A two-phase flow simulation of a fractured reservoir using a new fissure element method

Modeling of a fissure network is conventionally done using a dual porosity–dual permeability model, but this type of model involves large-scale approximate description of fluid transfers between the matrix and fissure. For understanding of the simplifications involved in the dual porosity approach, a fine description of the fissure network is necessary. To obtain this fine scale description, a new methodology was developed for the modeling of flow in fractured reservoirs. This technique called “the fissure element methodology” is based on application of a specific grid to the fractured medium. This unstructured grid is made of two kinds of elements, linear elements for the fissure network and triangular elements for the matrix. An appropriate finite volume scheme has been developed to provide a good description of the flow at the fissure–matrix interface and a good representation of the geometry. A specific numerical treatment of fissure intersections is proposed. The method has been validated by comparison with results from a classical black-oil simulator run on a finely gridded Cartesian model. Comparisons have been done also with a dual porosity–dual permeability model. The new tool will permit to run reference simulations for the validation of new formulations of the matrix–fissure exchange in dual-porosity simulators.