In the era of climate change mitigation, the significance of numerical simulation in Carbon Capture, Utilization, and Storage (CCUS) technologies cannot be overstated. This paper introduces an innovative framework for reactive transport modeling of subsurface CO2 injection. Its primary aim is to establish an efficient transport model with full speciation capabilities, leveraging a geochemical solver that accommodates both equilibrium and kinetic reactions. Furthermore, this paper outlines a pragmatic workflow for elucidating critical geochemical parameters governing the interplay between CO2-enriched aqueous phases and mineral assemblages.
This paper presents a comprehensive approach to modeling reactive transport during CO2 injection in subsurface environments. It encompasses geochemical batch reactions, including equilibrium and kinetic reactions to capture aqueous species and mineral interactions. This step is vital for understanding and conducting sensitivity analyses on rock and chemical parameters. The established chemical setup is integrated into a full-field simulation using a commercial reservoir simulator, incorporating both isothermal and thermal models. The simulator is coupled to an external geochemistry library, PHREEQC, using the PHREEQCRM module and Reaktoro. Once the system is solved for the given constraints, the transport parameters are updated. This results in an efficient coupling between transport and geochemistry.
The proposed framework is first applied to modeling Dolomitization in a mostly Calcite-rich rock. Magnesium-rich brine is injected into the reservoir (or the influx is modeled by fluid rising through faults) and under certain chemical conditions, Dolomite is precipitated. These are modeled using equilibrium reactions. Next, more complex aqueous phase and mineralogy are considered while modeling injection of CO2 into various subsurface systems. This investigation spans both one-dimensional and three-dimensional full-field simulations with heterogeneous formations and varying brine, both Magnesium and CO2 rich, injection rates. Long-term simulations show the temporal interaction between rock and the aqueous phase, which is key in quantifying the uncertainty in the subsurface processes.