A Single-Phase Flow Simulation of Fractured Reservoir Using a Discrete Representation of Fractures

Modelling the fracture network within a reservoir is a complex problem. This is conventionally done using a dual porosity, dual permeability model, but this type of model is not well adapted to the fine description of transfers between matrix and fracture. To obtain such a fine description and at the same time get a better understanding of the simplifications involved in the dual porosity model, a single porosity model must be used. Within this framework, we have developed a methodology for the modelling of an unsteady-state single phase flow in a fractured reservoir. It is composed of two main steps. The first step consists in modelling the fractures and matrix as a heterogeneous system and by gridding them both finely using a finite volume scheme (VF4) and a non structured triangular grid. This scheme provides at the same time a good description of the flow at the interface and is well adapted to the geometry of the medium. Results were compared to those obtained using a finely gridded cartesian single porosity model. It is however clearly impossible to use this approach for full-field simulations because of CPU limitations. To overcome this problem, a new "joint element methodology" was developed. This second step combines the VF4 scheme and a linear (2D) or planar (3D) gridding of the fracture. The matrix remains gridded using triangles. The use of this simplified geometrical description of the fractures allows the application to field-scale complex fracture networks.The full method has been validated by comparison with the fine gridded solution.