CHARACTERIZATION OF CRUDE OIL BY HIGH PRESSURE LIQUID CHROMATOGRAPHY

Abstract

A system and a method are provided for calculating one or more indicative properties, e.g., one or more of the cetane number, octane number, pour point, cloud point and aniline point of oil fractions, from the density and high pressure liquid chromatography (HPLC) data of a sample of the crude oil.

Claims

1. A system for assigning an indicative property of to a fraction of an oil sample, based upon high pressure liquid chromatography (HPLC) data, the system comprising: a non-volatile memory device that stores calculation modules and data, the data including HPLC data indicative of analyte retention time; a processor coupled to the memory; a first calculation module that calculates the saturates and aromatic composition of the gas oil fraction from the HPLC data; and a second calculation module that calculates and assigns the indicative property as a function of the saturates and aromatic composition and a density of the oil sample.

2. A system for assigning an indicative property of to a fraction of an oil sample comprising: a high pressure liquid chromatography (HPLC) system that outputs HPLC data; a non-volatile memory device that stores calculation modules and data, the data including outputted HPLC data indicative of analyte retention time; a processor coupled to the memory; a first calculation module that calculates the saturates and aromatic composition of the gas oil fraction from the HPLC data; and a second calculation module that calculates and assigns the indicative property as a function of the saturates and aromatic composition and a density of the oil sample.

3. A method for operating a computer to assign an indicative property to a fraction of an oil sample based upon high pressure liquid chromatography (HPLC) data, the method comprising: entering into the computer a density of the oil sample and HPLC data indicative of analyte retention time; calculating and assigning the saturates and aromatic composition of the gas oil fraction from the HPLC data; and calculating and assigning the indicative property as a function of the saturates and aromatic composition and a density of the oil sample.

4. A method for operating a computer to assign an indicative property to a fraction of an oil sample comprising: obtaining high pressure liquid chromatography (HPLC) data from a HPLC system, the HPLC data indicative of analyte retention time, obtaining a density of the oil sample; entering into the computer the density of the oil sample and the HPLC data; calculating and assigning the saturates and aromatic composition of the gas oil fraction from the HPLC data; and calculating and assigning the indicative property as a function of the saturates and aromatic composition and a density of the oil sample.

5. The method of claim 3 wherein the oil sample is crude oil.

6. The method of claim 3 wherein the oil sample is obtained from an oil well, stabilizer, extractor, or distillation tower.

7. The method of claim 3 wherein the indicative property is a cetane number.

8. The method of claim 3 wherein the indicative property is a pour point.

9. The method of claim 3 wherein the indicative property is a cloud point.

10. The method of claim 3 wherein the indicative property is an aniline point.

11. The method of claim 3 wherein the indicative property is an octane number.

12. The method of claim 3 wherein plural indicative properties are calculated including at least two indicative properties selected from the group consisting of cetane number, pour point, cloud point, aniline point and octane number.

13. The method of claim 3 wherein the indicative property is of a gas oil fraction boiling in the nominal range 180-370° C.

14. The method of claim 3 wherein the indicative property is of a gasoline fraction boiling in the nominal range 36-180° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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:

[0023] FIG. 1 is a graphic plot of typical HPLC data for a typical crude oil sample;

[0024] FIG. 2 is a block diagram of a method in which an embodiment herein is implemented;

[0025] FIG. 3 is a schematic block diagram of modules of an embodiment herein; and

[0026] FIG. 4 is a block diagram of a computer system in which an embodiment herein is implemented.

DETAILED DESCRIPTION OF INVENTION

[0027] A system and method is provided for determining one or more indicative properties of a hydrocarbon sample. Indicative properties (e.g., one or more of cetane number, pour point, cloud point and aniline point) of a gas oil fraction in crude oil samples are assigned as a function of density and HPLC measurement of crude oils.

