The effective channeling of fluid flow by fractures is a liability for enhanced oil recovery(EOR)methods like CO_(2) flooding or CO_(2) storage.Developing a distributed fracture model to understand the heterogeneity o...The effective channeling of fluid flow by fractures is a liability for enhanced oil recovery(EOR)methods like CO_(2) flooding or CO_(2) storage.Developing a distributed fracture model to understand the heterogeneity of the fracture network is essential in characterizing tight and low-permeability reservoirs.In the Ordos Basin,the Chang 8-1-2 layer of the Yanchang Formation is a typical tight and low permeability reservoir in the JH17 wellblock.The strong heterogeneity of distributed fractures,differing fracture scales and fracture types make it difficult to effectively characterize the fracture distribution within the Chang 8-1-2 layer.In this paper,multi-source and multi-attribute methods are used to integrate data into a neural network at different scales,and fuzzy logic control is used to judge the correlation of various attributes.The results suggest that attribute correlation between coherence and fracture indication is the best,followed by correlations with fault distance,north–south slope,and north–south curvature.Advantageous attributes from the target area are used to train the neural network,and the fracture density model and discrete fracture network(DFN)model are built at different scales.This method can be used to effectively predict the distribution characteristics of fractures in the study area.And any learning done by the neural network from this case study can be applied to fracture network modeling for reservoirs of the same type.展开更多
The fracture behavior at high temperatures of the Ti−22Al−26Nb alloy,which features duplex lamellar,bimodal,and Widmanstätten structures,was studied.Samples of the alloy were prepared through compression deformat...The fracture behavior at high temperatures of the Ti−22Al−26Nb alloy,which features duplex lamellar,bimodal,and Widmanstätten structures,was studied.Samples of the alloy were prepared through compression deformation in the trans-phase region followed by subsequent heat treatment.The results indicate that at 650℃,the fracture toughness of the Ti−22Al−26Nb alloy is increased by 41.7%compared to that with original microstructures.The content of the B2 phase significantly influences the inherent fracture toughness of the material,while the morphology and distribution of the precipitated phases primarily affect the tortuosity of the crack propagation path.Among the microstructural features,the morphology and geometric orientation of the lamellae most significantly impact the crack path;consequently,the Widmanstätten structure exhibits the most tortuous fracture path.Additionally,a predictive model for fracture toughness is developed,which effectively predicts the fracture toughness of Ti−22Al−26Nb alloys with various microstructures at 650℃.展开更多
Deep shale reservoirs are often associated with extreme geological conditions,including high tem-peratures,substantial horizontal stress differences,elevated closure stresses,and high breakdown pressures.These factors...Deep shale reservoirs are often associated with extreme geological conditions,including high tem-peratures,substantial horizontal stress differences,elevated closure stresses,and high breakdown pressures.These factors pose significant challenges to conventional hydraulic fracturing with water-based fluids,which may induce formation damage and fail to generate complex fracture networks.Supercritical carbon dioxide(SC-CO_(2)),with its low viscosity,high diffusivity,low surface tension,and minimal water sensitivity,has attracted growing attention as an alternative fracturing fluid for deep shale stimulation.This study presents a series of true triaxial large-scale physical experiments using shale samples from the Longmaxi Formation in the southern Sichuan Basin to investigate fracture initiation and propagation behavior under different fracturing fluids.The results show that,under identical experimental conditions,SC-CO_(2)fracturing results in a significantly lower breakdown pressure compared to slick water and promotes the formation of more complex fracture geometries.These advantages are attributed to both the favorable flow characteristics of SC-CO_(2)and its potential chemical interactions with shale minerals.The findings not only confirm the effectiveness of SC-CO_(2)as a fracturing fluid in deep shale environments but also provide new insights into its fracture propagation mechanisms.展开更多
We study the localized coherent structures ofa generally nonintegrable (2+ 1 )-dimensional KdV equation via a variable separation approach. In a special integrable case, the entrance of some arbitrary functions leads ...We study the localized coherent structures ofa generally nonintegrable (2+ 1 )-dimensional KdV equation via a variable separation approach. In a special integrable case, the entrance of some arbitrary functions leads to abundant coherent structures. However, in the general nonintegrable case, an additional condition has to be introduced for these arbitrary functions. Although the additional condition has been introduced into the solutions of the nonintegrable KdV equation, there still exist many interesting solitary wave structures. Especially, the nonintegrable KdV equation possesses the breather-like localized excitations, and the similar static ring soliton solutions as in the integrable case. Furthermor,in the integrable case, the interaction between two travelling ring solitons is elastic, while in the nonintegrable case we cannot find even the single travelling ring soliton solution.展开更多
Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and ...Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.展开更多
Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This a...Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This approach significantly increases the recovery efficiency of low-permeability oil and gas fields.Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs.However,few studies are reported on large-scale physical model experiments in terms of a method for calculating the fracture number.This study analyzed the initiation and propagation of cracks under LCPTB,derived a calculation formula for crack propagation radius under stress waves,and then proposed a new,fast,and accurate method for calculating the fracture number using the principle of mass conservation.Through ten rock-breaking tests using LCPTB,the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure,rock-breaking scenario,and the impact of varying parameters on fracture number.The results show that the new calculation method is suitable for fracturing technologies with high pressure rates.Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO_(2) mass in the tube to enhance fracture effectiveness.Moreover,the method can be applied to other fracturing technologies,such as explosive fracturing(EF)within HF formations,indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.展开更多
As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff perfor...As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff performance is not well understood.In this study,we present a fully coupled multi-component flow and geomechanics model for simulating CO_(2)huff-n-puff in shale gas reservoirs considering hydraulic fracture deformation hysteresis.Specifically,a shale gas reservoir after hydraulic fracturing is modeled using an efficient hybrid model incorporating an embedded discrete fracture model(EDFM),multiple porosity model,and single porosity model.In flow equations,Fick’s law,extended Langmuir isotherms,and the Peng-Robinson equation of state are used to describe the molecular diffusion,multi-component adsorption,and gas properties,respectively.In relation to geomechanics,a path-dependent constitutive law is applied for the hydraulic fracture deformation hysteresis.The finite volume method(FVM)and the stabilized extended finite element method(XFEM)are applied to discretize the flow and geomechanics equations,respectively.We then solve the coupled model using the fixed-stress split iterative method.Finally,we verify the presented method using several numerical examples,and apply it to investigate the effect of hydraulic fracture deformation hysteresis on CO_(2)huff-n-puff performance in a 3D shale gas reservoir.Numerical results show that hydraulic fracture deformation hysteresis has some negative effects on CO_(2)huff-n-puff performance.The effects are sensitive to the initial conductivity of hydraulic fracture,production pressure,starting time of huff-n-puff,injection pressure,and huff-n-puff cycle number.展开更多
The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exp...The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exponent 5 is estimated using the power law relations and the finite size scaling functions for the magnetization and the susceptibility in the range -0.1≤ h = H/J ≤0. The estimated value of the field critical exponent 5 is in good agreement with the universal value （δ = 5） in three dimensions. The simulations are carried out on a simple cubic lattice under periodic boundary conditions.展开更多
The utilization of hydraulic fracturing for the extraction of natural gas hydrates in maritime environments has been relatively underexplored in the existing literature.This study introduces a novel approach by employ...The utilization of hydraulic fracturing for the extraction of natural gas hydrates in maritime environments has been relatively underexplored in the existing literature.This study introduces a novel approach by employing a fully implicit integration method to construct a two-dimensional temperature distribution model of the wellbore.The model considers critical parameters such as fracturing fluid time,initial temperature,and fracturing fluid displacement to forecast the temperature data of the wellbore and its surrounding environments throughout the entire fracturing process.The investigation reveals that the initial temperature of the fracturing liquid and the duration of the fracturing process exert a substantial influence on the wellbore temperature,whereas the impact of fracturing fluid displacement is found to be minimal.Furthermore,a comparative analysis between the results derived from the proposed model and those obtained from traditional steady-state formulas substantiates the accuracy and efficacy of the developed model.This study significantly advances our comprehension of temperature dynamics within wellbores during hydraulic fracturing operations in maritime environments,thereby offering valuable insights for future endeavors in natural gas hydrate extraction.展开更多
