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).
