Hydraulic fracturing of low-permeability continental reservoirs that possess argillaceous interlayers between single sand bodies is poorly understood.In this study,the delta-front-facies,low-permeability sandemudstone...Hydraulic fracturing of low-permeability continental reservoirs that possess argillaceous interlayers between single sand bodies is poorly understood.In this study,the delta-front-facies,low-permeability sandemudstone interbedded reservoir of the Ansai district,Ordos Basin,is used as a case study.The reservoir characteristics of different sedimentary microfacies were identified using information from outcrops,drill cores and well logging.Six reservoir physical models of sandemudstone assemblages were established on the basis of these data.The fracture growth patterns and parameters of the six models were obtained by numerical simulation.Numerical simulation with different fracturing parameters was conducted,to obtain the best parameters for each model to achieve different fracturing effects.The results show that crack size is influenced by the thickness of sandstone and mudstone units,the sandstone to mudstone ratio,and fracturing operation parameters.Sandstone thickness is extremely important in crack propagation.For medium and thick sandstone(3e5 m thick)interbedded with thin mudstone(<0.3 m thick),fracture width and length are large,and longitudinal fractures can pierce mudstone layers.In contrast,for thin sandstone(<1.5 m thick)interbedded with thick mudstone(>0.8 m thick),fractures are small and often restricted to a single sand body,and the mudstone interlayers limit the longitudinal extent of cracks.The six models represent three sedimentary microfacies with different distributions of sandstone and mudstone.Oil well artificial fracture shapes and parameters in different microfacies were visualized through simulation with different models,and match well with data from actual fields We also conducted fracture simulation by changing the fracturing construction parameters to obtain the optimal parameters for different fracturing effects in the models,providing a new understanding of the mudstone interlayers between single sand bodies(>0.3 m thick)and an important basis for oil field construction.展开更多
To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring art...To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.展开更多
文摘Hydraulic fracturing of low-permeability continental reservoirs that possess argillaceous interlayers between single sand bodies is poorly understood.In this study,the delta-front-facies,low-permeability sandemudstone interbedded reservoir of the Ansai district,Ordos Basin,is used as a case study.The reservoir characteristics of different sedimentary microfacies were identified using information from outcrops,drill cores and well logging.Six reservoir physical models of sandemudstone assemblages were established on the basis of these data.The fracture growth patterns and parameters of the six models were obtained by numerical simulation.Numerical simulation with different fracturing parameters was conducted,to obtain the best parameters for each model to achieve different fracturing effects.The results show that crack size is influenced by the thickness of sandstone and mudstone units,the sandstone to mudstone ratio,and fracturing operation parameters.Sandstone thickness is extremely important in crack propagation.For medium and thick sandstone(3e5 m thick)interbedded with thin mudstone(<0.3 m thick),fracture width and length are large,and longitudinal fractures can pierce mudstone layers.In contrast,for thin sandstone(<1.5 m thick)interbedded with thick mudstone(>0.8 m thick),fractures are small and often restricted to a single sand body,and the mudstone interlayers limit the longitudinal extent of cracks.The six models represent three sedimentary microfacies with different distributions of sandstone and mudstone.Oil well artificial fracture shapes and parameters in different microfacies were visualized through simulation with different models,and match well with data from actual fields We also conducted fracture simulation by changing the fracturing construction parameters to obtain the optimal parameters for different fracturing effects in the models,providing a new understanding of the mudstone interlayers between single sand bodies(>0.3 m thick)and an important basis for oil field construction.
基金Projects(20120094110005,20120094130003)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProjects(51379068,51139001,51279052,51209077,51179066)supported by the National Natural Science Foundation of China+1 种基金Project(NCET-11-0628)supported by the Program for New Century Excellent Talents in University,ChinaProjects(201201038,201101013)supported by the Public Welfare Industry Research Special Fund Project of Ministry of Water Resources of China
文摘To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.
