Performance Variation In Polymer Surfactant Flooding Process And Its Effect On Recovery Efficiency

As a new type of chemical oil displacement system,polymer surfactant has been widely sturdily by domestic and foreign researchers in recent years.However,the study on dynamic change of its properties during the long distance migration,the effective distance of mobility control and emulsification and the mechanism of enhanced oil recovery of the polymer surfactant in the reservoir is still not perfect at present.This paper study a new polymer surfactant made in the laboratory and evaluate the basic properties of the polymer surfactant solution,such as viscosity properties,rheological properties and emulsifying properties etc.Then we use 30 meters long sand-packed model to simulate the flow of the polymer surfactant in the formation,monitor the changes of its properties during the long distance migration and analyze the change rules of its properties and its adaptable limit.In the end,we use the microscopic visual model and artificial core model to analyze the adverse effect of the loss of polymer surfactant on its capacity of activating the residual oil and its oil displacement efficiency in the process of long distance displacement experiment.The results of static evaluate experiment showed that the polymer surfactant has favorable properties on viscosity raising and emulsifying,its temperature resistance and salt tolerance are better than common polymer.In the oil displacement experiment of 30 m long sand-packed model,under the condition of injecting 0.6PV polymer surfactant solution,it can improve oil recovery by 18.17% on the basis of the water flooding.After 16.58 meters,its effect of pressurization is not ideal,and the values of both concentration and viscosity are in low level,its capability of mobility control is weak.During the displacement process,sampling results in the range of 6.38 meters ~ 19.13 meters showed there was obvious oil emulsification in the matrix.We can observe the apparent emulsification during the displacement process and emulsion band in the model,but after 19.13 meters,emulsification cannot be observed.In the experiment of microscopic physical model,polymer surfactant can expend the swept volume and reduce the residual oil saturation by emulsifying,with the decrease of the concentration of polymer surfactant,the volume of residual oil increase.In the core displacement experiment,when the concentration of polymer surfactant is reduced from 2000mg/L to 400mg/L,recovery after water flooding is reduced from 19.69% to 6.36%,this indicates that the loss of polymer surfactant during the long distance migration will significantly reduce its effect of oil displacement.Therefore,we should minimize the loss of polymer surfactant in practical applications,increase the effective scope of polymer surfactant.