Competitive Adsorption‐Mediated Preservation of Effective Polymer Concentration in a Hydrophobically Associating Water‐Soluble Polymer/Sodium Dodecyl Sulfate Hybrid System for Mobility Control and Enhanced Heavy Oil Recovery

Abstract

Conventional polymer flooding of medium‐to‐high‐viscosity heavy oil can be limited by near‐wellbore shear degradation and polymer retention, which impair injectivity and mobility control. Here, a hydrophobically associating water‐soluble polymer (HAWP)/sodium dodecyl sulfate (SDS) hybrid system was evaluated at 65°C using fixed‐shear‐rate rheology, interfacial tension, adsorption/migration, and core‐flooding measurements. The bulk viscosity exhibited a maximum at 250 mg/L SDS; at 1750 mg/L HAWP, the peak viscosity was 1752 mPa·s, corresponding to a 255.7% increase relative to the SDS‐free HAWP solution measured under identical conditions. During dynamic sand‐pack transport, formulations containing at least 300 mg/L SDS limited the HAWP concentration reduction to no more than 3.7%, and core floods increased oil recovery by 7.4 and 7.5 percentage points for 112 and 634 mPa·s heavy oils, respectively. These results indicate that SDS can improve injectivity and preserve effective polymer concentration by reducing HAWP adsorption loss, providing a mobility‐control route for heavy‐oil reservoirs.