Abstract:
A system and a method for characterizing an aromaticity value of a crude oil sample from the weight and ultraviolet visible spectroscopy of the sample id provided. The system and method includes calculating and assigning a crude oil ultraviolet visible index and using the assigned index to calculate and assign an aromaticity value of the sample, and optionally to calculate and assign an API gravity.

Description:
RELATED APPLICATIONS 
       [0001]    This application 
         [0002]    is a continuation of U.S. patent application Ser. No. 15/235,680, which
       is a continuation-in-part under 35 USC §365(c) of PCT Patent Application No. PCT/US16/12114 filed Jan. 5, 2016, which claims the benefit of U.S. Provisional Patent Application No. 62/099,658 filed Jan. 5, 2015, and   is a continuation-in-part of U.S. patent application Ser. No. 13/400,787 filed Feb. 21, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/445,217 filed Feb. 22, 2011,       
 
         [0005]    the disclosures of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0006]    This invention relates to a method and process for the evaluation of samples of crude oil and its fractions by ultraviolet visible spectroscopy. 
       BACKGROUND OF THE INVENTION 
       [0007]    Crude oil originates from the decomposition and transformation of aquatic, mainly marine, living organisms and/or land plants that became buried under successive layers of mud and silt some 15-500 million years ago. They are essentially very complex mixtures of many thousands of different hydrocarbons. Depending on the source, the oil predominantly contains various proportions of straight and branched-chain paraffins, cycloparaffins, and naphthenic, aromatic, and polynuclear aromatic hydrocarbons. These hydrocarbons can be gaseous, liquid, or solid under normal conditions of temperature and pressure, depending on the number and arrangement of carbon atoms in the molecules. 
         [0008]    Crude oils vary widely in their physical and chemical properties from one geographical region to another and from field to field. Crude oils are usually classified into three groups according to the nature of the hydrocarbons they contain: paraffinic, naphthenic, asphaltic, and their mixtures. The differences are due to the different proportions of the various molecular types and sizes. One crude oil can contain mostly paraffins, another mostly naphthenes. Whether paraffinic or naphthenic, one can contain a large quantity of lighter hydrocarbons and be mobile or contain dissolved gases; another can consist mainly of heavier hydrocarbons and be highly viscous, with little or no dissolved gas. Crude oils can also include heteroatoms containing sulfur, nitrogen, nickel, vanadium and other elements in quantities that impact the refinery processing of the crude oil fractions. Light crude oils or condensates can contain sulfur in concentrations as low as 0.01 W %; in contrast, heavy crude oils can contain as much as 5-6 W %. Similarly, the nitrogen content of crude oils can range from 0.001-1.0 W %. 
         [0009]    The nature of the crude oil governs, to a certain extent, the nature of the products that can be manufactured from it and their suitability for special applications. A naphthenic crude oil will be more suitable for the production of asphaltic bitumen, a paraffinic crude oil for wax. A naphthenic crude oil, and even more so an aromatic one, will yield lubricating oils with viscosities that are sensitive to temperature. However, with modern refining methods there is greater flexibility in the use of various crude oils to produce many desired type of products. 
         [0010]    When produced at the well, crude oil is usually accompanied by variable amounts of sweet and sour gases, as well as formation brines having high total dissolved solids (TDS). The crude oil is usually stabilized and desalted soon after its production from a well. 
         [0011]    A crude oil assay is a traditional method of determining the nature of crude oils for benchmarking purposes. Crude oils are subjected to true boiling point (TBP) distillations and fractionations to provide different boiling point fractions. The crude oil distillations are carried out using the American Standard Testing Association (ASTM) Method D 2892. The common fractions and their nominal boiling points are given in Table 1. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Fraction 
                 Boiling Point, ° C. 
               
