Numerical simulation on hydraulic fracture propagation in glutenite reservoir based on microscopic damage multiphase coupling

The numerical simulation on hydraulic fracture propagation in low permeability glutenite oil reservoir is of great significance to the successful fracturing stimulation of this reservoir. By characterizing the gravel in the glutenite reservoir as a matrixinterface-gravel three modal textures, and assuming that the gravel distribution, geometry and reservoir property meet the random distribution, the mathematical characterization of glutenite reservoir was completed with the Moter-Carolo method. Taking into account the tri-phase coupling of reservoir seepage field, stress field and hydration propagation moisture field, and according to the principles of damage mechanics and fracture mechanics, the microscopic damage finite element method was used to establish a mathematical model of hydraulic fracture propagation in glutenite reservoir. This mathematical model was used to simulate and analyze the hydraulic fracture propagation when the fractures encounter gravels under different principal stress differences, matrix-gravel interface strengths and gravel strengths. Finally, numerical simulation of dynamic propagation of hydraulic fractures in glutenite reservoir was completed. The study results show that some phenomena such as bypassing, passing through and arresting occur when hydraulic fracture encounters gravels.Especially, propagation through bypassing gravel predominates. The fracture apparently diverts, and pinnate secondary fractures occur.The fracture diverting level and penetration are related to the principal stress difference, gravel strength and interface strength. Essentially,the smaller the horizontal principal stress, the more apparent the diversion of hydraulic fracture when it encounters gravels. As the matrix-gravel interface strength increases, the hydraulic fracture apparently shortens and is difficult to divert. As the gravel strength increases, the diverting level of fractures increases.