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Naturally fractured carbonate reservoirs have very low oil recovery efficiency owing to their wettability and tightness of matrix. However, smart water can enhance oil recovery by changing the wettability of the carbonate rock surface from oilwet to water-wet, and the addition of surfactants can also change surface wettability. In the present study, the effects of a solution of modified seawater with some surfactants, namely C 12 TAB, SDS, and TritonX-100 (TX-100), on the wettability of carbonate rock were investigated through contact angle measurements. Oil recovery was studied using spontaneous imbibition tests at 25, 70, and 90 °C, followed by thermal gravity analysis to measure the amount of adsorbed material on the carbonate surface. The results indicated that Ca 2+ , Mg 2+ , and SO 4 2− ions may alter the carbonate rock wettability from oil-wet to water-wet, with further water wettability obtained at higher concentrations of the ions in modified seawater. Removal of NaCl from the imbibing fluid resulted in a reduced contact angle and significantly enhanced oil recovery. Low oil recoveries were obtained with modified seawater at 25 and 70 °C, but once the temperature was increased to 90 °C, the oil recovery in the spontaneous imbibition experiment increased dramatically. Application of smart water with C 12 TAB surfactant at 0.1 wt% changed the contact angle from 161° to 52° and enhanced oil recovery to 72%, while the presence of the anionic surfactant SDS at 0.1 wt% in the smart water increased oil recovery to 64.5%. The TGA analysis results indicated that the adsorbed materials on the carbonate surface were minimal for the solution containing seawater with C 12 TAB at 0.1 wt% (SW + CTAB (0.1 wt%)). Based on the experimental results, a mechanism was proposed for wettability alteration of carbonate rocks using smart water with SDS and C 12 TAB surfactants.

Nowadays, because of the reduction in oil resources and the passage of the first and second life period of current reservoirs, using enhanced oil recovery (EOR) methods is of great importance. In recent years, due to the developments in technology and the advent of powerful computers, using simulation methods in enhanced oil recovery processes is on the rise. The computational fluid dynamics (CFD) method, as a branch of fluid mechanics, is a suitable method for studying and simulating EOR methods. In this study, a review was done on the application of CFD studies for simulating EOR methods. Also, potentials for future studies and the challenges researchers may face in this method were mentioned. Although using this method in enhanced oil recovery processes has recently started, different areas for more studies still exist. To optimize the usage of this method in future studies, the necessity of multiphase models and solution methods development, as well as considering all microscopic parameters such as interfacial tension and viscosity in investigating oil recovery factor is of great importance.