Polymer flooding has a large-scale promotion in Daqing oilfield, this paper prepared two-dimensional heterogeneous model according to the typical reservoir in Daqing oilfield and did the experiments of water flooding and polymer flooding with the method of three tubes parallel, monitored the oil saturation distribution in the process of displacement timely by using the advanced saturation monitoring method. The results show that, the recovery rate was 30.35% in the water flooding stage and improve the degree of recovery to 8.28% in the polymer flooding stage. The mainstream channels in the high permeability layer was formed and occurred the phenomenon of fingering in each layers after water flooding, the remaining oil is mainly distributed in the medium and low permeability layer. The polymer advanced to the high permeability layer and increased the injection pressure and the amount of liquid absorption of the medium and low permeability layer after polymer injection, the distribution of remaining oil mainly in low permeability layer after polymer flooding.

CO2 miscible flooding is an important technology for enhancing oil recovery and greenhouse gas storage in the world. As a tertiary recovery technology, it is usually applied after water flooding. Therefore, the actual reservoirs usually contain a lot of injected water in addition to connate water. The salinity of these formation waters varies from place to place. CO2 is an acid gas. After it is injected into the reservoir, it easily reacts with formation water and rock and affects the physical properties of the reservoir. However, no research results have been reported whether this reaction affects the minimum miscibility pressure (MMP) of CO2-crude oil, a key parameter determining miscible flooding in formation water. Based on CO2-formation water–rock interaction experiments, this paper uses the core flooding method to measure the CO2-crude oil MMP under different salinity in formation water. Results show that CO2 causes a formation water pH decrease from 7.4 to 6.5 due to its dissolution in formation water. At the same time, CO2 reacts with formation water, albite, potassium feldspar, and carbonate minerals in the cores to generate silicate and carbonate precipitates, which could migrate to the pore throat together with the released clay particles. Overall, CO2 increased core porosity by 5.63% and reduced core permeability by 7.43%. In addition, when the salinity of formation water in cores was 0, 4,767, and 6,778 mg/L, the MMP of CO2-crude oil was 20.58, 19.85, and 19.32 MPa, respectively. In other words, the MMP of CO2-crude oil decreased with the increase of salinity of formation water.

In view of the formation characteristics as the high viscosity and the high permeability of offshore heavy oil reservoir, simulation of artificial core was developed. The indoor physical simulation experiments under the offshore oil field reservoir conditions were conducted. The effective viscosity of the binary system in the core was determined by the experiment. The corresponding capillary number was calculated according to the effective viscosity and experiments measured the relation curve between the capillary number and the oil displacement efficiency. When the capillary number gets higher, the system recovery efficiency is higher, and the residual oil saturation is lower. With the capillary number increasing, the increase scope of recovery and the decrease scope of residual oil saturation both increase gradually; The capillary number exists a critical value when the order of magnitude between 10-2~1 0-3. When the capillary number is greater than the critical value, it can improve the displacement efficiency greatly. When the capillary number is around 10-1, the oil displacement efficiency and the residual oil saturation tend to be stable. According to the capillary number and oil displacement efficiency curve, optimize the binary system in which the polymer concentration is 1750mg/l and the surface active agent concentration is 0.2%.

Aim at the reservoirs condition of high porosity, high permeability, high viscosity of crude oil in the offshore oilfield, this paper used two-dimensional heterogeneous physical model to conduct laboratory displacement experiments which contain water flooding, polymer flooding and binary combination flooding for offshore heterogeneous reservoirs, studied the displacement efficiency of the binary combination flooding after polymer flooding in offshore oilfield. The experiment results showed that final recovery efficiency of binary combination flooding after polymer flooding was 64.98% which is higher 31.85% than water flooding and higher 19.74% than polymer flooding; analyzed the distribution diagram of saturation at every stage, the swept efficiency of every layer respectively is 97.89%, 94.58%, 86.45%，and the oil saturation decreased in the swept area, which turned out that binary combination flooding could not only enlarge the swept volume, but also could enhance the displacement efficiency and the main effect is in low permeability layer.

The slim tube test is the industry standard for measuring the minimum miscibility pressure at present. However, there is a huge gap between the pore parameters of the slim tube model and the actual reservoir, especially the influence of permeability on MMP is not considered. The previous studies have shown that the minimum miscibility pressure is related to the pore structure and permeability of the reservoir. It is believed that there are some theoretical defects in the MMP measured by the slim tube test. This paper aims at the defect of slim tube test, core displacement experiment is carried out by using natural core to measure the minimum miscibility pressure under different permeability, and to reveal the law of the influence of permeability on the minimum miscibility pressure.