Patent ID: 8332162

Claim:
A method of measuring petroleum fractions, comprising the steps of: a) measuring a refractive index n of a petroleum fluid using refractometry; b) measuring a kinematic viscosity v of the petroleum fluid; c) calculating an API gravity of the petroleum fluid as API=−320.77n+501.4 if n is between 1.42 and 1.5227, and calculating the API gravity as API=−394.12n+615.12 if n is between 1.9385 and 1.4976; d) calculating a specific gravity SG of the petroleum fluid as SG=141.5/(API+131.5); e) calculating a density d of the petroleum fluid; f) calculating a viscosity gravity function VGF of the petroleum fluid as VGF=−1.816+3.484SG−0.1156 v; g) calculating a refractivity intercept Ri as Ri=n−d/2; h) calculating a mole fraction of paraffins as Xp=−23.94+24.21Ri−1.092VGF; i) calculating a mole fraction of naphthenes as Xn=41.14−39.43Ri+0.672VGF; and j) calculating a mole fraction of aromatics as Xa=−16.2+15.22Ri+0.465VGF.