Measuring and testing – Gas analysis – Gas chromatography
Reexamination Certificate
1999-12-21
2001-05-29
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
Gas chromatography
C073S023370, C073S023400, C073S061520, C436S161000, C210S656000, C095S082000, C095S086000
Reexamination Certificate
active
06237396
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an integrated analytical process for characterization of hydrocarbons in a petroleum product, in distillation fractions, by simulated distillation.
The process according to the invention can be used in many fields, notably for characterization of reservoir fluids or of petrochemical refining products.
BACKGROUND OF THE INVENTION
No analytical technique currently allows to directly characterize a petroleum product having a wide boiling range. Fractional distillation is necessary in order to apply to each fraction standard analytical methods or methods described in the literature. This procedure is very long and expensive, and it can lead to errors.
Considerable work and many publications deal with GC simulated distillation, GC-GC and GC-LC couplings and associated characterization methods. Examples thereof are:
Simulated distillation:
ASTM D 5307—1992; <<Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography>>, American Society for Testing and Materials;
J. P. Durand, et al : <<Simulated Distillation Methods for Petroleum Fractions with Minimal Residue in the Boiling range of 35-700° C.>>, J. of Chromatographic Science, Vol.36, September 1998.
Couplings:
There are standard detailed analysis methods for the light fraction.
ASTM D 5134—1990, <<Detailed Analysis of Petroleum Naphthas Through n-Nonane by Capillary Gas Chromatography>>, American Society for Testing and Materials;
NF
07-086,
<<Détermination des teneurs en families chimiques d'hydrocarbures dans les essences pour moteurs automobiles à partir de l'analyse détaillée>>, Association Française de normalisation, Paris La Défense, Cédex.
The use of GC-GC coupling only for analysis of the light fraction without distillation of the sample with these methods is also described by:
J. P. Durand et al: <<Direct and Automatic Capillary GC Analysis for Molecular Weight Determination and Distribution, in Crude Oils and Condensates up to C20>>, J. High Resolut. Chromatogr., 12, 1989, 230-234;
J. P. Durand et al: <<Detailed Characterization of Petroleum Products with Capillary GC analyzers>>, Analysis, 1995, 23, 481-483.
There are also many publications on LC-GC coupling. The interfaces allowing on-line coupling between LC and GC are described by K. Grob in <<On-line coupled LC-GC>>, Hüthig Ed., 1991.
As for characterization of middle and heavy fractions, the following examples can be cited:
G. W. Kelly et al: <<The use of combined LC-GC for the analysis of fuel products: a review>>, JHRC, Vol.17, 1994, 390-397;
A. Trisciani et al: <<Characterization of fuel samples by on-line LC-GC with automatic group-type separation of hydrocarbons>>, JHRC, Vol.17, 1994, 452-456;
K. J. Welch et al: <<Analysis of fossil fuel fractions by on-line coupled microcolumn HPLC-capillary GC-MS>>, HRC, 15, 1992, 171-175;
C. Ostman et al: <<On-line liquid chromatography-gas chromatography for automated clean-up and analysis of polycyclic aromatic hydrocarbons>>, HRC, 15, 1992, 437-443.
SUMMARY OF THE INVENTION
The integrated analysis process for characterization of a hydrocarbon sample in distillation fractions according to the invention is characterized in that simulated distillation by gas chromatography is carried out with a layout of two interconnected columns, so as to separate the sample into at least a first light fraction and at least another, heavier fraction, said fractions are collected after separation on retention means, each light fraction on the one hand and each of the heavier fractions on the other hand is analysed in detail by connecting up the corresponding retention means respectively with one or more gas chromatography units and with a combined liquid and gas chromatography unit.
The integrated analysis system for implementing the process comprises:
a first gas chromatography device laid-out to perform separation of the sample into at least a first light fraction and at least another, heavier fraction,
retention means for collecting said fractions after separation,
one or more gas chromatography columns for detailed analysis of each light fraction, by connecting up the corresponding retention means, and
a combined liquid and gas chromatography unit for analysing each one of the heavier fractions by connecting up and flushing of the corresponding retention means.
According to an embodiment, the first gas chromatography device comprises a capillary precolumn and a capillary column connected in series, a first multiway valve for connecting the outlet of the precolumn to a first retention means for the heavier phase, and a second multiway valve cooperating with the first valve and a source of gaseous fluid under pressure for selectively displacing at least a second, lighter phase out of the capillary column into at least a second retention means for this second phase (two for example, one for a light fraction and at least another one for a middle fraction).
The combined liquid and gas chromatography unit comprises for example a liquid chromatography column, a series of valves for intermittently connecting a retention means intended for a heavier fraction with solvent pumping means, with a liquid chromatography column and a gas chromatography unit, by means of a LC/GC type interface.
According to an embodiment, the series of valves comprises a first valve suited, in a first position, to communicate the pumping means with the liquid chromatography column and, simultaneously, a retention means with a solvent injection means, and, in a second position, to connect in series, by means of a second valve, the pumping means, the retention means, said liquid chromatography column and gas chromatography unit (GC).
According to an embodiment, gas chromatography unit (GC) comprises for example a retention-gap column for evaporation of the solvent, an analytical precolumn, evaporation and discharge means arranged on either side of this precolumn for solvent removal, and an analytical column associated with a FID detector.
An ultraviolet detector can be used for detection of the fractions transferred to said chromatography unit.
The analysis process according to the invention is advantageous because it allows, from a sample taken under pressure, without previous expansion, via a pressure injection valve, to obtain better characterization of fluids, notably of the heavy fraction of condensate gases (HT/HT fluids), which is essential for accurate calculation of their thermodynamic behaviour. It allows to obtain very complete analytical characterization of fluids, with a considerable saving in time in relation to conventional fractional distillation methods, and therefore with cost reduction. Furthermore, this result can be obtained with reduced samples, entirely compatible with the relatively small quantities that are generally available during preliminary reservoir effluent surveys.
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Durand JP, Analusis (Dec. 1995), 23(10), p. 481-3.
JP Durant et al Simulated Distillation Methods For Petroleum Fractions With Minimal Residue In the Boiling Range Of 35-700 Degrees' Journal of Chromatographic Science, vol. 36, No. 9, Sep. 1998 pp. 431-434.
Durand Jean-Pierre
Robert Eric
Ruffier-Meray Veronique
Antonelli Terry Stout & Kraus LLP
Cygan Michael
Institut Francais du Pe'trole
Williams Hezron
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