Study On The Emulsification Process Of ASP Flooding And Its Effect On Oil Displacement

In order to fully exploit the underground oil and gas resources,Daqing Oilfield carried out on-site test of enhanced recovery of ternary composite flooding on the basis of polymer flooding.Field experiments show that ASP flooding has achieved good results in the exploitation of the oil layer and the second oil layer reservoirs with better formation properties.In the process of ASP flooding in three types of reservoirs,emulsification occurs between ASP system and reservoir fluid,which seriously affects the percolation characteristics and oil displacement effect of ASP system in formation.Therefore,it is necessary to study the emulsification phenomenon and oil displacement mechanism of ASP flooding in depth.Firstly,the solution properties of the injection system were studied.Polymer DS800,surfactant petroleum sulfonate and alkali sodium carbonate were used as ASP system.The rheological properties and interface characteristics of ASP system were tested under different polymer concentration,surfactant content and alkali content..The results show that the ASP system belongs to non-Newtonian fluid,and its rheological model conforms to power law model.The rheological properties of ASP system are viscous fluid.The concentration of polymer has the greatest influence on the rheological properties of ASP system,alkali has the second effect on surfactant.The interfacial tension between ASP system and Daqing crude oil can reach 10-3mN·m-1,in which the content of alkali and surfactant has a great influence on the ability to reduce interfacial tension.The viscosity prediction model of ASP system with the content of three chemicals is obtained by orthogonal experiments.At the same time,the emulsification performance and emulsification law of ASP system were studied by laboratory stirring experiment and micro-seepage experiment,and the emulsification rate,emulsification type,particle size distribution of emulsion,emulsification stability and rheological property of emulsion were obtained under different oil-water ratio.Emulsification occurs between the combined system and the remaining oil,which has a certain influence on the oil displacement process.Based on the characteristics of three types of reservoirs in Daqing Oilfield,the effects of core permeability and clay mineral content on the percolation characteristics of ASP system were studied.The results show that in porous media with water permeability less than 100 mD,ASP system has good injectability,good ability to establish resistance coefficient and residual resistance coefficient,and strong ability to control fluidity.The lower permeability,the greater resistance coefficient and residual resistance coefficient.It can be seen that when the permeability is too low.the resistance coefficient is too large,and there will be injection in ASP flooding.Involvement.When the clay mineral content is in the range of 5%-10%,the greater the clay mineral content,the greater the resistance coefficient and residual resistance coefficient;when the clay mineral content is below 5%,the residual resistance coefficient does not change much.During the core displacement experiment,it is found that both ultra-low interfacial tension and emulsification can improve oil recovery.In the same process of system flooding with ultralow interfacial tension,the oil recovery of three types of reservoirs is increased by about 5%when emulsification occurs compared with that of non-emulsification.It can be seen that emulsification is conducive to improving the recovery of three types of reservoirs.