Quantitative Assessment of CO₂ Mineral Trapping Capacity in Presence of Sealing Fault in Carbonate Sequences: A Numerical Approach

Mineral trapping is believed to be the safest and the most secure CO₂ sequestration technique where the injected CO₂ could be mineralized in the long-term (exceeding 10² - 10³ years) geologically within subsurface formations. Nevertheless, the high complexity associated with CO₂ mineral trapping capacity predications obscures the in-depth understanding of CO₂ mineralization. In this study, a numerical simulation is adopted to demonstrate the impact of carbonate mineralogy in presence of a sealing fault on CO₂ mineral trapping capacity. Field-scale CO₂ pilot topographic model for three distinct carbonate minerals is simulated to depict the mineral trapping capacity. Thus, realistic petrophysical parameters, reservoir characteristic curves, and other in-situ conditions are upscaled to mimic carbonate formations. Thereafter, the amount of CO₂ mineralized is estimated for compositionally distinct reservoirs. Additionally, the effect of injection pressure on CO₂ mineralization is assessed upon precipitation/dissolution kinetics calculations. Moreover, the effects of well placement and perforation depth on mineral trapping potential of calcite, dolomite, and siderite dominant reservoirs are assessed. The mineral trapping capacities computed show that increasing injection pressure (base injection pressure to 1.5*base injection pressure) monotonically increased the mineral trapping capacities for calcite and dolomite. However, siderite seems slightly insensitive to the injection pressure increase. This monotonic trend is attributed to enhanced radial displacement and restricted plume migration upward as the injection pressure increases. Moreover, proper CO₂ injector placement showed significant enhancement in mineral trapping capacity especially if the injector is near to the fault plane on the leaking side. This study provides in-depth theoretical understanding of the mineralogy effect on CO₂ mineralization potential in faulty carbonate sequences. This is driven by the insignificance interest mineral trapping has gained over the years compared to other trapping mechanisms. This is because of the extremely long storage duration needed for mineral trapping to reach its maximum potential. Importantly, the results suggest that CO₂ mineralization within carbonate reservoirs immobilize CO₂ - thus assisting in stable and long-term permanent storage.