Aquifer Management To Accelerate CO2 Dissolution and Trapping

Abstract

Summary Bulk-phase CO2 injection into saline aquifers can provide substantive reduction in CO2 emissions if the risk arising from aquifer pressurization is addressed adequately through mechanisms such as brine production out of the system (Anchliya 2009). While this approach addresses the risks associated with aquifer pressurization it does not address the problem of ensuring CO2 trapping as an immobile phase and its accumulation at the top of the aquifer. The performance of bulk-CO2-injection schemes highly depends on the seal-integrity assessment and presence of thief zones. The accumulated pocket of free CO2 can readily leak through a breach in the aquifer seal. Ideally, the aquifer should be monitored as long as the free CO2 is present, but if the CO2 is not immobilized, it is expected to remain underneath the seal rock for more than 1,000 years. Therefore, long-term monitoring of the seal integrity and avoiding leakage will be very costly. To minimize the free CO2 below the caprock, we propose an engineered system to reduce aquifer pressurization and accelerate CO2 dissolution and trapping. We achieve these objectives through effective placement of brine injection and production wells to facilitate the lateral movement (hence, residual and solubility trapping) of CO2 in the aquifer and impede its upward movement. The simulation results for example engineered well configurations in this paper suggest that substantial improvements in immobilizing CO2 can be achieved through increasing enhanced solubility and residual trapping that result from better CO2-injection sweep efficiency. This approach has the potential to greatly reduce the risk of CO2 leakage both during and after injection. The controlled injection of CO2 with this technique reduces the uncertainty about the long-term fate of the injected CO2, prevents CO2 from migrating toward potential outlets or sensitive areas, and increases the volume of CO2 that can be stored in a closed aquifer volume during the CO2-injection period. Field-scale compositional simulation cases are discussed, and sensitivity studies are used to provide guidelines for well spacing and flow rates depending on aquifer properties and the volume of CO2 to be stored. Although it requires additional drilled wells, the active engineered configuration proposed for CO2 injection significantly reduces the reservoir volume required to effectively sequester a given volume of CO2, and the increase in the cost caused by additional wells is recovered by dramatic reduction in monitoring cost.

CO2 Storage Engineering: Real Solution to Real Problems

“…GEM is a three-dimensional, multi-phase compositional, single or dual porosity simulator and includes CO 2 trapping by pore volume, CO 2 dissolution and mineralization. 3 Figure 3 provides a three dimensional view of the grid blocks and the location of the CO 2 injection well used for modeling CO 2 injection into the Oriskany saline formation.…”

Increasing CO2-Storage Efficiency Through a CO2/Brine-Displacement Approach

“…Because the aquifer pressure will rise during bulk-CO 2 injection, recommended regular pressure-falloff testing in CO 2 -injection wells to monitor aquifer-pressure behavior and, in particular, to watch for evidence that CO 2 may be leaking from the aquifer. Anchliya et al (2012) investigated producing the same volume of brine as is injected as CO 2 to avoid pressurizing the aquifer, and they found that this increases the aquifer-storage efficiency. This study also investigated brine injection above the CO 2 injection as a way to keep the CO 2 plume from rising to the top of the aquifer, thereby accelerating CO 2 trapping and dissolution.…”

Optimization of Geologic CO2 Storage in Heterogeneous Aquifers Through Improved Sweep Efficiency

“…Most of the trapped CO 2 is anticipated to dissolve in the formation water over a long period of time (Ennis-King and Paterson, 2003). Residual trapping can, however, be invoked through intelligent engineered design of the storage system (Anchliya et al, 2010;Hassanzadeh et al, 2009;Keith et al, 2005;Leonenkoy and Keith, 2008;McMillan and Bryant, 2007). The poor sweep efficiency of the injected CO 2 can also affect the residual trapping.…”

“…The methods that have been recently proposed to accelerate CO 2 sequestration are based on brine injection (Keith et al, 2005;McMillan and Bryant, 2007;Leonenkoy and Keith, 2008;Hassanzadeh et al, 2009;Anchliya et al, 2010). The effect of simultaneous CO 2 and brine injection and also water-alternate-gas systems have been studied by several authors (Juanes et al, 2006;Sifuentes et al, 2009;Anchliya et al, 2010).…”

“…The effect of simultaneous CO 2 and brine injection and also water-alternate-gas systems have been studied by several authors (Juanes et al, 2006;Sifuentes et al, 2009;Anchliya et al, 2010). These methods can affect both residual and solubility trapping.…”