Abstract: According to the orthogonal design experiment, the best microemulsion system was selected. The natural rock core displacement tests were conducted to verify the improvement of oil recovery by microemulsion techniques. The lithographic glass model was used to conduct the visualization test of the remaining oil micro-displacement process and its mechanism. The results showed that compared with water flooding, when the permeability of rock core increases from 1.78×10-3μm2 to 29.11×10-3μm2, the enhanced oil recovery (EOR) by microemulsion is from 5.45 percentages to 12.14 percentages, which is consistent with the results of lithographic glass model tests. The five micro-residual oil types are observed: cluster type, column type, blind-end, droplets type, and oil film type. Among them, the flooding proportions of the cluster and droplet residual oil are the highest, the displacement effect is better, and the oil film residual oil is the lowest, and the displacement effect is poor.

Key words: microemulsion flooding, lithography glass model, remaining oil type, oil displacement mechanism, remaining oil recovery