Towards the generic conceptual and numerical framework for the simulation of CO2 sequestration in different types of georeservoirs

Abstract

In this paper, conceptual and numerical modeling of coupled thermo-hydromechanical (THM) processes during CO2 injection and storage is presented. The commonly used averaging procedure combining the Theory of Mixtures and the Concept of Volume Fractions serves as background for the complex porous media approach presented here. Numerical models are based on a generalized formulation of the individual and overall balance equations for mass and momentum, as well as, in non-isothermal case, the energy balance equation. Within the framework of a standard Galerkin approach, the method of weighted residuals is applied to derive the weak forms of governing equations. After discretizing spatially these weak forms, a system of nonlinear algebraic equations can be obtained. For the required time discretization a generalized first order difference scheme is applied, linearization is performed using Picard or Newton-Raphson methods. The corresponding models are implemented within the scientific open source finite element code OpenGeoSys (OGS) developed by the authors, which is based on object oriented programming concepts. This assists the efficient treatment of different physical processes, whose mathematical models are of similar structure. Thus, the paper is mainly focused on a generic theoretical framework for the coupled processes under consideration. Within this context, CO2 sequestration in georeservoirs of different type can be simulated (e.g., saline aquifers, (nearly) depleted hydrocarbon reservoirs).