Horizontal Wells for Enhanced CO<sub>2</sub> Storage in Saline Aquifers
Hasti Firoozmand, Yuri Leonenko
Abstract
CO 2 sequestration in geological formations is crucial for mitigating the excessive greenhouse gas accumulation. Saline aquifers have been identified as the most appealing targets for the secure storage of CO 2 in the subsurface. However, limited effective capacity necessitates the implementation of enhanced injection methods to take the utmost advantage of the storage potential of the aquifers. This study investigates how horizontal wells enhance storage capacity and evaluates the impact of rock characteristics and project designs. Results show that replacing vertical injection wells with horizontal wells decreases bottom-hole pressure, improves pressure distribution, and delays CO 2 plume migration to the caprock. Longer horizontal wells offer more uniform pressure distribution, reducing fracturing risks and potential CO 2 leakage. However, excessive well length may not significantly enhance the storage capacity, questioning cost-effectiveness. Plume evolution studies indicate that longer well lengths improve lateral CO 2 distribution. High-permeability aquifers exhibit greater storage capacity with horizontal wells enhancing pressure distribution across all permeability ranges. In anisotropic aquifers, horizontal well efficiency is less pronounced, requiring longer lengths to surpass vertical well performance. It was also concluded that horizontal well utilization for enhancement purposes proved to have a more beneficial effect in aquifers with low permeabilities, smaller permeability ratios, and smaller thicknesses. This study highlights the importance of aquifer characteristics in optimizing CO 2 storage with horizontal wells.