An Enhanced Synergistic Effect in Surfactant-Polymer Flooding Under High-Temperature and High-Salinity Conditions

Abstract

AbstractTwo hydrophobically associating polyacrylamide (HAPAM) polymers were synthesized through free-radical micellar polymerization using different hydrophobic monomers. One polymer product – HAPAM-1 contains a linear alkyl chain, and the other one HAPAM-2 bears an aromatic group which is more compact comparing the alkyl hydrocarbons. The properties of both polymer solutions were investigated in high-salinity water (HSW). The interaction between the polymers and a non-ionic surfactant – dodecyl glucopyranoside (DDG) was studied in the HSW at 50 °C using formulations composed of 2 g/L polymer and a series of DDG concentrations. The polymer solutions exhibited a Newtonian plateau at lower shear rates followed by a significant shear-thinning region at higher shear rates. HAPAM-1 exhibited a more pronounced shear-thinning effect than HAPAM-2 due to more rigid hydrophobic junctions self-assembled by the aromatic groups. Upon addition of DDG, the zero-shear viscosities of polymer solutions were found to peak at 15 mg/L of DDG concentration to both polymer solutions. The interfacial tension (IFT) between oil and water obtained from HAPAM-2/DDG solution was lower than that of the DDG solution without polymer, suggesting a synergistic effect between HAPAM-2 and DDG which further reduced IFT. However, the IFT of DDG solution was not affected in the presence of HAPAM-1. Micromodel experiments indicated that the oil production efficiency by initial HSW injection was quite low, then displacement of residual oil was dramatically improved by injection of HAPAM-1/DDG or HAPAM-2/DDG solution. Extended HSW flooding slightly increased the oil production for both chemical flooding systems. The performance of HAPAM-2/DDG in oil displacement was better than HAPAM-1/DDG, which could be attributed to the higher solution viscosity and lower IFT resulting from more pronounced interaction between HAPAM-2 and DDG. This study aims at probing the effect of different types of hydrophobic units on surfactant-polymer interaction and correlating such interaction with the effectiveness on improving oil production by oil displacement in a porous media.