Induced seismicity associated with underground space creation and resource extraction has become a matter of global concern.However,our ability to predict and mitigate anthropogenic geohazards is still woefully inadeq...Induced seismicity associated with underground space creation and resource extraction has become a matter of global concern.However,our ability to predict and mitigate anthropogenic geohazards is still woefully inadequate.This review provides an overview of unloading-induced seismicity and highlights the mechanisms behind fault instability from a view of rock mechanics.Based on numerous fault instability cases,reduction and rotation of in situ stresses on pre-existing faults are possible causes of excavation-induced seismicity.Fault instability during resource extraction is related to many geological and operational factors,including mining depth,pore pressure,stress distribution,and production rate.Most of these cases can be explained by the Mohr-Coulomb failure criterion,and some exceptional cases could offer us new clues to improve the understanding of the mechanisms behind and the ability to predict and mitigate the induced seismic events.The current challenges include how to control remote triggering of fault instability and how to manage unseen threat of undetected faults.Emerging technologies,such as data analytics and machine learning,combining with physical models could be the next frontier for fault instability research.展开更多
Hydraulic fracturing then fluid circulation in enhanced geothermal system(EGS)reservoirs have been shown to induce seismicity remote from the stimulation-potentially generated by the distal projection of thermoporoela...Hydraulic fracturing then fluid circulation in enhanced geothermal system(EGS)reservoirs have been shown to induce seismicity remote from the stimulation-potentially generated by the distal projection of thermoporoelastic stresses.We explore this phenomenon by evaluating stress perturbations resulting from stimulation of a single stage of hydraulic fracturing that is followed by thermal depletion of a prismatic zone adjacent to the hydraulic fracture.We use Coulomb failure stress to assess the effect of resulting stress perturbations on instability on adjacent critically-stressed faults.Results show that hydraulic fracturing in a single stage is capable of creating stress perturbations at distances to 1000 m that reach 10^(-5)-10^(-4)MPa.At a closer distance,the magnitude of stress perturbations increases even further.The stress perturbation induced by temperature depletion could also reach 10^(-3)-10^(-2)MPa within 1000 m-much higher than that by hydraulic fracturing.Considering that a critical change in Coulomb failure stress for fault instability is 10^(-2)MPa,a single stage of hydraulic fracturing and thermal drawdown are capable of reactivating critically-stressed faults at distances within 200 m and 1000 m,respectively.These results have important implications for understanding the distribution and magnitudes of stress perturbations driven by thermoporoelastic effects and the associated seismicity during the simulation and early production of EGS reservoirs.展开更多
基金the support of Start-up Grant from Nanyang Technological University,Singapore.
文摘Induced seismicity associated with underground space creation and resource extraction has become a matter of global concern.However,our ability to predict and mitigate anthropogenic geohazards is still woefully inadequate.This review provides an overview of unloading-induced seismicity and highlights the mechanisms behind fault instability from a view of rock mechanics.Based on numerous fault instability cases,reduction and rotation of in situ stresses on pre-existing faults are possible causes of excavation-induced seismicity.Fault instability during resource extraction is related to many geological and operational factors,including mining depth,pore pressure,stress distribution,and production rate.Most of these cases can be explained by the Mohr-Coulomb failure criterion,and some exceptional cases could offer us new clues to improve the understanding of the mechanisms behind and the ability to predict and mitigate the induced seismic events.The current challenges include how to control remote triggering of fault instability and how to manage unseen threat of undetected faults.Emerging technologies,such as data analytics and machine learning,combining with physical models could be the next frontier for fault instability research.
基金funded by the National Natural Science Foundation of China(Grant Nos.42107163 and 42320104003)support from the G.Albert Shoemaker endowment.
文摘Hydraulic fracturing then fluid circulation in enhanced geothermal system(EGS)reservoirs have been shown to induce seismicity remote from the stimulation-potentially generated by the distal projection of thermoporoelastic stresses.We explore this phenomenon by evaluating stress perturbations resulting from stimulation of a single stage of hydraulic fracturing that is followed by thermal depletion of a prismatic zone adjacent to the hydraulic fracture.We use Coulomb failure stress to assess the effect of resulting stress perturbations on instability on adjacent critically-stressed faults.Results show that hydraulic fracturing in a single stage is capable of creating stress perturbations at distances to 1000 m that reach 10^(-5)-10^(-4)MPa.At a closer distance,the magnitude of stress perturbations increases even further.The stress perturbation induced by temperature depletion could also reach 10^(-3)-10^(-2)MPa within 1000 m-much higher than that by hydraulic fracturing.Considering that a critical change in Coulomb failure stress for fault instability is 10^(-2)MPa,a single stage of hydraulic fracturing and thermal drawdown are capable of reactivating critically-stressed faults at distances within 200 m and 1000 m,respectively.These results have important implications for understanding the distribution and magnitudes of stress perturbations driven by thermoporoelastic effects and the associated seismicity during the simulation and early production of EGS reservoirs.
