Abstract: To address the problem that the strong inhomogeneity of large fracture reservoirs makes it difficult to depict the special hydraulic conductivity with conventional continuous media models, a discrete fracture network model was used for numerical simulation, in which large fractures are subjected to a dimensionality reduction to be explicitly characterized in the grid system, unstructured grids were used for the reservoir geometrical sectioning, the fracture was taken as a virtual boundary and discretized into a dimensionality reduction control unit, and the finite-difference numerical computation format of the flow mathematical model was constructed by calculating the conduction coefficients of bedrock-bedrock, bedrock-fracture, and fracture-fracture respectively, and taking into account the dimensional differences of the neighboring control units. The method was applied to numerical simulation of fractured reservoir in Well Group T-6 in a certain western oil field. The results show that the production history fit compliance rate of the well group is more than 80%, the type of residual oil is mainly the shielded residual oil in fracture channel and the unused residual oil between wells, and the proportion of residual oil between wells and below the production interval accounts for more than 60%, which is more in line with the actual understanding. The study results have good applicability to the numerical simulation and residual oil distribution study of reservoirs containing large-scale fractures, and the dimensionality reduction treatment of large fractures can significantly improve the computational efficiency.

Key words: fractured reservoir, large-scale discrete fractures, dimensionality reduction treatment, control unit, numerical simulation