Study On Interfacial Properties Of Crude Oil And Its Acid-base Fractions

With different oil field deeply exploited,new technology of flooding and new floodingchemicals have been applied in large scale, which made the produced fluid compositionbecome more complex. The stability of emulsion is significantly enhanced and makes itdifficult for desalting and dewatering. Systematically study the composition of produced fluidcontaining polyethylene composition and oil-water interfacial properties has theoretical andpractical significance in stabiling mechanism of produced fluid and oil-water separation. Thisthesis mainly studied the interfacial properties of crude oil from Gudao No.5 union stationand its acid-base fractions, and additionally investigated the influence of the properties on thestability of crude oil emulsion. The crude oil is separated into acid, base, amphoteric andneutral fractions by ion exchange chromatography (IEC). It has been systematically studiedthe influence of partially hydrolyzed polyacrylamide, clay, and demulsifiers on the dilationalviscoelasticity and surface pressure. The influence of concentration, pH value, temperatureand salts on these properties is also studied.The result shows that, the content of neutral fraction in Gudao crude oil is up to 77%.The structure and composition of amphoteric fraction is complicated, the percentage ofheteroatom is high, and the structure of fractions is different. HPAM and clay had a biginfluence on dilational viscoelasticity of crude oil and its fractions. As concentration ofHPAM increasing, the stability of interfacial film increased; The tendency of interfacial filmsdilational viscoelasticity formed by oil fractions and HPAM changed as follows: as thedilational frequency increasing, the dilational modulus, the dilational elasticity and phraseangle increased, while the dilational viscosity decreased; As HPAM molecular weightincreasing, the stability of interfacial film stabilized by crude oil and acid-base fractions isincreased then decreased, the interfacial activity of crude oil and amphoteric fraction is thehighest; Additionally, as concentration of sodium montmorillonite increasing, the dilationalmodulus, elasticity and viscosity increased, while phrase angle regularity was poor. Thestability of interfacial film formed by sodium montmorillonite and amphoteric fraction wasthe strongest. As dilational frequency increasing, the dilational modulus and dilationalelasticity increased, while dilational viscosity decreased.The surface pressure of crude oil and its fractions decreased in the following orders: amphoteric fraction> acid fraction> base fraction >crude oil > neutral fraction. As theconcentration of crude oil and its fractions increased, the surface pressure increased. Astemperature increasing, surface pressure of crude oil and its fractions surface film changedslightly. When the water phase pH value closed to 7, surface pressure of crude oil andamphoteric fraction was the lowest. As pH value increasing, surface pressure of acid fractionincreased, while base fraction is in the opposite situation. With concentration of salt in thewater phase increase, surface pressure of crude oil and its fractions increased. The destructiveeffect of Ca ion on the emulsion stability was the strongest. The mechanical strength ofSurface film is enhanced by sodium montmorillonite, and the emulsion was stable. With theconcentration of HPAM in the water phase increases, the surface pressure raised. The smallermolecular weight of HPAM, the higher surface pressure was. When demulsifier was added,the surface pressure of crude oil and its fractions was greatly reduced. Branch chaindemulsifier had stronger ability to reduce surface pressure, and had bigger influence on thestability of emulsion.