Stable Silica Nanofluids of an Oilfield Polymer for Enhanced CO ₂ Absorption for Oilfield Applications

CO ₂ injected with water often gives premature breakthrough and reduces its absorption during sequestration and oil recovery applications. Water-soluble polymers are used to increase CO ₂ absorption via an increase in water viscosity that restricts CO ₂ movement and thus its early release. The efficacy of polymer CO ₂ absorption methods can be further increased in the presence of nanoparticles (NPs) that interact with polymer chains and create a steric barrier to improve CO ₂ absorption. Thus, nanofluids prepared with compatible NPs might be a safe and reliable method to improve CO ₂ 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 CO ₂ absorption and compared with the one of PAM fluid at different temperatures (303 and 353 K). The inclusion of SiO ₂ in PAM fluid provided stable nanofluids that exhibited good dispersion stability without NP settlement for days. Thus, the efficacy of PAM fluid CO ₂ 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 CO ₂ absorption in nanofluids, mainly due to enhanced NP aggregation; thus, the use of nanofluids for CO ₂ absorption is critical at high temperature and high NP concentration. The NP effect on CO ₂ stabilization and absorption is finally supported through UV-vis measurements. The study highlighted important aspects of CO ₂ absorption and is a forward step toward the use of nanofluid together with the considerable possibility of enhanced CO ₂ miscible oil recovery.