Rheological properties of super critical CO2 with Al2O3: Material type, size and temperature effect

Abstract

CO2 liquid is applied as an Enhanced Oil Recovery (EOR) method in oil reservoirs to increase the displacement efficiency. Because of the high temperature and pressure in the reservoirs, the viscosity of the CO2 decreases leading to poor macroscopic sweep efficiency. We study the effect of morphology of aluminum oxide nanoparticle (Al2O3 NP) on the rheological properties of super critical (SC)-CO2 such as viscosity and self-diffusion coefficient using molecular dynamic (MD). We investigate these properties in detail for relevant temperature (350, 380, and 410) K, pressure, 200 bar, and spherical diameter (1.0, 2.0, and 3.0 nm) at 1% volume fraction. Molecular dynamic (MD) simulates Al2O3 SC-CO2 nanofluid by using two force fields such as condensed-phase molecular potentials for atomistic simulation studies (COMPASS) and Charge optimization many body (COMB). The results show that the viscosity of the nanofluid has a direct proportional to temperature and reversely proportional to NP size. Moreover, NP-based material and NP shape exhibit significant effect of enhancement in the nanofluid viscosity in comparison with the cylindrical CuO NP in our previous study. The relative viscosity is enhanced almost 3.6 times for smallest NP at 380 K. Also, implementing 1.0 nm Al2O3 SC-CO2 nanofluid improves the relative viscosity from 1.94 to 3.59 and then to 3.67 by increasing temperature from 350 to 380 to 410 K.