Study on Microscopic Displacement Characteristics of Foam Flooding in Extra-low Permeability Reservoirs Real Sandstone Model

Abstract

Due to poor physical properties, high percolation resistance and natural micro fractures, 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. Foam flooding has both plugging capacity and surfactant properties, which can effectively increase oil displacement efficiency while expanding the sweep volume. The micro displacement mechanism of foam flooding in ultra-low permeability reservoirs and the improvement of oil displacement efficiency still need further studies. In this study, Changqing oilfield extra-low permeability reservoir cores were selected to make a real sandstone model, and researches of microscopic displacement characteristics of foam flooding have been conducted. The results indicate that: (1) Because foams have selective plugging effect in the pores, the displacement effect of foam flooding is better than that of surfactant agent which has the same apparent viscosity (2) foam injection timing has little effect on the oil displacement efficiency (3) when the water pressure is maintained at the same pressure after foam flooding, the oil displacement efficiency can be increased by 2.56–27.69%, and the main contribution comes from the large reduction of cluster residual oil and membrane residual oil (4) increasing injection pressure in later stage of foam flooding can further improve the oil displacement efficiency.KeywordsExtra-low permeability reservoirsFoam floodingMicroscopic displacementReal sandstone model