Laboratory-scale Interaction Between CO2-saturated H2SO4-rich Brine and Reservoir Rocks (Limestone and Sandstone)

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We investigated the effect of 0.36% SO2 in the CO2 injection stream (added as dissolved H2SO4) on the reactivity of the reservoir (limestone and sandstone) rocks of Hontomin (Spain) at P = pCO2 = 10bar and 60°C using flow-through column experiments. Results were modeled with the CrunchFlow reactive transport code. A comparison between the reactivity of the rocks reacted in H2SO4-free and H2SO4-rich brine showed that calcite dissolution and gypsum precipitation were elevated by 27-42% and 63-75%, respectively, in the H2SO4-rich brine. Overall rock porosity increases in H2SO4-rich brine were 7-19% higher than under H2SO4-free conditions. Porosity increases in the acid inlet zone in H2SO4-rich brine were similar to increases in H2SO4-free brine for sandstone. In limestone, porosity increases in the acid inlet zone in H2SO4-free brine were further elevated by 70% in H2SO4-rich brine.