MXPA99004770A - Additives for inhibiting formation of gas hydrates - Google Patents

Abstract

The instant invention relates to the use of water-soluble polymers comprising structural elements of formula (I) wherein each R is independently H or C 1-5-alkyl;X is H, an alkaline or earth alkaline metal or a quaternary ammonium group;R 1 is H or C 1-18-alkyl;and R 2 is C 1-18-alkyl;and wherein the alkyl groups represented by R 1 and R 2 may carry a hydroxy or amino substituent;and, if desired, a minor proportion of structural elements of formula (II) wherein R, R 1, R 2 and X may have the meaning as above, and Alk is a C 1-C 5-alkylene chain, as additives for inhibiting the formation of gas hydrates in connection with hydrocarbon production and transportation.

Description

ADDITIVES TO INHIBIT THE FORMATION OF GAS HYDRATES FIELD OF THE INVENTION This invention relates to the use of water soluble polymers to inhibit the formation of gas hydrates in pipes containing oil or gas. This is relevant for both drilling and oil and gas production.

BACKGROUND OF THE INVENTION Gas hydrates are clathrates (inclusion compounds) of small molecules in a network of water molecules. In the petroleum industry, natural gas and petroleum fluids contain a variety of these small molecules that can form gas hydrates. They include hydrocarbons such as methane, ethane, propane, isobutane, as well as *, also nitrogen, carbon dioxide and hydrogen sulfide. Larger hydrocarbons such as n-butane, neopentane, ethylene, cyclopentane, cyclohexane and benzene are also hydrate-forming components. When these hydrate-forming components are present with water at high pressures and reduced temperatures, the mixture tends to form gas hydrate crystals. For example, ethane at a pressure of 1 MPa forms hydrates only below 4 ° C, while at 3MPa gas hydrates can be formed only below 14 ° C. These temperatures and pressures are the typical means of operation where oil fluids are produced and transported. If gas hydrates are allowed to form within a pipe used to transport natural gas and / or other petroleum fluids, hydrates can eventually clog the pipe. Blockage by hydrates can lead to a production stoppage and significant financial loss. The oil and gas industry uses several means to prevent the formation of hydrate blockages in the pipes. These include heating the pipeline, reducing the pressure, removing the water and adding antifreezes such as methanol and ethylene glycols, which act as melting point depressants. Each of these methods is expensive to implement and maintain. The most common method used today is the addition of antifreeze. However, these antifreezes have to be added at high concentrations, typically 10 to 40% by weight of the water present, to be effective. The recovery of antifreeze is usually also required and is an expensive procedure. As a consequence, there is a need for cheap alternative methods to avoid obstructions by hydrates in the production and drilling of oil and gas. An alternative to the above methods is to control the gas hydrate formation process using nucleation and crystal growth inhibitors. These types of chemical agents are widely known and used in other industrial processes. The advantage of using these chemical agents to control the formation of gas hydrates is that they can be used at concentrations of 0.01 to 2%, which is much lower than that of antifreeze. It is an object of this invention to provide an additive and method for controlling gas hydrate formation by adding said additives at low concentrations to a stream of at least some light hydrocarbon and water.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, the use of polymers comprising structural elements of the formula is provided: (i) wherein each R is independently H or C1-C5 alkyl; X is H, an alkaline or alkaline earth metal or a quaternary ammonium group; Ri is H or C? -C? 8 alkyl; and R 2 is C 1 -C 8 alkyl; and wherein the alkyl groups represented by R-i and R2 can carry a hydroxy or amino substituent; and if desired, a smaller proportion of structural elements of the formula: (II) wherein R-i, R2 and X are as above, and Alk is a C1-C5 alkylene chain, and if desired, also other structural elements formed from ethylenically unsaturated monomers; the molecular weight of the polymer is on the scale of 500 to 2, 000,000, as an additive to inhibit the formation of gas hydrates with respect to the production and transportation of hydrocarbons. When reference is made to formula I in the following, this may also include minor amounts of II. The polymers preferably have a molecular weight in the range 1000-1,000,000. The units of formula I may be different, and there may also be other units different from formula i. These other units may be present in the polymer in amounts up to 90% of the polymer based on the total number of units in the polymer. Sometimes, it may be advantageous to have as little as 1% of these other units in the polymer. A polymer having units of formula I and said other units in a ratio of 2: 1 to 1: 2 may also be preferred. The distribution of the units in the polymer can be random or of an exact alternation (in particular when the ratio is 1: 1). The polymer may contain more monomers that produce units of formula I in a polymer formed by reaction of one or more primary or secondary amines having from 1 to 18 carbon atoms, with polymers or copolymers of maleic anhydride. Additionally, the polymer can be prepared by reacting one or more monoamines having from 1 to 18 carbon atoms and one or more hydroxyamines with polymers or copolymers of maleic anhydride. The polymer can be a homopolymer or a copolymer with other ethylenically unsaturated monomers including alkylvinyl ethers, (meth) acrylates, hydroxylalkyl (meth) acrylates, vinylcarboxylates, alkenes, vinyl lactams, vinylamides, acrylamidopropylsulfonic acid (AMPS), vinylsulfonic acid, alkyl (meth) acrylamides, styrene, allylamides, vinylphosphoric acid and styrenesulfonic acid. Instead of amidating the maleic anhydride polymer, it is also possible to assimilate the corresponding maleic anhydride to form a compound of the formula: (lll) wherein each R is independently H or C 1 -C 5 alkyl; X is H, an alkaline or alkaline earth metal or a quaternary ammonium group; R-i is H or alkyl, hydroxyalkyl or aminoalkyl of C, -C18; and R2 is alkyl, hydroxyalkyl or aminoalkyl of C? -C? 8. This monomer can then be subjected to polymerization, if necessary together with a comonomer. Examples of alkylamines that can be reacted with maleic anhydride and polymers thereof to form the desired product include methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, so-propylamine, iso-butylamine and n-butylamine. Examples of hydroxyamines that can be added to the reaction mixture of alkylamine and maleic anhydride polymers include 2-amino-2-methyl-1-propanol, 2-aminoethanol, 2- (2-aminoethylamino) ethanol, 2 (2- aminoethoxy) ethanol, dimethylethanolamine, 3- (dimethylamino) -1-propanol, 1- (dimethylamino) -2-propanol, N, N-dibutylethanolamine and 1-amino-2-propanol, as well as polyglycols of ethylene oxide, of propylene and butylene oxide having an extreme amino group. When a hydroxydialkylamine such as 3- (dimethylamino) -l-propanol is used, the reaction with the maleic anhydride groups will always result in structural elements of formula II, since a disubstituted amino group can not react with maleic anhydride.

