Numerical simulation study on enhanced efficiency of carbon dioxide geological storage with nanoparticles in deep saline aquifer

Geological storage of carbon dioxide (CO2) is a promising technique to reduce large-scale greenhouse gas emissions. There are some candidates for geological storage formation while deep saline aquifers have attracted tremendous attention because they have the largest potential of all possible subsurface storage sites. CO2 injected into deep saline aquifers migrates upward until it reaches a sealing formation due to its buoyancy effect, which causes poor storage efficiency. Over the past few years, some novel research has been published to utilize nanoparticles for CO2 geological storage. The addition of nanoparticles to injecting super-critical CO2 (scCO2) changes its physical properties, such as the density and viscosity, which could mitigate gravity segregation and viscous fingering. However, the studies related to these techniques are still extremely limited, and the potential advantages or their impacts are poorly understood. In this paper, we investigated the effects of the physical properties of scCO2 containing nanoparticles on storage efficiency by using a versatile commercial simulator (CMG-GEM). In particular, the effects of nanoparticle types (aluminum oxide, silicon dioxide, titanium oxide, and zinc oxide) and concentration on CO2 storage efficiency were presented quantitatively by considering possible operation scenarios. The results showed the migration of CO2 to the upper part of the aquifer was suppressed, and the storage of CO2 in the lower part of the aquifer was promoted when scCO2 was injected with nanoparticles. It also showed some effects in delaying breakthrough time and mitigating breakthrough amount when we assumed the pressure control well. It was indicated that the cumulative breakthrough amount after 30 years was reduced by 8.2% in the minimum case and by 79.3% in the maximum case. Although the proposed method still has economic challenges, the innovation in the production processes of nanoparticles or combining with added value will lead to improving feasibility.