Study on the synergistic phenomenon of oil–water–solid interface in high mineralization co-produced water system based on chelating agent mixed surfactant

This study investigates the synergistic effects of chelating agents and surfactants in high-salinity co-produced water coproduced water. The scale inhibition efficiency, wettability alterations, and interfacial modification capabilities of various surfactants and chelating agents were assessed by individually incorporating them into high-salinity co-produced water. Results indicated that the Sodium isomeric 13-alcohol polyoxyethylene ether sulfonate itaconic acid ester (GTOS), demonstrated superior performance compared to other surfactants. At a concentration of 0.3%, GTOS reduced the oil–water interfacial tension to 10⁻2 mN/m and markedly altered rock wettability. Among the chelating agents, N, N-diacetic acid (GLDA) effectively neutralizes metal ions on the rock surface due to its stability. At a 1% concentration, GLDA achieved a scale inhibition rate of 98% and also has the potential to modify rock wettability and slightly acidify it. The combination of GLDA (1%) and GTOS (0.3%) is more effective at reducing oil–water interfacial tension and modifying rock wettability in high-salinity co-produced water compared to their application. Furthermore, advanced microscopic techniques, including molecular chemistry, mechanics, and electrochemistry, were employed to analyze variations in crude oil bonding, rock surface roughness, and charge adsorption. This analysis provided insights into the synergistic effects of these agents. Results demonstrate that micro characterization techniques confirmed the significant removal of the oil film from the rock surface following treatment with the composite system. Spontaneous seepage experiments indicated that the composite system increased crude oil self-absorption recovery in the rock by 36%, thus validating the formulation's effectiveness. Notably, our formulation utilizes lower concentrations than those employed in previous studies, making it more cost-effective for field applications. This study provides the first comprehensive insight into the synergistic mechanisms of chelating agents and surfactants through macro- and micro-analysis. These findings offer valuable guidance for enhancing recovery in low-permeability and high-salinity formations and introduce novel technical approaches for field development.