Numerical simulation of non-isothermal multiphase multicomponent processes in porous media.: 1. An efficient solution technique

Modeling non-isothermal multiphase multicomponent flow and transport processes in the subsurface requires the consideration of the transfer of mass and energy between the phases in addition to the flow processes such as advection and diffusion. We developed a multidimensional numerical simulator, in which we implemented new efficient solution techniques. The description of the physical and thermodynamical state yields a system of four strongly coupled partial differential equations. The set of phases (phase state) present in the porous medium is variable in space and time. In order to take this into account, we implemented an algorithm that allows an adaptive switching of the primary variables according to each phase state. We apply a Newton algorithm for the linearization of the equations. For the solution of the arising linear equations, we extended a multigrid method and adapted it to the problem of variable phase states. First results of this new solution technique are given in the paper.