MXPA99007712A - Process for removing solid asphalt residues produced in the petroleum industry - Google Patents

Abstract

Fatty acid esters of general formula (I) R1-COO-(CnH2nO)x-R2 are used to remove solid asphalt residues from the surface of petroleum industry installations or petroliferous formations around petroleum bore holes. In formula (I) R1-COO-(CnH2nO)x-R2, R1 stands for an alkyl radical with 6 to 22 C atoms or for a (CH2)m-COOR4 radical, R2 and R4 independently representing an alkyl radical with 1 to 8 C atoms, n equals 2 or 3, m equals 1 to 6 and x equals 0 or a number from 1 to 12.

Description

PROCESS TO SEPARATE SOLID ASPHALTIC WASTE PRODUCED IN THE PETROLEUM INDUSTRY This invention relates to a process and compositions for separating solid asphaltene residues from the surface of production equipment or the shape surrounding the well in the production and processing of petroleum, and to the use of certain fatty acid esters for this purpose .

Crude oil is a complex mixture of different paraffinic and aromatic hydrocarbons, where the individual constituents have very different chemical and physical properties. Accordingly, both relatively low-viscosity, relatively volatile constituents and high-viscosity fractions similar to waxes are obtained in the distillation of crude oil. Wax-like fractions include petroleum resins and, for the most part, asphaltenes that are dispersed in colloidal form in the oil phase. Asphaltenes consist of a mixture of different saturated, unsaturated and aromatic hydrocarbons, more specifically naphthalene derivatives. These also contain heterocyclic hydrocarbons which in turn partially contain complexed metal ions. Asphaltenes are also compounds rich in sulfur, nitrogen and oxygen. In view of its complex composition, asphaltenes are generally characterized by their solubility. In this way, the fraction of oil insoluble in heptane or pentane, but soluble in toluene, is known by the name of asphaltenes, the "dissolution" of which represents a complex process that until now does not have a complete theoretical description (see EY Sheu, 0. C. Mullins, Asphaltenes - Fundamentals and Applications, Plenum Press, New York, 1995, chapter I and chapter III). Asphaltenes are present in the oil phase of crude oil as micellar colloids, whose individual micelles consist of several different molecules. The micelles differ in size according to the temperature and composition of the oil phase. For example, it is known that lighter aromatic hydrocarbons in crude oil stabilize asphaltene micelles. However, under the conditions in which oil is produced, asphaltenes are often precipitates that give rise to the formation of highly viscous residues, with the appearance of wax to solids on the surface of the production equipment and the formation contained in it. oil and that surrounds the well. The asphaltene residues block the pores of the formation which gives rise to a considerable reduction in production rates and, in the worst case, can even make production completely impossible. Asphaltene residues on the surfaces of production equipment, for example, distribution pipes or tube wells of pipes or separators can also seriously affect production. Therefore, there are some known methods for separating the asphaltene residues that occur in oil production. For example, the waste can be separated mechanically or by treatment with hot mineral oil or with aqueous surfactant solutions. However, in general, efforts are made to separate the waste with suitable organic solvents, more specifically benzene, toluene or xylene. Since some of these compounds do not have adequate solvent properties, searches are made for alternatives. According to the teachings of US 5,504,063, for example, the solvent properties of the aforementioned aromatic hydrocarbons can be improved by the addition of up to 50% by volume of certain N-substituted imidazolines or the condensation products of polyamines with fatty acids. On the contrary, US 5,382,728 proposes a special mixture of saturated, aromatic and polyaromatic hydrocarbons as suitable solvents for the asphaltene residues. However, these solvents or solvent mixtures can not be used in any case in view of their low flammability temperatures, its high volatility and its high cost. In addition, because the work materials have to meet more severe requirements regarding environmental compatibility and industrial safety in mind, efforts are made to avoid the use of carcinogenic and non-ecologically safe substances. Accordingly, the problem considered by the present invention was to find ecologically safe alternatives to solvents known from the prior art for solid asphaltene residues that occur in the production and processing of petroleum. Although it is already known that asphaltenes can be precipitated with polar liquids such as alcohols or esters (HJ Neuman, I. Rahimian, G. Zenke, Analytik der Asphaltene, Erdol und Kohle - Erdgas - Petrochemle, vol 39, No. 2, 1986 ), it has surprisingly been found that certain fatty acid esters are suitable as solvents for the asphaltene residues. In a first embodiment, therefore, the present invention relates to the use of fatty acid esters corresponding to the general formula (I): R1-COO- (CnH2nO)? - R2 (I) Wherein R1 is an alkyl group containing from 6 to 22 carbon atoms or a group (CH;) --COOR ', R "and R" independent of each other represent an alkyl group containing from 1 to 8 carbon atoms , n is the number 2 or 3 and m is a number from 1 to 6, and x is 0 or a number from 1 to 12, to separate the solid waste of asphaltene from the surfaces of the production equipment or the formation that contains oil and that It surrounds the sediment in the production and processing of oil. In the context of the present invention, it is understood that asphaltenes are those constituents of crude oil which, according to DIN 51595 (December 1983), precipitate when the oil is dissolved in 30 times the volume of heptane at 18-28 ° C. and that are soluble in benzene. The asphaltene solid waste is a waste having a solid or wax-like consistency at the specific treatment temperature at which the surface is exposed and of which more than 50% by weight consists of asphaltenes. In addition to asphaltenes, solid waste may also contain petroleum resins or other solids.

