Study on deformation characteristics of fractures in different directions with constant volume boundary conditions

Abstract

With different boundary conditions, the stress sensitivity change law of the reservoir is significantly different. This thesis qualitatively researches and describes the relationship among parameters such as fracture aperture, fracture permeability, boundary stress and pore fluid pressure based on physical simulation experiments. In order to apply it to actual oil reservoirs, a fracture dynamic deformation calculation model was established to quantitatively analyze the fracture directional pressure sensitivity effect in actual oil reservoirs. Finally, the physical simulation experiment test results are compared with the theoretical model calculation results, the two results are consistent, indicating the research results are reliable. The pressure-sensitive analytical model proposed by the research is used to analyze the pressure-sensitive characteristics of fractures at different angles, the characteristics of permeability tensor and their influence on the seepage law. The experimental results show: under the same pressure condition of the constant volume boundary, the flow rate of the fracture model decreases with the increase of the fracture angle, and the fracture aperture change rate first increases and then decreases with increase of the fracture angle, the 45° fracture system is the largest; the larger the fracture distance is, the smaller the total aperture in per unit area and corresponding fracture permeability; fracture aperture and permeability decrease with increase of elastic modulus of matrix system; the effective stress coefficient larger, the aperture and permeability of fracture smaller after deformation.