CO2 Sequestration [Reservoir Simulation]

1. When modelling CO2 sequestration, how easy would it remain - to deduce the mathematical model that reflects the thermodynamic equilibrium between CO2 and brine, involving gas and aqueous phases (although, the solutions of CO2 and brine transport equations could be solved with ease]?

Feasible to consider the enhancement dynamics of brine density with CO2 dissolution?

2. How exactly to consider the heterogeneous chemical reactions between the aqueous species and mineral precipitation and dissolution – considering aquifer dynamics?

Whether the coupling between transport and reactions would always lead a strong non-linear system of a relatively large number of equations – that generally remains difficult to solve either with ‘sequential solution method’ (where, the flow equations and chemical equilibrium equations are solved separately and sequentially) or with ‘simultaneous solution method’ (where, all the equations are solved simultaneously with Newton’s method)? Whether any of the above two methods take into account, the downward migration of high-density saturation plumes?

Whether the chemical reactions between components in the aqueous-phase would always remain to be faster with reference to mineral precipitation/dissolution reactions? If not, then, how could we represent intra-aqueous reactions as chemical-equilibrium reactions?

3. Whether the conceptual model will keep evolving with time resulting from (a) the dynamics of gravitational segregation resulting from the huge density contrast between CO2 & brine; and (b) solubility variations of CO2 and brine leading to salt precipitation and connective mixing?

4. Can we assume a typical CO2-brine system to remain as an isothermal system, where the changes in temperature due to Joule-Thomson effect gets swiftly calibrated with the surrounding temperature?

5. Can we afford to ignore the changes in viscosities, wettability and surface-tension due to solubility? If we (a) fix CO2 density; (b) assume that the dissolution remains to be instantaneous such that the dissolution rate could be considered infinite; and (c) consider only changes in concentration based on the change of mass (while the change in the volume is taken into account across the solution of the transport equation), then, how easy would it remain to strike a balance between (a) mass; (b) volume; and (c) thermodynamic relation between concentration and density? In such cases, whether, the Peng-Robinson EoS could comfortably be applied in order to determine the component composition and compressibility factor for each phase – towards fulfilling the requirements of thermodynamic equilibrium?