This paper attempts to study dolomite failure using small-scale blast tests.The experimental setup consisted of a cylindrical specimen with a central borehole fitted with a detonation cord inside a copper pipe.The spe...This paper attempts to study dolomite failure using small-scale blast tests.The experimental setup consisted of a cylindrical specimen with a central borehole fitted with a detonation cord inside a copper pipe.The specimen was confined using lead material.During the test,acceleration histories were recorded using sensors placed on the lead confinement.The results showed that heterogeneity and initial cracks significantly influenced the observed failure and cracking patterns.The tests were numerically represented using the previously validated Johnson-HolmquistⅡ(JH-2)constitutive model.The properties of the detonation cord were first determined and verified in a special test with a lead specimen to compare the deformation in the test with that of numerical simulation.Then,the small-scale blast test was simulated,and the failure of the dolomite was compared with the test observations.Comparisons of acceleration histories,scabbing failure,and number of radial cracks and crack density confirmed the overall repeatability of the actual testing data.It is likely that the proposed model can be further used for numerical studies of blasting of dolomite rock.展开更多
This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground d...This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground deformation,fault reactivation,induced seismicity and crack propagation,is presented.It is indicated that although all the processes involved are not fully understood,integration of all available data,such as ground survey,geological conditions,microseismicity and ground level deformation,has led to many new insights into the rock mechanical response to CO2injection.The review also shows that in geomechanical modeling,continuum modeling methods are predominant compared with discontinuum methods.It is recommended to develop continuum-discontinuum numerical methods since they are more convenient for geomechanical modeling of CO2geological storage,especially for fracture propagation simulation.The Mohr-Coulomb criterion is widely used in prediction of rock mass mechanical behavior.It would be better to use a criterion considering the effect of the intermediate principal stress on rock mechanical behavior,especially for the stability analysis of deeply seated rock engineering.Some challenges related to geomechanical modeling of CO2geological storage are also discussed.展开更多
A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put...A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put forward. The principle, geo-metric schematic and limit state equation of this model are presented. Reliability evaluation for a kind of diesel engine crankshaft was made based on this theory, in which multi-axial loading fatigue criteria was employed. Because more important factors, i.e. stress asymmetric ratio and its variability, are considered, it theoretically can make more accurate evaluation for structural com-ponent reliability than the traditional interference model. Correspondingly, a Monte-Carlo Method simulation solution is also given. The computation suggests that this model can yield satisfactory reliability evaluation.展开更多
基金supported by the National Science and Technology Project of China(No.2024ZD1004300)。
文摘The effective channeling of fluid flow by fractures is a liability for enhanced oil recovery(EOR)methods like CO_(2) flooding or CO_(2) storage.Developing a distributed fracture model to understand the heterogeneity of the fracture network is essential in characterizing tight and low-permeability reservoirs.In the Ordos Basin,the Chang 8-1-2 layer of the Yanchang Formation is a typical tight and low permeability reservoir in the JH17 wellblock.The strong heterogeneity of distributed fractures,differing fracture scales and fracture types make it difficult to effectively characterize the fracture distribution within the Chang 8-1-2 layer.In this paper,multi-source and multi-attribute methods are used to integrate data into a neural network at different scales,and fuzzy logic control is used to judge the correlation of various attributes.The results suggest that attribute correlation between coherence and fracture indication is the best,followed by correlations with fault distance,north–south slope,and north–south curvature.Advantageous attributes from the target area are used to train the neural network,and the fracture density model and discrete fracture network(DFN)model are built at different scales.This method can be used to effectively predict the distribution characteristics of fractures in the study area.And any learning done by the neural network from this case study can be applied to fracture network modeling for reservoirs of the same type.
