MXPA97003503A - Procedure to inhibit or delay formation the agglomeration of hydrates in a deflection effluent - Google Patents

Abstract

The present invention relates to a method for inhibiting or retarding the formation, growth and / or agglomeration of natural gas hydrates, petroleum gas or other gases, by the use of at least one additive. The gases forming the hydrates may especially comprise at least one hydrocarbon chosen from methane, ethane, ethylene, propane, propene, n-butane, and optionally H2S or CO2. These hydrates are formed when the water is in the presence of the gas, either in the free state, or in the dissolved state in a liquid phase, such as a liquid hydrocarbon, and when the temperature reached by the mixture, especially water , of the gas and possibly of liquid hydrocarbons, such as oil, has become lower than the thermodynamic temperature of hydrate formation, this temperature is set for a known gas composition and when its pressure is fi

Description

"DEVELOPMENT TO INHIBIT OR DELAY THE FORMATION OR AGGLOMERATION OF HYDRATES IN AN EFFLUENT OF PRODUCTION" FIELD DB THE INVENTION The present invention relates to a method for inhibiting or retarding the formation, growth and / or agglomeration of natural gas hydrates, petroleum gas or other gases, by the use of at least one additive. The gases forming the hydrates may especially comprise at least one hydrocarbon selected from methane, ethane, ethylene, propane, propene, n-butane and isobutane, and optionally H2S or C02. These hydrates are formed when the water is in the presence of the gas, either in the free state, or in the dissolved state in a liquid phase, such as a liquid hydrocarbon, and when the temperature reached by the mixture, especially water , of the gas and possibly of liquid hydrocarbons, such as oil, has become lower than the thermodynamic temperature of hydrate formation, this temperature is given for a known gas composition and when its pressure is fixed.

