Theoretical and Numerical Aspects of Modelling Geological Carbon Storage with Application to Muographic Monitoring

The storage of waste carbon dioxide (CO2) from fossil fuel combustion in deep geological formations is a strategy component for mitigating harmfully increasing atmospheric concentrations to within safe limits. This is to help prolong the security of fossil fuel based energy systems while cleaner and more sustainable technologies are developed. The work of this thesis is carried out as part of a multi-disciplinary project advancing knowledge on the modelling and monitoring of geological carbon storage/sequestration (GCS). The underlying principles for mathematically describing the multi-physics of multiphase multicomponent behaviour in porous media are reviewed with particular interest on their application to modelling GCS. A fully coupled non-isothermal multiphase Biot-type double-porosity formulation is derived, where emphasis during derivation is on capturing the coupled hydro-thermomechanical (HTM) processes for the purposes of study. The formulated system of governing field equations is discretised in space by considering the standard Galerkin finite element procedure and its spatial refinement in the context of capturing coupled HTM processes within a GCS system. This presents a coupled set of nonlinear first-order ordinary differential equations in time. The system is discretised temporally and solved using an embedded finite difference method which is schemed with control theoretical techniques and an accelerated fixed-point-type procedure. The developed numerical model is employed to solve a sequence of benchmark problems of increasing complexity in order to comprehensively study and highlight important coupled processes within potential GCS systems. This includes fracture/matrix fluid displacement, formation deformation and Joule-Thomson cooling effects. The computational framework is also extended to allow for the simulation of cosmic-ray muon radiography (muography) in order to assess the extent to which detected changes in subsurface muon flux due to CO2 storage can be used to monitor GCS. This study demonstrates promise for muography as a novel passive-continuous monitoring aid for GCS.