Optimal design of injection/extraction wells for the surface dissolution CO2 storage strategy

Abstract

Implementing geological carbon sequestration at a scale large enough to mitigate anthropogenic emissions will involve the injection of supercritical CO2 into deep saline aquifers. The principal technical risks associated with such injection are that (i) buoyant CO2 will migrate out of the storage formation; (ii) pressure elevation during injection will limit storage rates and/or fracture the storage formation; and (iii) groundwater resources will be contaminated, directly or indirectly, by brine displaced from the storage formation. An alternative to injecting CO2 as a buoyant phase is to dissolve it into brine extracted from the storage formation, then inject the CO2-saturated brine into the storage formation. This “surface dissolution” strategy completely eliminates the risk of buoyant migration of stored CO2. It greatly mitigates the extent of pressure elevation during injection. It nearly eliminates the displacement of brine. To gain these benefits, however, it is essential to determine the costs of this method of risk reduction. In this work, we compute the pressure field for typical injection patterns and quantify the restriction imposed by this field on the design of the process. We also develop an analytical framework for optimization of the process, and hence for cost minimization.