[0028] HPLC is carried out on oil samples. HPLC operates in various modes, such as normal phase, reversed phase, ion exchange, gel permeation, and hydrophilic interaction, which are defined by the combination of stationary phases and mobile phases. In certain embodiments herein, normal phase chromatography is used; where the stationary phase is polar and the mobile phase is non-polar. HPLC typically utilizes different types of stationary phases for different applications, a pump that moves the mobile phase(s) and analytes through the column, and a detector to provide a characteristic retention time for the analytes. The detector may also provide additional information related to the analytes. Analyte retention time varies depending on the strength of its interactions with the stationary phase, the ratio/composition of solvent(s) used, and the flow rate of the mobile phase.

[0029] The correlations provide information about gas oil and/or naphtha indicative properties without fractionation/distillation (crude oil assays) and will help producers, refiners, and marketers to benchmark the oil quality and, as a result, valuate the oils without performing the customary extensive and time-consuming crude oil assays. The currently used crude oil assay method is costly in terms of money and time. It costs about $50,000 US and takes two months to complete one assay. With the method and system herein, the crude oil can be classified as a function of HPLC data, and thus decisions can be made for purchasing and/or processing.

[0030] The systems and methods are 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. Samples can be obtained from various sources, including an oil well, stabilizer, extractor, or distillation tower.

[0031] In the system and method herein, a chromatogram is obtained by a suitable known or to be developed HPLC. FIG. 2 shows a process flowchart in a method 200 according to one embodiment herein. A solution of an oil sample is prepared, step 205. The prepared solution is injected into HPLC equipment, step 210. In step 215, the peaks are integrated to obtain a relevant percentage of each peak, e.g., saturates, aromatics containing 1-ring molecules, aromatics containing 2-ring molecules and aromatics containing 3 or more aromatic rings.

[0032] FIG. 3 illustrates a schematic block diagram of modules in accordance with an embodiment of the present invention, system 300. Density and raw data receiving module 310 receives the density of a sample of crude oil and high pressure liquid chromatography (HPLC) data derived from the crude oil. Peak integrating module 315 integrates the peaks derived from the HPLC and calculates the fraction of saturates, fraction of aromatics containing 1-ring molecules and fraction of aromatics containing 2-ring molecules.

[0033] Cetane number calculation module 335 derives the cetane number for the gas oil fraction as a function of the density of the sample, the fraction of saturates, the fraction of aromatics containing 1-ring molecules, and the fraction of aromatics containing 2-ring molecules.

[0034] Pour point calculation module 340 derives the pour point for the gas oil fraction as a function of the density of the sample, the fraction of saturates, the fraction of aromatics containing 1-ring molecules, and the fraction of aromatics containing 2-ring molecules.

[0035] Cloud point calculation module 345 derives the cloud point for the gas oil fraction as a function of the density of the sample, the fraction of saturates, the fraction of aromatics containing 1-ring molecules, and the fraction of aromatics containing 2-ring molecules.

[0036] Aniline point calculation module 350 derives the aniline point for the gas oil fraction as a function of the density of the sample, the fraction of saturates, the fraction of aromatics containing 1-ring molecules, and the fraction of aromatics containing 2-ring molecules.

[0037] Octane number calculation module 355 derives the octane number for the gasoline fraction as a function of the density of the sample, the fraction of saturates, the fraction of aromatics containing 1-ring molecules, and the fraction of aromatics containing 2-ring molecules.

[0038] FIG. 4 shows an exemplary block diagram of a computer system 400 in which the partial discharge classification system of the present invention can be implemented. Computer system 400 includes a processor 420, such as a central processing unit, an input/output interface 430 and support circuitry 440. In certain embodiments, where the computer system 400 requires a direct human interface, a display 410 and an input device 450 such as a keyboard, mouse or pointer are also provided. The display 410, input device 450, processor 420, and support circuitry 440 are shown connected to a bus 490 which also connects to a memory 460. Memory 460 includes program storage memory 470 and data storage memory 480. Note that while computer system 400 is depicted with direct human interface components display 410 and input device 450, programming of modules and exportation of data can alternatively be accomplished over the input/output interface 430, for instance, where the computer system 400 is connected to a network and the programming and display operations occur on another associated computer, or via a detachable input device as is known with respect to interfacing programmable logic controllers.

