An integrated site characterization-to-optimization study for commercial-scale carbon dioxide storage

Abstract Injection of supercritical carbon dioxide (scCO 2 ) into deep saline aquifers is considered a promising option to mitigate global climate change. At a storage site, the main objectives of carbon dioxide sequestration are to maximize the volume of scCO 2 injected and minimize the leakage risk, while effectively managing formation fluid pressure buildup and the brine displaced by scCO 2 . An integrated characterization-to-optimization study is carried out for potential commercial-scale deep saline aquifer carbon dioxide storage proposed in western Wyoming. A three-dimensional heterogeneous reservoir model is built for which petrophysical and fluid flow parameters are populated using field characterization data and state-of-the-art laboratory measurements. The measured scCO 2 relative permeability end point is low compared to previous measurements on similar sandstones, which poses a challenge for CO 2 flow, formation pressure control, and storage efficiency. By carefully selecting a set of optimal well locations, perforation intervals, and bottomhole pressure constraints that lead to maximum CO 2 -in-place and minimal CO 2 breakthrough at the producers, an injection rate ranging from 10.8 to 15.1 Mt/year is achieved for a duration of 50 years. After scCO 2 injection ceases, up to 62% of the total injected scCO 2 can be immobilized as residual scCO 2 in 1000 years. Because of the low scCO 2 relative permeability end point, post-scCO 2 -injection chase brine operation is not found to be an effective means of enhancing residual trapping. Instead, by modulating reservoir fluid pressure, boundary conditions of the reservoir exert a more significant impact on flow. Given the same well configuration and bottomhole pressure constraints, an open reservoir with lateral background flow allows 40% additional scCO 2 injection compared to a compartmentalized system without background flow. However, background flow leads to a lower trapping efficiency – after 1000 years post-scCO 2 -injection, only 54% of the total injected scCO 2 is immobilized as residual scCO 2 . This research suggests that a careful engineering design can contribute to significant CO 2 storage at commercial scales while enhancing storage security. Site-specific multi-phase flow data should be measured for such a design, since for the study site, chase-brine operation is not effective when scCO 2 relative permeability is low.