               
                   
                   
               
             
             
               
                   
                 Methane 
                 −161.5  
               
               
                   
                 Ethane 
                 −88.6 
               
               
                   
                 Propane 
                 −42.1 
               
               
                   
                 Butanes 
                  −6.0 
               
               
                   
                 Light Naphtha 
                 36-90 
               
               
                   
                 Mid Naphtha 
                  90-160 
               
               
                   
                 Heavy Naphtha 
                 160-205 
               
               
                   
                 Light Gas Oil 
                 205-260 
               
               
                   
                 Mid Gas Oil 
                 260-315 
               
               
                   
                 Heavy Gas Oil 
                 315-370 
               
               
                   
                 Light Vacuum Gas Oil 
                 370-430 
               
               
                   
                 Mid Vacuum Gas Oil 
                 430-480 
               
               
                   
                 Heavy Vacuum Gas Oil 
                 480-565 
               
               
                   
                 Vacuum Residue 
                 565+  
               
               
                   
                   
               
             
          
         
       
     
         [0012]    The yields, composition, physical and indicative properties of these crude oil fractions, where applicable, are then determined during the crude assay work-up calculations. Typical compositional and property information obtained in a crude oil assay is given in Table 2. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                 Property 
                   
               
               
                 Property 
                 Unit 
                 Type 
                 Fraction 
               
               
                   
               
             
             
               
                 Yield Weight and 
                 W % 
                 Yield 
                 All 
               
               
                 Volume % 
               
               
                 API Gravity 
                 ° 
                 Physical 
                 All 
               
               
                 Viscosity 
                 ° 
                 Physical 
                 Fraction boiling &gt;250° C. 
               
               
                 Kinematic @ 38° C. 
               
               
                 Refractive Index 
                 Unitless 
                 Physical 
                 Fraction boiling &lt;400° C. 
               
               
                 @ 20° C. 
               
               
                 Sulfur 
                 W % 
                 Composition 
                 All 
               
               
                 Mercaptan Sulfur, 
                 W % 
                 Composition 
                 Fraction boiling &lt;250° C. 
               
               
                 W % 
               
               
                 Nickel 
                 ppmw 
                 Composition 
                 Fraction boiling &gt;400° C. 
               
               
                 Nitrogen 
                 ppmw 
                 Composition 
                 All 
               
               
                 Flash Point, COC 
                 ° C. 
                 Indicative 
                 All 
               
               
                 Cloud Point 
                 ° C. 
                 Indicative 
                 Fraction boiling &gt;250° C. 
               
               
                 Pour Point, (Upper) 
                 ° C. 
                 Indicative 
                 Fraction boiling &gt;250° C. 
               
               
                 Freezing Point 
                 ° C. 
                 Indicative 
                 Fraction boiling &gt;250° C. 
               
               
                 Microcarbon 
                 W % 
                 Indicative 
                 Fraction boiling &gt;300° C. 
               
               
                 Residue 
               
               
                 Smoke Point, mm 
                 mm 
                 Indicative 
                 Fraction boiling between 
               
               
                   
                   
                   
                 150-250 
               
               
                 Octane Number 
                 Unitless 
                 Indicative 
                 Fraction boiling &lt;250° C. 
               
               
                 Cetane Index 
                 Unitless 
                 Indicative 
                 Fraction boiling between 
               
               
                   
                   
                   
                 150-400 
               
               
                 Aniline Point 
                 ° C. 
                 Indicative 
                 Fraction boiling &lt;520° C. 
               
               
                   
               
             
          
         
       
     
