Diffusion Coefficient and Interfacial Tension with Addition of Silica Nanoparticles in CO_2-Surfactant-Water-Hexane for Enhanced Oil Recovery (EOR) Using Molecular Dynamic Simulation

摘要

Dynamic simulation for investigating the interactions of molecules that involved carbon dioxide (CO_2), sodium dodecyl sulfate (SDS), water (H_2O), hexane and silica nanoparticles (SiO_2) in terms of diffusion coefficient and interfacial tension (IFT) were conducted at 298 K and 383 K for three different systems which consists of three layers (L1-L2-L3); CO_2-water-water/hexane (S1), CO_2-water/SDS-water/hexane (S2) and CO_2-water/SDS/SiO_2-water/hexane (S3). Analyses of the mean square displacement (MSD) showed that higher curve definition was obtained at 383 K than 298 K system, indicates higher mobility of the molecules. The diffusion coefficient of all CO_2, SiO_2, SDS and hexane molecules in all systems were higher at 383 K than 298 K due to heat supplied that energized the molecules and enhanced their diffusivity at the elevated temperature. The IFT between L1-L2 (I1) and L2-L3 (12) determined from the pressure tensor data, decreased from 36.3 to 16.13 mN/m and 42.3 5 to 6.45 mN/m, respectively for S1 with the increment of temperature. Addition of SDS surfactant further decreased the I1 and 12 from 25.67 to 11.83 mN/m and 29.95 to 9.46 mN/m, respectively for S2 when the temperature increased. The IFT reduced significantly from 25.67 to 0.57 mN/m and 29.95 to 1.13 mN/m for I1 and 12, respectively at 298 K with addition of SiO_2 into SDS-Water i.e. S3. The addition of SiO_2 and SDS further reduced the interfacial tension due to the part taken by SiO_2 and SDS in disrupting the closely linked hydrogen bond between water molecules at the interphase.