Mixed-mode fracture behavior in deep shale reservoirs under different loading rates and temperatures  

作　　者：Yu Suo Yan-Jie Zhao Xiao-Fei Fu Wen-Yuan He Zhe-Jun Pan 

机构地区：[1]School of Petroleum Engineering,Northeast Petroleum University,Daqing,163318,Heilongjiang,China [2]Postdoctoral Resource Center,Daqing Oilfield Company Limited,Daqing,163458,Heilongjiang,China [3]Key Laboratory of Continental Shale Hydrocarbon Accumulation and Efficient Development(Northeast Petroleum University),Ministry of Education,Daqing,163318,Heilongjiang,China [4]Heilongjiang Province Key Laboratory of Oil and Gas Reservoir Fracturing and Evaluation,Daqing,163318,Heilongjiang,China [5]PetroChina International Exploration and Development Company Limited Corporation,Beijing,100034,China

出　　处：《Petroleum Science》2023年第5期3037-3047,共11页石油科学（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.52204007);the Natural Science Foundation of Heilongjiang Province of China(YQ2021E005);New Era Longjiang Outstanding Master's and Doctoral Thesis Project(LJYXL2022-002);Key Laboratory of Enhanced Oil and Gas Recovery,Ministry of Education(NEPU-EOR-2022-04).

摘　　要：In the last years,shale gas has gradually substituted oil and coal as the main sources of energy in the world.Compared with shallow shale gas reservoirs,deep shale is characterized by low permeability,low porosity,strong heterogeneity,and strong anisotropy.In the process of multi-cluster fracturing of horizontal wells,the whole deformation process and destruction modes are significantly influenced by loading rates.In this investigation,the servo press was used to carry out semi-circular bend(SCB)mixedmode fracture experiments in deep shales(130,160,190℃)with prefabricated fractures under different loading rates(0.02,0.05,0.1,0.2 mm/min).The fracture propagation process was monitored using acoustic emission.The deformation characteristics,displacementeload curve,and acoustic emission parameters of shale under different loading rates were studied during the mixed-mode fracture propagation.Our results showed that during the deformation and fracture of the specimen,the acoustic emission energy and charge significantly increased near the stress peak,showing at this point the most intense acoustic emission activity.With the increase in loading rate,the fracture peak load of the deep shale specimen also increased.However,the maximum displacement decreased to different extents.With the increase in temperature,the effective fracture toughness of the deep shale gradually decreased.Also,the maximum displacement decreased.Under different loading rates,the deformation of the prefabricated cracks showed a nonlinear slow growthelinear growth trend.The slope of the linear growth stage increased with the increase in loading rate.In addition,as the loading rate increased,an increase in tension failure and a decrease in shear failure were observed.Moreover,the control chart showing the relationship between tension and the shear failure under different temperatures and loading rates was determined.

关 键 词：Deep shale Mixed-mode fracture toughness Loading rate Deformation characteristics 

分 类 号：TE377[石油与天然气工程—油气田开发工程]