         [0013]    Due to the number of distillation cuts and the number of analyses involved, the crude oil assay work-up is both costly and time consuming. 
         [0014]    In a typical refinery, crude oil is first fractionated in the atmospheric distillation column to separate sour gas and light hydrocarbons, including methane, ethane, propane, butanes and hydrogen sulfide, naphtha (36°-180° C.), kerosene (180°-240° C.), gas oil (240°-370° C.) and atmospheric residue (&gt;370° C.). The atmospheric residue from the atmospheric distillation column is either used as fuel oil or sent to a vacuum distillation unit, depending on the configuration of the refinery. The principal products obtained from vacuum distillation are vacuum gas oil, comprising hydrocarbons boiling in the range 370°-520° C., and vacuum residue, comprising hydrocarbons boiling above 520° C. The crude assay data help refiners to understand the general composition of the crude oil fractions and properties so that the fractions can be processed most efficiently and effectively in an appropriate refining unit. 
         [0015]    In the field of organic chemistry, UV-visible spectrophotometry, which deals with electronic transitions within molecules, has traditionally provided unique information about aromatic and heteroaromatic compounds which absorb strongly in the UV region (200 nm-400 nm). Despite this and owing to the complex molecular nature of crude oil, UV-visible spectra of these oils are often described as featureless, poorly defined spectra. 
         [0016]    New rapid and direct methods to help better understand crude oil composition and properties from the analysis of whole crude oil will save producers, marketers, refiners and/or other crude oil users substantial expense, effort and time. Therefore, a need exists for an improved system and method for determining properties of crude oil fractions from different sources and classifying the crude oil fractions based on their boiling point characteristics and/or properties. 
       SUMMARY OF THE INVENTION 
       [0017]    Systems and methods are provided for characterizing samples of crude oil based on an index derived from the UV visible spectra and gravity. The wavelength maxima of known aromatic compounds and components are evaluated and extracted from the UV spectra of crude oils, which can be used to formulate and assign indices for the aromatic content of the crude oil. Properties of the oil including API gravity, sulfur content, and other selected characteristics that define the quality and nature of the constituent products, are assigned as a function of these indices. Importantly, this information can be obtained relatively rapidly and inexpensively from a UV-visible scan as compared to conventional assay methods described above. 
         [0018]    In the method and system herein, a crude oil ultraviolet visible index (which will be referred to for convenience as “CUVISI”) is calculated and assigned. CUVISI is used as a basis for further calculations upon which the crude oil can be classified. API gravity and/or aromaticity are also calculated and assigned from the CUVISI. CUVISI or API gravity can be used to characterize the sample as extra heavy gravity, heavy gravity, medium gravity, light gravity, or super light gravity crude oil. Aromaticity, which is a measure of the percentage of the aromatic carbon atoms present in the sample, can also be used to characterize the crude oil sample. The correlations will provide for the necessary characterization of the nature of crude oils without fractionation/distillation typically required for the crude oil assays. The method and system will enable producers, marketers and refiners to benchmark the oil quality and valuate the oil without performing the customary extensive and time-consuming crude oil assays. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0019]    Further advantages and features of the present invention will become apparent from the following detailed description of the invention when considered with reference to the accompanying drawings, in which: 
           [0020]      FIG. 1  is a graphic plot of typical ultraviolet visible spectroscopy data for a crude oil sample solution prepared as described herein; 
           [0021]      FIG. 2  is a process flow diagram of steps carried out to characterize the API gravity of a crude oil sample, using the system and method herein; and 
           [0022]      FIG. 3  is a block diagram of a component of a system for implementing the invention, according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0023]    In the system and method herein, spectra are obtained by a suitable known or to be developed UV-visible spectrophotometry techniques UV-visible spectrophotometry is carried out on a sample of crude oil according to the method and system herein to provide unique information about aromatic and heteroaromatic compounds which absorb strongly in the UV region (200 nm-400 nm). Specific individual aromatic compounds and components have maxima at well-defined wavelengths. Wavelength maxima of known aromatic compounds and components are evaluated and extracted from the UV spectra of crude oils. These maxima are used to formulate indices for the aromatic content of the crude oil. These indices can be used to assign properties to the oil, e.g., API gravity, sulfur content, and other selected characteristics that define the quality and nature of the constituent products. According to the provided method and system, this information is obtained relatively rapidly and inexpensively from a UV-visible scan as compared to the conventional assay methods. 
         [0024]    The system and method is applicable for naturally occurring hydrocarbons derived from crude oils, bitumens, heavy oils, shale oils and from refinery process units including hydrotreating, hydroprocessing, fluid catalytic cracking, coking, and visbreaking or coal liquefaction. 
         [0025]      FIG. 2  shows a process flowchart in a method according to one embodiment herein. Crude oil samples were prepared and analyzed by ultraviolet visible spectrophotometry between 200-500 nm, in certain embodiments between 220-400 nm. In step  210 , a crude oil sample is weighed. 
         [0026]    In step  220 , solutions are prepared by dissolving a sample of the crude oil in a two-part solvent system of a paraffinic solvent having from 5-20 carbon atoms and a polar solvent., e.g., at a ratio of 90:10% v/v. In certain embodiments, effective paraffinic solvents include iso-octane In certain embodiments, effective polar solvents include dichloromethane. 
         [0027]    The use of a polar solvent prevents precipitation of asphaltenes from the crude oil sample and ensures that all solutions are translucent for the measurement. The polar solvents are selected based on their Hildebrand solubility factors or their two-dimensional solubility parameters. The overall Hildebrand solubility factor is a well known measure of polarity and has been calculated for numerous compounds. See, for example, the Journal of Paint Technology, Vol. 39, No. 505 (February 1967). The solvents can also be described by their two-dimensional solubility parameter. See, for example, I. A. Wiehe, “Polygon Mapping with Two-Dimensional Solubility Parameters”,  I &amp; EC Research,  34, 661-673 (1995). The complexing solubility parameter component, which describes the hydrogen bonding and electron donor-acceptor interactions, measures the interaction energy that requires a specific orientation between an atom of one molecule and a second atom of a different molecule. The field force solubility parameter, which describes the van der Waals and dipole interactions, measures the interaction energy of the liquid that is not destroyed by changes in the orientation of the molecules. 
         [0028]    The UV absorbance of the crude oil solutions is determined, for instance, in a conventional one cm quartz cell. The absorbance values of the samples are summed at predetermined increments (e.g., even numbers, odd number, or increments of any number) between a predetermined range, e.g., between 200-500 nm, in certain embodiments between 220-400 nm to calculate the characterization index. 
         [0029]    In step  230 , one or more samples of crude oil in dilute solution are analyzed by UV-visible spectrophotometry over the wavelengths 200-500 nm, in certain embodiments 220-400 nm. 
         [0030]    In step  240 , the mass and spectra data are entered into a computer. In step  250 , the CUVISI is calculated. 
         [0031]    Equation (1) shows a crude oil ultraviolet visible index, CUVISI. 
         [0000]    
       