基金financially supported by the National Natural Science Foundation of China(Nos.51975175,51875158)。
文摘The fracture behavior at high temperatures of the Ti−22Al−26Nb alloy,which features duplex lamellar,bimodal,and Widmanstätten structures,was studied.Samples of the alloy were prepared through compression deformation in the trans-phase region followed by subsequent heat treatment.The results indicate that at 650℃,the fracture toughness of the Ti−22Al−26Nb alloy is increased by 41.7%compared to that with original microstructures.The content of the B2 phase significantly influences the inherent fracture toughness of the material,while the morphology and distribution of the precipitated phases primarily affect the tortuosity of the crack propagation path.Among the microstructural features,the morphology and geometric orientation of the lamellae most significantly impact the crack path;consequently,the Widmanstätten structure exhibits the most tortuous fracture path.Additionally,a predictive model for fracture toughness is developed,which effectively predicts the fracture toughness of Ti−22Al−26Nb alloys with various microstructures at 650℃.
文摘Deep shale reservoirs are often associated with extreme geological conditions,including high tem-peratures,substantial horizontal stress differences,elevated closure stresses,and high breakdown pressures.These factors pose significant challenges to conventional hydraulic fracturing with water-based fluids,which may induce formation damage and fail to generate complex fracture networks.Supercritical carbon dioxide(SC-CO_(2)),with its low viscosity,high diffusivity,low surface tension,and minimal water sensitivity,has attracted growing attention as an alternative fracturing fluid for deep shale stimulation.This study presents a series of true triaxial large-scale physical experiments using shale samples from the Longmaxi Formation in the southern Sichuan Basin to investigate fracture initiation and propagation behavior under different fracturing fluids.The results show that,under identical experimental conditions,SC-CO_(2)fracturing results in a significantly lower breakdown pressure compared to slick water and promotes the formation of more complex fracture geometries.These advantages are attributed to both the favorable flow characteristics of SC-CO_(2)and its potential chemical interactions with shale minerals.The findings not only confirm the effectiveness of SC-CO_(2)as a fracturing fluid in deep shale environments but also provide new insights into its fracture propagation mechanisms.
文摘We study the localized coherent structures ofa generally nonintegrable (2+ 1 )-dimensional KdV equation via a variable separation approach. In a special integrable case, the entrance of some arbitrary functions leads to abundant coherent structures. However, in the general nonintegrable case, an additional condition has to be introduced for these arbitrary functions. Although the additional condition has been introduced into the solutions of the nonintegrable KdV equation, there still exist many interesting solitary wave structures. Especially, the nonintegrable KdV equation possesses the breather-like localized excitations, and the similar static ring soliton solutions as in the integrable case. Furthermor,in the integrable case, the interaction between two travelling ring solitons is elastic, while in the nonintegrable case we cannot find even the single travelling ring soliton solution.
基金supported by the National Natural Science Foundation of China(No.52174038 and No.52004307)China Petroleum Science and Technology Project-Major Project-Research on Tight Oil-Shale Oil Reservoir Engineering Methods and Key Technologies in Ordos Basin(No.ZLZX2020-02-04)Science Foundation of China University of Petroleum,Beijing(No.2462018YJRC015)。
文摘Under the policy background and advocacy of carbon capture,utilization,and storage(CCUS),CO_(2)-EOR has become a promising direction in the shale oil reservoir industry.The multi-scale pore structure distribution and fracture structure lead to complex multiphase flow,comprehensively considering multiple mechanisms is crucial for development and CO_(2) storage in fractured shale reservoirs.In this paper,a multi-mechanism coupled model is developed by MATLAB.Compared to the traditional Eclipse300 and MATLAB Reservoir Simulation Toolbox(MRST),this model considers the impact of pore structure on fluid phase behavior by the modified Peng—Robinson equation of state(PR-EOS),and the effect simultaneously radiate to Maxwell—Stefan(M—S)diffusion,stress sensitivity,the nano-confinement(NC)effect.Moreover,a modified embedded discrete fracture model(EDFM)is used to model the complex fractures,which optimizes connection types and half-transmissibility calculation approaches between non-neighboring connections(NNCs).The full implicit equation adopts the finite volume method(FVM)and Newton—Raphson iteration for discretization and solution.The model verification with the Eclipse300 and MRST is satisfactory.The results show that the interaction between the mechanisms significantly affects the production performance and storage characteristics.The effect of molecular diffusion may be overestimated in oil-dominated(liquid-dominated)shale reservoirs.The well spacing and injection gas rate are the most crucial factors affecting the production by sensitivity analysis.Moreover,the potential gas invasion risk is mentioned.This model provides a reliable theoretical basis for CO_(2)-EOR and sequestration in shale oil reservoirs.
