Foamability and stability of anionic surfactant-anionic polymer solutions: Influence of ionic strength, polymer concentration, and molecular weight

Abstract

A systematic experimental approach was initiated to optimize properties of a polymer enhanced foam (PEF) system using anionic surfactant (i.e., AOS) and anionic polymer (i.e., SAV10 MPM) in high salinity conditions. First, the bulk foam properties of AOS surfactant solutions as a function of AOS concentration and salinity were evaluated. The result indicated that Ca2+ ions increased the AOS foamability and foam stability more than Mg2+ ions within the solubility limit, where only the divalent ionic strength (Mg2+/Ca2+) ratio varied within brine composition. Second, the effect of SAV10 MPM concentration and different molecular weights of this polymer on AOS foamability and foam stability were investigated in modified synthetic seawater (MSSW1). We found that the AOS foamability and foam stability improved by SAV10 MPM addition but it's highly dependent on the polymer concentration. The AOS foamability and foam stability were boosted when the polymer concentration was below the critical overlap concentration (c*) in comparison to AOS without polymer. However, above polymer c*, the polymer tends to exhibit antifoam characteristics due to the hydrophobic nature of the polymer. Hence, to enhance anionic-anionic PEF systems, one should inhibit the hydrophobic interaction by maintaining the polymer concentration below c*. Thus, we recommend a low concentration of sulfonated polymer (i.e., SAV10 series, below c*) to enhance the AOS foamability and foam stability in a high salinity environment regardless of viscosity and molecular weight.