4.2 Objectives of geochemical modelling in CO2 geological storage

The study of rock-CO2-fluid chemical interactions is essential to assess storage integrity. It allows evaluation of the injected CO2behaviour, and thus provides a guide for monitoring during and after injection. Storage integrity issues which may be addressed by reactive transport modelling of CO2 and fluid flow in the subsurface include: confinement in the injection zone, CO2 partitioning into the rock and fluid phases via mineralisation and dissolution, and potential impacts to groundwater from CO2 leakage.

In the previous chapter, various modelling codes allowing the modelling of chemical processes in the subsurface have been described. These models range from equilibrium models, reaction-path models and kinetic models, to coupled reactive transport models. Reactive transport models account for the coupling between transport and chemical reaction. They are thus more computationally intensive than non-coupled codes because of additional reactions, multiple variables and associated degrees of freedom (NETL, 2011).

Gaus et al., 2008 have identified three main application domains when assessing the geochemical impact of CO2 storage. They are presented in the following sub-sections.

 

in depth

4.2.1 Long-term integrity modelling

Modelling of long-term integrity aims to assess the ultimate fate of the injected CO2 and its impacts on physical proper...

4.2.2 Injectivity modelling

When modelling the injectivity phenomena, the time scale of interest is the injection period itself and generally, the s...

4.2.3 Well integrity modelling

Well integrity modelling focuses on the geochemical impacts of CO2 on the well completion itself. Well completions are m...