Examples of alkyldiamines that can be added to the reaction mixture of alkylamine and maleic anhydride polymers include 3-dimethylaminopropylamine and 3-diethylaminopropylamine. At least one of the alkylamines to be reacted with polymers of maleic anhydride is preferably chosen from alkylamines of C3-C4. in particular n-propylamine, isopropylamine, n-butylamine and isobutylamine. In this manner, one of R-i or R2 is preferably n-propyl, isopropyl, n-butyl or isobutyl. Two or more amines can be reacted with the maleic anhydride polymer to increase the yield or for compatibility with the aqueous phase. Two examples to illustrate this, but which does not mean that they limit the scope of the application, include a mixture of isobutylamine and a hydroxyamine or a mixture of isobutylamine and methylamine. The amidated maleic anhydride monomers can be structurally part of the copolymers comprising other comonomers such as alkenes, alkylvinyl ethers, (meth) acrylates, hydroxyalkyl (meth) acrylates, vinylcarboxylates, vinyl lactams, vinylamides, acrylamidopropylsulfonic acid (AMPS), vinylsulfonic acid, alkyl (meth) acrylamides, styrene, allylamides, vinylphosphoric acid and styrenesulfonic acid. Examples of alkenes include 1 -alkenes having 2 to 24 carbon atoms and isobutylene.

Examples of (meth) acrylates include acrylic acid and acrylate salts, methacrylic acid and salts, C1.24 alkyl acrylates, C-α-24 alkyl methacrylates, dimethylaminoethyl (meth) acrylate and ethyl (meth) acrylatetrimethylammonium chloride. Examples of hydroxyalkyl (meth) acrylates include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and polyglycol esters of acrylic acid. Examples of alkylvinyl ethers include methylvinyl ether and isobutylvinyl ether. Examples of vinylcarboxylates include vinyl acetate. Examples of N-vinyl lactams include N-vinylcaprolactam, N-vinylpiperidone and N-vinylpyrrolidone. Examples of vinyllates include N-vinylacetamide, N-vinyl-N-methyl acetamide and N-vinylformamide. Examples of alkyl (meth) acrylamides include acrylamide, methacrylamide N-methylacrylamide. N, N-dimethylacrylamide, N-ethylacrylamide, N, N-diethylacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-isobutylacrylamide, acryloylpyrrolidine, methacryloylpyrrolidine, N-octyl-acrylamide, stearylacrylamide, N-methylol (meth) acrylamide, N- butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and trimethylammoniumpropyl (meth) acrylamide chloride. Depending on the chemical structure of the comonomers, the effect of the resulting polymer may be to inhibit one or more of the following processes during gas hydrate formation: nucleation or crystal growth. In addition, the polymers have a scab inhibiting activity.