         
           
             
               
                 
                   CUVISI 
                   = 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         L 
                       
                       H 
                     
                      
                     
                         
                     
                      
                     
                       ( 
                       
                         
                           
                             Absorbance 
                             
                               ( 
                               
                                 Ni 
                                 - 
                                 220 
                               
                               ) 
                             
                           
                           / 
                           x 
                         
                         * 
                         10 
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0032]    where: 
         [0033]    Absorbance=absorbance value of the prepared crude oil sample solution at a specific wavelength over the range L to H at intervals of N, whereby in certain embodiments L is between about 200 nm and 220 nm and H is between 400 nm and 500 nm, and N is between 1 and 3, and x is the weight of the sample used, in milligrams. 
         [0034]    In one embodiment, in step  260  the sample is then characterized as follows: 
         [0035]    For CUVISI≧115, the sample is extra heavy gravity crude oil; 
         [0036]    For 100≦CUVISI&lt;115, the sample is heavy gravity crude oil; 
         [0037]    For 80≦CUVISI&lt;100, the sample is medium gravity crude oil; 
         [0038]    For 50≦CUVISI&lt;80, the sample is light gravity crude oil; and 
         [0039]    For CUVISI&lt;50, the sample is super light gravity crude oil. 
         [0040]    In another embodiment, in step  270  the API gravity of the sample is derived from the CUVISI, and the API gravity can also be used to characterize the sample. The API gravity value is calculated in step  280  as follows: 
         [0000]      API Gravity= X 1 API *CUVISI 2   X 2 API *CUVISI+ K   API    (2)
 
         [0041]    where X1 API , X2 API  and K API  are constants that are developed using linear regression techniques. 
         [0042]    In certain embodiments, the sample can be characterized as follows: 
         [0043]    For API Gravity≦20, the sample is extra heavy gravity crude oil; 
         [0044]    For 20&lt;API Gravity&lt;27, the sample is heavy gravity crude oil; 
         [0045]    For 27≦API Gravity&lt;34, the sample is medium gravity crude oil; 
         [0046]    For 34≦API Gravity&lt;40, the sample is light gravity crude oil; and 
         [0047]    For API Gravity≧40, the sample is super light gravity crude oil. 
         [0048]    In another embodiment, the aromaticity of the sample can be derived from the CUVISI and used to further characterize the sample. 
         [0000]      Aromaticity= X 1 AR *CUVISI 2   +X 2 AR *CUVISI+ K   AR    (3)
 