BACKGROUND DB THE INVENTION The formation of hydrates can be feared or undesirable, especially in the oil industry and Ref. 24681 gasera, for which the conditions of hydrate formation can be met. In effect, in order to reduce the production cost of crude oil and gas, both from the point of view of investments and from the point of view of exploitation, a route or route contemplated, especially in production at sea, is the one of reducing, instead of suppressing, the treatments applied to the crude oil or to the gas for the transport of the deposit to the coast and especially to leave all or a part of the water in the fluid to transport. These treatments at sea are generally carried out on a platform located on the surface in the vicinity of the deposit, so that the effluent, initially hot, can be treated before the thermodynamic conditions of hydrate formation are not reached due to the made from the cooling of the effluent with seawater. However, as it happens in a practical way, when the thermodynamic conditions required to form the hydrates are reunited, the agglomeration of the hydrates causes the blockage of the transport ducts by the creation of plugs that prevent any passage of crude oil or gas. The formation of hydrate plugs can cause a stoppage of production and thus cause significant financial losses. In addition, the new implementation Installation service, especially if it is production or transport at sea, can be prolonged, because the decomposition of the hydrates formed is very difficult to perform. In fact, when the production of a submarine deposit of natural gas or oil and gas that carries water reaches the surface of the sea floor and is then transported to the seabed, it is reached by reducing the temperature of the effluent produced , to that the thermodynamic conditions are reunited so that the hydrates are formed, agglomerate and block the transfer conduits. The temperature at the bottom of the sea can be, for example, 3 or 4 ° C. Favorable conditions for the formation of hydrates can also be gathered in the same way on land, for the passages that pass (or pass quite deeply) buried in the terrestrial soil, when for example the air temperature of the environment is cooled . To avoid these drawbacks, it has been sought, in the prior art, to use products that, added to the fluid, could act as inhibitors reducing the thermodynamic temperature of hydrate formation. These are especially alcohols, such as methanol, or glycols, such as mono-, di- or tri-ethylene glycol. This solution is very expensive because the The amount of inhibitors that will be added can reach 10 to 40% of the water content and these inhibitors are difficult to recover completely. The isolation of the transport conduits has also been postulated, so as to prevent the temperature of the transported fluid from reaching the hydrate formation temperature under the operating conditions. One such technique is, by itself, very expensive. The use of additives capable of modifying the mechanism of hydrate formation is still described, since, instead of quickly agglomerating each other and forming plugs, the hydrates formed are dispersed in the fluid without agglomerating and without obstructing the conduits. Mention may be made in this regard: patent application EP-A-323774 in the name of this same applicant, which describes the use of non-ionic amphiphilic compounds selected from the polyols and carboxylic acid esters, substituted or unsubstituted, and the compounds with imida function; patent application EP-A-323775, also in the name of this same applicant, which describes in particular the use of compounds belonging to the family of fatty acid diethanolamides or of fatty acid derivatives; US-A-4956593 which describes the use of surfactant compounds such as organic phosphonates, phosphate esters, phosphonic acids, their salts and esters, inorganic polyphosphates and their esters, as well as homopolyacrylamides and acrylamide-acrylate copolymers; and patent application EP-A-457375, which describes the use of anionic surfactant compounds, such as alkylarylsulfonic acids and their alkali metal salts. The amphiphilic compounds obtained by the reaction of at least one succinic derivative selected from the group consisting of the polyalkenylsuccinic acids and anhydrides on at least one polyethylene glycol monoether have also been proposed to reduce the agglomeration tendency of the natural gas hydrates, Petroleum gas or other gases (patent application EP-A-582507). On the other hand, the use of additives capable of inhibiting or delaying the formation and / or growth of hydrates has also been postulated. One can cite in this regard the patent application EP-A-536950, which describes the use of tyrosine derivatives, the international application OA-9325798, which describes the use of homopolymers and copolymers of N-vinyl-2- pyrrolidone and mixtures thereof, international application WO-A-9412761 and US-A-5432292 which describe the use of poly (N-vinyl) 2-pyrrolidone), of the hydroxyethyl cellulose and its mixtures or of a terpolymer based on N-vinyl-2-pyrrolidone, N-vinyl-e-caprolactam and dimethylaminoethyl methacrylate marketed under the name of GAFFIX VC-713. The international application WO-A-9519408 describes more generally the use of aliphatic polymers containing N-carbonyl heterocycles in the complex formulations. It is the same case of the international application O-A-9532356, which describes in particular the use of the terpolymer based on N-vinyl-2-pyrrolidone, of acrylamido methyl acrylamide sulfonate and of acrylamide. Finally, international applications WO-A-9517579 and WO-A-9604462 describe the use of alkylated ammonium, sulfonium and phosphonium derivatives either alone or mixed with a corrosion inhibitor. It has now been discovered that certain water-soluble polymers which can be neutral or positively charged homopolymers or copolymers, or even polyanfolites and which are derived from one or more nitrogenous monomers, allow, at reduced concentrations, inhibit or retard formation, growth and / or the agglomeration of hydrates of natural gas, petroleum gas or other gases, with an efficacy clearly superior to the compounds described above.

DETAILED DESCRIPTION DB THE INVENTION Thus, the invention proposes a method for inhibiting or retarding the formation, growth and / or agglomeration of hydrates within a fluid comprising water and a gas, under the conditions where hydrates can be formed (from of water and gas), characterized in that at least one water-soluble homopolymer or copolymer defined in a general manner as that derived from at least one nitrogenous monomer chosen from cationic (or positively charged) monomers, monomers is incorporated into said fluid. amphoterous (that is, they carry both a positive charge and a negative charge) and the neutral monomers chosen from: - the monomers [A] having at least one tertiary amine function and optionally at least one amide function on a side chain and corresponding to the general formula [1]: R CH, C R- R? [1] N wherein R 'is a hydrogen atom or a methyl group, R "is selected from the divalent groups -COO-, -CO-NH-, -CO-NH-CO-NH- or -C6H4-, R? is chosen from the following divalent groups ~ (CH2 ^ n ~ 'with ^ - n -' -C (CH3) 2-, -C (CH3) 2- (CH2) 2- or -CH2-CH (OH) CH2-, R 2 is a hydrogen atom or a methyl, ethyl or iso-propyl radical, R 3 is a hydrogen atom or a methyl or ethyl radical; -monomers [B] which have at least one amide function on a side chain and which respond to the general formula [2]: R CH, • C C = 0 NH [2] R4 wherein R 'is a hydrogen atom or a methyl group and R4 a group -C (CH3) 2 -CH2-C0-CH3 or -CH20H; - the monomers [C] have a pendant aromatic nitrogenous radical and correspond to the general formula [3]: wherein R 'is a hydrogen atom or a methyl group; the monomers [D] that have a succinimide function on a side chain and that correspond to the general formula [4]: R ' wherein R 'is a hydrogen atom or a methyl group; - and the monomers [E], which correspond to the general formula [5]: (CH2 = CH- (CH2)) 2-N-R5 [5] wherein, R5 is an alkyl chain cnH2n + l 'with ^ < n < 10, or a hydroxyl group or a group - (CH2) 2 -CO-NH2.