DETAILED DESCRIPTION OF THE INVENTION The polymers of this invention are preferably prepared by reacting polymers and copolymers of maleic anhydride with one or more amines containing 1 to 18 carbon atoms, with or without added hydroxylamines, at a temperature sufficiently low to prevent the formation of cyclic imide products less soluble in water. The amine may be a monoamine or diamine. If one mole of amine is used per mole of maleic anhydride, the product has X = H. Although not necessary, these monocarboxylic products can be made more water soluble by adding a base such as NaOH. If two or more moles of alkylamine are used per mole of maleic anhydride, the product has X = RNH3. These products are more ionic and therefore more soluble in water than those formed using one mole of amine and no base. In addition, the R2NH3 ion also has some activity of its own to prevent the formation of hydrates, especially if R2 has 4 to 5 carbons. The solubility in water can be increased by using copolymers of maleic anhydride comprising comonomers having polar and / or ionic groups, using less than 1 mole equivalent of alkylamine reacted with the maleic anhydride polymer, or by reacting a mixture of hydroxyamine and an alkylamine with the maleic anhydride polymer. As mentioned above, the polymers of this invention are useful as additives to inhibit the formation of gas hydrates with respect to the production and transport of hydrocarbons. The additives of the present invention also contain a liquid or solid carrier or excipient, in addition to the polymers of the invention and other substances. The amount of the polymers of this invention to be added is generally between 0.05 and 5% by weight, preferably between 0.05 and 0.5% by weight based on the amount of water in the mixture containing the hydrocarbon. The polymers can be added to a stream of light hydrocarbons and water, either as powders or preferably in concentrated solution. The polymers of this invention can also be used together with several other substances called synergists, to improve the overall performance of the product. These synergists are: a) Polymers and copolymers of n-vinylcaprolactam, N-vinylpyrrolidone, alkylated vinylpyrrolidines, acryloylpyrrolidine, and polyamino acids such as polyaspartates. b) Butoxyethanol and 2-butoxypropanol, which can also be used as a solvent medium. c) Tetrabutylammonium salts, tetrapentylammonium salts, tributylamine oxide, tripentylamine oxide and compounds containing the di-, and tri-alkylamino group, wherein the alkyl is particularly butyl or pentyl, and zwitterionic compounds having at least one butyl or pentyl group on the quaternary ammonium nitrogen atom such as Bu3N + -CH2-COO. "These synergists of classes a), b), and c) are preferably added in an amount between 0.01 and 2.0% by weight based on to water content An example of a synergist-containing product is formed by the addition of a part of Gaffix VC713 (a terpolymer of N- • vinylcaprolactam, N-vinylpyrrolidone and dimethylaminoethyl acrylate) to 4 parts of the reaction product of " Gantrez AN-1 19-BF "(a copolymer of vinylethyl ether and maleic anhydride) and isobutylamine The polymers of this invention can be formulated with a solvent such as water, a glycol or lower alcohol or a mixture of these solvents. Other chemical production agents such as corrosion inhibitors, scab inhibitors and antifoams can be formulated with the polymers of this invention. It is also suspected that the polymers of this invention have anti-corrosion and anti-scab properties on their own. Particular preference is given to products that are formed by reacting a polymer that is constructed from maleic anhydride and one or more substituted or unsubstituted olefins R3R4C = CH2, with one or more acyclic diamines of C2-C-18 and, if desired, with one or more primary or secondary monoamines of C1-C12, wherein R3 and R4 are independently of each other, hydrogen or an alkyl radical of C1 -C12, C2-C12 alkenyl or C6-C2 aryl which may be interrupted with oxygen or -CO-O- or -O-CO-, and R3 may also be -COOH. The incorporation of the diamine makes it possible to prepare polymers that are soluble in a wide pH range, since the simple reaction products of the polymers based on maleic anhydride with aliphatic monoamines are polymers having carboxylate functions that become insoluble in water. in an acid medium as a result of the protonation of the carboxylate groups and therefore precipitate from the aqueous solution. When suitable diamines are incorporated, the polymer takes a cationic charge on the acid scale and thus remains soluble in water. These polymers can be alternating polymers of maleic anhydride and the corresponding olefin, as formed, in particular, in processes under low pressure, or even random polymers having molar ratios of olefin to maleic anhydride of >; 1 or < 1, which are formed predominantly in high pressure processes. Preference is given to a molar ratio of olefin to maleic anhydride of 1: 1 or 10: 1. Many of these polymers are commercially available or can be synthesized by a simple route. In this way, the polymers of maleic anhydride and vinyl ethers are obtained under the name © Gantrez AN (ISP), © Gantrez ES (GAF), © Viscofras (ICI) or © Sokalan (BASF).

The maleic anhydride polymers and the corresponding olefins can be obtained by methods known from the literature.

A summary of these syntheses is given in Methoden der Organischen Chemie, Volume E 20 (Makromolekulare Stoffe), p. 1234-1250, Georg Thiem Verlag, Stuffgart, 1987. The synthesis of alternating polymers of ethylene and maleic anhydride and random polymers of maleic anhydride and ethylene is described in the reference above and also in Polymer Science U.S.S.R. Vol. 25, No. 9, p. 2151-2160, 1983. The molecular weight of these polymers may vary within the range of 1000 - > 106 g / mol, but preference is given to molecular weights of 1000-40000 g / mol. The diamine components that can be used are dialkyl substituted diamines having from 2 to 18 carbon atoms in the molecule, preferably having a primary and a tertiary amino group, for example N, N-diethylaminopropylamine, N, N-dimethylaminopropylamine, N, N-dipropylaminopropylamine and N, N-dibutylaminopropylamine. Preference is given to dialkyl substituted diamines having from 4 to 12 carbon atoms in the molecule; 3-dimethylaminopropylamine is particularly well suited. Suitable monoamine components are monoamines having a primary or secondary amino group and 1 to 12 carbon atoms in the molecule. Preference is given to amines of the formula R5NH2, wherein R5 is an unsubstituted, branched or unbranched alkyl radical having 1 to 12, preferably 1 to 5, carbon atoms. Examples are methylamine, ethylamine, propylamine, isopropylamine, N-butylamine, isobutylamine, the pentylamines and isomeric hexylamines, as well as octylamine and dodecylamine. The polymers to be used according to the invention are prepared for example by reacting the polymer that is constructed of maleic anhydride and one or more olefins, with the monoamines and diamines mentioned above in an aqueous or aqueous-alcoholic medium, the polymer being slowly introduced in the solution of the amines. Suitable alcoholic solvents are water-soluble monoalcohols, for example methanol, ethanol, propanols, butanols and oxyethylated monoalcohols such as butylene glycol and butylene glycol. The sum of the molar amounts of the diamines and monoamines is 80-200% based on the anhydride content of the polymer. However, the diamines and monoamines are preferably added in amounts such that the sum of the amounts of diamines and monoamines corresponds to the anhydride content of the polymer. The molar ratio of diamine to monoamine is 100: 0 at 10:90. The selected reaction temperature may be from 0 ° C to the boiling point of the solvent, but is preferably selected to be below 50 ° C to enable the formation of monoamide structures and suppress ring-closing reactions that form the Measure cyclical. Transparent solutions of the modified polymers are formed.

