Reza Azin

CO2 miscible injection method combined with surfactants and silica nanoparticles was studied to investigate the effect of these additives on CO2 mass transfer parameters to the light oil, including diffusion coefficient, mass transfer coefficient and solubility. Silica nanoparticles with controlled size distribution were synthesized in isooctane/1- hexanol/CTAB/ammonium hydroxide, a highly-stable reverse micellar system with wo=5. The presence of Si-O-Si and Si-O-H bonds in FTIR spectra of the system revealed that silica nanoparticles are formed by partial hydrolysis of TEOS. Results of DLS indicated that the average size and size distribution of the synthesized nanoparticles were 27.6 nm and 13-76 nm, respectively. Diffusion tests were carried out using CO2 gas and three liquid systems: isooctane/ 1-hexanol, isooctane/1-hexanol/CTAB reverse micellar system without nanoparticles, and isooctane/1-hexanol/CTAB reverse micellar system with nanoparticles. Results of modeling and optimization of the gas-liquid systems under nonequilibrium interface condition, using pressure decay data show that the presence of surfactants and nanoparticles leads to decreased gas diffusion coefficient; while increased interface mass transfer resistance due to presence of aqueous droplets and nanoparticles as well as lower solubility of CO2 in the light oil are the results of applying these additives, which limits their application. The obtained CO2 diffusion coefficients for isooctane/1-hexanol, reverse micellar system without nanoparticles, and reverse micellar system with nanoparticles are 8.5550×10?8, 8.2216×10?8, and 8.1114×10?8 m2/s, respectively.