As examples of neutral monomers that illustrate these formulas, mention may be made of dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate. The cationic monomers considered more particularly in the definition of the polymers of the invention, are those that carry quaternary ammonium groups. These may be monomers derived from the quaternization by chlorination, sulfomethylation, sulphoxylation or chlorobenzylation of the monomers of the type [A], [C] or [E] described above. These cationic monomers [F], [G] and [H] correspond respectively to the general formulas [6], [7] and [8] below: - the monomers [F], of the general formula [6] R C wherein R 'is a hydrogen atom or a methyl group, R "is selected from the divalent groups -COO-, -CO-NH-, -CO-NH-CO-NH- or -C6H-,? is chosen among the following divalent groups - (CH) -, with 1 < n < 3, -C (CH3) 2-, -C (CH3) 2- (CH2) 2- or -CH2-CH (OH) CH2-, R2 is a hydrogen atom, or a methyl, ethyl or isopropyl radical, R3 is a hydrogen atom or a methyl or ethyl radical, Rft is selected from the methyl, ethyl or benzyl groups and X is an ionic chloride or a CH30S03 ion; the monomers [G], of the general formula [7]: wherein R 'is a hydrogen atom or a methyl group, R? a group -C (CH3) 2 -CO-CH3, -CH20H, methyl, ethyl or benzyl and X is a chloride ion or a CH30S03 ion; - and the monomers [H], of the general formula [8] ; CH2 = CH- (CH2)) 2-N + -R5R6 X- [8] wherein, 5 is an alkyl chain with cnH2 + 1 * with 1 < n < 10, a hydroxyl group or a group (CH) -C0-NH2 > R6 is selected from methyl, ethyl or benzyl groups and X is a chloride ion or a CH30S03 ~ ion. Examples of cationic monomers are methacrylate-ethyltrimethyl ammonium chloride, methacrylamido-N-propyl chloride -trimethyl ammonium and diallyl-dimethyl ammonium chloride. The amphoteric monomers [IJ, [J] and [K] (which carry both a positive charge and a negative charge) considered in the definition of the polymers of the invention, respond to the following general formulas: - the monomers [I], of the general formula [9] R 'CH, R? O wherein R ', R3 and Rg are either hydrogen atoms or methyl groups, RQ is selected from the divalent groups -COO- or -CO-NH-, R .. and R are selected from the following divalent groups - ( CH2) n ~, with 1 < n < 3, -C (CH3) 2 ~ or -C (CH3) 2 ~ (CH2) 2 ~ and G is a negatively charged group of the carboxylate or sulfonate type; - the monomers [J], of the general formula [10]: CH, -CH k14 wherein R. is a hydrogen atom or a methyl group, R-, is selected from the divalent groups - (CH2) -with 1 < n < 4, or -CH2-C6H4- and G is a negatively charged group of the carboxylate or sulfonate type; - and the monomers [K], of the general formula [11]; wherein R 'is a hydrogen atom or a methyl group, Rjr is a divalent group of the type ~ (CH2) n-, with 1 < n < 4, and G ~ is a negatively charged group of the carboxylate or sulfonate type. As an example of the amphoteric monomers, there may be mentioned the acrylate methosulfonate of ethyltrimethyl ammonium. The cationic monomers, the amphoteric monomers and the neutral monomers from A to E defined in the preceding description, can be included in the homopolymers or copolymers, in any proportions, that is to say that they have, for each one, from 0 to 100 mole%. The invention also proposes the use as additives of the copolymers resulting from the combination of at least one of the monomers described above (cationic monomer, amphoteric monomer and / or neutral monomer from [A] to [E]), with at least one anionic monomer (or negatively charged) and / or at least one neutral monomer different from those already described above. The anionic monomers considered are more particularly monomers containing carboxylate groups or sulfonate groups and more precisely monomers of acrylate, methacrylate, itaconate, 2-acrylamido-2-methyl-propane sulfonate, 2-methacryloyloxy ethane sulfonate, butanoate 3 acrylamido-3-methyl, styrene sulfonate, styrene carboxylate, vinyl sulfonate, maleic anhydride or maleic acid. They may be associated with the cationic monomers, the amphoteric monomers and / or the neutral monomers of [A] to [E] described above, likewise one or more other neutral nitrogenous monomers such as monomers of the acrylamide, alkyl acrylamide or vinyl type. acetamide. In these copolymers, the proportions of cationic monomers, amphoteric monomers, monomers neutral of [A] to [E], of anionic monomers and / or additional neutral monomers, can vary, for each of the monomers, for example from 1 to 99%, more particularly from 10 to 70% mol. The cationic monomers, the amphoteric monomers and the neutral monomers of [C] to [E] described above may still be associated with one or more other neutral nitrogen-containing monomers of the N-vinyl lactam type, in particular N-vinyl 2-pyrrolidone, N-vinyl-d-valerolactam and N-vinyl-e-caprolacta a. In these polymers, the proportions of the cationic monomers, of the amphoteric monomers, of the neutral monomers of [C] to [E] and of the additional neutral monomers, can vary, for each of the monomers, for example from 1 to 99%, and more particularly from 10 to 70% mol. Taking into account the definition of the homopolymers and copolymers given above, regarding the nature of the monomers that can enter their constitution, the homopolymers and copolymers considered in the invention can consist of neutral (cationic) co (polymers). or of the polyanfolites (the latter containing both positively charged monomers and negatively charged monomers).