Asphaltene solid waste can form on the surface of the production equipment in the production of oil, understood by production equipment, in the context of the invention, any equipment that comes into direct contact with oil. This equipment includes, for example, production pipes, the lining of the well and the other carrier lines, pipes, separators, pumps and valves. Except for the coating, the surface of this production equipment normally consists of metal, more especially steel, the coating generally consists of concrete. However, the production equipment in the context of the invention also includes the processing steps of the crude oil that follow the actual production cycle, for example the distillation of the crude oil fractions. Asphaltene waste can also be present in the transportation of crude oil through the pipes or during the storage of the same and can thus affect production. However, asphaltene solid waste is also formed on the surface of the oil-containing formation surrounding the well, where they block the pores of the rock, which leads to a considerable reduction in the rate of production. The esters of the fatty acids which are used according to the invention to separate the asphaltene solid waste can be synthesized by any of the methods known to those skilled in the art. For this purpose, alcohol and fatty acid are reacted in the presence of acidic or basic catalysts, optionally under pressure. Another method for obtaining fatty acid esters corresponding to the general formula (I) is the transesterification of natural fats and oils with methanol in the presence of a catalyst. Suitable natural oils are, for example, rapeseed oil, sunflower oil, soybean oil, linseed oil or coconut oil. Suitable alcohols which can be used in the synthesis of the esters used according to the invention are non-branched, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, or branched as isopropanol, isobutanol, 2-methyl or 2-methyl. -ethylhexanol. Suitable saturated fatty acids are capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, aracaric acid or behenic acid. The unsaturated fatty acids are, for example, lauroléic acid, palmitoleic acid, oleic acid, ricinoleic acid, linoleic acid and linolenic acid. In addition to monocarboxylic acids, esters of dicarboxylic acids such as maleic acid, succinic acid or adipic acid, can also be used for synthesis. Also suitable are the technical mixtures of the esters corresponding to formula (I) which can be obtained, for example by esterifying the fatty acids of the higher fraction obtained in the purification of the fatty acid mixtures by distillation. Mixtures of the esters corresponding to formula (I) can also be used. It has proven to be a particular advantage and, therefore, the use of the esters of the general formula (I) in which R "is an alkyl group containing from 6 to 10 carbon atoms, R" is a methyl group and x is 0 is preferred. use of the mixtures of these esters obtained by esterifying the fatty acids of the upper fraction containing from 6 to 10 carbon atoms, with methanol. In addition to the fatty acid esters described above, the alkoxylates of the fatty acid esters corresponding to the formula (I) in which n is the number 2 or 3 and x is a number from 1 to 12, can also be used in accordance with the present invention. Compounds such as these are obtained by reacting the fatty acid derivatives with alkoxylated methanol or by the heterogeneously catalyzed direct alkoxylation of the alkyl esters of fatty acids with alkylene oxide, more specifically ethylene oxide. This synthesis process is described in detail in WO 90/13533 and WO 91/15441. The use of the alkyl esters of alkoxylated fatty acids of the general formula (I) is preferred, wherein R: is an alkyl group containing from 8 to 16 carbon atoms, R: is a short chain alkyl group containing 1 to 4 carbon atoms, preferably a methyl group, n is 2 and x is a number from 2 to 6. If asphaltene deposits are formed on the surface of the production equipment or the formation surrounding the well during oil production , which normally manifests itself in a reduction of the production rate, the affected part of the production team or the well is put in contact with the esters of the fatty acids. For this purpose, it is preferred that the esters be pumped through the production equipment or the well in liquid form at temperatures of at least 50 ° C to remove the deposits. Accordingly, the present invention also relates to a process for separating solid waste from asphaltene from the surface or production equipment or formation containing oil and surrounding the well in oil production and processing, characterized by the asphaltene residues they are contacted with an ester corresponding to formula (I) in liquid form and at a temperature of at least 50 ° C until the residues have been at least partially dissolved. In oil production, this manifests itself, for example, in the fact that the production rate rises again. The time it takes for the separation of the asphaltene deposits will depend on their quantity and also on the treatment temperature. For example, asphaltene deposits dissolve more rapidly under the prevailing conditions on the surface of the petroleum-containing formation, namely at pressure and elevated temperatures (150 to 300 ° C), as compared to for example the deposits that are found in the production pipe due to lower temperatures (<100 ° C) that prevail in this one. As already explained, the dissolution of the residues includes a complex process in which asphaltenes dissolve in colloidal form in the form of micelles. The production equipment can be flooded with the liquid ester alone, although this is by no means preferred for reasons of cost. In addition, depending on the temperature at which the ester is used and its melting point, viscosity problems may arise during storage of the pure ester. At low temperatures, for example, in winter heating tanks would have to be used for compounds with a relatively high melting temperature. Because of this, the esters are preferably used in the form of a mixture with a suitable solvent to avoid the aforementioned handling problems. It has been shown that the use of esters in a mixture with crude oil, the fraction that distills from 180 to 225 ° C in the distillation of crude oil, is a specific advantage. In principle it is possible to use mixtures with a weight ratio of crude oil or petroleum to the ester of 1:99 to 99: 1. However, for the purposes of the invention, the use of mixtures with a certain percentage of ester contents is preferred. Accordingly, the present invention also relates to a liquid composition containing crude oil or petroleum to remove asphaltene solid waste from the surface of the production equipment or the oil-containing formation that surrounds the well in the production and processing of the product. petroleum, characterized in that it contains more than 25% by weight of at least one fatty acid ester corresponding to the general formula (I). Compositions containing crude oil or petroleum in which more than 50% by weight of the esters corresponding to formula (I) are present are particularly preferred compositions. The esters dissolve or disperse in crude oil or oil and can thus be stored and used without difficulty. Besides crude or petroleum oil and corresponding to formula (I) esters, the compositions may also contain other ingredients, for example inhibitors of corrosion or other known solvents for asphaltene inhibitors and asphaltene to prevent precipitation, such as imidoamines, imidazolines or aromatic sulfonic acids as described in US 5,504,063. The present invention also relates to a process for separating solids of asphaltene residues from the surface of production equipment or the formation containing oil and surrounding the well in the production and processing of oil, characterized in that the deposits asphaltene get in contact with a liquid composition containing the crude oil or petroleum having a temperature of at least 50 ° C and containing at least 25% by weight of an ester corresponding to the formula (I) until the residues have been, when less partially, dissolved.

