Research On The Mechanism Of Emulsification To Improve Oil Recovery

The chemical flooding system contacts with oil in the process of seepage and forms emulsion under the shearing action of porous media.A large number of laboratory and field tests show that carrying and profile controlling of emulsions play an important role in improving oil recovery.The intrinsic principle of emulsion enhanced oil recovery can be deeply revealed through the dynamic instability process of emulsion and the study of seepage law.The effects of surfactant and polymer on the stability of emulsion were studied under laboratory conditions.The process of dynamic instability of emulsions was monitored in real time,and the internal microscopic dynamic changes during the instability process were analyzed.Oil displacement experiments of binary compound system with three different emulsifying capacities were carried out in three beret cores with different permeability.The influence of emulsifying ability of chemical flooding system on improving oil recovery is studied under different core permeability.The percolation law of emulsion produced by chemical flooding system and oil phase in the formation was studied In the physical model of three-string long core.The result showed that during the instability of the emulsion,the lower part of the emulsion system mainly present the creaming of droplets,accompanied by aggregation and coagulation.The central part mainly present the aggregation and coagulation of droplets.The emulsion have the best stability when the surfactant concentration reached 0.4%.The emulsion stability increased gradually with the increase of polymer relative molecular mass and mass concentration.When the polymer concentration reached 2000mg/L,The flocculation-steric hindrance effect of the emulsion system reaches an equilibrium.The stability of the emulsion system is basically unchanged by increasing the mass concentration of the polymer.The binary compound system has an early emulsification time and the amount of emulsified liquid is smaller in the seepage process of the low-permeability core physical model.The oil-in-water emulsion is mainly formed,the average droplet size is smaller,the distribution is relatively uneven and the stability of the forming emulsion is poor In the early stage of emulsification.The timing of emulsification is late and the amount of emulsified liquid is large in the high permeability core.More types of emulsion are formed,the average particle size is larger,the distribution is more uniform and the stability of the forming emulsion is better in the early stage of emulsification.The stability of emulsion in high permeability and low permeability core is similar In the middle and late stages of theemulsification phenomenon of the binary compound system in the process of core seepage.The oil recovery rate of the chemical flooding system can be increased by increasing the emulsification capacity of the compound flooding system for the medium and high permeability reservoirs.The oil recovery rate can be improved by reducing the interfacial tension of the system to increasing the oil washing efficiency for the low permeability reservoirs.The emulsification occurs mainly in the front and middle of the core In the process of oil displacement.In order to more effectively exert the effect of emulsification,the emulsifying power of the binary compound flooding system should be appropriately weakened and the anti-adsorption ability of the system should be increased under the premise of satisfying the stability of emulsion formation.