The polymers described in the invention can be linear or branched. Its mass can vary from 3000 to several million. In the process of the invention, the homo and copolymers such as those described above can be added to the fluid to be treated alone or in the form of mixtures of two or several of them. When several copolymers are used in the mixture, they may be copolymers differing from each other, for example, by the nature of the motifs or portions of at least one type and / or by a composition different from at least one motif or portion and / or for its molecular mass. The homo or copolymers, as well as their mixtures in all proportions, can be added to the fluid to be treated at concentrations which are generally 0.05 to 5% by mass, preferably 0.1 to 2% by mass, with respect to water . On the other hand, the homo or copolymers postulated as additives in the invention can be mixed with one or several alcohols (monoalcohols or polyols) containing, for example, the β carbon atoms, more particularly the mono-, the di- or the tri -ethylene glycol, ethanol or methanol, the latter is the preferred alcohol. This alcohol (or these alcohols) is (are) aggregated (s) in general in proportions having from 0.5 to 20% by mass, preferably from 1 to 10% by mass, with with respect to the water present in the fluid to be treated. The homogen or copolymer (s) considered in the invention can then be previously dissolved in a hydro-alcoholic medium and then added to the medium to be treated., so that final concentrations of homo or copolymers are obtained, which generally have 0.05 to 3% by mass, preferably 0.1 to 1% by mass with respect to the water present in the fluid to be treated. The presence in the medium of the kinetic additive (s) such as the polymers postulated in the invention and of alcohol (s) such as, for example, methanol, allow, by their conjugated actions, to obtain delays in the formation of extremely satisfactory hydrates and this, on the one hand, decreases the amounts of additives used (alcohols and polymers) and, on the other hand, and above all, allows operating in a much lower temperature range. The water-soluble homo-or copolymers considered in the invention can be used in a pure water medium, for example in condensation water, or in a salty medium, for example in the production water. The invention will be better understood with the reading of the following experimentations, in no way limiting. Examples 4 to 9 are given by way of comparison and do not form part of the invention.