The synergists mentioned above include blends of polyamides with one or more different polymers having a carbon skeleton and amide bonds in the side chains. These include in particular polymers such as polyvinylpyrrolidone, polyvinylcaprolactam, polymers of vinylpyrrolidone and vinylcaprolactam, and also terpolymers of vinylpyrrolidone, vinylcaprolactam and additional anionic, cationic and non-charged comonomers having a vinyl double bond, for example 1-olefins, N-alkyl acrylamides, N-vinylacetamine, acrylamide, sodium 2-acrylamido-2-methyl-1 -propanesulfonate (AMPS) or acrylic acid. Also suitable are mixtures comprising homopolymers and copolymers of N, N-dialkylacrylamides such as N-acryloylpyrrolidine, N-acrylmorpholine and N-acryloylpiperidine. Also suitable are mixtures comprising alkyl polyglycosides, hydroxyethyl cellulose, carboxymethyl cellulose and other ionic or nonionic surfactant molecules. Particularly suitable mixtures are those comprising quaternary ammonium salts, specifically tetrabutylammonium bromide and amine oxides such as tributylamine oxide.

SYNTHESIS OF POLYMERS EXAMPLE 1 9.15 g (89.5 mmol) of 3-dimethylamino-propylamine and 6.55 g (89.5 mmol) of isobutylamine are initially charged to 50.7 g of butyl glycol and 101.4 g of water at 25 ° C, and added over a period of 2 minutes, 35.0 g (179 mmol) of an ethylene-maleic anhydride polymer in pulverized form, having a maleic anhydride content of 50% by mass (molecular weight according to gel permeation chromatography about 10000). The reaction mixture is heated to 50 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a fluid yellow solution that has a content of 25% and a pH (1% in deionized water) of 8.0. The product has a solubility of 1% in deionized water at pH 1, pH3 and pH1.

EXAMPLE 2 18.3 g (179 mmol) of 3-dimethylaminopropylamine are initially charged to 53.3 g of butyl glycol and 106.6 g of water at 25 ° C, and 35.0 g (179 mmol) of an ethylene polymer are added over a period of 2 minutes. maleic anhydride in powdered form, having a 50% by mass maieic anhydride content (molecular weight according to GPC about 10000). The reaction mixture is heated to 50 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a fluid yellow solution having a content of 25% and a pH (1% in deionized water) of 9.4. The product has a solubility of 1% in deionized water at pH 1, pH3 and pH1.

EXAMPLE 3 7.15 g (70.0 mmoles) of 3-dimethylaminopropylamine and 5.12 g (70.0 mmoles) of isobutylamine are initially charged to 47.3 g of butyl glycol and 94.5 g of water at 25 ° C, and added over a period of 2 minutes, 35.0 g (140 mmoles) of an ethylene-maleic anhydride polymer in pulverized form having a maleic anhydride content of 40% by mass (molecular weight according to GPC about 10000). The reaction mixture is heated to 50 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a slightly cloudy, fluid, yellow solution, having a content of 25% and a pH (1% in deionized water) of 8.9. The product has a solubility, to give a clear solution, of 1% in deionized water at pH 1, pH 3 and pH-1 1.

EXAMPLE 4 8.33 g (81.5 mmol) of 3-dimethylamino-propylamine and 5.96 g (81.5 mmol) of butylamine in 44.3 g of butyl glycol and 88.6 g of water at 25 ° C are initially charged and added over a period of 2 minutes. , 30.0 g (140 mmol) of a polymer of vinyl acetate-maleic anhydride in pulverized form (molecular weight according to GPC about 15,000). The reaction mixture is heated to 45 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a slightly cloudy, fluid, yellow solution, having a content of 25% and a pH (1% in deionized water) of 5.8. The product has a solubility, to give a clear solution, of 1% in deionized water at pH 1, pH3 and pH11.

EXAMPLE 5 7.76 g (76.0 mmoles) of 3-dimethylamino-propylamine and 5.56 g (76.0 mmoles) of isobutylamine are initially charged in 43.3 g of butyl glycol and 86: 6 g of water at 25 ° C, and are added over a period of 3 hours. minutes, 30.0 g (152 mmol) of an alternating polymer of vinyl isobutyl ether-maleic anhydride in pulverized form (molecular weight according to GPC about 18000). The reaction mixture is heated to 48 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a fluid, transparent, orange solution, having a content of 25% and a pH (1% in deionized water) of 6.2. The product has a solubility, to give a clear solution, of 1% in deionized water at pH 1, pH3 and pH11.

EXAMPLE 6 .5 g (152 mmol) of 3-dimethylaminopropylamine are initially charged in 45.5 g of butyl glycol and 91.1 g of water at 25 ° C., and 30.0 g (152 mmoles) of an alternating polymer of vinyl-n-butyl ether-maleic anhydride in pulverized form, (molecular weight according to GPC about 16,000) are added over a period of 3 minutes. The reaction mixture is heated to 42 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a cloudy yellowish solution having a content of 25% and a pH (1% in deionized water) of 7.0. The product has a solubility, to give a clear solution, of 1% in deionized water at pH 1, pH3 and pH11.

EXAMPLE 7 7.76 g (76.0 mmoies) of 3-dimethylamino-propylamine and 5.56 g (76.0 mmoles) of isobutylamine are initially charged in 43.3 g of butyl glycol and 86.6 g of water at 25 ° C, and added over a period of 3 minutes, 30.0 g (152 mmol) of an alternating polymer of vinyl-n-butyl ether-maleic anhydride in pulverized form (molecular weight according to GPC about 16000). The reaction mixture is heated to 48 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a clear orange solution, which has a content of 25% and a pH (1% in deionized water) of 5.9. The product has a solubility, to give a clear solution, of 1% in deionized water at pH 1, pH3 and pH11.

