| With the widespread application of polymer flooding,the environmental problems have consequently received significant attention during the oil exploitation.Despite the excellent efficiency of oil displacement in polymer flooding,the production of oil field has been plagued by the treatment of oily wastewater as a result of large quantities of residual polymer,which has not been fundamentally solved.Studies have shown that the adsorption of polymers at the oil/water interface is an essential reason for the stability of the oil-water emulsion produced in the wastewater.However,the quantitatively research of the adsorption between residual polymer and oil-water interface has not been reported previously,and it is not clear the adsorption mechanism of residual polymer at the oil-water interface.Therefore,it is very important to develop a high-sensitivity,non-destructive and in-situ method to research the adsorption of residual polymer at oil/water interface and reveal the adsorption mechanism of residual polymer at oil/water interface.Dual polarization interferometry(DPI),a high precision and newly-developed nonlinear optical technique,can proceed with real-time monitoring of the dynamical changes in the surface/interfacial mass,thickness,density accurately.In this paper,an experimental method for simultaneously qualitative and quantitative study of residual polymer adsorption at the oil-water interface has been established by DPI.The adsorption behavior of residual polymer at the oil/water interface was monitored in real time.In this paper,the asphaltene model compound(C5Pe)was spin-coated on the surface of DPI sensor chip for construction of an oil-water interface by optimizing the mearsuring conditions.The sensitive changes of the evanescent field at DPI sensor chip were prodcued through the interaction between the hydrophobic associating polymer(HAPAM)and the oil-water interface to obtain the interference intensity and phase change of the transmitted light wave.The sensitive varation of the mass,density and thickness of the oil-water interface can be acquired on the basis of the Maxwell equation and the Feijter equation.Through the sensitive variation of the thickness,mass and density of oil-water interface,a deeper insight into the adsorption kinetics,the layer conformation,the adsorption thermodynamics were analyzed,and then the kinetics and thermodynamic model of the adsorption process were established.Moreover,the effects of the molecular weight,the salt concentration,the crude oil component and the polymer structure on the adsorption behavior were discussed.In combination with the rupture rate of oil droplets and the strength of oil-water interface,the effect of residual polymer on the stability of oil/water interface under different influence factors were investigated.Furthmore,in connection with the adsorption behavior revealed by DPI,the relationship between adsorption behavior and interfacial stability was inferred and the mechanism of the stability of oil/water interface induced by the adsorption of HAPAM was proposed.Based on above studies,HAPAM adsorbion at the oil/water interface can be interpreted as three stages:diffusion,adsorption and desorption.As the variation of HAPAM concentrations,two patterns of adsorption layer morphology are indicated.When HAPAM concentration is 500 mg/L,HAPAM molecules firstly adsorb at the oil/water interface in manner of "lying flat" as far as possible,and then change to the form of "partial contact";When HAPAM concentrations increase to 1000-3000 mg/L,HAPAM molecules firstly adsorb at oil film in form of "partial contact" and then adsorb at the oil/water interface uniformly.HAPAM adsorption adheres to an exothermic process and the value of interface entropy is proven to reduce.With the decrease of HAPAM molecular weight and the salt content,it is favorable to strengthen the stability of oil-water interface by the remarkable adsorption behavior of HAPAM at the oil/water interface.Adopted the oil component of SZ-361 crude in researching,it is indicated that HAPAM molecules can be steadily adsorbed at the layer of asphaltene and resin,while produce obvious elution on the layer of saturates and aromatics.The interfacial stability of each oil component is:asphaltene>resin>aromatics>saturates.The effects of molecular structure of residual polymer on the interfacial adsorption behavior demonstrated that HAPAM has the most remarkable adsorption behavior at the oil/water interface and the strongest stabilization effects on the oil/water interface.The hydrophobic interaction between the hydrophobic monomers and the oil/water interface is the main contribution to adsorption and result in the increase of the stability of oil/water interface. |
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