Example 1 The experimental procedure of selection of the additives is carried out on tetrahydrofuran hydrates (THF). A solution of pure water / THF (80/20 in mass) formed from hydrates under atmospheric pressure at 4 ° C (see: "Kinetic Inhibitors of Natural Gas Hydrates", Sloan, E.D. et al., 1994). The device used consists of tubes with a diameter of 16 mm, into which 8 ml of a 20% by weight aqueous solution of THF, optionally containing an additive to be tested, are introduced. A glass ball with a diameter of 8 mm is inserted into each tube to ensure a solder or correct union of the solution. The tubes are placed on a rotating agitator, which rotates at 20 revolutions / minute. The latter is placed in a refrigerated room at 2 ° C. The principle of this test is to determine the latency time that precedes the formation of hydrates. These latency times correspond to the interval measured between the moment in which the tubes are introduced into the refrigerated room and the moment in which the formation of the hydrates is observed (appearance of a turbidity). Each series of tests is carried out in the presence of a reference mixture that does not contain a additive, and the latency times provided by an additive correspond to an average of the times measured on 16 tests. Under the operating conditions described above, the pure water / THF solutions have an average latency time of 35 minutes. Under operating conditions placed on site or in operation, the addition of 0.5% by mass of a copolymer containing 10% by mol of the dimethyl-amino-ethyl methacrylate (MADAME) or 90% by mol Acrylamide (AA) motifs or portions multiply the latency times by approximately 4.5, the addition of 0.5% by mass of a poly (methacrylate-ethyltrimethyl ammonium chloride) (MAC) leads as far as itself, to a induction time which is on average more than 7 times higher than that of pure water. The addition of 0.3% by mass of a copolymer containing 55 mol% of motifs or portions of acrylamide (AA) and 45 mol% of motifs or portions of diallyl-dimethyl ammonium chloride (DADMAC) makes it possible to multiply by more latency time. Finally, the addition of 0.5% by mass of poly (acrylate-ethyl-trimethyl ammonium methosulfate) or the addition of 0.3% by mass of a copolymer containing 50% by mole of motifs or portions of N-vinyl-2- pyrrolidone (NVP) and 50% by mol of motifs or portions of chloride methacrylate-ethyl-trimethyl ammonium (MAC) or still a copolymer containing 32 mol% of motifs or portions of [3- (2-acrylamido-2-methyl-propyl-dimethyl-ammonium) -1-propan sulfonate] ( AMPDAPS) and 68% by mole of motifs or portions of acrylamide (AA) inhibits the formation of THF hydrates for a period exceeding 6 hours. In the same way, the addition of a mixture of the type DADMAC + AA / MADAME (70/30 in mol) in a ratio 60/40 by mass, at a concentration of 0.3% by mass with respect to water, also inhibits the formation of THF hydrates for a period exceeding 6 hours.

Example 2 The experimental procedure of Example 1 is repeated by replacing the pure water with a mixture of pure water + 5% methanol by mass and reducing the temperature of the cooled room to -1 ° C. Under these conditions, the average latent times of the solutions of pure water + 5% methanol / THF in the absence of the additive is 29 minutes.

The addition of 0.15 mass% with respect to water, of a copolymer containing 50 mol% of dimethyl amino-ethyl acrylate (ADAME) motifs or portions, and 50 mol% of acrylic acid motifs or portions (Ac Acrylic) in the water medium + 5% methanol multiplies the latency times by more than 5.

Example 3 The experimental procedure of Example 1 is repeated by replacing the pure water with a 3.5% by mass NaCl solution, the temperature of the cooled room is reduced to 0 ° C. Under these conditions, the average latent times of the NaCl / THF solutions in the absence of the additive is 42 minutes. The addition of 0.5% by mass of a poly (diallyl-dimethyl ammonium chloride) (DADMAC) allows the latency time to be multiplied by approximately 5. The addition of 0.5% by mass of a poly [3- (2-acrylamido-2-methyl-propyl-dimethyl-ammonium) -1-propan sulfonate] (AMPDAPS) allows the latency time to be multiplied by approximately 6. Finally, the addition of 0.5% by mass of a terpolymer containing 50 mol% of motifs or portions of acrylamide (AA), 35 mol% of motifs or portions of methacrylamido-N-propyl trimethyl ammonium chloride (MAPTAC ) and 15% mole of sodium acrylate portions or patterns leads to a latent time more than 7 times higher than that obtained without additive.

