Research On Ultra-low Interfacial Tension Foam Flooding System

Foam flooding with its good oil displacement performance has attracted much attention in terms of enhanced oil recovery.Studies have shown that during the oil displacement process,the foam can significantly reduce the fluidity of the injected fluid,improve the fluidity ratio,reduce the relative permeability of the fluid,delay the breakthrough time of the injected fluid,plug the large pores of the high permeability layer,and change the liquid flow.The direction is better to achieve the blocking effect.The field test results also proved that foam flooding is feasible,and the foam flooding after water flooding and polymer flooding has achieved good results.However,foam is thermodynamically unstable fluid,its stability is affected by many factors,including rapid defoaming in oil,and extremely easy to crack in the case of high temperature and high salinity.Foam stability has become an urgent problem to be solved in foam flooding.In addition,the solution system used for foam flooding is difficult to combine both ultra-low interfacial tension and stable foam properties,and there are few studies in this paper in the literature,which provides a new idea for this paper.Anionic-nonionic surfactant fatty alcohol polyoxyethylene ether sulfate(AES)was synthesized in the laboratory.The fatty alcohol polyoxyethylene ether combines the properties of both anionic and nonionic surfactants,which has good foam properties and surface activity and also has good compatibility with other surfactants.Fatty alcohol polyoxyethylene ether and sulfamic acid were used to synthesize AES.The experiment finally determined that the optimal molar ratio of fatty alcohol polyoxyethylene ether and sulfamic acid during synthesis was 1:2,the optimum temperature was 95℃,and the optimal reaction time was 60 min.Several different types of surfactants was choosed on the basis of AES synthesized for compounding,and the compounding system with excellent foam performance and surface activity is carried out evaluation of temperature resistance,mineralization resistance and oil resistance.The Waring-Blender method was used for foaming,Subsequently,half-life of the foam was measured.The surface tension and oil-water interfacial tension of the compound system were measured by the lifting ring method and the rotary drop method.In the experiment,AES-CTAB compounding system with excellent foaming properties and surface activity was selected,and the optimum compounding molar ratio was 3:1,and the optimum total concentration was 0.02 mol·L-1.The temperature resistance,mineralization resistance and oil resistance were evaluated.The system has a temperature resistance of 200 ° C and hasa resistance to crude oil with a mass fraction of 20%.,the increase in salinity can improve the foam stability and surface activity of the compound system.The experiment studied the effect of foam on enhanced oil recovery from three aspects:gas-liquid ratio,foam injection amount and temperature.The results show that the optimum gas-liquid ratio is 2:1,and the optimum foam injection amount is 0.6PV.The foam recovery rate gradually decreases with the increase of temperature,and the foam recovery rate is above30% in the range of 60-100℃.