The basic tool for fractured reservoir studies is the dual-porosity (-permeability) model. Using the Warren and Root concept of rectangular parallelepiped blocks, this (sugar box) model is generally considered as unrealistic by geologists. On the other hand fluid flows within the matrix blocks are not simulated (one node) and the matrix-fracture exchanges within a cell are generally lumped in one connection including horizontal and vertical flows. This requires to compute and input pseudo kr-Pc curves which depend on the matrix petrophysical properties, block sizes and fluids present both in the matrix and the surrounding fractures.
To improve the accuracy and speed up the fractured reservoir studies, IFP developed a complete methodology of modelling and simulation which includes:
a software giving a realistic and stochastic picture of the fracture network after a geologic characterization of the different fracture sets;
a software taking the above picture as input and computing the equivalent parameters of a dual-porosity model so that the anisotropy of the fracture system and the oil recovery versus time of a matrix block surrounded by another fluid are the same in the simulator as in the geological model;
a dual-porosity, dual-permeability model which uses the above parameters and where the fracture-matrix flows are simulated according to their direction and to give the true kinetics and final recovery without using arbitrary pseudo functions.
laboratory test technology and procedures to measure, in reservoir conditions, the required parameters. These tests also provided examples to benchmark our simulator. They are not described in the present paper1 ,2 .
This paper describes the complete methodology and details the specific fracture-matrix flow formulation, which could be input in other dual-porosity simulators. The presented cases indicate that geologists and engineers can cooperate in a really-integrated fractured reservoir study based on a realistic picture of the fracture network. In addition, the modification of the matrix-fracture flow terms improves the model accuracy and speeds up the study as it does not require to prepare any pseudo curve.