Numerical Simulation Study on Enhanced Efficiency of Geological CO2 Storage with Nanoparticle

Abstract

Abstract Carbon dioxide (CO2) geological storage has a large potential to achieve a net-zero target of CO2 emissions. CO2 injected into the storage formation typically becomes a super-critical state under the underground temperature and pressure conditions. The injected super-critical CO2 (scCO2) tends to migrate upwards within the reservoir due to its lower density compared to the formation brine even though the density of scCO2 is quite higher than that of gaseous phase CO2. Moreover, injected CO2 is affected by not only the gravity segregation but also the viscous fingering. These phenomena are expected to cause poor storage efficiency in carbon storage projects. In this study, we investigated the potential of adding common metal oxide nanoparticles to scCO2 to improve the storage efficiency utilizing the properties of scCO2 as a solvent under subsurface conditions. This paper presents the pseudo-fluid modeling of scCO2 containing nanoparticles and the results of numerical simulation considering the effects of nanoparticle types and concentrations on the CO2 storage efficiency. In particular, the effect of density alteration on CO2 storage efficiency was investigated in this study. Some pseudo-fluid models of scCO2 containing four types of nanoparticles, such as aluminum oxide, silicon dioxide, titanium oxide, and zinc oxide with different concentration were created, respectively. Furthermore, numerical simulations of scCO2 injection with and without nanoparticles were performed using a two-dimensional radially symmetric model. The results from this work showed the migration of CO2 to the upper part of the formation was suppressed and the storage of CO2 in the lower part of the formation was promoted when scCO2 was injected with nanoparticles. Furthermore, CO2 breakthrough time was delayed several months or years and total breakthrough quantities were also decreased as the density and concentration of nanoparticles in scCO2 became higher in the case of installing an imaginary production well for pressure control. These results suggest that the injection of nanoparticle-dispersed CO2 improves the storage efficiency of CO2 geological storage compared to the injection of CO2 alone. Furthermore, this study showed that the concept has possibility of improving the safety of CO2 geological storage, which may play an important role when considering the long-term CO2 sequestration as well.