EXAMPLE 8 7.76 g (76.0 mmoles) of 3-dimethylamino-propylamine and 4.50 g (76.0 mmoles) of isopropylamine are initially charged in 42.3 g of butyl glycol and 84.5 g of water at 25 ° C, and are added over a period of 3 minutes, 30.0 g (152 mmol) of an alternating polymer of vinyl isobutyl ether maleic anhydride in pulverized form (molecular weight according to GPC about 18000). The reaction mixture is heated to 48 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a clear, light yellow fluid solution, which has a 25% content and a pH (1% in deionized water) of 6.2. The product has a solubility, to give a clear solution, of 1% in deionized water at pH3 and pH11.

EXAMPLE 9 7.76 g (76.0 mmoles) of 3-dimethylaminopropylamine and 5.40 g (76.0 mmoles) of an aqueous solution of ethylamine at a concentration of 63.5%, in 43.2 g of butyl glycol and 86.4 g of water at 25 ° C were initially charged, and 30.0 g (152 mmol) of an alternating polymer of vinyl-n-butyl ether-maleic anhydride in pulverized form are added over a period of 3 minutes (molecular weight according to GPC about 16,000). The reaction mixture is heated to 45 ° C and after completion of the exothermic reaction, it is stirred for a further 2 hours at 50 ° C. This produces a clear, light yellow solution, which has a content of 25% and a pH (1% in deionized water) of 6.0. The product has a solubility, to give a clear solution, of 1% in deionized water at pH1 and pH11.

Effectiveness of polymers The effectiveness of polyamides was studied by means of a THF hydrate test. Since natural gas hydrates exist only at high pressures, which are obtained only with difficulty under laboratory conditions, the formation of THF (tetrahydrofuran) clathrates and water was used as a model. These hydrates are formed at atmospheric pressure and 4 ° C in a molar ratio of water: THF of 17: 1. If an additive kinetically inhibits the formation of THF hydrates or keeps the formed THF hydrates agitable, then this additive should have a similar effect on naturally occurring gas hydrates. As can be shown in the following experimental examples, in the absence of an inhibitor, the formation of THF hydrate begins rapidly under the experimental conditions and leads to the formation of THF hydrates in acicular or platelet form, which very quickly results in the solidification of all the test solution. The addition of the polymer significantly delays the formation of THF hydrate and / or alters the crystal form of the hydrates formed. All the polyamides used significantly delayed the formation of THF hydrate. The THF test was carried out as follows: Experiments without inhibitor A short Pasteur pipette (I = 140 mm) is fixed in a perforated cork stopper in such a way that the tip of the pipette projects 120 mm from the cork stopper. A drop of a THF / water mixture (1: 17) is then taken in this pipette by means of capillary action, the pipette is weighed (with the cork stopper) and cooled for at least 2 hours at -20 ° C. . A solution of sodium chloride of 3.5% concentration is mixed with THF in a ratio of 4: 1. 30 ml of this solution is placed in a test tube (150 x 30 mm) and cooled for 25 minutes at 0 ° C in a cooling bath (the test tube is immersed in a cooling bath at a depth of approximately 60 mm). The frozen pipette is then taken from the refrigerator, rinses quickly (to remove glass nuclei from the outside of the pipette and obtain uniform initial conditions) and immersed immediately to a depth of approximately 15 mm in the previous mixture of THF / water / sodium chloride, forming hydrates of THF after a short time (a few minutes). After 60 minutes, the pipette is taken very carefully from the test tube and the pipette together with the cork stopper and the adhered hydrates are weighed immediately. The rate of formation of THF hydrate (in g / h) of the difference between the initial and final weights and the elapsed time is calculated.

EXAMPLES 1-9 The blank determination procedure is repeated, but 5,000 ppm of the appropriate inhibitor is added to the test solution (based on the water content of the mixture). The evaluation is carried out as before. The results are summarized in table 1 and show the effectiveness of the compounds used: TABLE 1 THF test, hydrate formation rates VF = formation speed (g / h) In addition, the effectiveness of the polymers of the invention was studied by means of autoclave experiments under isochoric conditions (at constant volume) using mixtures of water and gas. For this purpose, in the reference experiment deionized water was treated in an autoclave with approximately 50 bars of a natural gas that forms hydrates of structure II (predominantly methane, content of n-propane> 1%) and cooled by stirring (speed of agitation 250 rpm) according to a temperature program (see below). The pressure changes indicate the nucleation and crystal growth of the gas hydrates and the produced torque, which represents a measurement of the agglomeration of hydrates, is measured by means of a torque detector. As can be shown in the following experimental examples, the formation of gas hydrate begins rapidly without inhibitor under the experimental conditions, and leads to a large increase in torque, so that the formation of large agglomerates of hydrate can be concluded. On the contrary, the addition of small amounts (in all examples 500 ppm = 0.05%) of the polymers of the invention, leads either to a considerable delay in the formation of hydrate (example 1) or to the complete inhibition of the formation of gas hydrates during the whole experiment (example 4/5). The apparatus for measuring the inhibition of gas hydrates is described in D. Lippmann, Thesis, Techn. Universitát Clausthal, 1995. The test products were dissolved in 88 ml of deionized water in a steel autoclave with stirring provided with temperature control and a torque detector (agitation speed: 250 rpm) at a volume ratio of gas to aqueous phase of 8: 2, and the autoclave was pressurized with gas at 49-53 bar. From an initial temperature of 17.5 ° C, the contents of the autoclave were cooled to 2 ° C over a period of 2 hours, then stirred for 20 hours at 2 ° C and again warmed to 17.5 ° C over a period of time. of 2 hours. During cooling, a small decrease in pressure was observed first, corresponding to the thermal contraction of the gas. When the formation of gas hydrate nuclei occurs, the measured pressure is reduced and an increase in the measured torque is observed; in the absence of the inhibitor, the additional crystal growth and the increasing agglomeration of these hydrate cores rapidly lead to an additional increase in the measured torque. The time to reach the minimum temperature of 2 ° C at the first decrease in gas pressure is referred to as the induction time. When heating the reaction mixture, the gas hydrates finally decompose again, so that at the end of the experiment the initial state is restored.