         [0049]    where X1 AR , X2 AR  and K AR  are constants that are developed using linear regression techniques. 
         [0050]    In certain embodiments, the sample can be characterized as follows: 
         [0051]    For Aromaticity&gt;10, the sample is aromatic; 
         [0052]    For Aromaticity≦10, the sample is paraffinic/naphthenic. 
         [0053]    An exemplary block diagram of a computer system  300  by which indicative property calculation modules can be implemented is shown in  FIG. 3 . Computer system  300  includes a processor  310 , such as a central processing unit, an input/output interface  320  and support circuitry  330 . In certain embodiments, where the computer  300  requires direct human interaction, a display  340  and an input device  350  such as a keyboard, mouse or pointer are also provided. The display  340 , input device  350 , processor  310 , input/output interface  320  and support circuitry  330  are shown connected to a bus  360  which also connects to a memory unit  370 . Memory  370  includes program storage memory  380  and data storage memory  390 . Note that while computer  300  is depicted with the direct human interface components of display  340  and input device  350 , programming of modules and importation and exportation of data can also be accomplished over the interface  320 , for instance, where the computer  300  is connected to a network and the programming and display operations occur on another associated computer, or via a detachable input device, as are well known in the art for interfacing programmable logic controllers. 
         [0054]    Program storage memory  380  and data storage memory  390  can each comprise volatile (RAM) and non-volatile (ROM) memory units and can also comprise hard disk and backup storage capacity, and both program storage memory  380  and data storage memory  390  can be embodied in a single memory device or separated in plural memory devices. Program storage memory  380  stores software program modules and associated data, and in particular stores a crude oil UV visible index (CUVISI) calculation module and an API gravity characterization module that performs its calculations based upon the CUVISI. Data storage memory  390  stores data used and/or generated by the one or more modules of the present system, including mass of the oil sample, UV absorbance data or portions thereof used by the one or more modules of the present system, and calculated data generated by the one or more modules of the present system. 
         [0055]    The calculated and assigned results in accordance with the systems and methods herein are displayed, audibly outputted, printed, and/or stored to memory for use as described herein. 
         [0056]    It is to be appreciated that the computer system  300  can be any general or special purpose computer such as a personal computer, minicomputer, workstation, mainframe, a dedicated controller such as a programmable logic controller, or a combination thereof. While the computer system  300  is shown, for illustration purposes, as a single computer unit, the system can comprise a group/farm of computers which can be scaled depending on the processing load and database size, e.g., the total number of samples that are processed and results maintained on the system. The computer system  300  can serve as a common multi-tasking computer. 
         [0057]    The computing device  300  preferably supports an operating system, for example, stored in program storage memory  390  and executed by the processor  310  from volatile memory. According to the present system and method, the operating system contains instructions for interfacing the device  300  to the calculation module(s). According to an embodiment of the invention, the operating system contains instructions for interfacing computer system  300  to the Internet and/or to private networks. 
       EXAMPLE 
       [0058]    Crude oil samples were prepared and analyzed by ultraviolet visible spectrophotometry between 220-400 nm using a Jasco V-530 double beam spectrophotometer. The samples were weighed. Solutions were prepared by dissolving a milligram-sized sample of the crude oil in a two-part solvent system consisting of a paraffinic solvent having from 5-20 carbon atoms, preferred solvent being iso-octane, and a polar solvent, dichloromethane, at a ratio of 90:10% v/v. Dilute solutions were prepared by dissolving the oil in a two-part solvent system consisting of iso-octane (90 mL) and dichloromethane (10 mL). In a typical solution preparation, one drop (˜6 mg±3 mg) of crude oil from a pre-weighed syringe is added to 100 mL of the solvent solution. The syringe is reweighed to determine the exact amount of the crude oil added. Each crude oil sample is analyzed at two concentration levels, e.g., 60 mg/L and 120 mg/L. 
         [0059]    The UV absorbance of the crude oil solutions is determined in a conventional one cm quartz cell. Solutions are analyzed in 1 cm quartz cells using a Jasco V-530 double beam spectrophotometer over the wavelengths 220-400 nm. The absorbance values of the samples, normalized to 10 mg/L, are summed every even-numbered wavelength between 220 to 400 nm to calculate the characterization index. 
         [0060]    The instrument is allowed to warm up for 30 minutes prior to analysis and is auto-zeroed without cells in both sample and reference beams. The reference cell is filled with the solvent mixture then placed in the reference beam. Solutions of the crude oil sample solutions prepared as described above are successively placed in a clean quartz sample cell and the spectra are recorded against the reference solvent blank. The spectra are recorded at a scan speed of 100 nm/min with a fast response time. 
         [0061]    Table 3 is an example of a tabulation of values for the sample of Arab heavy crude oil in the wavelength range 220-400 nm. This data is depicted in the curve of  FIG. 1 . 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Absorbances of Arab Heavy Crude Oils at 
               
