NUMERICAL ASSESSMENT OF EFFECTS OF POROELASTICITY TO SUSTAINED IN-SITU CO2 MINERALIZATION IN OLIVINE FORMATIONS

Objectives/Scope: Inducing in-situ carbonation reaction of Olivine (Mg2SiCO4) is a promising strategy to assist geologic carbon dioxide (CO2) storage. Mineralization of CO2 may be accompanied by a significant decrease of rock porosity over time, eventually leading to clogging of the available porous spaces. Here, we perform a set of numerical poroelastic simulations of in-situ CO2 mineralization scenarios taking place within geological olivine formations. We aim at quantifying the impact of reaction-driven cracking of the formation to the effectiveness of CO2 mineralization. We then identify a range of environmental conditions where porosity reductions allow sustained in-situ mineralization. Methods/Procedures/Process: We consider the poroelastic model formulation to simulate flow and transport in porous media performed in TerraFERMA toolkit environment. Fluid-rock interactions are evaluated by integrating: (i) fluid flow dynamics, (ii) geochemical reactions, and (iii) rock deformation processes. Our numerical simulations are set up to account for a reaction driven cracking process which may take place due to changes in rock surface energy and associated tensile stress. We consider diverse scenarios of CO2 carbonation, incorporating a variety of environmental conditions of pressure, temperature, and pH. Results/Observations/Conclusions: We evaluate the kinetics of olivine dissolution under conditions relevant to the aqueous mineral carbonation process at diverse environmental conditions. Our numerical study can assist the assessment of changes of rock surface energy that, in turn, may lead to significant fluid overpressure and tensile stress across high-permeability pathways. These might then lead to tensile failure of the host rock. This can result in reaction-induced fracturing which enables continuous fluid migration and CO2 carbonation while keeping sufficiently constant values of rock average porosity across the simulation time window. The analysis of various environmental scenarios of CO2 yields a set of preliminary recommendations about conditions that are likely to prevent the immediate reaction-derived reduction of porosity and clogging of flow pathways across the system. Our results suggest that for high values of alkalinity conditions (pH > 7), optimal injection of CO2 in olivine formations should be associated with large depths (e.g., larger than about 5 km, corresponding to a temperature of about 120°C and hydrostatic pressure conditions of about 50 MPa). Otherwise, CO2 mineralization under acidic aqueous conditions (pH < 5) can be effective at shallow depths (of roughly 1 km depth, 50°C temperature, and 10s MPa pressure). Intermediate depths (e.g., about 3 km) are preferred for CO2 mineralization in balanced (neutral) state conditions. Novel/Additive Information: Our study highlights conditions to assist integrity of depth dependent (i.e., temperature and pressure) characteristics of the sequestration site as a function of environmental pH conditions in the context of enhancement of CO2 mineralization in olivine formations.