The concordance of the results of the THF test with the experimental examples under high pressure conditions, show that the behavior of an inhibitor in the THF test is a valid measure of effectiveness under high pressure conditions. To demonstrate the increased compatibility of the modified maleic anhydride copolymers of the invention in salt water, in comparison with the conventional products based on polyvinylpyrrolidone / polyvinylcaprolactam, the turbidity points of solutions with a concentration of 1% of the corresponding polymers were measured. in a sodium chloride solution with a concentration of 3.6% (% =% by weight) ADDITIONAL EXAMPLES Test equipment and procedure To evaluate the performance of the hydrate inhibiting polymers of this invention, the examples given herein use high-pressure sapphire cells and the methods using them are described in M.A. Kelland, T.M.

Svartaas and L.A. Dybvik, Proc. SPE Annual Technical Conference / Production Operations and Engineering, 1994, p. 431-438. The illustrated equipment is illustrated in Figure 1. The sapphire cell was mounted in a cooling bath. The sapphire cell consists of a sapphire tube 1 encased in a fastener between two stainless steel end pieces. The cell has an internal diameter of 20 mm, height of 100 mm and a wall thickness of 20 mm. 15 mm from the top piece and 13 mm from the bottom piece, protrude towards the cell, and the total volume between the top and bottom piece is 22.6 ml. The sapphire cell is equipped with an agitator mechanism. A stirring blade 2 is connected to a magnetic housing in the lower end piece by means of an axis. An external rotation magnetic field 3 created by a laboratory stir bar pulse is used to regulate the speed of the agitator. The agitator motor can be adjusted to maintain a constant speed (independent of the motor load) on the scale from 0 to 1700 rpm. The regulator / amplifier unit has output connections for readings of both torque and rotation speed. The agitator speed readings are calibrated using a strobe. The sapphire cell is placed inside transparent plastic double-wall carbonate cylinders with four separate windows at 0, 90, 180, 270 ° for visual observations. Temperature control of the cell is obtained by circulating water in the plastic cylinders and through a chiller / heater unit 8 connected to a temperature control unit 9. The cell system is equipped with two temperature sensors for the measurement of the temperature inside cell 5 (in the gaseous phase) and in the water bath 6. The pressure is measured with a pressure transducer through the inlet pipe connection in the upper end part of the cell. The temperature was measured to an accuracy of ± 0. 1 ° C, and the pressure was measured to an accuracy of ± 0.2 bar. Video recordings of the experiments were also made. All the data was collected in a data indicator 10. The data can be sent to a printer / plotter 1 1.

The same procedure was followed for the preparation of the experiment and filling of the cell in all the experiments. All tests were performed in recent synthetic seawater (SSW = 3.6%) and synthetic natural gas (SNG). Condensate was added in experiments 23-25. A description of the general test procedure is given here: 1) The polymer to be tested was dissolved or dispersed in synthetic seawater (SSW) to the desired concentration. 2) The magnetic housing of the cells was filled with the aqueous solution containing the inhibitor to be tested. The magnetic housing was then mounted on the lower end piece of the cell, which was then attached to the sapphire tube and the cell holder. 3) The desired amount of the aqueous solution containing the dissolved inhibitor was placed in the cell (above the bottom of the cell) using a pipette, the upper end piece was fitted and the cell was placed in the cooling bath (cylinder of plastic). 4) The temperature of the cooling bath was adjusted to 2-3 ° C outside the hydrate region under the pressure conditions to be used in the experiment. 5) Before loading the cell with hydrocarbon or condensate gas, it was purged twice with the SNG used in the experimental hydrocarbon fluid. 6) Data recording and video recording was started, and the cell was charged with the hydrocarbon fluid to the desired pressure while stirring at 700 rpm. Normally, the hydrocarbon fluid was SNG.

The experiment was started after stabilizing the temperature and pressure in the cell. All crystal nucleation / growth experiments, so-called "kinetic inhibition" experiments, were performed at constant temperature. Once the temperature and pressure stabilized after loading the cell, stirring was stopped. The closed cell was then cooled to the experimental temperature, resulting in a reduction in pressure. When the temperature and pressure stabilized again, agitation was started at 700 rpm. The induction time, ti, for the hydrate formation, was measured from the start time of the stirring at the experimental temperature. The time of onset of hydrate formation at the time of rapid hydrate growth is called the crystal growth delay time, St-1. The procedures given here for the synthesis of polymers by reacting amines with maleic anhydride copolymers are only examples of the possible synthetic techniques that can be used for the methods according to the invention.

KINETIC INHIBITION EXPERIMENTS Examples 10-19 are carried out using SNG and brine at 90 bar and 7.5 ° C (? T = 13.8 ° C).

EXAMPLE 10 Several kinetic inhibition experiments without additives were carried out. The total delay time before rapid gas uptake occurred (ie, the induction time t, plus the St-1 crystal growth delay time) was less than 3 minutes in all experiments.

