Research and Development of Asymmetric Amphoteric Gemini Surfactants and Oil Displacement in Low Permeability Reservoirs

Asymmetric amphoteric Gemini surfactants (PAHC and PAOC) were synthesized from cashew phenol, epichlorohydrin, dimethyl tertiary amine vis etherification and quaternization reactions. The structures were determined by FTIR and 1 H NMR. The prepared asymmetric amphoteric Gemini surfactants, sodium salicylate, and potassium chloride were optimized to obtain the systems PSP‐C 16 and PSP‐C 18 . The experimental results showed that the two systems can reduce the interfacial tension to 2.37 × 10 −2 and 1.81 × 10 −2 mN/m, respectively, so that the crude oil can better break off from the rock. With the increase of system concentration, the adsorption capacity increased first and then changed little. The maximum splitting times of PSP‐C 16 and PSP‐C 18 at a concentration of 0.5 wt% were 540 and 585 s, respectively, resulting in good emulsification properties. PSP‐C 16 can reduce the oil‐contact antenna from 98.3° to 15.6°, and PSP‐C 18 can reduce the oil‐contact antenna from 96.4° to 14.3°, leading to good wettability transition. The single core flooding test results showed that the average enhanced oil recovery of the two systems was 9.42% and 10.21%, respectively, and the double core flooding test results showed that the average enhanced oil recovery of the two systems was 10.56% and 12.34%.