Numerical simulation of two-phase flow in deformable porous media: Application to carbon dioxid estorage in the subsurface

摘要

In this paper, the conceptual modeling as well as the numerical simulation of two-phase flow in deep, deformable geological formations induced by CO2 injection is presented. The conceptual approach is based on balance equations for mass, momentum and energy completed by appropriate constitutive relations for the fluid phases as well as the solid matrix. Within the context of the primary effects under consideration, the fluid motion will be expressed by modified Darcy's law for two phase flow. Additionally, constraint conditions for the partial saturations and the pressure fractions of carbon dioxide and brine are defined. To characterize the stress state in the solid matrix the effective stress principle is applied. Furthermore, the interaction of fluid and solid phases is illustrated by constitutive models for capillary pressure, porosity and permeability as functions of saturation. Based on the conceptual model a coupled system of nonlinear differential equations is formulated modeling the two-phase flow in a deformable porous matrix (H2M model). As the displacement vector acts as primary variable for the solid matrix, considering the fluid motion pressure/pressure or pressure/saturation for multiphase flow are implemented. The finite element method is used to solve the multi-field problem numerically. The capabilities of the model and the numerical tools to treat complex processes during CO2 sequestration has been demonstrated by benchmark examples beforehand. Here we present two examples:①a new benchmark test for H2M processes and②a 3-D example to test the stability and computational costs of the H2 model for real applications.