Wettability alteration of carbonate rocks from strongly liquid-wetting to strongly gas-wetting by fluorine-doped silica coated by fluorosilane

Wettability alteration is an important mechanism to increase recovery from oil and gas reservoirs. In this study, effect of fluorine-doped silica coated by fluorosilane nanofluid on wettability alteration of carbonate rock was investigated. The nanoparticle synthesized by sol-gel method was characterized using XRD, FTIR, SEM, and DLS. Adsorption of nanoparticle on rock was characterized by FESEM, and composition of rock after treatment was determined by EDXA. Effect of nanofluid on wettability was investigated by measuring static, advancing, and receding contact angle and surface free energy, imbibition of water, crude oil, and condensate of untreated and treated carbonate rock. Also, stability of contact angle and thermal stability of nanofluid were studied. ‎Results show that contact angles for water, condensate, and crude oil were altered from 37.95°, 0°, ‎and 0° to 146.47°, 145.59°, and 138.24°. In addition, water, condensate, and oil imbibition ‎decreased more than 87, 88, and 80%, indicating that wettability was altered from strongly oil wet, ‎condensate wet, and water wet to strongly gas wet. The ultraoleophobic and ultrahydrophobic stability were >48 hours and 120 minutes. Surface free energy of treated rock for water, crude oil, and condensate was ‎2.24, 1.17, and 1.47mN/m. Thermal stability of nanofluids and adsorbed nanoparticle was up to 150°C.