基金supported by the National Key R&D Program of China (Grant No.2020YFA0711802).
文摘Integrating liquid CO_(2)phase transition blasting(LCPTB)technology with hydraulic fracturing(HF)methods can help reduce wellbore damage,create multiple radial fractures,and establish a complex fracture network.This approach significantly increases the recovery efficiency of low-permeability oil and gas fields.Accurately calculating the number of fractures caused by LCPTB is necessary to predict production enhancement effects and optimize subsequent HF designs.However,few studies are reported on large-scale physical model experiments in terms of a method for calculating the fracture number.This study analyzed the initiation and propagation of cracks under LCPTB,derived a calculation formula for crack propagation radius under stress waves,and then proposed a new,fast,and accurate method for calculating the fracture number using the principle of mass conservation.Through ten rock-breaking tests using LCPTB,the study confirmed the effectiveness of the proposed calculation approach and elucidated the variation rule of explosion pressure,rock-breaking scenario,and the impact of varying parameters on fracture number.The results show that the new calculation method is suitable for fracturing technologies with high pressure rates.Recommendations include enlarging the diameter of the fracturing tube and increasing the liquid CO_(2) mass in the tube to enhance fracture effectiveness.Moreover,the method can be applied to other fracturing technologies,such as explosive fracturing(EF)within HF formations,indicating its broader applicability and potential impact on optimizing unconventional resource extraction technologies.
基金This work is supported by the National Natural Sci‐ence Foundation of China(Nos.52004321,52034010,and 12131014)the Natural Science Foundation of Shandong Province,China(No.ZR2020QE116)the Fundamental Research Funds for the Central Universities,China(Nos.20CX06025A and 21CX06031A).
文摘As a promising enhanced gas recovery technique,CO_(2)huff-n-puff has attracted great attention recently.However,hydraulic fracture deformation hysteresis is rarely considered,and its effect on CO_(2)huff-n-puff performance is not well understood.In this study,we present a fully coupled multi-component flow and geomechanics model for simulating CO_(2)huff-n-puff in shale gas reservoirs considering hydraulic fracture deformation hysteresis.Specifically,a shale gas reservoir after hydraulic fracturing is modeled using an efficient hybrid model incorporating an embedded discrete fracture model(EDFM),multiple porosity model,and single porosity model.In flow equations,Fick’s law,extended Langmuir isotherms,and the Peng-Robinson equation of state are used to describe the molecular diffusion,multi-component adsorption,and gas properties,respectively.In relation to geomechanics,a path-dependent constitutive law is applied for the hydraulic fracture deformation hysteresis.The finite volume method(FVM)and the stabilized extended finite element method(XFEM)are applied to discretize the flow and geomechanics equations,respectively.We then solve the coupled model using the fixed-stress split iterative method.Finally,we verify the presented method using several numerical examples,and apply it to investigate the effect of hydraulic fracture deformation hysteresis on CO_(2)huff-n-puff performance in a 3D shale gas reservoir.Numerical results show that hydraulic fracture deformation hysteresis has some negative effects on CO_(2)huff-n-puff performance.The effects are sensitive to the initial conductivity of hydraulic fracture,production pressure,starting time of huff-n-puff,injection pressure,and huff-n-puff cycle number.
