CO₂ Sequestration in Deformable, Chemically Interactive, Porous Media

Abstract

CO₂ sequestration is one of the critical areas of research throughout the world, as it is a major step to investigate non-fossil fuel energy sources. One of the biggest challenges in this field is designing and developing an effective methodology for modelling the CO₂ sequestration system, which depends on the proficiency of using different parameters and processes of CO₂ sequestration. The geochemical and geomechanical processes are the most significant components for establishing this system, which relies on adaptable utilising the effects of various parameters including pressure, temperature, salinity, impurities in the supercritical phase, and mechanical deformation. These parameters can considerably alter the behaviours of geochemical systems. Although the existing codes can address several challenges in the geochemical problems, these codes do not fully account for many of the above effects.

Consequently, in this thesis, four integrated models (Model A, B1, B2 and C) are developed, with each model is building on the previous, for the purpose of investigating several factors previously not considered in the CO₂ sequestration geochemical model. Models A and B1 account for the explicit corrections of high pressure and salinity on the activity coefficient models and water activity; the effects of pressure and salinity on the chemical equilibrium and solubility constants; and the effect of pressure on mineral activities before and after the injection of CO₂. Model B2 also includes the effect of impurities such as sulphur dioxide (SO₂) in the supercritical phase. Model C also accounts for chemical-mechanical coupling, based on a new equation for coupling of mechanics on chemistry via the solid activity coefficient and chemical effects on the mechanics through the mineral dissolution.

The proposed models are applied to analyse a limestone aquifer saturated with saline water, CO₂ sequestration in a limestone saline aquifer, CO₂/SO₂ sequestration in a limestone saline aquifer, and CO₂ sequestration in a mechanically deformable limestone saline aquifer. The results showed that the proposed models have a great impact on enhancing the existing geochemical systems with utilising the above parameters and processes. Moreover, the results revealed their superiority at the coupling of chemical-mechanical processes compared with some existing tools.