Bp Oil International Limited

Antoine Pasquier

Andre Martens

Didier C Lambert

Gilbert Ventron

Alain Espinosa

The properties of a liquid hydrocarbon blend are determined from the NIR (Near Infra Red) spectrum of the components of the blend. This is accomplished by: (a) determining with an IR spectrometer, the absorbance of the components of the blend at a certain number of frequencies in the spectral range 16667 to 3840 cm.sup.-1 starting from a defined base line, (b) determining for each component and each property, a spectral mixture index (SMI) by applying a correlation between the SMI and the absorbance values, and then (c) calculating the property (J) to be determined by applying a linear expression, J=f.sub.a SMI.sub.a.sup.J +f.sub.s SMI.sub.b.sup.J +f.sub.c SMI.sub.c.sup.J + . . . f.sub.o SMI.sub.o.sup.J where SMI.sup.J.sub.(a, b, c . . . ) is the Spectral Mixture Index for property J for each component (a, b, c . . . ) and f.sub.(a, b, c . . . ) is the fraction by volume of that component in the final blend. The correlation in (b) is determined experimentally by multivariate regression, and is dependent upon the type of spectrometer used, the property to be determined, and the frequencies used.

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Antoine Pasquier