Experimental study on hydraulic shear and seepage of granite under three-dimensional stress
To reveal the influence mechanism of hydraulic shear on the permeability characteristics of hot dry rock under three-dimensional stress.The self-made high temperature true triaxial hydraulic shear test device and permeability test system were used.The granite in Daqing area of Songliao Basin is taken as the research object.Prefabricated fractured granite is treated at high temperature.The geological characteristics of different thermal reservoirs are simulated by changing the three-dimensional stress,water injection pressure,flow rate and time.The roughness coefficient of fracture surface is used to describe the variation characteristics of fracture before and after hydraulic shear.The influence of water injection parameters on fracture permeability after hydraulic shear of granite under different three-dimensional stresses was tested.The results show that:(1)the mass loss rate and porosity of granite increase with the increase of temperature,and the tensile-compressive strength decreases with the increase of temperature.(2)The fracture permeability decreases with the increase of volume stress under different pore pressure and temperature.The fracture permeability increases from 10-17 m2 to 10-16 m2 at 150 ℃-350 ℃.(3)The relationship between the maximum water injection pressure and the volumetric stress obeys the quadratic polynomial distribution.The maximum water injection pressure is 4.78 MPa when the volumetric stress is 18.5 MPa.(4)After hydraulic shearing,the fracture permeability of granite increases with the increase of water injection flow rate,and increases first and then stabilizes or decreases with the increase of water injection time.(5)The roughness coefficient of fracture surface decreases after hydraulic shear with different volume stress,water injection flow rate and time,which indicates that the seepage capacity of granite fracture surface is improved after hydraulic shear.
rock mechanicshydraulic shearthree-dimensional stresspermeability
万方数据
维普
