Study On Stability And Dehydration Technology Of Polymer Flooding In Bohai Oilfield

With the expansion of polymer injection in Bohai oilfield, it is more and more difficult to demulsificate the polymer-containing produced liquid. The stability of crude oil emulsion containing polymer is the important theoretical foundation of demulsification and dehydration. In order to find cost-effective demulsification method, it is necessary to understand stability of crude oil emulsion with polymer. Based on polymer, crude oil and its components as the research object, oil-water interfacial property and stability of containing-polymer emulsion were studied, and their relationship and the stability mechanism have been discussed. What’s more, dehydration technology of polymer-containing crude oil has been studied in view of the poor demulsification effect in the dehydration of Bohai oilfield. In this paper, the main research work and conclusions are as follows:Crude oil is separated into three components(asphaltene, resin, and oil without asphaltene and resin) by means of solvent separation, and content of each component, element content in the components and their infrared spectrograms are determined, and the results are as follows:crude oil contains high content of asphaltene and resin; the H/C order of each component is:oil without asphaltene and resin> resin> asphaltene; asphaltene and resin, with complex molecular structure, contain much nitrogenous and oxygenous chemical; active components of crude oil mainly exist in asphaltene and resin.Oil-water interfacial tension of crude oil and its component model oil/polymer solution is measured by drop-volume method, and the results are as follows:with the increase of polymer concentration, the interfacial tension reduces first and then rises again; the entire process curve is "V", conforming to interface layer reaction model; with content of asphaltene, resin, oil without asphaltene and resin and crude in the model oil increases respectively, the interfacial tension decreases obviously.The influence of crude oil, its components and polymer on the oil-water interfacial film strength is studied, and the results are as follows:polymer and the components are beneficial to the improvement of the interfacial film strength; with content of polymer, each component (asphaltene, resin, oil without asphaltene and resin and crude oil) in the model oil increases, interfacial film strength increases growly.Polymer and the components are beneficial to stability of emulsion; with content of polymer, each component (asphaltene, resin, oil without asphaltene and resin and crude oil) in the model oil increases, interfacial film strength increases growly, the stability of simulated emulsion is enhanced; the emulsion stability is not one-to-one correspondence relationship to the change of the interfacial tension, but to interfacial film strength.The stability mechanism of the emulsion containing polymer oil is that lower interfacial tension due to attach of polymer and crude active components on the oil-water interface is the precondition of emulsion stability; as polymer and active components in crude oil can improve the interfacial strength, solid and steady interfacial film formed by them is the root cause of the emulsion stability. Aiming at characteristics of produced fluid in Bohai oilfield, the demulsifier (A9: All=2:1) is filtered out. In view of the different polymer content in produced fluid, dehydration technology is studied and the optimized parameters for the dehydration is obtained to providetheory support and technical guarantee of dehydration scheme design and production run.