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

Abstract

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.