Chemistry of hydrocarbon compounds – Miscellaneous considerations – Prevention or removal of corrosion or solid deposits
Reexamination Certificate
2000-01-25
2001-11-06
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Miscellaneous considerations
Prevention or removal of corrosion or solid deposits
C208S022000, C208S309000
Reexamination Certificate
active
06313367
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for inhibiting asphaltene deposition in hydrocarbon fluids, and more particularly relates, in one embodiment, to methods and compositions for inhibiting asphaltene deposition in crude oil using ester and ether compounds.
BACKGROUND OF THE INVENTION
Asphaltenes are most commonly defined as that portion of crude oil which is insoluble in heptane. Asphaltenes exist in the form of colloidal dispersions stabilized by other components in the crude oil. They are the most polar fraction of crude oil, and often will precipitate upon pressure, temperature, and compositional changes in the oil resulting from blending or other mechanical or physicochemical processing. Asphaltene precipitation occurs in pipelines, separators, and other equipment. Once deposited, asphaltenes present numerous problems for crude oil producers. For example, asphaltene deposits can plug downhole tubulars, well-bores, choke off pipes and interfere with the functioning of separator equipment.
It would thus be desirable to develop a composition and method employing it which would inhibit or prevent asphaltene deposition.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide ester and ether reaction products which can inhibit or prevent asphaltene deposition and methods for using them.
It is another object of the present invention to provide a family of ester and ether compounds useful in inhibiting asphaltene deposition in crude oil.
In carrying out these and other objects of the invention, there is provided, in one form, a method of inhibiting asphaltene deposition in crude oil comprising adding to the crude oil an effective asphaltene inhibiting amount of an asphaltene inhibiting compound. The asphaltene inhibiting compounds may be (1) esters formed from the reaction of polyhydric alcohols with carboxylic acids; (2) ethers formed from the reaction of fatty glycidyl ethers or fatty epoxides with polyhydric alcohols; and (3) esters formed from the reaction of fatty glycidyl ethers or fatty epoxides with carboxylic acids.
DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that various ester and ether reaction products are excellent asphaltene deposition inhibitors or dispersants for use in crude oils.
The invention specifically relates, in one embodiment, to the use of esters of polyhydric alcohols with fatty long-chain acids and linear or branched alkane and alkene acids. The polyhydric alcohols may have from about 2 to hundreds of carbon atoms, more preferably from about 2 to about 100 carbon atoms, and most preferably have from about 6 to about 50 carbon atoms. More specifically, suitable polyhydric alcohols include, but are not necessarily limited to, glycerol, sorbitol, and polyglycerols.
The carboxylic acids suitable for reacting in this invention may have from about 10 to about 30 or more carbon atoms, more preferably from about 12 to about 28 carbon atoms, and most preferably have from about 16 to about 22 carbon atoms. The suitable fatty long-chain acids include, but are not necessarily limited to, oleic acid, but also include tall-oil fatty acid, vegetable fatty acids (e.g. soya fatty acid, canola fatty acid, etc.), animal fatty acid (e.g. tallow fatty acid, etc.) and the like. Oleic acid is a particularly preferred carboxylic acid herein. In one embodiment of the invention, C
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linear or branched (e.g. isostearic acid) alkane and alkene (conjugated or non-conjugated acids) may be employed.
More specifically, in the case of glycerol and a mono-carboxylic acid, the mono-, di- or tri-esters can be formed. That is, if a mono-ester is formed, then two hydroxyl groups of glycerol will remain unreacted. Mono-esters of glycerol and other alcohols are considered to be within the scope of this invention. Thus, monoesters and polyesters (reaction products having only one ester group or having more than one ester group, respectively) and monoethers and polyethers (reaction products having only one ether group or having more than one ether group, respectively) are within the scope of this invention.
In another non-limiting aspect of this invention, polyhydric alcohols are reacted with fatty glycidyl ethers or fatty epoxides, instead of carboxylic acids. Consequently, the polyhydric alcohols react with the epoxy group to form a new ether linkage with a pendant alcohol group on the beta carbon. The mole ratio of the total alcohols to total epoxide groups can be varied such that partial or total etherification of the hydroxyl groups will occur. Suitable polyhydric alcohols are as discussed above. The glycidyl ethers or epoxides suitable for reacting in this invention may have from about 10 to about 30 or more carbon atoms, more preferably from about 12 to about 28 carbon atoms, and most preferably have from about 16 to about 22 carbon atoms. Within the scope of this invention, glycidyl ethers are understood to encompass polyglycidyl ethers, and epoxides encompasses polyepoxides.
Alternatively, in another non-limiting aspect of this invention, the carboxylic acids may be reacted with glycidyl ethers or epoxides instead of the polyhydric alcohols. In this embodiment, the carboxylic acids will react with the glycidyl ether (e.g. glycerol triglycidyl ether) or epoxide to form an ester linkage and a pendant alcohol group on the beta carbon. Again, one can vary the mole ratio of total epoxide groups to the total carboxylic groups such that partial or total esterification will occur. Suitable glycidyl ethers or epoxides for use in this embodiment are the same as those discussed above for the previous embodiment.
In another non-limiting embodiment of the invention, the asphaltene inhibiting compound averages from 4 to 6 ester groups or 4 to 6 ether groups. Further, the asphaltene inhibiting compound is selected from the group consisting of decaglycerol tetraoleate and sorbitan mono-oleate.
In one embodiment of the invention, the asphaltene inhibitor is employed in the absence of an added amine base. Further, the inventive asphaltene inhibitor is used in the absence of added free carboxylic acids and/or an added fluorochemical compound, in other embodiments. In additional embodiments of the invention, the asphaltene inhibitor of the invention is used in the absence of an added liquid paraffinic solvent or other added hydrocarbon solvent.
The effective ester and ether compounds useful as asphaltene deposition inhibitors will typically be diluted in a hydrocarbon solvent. Examples of suitable solvents include, but are not necessarily limited to, toluene, xylene, aromatic naphtha and the like.
The best asphaltene deposition inhibitor is research product RP-A, which is a dilution in a solvent of decaglycerol tetraoleate, which is obtained by reacting decaglycerol with four equivalents of oleic acid. RP-A was developed from the initial discovery that sorbitan mono-oleate was a good asphaltene inhibitor. This component was the active component of RP-B. Other oleates and esters have been investigated and are listed below with their respective performance results.
Application of the asphaltene inhibitor according to the method herein may be by continuous or batch injection into the oil pipeline, well or header system, or other equipment. It will be appreciated that there are a number of complex and interrelated factors which would determine the range of dosage of asphaltene inhibitor in a particular hydrocarbon stream, including, but not necessarily limited to, the chemical composition of the hydrocarbon or crude oil, the temperature and pressure of the stream and the nature of any mechanical or physicochemical process the stream will be subjected to. The latter includes, but is not limited to, depressurization, cooling or heating, mixing with other produced fluids, shearing, the use of other additives such as acid, and the like. While it is impossible to generalize about dosage levels because of these complex factors, it will be appreciated that in one non-limiting example, the proportion of asphaltene dep
Baker Hughes Incorporated
Griffin Walter D.
Madan Mossman & Sriram P.C.
Nguyen Tam M.
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