               
                 Wavelength Ranging from 220-400 nm at 2 nm Interval 
               
             
          
           
               
                   
                 Wave 
                 Absor., 
               
               
                   
                 Length 
                 nm 
               
               
                   
                   
               
             
          
           
               
                   
                 220 
                 3.076 
               
               
                   
                 222 
                 2.841 
               
               
                   
                 224 
                 2.778 
               
               
                   
                 226 
                 2.753 
               
               
                   
                 228 
                 2.735 
               
               
                   
                 230 
                 2.708 
               
               
                   
                 232 
                 2.663 
               
               
                   
                 234 
                 2.591 
               
               
                   
                 236 
                 2.486 
               
               
                   
                 238 
                 2.361 
               
               
                   
                 240 
                 2.236 
               
               
                   
                 242 
                 2.113 
               
               
                   
                 244 
                 1.994 
               
               
                   
                 246 
                 1.891 
               
               
                   
                 248 
                 1.811 
               
               
                   
                 250 
                 1.755 
               
               
                   
                 252 
                 1.719 
               
               
                   
                 254 
                 1.698 
               
               
                   
                 256 
                 1.689 
               
               
                   
                 258 
                 1.688 
               
               
                   
                 260 
                 1.685 
               
               
                   
                 262 
                 1.673 
               
               
                   
                 264 
                 1.649 
               
               
                   
                 266 
                 1.621 
               
               
                   
                 268 
                 1.59 
               
               
                   
                 270 
                 1.552 
               
               
                   
                 272 
                 1.502 
               
               
                   
                 274 
                 1.447 
               
               
                   
                 276 
                 1.39 
               
               
                   
                 278 
                 1.341 
               
               
                   
                 280 
                 1.297 
               
               
                   
                 282 
                 1.255 
               
               
                   
                 284 
                 1.218 
               
               
                   
                 286 
                 1.183 
               
               
                   
                 288 
                 1.15 
               
               
                   
                 290 
                 1.121 
               
               
                   
                 292 
                 1.096 
               
               
                   
                 294 
                 1.067 
               
               
                   
                 296 
                 1.036 
               
               
                   
                 298 
                 1.006 
               
               
                   
                 300 
                 0.981 
               
               
                   
                 302 
                 0.962 
               
               
                   
                 304 
                 0.935 
               
               
                   
                 306 
                 0.905 
               
               
                   
                 308 
                 0.871 
               
               
                   
                 310 
                 0.839 
               
               
                   
                 312 
                 0.809 
               
               
                   
                 314 
                 0.783 
               
               
                   
                 316 
                 0.758 
               
               
                   
                 318 
                 0.735 
               
               
                   
                 320 
                 0.714 
               
               
                   
                 322 
                 0.696 
               
               
                   
                 324 
                 0.678 
               
               
                   
                 326 
                 0.662 
               
               
                   
                 328 
                 0.645 
               
               
                   
                 330 
                 0.627 
               
               
                   
                 332 
                 0.609 
               
               
                   
                 334 
                 0.59 
               
               
                   
                 336 
                 0.57 
               
               
                   
                 338 
                 0.551 
               
               
                   
                 340 
                 0.532 
               
               
                   
                 342 
                 0.518 
               
               
                   
                 344 
                 0.502 
               
               
                   
                 346 
                 0.486 
               
               
                   
                 348 
                 0.472 
               
               
                   
                 350 
                 0.458 
               
               
                   
                 352 
                 0.445 
               
               
                   
                 354 
                 0.432 
               
               
                   
                 356 
                 0.418 
               
               
                   
                 358 
                 0.406 
               
               
                   
                 360 
                 0.394 
               
               
                   
                 362 
                 0.382 
               
               
                   
                 364 
                 0.37 
               
               
                   
                 366 
                 0.359 
               
               
                   
                 368 
                 0.349 
               
               
                   
