Effect of Nanoparticles on Flow Alteration During CO2 Injection

Abstract Surface-treated nanoparticles have been shown to stabilize CO2-in-water foam by adhering to the surface of CO2 bubbles and preventing their coalescence. However, to bring the nanoparticles from the bulk phase to CO2/water interface requires an input of mechanical energy. Co-injection of CO2 and an aqueous dispersion of nanoparticles at high rates is known to provide sufficient energy. However, this co-injection is less favorable because of the operational constraint, i.e., injectivity reduction. Here, we show that beneficial effect of nanoparticles, manifested as improved sweep efficiency, occurs even at low shear rates in a drainage displacement. We inject high-pressure liquid CO2 into sandstone cores initially saturated with brine containing suspended nanoparticles and compare the results with the case with no nanoparticle addition. The water saturation distribution was measured using CT scanning techniques. The results show that the nanoparticles increase sweep efficiency and reduce the gravity override compared to displacements without nanoparticles. The new mechanism described here provides a promising alternative for mobility control in CO2 floods.