文摘The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exponent 5 is estimated using the power law relations and the finite size scaling functions for the magnetization and the susceptibility in the range -0.1≤ h = H/J ≤0. The estimated value of the field critical exponent 5 is in good agreement with the universal value （δ = 5） in three dimensions. The simulations are carried out on a simple cubic lattice under periodic boundary conditions.
基金supported by National Natural Science Foundation of China(52074248)Fundamental Research Funds for the Central Universities(2652022207).
文摘The utilization of hydraulic fracturing for the extraction of natural gas hydrates in maritime environments has been relatively underexplored in the existing literature.This study introduces a novel approach by employing a fully implicit integration method to construct a two-dimensional temperature distribution model of the wellbore.The model considers critical parameters such as fracturing fluid time,initial temperature,and fracturing fluid displacement to forecast the temperature data of the wellbore and its surrounding environments throughout the entire fracturing process.The investigation reveals that the initial temperature of the fracturing liquid and the duration of the fracturing process exert a substantial influence on the wellbore temperature,whereas the impact of fracturing fluid displacement is found to be minimal.Furthermore,a comparative analysis between the results derived from the proposed model and those obtained from traditional steady-state formulas substantiates the accuracy and efficacy of the developed model.This study significantly advances our comprehension of temperature dynamics within wellbores during hydraulic fracturing operations in maritime environments,thereby offering valuable insights for future endeavors in natural gas hydrate extraction.
基金supported by the Interdisciplinary Center for Mathematical and Computational Modeling(ICM),University of Warsaw(Grant No.GA73-19)as part of the implementation of the Military University of Technology(Grant No.22-876)。
文摘This paper attempts to study dolomite failure using small-scale blast tests.The experimental setup consisted of a cylindrical specimen with a central borehole fitted with a detonation cord inside a copper pipe.The specimen was confined using lead material.During the test,acceleration histories were recorded using sensors placed on the lead confinement.The results showed that heterogeneity and initial cracks significantly influenced the observed failure and cracking patterns.The tests were numerically represented using the previously validated Johnson-HolmquistⅡ(JH-2)constitutive model.The properties of the detonation cord were first determined and verified in a special test with a lead specimen to compare the deformation in the test with that of numerical simulation.Then,the small-scale blast test was simulated,and the failure of the dolomite was compared with the test observations.Comparisons of acceleration histories,scabbing failure,and number of radial cracks and crack density confirmed the overall repeatability of the actual testing data.It is likely that the proposed model can be further used for numerical studies of blasting of dolomite rock.
基金finically supported by the National Natural Science Foundation of China(Grant Nos.41272349 and 51322906)Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDB-SSW-DQC029)
文摘This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground deformation,fault reactivation,induced seismicity and crack propagation,is presented.It is indicated that although all the processes involved are not fully understood,integration of all available data,such as ground survey,geological conditions,microseismicity and ground level deformation,has led to many new insights into the rock mechanical response to CO2injection.The review also shows that in geomechanical modeling,continuum modeling methods are predominant compared with discontinuum methods.It is recommended to develop continuum-discontinuum numerical methods since they are more convenient for geomechanical modeling of CO2geological storage,especially for fracture propagation simulation.The Mohr-Coulomb criterion is widely used in prediction of rock mass mechanical behavior.It would be better to use a criterion considering the effect of the intermediate principal stress on rock mechanical behavior,especially for the stability analysis of deeply seated rock engineering.Some challenges related to geomechanical modeling of CO2geological storage are also discussed.
文摘A 2D stress strength interference model (2D-SSIM) considering that the fatigue reliability of engineering structural components has close relationship to load asymmetric ratio and its variability to some extent is put forward. The principle, geo-metric schematic and limit state equation of this model are presented. Reliability evaluation for a kind of diesel engine crankshaft was made based on this theory, in which multi-axial loading fatigue criteria was employed. Because more important factors, i.e. stress asymmetric ratio and its variability, are considered, it theoretically can make more accurate evaluation for structural com-ponent reliability than the traditional interference model. Correspondingly, a Monte-Carlo Method simulation solution is also given. The computation suggests that this model can yield satisfactory reliability evaluation.
