Application of surface laser-light scattering spectroscopy to photoabsorbing systems: the measurement of interfacial tension and viscosity in crude oil

We have successfully used surface laser-light scattering spectroscopy to measure the interfacial tension and viscosity in a strongly photoabsorbing crude oil system. Photothermal distortion of the sample interface was avoided by judicious choice of laser power, scattering angle, and optical configuration. Measurements were performed on a stock tank crude oil/air interface at ambient conditions for a series of incident laser powers. The measured interfacial tension was in good agreement with that obtained using the Wilhelmy plate technique. The measured viscosity was in good agreement with that obtained using low-shear viscometry. Both the interfacial tension and the liquid viscosity were independent of laser power for low incident powers. Surface laser-light scattering is now fully qualified for measurements of interfacial tension and viscosity of reservoir fluids at the elevated pressures and temperatures of an oil-field reservoir.