Basin-scale study of CO₂ storage in stacked sequence of geological formations

Commercial scale decarbonization through carbon capture and storage may likely involve many CO₂ storage projects located in close proximity. The close proximity could raise concerns over caprock integrity associated with reservoir pressure buildup and interference among adjacent projects. Commercial-scale injection will also require large prospective CO₂ storage resource and high injectivity in the targeted storage formations. To accommodate the need for both large resource and high injectivity, project operators could consider injecting CO₂ into a stacked sequence of formations. This analysis investigates the benefits of injecting CO₂ into a vertically stacked sequence of saline formations, over injecting the same amount of CO₂ into a single saline formation, in addressing these challenges. Our analysis shows that injecting into the stacked sequence mitigates the extent of pressure buildup among the stacked formations, while still achieving the same or greater target CO₂ storage volumes. Among cases modeled, the resulting pressure buildup front is most reduced when each storage site distributes injection volumes over several wells, each of which injects a portion of the total CO₂ mass across the stacked sequence. This favorable case not only results in the smallest CO₂ aerial footprint, but also shows the largest reduction in the pressure buildup at the top of perforation at the injection wells (upwards of approximately 46% compared to the single-formation storage), the result of which is crucial to maintain caprock integrity. This analysis provides insights into required decision-making when considering multi-project deployment in a shared basin.