Study On Flow Simulation Of Discrete Fracture Network Model Based On Control Volume Method

Numerical simulation technology of fractured reservoir has been always the difficulty and hotspot in reservoir numerical simulation. Discrete fracture model greatly improve the computational efficiency, because the dimensionality of fractures is reduced from n to (n-1), and it has good development prospect. At present, in order to adapt to complex geometry geological model, the flow numerical simulation of discrete fracture model mostly employed finite element method. However, because of the large computational complexity, it can't be large-scale applied. Meanwhile, the calculation scheme of finite element method can't ensure local mass conservation. The numerical calculation method based on the control volume method can strictly ensure local mass and momentum conservation in every control volume cell, and it has a clear physical interpretation. Meanwhile, the control volume method based on unstructured grid also applys to complex geometry geological model. For the reason, establish the numerical calculation scheme of discrete fracture model based on the control volume method in the paper, and realize the flow simulation of weakly compressible oil-water two phases. First use Monte-Carlo method to generate equivalent discrete fracture network in a statistical sense, and carry out geometrical discretization accordance with the simplified physical model. Next establish discrete fracture model on the basis of the equivalent velocity of single fracture, and integrate seepage equation in every control volume cell based on control volume method, final establish the control volume numerical calculation scheme of the slightly compressible oil-water two phase flow. Then slove the two phase mathematical model with the IMPES method, and apply the iterative method to slove linear algebraic equations. At last verify the correctness and high computational efficiency of discrete fracture model based on control volume method flow simulation theory through examples. The results show that numerical calculation results of discrete fracture model based on control volume method shows a good agreement with single porosity media model, but the discrete fracture network has higher computational efficiency than single porosity media model. Through the research of flow simulation of water injection in discrete fractured media, we can see that the distribution of fractures has great influence on waterflooding effect and flood pattern arrangement. Water injection should displacement of oil at the sides of fracture and not along fracture, this can effectively expand the sweep area, thus improve the water flooding recovery.