Characterization of crude oil and its fractions by fluorescence spectroscopy analysis

Abstract

A system and a method are provided for calculating the cetane number, pour point, cloud point, aniline point, aromaticity, and/or octane number of a crude oil and its fractions from the density and fluorescence spectroscopy of a sample of the crude oil.

We claim: 
     
         1 . A system for evaluating a crude oil sample and calculating an indicative property of a naphtha or gas oil fraction of the crude oil sample without first distilling said naphtha or gas oil fraction, the system comprising:
 a fluorometer that outputs fluorescence spectroscopy data;   a non-volatile memory device that stores calculation modules and data, the data including density of the crude oil sample and fluorescence spectroscopy data indicative of absorbance units at predetermined increments between a predetermined range for the oil sample, as derived by an analysis of the crude oil sample by the fluorometer;   a processor coupled to the non-volatile memory;   a first calculation module that retrieves the fluorescence spectroscopy data from the non-volatile memory device, calculates a crude oil fluorescence spectroscopy index value of the fraction from the absorbance units of the fluorescence spectroscopy data, and transfers the calculated crude oil fluorescence spectroscopy index value into the non-volatile memory; and   a second calculation module that calculates the indicative property for the naphtha or gas oil fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques, and that stores the indicative property into the non-volatile memory device;   wherein the two variables of the two-variable polynomial equation are the crude oil fluorescence spectroscopy index and the density of the crude oil sample.   
     
     
         2 . The system of  claim 1 , wherein the indicative property is the cetane number. 
     
     
         3 . The system of  claim 1 , wherein the indicative property is the pour point. 
     
     
         4 . The system of  claim 1 , wherein the indicative property is the cloud point. 
     
     
         5 . The system of  claim 1 , wherein the indicative property is the aniline point. 
     
     
         6 . The system of  claim 1 , wherein the indicative property is the aromaticity. 
     
     
         7 . The system of  claim 1 , wherein the indicative property is the octane number. 
     
     
         8 . The system of  claim 1 , wherein the temperature range for the fluorometer is 20-1000° C. 
     
     
         9 . The system of  claim 1 , wherein the fluorescence spectroscopy index is that of whole crude oil. 
     
     
         10 . The system of  claim 1 , wherein the fluorescence spectroscopy index is calculated from fluorescence spectroscopy data measured in the wavelength range of 250-800 nm. 
     
     
         11 . The system of  claim 1 , wherein the fluorescence spectroscopy data is obtained directly from core and/or drill cuttings material. 
     
     
         12 . A method for evaluating a crude oil sample and calculating an indicative property of a naphtha or gas oil fraction of the crude oil sample without first distilling said naphtha or gas oil fraction, the method comprising:
 obtaining density of the crude oil sample;   providing a fluorometer that outputs fluorescence spectroscopy data   subjecting said crude oil sample to fluorescence spectroscopy analysis using the fluorometer, and entering absorbance units of the fluorescence spectroscopy data into non-volatile memory of a computer;   using a processor of the computer to calculate a crude oil fluorescence spectroscopy index value of the fraction from the absorbance units of the spectroscopy data; and   using the processor to calculate and enter into the non-volatile memory the indicative property for the naphtha or gas oil fraction of the crude oil from a two-variable polynomial equation with predetermined constant coefficients developed using linear regression techniques;   wherein the two variables of the two-variable polynomial equation are the crude oil fluorescence spectroscopy index and the density of the crude oil sample.   
     
     
         13 . The method of  claim 12 , wherein the indicative property is the cetane number. 
     
     
         14 . The method of  claim 12 , wherein the indicative property is the pour point. 
     
     
         15 . The method of  claim 12 , wherein the indicative property is the cloud point. 
     
     
         16 . The method of  claim 12 , wherein the indicative property is the aniline point. 
     
     
         17 . The method of  claim 12 , wherein the indicative property is the aromaticity. 
     
     
         18 . The method of  claim 12 , wherein the indicative property is the octane number. 
     
     
         19 . The method of  claim 12 , wherein the temperature range for the fluorometer is 20-1000° C. 
     
     
         20 . The method of  claim 12 , wherein the fluorescence spectroscopy index is that of whole crude oil. 
     
     
         21 . The method of  claim 12 , wherein the fluorescence spectroscopy index is calculated from fluorescence spectroscopy data measured in the wavelength range of 250-800 nm. 
     
     
         22 . The method of  claim 12 , wherein the fluorescence spectroscopy data is obtained directly from core and/or drill cuttings material.