Examples A certain amount of an asphaltene deposit (residue from the Laque refinery in France) was stirred for 1.5 hours at 50-10 ° C in a glass vessel with a heavy amount of a fatty acid ester A-D. The liquids were then filtered and the remaining asphaltene residue was then washed with heptane. Solubility was determined by comparing the amount of heavy asphaltenes with the amount of filtered asphaltene residue. The results are set forth in Table 1. To detect the asphaltenes in the filtrate, 30 times the volume of heptane was added to the filtrate according to DIN 51595 (December 1983). The asphaltenes were precipitated as specified.

Ester: A methyl ester of fatty acids of rapeseed oil B methyl ester of the fatty acids of the upper fraction C methyl ester of fatty acids of C- ethoxylated with 6 moles of ethylene oxide per mole of ester D fatty acid of Ce- i4-2-ethylhexyl ester

Claims (6)

1. The use of fatty acids corresponding to the general formula (I): R1-COO- (CnH2nO)? - R2 (I) Wherein R1 is an alkyl group containing from 6 to 22 carbon atoms or a group (CH;) r-COOR ", R ~ and R 'independent from each other representing an alkyl group containing from 1 to 8 carbon atoms , n is the number 2 or 3 and m is a number from 1 to 6, and x is 0 or a number from 1 to 12, to separate the solid waste from asphaltene from the surfaces of the production equipment or the formation containing oil and that surrounds the well in the production and processing of oil

2. The use as mentioned in claim 1, characterized in that the esters corresponding to the general formula (I) are used, in which R ~ is an alkyl group containing from 6 to 10 carbon atoms, R2 is a methyl group and x is 0.

3. A process to separate solid waste from asphaltene from the surface of production equipment or the formation containing oil and surrounding the well in production and processing of petroleum, is characterized by the residues of asphal ltene are contacted with an ester corresponding to formula (I) of claim 1, in liquid form at temperatures of at least 50 ° C until the residues dissolve at least partially.

4. A composition that contains crude oil or oil to separate the solid waste of asphaltene from the surface of the production equipment or the formation that contains oil and that surrounds the well in the production and processing of the oil, is characterized because it contains more than 25% by weight of at least one fatty acid ester corresponding to the general formula (I) of claim 1.

5. The composition, as mentioned in claim 4, is characterized in that it contains more than 50% by weight of at least one fatty acid ester corresponding to the formula (I) •

6. A process for separating asphaltene solid waste from the surface of the production equipment or the oil-containing formation that surrounds the well in the production and processing of petroleum, is characterized by the fact that the asphaltene residues are put into contact with the composition claimed in claim 4 at temperatures of at least 50 ° C until the waste has dissolved at least partially.