Performance Evaluation of Lipopeptide-Enhanced Petroleum Sulfonate Binary Flooding System

To address the rapid interfacial activity decay and high adsorption loss of conventional chemical flooding under harsh reservoir conditions, this study developed an alkali-free biochemical binary composite system by partially substituting petroleum sulfonate with the biosurfactant lipopeptide (0.15 wt % petroleum sulfonate + 0.15 wt % lipopeptide + 1400 mg/L HPAM). Systematic thermal aging, emulsification, dynamic antiadsorption, and core flooding evaluations revealed distinct performance enhancements over the conventional chemical binary system. After 60 days of aging at 45-65 °C, the composite system sustained interfacial tension within the ultralow regime (10^-2 mN/m) and exhibited a 20-28 percentage points higher viscosity retention rate, along with a counterintuitive decrease in equilibrium interfacial tension at elevated temperatures. In multicycle dynamic sand contact tests at 55 °C, competitive adsorption and steric/electrostatic shielding by lipopeptides prolonged the antiadsorption lifespan by an additional cycle. In physical core displacement experiments, the biochemical system achieved an incremental oil recovery of 6.1 percentage points over the conventional counterpart. These findings demonstrate that "structural and electrical complementarity" between biosurfactants and synthetic surfactants provides an effective, alkali-free route for chemical flooding in heavy oil reservoirs.