Stable Silica Nanofluids of an Oilfield Polymer for Enhanced CO2 Absorption for Oilfield Applications

CO2 injected with water often gives premature breakthrough and reduces its absorption during sequestration and oil recovery applications. Water-soluble polymers are used to increase CO2 absorption via an increase in water viscosity that restricts CO2 movement and thus its early release. The efficacy of polymer CO2 absorption methods can be further increased in the presence of nanoparticles (NPs) that interact with polymer chains and create a steric barrier to improve CO2 absorption. Thus, nanofluids prepared with compatible NPs might be a safe and reliable method to improve CO2 absorption of polymer methods. In this work, a nanofluid prepared with silica NPs (0.1-1.0 wt %) in base fluid of oilfield polymer [(polyacrylamide (PAM) with typical oilfield concentration (1000 ppm)] was tested for CO2 absorption and compared with the one of PAM fluid at different temperatures (303 and 353 K). The inclusion of SiO2 in PAM fluid provided stable nanofluids that exhibited good dispersion stability without NP settlement for days. Thus, the efficacy of PAM fluid CO2 absorption significantly increased with nanofluids as reported through microscopic, kinetics, and molality results. The increase in NP concentration and temperature (353 K) showed an inverse relationship with CO2 absorption in nanofluids, mainly due to enhanced NP aggregation; thus, the use of nanofluids for CO2 absorption is critical at high temperature and high NP concentration. The NP effect on CO2 stabilization and absorption is finally supported through UV-vis measurements. The study highlighted important aspects of CO2 absorption and is a forward step toward the use of nanofluid together with the considerable possibility of enhanced CO2 miscible oil recovery.