CO2 Leakage Prevention Technologies

Abstract A central challenge of both scientific and regulatory interest is how to ensure carbon dioxide (CO2) is securely contained within a storage site. The fate of CO2 in the subsurface describes the range of processes that progressively trap the CO2. Pure phase CO2 can be trapped within the pore space as (i) residual saturation, and (ii) capillary trapping where the buoyancy forces exerted by a vertical column of CO2 are not sufficient to overcome the capillary forces either within the reservouir rock or to overcome the caprock. Aside from the physical trapping of free CO2, it can be trapped as an aqueous phase. An alternative to injection of pure phase CO2 is to inject CO2 saturated waters which are denser than the unsaturated formation waters thus eliminating the problems associated with buoyancy. Further, in order for the CO2 to be locked away geochemically as mineral trapping, it must first enter an aqueous phase in order for it to be reactive. Here we explore engineering technologies for enhancing the dissolution of CO2 in formation fluids to mitigate leakage and minimise the risk of CO2 escaping from the storage site. Conceptual process engineering and design of CO2 injection systems downstream were performed with primary aim of rendering integrated injection strategies suitable for use in enhancing permanent storage of CO2 in deep geological formations. The results of the application indicate that the strategies speed up CO2 dissolution and immobilisation as the period of time needed to achieve immobilisation in the subsurface formation is enhanced by the surface processes engineering. The immobilised CO2 will remain indefinitely in the storage zone even if the integrity of the caprock is not intact. These innovative engineering technologies provide leakage prevention opportunities which are fundamental to addressing long-term risk management and monitoring issues for CO2 storage sites.