Ultra-low interfacial tension (IFT) zwitterionic surfactant for imbibition enhanced oil recovery (IEOR) in tight reservoirs

Abstract

Surfactants are effective for imbibition enhanced oil recovery (IEOR) in tight sandstone reservoirs because of their ability to change rock wettability and reduce oil–water interfacial tension (IFT). Different surfactants have different IEOR, and some surfactants even have a negative effect on IEOR. Thus, the selection of an optimum surfactant is necessary for IEOR aiming at different reservoirs. In this study, the static imbibition efficiencies of different surfactants at 50℃ and 2 % KCl were systematically studied by Amott imbibition flask. The imbibition mechanisms and influence factors including salinity and temperature were then investigated by IFT, contact angle (CA), Zeta potential and adhesion energy. The results showed that the zwitterionic surfactant of erucic acid amide propyl betaine (EAPB) could significantly reduce the IFT to ultra-low values (5.7 × 10-4 mN/m) and alter the wettability of sandstone surface at 50℃. The fluidity of oil and capillary force could be effectively improved and the adhesion energy could be reduced, which enabling more pore throats to participate in the imbibition production process. It could be found that the core hydrophilic and IEOR increased with the reduction of IFT. The IEOR of 0.1 % EAPB system reached 44.57 %. The high IEOR and rate can be achieved under the condition of low salinity, high temperature. The IEOR of 0.1 % EAPB was 47.59 % at 2000 mg/L salinity, and 46.61 % at 60℃. This work provides fundamentals for the selection and design of IEOR surfactant in tight oil reservoirs.