An Enhanced Discrete Fracture Network model to simulate complex fracture distribution

摘要

This paper presents an approach called, Enhanced Discrete Fracture Network (EDFN) for fractured reservoirs modeling. The purpose of this approach is to efficiently represent complex fracture network and accurately simulate the fluid exchange between matrix and fracture. In this approach, fracture network is discretized with a minimum number of grids depending on the fracture intersecting points and fracture extremities. Besides, fracture network naturally decomposes matrix into coarse-scale block with variable geometries, and the partition is optimized by a rapid image processing algorithm. Each coarse matrix block is locally associated with a fracture grid, and it is equivalently discretized to rectangular fine-scale grid blocks. Fine-scale grid blocks are communicated with local fracture grids through one-dimensional flow transport. Therefore, the EDFN model maximally optimizes the discretization process for fractured reservoirs, and it is very appropriate for the simulation of reservoirs with arbitrarily oriented interconnected fractures. Through benchmark with different grid discretization approaches, the EDFN model provides very consistent results and its accuracy is validated. Besides, we also demonstrate that the EDFN model is able to simulate fractured reservoirs with a much smaller number of grid blocks than other approaches. Finally different non-Darcy flow mechanisms in shale gas reservoirs are incorporated into the EDFN model and the impact of those flow mechanisms are investigated.