EVALUATING MOBILIZATION POTENTIAL OF TRACE METALS FROM THE MT. SIMON SANDSTONE AND EAU CLAIRE FORMATION UNDER GEOLOGICAL CO2 SEQUESTRATION CONDITIONS

Geological CO₂ sequestration (GCS) is one of the most promising strategies to mitigate future adverse effects of CO₂ concentration increases in the atmosphere. To ensure successful deployment of this climate mitigation strategy, risks associated with GCS need to be fully assessed. Geologic formations for GCS may contain toxic metals that naturally occur in minerals. Injecting CO₂ into these formations may decrease the pH of the formation fluids (brines), inducing mineral dissolution or desorption, and thus has the potential to mobilize metals into brine. A better understanding of the distribution of trace metals in potential CO₂ sequestration sites as well as the conditions under which GCS might cause their release is important to assess potential environmental and health risks associated with GCS. Little work has been done in this area to date. In this work rock and brine samples were collected from a large-scale, CO₂ sequestration site, the Illinois Basin - Decatur Project, from depths of 800-2,200m below ground surface. The presence of trace metals that are regulated by US EPA for drinking water were observed in some of the rock core samples. Trace metal distribution in the rocks as well as the relationships of this distribution with the depositional/diagenetic characteristics of the rocks are being investigated. CO₂-rock-brine interaction experiments in high pressure vessels are being conducted to determine the potential of metal mobilization at reservoir conditions. The factors that influence metal mobilization from rocks will also be presented.