Characterization of crude oil by ultraviolet visible spectroscopy

1. A system for determining indicative properties of a gas oil fraction of a crude oil, based upon ultraviolet visible spectroscopy data derived from a sample of the crude oil and the weight and density of the sample, the system comprising:

a non-volatile memory device that stores calculation modules and data;

a processor coupled to the memory;

a first calculation module that calculates a crude oil ultraviolet visible index value for the gas oil fraction based on the sample's weight and the absorbance values of the spectroscopy data;

a second calculation module that derives the cetane number for the gas oil fraction of the crude oil as a function of the ultraviolet visible index and density of the sample;

a third calculation module that derives the pour point for the gas oil fraction of the crude oil as a function of the ultraviolet visible index and density of the sample;

a fourth calculation module that derives the cloud point for the gas oil fraction of the crude oil as a function of the ultraviolet visible index and density of the sample; and

a fifth calculation module that derives the aniline point for the gas oil fraction of the crude oil as a function of the ultraviolet visible index and density of the sample.

2. The system of claim 1 , wherein the gas oil fraction boils in the nominal range of 180-370° C.

3. A method for operating a computer to determine indicative properties of a gas oil fraction of crude oil boiling in the range of 180-370° C. based upon a sample of the crude oil collected from an oil well, stabilizer, extractor, or distillation tower, the method comprising:

weighing the sample;

preparing said sample for ultraviolet visible spectroscopy analysis by diluting the sample with solvents;

obtaining spectra data for the sample by an ultraviolet visible spectroscopy analysis in a wavelength range from 220-500 nm;

entering into the computer the spectra data for the sample;

calculating an ultraviolet visible index of the gas oil fraction based on the spectra data;

calculating the cetane number for the gas oil fraction as a function of the ultraviolet visible index and density of the sample, and storing the calculated cetane number into a non-volatile memory associated with the computer;

calculating the pour point for the gas oil fraction as a function of the ultraviolet visible index and density of the sample, and storing the calculated pour point into the non-volatile memory associated with the computer;

calculating the cloud point for the gas oil fraction as a function of the ultraviolet visible index and density of the sample, and storing the calculated cloud point into the non-volatile memory associated with the computer; and

calculating the aniline point for the gas oil fraction as a function of the ultraviolet visible index and density of the sample, and storing the calculated aniline point into the non-volatile memory associated with the computer.

4. The method of claim 3 , wherein the gas oil fraction boils in the nominal range of 180-370° C.

5. The method of claim 3 , wherein the solvent used is a mixture of paraffinic and polar solvents.

6. The method of claim 5 , wherein the paraffinic solvent contains from 5-20 carbon atoms.

7. The method of claim 5 , wherein the polar solvent is selected based on is Hildebrand solubility factor or by its two-dimensional solubility parameter.

8. The method of claim 7 , wherein the polar solvent has a Hildebrand solubility rating of at least 19.

9. The method of claim 7 , wherein the two-dimensional solubility factors of the polar solvent are the complexing solubility parameter and the field force solubility parameter.

10. The method of claim 9 , wherein the polar solvent's complexing solubility parameter component describes the hydrogen bonding and electron donor acceptor interactions.

11. The method of claim 9 , wherein the polar solvent's field force solubility parameter is based on the van der Waals and dipole interactions.

12. The method of claim 5 , wherein the paraffinic-to-polar solvent ratio is 70:30 or greater.

13. The method of claim 5 , wherein the paraffinic-to-polar solvent ratio is 90:10 or greater.

14. The method of claim 3 , wherein the ultraviolet visible spectroscopy data is obtained from an ultraviolet visible spectroscopy analysis in a wavelength range from 220-400 nm.

15. A system for evaluating a crude oil sample and calculating an indicative property, the system comprising:

an ultraviolet visible spectrophotometer;

a non-volatile memory device that stores calculation modules and data, the data including density of the crude oil sample and spectroscopy data obtained from the ultraviolet visible spectrophotometer;

a processor coupled to the non-volatile memory;

a first calculation module that calculates a crude oil ultraviolet visible index value for the gas oil fraction based on the sample's weight and the absorbance values of the spectroscopy data; and

a second calculation module that calculates the indicative property as a function of the ultraviolet visible index and the density of the sample.

16. The system for evaluating a crude oil sample of claim 15 , wherein the indicative property being calculated in the second calculation module is the cetane number.

17. The system for evaluating a crude oil sample of claim 15 , wherein the indicative property being calculated in the second calculation module is the pour point.

18. The system for evaluating a crude oil sample of claim 15 , wherein the indicative property being calculated in the second calculation module is the cloud point.

19. The system for evaluating a crude oil sample of claim 15 , wherein the indicative property being calculated in the second calculation module is the aniline point.

20. A method for operating a computer to evaluate a crude oil sample and calculate an indicative property, the method comprising:

weighing the sample;

preparing said sample for ultraviolet visible spectroscopy analysis by diluting the sample with solvents;

obtaining spectra data for the sample by an ultraviolet visible spectroscopy analysis in a wavelength range from 220-500 nm;

entering into the computer the spectra data for the sample;

calculating an ultraviolet visible index of the gas oil fraction based on the spectra data; and

calculating the indicative property as a function of the ultraviolet visible index and density of the sample, and storing the calculated indicative property into a non-volatile memory associated with the computer.

21. The method for operating a computer of claim 20 , wherein the indicative property being calculated is the cetane number.

22. The method for operating a computer of claim 20 , wherein the indicative property being calculated is the pour point.

23. The method for operating a computer of claim 20 , wherein the indicative property being calculated is the cloud point.

24. The method for operating a computer of claim 20 , wherein the indicative property being calculated is the aniline point.