EXAMPLE 11 Ethylene-maleic anhydride copolymer was added as a fine powder to a solution of n-PrNH2 in diethyl ether at room temperature, and stirred for 1 hour. One mole of n-PrNH2 was used per mole of maleic anhydride in the copolymer. The suspension was evaporated to dryness to leave a white solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave tl = 137 minutes and St-1 = 37 minutes.

EXAMPLE 12 Ethylene-maleic anhydride copolymer was added as a fine powder to a solution of i-BuNH2 in diethyl ether at room temperature, and stirred for 1 hour. 1 mole of i-BuNH2 was used per mole of maleic anhydride in the copolymer. The suspension was evaporated to dryness to leave a white solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave tl = 885 minutes and St-1 = 183 minutes.

EXAMPLE 13 Ethylene-maleic anhydride copolymer was slowly added as a fine powder to an excess of pure isopropylamine solution at room temperature, and stirred for 1 hour. The suspension was evaporated to dryness to leave a whitish solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave tl = 115 minutes and St-1 = 15 minutes.

EXAMPLE 14 Ethylene-maleic anhydride copolymer was slowly added as a fine powder to an excess of pure solution of n-butylamine at room temperature, and stirred for 1 hour. The suspension was evaporated to dryness to leave a whitish solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave t, = 1 17 5 minutes and St-1 = 55 minutes in a first experiment and t¡ = 190 minutes and St-1 = 37 minutes in a second experiment.

EXAMPLE 15 Ethylene-maleic anhydride copolymer was slowly added as a fine powder to an excess of pure isobutylamine solution at room temperature, and stirred for 1 hour. The suspension was evaporated to dryness to leave a whitish solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave tl = 103 minutes and St-1 = 171 minutes in a first experiment and t¡ = 1 18 minutes and St-1 = 153 minutes in a second experiment EXAMPLE 16 Ethylene-maleic anhydride copolymer was slowly added as a fine powder to an excess of pure solution of sopentylamine at room temperature, and stirred for 1 hour. The suspension was evaporated to dryness to leave a whitish solid. When kinetic inhibition was tested at 0.5% by weight in 3.6% SSW, the product gave tl = 21 minutes and St-1 = 27 minutes.

EXAMPLE 17 The kinetic inhibition of a product formed by reacting Gantrex AN-119-BF (methylvinyl ether copolymer and maleic anhydride) and sobutylamine was tested at 0.5% by weight in 3.6% SSW. The product gave t = 48 minutes and St-1 = 43 minutes.

EXAMPLE 18 The kinetic inhibition of a product similar to Example 8 formed by reacting Gantrex AN-1 69-BF (copolymer of methylvinyl ether and maleic anhydride) and isobutylamine, was tested at 0.5% by weight in 3.6% SSW. The product gave tl = 106 minutes and St-1 = 60 minutes in the first experiment, and t¡ = 256 minutes and St-1 = 69 minutes in a second experiment.

EXAMPLE 19 The kinetic inhibition of a product formed by reacting Gantrez AN-169-BF (methylvinyl ether copolymer and maleic anhydride) with an excess of isobutylamine and ethanolamine in a molar ratio of 4: 1, to 0.5% by weight in SSW was tested. 3.6%. The product gave t > 1212 minutes EXAMPLE 20 The kinetic inhibition of a product formed by reacting isobutyl vinyl ether-maleic anhydride copolymer with a mixture of isobutylamine and dimethylaminopropylamine was tested at 0.5% by weight in 3.6% SSW. The product gave t = 795 minutes and St-1 = 192 minutes.

EXAMPLE 21 The kinetic inhibition of the polymer product used in example 11 was tested at 0.4% by weight in 3.6% SSW, with the addition of vinylpyrrolidone-vinylcaprolactam copolymer 0.1% by weight, 1: 1. The product gave t = 1222 minutes.

EXAMPLE 22 The kinetic inhibition of the polymer product used in example 11 was tested at 0.4% by weight in 3.6% SSW, with the addition of tributylamine oxide 0.1% by weight. The product gave t = 1059 minutes and St-1 = 32 minutes.

EXPERIMENTS OF KINETIC INHIBITION USING SNG AND CONDENSATE Examples 23-25 were carried out using a North Sea condensate and the same SNG and brine as in Examples 1-13, at 90 bar but at different temperatures.

EXAMPLE 23 The kinetic inhibition of the polymer product used in Example 3 was tested at 0.5% by weight in 3.6% SSW at 8.8 ° C (SD = 9.7 ° C). The product gave t = 621 minutes and St-1 = 48 minutes. In an identical experiment at 6.8 ° C (SD = 11.7 ° C), the result was t = 28 minutes and St-1 = 10 minutes. Without an additive, this system clogs with hydrate in less than 5 minutes at either 8.8 ° C or 6.8 ° C.

EXAMPLE 24 The kinetic inhibition of the polymer product used in Example 3 was tested at 0.5% by weight in 3.6% SSW at 6.8 ° C, with the addition of 0.1% polyvinylcaprolactam. The product gave t = 480 minutes and St-1 = 300 minutes.

EXAMPLE 25 The kinetic inhibition of the polymer product used in Example 3 was tested at 0.5% by weight in 3.6% SSW at 6.8 ° C, with the addition of 0.1% tetrabutylammonium bromide. The product gave t = 145 minutes and St-1 = 25 minutes.

