CO2 SOLUBILITY IN THE SILURIAN “CLINTON/MEDINA” SANDSTONE: MULTI-ELEMENT MODELING AND IMPLICATIONS FOR CARBON STORAGE

The long-term storage of industrial carbon dioxide (CO₂) emissions in deep geologic formations, commonly known as Carbon Capture, Utilization, and Storage (CCUS), is an essential part of mitigating the effects of CO₂ on the atmosphere. One of the ways that CO₂ can be stored is as a supercritical fluid within deep saline formations. These formations are well below the level of potable groundwater and contain heavily saturated brines. While the CO₂ and brines are considered immiscible fluids, they are mutually soluble and over time CO₂ can be dissolved into the formation water and mineral precipitation can occur, effectively trapping the CO₂. To assess the utility of potential CO₂ trapping, modeling the solubility of CO₂ for a number of wells in the Silurian “Clinton/Medina” sandstone was performed using geochemical modelling software and data of formation temperatures, pressures, and geochemistry.

Historical and modern data was collected from the Ohio Brine Geochemistry Database. The brines in the “Clinton/Medina” sandstone formation have an average total dissolved solids (TDS) of approximately 260,000 mg/L and tend to be sodium and calcium rich. Historically, solubility work has focused on using either TDS or single-element approximations of CO₂ solubility, but more recent research has shown that CO₂ solubility in aqueous solutions with different salt species is significantly different, even if the TDS is the same. Therefore, it has become necessary to use more sophisticated, multi-element geochemical models in order to accurately understand the solubility of CO₂ in these formations. In turn, this knowledge can help in assessing long-term suitability of Ohio deep saline formations for CCUS activity.