Although many studies based on naturally deformed samples have been carried out to investigate the pore-crack characteristics of shales,studies based on high temperature(T)and high pressure(P)deformation experiments,w...Although many studies based on naturally deformed samples have been carried out to investigate the pore-crack characteristics of shales,studies based on high temperature(T)and high pressure(P)deformation experiments,which can exclude sample heterogeneity factors,simulate deep T-P conditions,and generate a continuous deformation sequence,are still rare.In this study,shales with different deformation levels are generated by triaxial compression experiments,and methods including scanning electron microscopy,mercury injection,and gas sorption are utilized to characterize their influence factors and pore-crack characteristics.Results indicate that T is the primary factor influencing shale deformation when P is low,while P is dominant under high P conditions.At T<90℃ and P<60 MPa,shales undergo brittle deformation and their macropores decrease due to the compaction of primary pores,while mesopores increase because of the interconnection of micropores.At 90℃<T<200℃ and 60 MPa<P<110 MPa,shales experience brittle-ductile transitional deformation,and their macro-and micropores increase because of the extension of open cracks and the plastic deformation of clay flakes respectively,while mesopores decrease dramatically.At T>200℃ and P>110 MPa,shales are subjected to ductile deformation,and their micro-and mesopores drop significantly due to the intense compaction in the matrix while macropores continuously increase with crack expansion.The permeability of shale increases with the degree of deformation and ductile material contents are predicted to be a key factor determining whether open microcracks can be preserved after ductile deformation.To account for these experimental results,an ideal model of micro pore-crack system evolution in deformed shales is further proposed,which can provide guidance for the exploration of shale gas resources in the deep or structurally complex zones.展开更多
岩石内孔隙结构和矿物组成是诱导岩体破裂失稳的重要因素。为了研究孔隙结构和矿物组成对裂纹扩展的影响,利用颗粒流程序(particle flow code,简称PFC),构建含不同孔隙结构和矿物组成的岩石晶体模型(grain based model,简称GBM),研究孔...岩石内孔隙结构和矿物组成是诱导岩体破裂失稳的重要因素。为了研究孔隙结构和矿物组成对裂纹扩展的影响,利用颗粒流程序(particle flow code,简称PFC),构建含不同孔隙结构和矿物组成的岩石晶体模型(grain based model,简称GBM),研究孔隙大小对裂纹扩展的影响以及不同矿物内裂纹的扩展规律。研究结果表明:随着孔隙短长轴比的增大,岩石的单轴抗压强度和弹性模量均先减小后增大,岩石的破坏程度先增大后减小,在短长轴比为0.8时,岩石破坏程度最严重。随着孔隙短长轴比的增大,岩石内形成的裂纹数量先减小后增加再减小,张拉裂纹数量先减小后增加再减小,而剪切裂纹数量基本无变化。岩石在破坏过程中以晶内张拉破坏为主,其次为晶间张拉破坏,晶内破坏和晶间破坏中剪切破坏均较少。孔隙短长轴比为0.6时对砂岩基质、黏土、云母内裂纹扩展演化行为影响程度最大,孔隙短长轴比为0.2时对石英和长石内裂纹扩展演化行为影响程度最大。该研究成果可以为解决含孔隙缺陷岩体的失稳破坏问题提供参考和研究基础。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42372153,41530315)the National Key Research and Development Program of China(Grant No.2023YFF0804300)+1 种基金the National Science and Technology Major Project of China(Grant Nos.2016ZX05066,2017ZX05064)the“Climate Change:Carbon Budget and Related Issues”Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05030100)。
文摘Although many studies based on naturally deformed samples have been carried out to investigate the pore-crack characteristics of shales,studies based on high temperature(T)and high pressure(P)deformation experiments,which can exclude sample heterogeneity factors,simulate deep T-P conditions,and generate a continuous deformation sequence,are still rare.In this study,shales with different deformation levels are generated by triaxial compression experiments,and methods including scanning electron microscopy,mercury injection,and gas sorption are utilized to characterize their influence factors and pore-crack characteristics.Results indicate that T is the primary factor influencing shale deformation when P is low,while P is dominant under high P conditions.At T<90℃ and P<60 MPa,shales undergo brittle deformation and their macropores decrease due to the compaction of primary pores,while mesopores increase because of the interconnection of micropores.At 90℃<T<200℃ and 60 MPa<P<110 MPa,shales experience brittle-ductile transitional deformation,and their macro-and micropores increase because of the extension of open cracks and the plastic deformation of clay flakes respectively,while mesopores decrease dramatically.At T>200℃ and P>110 MPa,shales are subjected to ductile deformation,and their micro-and mesopores drop significantly due to the intense compaction in the matrix while macropores continuously increase with crack expansion.The permeability of shale increases with the degree of deformation and ductile material contents are predicted to be a key factor determining whether open microcracks can be preserved after ductile deformation.To account for these experimental results,an ideal model of micro pore-crack system evolution in deformed shales is further proposed,which can provide guidance for the exploration of shale gas resources in the deep or structurally complex zones.
文摘岩石内孔隙结构和矿物组成是诱导岩体破裂失稳的重要因素。为了研究孔隙结构和矿物组成对裂纹扩展的影响,利用颗粒流程序(particle flow code,简称PFC),构建含不同孔隙结构和矿物组成的岩石晶体模型(grain based model,简称GBM),研究孔隙大小对裂纹扩展的影响以及不同矿物内裂纹的扩展规律。研究结果表明:随着孔隙短长轴比的增大,岩石的单轴抗压强度和弹性模量均先减小后增大,岩石的破坏程度先增大后减小,在短长轴比为0.8时,岩石破坏程度最严重。随着孔隙短长轴比的增大,岩石内形成的裂纹数量先减小后增加再减小,张拉裂纹数量先减小后增加再减小,而剪切裂纹数量基本无变化。岩石在破坏过程中以晶内张拉破坏为主,其次为晶间张拉破坏,晶内破坏和晶间破坏中剪切破坏均较少。孔隙短长轴比为0.6时对砂岩基质、黏土、云母内裂纹扩展演化行为影响程度最大,孔隙短长轴比为0.2时对石英和长石内裂纹扩展演化行为影响程度最大。该研究成果可以为解决含孔隙缺陷岩体的失稳破坏问题提供参考和研究基础。
