Construction and\nProperties Evaluation of the Binary\nFlooding System Based on Lipid Peptide

To enhance crude oil recovery under complex reservoir\nconditions\nand reduce the environmental impact of the oil displacement system,\na biosurfactant lipid peptide (TH) was combined with four chemical\nsurfactants. From these combinations, those capable of achieving an\nultralow interfacial tension region (<10<sup>–2</sup> mN/m)\nwere selected. The selected surfactant mixtures were then combined\nwith polyacrylamide (HPAM) to construct a surfactant–polymer\nbinary oil displacement system. The results showed that TH/OAB(2:1),\nTH/OAB(3:1), and TH/EAO(3:1) could reduce IFT to the ultralow interfacial\ntension region. Compound surfactants are easier to form mixed micelles\nthan single surfactants, and the EACN of TH/OAB(2:1) and TH/EAO(3:1)\nis consistent with EACN<sub>Oil</sub>, which can achieve higher surface\nactivity at lower concentrations. The three compound surfactants have\na wide range of ultralow interfacial tension concentrations and excellent\nantidilution performance. TH/OAB(2:1) and TH/EAO(3:1) have better\nantiformation adsorption performance than TH/OAB(3:1), and the oil\nwashing rate of TH/OAB(2:1) is up to 80.30%. TH and OAB have spatial\ncomplementarity, which can increase the molecular packing density\nat the oil–water interface and reduce the IFT. In CaCl<sub>2</sub> and NaCl solutions, the IFT of the two binary flooding systems\nconstructed by TH/OAB(2:1) and TH/EAO(3:1) and HPAM remained in the\nultralow interfacial tension region, with excellent salt resistance.\nWhen aged in the reservoir for 90 days, the IFT slightly increased\nbut the viscosity decreased significantly. Adding a viscosity retaining\nagent (JW) was required to maintain the viscosity of the system. In\nthe simulated oil displacement experiment, the recovery improvement\nof the two binary oil displacement systems was higher than those of\nsurfactant and polymer alone. This study provides a new idea for the\nalkali-free surfactant–polymer binary oil flooding system and\nprovides theoretical support for the practical application of TH in\ntertiary oil recovery.