Mineralogical controls on porosity and water chemistry during O 2 -SO 2 -CO 2 reaction of CO 2 storage reservoir and cap-rock core

Impact of SO2 on Alteration of Reservoir Rock with Ca-Deficient Conditions and Poor Buffering Capacity under a CO2 Geologic Storage Condition

“…This result shows that a higher content of SO 2 leads to enhanced mineral dissolution through formation of an acidified condition. This is because the dissolution of silicate minerals is pH-dependent [29,34] and our result is also in good agreement with other studies [4,6,13,15,33]. This is clearly shown by the changes in the quantities of the minerals with time ( Figure 4).…”

“…In the 1% SO 2 case, the pH significantly decreased to 1.84. In the presence of SO 2 , the formation of sulfuric acid increased the number of H + ions in the water, thereby reducing the pH more than if reacting with pure CO 2 [15,33]. This can be supported by the sulfate concentrations measured in the experiments (Figure 3).…”

“…In contrast, chlorite (4.8 wt.% of total minerals) caused the release of a large amount of Fe and Mg. Chlorite plays an important role in the increase in Fe and Mg concentrations in other studies under CO 2 -rich conditions [6,15,37,38].…”

“…However, to the best of our knowledge, most studies on the effect of SO 2 have been performed in rocks containing Ca-rich minerals (e.g., calcite and anorthite), easily buffering the pH [4,6,8,[12][13][14][15][16]. These studies showed that SO 2 did not largely influence the alteration of reservoir rocks because pH was quickly buffered enough to prevent significant dissolution of silicate minerals.…”

“…In contrast, a very low pH (<2) during the experiments in the 1% SO 2 case shows insufficient buffering capacity. On the other hand, several researchers have shown that even when strong sulfuric acid is formed in solution due to the presence of SO 2 , pH can be buffered if carbonate minerals are sufficiently present in the reservoir rocks [6,15].…”