Objective During the implementation of chemical flooding, the adsorption and retention of the reservoir on the displacing agent was a major reason for the concentration loss of surfactants entering the reservoir. In order to reduce the loss cost of oil displacement fluid in the formation, the research on the adsorption inhibitor of oil displacement fluid is carried out.

Methods A adsorption inhibitor OHCB for oil displacement fluids was synthesized by the nucleophilic addition principle based on the raw materials of dicyanodiamide (DCD) and 1-octadecylamine hydrochloride (OHC) using fusion method at 150 ℃. This surfactant had strong hydrophobic groups, strong polar atoms and cationic groups, and had the ability to occupy the adsorption sites on the clay mineral surface. The structure characterization was carried out by infrared absorption, ultraviolet absorption, elemental analysis, mass spectrometry, etc. The optimum ratio was studied by static adsorption method for using it as an additive, and the adsorption inhibition effects of the optimal ratio on the oil displacement agent AEO7 were verified, as well as the static oil washing efficiency, emulsification and wetting properties of the system were compared with the single AEO7 system.

Results The results showed that OHCB had better inhibition effect on the adsorption of oil displacement agent AEO7 on clay mineral surface. The inhibition effect reached more than 27% when the mass ratio of oil displacement agent to adsorption inhibitor was 5∶1.

Conclusions The addition of OHCB not only has a good adsorption inhibition effect, but also improves the static oil washing efficiency of AEO7 to 27.3%, reduces γ_cmc to 27.1 mV/m, reduces cmc to 38 mg/L, and reduces the oil-water interfacial tension to below 0.5 mV/m. It has a synergistic effect on the system performance. Comparing with sacrificial agents requiring pre-adsorption, the method is more convenient.