                 370 
                 0.34 
               
               
                   
                 372 
                 0.332 
               
               
                   
                 374 
                 0.323 
               
               
                   
                 376 
                 0.316 
               
               
                   
                 378 
                 0.309 
               
               
                   
                 380 
                 0.303 
               
               
                   
                 382 
                 0.299 
               
               
                   
                 384 
                 0.294 
               
               
                   
                 386 
                 0.292 
               
               
                   
                 388 
                 0.29 
               
               
                   
                 390 
                 0.289 
               
               
                   
                 392 
                 0.288 
               
               
                   
                 394 
                 0.287 
               
               
                   
                 396 
                 0.283 
               
               
                   
                 398 
                 0.276 
               
               
                   
                 400 
                 0.268 
               
               
                   
                   
               
             
          
         
       
     
         [0062]    Equation (1) shows a crude oil ultraviolet visible index, CUVISI. 
         [0000]    
       
         
           
             
               
                 
                   
                     CUVISI 
                     = 
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           220 
                         
                         400 
                       
                        
                       
                           
                       
                        
                       
                         ( 
                         
                           
                             
                               Absorbance 
                               
                                 ( 
                                 
                                   
                                     2 
                                      
                                     
                                         
                                     
                                      
                                     i 
                                   
                                   - 
                                   220 
                                 
                                 ) 
                               
                             
                             / 
                             x 
                           
                           * 
                           10 
                         
                         ) 
                       
                     
                   
                   ; 
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0063]    where: 
         [0064]    Absorbance=absorbance value of the prepared crude oil sample solution at a specific wavelength over the range 220 nm to 400 nm at 2 nm intervals; 
         [0065]    x=the weight of the sample used, in mg. 
         [0066]    The data recorded in Table 3 produces a CUVISI of 98.697. This classifies this crude oil as medium gravity crude oil based on the characterizations above. 
         [0067]    Exemplary constants for equations (2) and (3) are developed by linear regression, and are given as:
       X1 API =−0.00176   X2 API =−0.00689   K API =45.743   X1 AR =−0.0000309999   X2 AR =0.127188   K AR =6.36006       
 
         [0074]    Using these constants for the example provided in Table 3, for which CUVISI was determined to be 98.697: 
         [0000]    The API Gravity is calculated as: 
         [0075]    API Gravity=−0.00176*(98.697) 2 −0.00689*(98.697)+45.743=27.9, which also identifies it as medium crude oil. 
         [0000]    The Aromaticity value is calculated as: 
         [0076]    Aromaticity=−0.0000309999*(98.697) 2 +0.127188*(98.697)+6.36006=18.6, which identifies the sample as aromatic. 
         [0077]    In alternate embodiments, the present invention can be implemented as a computer program product for use with a computerized computing system. Those skilled in the art will readily appreciate that programs defining the functions of the present invention can be written in any appropriate programming language and delivered to a computer in any form, including but not limited to: (a) information permanently stored on non-writeable storage media (e.g., read-only memory devices such as ROMs or CD-ROM disks); (b) information alterably stored on writeable storage media (e.g., floppy disks and hard drives); and/or (c) information conveyed to a computer through communication media, such as a local area network, a telephone network, or a public network such as the Internet. When carrying computer readable instructions that implement the present invention methods, such computer readable media represent alternate embodiments of the present invention. 
         [0078]    As generally illustrated herein, the system embodiments can incorporate a variety of computer readable media that comprise a computer usable medium having computer readable code means embodied therein. One skilled in the art will recognize that the software associated with the various processes described can be embodied in a wide variety of computer accessible media from which the software is loaded and activated. Pursuant to In re Beauregard, 35 USPQ2d 1383 (U.S. Pat. No. 5,710,578), the present invention contemplates and includes this type of computer readable media within the scope of the invention. In certain embodiments, pursuant to In re Nuijten, 500 F.3d 1346 (Fed. Cir. 2007) (U.S. patent application Ser. No. 09/211,928), the scope of the present claims is limited to computer readable media, wherein the media is both tangible and non-transitory. 
         [0079]    The system and method of the present invention have been described above and with reference to the attached figure; however, modifications will be apparent to those of ordinary skill in the art and the scope of protection for the invention is to be defined by the claims that follow.