Influence of Clay Content on CO2-Rock Interaction and Mineral-Trapping Capacity of Sandstone Reservoirs

Abstract

The injection of carbon dioxide (CO2) is an essential technology for maximizing the potential of hydrocarbon reservoirs while reducing the impact of greenhouse gases. However, because of the complexity of this injection, there will be many different chemical reactions between the formation fluids and the rock minerals. This is related to the clay content of sandstone reservoirs, which are key storage targets. Clay content and clay types in sandstone can vary substantially, and the influence of these factors on reservoir-scale CO2-water-sandstone interactions has not been managed appropriately. Consequently, by simulating the process of CO2 injection in two different clay-content sandstones (i.e., high- and low-clay content), we investigated the effect of the sandstone clay concentration on CO2-water-sandstone interactions in this article. High clay content (Bandera Grey sandstone) and low clay content (Bandera Brown sandstone) were considered as potential storage reservoirs and their responses to CO2 injection were computationally assessed. Our results indicate that the mineralogical composition of the sandstone reservoir significantly varies as a result of CO2-water-sandstone interactions. Clearly, the high clay-content sandstone (Bandera Grey) had a higher maximum CO2 mineral-trapping capacity (6 kg CO2/m3 sandstone) than Bandera Brown Sandstone (low clay content), which had only 3.3 kg CO2/m3 sandstone mineral-storage capacity after 400 years of storage. Interestingly, pH was decreased by ~3 in Bandera Grey sandstone and by ~2.5 in Bandera Brown sandstone. Furthermore, porosity increased in Bandera Grey sandstone (by +5.6%), more than in Bandera Brown Sandstone (+4.4%) after a 400-year storage period. Overall, we concluded that high clay-content sandstone shows more potential for CO2 mineral-trapping.