The addition of 0.3% by mass of a terpolymer containing 60 mol% of motifs or portions of the acrylamide type, 25 mol% of acrylamido methyl propan sulfonate (AMPS) motifs and 15 mol% of portions or motifs of methacrylamido-N-propyl trimethyl ammonium chloride (MAPTAC) or 0.3% by mass of a PVP / AMPDAPS copolymer (60/40 in mol) inhibit the formation of THF hydrates for a period exceeding 6 hours.

Examples 4, 5, 6, 7, 8 and 9 (comparative) Different additives that come out of the frame of the invention have been tested for comparison in the conditions described above (examples 1, 2 and 3): Ex. 4: Polyvinylpyrrolidone (molecular weight 10 000, 0.5% by mass) Ex. 5: Polyacrylamide (0.5% by mass) Ex. 6: Acrylamide / sodium acrylate copolymer (0.5% by mass) Ex. 7: Tetrabutyl ammonium chloride (0.5% by mass) Ex. 8: HE-300 (terpolymer of N-vinyl-2-pyrrolidone / acrylamido-methylpropanesulfonate / acrylamide: 0.3% by mass) Ex 9: GAFFIX VC-713 (N-vinyl-2-pyrrolidone / N-vinyl-e-caprolactam / dimethylaminoethyl methacrylate, 0.3% by mass) In the test conditions put into operation, these additives have induction times preceding the formation of hydrates, clearly shorter than the substances mentioned in the invention, as shown by the results shown in the table given below.

Example 10 In order to test the efficacy of the products used in the process of the invention, in the presence of methane hydrates, hydrate formation tests have been carried out from gas and water, with the aid of the apparatus described hereinafter. The apparatus has a loop or curl of 6 meters consisting of tubes of internal diameter equal to 7.7 mm, a reactor of 2 liters comprising an inlet and outlet for gas, a suction and a discharge for the mixture of water and introduced additive initially. The reactor allows to put the loop or curl under pressure. The tubes of diameter analogous to those of the loop ensure the circulation of the fluid from the loop or loop to the reactor, and inversely, by the intermediation of a gear pump placed between the two. A cell or sapphire cell integrated in the circuit allows a visualization of the circulating fluid and thus of the hydrates, if they are formed. To determine the effectiveness of the additives according to the invention, the fluid (water and additive) is introduced into the reactor. The installation is carried out immediately under a pressure of 7 MPa. The solution is homogenized by its circulation in the loop or loop and the reactor, then the Loop or loop is isolated from the reactor. The pressure is kept constant by the addition of methane, and a progressive decrease in temperature (0.5 ° C / minute) from 17 ° C to 5 ° C is imposed, which corresponds to the experimental temperature chosen. The principle of these tests is to determine, on the one hand, the formation temperature of the methane hydrates in the loop, and on the other hand the latency times that precede their formation. The latency times correspond to the times measured between the start of the test (circulation of the fluid at 17 ° C) and the detection of hydrate formation (exotherm, high gas consumption). The duration of the tests can vary from a few minutes to several hours: a functioning additive inhibits the formation of hydrates, or keeps them dispersed in the fluids for several hours. In the absence of the additive (medium: deionized water), methane hydrates are formed at a temperature close to 10.0 ° C and after an induction time of 30 minutes. The formation of hydrates leads to an immediate blockage of the circulation of the fluid mixture + the hydrates in the loop or curl. The addition of 0.3% by weight of the terpolymer AA / MPS / MAPTAC (60/25/15) completely inhibits the formation of methane hydrates under pressure conditions and of temperature imposed for this same test after 24 hours of circulation.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following

Claims (15)

