Carbonated polymeric nanofluids for enhanced oil recovery from sandstone reservoir

Polymeric nanoparticle (NP) suspensions are colloidal suspensions where NPs (size <= 100 nm) are suspended in the polymer-enhanced base fluid, mainly water. Compared to water or sole polymer solutions, they exhibit superior rheological, mass transfer, and heat tolerance attributes. While the use of polymeric NP suspensions as injection fluids for enhanced oil recovery has been explored in past studies, their use as carrier fluids for CO2-loaded (carbonated) water injection has not been explored to date. Thus, this study explores the use of polymeric NP suspensions prepared using SiO2, ZnO, and TiO2 nanoparticles of varying concentration for CO2 loading and their use as carbonated fluids for enhanced oil recovery from sand-packs mimicking a sandstone reservoir. It was observed that the use of nanoparticles improved CO2 absorption in the base fluid, water by a significant margin (approximate to 8-23%). The inclusion of salt (3 wt% NaCl) induced aggregation in NP suspensions and reduced their CO2 loading capacity. When used for flooding, the carbonated polymeric NP suspensions exhibited superior oil mobilization than their non-carbonated peers resulting in more oil produced even at a higher temperature and salinity (additional 12-20% of OOIP). Increasing temperature reduced the loading (absorption) of CO2 and oil recovery effectiveness of the polymeric NP suspensions while salt majorly impacted oil recovery efficiency under the investigated conditions. Based on the results obtained in this study, the use of 0.1 wt% SiO2 NPs has been recommended as the ideal concentration for use in carbonated water injection.