Patent ID: 8206993

Claim:
A method for determining the characteristics of at least one fluid sample under investigation having at least one constituent, wherein the at least one fluid sample includes one of a crude oil, a mixture of homologous hydrocarbon molecules, or some combination thereof, the method comprising: a. obtaining measurements of a plurality of calibration samples at a first temperature and a reference pressure, wherein the calibration samples have differing mean chain lengths, and wherein said measurements are selected from the group consisting of one of diffusion coefficients, relaxation times, and combinations thereof; b. determining the density of more than one pure alkane or mixtures of alkanes at the first temperature and the reference pressure, wherein density is determined as a function of mean chain length; c. determining one of diffusion coefficients, relaxation times or both for the at least one fluid sample under investigation at the first temperature and a second pressure; d. determining the density of the at least one fluid sample under investigation at the first temperature and the second pressure; e. applying the density function of (b) to the density measurements of (d) and using the measurements of (a) to provide exponents and constants of proportionality so as to determine a first scaling law of diffusion (1), a second scaling law of relaxation (2), or both, at the second pressure in terms of chain length, according to the following: D i = A ( T,P 0 ) N i −ν N eff −β(T,P 0 ) (1), Wherein D i is a diffusion coefficient, N i is the chain length of the i th component, N eff is the mean chain length of a mixture of one or more alkanes that has the density at the reference pressure (P 0 ) equal to the density of the fluid sample at the second pressure, A and β are temperature (T) and pressure (P) dependent coefficients; T 1i =B ( T,P ) N i −k N eff −γ(T,P 0 ) (2), Wherein T 1i is the spin-spin or spin lattice relaxation time of the i th component, N i is the chain length of the i th component, N eff is the mean chain length of a mixture of one or more alkanes that has the density at the reference pressure (P 0 ) equal to the density of the fluid sample at the second pressure, B and γ are temperature (T) and pressure (P) dependent coefficients; f. applying the scaling law of (e) to the data of (c) to determine the composition of the at least one fluid sample under investigation.