffness as the significant disturbance of stresses at these positions in the coupled process.Therefore,notable attention should be given to the injection rate during fracturing,fault position,and position along faults as important considerations to help reduce the potential for induced seismicity.Our model was verified and confirmed using the case of the Longmaxi Formation in the Sichuan Basin,China,in which the reported microseismic data were correlated with high critical stiffness values.This work supplies new thoughts of the seismic risk associated with HF engineering.
Zi-Han Sun、Ming-Guang Che、Li-Hong Zhu、Shu-Juan Zhang、Ji-Yuan Lu、Chang-Yu Jin
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Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,School of Resources and Civil Engineering and Key Laboratory of Liaoning Province on Deep Engineering and Intelligent Technology,Northeastern University,Shenyang,110819,Liaoning,China
Research Institute of Petroleum Exploration & Development,PetroChina Company Limited,Beijing,100084,China
The Exploration and Development Research Institute of Daqing Oilfield Limited Company,Daqing,163458,Heilongjiang,China
joint fund of the National Key Research and Development Program of China国家自然科学基金Open Foundation of National Energy shale gas Research and Development(experiment)center高等学校学科创新引智计划(111计划)
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