To investigate the porosity, permeability and rock mechanics of deep shale under temperature-pressure coupling, we selected the core samples of deep shale from the Lower Silurian Longmaxi Formation in the Weirong and ...To investigate the porosity, permeability and rock mechanics of deep shale under temperature-pressure coupling, we selected the core samples of deep shale from the Lower Silurian Longmaxi Formation in the Weirong and Yongchuan areas of the Sichuan Basin for porosity and permeability experiments and a triaxial compression and sound wave integration experiment at the maximum temperature and pressure of 120 ℃ and 70 MPa. The results show that the microscopic porosity and permeability change and the macroscopic rock deformation are mutually constrained, both showing the trend of steep and then gentle variation. At the maximum temperature and pressure, the porosity reduces by 34%–71%, and the permeability decreases by 85%–97%. With the rising temperature and pressure, deep shale undergoes plastic deformation in which organic pores and clay mineral pores are compressed and microfractures are closed, and elastic deformation in which brittle mineral pores and rock skeleton particles are compacted. Compared with previous experiments under high confining pressure and normal temperature,the experiment under high temperature and high pressure coupling reveals the effect of high temperature on stress sensitivity of porosity and permeability. High temperature can increase the plasticity of the rock, intensify the compression of pores due to high confining pressure, and induce thermal stress between the rock skeleton particles, allowing the reopening of shale bedding or the creation of new fractures along weak planes such as bedding, which inhibits the decrease of permeability with the increase of temperature and confining pressure. Compared with the triaxial mechanical experiment at normal temperature, the triaxial compression experiment at high temperature and high pressure demonstrates that the compressive strength and peak strain of deep shale increase significantly due to the coupling of temperature and pressure. The compressive strength is up to 435 MPa and the peak strain exceeds 2%, indicating that high temperature is not conducive to fracture initiation and expansion by increasing rock plasticity. Lithofacies and mineral composition have great impacts on the porosity, permeability and rock mechanics of deep shale. Shales with different lithologies are different in the difficulty and extent of brittle failure. The stress-strain characteristics of rocks under actual geological conditions are key support to the optimization of reservoir stimulation program.展开更多
Variations of sedimentation rate within a basin over geologic time are a time series that can be filtered into several cyclic wave curves. Based on back-stripping and the empirical mode decomposition method, the cores...Variations of sedimentation rate within a basin over geologic time are a time series that can be filtered into several cyclic wave curves. Based on back-stripping and the empirical mode decomposition method, the cores from 14 wells in the Tarim Basin were selected to do filtering analysis. Four cycles or quasi-cycles （33 Ma, 64.4 Ma, 103.6 Ma, and 224 Ma） were obtained. Among these, the 33 Ma period, which was related to the internal earth activity, an external force, or a combination of the two, was the most obvious. The 64.4 Ma period corresponded to the solar system crossing the galaxy plane or the periodic melting of inner-earth material. The 103.6 Ma period was related with plate collisional tectonism around the Tarim Plate. The 224 Ma period was related to one galaxy year and may also be related to the aesthenospherical convection cycle.展开更多
基金Supported by the National Natural Science Foundation of China(41872124,42130803)Sinopec Key Science and Technology Project(P20046).
文摘To investigate the porosity, permeability and rock mechanics of deep shale under temperature-pressure coupling, we selected the core samples of deep shale from the Lower Silurian Longmaxi Formation in the Weirong and Yongchuan areas of the Sichuan Basin for porosity and permeability experiments and a triaxial compression and sound wave integration experiment at the maximum temperature and pressure of 120 ℃ and 70 MPa. The results show that the microscopic porosity and permeability change and the macroscopic rock deformation are mutually constrained, both showing the trend of steep and then gentle variation. At the maximum temperature and pressure, the porosity reduces by 34%–71%, and the permeability decreases by 85%–97%. With the rising temperature and pressure, deep shale undergoes plastic deformation in which organic pores and clay mineral pores are compressed and microfractures are closed, and elastic deformation in which brittle mineral pores and rock skeleton particles are compacted. Compared with previous experiments under high confining pressure and normal temperature,the experiment under high temperature and high pressure coupling reveals the effect of high temperature on stress sensitivity of porosity and permeability. High temperature can increase the plasticity of the rock, intensify the compression of pores due to high confining pressure, and induce thermal stress between the rock skeleton particles, allowing the reopening of shale bedding or the creation of new fractures along weak planes such as bedding, which inhibits the decrease of permeability with the increase of temperature and confining pressure. Compared with the triaxial mechanical experiment at normal temperature, the triaxial compression experiment at high temperature and high pressure demonstrates that the compressive strength and peak strain of deep shale increase significantly due to the coupling of temperature and pressure. The compressive strength is up to 435 MPa and the peak strain exceeds 2%, indicating that high temperature is not conducive to fracture initiation and expansion by increasing rock plasticity. Lithofacies and mineral composition have great impacts on the porosity, permeability and rock mechanics of deep shale. Shales with different lithologies are different in the difficulty and extent of brittle failure. The stress-strain characteristics of rocks under actual geological conditions are key support to the optimization of reservoir stimulation program.
基金financially supported by the National Natural Science Foundation of China (Grant No.41172124)the Petroleum Exploration and Production Research Institute,Sinopec Company Ltd
文摘Variations of sedimentation rate within a basin over geologic time are a time series that can be filtered into several cyclic wave curves. Based on back-stripping and the empirical mode decomposition method, the cores from 14 wells in the Tarim Basin were selected to do filtering analysis. Four cycles or quasi-cycles （33 Ma, 64.4 Ma, 103.6 Ma, and 224 Ma） were obtained. Among these, the 33 Ma period, which was related to the internal earth activity, an external force, or a combination of the two, was the most obvious. The 64.4 Ma period corresponded to the solar system crossing the galaxy plane or the periodic melting of inner-earth material. The 103.6 Ma period was related with plate collisional tectonism around the Tarim Plate. The 224 Ma period was related to one galaxy year and may also be related to the aesthenospherical convection cycle.
