Wettability Alteration in Low-Permeability Sandstone Reservoirs by “SiO2-Rhamnolipid” Nanofluid

Wettability condition of rock surface is an enormous parameter for enhanced oil recovery (EOR) in low−permeability reservoirs. It determines the spreading of injected water and the adhesion of residual oil on rock surfaces. In this study, a new nanofluid composed of silica nanoparticles and rhamnolipid in brine was utilized as an effective agent to alter the wettability of rock surface. In order to obtain rock surfaces with different initial wettabilities, hexamethyl disilazane (HMDS) was used for the sample preparation. The measurement of three−phase contact angles for water/air/rock and brine/oil/rock were performed to explore the contact situation between rock surface and movable fluids, and the spontaneous imbibition test researched the process of oil recovery with nanofluid. By evaluating the experimental measurements, nanofluid showed a significant potential in wettability alteration from oil−wet toward water−wet state, which is an important mechanism for “scraping” oil drop from rock surface during...