Strength theory is the basic theory for calculating and designing the strength of engineering materials in civil,hydraulic,mechanical,aerospace,military,and other engineering disciplines.Therefore,the comprehensive st...Strength theory is the basic theory for calculating and designing the strength of engineering materials in civil,hydraulic,mechanical,aerospace,military,and other engineering disciplines.Therefore,the comprehensive study of the generalized nonlinear strength theory(GNST)of geomaterials has significance for the construction of engineering rock strength.This paper reviews the GNST of geomaterials to demonstrate the research status of nonlinear strength characteristics of geomaterials under complex stress paths.First,it systematically summarizes the research progress of GNST(classical and empirical criteria).Then,the latest research the authors conducted over the past five years on the GNST is introduced,and a generalized three-dimensional(3D)nonlinear Hoek‒Brown(HB)criterion(NGHB criterion)is proposed for practical applications.This criterion can be degenerated into the existing three modified HB criteria and has a better prediction performance.The strength prediction errors for six rocks and two in-situ rock masses are 2.0724%-3.5091%and 1.0144%-3.2321%,respectively.Finally,the development and outlook of the GNST are expounded,and a new topic about the building strength index of rock mass and determining the strength of in-situ engineering rock mass is proposed.The summarization of the GNST provides theoretical traceability and optimization for constructing in-situ engineering rock mass strength.展开更多
The Longmaxi shale is an extensive,prolific unconventional play in southwestern China.Its development in the Changning area is affected by ineffective hydraulic fracturing(HF)stimulation,fault reactivation and casing ...The Longmaxi shale is an extensive,prolific unconventional play in southwestern China.Its development in the Changning area is affected by ineffective hydraulic fracturing(HF)stimulation,fault reactivation and casing damage.It is suspected that the stress contrast within and between the shale reservoirs and the formations above and below matters to hydraulic fracture propagation and reservoir stimulation.To this end,the Longmaxi shale in the Changning area deserves a dedicated quantification of the in situ stress state and its variations.In this study,we re-visit the available data from one of the play’s first appraisal wellbores(X01)for an integrated geomechanics study,focusing on profiling the stress across the Longmaxi and its adjacent formations.Combining geophysical logs and other stress indicators,we re-interpret its stress profile in the context of lithological variations.The resulting stress variations are modeled primarily through a viscoplastic stress relaxation framework,compared with the results via the frictional equilibrium and an elastic theory(the Extended Eaton model).We offer some discussions on the differences and similarities of these stress profiling methods,and examine their applicability to Longmaxi shale in the Changning area.Our objective is to connect the lithology-controlled stress variations to the first-order complexities(HF ineffectiveness and fault reactivation)that have been observed in the area to date.展开更多
We apply binary logistic regression to correlate fracture shear-slip criticality to hydraulic conductivity using data from four deep scientific boreholes in fractured crystalline rocks.In each borehole,an optimized de...We apply binary logistic regression to correlate fracture shear-slip criticality to hydraulic conductivity using data from four deep scientific boreholes in fractured crystalline rocks.In each borehole,an optimized decision boundary is obtained by maximizing the joint probability of classifying all fractures in consideration as critical or not.All four cases feature an optimized decision boundary close to the empirical rock friction(μ=0.6),corroborating the applicability of laboratory-derived friction coefficients to faults in situ.Utilizing this statistical technique,we demonstrate that one can determine the in situ stress orientation and relative magnitude based only on whether fractures of varied orientations are hydraulically conductive,or not.The stress inversion results are consistent with independent stress measurements in each of the four case studies.展开更多
基金This research was financially supported by the National Natural Science Foundation of China(Nos.51934003,52334004)Yunnan Innovation Team(No.202105AE 160023)+2 种基金Major Science and Technology Special Project of Yunnan Province,China(No.202102AF080001)Yunnan Major Scientific and Technological Projects,China(No.202202AG050014)Key Laboratory of Geohazard Forecast and Geoecological Restoration in Plateau Mountainous Area,MNR,and Yunnan Key Laboratory of Geohazard Forecast and Geoecological Restoration in Plateau Mountainous Area.
文摘Strength theory is the basic theory for calculating and designing the strength of engineering materials in civil,hydraulic,mechanical,aerospace,military,and other engineering disciplines.Therefore,the comprehensive study of the generalized nonlinear strength theory(GNST)of geomaterials has significance for the construction of engineering rock strength.This paper reviews the GNST of geomaterials to demonstrate the research status of nonlinear strength characteristics of geomaterials under complex stress paths.First,it systematically summarizes the research progress of GNST(classical and empirical criteria).Then,the latest research the authors conducted over the past five years on the GNST is introduced,and a generalized three-dimensional(3D)nonlinear Hoek‒Brown(HB)criterion(NGHB criterion)is proposed for practical applications.This criterion can be degenerated into the existing three modified HB criteria and has a better prediction performance.The strength prediction errors for six rocks and two in-situ rock masses are 2.0724%-3.5091%and 1.0144%-3.2321%,respectively.Finally,the development and outlook of the GNST are expounded,and a new topic about the building strength index of rock mass and determining the strength of in-situ engineering rock mass is proposed.The summarization of the GNST provides theoretical traceability and optimization for constructing in-situ engineering rock mass strength.
基金sponsored by Research Institute of Petroleum Exploration and Development(RIPED),China National Petroleum Corporation(CNPC)through an international collaborative grant(No.17064).
文摘The Longmaxi shale is an extensive,prolific unconventional play in southwestern China.Its development in the Changning area is affected by ineffective hydraulic fracturing(HF)stimulation,fault reactivation and casing damage.It is suspected that the stress contrast within and between the shale reservoirs and the formations above and below matters to hydraulic fracture propagation and reservoir stimulation.To this end,the Longmaxi shale in the Changning area deserves a dedicated quantification of the in situ stress state and its variations.In this study,we re-visit the available data from one of the play’s first appraisal wellbores(X01)for an integrated geomechanics study,focusing on profiling the stress across the Longmaxi and its adjacent formations.Combining geophysical logs and other stress indicators,we re-interpret its stress profile in the context of lithological variations.The resulting stress variations are modeled primarily through a viscoplastic stress relaxation framework,compared with the results via the frictional equilibrium and an elastic theory(the Extended Eaton model).We offer some discussions on the differences and similarities of these stress profiling methods,and examine their applicability to Longmaxi shale in the Changning area.Our objective is to connect the lithology-controlled stress variations to the first-order complexities(HF ineffectiveness and fault reactivation)that have been observed in the area to date.
文摘We apply binary logistic regression to correlate fracture shear-slip criticality to hydraulic conductivity using data from four deep scientific boreholes in fractured crystalline rocks.In each borehole,an optimized decision boundary is obtained by maximizing the joint probability of classifying all fractures in consideration as critical or not.All four cases feature an optimized decision boundary close to the empirical rock friction(μ=0.6),corroborating the applicability of laboratory-derived friction coefficients to faults in situ.Utilizing this statistical technique,we demonstrate that one can determine the in situ stress orientation and relative magnitude based only on whether fractures of varied orientations are hydraulically conductive,or not.The stress inversion results are consistent with independent stress measurements in each of the four case studies.
