Abstract: Three surfactants were selected: sodium dodecyl sulfate (SDS), cetrimonium bromide (CTMAB), and polyglycerol fatty acid ester (PGFE) for evaluation of oil rheology, interfacial tension and oil-displacement effect on Liaohe crude oil. The molecular simulation was used to explore the oil-displacement of surfactants in multi-systems. The results showed that: (1) The order in which surfactants improved the rheological properties of crude oil from high to low is SDS>PGFE>CTMAB; (2) When the mass fraction of surfactant added was 0.3%, SDS had the lowest interfacial tension of 1.03×〖10〗^(-2)mN/ m, and the oil-displacement efficiency was as high as 87.3%; (3) The order of density reduction ability in molecular simulation was: CTMAB<PGFE<SDS; (4)The radial distribution function (r)of each crude oil system showed that the highest peaks of the four crude oil systems were at r=0.12nm, compared with the peak of the blank crude oil system of 11.432 nm. The highest peaks of the CTMAB system, PGFE system and SDS system were 10.084, 9.902 and 8.047 nm, respectively. The lower the position of peak r, the weaker the interaction between crude oil and rock. SDS had the best oil-displacement performance. The simulation results were in agreement with the experimental results, explaining the mechanism of oil-displacement by surfactant.

Key words: surfactant, rheological characteristic, interfacial tension, oil displacement effect, molecular dynamics