In view of the typical heterogeneous block of Daqing Oilfield，core displacement experiments are carried out and study on laboratory physical simulation of surfactant/polymer-alternating-nitrogen foam flooding has been introduced by using positive rhythm heterogeneous artificial core. The injection parameters of the system are optimized and the feasibility of improving oil recovery for low interfacial tension surfactant/polymer-alternating-nitrogen foam flooding is discussed. The experimental results show that when the total injection of the oil displacement systems is kept as a fixed value, the enhancement in oil recovery is different under the condition of the same water flooding recovery with changing of the alternating way of low interfacial tension surfactant/polymer and nitrogen foam. The injection pattern of injecting 0.05 PV foam base fluid+0.05 PV N ²⁺0.10 PV low interfacial tension surfactant/polymer in a single cycle with 0.20 PV cyclic injection volume and 3 alternating rounds is the optimal injection pattern. And the stage recovery is the highest under this injection pattern, which can further improve oil recovery by about 21.82% based on water flooding.

Principle of litho electric experiment and threedimensional physical simulation system were used to research the swept law of binary. By the pressure recorder and resistivity measuring probe installed on the model, the change of the pressure and saturation in the model was accurately measured and swept law of the binary compound flooding system was evaluated. The results showed that the swept volume of low permeability layer was expanded by the binary system, and the sweep efficiency of the model was also improved. After binary flooding, the unswept areas mainly concentrated on both sides of the mainstream line in the layer of low and middle permeability, and there is unswept areas shunt online between the production wells because of the influence of border and injectionproduction well.

Scaling phenomenon widely existing in the process of base ASP flooding will affected subsequent water flooding and lifting system adversely. The scale composition change and types in the lifting system and formation were studied and the scale statistics from lifting system, casting thin sections, SEM and electron probe analysis were used to determine the base ASP flooding. The results showed that the main scale types changed with the PV injection of base ASP flooding. In early injection stage, the scale was mainly carbonate scale containing a small amount of silica scale and organic matter. In the middle injection stage, the number component of three scales was same. In later injection stage, the scale was the same with early injection stage. Casting thinsection analysis showed that the scale form was “white clouds” and “brown cementation”. With part of the pores blocking, surface pore rate fell by 6.45% on average. The types of scale formation in the study area were mainly calcium scale and silicon scale, containing a small amount of barium/titanium scale and iron scale. Due to alkali dissolution, scaling phenomenon in formation and wellbore appeared frequently, so it was suggested that base ASP flooding should be replaced wit weak ASP flooding if it can achieve the same improving recovery rate.