The Effect of pH value on Crude Oil and its Fractions Oil-water Interficial Film Dilational Viscoelastic Properties

The study of crude oil and its polar fractions oil-water interfacial film dilational viscoelasticity has important significance to understand the stability of crude oil emulsion. By interfacial expansion rheological determinator, the Gudao Crude oil and its fractions dilational viscoelasticity under different pH value and dilational frequency was tested. The result shows that the dilational modulus of Asphaltene, Resin, Crude oil and Oil fraction reduced gradually under different dilational frequency and pH value, which has a relationship with polar groups in the crude oil and its fractions. When pH value was different, crude oil and its fractions dilational modulus and dilational frequency was similar. Dilational modulus increased with the increases of dilational frequency, but increasing amplitudes were different. Under the same pH value, dilational viscosity and phrase angle of Crude oil and its fractions were decreased with the increase of dilational frequency. The influence degree on different fractions was different, the influence degree of Oil fraction of dilational viscosity and phrase angle was small, Asphaltene was big. The dilational elasticity of Crude oil and its fractions increased with the increase of dilational frequency. Under different dilational frequency, the dilational modulus of Crude oil, Resin and Asphaltene increased with the increase of pH value, and it had no influence on dilational modulus of Oil fraction. The total dilational elasticity tendency of Crude oil, Resin and Asphaltene was increase, while dilational elasticity of Oil fraction decreased with the increases of pH value. The variation of dilational elasticity and phrase angle of Crude oil and its fractions was relatively complex. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of International Materials Science Society.