Thermo-Hydro-Mechanical-Chemical Modelling for Carbon Capture and Storage: A Mixture Coupling Theory Approach

In pursuit of advancing the field of geoenergy, this thesis presents a Thermo-Hydro-Mechanical-Chemical (THMC) model specifically derived for the simulation of Carbon Capture and Storage (CCS) processes. The introduced model addresses the dynamic interactions of gas migration, water transport, and mechanical deformation in deformable porous media. Building upon mixture-coupling theory and based on non-equilibrium thermodynamics, the model introduces novel perspectives and governing equations that capture the complexities of two-phase fluid dynamics and the details of chemical reactions within a geological context. Moreover, central to this thesis is the characterisation of the coupling effects among fluid phases, solid deformation, and thermal properties, which are crucial in determining the efficiency and sustainability of CCS operations. Through comparison with experimental data from the literature, the developed model showed good agreement with the data. Sensitivity analyses within the studies further shed light on the critical roles of relative permeability and saturation, revealing the subtleties of frictional behaviour and its implications for fluid flow in porous media.
Additionally, the model is further extended by incorporating chemical reaction dynamics, providing insights into the significant influence of calcite dissolution on porosity and permeability alterations. The simulations reveal that chemical reactions are not simply a secondary factor but a driving force in the evolution of geological storage properties. The research findings also indicate that temperature variations significantly affect dissolution processes, with long-term implications for porosity and permeability.
As the global community confronts the challenges of climate change, the importance of refining CCS strategies cannot be overstated. This thesis extends the existing mixture coupling theory for two-phase transport, accounting for energy losses from two-phase interactions (friction) and solute transport within the mixture. Additionally, it integrates a chemical coupling process into the two-phase model (dissolution process) by utilizing the concepts of affinity and extent of the reaction. Furthermore, thermal coupling is included to develop a novel two-phase THMC coupled model that can be used to simulate CCS process, primarily for academic purposes, with the potential for real-world field applicability through further extensions. Future research directions are proposed to further fine-tune the model, ensuring that it remains responsive to the complex and evolving demands of environmental sustainability and energy management.