Multiscale modelling of CO2-CH4 displacement in shale gas reservoirs

Abstract

Shale gas is becoming an increasingly important source in the global energy sector. Australia has one of the largest shale gas reserves globally, but the exploration is still in the very early stages. Shale reservoirs are characterised by small porosity and ultra-low permeability, with gas production from natural fractures rapidly decaying over time. CO2 injection can potentially be utilised to recover adsorbed gas from the organic matrix and achieve carbon sequestration, known as CO2-enhanced gas recovery (CO2-EGR). As shale is mainly composed of nanopores, the gas flow and transport can significantly differ from that described by conventional theories. During CO2-CH4 displacement, shale can also deform in response to gas adsorption/desorption like many other nanoporous materials, which may affect gas permeability during production. This thesis revolves around the interaction between CO2 and CH4 in porous media at nano and micro scales using molecular dynamics (MD) and the lattice Boltzmann method (LBM).