Claims (4)

1. NOVELTY OF THE INVENTION CLAIMS 1. - The use of a water-soluble polymer comprising structural elements of the formula: (I) wherein each R is independently H or C? -C5 alkyl; X is H, an alkaline or alkaline earth metal or a quaternary ammonium group; Ri is H or C? -C? 8 alkyl; and R2 is C-? -C- alkyl- < 8; and wherein the alkyl groups represented by R, and R 2 can carry a hydroxy or amino substituent; and if desired, a smaller proportion of structural elements of the formula: (II) wherein R, Ri, R2 and X may have the same meaning as above, and Alk is a C1-C5 alkylene chain, as an additive for inhibiting the formation of gas hydrates in the production and transportation of hydrocarbons.
2. 2. The use of a polymer according to claim 1, wherein the molecular weight is 1,000-1,000,000.
3. 3. The use of a polymer according to any of claims 1 or 2, comprising different structural elements of formula (I) and, if desired, (II).
4. 4. The use of a polymer according to any of claims 1-3, comprising units of formula (I) and, if desired, (II) wherein R is H. 5. - The use of a polymer according to any of claims 1 to 4, comprising units of formula (I) and, if desired, (II) wherein Ri is H and R2 is C3-C4 alkyl. 6. The use of a polymer according to any of claims 1 to 5, comprising units of formula (I) and, if desired, (II) wherein X is H. 7.- The use of a polymer according to any of claims 1-6, which comprises not only units of formula (I) and, if desired, (II), but also other units corresponding to ethylenically unsaturated comonomers. 8. The use of a polymer according to claim 7, comprising up to 90 mol% of said other units. 9. The use of a polymer according to claim 8, wherein the ratio of the number of units of formula (I) and, if present (II), to the number of the other units, is in the scale of 2. : 1 to 1: 2. 10. The use of a polymer according to claim 1, which is formed by reacting a starting polymer that is constructed from maleic anhydride and one or more substituted or unsubstituted olefins R3R4C = CH2, with acyclic diamines of C2-C? 8 and, if desired, primary and / or secondary C1-C12 monoamines, wherein R3 and R4 are independently from each other, hydrogen or a C1-C12 alkyl radical, C2-C12 alkenyl or aryl of C6-C? 2 which may be interrupted by oxygen or -CO-O- or -O-CO, and R1 may also be -COOH. 12. - The use of a polymer according to claim 10, wherein the polymer is constructed from maleic anhydride and ethylene and, if desired, more components. 13. The use of a polymer according to claim 10, wherein the polymer is constructed from maleic anhydride and one or more vinyl ethers and, if desired, more components. 14. The use of a polymer according to claim 10, wherein the polymer is constructed from maleic anhydride and vinyl acetate and, if desired, more components. 15. The use of a polymer in accordance with the claim 10, wherein the polymer is constructed from maleic anhydride and styrene and, if desired, more components. 16. The use of a polymer according to claim 10, wherein the diamine is acyclic, has a primary or tertiary amine group and from 4 to 12 carbon atoms in the molecule. 17. The use of a polymer according to claim 10, wherein the diamine is 3-dimethylaminopropylamine. 18. The use of a polymer according to claim 10; wherein the monoamine is a primary monoamine with 1 to 12 carbon atoms in the molecule. 19. The use of a polymer according to claim 10, wherein the monoamine is a primary monoamine with 1 to 5 carbon atoms in the molecule. 20. - The use of a polymer according to any of claims 10-17 in admixture with one or more polymers that are constructed from a carbon skeleton, obtained by polymerization, and amide bonds in the side chains, and in admixture with quaternary ammonium salts and amine oxides. 21. An additive for inhibiting the formation of gas hydrates in the production and transportation of hydrocarbons, comprising one or more polymers according to any of claims 1-20, if desired combined with a liquid or solid carrier or excipient. 22. A method of inhibiting the formation of gas hydrate in a system for drilling, producing and / or transporting oil and gas, comprising adding to the system an additive comprising a polymer according to any of claims 1 -20 in an amount of 0.01 to 2% by weight based on the water present in the system. 23. The method according to claim 22, wherein a synergist is added in combination with said polymer. 24. The method according to claim 22, wherein the synergist is selected from polymers and copolymers of N-virocaprolactam, N-vinylpyrrolidone and alkylated vinylpyrrolidones. 25.- The use of a chemical compound of the formula: (lll) wherein each R is independently H or C1-C5 alkyl; X is H, an alkaline or alkaline earth metal or a quaternary ammonium group; R, is H or alkyl, hydroxyalkyl or aminoalkyl of C-i-C-is; and R2 is alkyl, hydroxyalkyl or aminoalkyl of C -? - C-? 8, as an additive for inhibiting the formation of gas hydrates in the production and transportation of hydrocarbons. 26. The use of a chemical compound according to claim 25, wherein each R is H. 27.- The use of a chemical compound according to any of claims 25 or 26, wherein Ri is H and R2 is C3-C4 alkyl. 28. The use of a chemical compound according to any of claims 25-27, wherein X is H. SUMMARY OF THE INVENTION The present invention relates to the use of water soluble polymers comprising structural elements of the formula: (") wherein each R is independently H or C 1-5 alkyl; X is H, an alkaline or alkaline earth metal or a quaternary amino group; R-i is H or C-i-? 8 alkyl; and R2 is C? -? 8 alkyl; and wherein the alkyl groups represented by R, and R 2 can carry a hydroxy or amino substituent; and if desired, a smaller proportion of structural elements of formula: (H) wherein R, R-i, R2 and X may have the same meaning as above, and Alk is a C1-C5 alkylene chain, as additives to inhibit the formation of gas hydrates in the production and transportation of hydrocarbons. EA / ald * asg * ram * amm P99-362F