At present, the polymer injection target of Lamadian oilfield has been shifted to the second type reservoir. Compared with the second type A reservoir,the second type B reservoir has serious heterogeneity and low permeability.For this reason,the study on the characteristics of polymer flooding seepage in the second type B reservoir is carried out.The results show that with the increase of core permeability,the iso⁃permeability point of polymer flooding relative permeability curve moves to the right and the span of two phases increases.Increasing the polymer molecular weight and the injection concentration can make the right end of the curve shift to the right.The polymer flooding resistance coefficient and residual resistance coefficient increase with the increasing of polymer solution concentration and molecular weight,while decrease with the increase of core permeability.There is a good correspondence between the polymer flooding resistance coefficient and the shunt rate.When the resistance coefficient reaches the peak,the shunt rate will reach the peak,and then the shunt rate of the high permeability layer will rise.The higher the molecular weight of the polymer, the higher the concentration of the solution,the greater the difference in permeability level,and the earlier the diversion rate of high permeability layer rises.

The concentration of ions in the three element composite flooding is higher, the radius of the suspended particles is larger, the emulsification of the crude oil is serious, and the O/W emulsion is formed, which contains the polymer and the surface active agent. So, the viscosity of the three element composite flooding is larger and the composition is more complex. The above reasons make it difficult for the three yuan produced liquid to achieve better separation effect by conventional sedimentation treatment when oil and water separation is carried out. Through indoor sedimentation experiment, the settlement effect of the three surfactant polymer flooding under the conditions of different settling time and settlement temperature is studied, and effect and technical limits after mixing of three yuan and polymer flooding system are clearly defined. The experimental results show that three yuan of produced liquid in the blending of polymer flooding produced liquid, helps to reduce the three yuan produced liquid mixed with polymer flooding produced liquid is helpful to reduce the oil-water separation difficulty. From the analysis of water quality of mixed wastewater, the mixed three yuan extraction liquid and the polymer flooding recovery solution can not only reduce the sewage the treatment difficulty, but also be more conducive to the stable operation of the existing three yuan oilfield produced water treatment process. The optimum mixing ratio of three yuan production fluid and polymer flooding production fluid is1∶3,and the optimum mixing settlement time limit is 8 h.

The acidizing cleanup emulsion phenomenon is serious, and it can not enter the power off process. In view of the above problems, indoor simulation experiments were carried out to explore the influence of temperature, pH value, moisture content, the oil phase of the returned liquid, the water phase of the returned liquid, the iron-containing compound and the mud content on electric dehydration of returned acidizing fluids. It was found that when the impurities in the oil were less, the water phase and water content of the returned acidizing fluids had little effect on the electric dehydration, the increasing of the temperature was beneficial to the effluent demulsification, and neutral pH value was the most suitable condition for the demulsification of the returned fluids. The ferric hydroxide colloid which was wrapped with crude oil, sludge and free water in oil, forming a very high conductivity intermediate layer between the oil phase and the water phase, was the main cause of electric dehydrator trip.