[0039] Program storage memory 470 and data storage memory 480 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 470 and data storage memory 480 can be embodied in a single memory device or separated in plural memory devices. Program storage memory 470 stores software program modules and associated data, and in particular stores a density and raw data receiving module 310, peak integrating module 315, cetane number calculation module 330, pour point calculation module 340, cloud point calculation module 345, aniline point calculation module 350, and octane number calculation module 355. Data storage memory 480 stores results and other data generated by the one or more modules of the present invention.

[0040] 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.

[0041] It is to be appreciated that the computer system 400 can be any 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 400 is shown, for illustration purposes, as a single computer unit, the system can comprise a group of computers which can be scaled depending on the processing load and database size.

[0042] Computer system 400 preferably supports an operating system, for example stored in program storage memory 470 and executed by the processor 420 from volatile memory. According to the present system and method, the operating system contains instructions for interfacing the device 400 to the calculation module(s). According to an embodiment of the invention, the operating system contains instructions for interfacing computer system 400 to the Internet and/or to private networks.

Example

[0043] Crude oil samples were prepared and analyzed by HPLC according to the method 200 described below, and illustrated in FIG. 2.

[0044] In step 205, about 100 mg of crude oil sample is dissolved in 1 mL heptane. The solution is shaken thoroughly by a Vortex Mixer and allowed to stand for 10 minutes, after which it is filtered through a 0.45 μm Millipore filter in order to remove insoluble particles.

[0045] In step 210, the filtered sample is then directly injected into the HPLC equipment, consisting of a micro vacuum degasser, binary pump, column thermostat, auto-sampler and refractive index detector. The HPLC conditions maintained for this analysis are presented in the Table 3.

TABLE-US-00003 TABLE 3 Flow rate: 0.8 mL/min Detector: Refractive index detector, Optical unit temperature 30° C. Injection volume: 10 μL Run time: 40 minutes Forward flush 11.4 minute Back flush 11.4-30 minute Mobile phase: n-heptane Column storage: n-heptane Injector needle wash: n-heptane Column: LiChrospher NH.sub.2 (250 × 4.6 mm) Column temperature: 25° C.

[0046] As the chromatogram of FIG. 1 shows, four peaks are obtained. The area under these peaks are: A.sub.s, the peak area of saturates; A.sub.1, the peak area of 1-aromatic rings; A.sub.2, the peak area of 2-aromatic rings; and A.sub.3+, the peak area of 3+-aromatic rings.

[0047] In step 215, the peaks are manually integrated using Agilent ChemStation software, though any similar software may be used. The relevant percentage of each peak is reported as:

Fraction of saturates (SAT)=A.sub.S/(A.sub.S+A.sub.1+A.sub.2+A.sub.3+)  (1);

Fraction of aromatics containing 1-ring molecules (AROM-1R)=A.sub.1/(A.sub.S+A.sub.1+A.sub.2+A.sub.3+)  (2);

Fraction of aromatics containing 2-ring molecules (AROM-2R)=A.sub.2/(A.sub.S+A.sub.1+A.sub.2+A.sub.3+)  (3);

Fraction of aromatics containing 3 or more aromatic rings=A.sub.3+/(A.sub.S+A.sub.1+A.sub.2+A.sub.3+)  (4).

[0048] The indicative properties (e.g., the cetane number, pour point, cloud point and aniline point of the gas oil fraction boiling in the range 180-370° C. and octane number for gasoline fraction boiling in the range 36-180° C.) of the crude oil can be predicted from the density of whole crude oil and the group type composition (saturates, 1-, 2-ring aromatics) of crude oil, as determined by HPLC. That is,

Indicative Property=f(density.sub.crude oil, SAT.sub.crude oil, AROM-1R.sub.crude oil, AROM-2R.sub.crude oil)  (5);

