Study on Microscopic Displacement Characteristics of Surfactant Flooding in Extra-Low Permeability Reservoirs Real Sandstone Model

Due to poor physical properties, high percolation resistance and natural micro fractures, the primary water flooding recovery of Changqing oilfield extra-low permeability reservoirs is only 20.3%. Especially when the reservoir enters the rapid water cut increase development stage, the oil production rate is greatly reduced, and it is difficult to produce the remaining oil by using conventional technology. Surfactant flooding has good injection performance, and the combination of surfactant flooding and profile control technology can effectively improve the displacement efficiency while enlarging the sweep volume. There are differences in micro flooding mechanism between surfactant flooding and conventional water flooding in ultra-low permeability reservoir. In this paper, the inspection well cores of Changqing extra low permeability reservoirs were selected to make a real sandstone model, and the micro displacement characteristics of surfactant flooding have been studied. The results show that: 1. The percolation characteristics of water driving oil in pores during surfactant flooding are mainly uniform displacement. 2. Surfactant flooding is mainly used to strip oil through emulsification. For the small pores that the displacement fluid can’t enter, the residual oil can’t be displaced, and the ability to improve the sweep efficiency is limited. 3. Compared to water flooding, surfactant flooding has higher displacement efficiency, which can increase the displacement efficiency by 2.86–14.29%, which is 50–70%. The residual oil of the model after surfactant flooding can’t enter is 22–35%.