ON REGIONAL PRESSURE BUILDUP AND FLUID MIGRATION IN RESPONSE TO LARGE CO2 INJECTION OPERATIONS

Several international researchers have in recent years evaluated the potential basin-scale hydrological impacts resulting from the storage of large volumes of CO₂ in deep saline aquifers and the related large-scale brine pressurization and migration processes. It was shown in these studies that the areas impacted by pressure changes can be very large and that brine pressurization might impact caprock integrity and groundwater resources. For example, overpressure over much of a basin can provide a driving force pushing brine upward into overlying freshwater aquifers via possibly existing localized pathways. The present abstract provides recent studies and insights on this topic. We discuss the results from high-performance models for two sedimentary basins in order to illustrate the potential for regional fluid migration processes related to industrial-scale CO₂ storage operations. We also provide results from sensitivity analyses to identify key parameters and processes for pressure buildup and brine migration. Here we distinguish between the near-field region comprising the projected size of the plume, where hydrogeological properties are expected to be better constrained, and the far-field region comprising the projected extent of pressure buildup, where parameter uncertainty can be quite high. We finally touch on the concept of a critical pressure threshold below which upward leakage of saline formation water into an overlying freshwater aquifer is unlikely.