1. Field of the Invention
The present invention relates to a method for measuring fractions of hydrocarbon fluids using optical spectroscopy.
2. Description of Related Art
It is often desirable for many reasons to characterize the compositions of hydrocarbon fluids, such as crude oil. For example, the behavior of a hydrocarbon fluid depends, at least in part, on the composition of the hydrocarbon fluid. Proper reservoir management utilizes data concerning pressure and temperature of the reservoir along with the composition of the hydrocarbon reservoir fluids. Moreover, the mixing of different hydrocarbon fluids during transportation and/or storage of hydrocarbon fluids can cause perturbation of the fluids system. For example, the presence of incompatible fluids can result in precipitation of solids and the deposition of such solids within transportation and/or storage equipment.
One of the more common methods used to characterize the compositions of hydrocarbon fluids involves the separation of such fluids into four fractions, i.e., saturates, aromatics, resins, and asphaltenes, then weighing each fraction to determine the composition of the hydrocarbon fluid. Such weight-based measurements are cumbersome and costly, as substantial quantities of solvents, adsorbent, and oil are required for testing accuracy.
There are methods for characterizing the compositions of hydrocarbon fluids that are well known in the art, however, considerable shortcomings remain.
In one aspect, the present invention provides a method for measuring saturate, aromatic, and resin fractions of a hydrocarbon fluid. The method comprises separating maltenes from the hydrocarbon fluid and separating saturate, aromatic, and resin fractions from the maltenes. The method further includes determining an optical density of each of the saturate, aromatic, and resin fractions and correlating the optical density of each of the saturate, aromatic, and resin fractions to predetermined data to determine each of the saturate, aromatic, and resin fractions.
The present invention provides significant advantages, including, but not limited to, providing a way to determine the saturate, aromatic, and resin fractions of a hydrocarbon fluid by using much smaller portions of the fractions than those required in conventional methods.
Additional objectives, features and advantages will be apparent in the written description which follows.
The features of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numbers denote(s) the first figure in which the respective reference numbers appear, wherein:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present invention provides a new method for measuring saturate, aromatic, and resin fractions of hydrocarbon fluids using optical spectroscopy. Asphaltenes are removed from the hydrocarbon fluid, leaving the remaining maltenes. Each of the saturate, aromatic, and resin constituents are separated from the maltenes. The optical density of each constituent is measured using optical spectroscopy. The optical density is then compared to predetermined data to determine the fraction of the constituent in the hydrocarbon fluid.
Toluene is then flushed through packed bed 105, causing the aromatics to be released from the activated alumina. The aromatics are then collected and introduced into spectrometer 110, which may have a path length of about 10 mm, wherein the optical density of the aromatics is measured at a predetermined wavelength. Although not essential for proper functioning of the invention, the optical density of the aromatics may be measured at both a shorter wavelength and a longer wavelength. As described herein concerning the saturates, the optical density of the aromatics at the longer wavelength may be subtracted from the optical density of the aromatics at the shorter wavelength to compensate or correct for errors due to the baseline shift of spectrometer 110. In one embodiment, the optical density of the aromatics is measured at about 470 nanometers and at about 800 nanometers, wherein the optical density of the aromatics at about 800 nanometers is subtracted from the optical density of the aromatics at about 470 nanometers. The measured optical density, or the resulting differential optical density normalized based on the injected mass of maltenes, is then compared to correlation data 117 to determine the fraction of aromatics in the hydrocarbon fluid. In one embodiment, correlation data 117 is resident in the memory of computer 113, which is operated to perform the correlation. Finally, the aromatics may be introduced into evaporator 115, such as a rotary evaporator, to remove the toluene from the toluene-aromatic mixture.
Still referring to
It should be noted that, while the evaporators depicted in
To assess the accuracy of the method described herein concerning
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. The particular embodiments disclosed above may be altered or modified within the scope of the invention. Accordingly, the protection sought herein is as set forth in the claims below. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications and may be used to evaluate a variety of hydrocarbon fluids.
This application claims priority from U.S. Provisional Application 61/377,354, filed on Aug. 26, 2010, which is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB2011/053288 | 7/22/2011 | WO | 00 | 6/5/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/025845 | 3/1/2012 | WO | A |
Number | Name | Date | Kind |
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4843247 | Yamazoe et al. | Jun 1989 | A |
20070120051 | DiFoggio et al. | May 2007 | A1 |
Number | Date | Country |
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0551145 | Jul 1993 | EP |
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Number | Date | Country | |
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20130242288 A1 | Sep 2013 | US |
Number | Date | Country | |
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61377354 | Aug 2010 | US |