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A numerical model for water-oil flow in naturally fractured reservoirs

This paper describes the development of a three-dimensional, two-phase model for simulating the flow of water and oil in naturally fractured reservoirs. The model is based on the dual porosity approach. Main flow in the reservoir occurs within the fractures with local exchange of fluids between the fracture system and matrix blocks. A new formula for matrix/fracture fluid exchange rate is proposed based on an extension of the equation developed by Kazemi to account the gravity effects. | Vietnam Journal of Mechanics, VAST, Vol. 26, 2004, No. 1 (31 - 38) A NUMERICAL MODEL FOR WATER-OIL FLOW IN NATURALLY FRACTURED RESERVOIRS HA NGOC HIEN , NGUYEN VAN DIEP AND DUONG NGOC HAI Institute of M echanics, VAST, 264 Doi Can, Hanoi, Vietnam A BSTRACT. This paper describes the development of a three-dimensional, two-phase model for simulating the flow of water and oil in naturally fractured reservoirs. The model is based on the dual porosity approach. Main flow in the reservoir occurs within the fractures with local exchange of fluids between the fracture system and matrix blocks. A new formula for matrix/fracture fluid exchange rate is proposed based on an extension of the equation developed by Kazemi to account the gravity effects. This formula allows to eliminate the matrix pressure in the pressure equation for fractures and makes the solution algorithm easier. Some example calculations are presented to validate the model. These include a comparison of the results of this paper with previous results, showing the gravity effects and applicability of the model for field-scale problems. 1 Introduction Fractured reservoir models were developed to simulate fluid fl.ow in a system of continuous fractures of high permeability and low porosity that surround porous, oil-saturated matrix blocks of much lower permeability but higher porosity. The main difference between fl.ow in fractured medium and flows in conventional porous system is that, in the fractured medium, the interconnected fracture network provides the main path for fluid fl.ow through the reservoir , while local flows (exchanges of fluid) occur between the matrix blocks and the surrounding fractures. Matrix oil flows into the fractures , and the fractures carry the oil to the wellbore. Most of fractured reservoir models are constructed based on the dual porosity approach. The reservoir is considered as two overlying continua, the matrices and the fractures , in which the fl.ow is governed by Darcy