A method of FE modeling multiphase compressible flow in hydrocarbon reservoirs

Abstract

We propose a model and numerical method for multiphase multicomponent flow simulation in porous media for solving problems of hydrocarbon reservoir engineering. The method takes into account the complex structure of reservoirs, a large number of operating wells, various methods of specifying the dependences of the properties of phases on pressure and mass fractions of their components, the transition of components from one phase to another, as well as compressibility and gravity. The method provides a sufficiently high computational efficiency, local conservation of mass for each component and protects the requirement of constraint of phases saturations from violation due to the following aspects. To calculate the phase flows we use a combination of continuous Galerkin finite element method (CG FEM) with a new balancing method. This combination provides high accuracy of flows calculated from the pressure field on rather coarse meshes. We also propose to use the grouping of finite elements, which allows us to remove strict restrictions on the time step when calculating the phase flows between cells. Verification of the proposed method is performed by comparing with the results of SPE tests. The effectiveness of the method is demonstrated both on simple model problems and on problems of modeling a complex reservoir. For a real field of high-viscosity oil in Tatarstan (Russia), a good agreement between the computed and observed data is obtained for all high-rate wells over a fairly long period of field development.