[0049] Equations (6) through (9) show, respectively, the cetane number, pour point, cloud point and aniline point of gas oils boiling in the range 180-370° C., and equation (10) shows the octane number of gasoline boiling in the range 36-180° C. that can be predicted from the density (which is determined in step 230) and 1- and/or 2-ring aromatics composition of crude oils. Thus, in step 235, the cetane number is calculated as:

Cetane Number (CET)=K.sub.CET+X1.sub.CET*DEN+X2.sub.CET*SAT+X3.sub.CET*AROM-1R+X4.sub.CET*AROM-2R  (6);

[0050] In step 240, the pour point is calculated as:

Pour Point (PPT)=K.sub.PPT+X1.sub.PPT*DEN+X2.sub.PPT*SAT+X3.sub.PPT*AROM-1R+X4.sub.PPT*AROM-2R  (7)

[0051] In step 245, the cloud point is calculated as:

Cloud Point (CPT)=K.sub.CPT+X1.sub.CPT*DEN+X2.sub.CPT*SAT+X3.sub.CPT*AROM-1R+X4.sub.CPT*AROM-2R  (8)

[0052] In step 250, the aniline point is calculated as:

Aniline Point (AP)=K.sub.AP+X1.sub.AP*DEN+X2.sub.AP*SAT+X3.sub.AP*AROM-1R+X4.sub.AP*AROM-2R  (9)

[0053] In step 255, the octane number is calculated as:

Octane Number (ON)=K.sub.ON+X1.sub.ON*DEN+X2.sub.ON*SAT+X3.sub.ON*AROM-1R  (10) [0054] where: [0055] DEN=density of the crude oil sample; [0056] SAT=Fraction of saturates by HPLC; [0057] AROM-1R=Fraction of aromatics containing 1-ring molecules by HPLC; [0058] AROM-2R=Fraction of aromatics containing 2-ring molecules by HPLC; and [0059] K.sub.CET, X1.sub.CET-X4.sub.CET, K.sub.PPT, X1.sub.PPT-X4.sub.PPT, K.sub.CPT, X1.sub.CPT-X4.sub.CPT, K.sub.AP, X1.sub.AP-X4.sub.AP, K.sub.ON, X1.sub.ON-X3.sub.ON are constants that were developed using linear regression analysis of hydrocarbon data from HPLC, and which are given in Table 4.

TABLE-US-00004 TABLE 4 Cetane Octane Constants Number Pour Point Cloud Point Aniline Point Number K 272.6 355.3 265.2 234.3 273.4 X1 −220.8 −425.5 −317.9 −163.9 −230.8 X2 −79.3 −46.7 −25.0 −43.8 36.2 X3 5.9 22.4 5.8 −13.4 −138.9 X4 −3.3 60.4 37.0 −38.6 —

[0060] The following example is provided to demonstrate an application of equations (6) through (10). A sample of Arabian medium crude with a 15° C./4° C. density of 0.8828 Kg/l was analyzed by HPLC, using the described method. The HPLC composition was determined to be: Saturates=27.2 W %; 1-Ring Aromatics=18.6 W %; 2-Ring Aromatics 28.5 W %; and 3+-Ring Aromatics=25.7 W %.

[0061] Applying equation (6) and the constants from Table 4,

[00001]$\begin{array}{c}\mathrm{Cetane}.Math..Math.\mathrm{Number}.Math..Math.\left(C.Math..Math.E.Math..Math.T\right)=.Math.K_{\mathrm{CET}}+X.Math..Math.1_{\mathrm{CET}}*\mathrm{DEN}+X.Math..Math.2_{\mathrm{CET}}*\mathrm{SAT}+\\ .Math.X.Math..Math.3_{\mathrm{CET}}*\mathrm{AROM}-1.Math.R+X.Math..Math.4_{\mathrm{CET}}*\mathrm{AROM}-2.Math.R\\ =.Math.\left(272.6\right)+\left(-220.8\right).Math.\left(0.8828\right)+\left(-79.3\right).Math.\left(0.272\right)+\\ .Math.\left(5.9\right).Math.\left(0.186\right)+\left(-3.3\right).Math.\left(0.285\right)\\ =.Math.56.3\end{array}$

