Effect of brine salinity and hydrolyzed polyacrylamide concentration on the Oil/Brine and Brine/Rock Interactions: Implications on enhanced oil recovery by hybrid low salinity polymer flooding in sandstones

The main idea behind the application of Low salinity polymer flooding (LSPF) enhanced oil recovery (EOR) method is that diluted brine improves the oil recovery by wettability alteration from oil-wet (OW) towards water-wet (WW) condition, while polymer enhances the mobility of the displacing phase. However the possible effect of polymer on the fluid/fluid and fluid/rock interactions are not investigated systematically in the literature. The main objective of the present reserach is to examine the possible effect of hybrid application of low-salinity and polymer on the brine/rock and brine/oil interfaces properties. Formation water (FW) and sea water (SW) and its two different dilutions, i.e. twice concentrated (2xcSW) and 10 times diluted (10xdSW) along with different concentrations of HPAM as polymer, i.e. 250, 500, 1000 and 2000 ppm, are considered. Silicate substrates are used as representative of the main mineral in sandstone rocks and both WW and OW conditions evaluated. To understand the dominant oil/brine and rock/brine interactions, different properties such as brines pH, oil/brine interfacial tension, oil/brine zeta potential, rock/brine zeta potential and oil contact angle on the rock surface (in the presence of the desired aqueous sample) are investigated. Experimental results are in line with each other and confirm the influence of both aqueous salinity and polymer concentrations on all the measured properties i.e. IFT, wettability and zeta potentials. Fluid/fluid and rock/fluid interactions are proposed for justification of the observed experimental results. The results can be used to shed lights on the possible recovery mechanisms and designing of successful hybrid low salinity polymer flooding.