Two-phase interaction in isothermal hydro-mechanical-chemical coupling for improved carbon geological sequestration modelling

Geological sequestration is an established method to store carbon deep underground. Many studies have proposed coupled constitutive models that can simulate such a complicated process; however, the coupling effect of multi-phase fluid flow and transport of chemical solutes in the liquid phase remains to be investigated. This study presents a multi-phase non-reactive hydro-mechanical-chemical constitutive framework under isothermal conditions based on mixture coupling theory. Non-equilibrium thermodynamics is used to generate an entropy production equation, and phenomenological equations use this to derive the chemical transport and interaction between two-phase fluid flows. This study proposes novel terms in the final governing equations. The model results are in good agreement with the results of a benchmark experiment and those found in the literature; the model has been used to compare the behaviour of carbon dioxide in the gas and supercritical phases. Sensitivity analysis was conducted to determine the effect of the parameters in the new terms. Sensitivity analysis revealed the significant impact of relative permeability and saturation values on the new terms, emphasising the importance of understanding frictional behaviour in porous media for accurate fluid flow modelling and prediction. This study urges further experimentation and model refinement to improve carbon sequestration modelling in larger formations.