[0062] Applying equation (7) and the constants from Table 4,

[00002]$\begin{array}{c}\mathrm{Pour}.Math..Math.\mathrm{Point}.Math..Math.\left(P.Math..Math.P.Math..Math.T\right)=.Math.K_{\mathrm{PPT}}+X.Math..Math.1_{\mathrm{PPT}}*\mathrm{DEN}+X.Math..Math.2_{\mathrm{PPT}}*\mathrm{SAT}+\\ .Math.X.Math..Math.3_{\mathrm{PPT}}*\mathrm{AROM}-1.Math.R+X.Math..Math.4_{\mathrm{PPT}}*\mathrm{AROM}-2.Math.R\\ =.Math.\left(355.3\right)+\left(-425.5\right).Math.\left(0.8828\right)+\left(-46.7\right).Math.\left(0.272\right)+\\ .Math.\left(22.4\right).Math.\left(0.186\right)+\left(60.4\right).Math.\left(0.285\right)\\ =.Math.-12\end{array}$

[0063] Applying equation (8) and the constants from Table 4,

[00003]$\begin{array}{c}\mathrm{Cloud}.Math..Math.\mathrm{Point}.Math..Math.\left(\mathrm{CPT}\right)=.Math.K_{\mathrm{CPT}}+X.Math..Math.1_{\mathrm{CPT}}*\mathrm{DEN}+X.Math..Math.2_{\mathrm{CPT}}*\mathrm{SAT}+\\ .Math.X.Math..Math.3_{\mathrm{CPT}}*\mathrm{AROM}-1.Math.R+X.Math..Math.4_{\mathrm{CPT}}*\mathrm{AROM}-2.Math.R\\ =.Math.\left(265.2\right)+\left(-317.9\right).Math.\left(0.8828\right)+\left(-25.0\right).Math.\left(0.272\right)+\\ .Math.\left(5.8\right).Math.\left(0.186\right)+\left(37.0\right).Math.\left(0.285\right)\\ =.Math.-11\end{array}$

[0064] Applying equation (9) and the constants from Table 4,

[00004]$\begin{array}{c}\mathrm{Aniline}.Math..Math.\mathrm{Point}.Math..Math.\left(A.Math..Math.P\right)=.Math.K_{\mathrm{AP}}+X.Math..Math.1_{\mathrm{AP}}*\mathrm{DEN}+X.Math..Math.2_{\mathrm{AP}}*\mathrm{SAT}+\\ .Math.X.Math..Math.3_{\mathrm{AP}}*\mathrm{AROM}-1.Math.R+X.Math..Math.4_{\mathrm{AP}}*\mathrm{AROM}-2.Math.R\\ =.Math.\left(234.3\right)+\left(-163.9\right).Math.\left(0.8828\right)+\left(-43.8\right).Math.\left(0.272\right)+\\ .Math.\left(-13.4\right).Math.\left(0.186\right)+\left(-38.6\right).Math.\left(0.285\right)\\ =.Math.64\end{array}$

[0065] Applying equation (10) and the constants from Table 4,

[00005]$\begin{array}{c}\mathrm{Octane}.Math..Math.\mathrm{Number}.Math..Math.\left(O.Math..Math.N\right)=.Math.K_{\mathrm{ON}}+X.Math..Math.1_{\mathrm{ON}}*\mathrm{DEN}+X.Math..Math.2_{\mathrm{ON}}*\\ .Math.\mathrm{SAT}+X.Math..Math.3_{\mathrm{ON}}*\mathrm{AROM}-1.Math.R\\ =.Math.\left(273.4\right)+\left(-230.8\right).Math.\left(0.8828\right)+\\ .Math.\left(36.2\right).Math.\left(0.272\right)+\left(-138.9\right).Math.\left(0.186\right)\\ =.Math.54\end{array}$

[0066] 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.

[0067] 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.

[0068] 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.