Optimization And Evaluation Of ASP System Based On Emulsifying Property

ASP flooding can dramatically enhance oil recovery when the oil-water interfacial tension reaches ultra-low level during flooding.However,results from numbers of field experiments and laboratory studies have shown the fact that the ultra-low interfacial tension is not the only decision,and the emulsification of ASP system is also a key factor to enhance oil recovery,though the former is an important economic and technical condition to obtain considerable oil recovery.This paper analyzes the advantages and disadvantages of the existing methods of evaluation of emulsifying capacity and emulsion stability,and puts forward a method to evaluate the composite performance of ASP system in emulsification(C_PI)by introducing the dynamic instability index TSI.By using this method,the effects of surfactants,alkali concentration,relative molecular weight of HPAM,polymer concentration on the composite performance of ASP system in emulsification are studied,and a kind of ASP system with good composite performance in emulsification is screened out.The effect of emulsification of the selected formula on enhancing oil recovery is studied through a series of laboratory simulation experiments including core,sand-filled tube and plate radial model physical simulation,and its effect on enhancing oil recovery is used in contrast to Daqing conventional ASP system with ultra-low IFT propotery.The mechanism how emulsification can enhance oil recovery is also studied by means of microscopic displacement experiment.The results have shown that composite performance of ASP system in emulsification is a comprehensive result of its effective components;ASP system with excellent composite performance in emulsification works better in enhancing oil recovery than the conventional system;the higher the permeability,the larger the enhanced oil recovery rate,and the maximum rate can reach about 5%;emulsion forming in the flooding process can cause fluctuations of the injection pressure and the water cut,and the fluctuations are interrelated,the smaller the permeability,the more obvious the fluctuation;the mechanism by which the ASP system designed according to emulsifying property can enhance oil recovery is that emulsion is formed by emulsifying effect of ASP system on crude oil,and the emulsion can block big pore throats,thereby forcing the following fluid to change its way and expanding the swept volume;the emulsion can effectively start oil in dead ends and columnar residual oil,and displacement efficiency is improved as a result.