Enhanced CO2 Storage and Sequestration in Deep Saline Aquifers by Nanoparticles: Commingled Disposal of Depleted Uranium and CO2

Abstract

Geological storage of anthropogenic CO 2 emissions in deep saline aquifers has recently received tremendous attention in the scientific literature. Injected buoyant CO 2 accumulates at the top part of the aquifer under a sealing cap rock. Potential buoyant movement of CO 2 has caused some concern that the high-pressure CO 2 could breach the seal rock. However, CO 2 will diffuse into the brine underneath and generate a slightly denser fluid that may induce instability and convective mixing. Onset times of instability and convective mixing performance depend on the physical properties of the rock and fluids, such as permeability and density contrast. We present the novel idea of adding nanoparticles (NPs) to injected CO 2 to increase density contrast between the CO 2 -rich brine and the underlying resident brine and, consequently, decrease onset time of instability and increase convective mixing. The analyses show that 0.001 volume fraction of NPs added to the CO 2 stream shortens onset time of mixing by approximately 80% and increases convective mixing by 50%. If it thus originally takes 5 years for the overlying CO 2 to start convective mixing, by adding NPs, onset time of mixing reduces to 1 year, and after initiation of convective mixing, mixing improves by 50%. A reduction of the CO 2 leakage risk ensues. In addition to other metallic NPs, use of processed depleted uranium oxide (DU) as the NPs is also proposed. DU-NPs are potentially stable and might be safely commingled with CO 2 to store in saline aquifers.

The effect of designing parameter of WAG injection on enhancement of CO2 trapping in heterogeneous formations: A numerical study

“…In fact, for the chosen example realization of permeability field, the area containing mobile gas phase CO 2 (gas saturation more than S grmax ) on the top of the domain for the one‐cycle injection is 342 m 2 in comparison to 304 m 2 for the ten‐cycle injection. Comparing the volume affected by the CO 2 for different injection scenarios also shows that the total volume of the domain touched by the injected gas decreases with the increase in the number of cycles (4068 m 3 for one‐cycle injection compare to 3618 m for ten‐ cycle injection respectively) while the total volume containing CO 2 in mobile phase increases.…”

“…Therefore, finding applicable methods to enhance the formation storage and improve its safety and durability has motivated a series of studies. Physical processes involved in capillary trapping mechanisms have been studied and different strategies, as will be introduced in more detail later, have been proposed to enhance the amount of CO 2 that can be stored in a given formation …”

“…Injection strategies to enhance the trapping and reduce the risk of leakage have been proposed; these include, for example, gas injection at the bottom of the aquifer to increase the interaction between the gas and the ambient fluid and adding nanoparticles to injected CO 2 in order to increase the density gradient between the injected and the ambient fluid . Using numerical simulations, Leonenko and Keith and Hassanzade et al .…”

“…Physical processes involved in capillary trapping mechanisms have been studied and different strategies, as will be introduced in more detail later, have been proposed to enhance the amount of CO 2 that can be stored in a given formation. [2][3][4][5][6] Permeability heterogeneity is a critical factor influencing CO 2 migration and trapping in saline aquifers. The effect of permeability heterogeneity on the transport and trapping behaviors of CO 2 has been studied since about a decade ago.…”

“…Injection strategies to enhance the trapping and reduce the risk of leakage have been proposed; these include, for example, gas injection at the bottom of the aquifer to increase the interaction between the gas and the ambient fluid 2 and adding nanoparticles to injected CO 2 in order to increase the density gradient between the injected and the ambient fluid. 3 Using numerical simulations, Leonenko and Keith 4 and Hassanzade et al 5 showed that injecting brine on top of the injected CO 2 will increase solubility trapping. Hassanzade et al 5 also suggested that horizontal injection wells can expand the phases interface and consequently the dissolution trapping in saline aquifers.…”