Enhanced oil recovery with a thermo-thickening viscoelastic surfactant: A comparison with polymer

High-molecular-weight partially hydrolyzed polyacrylamide (HPAM) has extensively used in enhanced oil recovery (EOR) process; however, it suffers from poor injectivity into low-permeability oil reservoirs and compromised long-term thermal stability under reservoir conditions. To address these challenges, a viscoelastic surfactant, 3-(N-erucamidopropyl-N,N-dimethyl ammonium) betaine (EDAB), was developed and systematically compared with HPAM. Experimental results demonstrate that EDAB outperforms HPAM in thermal resilience, salt tolerance, and interfacial activity. Unlike HPAM's thermal thinning behavior, EDAB displays thermo-thickening properties, with viscosity rising from 225 to 366 mPa·s as temperature increases from 25 to 55 ℃. EDAB maintains 100% viscosity retention under 80 mg·L⁻¹ Ca²⁺ or Mg²⁺, whereas HPAM experiences 46% viscosity loss under identical ionic conditions. Core-flooding tests conducted under simulated Daqing oil reservoir conditions indicate that EDAB achieves a 1.4% higher incremental oil recovery factor than HPAM with equal initial solution concentration. When HPAM was employed as a mobility control for pre- or post-flush, EDAB elevates the recovery factor by 13.9% over water flooding. These comparative analyses underscore the potential of EDAB as a thermally stable, salt-insensitive alternative to HPAM, offering an optimized chemical strategy for EOR in challenging reservoir environments. The findings provide empirical validation for surfactant-based solutions to address HPAM's operational constraints in low-permeability formations.