1. A method for inhibiting or retarding the formation, growth and / or agglomeration of hydrates within a fluid comprising water and a gas, such as natural gas, petroleum gas or other gases, under the conditions of wherein hydrates can be formed from water and said gas, characterized in that it comprises the incorporation into said fluid of at least one water-soluble homopolymer or copolymer which is derived from at least one nitrogenous monomer selected from cationic monomers, amphoteric monomers and the neutral monomers chosen among - the monomers [A] which corresponds to the general formula [1]: R CH, C R "[1] R 1 N R2 R3 wherein R 'is a hydrogen atom or a methyl group, R "is selected from the divalent groups -COO-, -CO-NH-, -CO-NH-CO-NH- or C6H4-, R? is chosen between the following divalent groups ~ (CH2) n-, with 1 n < 3, -C (CH3) 2 ~, -C (CH3) 2- (CH2) 2- O -CH2-CH (OH) CH2-, R2 is a hydrogen atom or a methyl, ethyl or isopropyl radical, R3 is a hydrogen atom or a methyl or ethyl radical. - the monomers [B] which correspond to the general formula [2] R CH, [2] NH wherein R 'is a hydrogen atom or a methyl group and R4 a group -C (CH3) 2-CH2-CO-CH3 or -CH20H. - the monomers [C] which correspond to the general formula [3] wherein R 'is a hydrogen atom or a methyl group. - the monomers [D] which correspond to the general formula [4]: wherein R 'is a hydrogen atom or a methyl group. - and the monomers [E] which correspond to the general formula [5]: (CH2 = CH- (CH2)) 2-N-R5 [5] wherein, R5 is an alkyl chain CnH2n +? , with 1 < n < 10, or a hydroxyl group or a group (CH2) 2C0-NH.

2. The process according to claim 1, characterized in that said cationic monomers carry at least one quaternary ammonium group.

3. The process according to one of claims 1 and 2, characterized in that said cationic monomers are chosen from: - the monomers [F] which correspond to the general formula [6]: CH, [6] - wherein R 'is a hydrogen atom or a methyl group, R "is chosen from the divalent groups -COO-, -CO-NH-, -CO-NH-CO-NH- or -C6H4-, R? choose between the following divalent groups ~ (CH2) n-, with 1 <n <3, -C (CH3) 2-, -C (CH3) 2- (CH2) 2- or -CH2-CH (OH) CH2-, R2 is a hydrogen atom, or a methyl, ethyl or isopropyl radical, R3 is a hydrogen atom or a methyl or ethyl radical, R, is selected from the methyl, ethyl or benzyl groups and X is a chloride ion or an ion CH3OSO3""; - the monomers [G] which correspond to the general formula [7]: wherein R 'is a hydrogen atom or a methyl group, R7 a group -C (CH3) 2 -CO-CH3, -CH2OH, methyl, ethyl or benzyl and X is a chloride ion or a CH3OS03 ~ ion; - and the monomers [H] which correspond to the general formula [8]: (CH2 = CH- (CH2)) 2-N + -R5R6 X "[8] wherein, R 5 is an alkyl chain C n H 2n + 1, with 1 < n < 10, a hydroxyl group or a group (CH2) 2-C0-NH ", R, is chosen from the methyl, ethyl or benzyl groups and X is a chloride ion or a CH3OS03 ion.

4. The process according to one of claims 1 to 3, characterized in that said amphoteric monomers are chosen from among - the monomers [I], which correspond to the general formula [9]: R ' CH, C Rio R8 G " wherein R 'RYR are either hydrogen atoms or methyl groups, R "is chosen from the divalent groups -COO- or -CO-NH-, R1] L and R12 are chosen from the following divalent groups - (CH2 ) -, with 1 < n < 3, -C (CH3) 2- or -C (CH3) 2 - (CH2) 2 - and G ~ is a negatively charged group of the carboxylate or sulfonate type: - the monomers [J] which correspond to the general formula [10]: CH, = CH 4 wherein R13 is a hydrogen atom or a methyl group, R1 is chosen from the divalent groups - (CH2) n-, with 1 < n < 4, or -CH -C0H4- and G "is a negatively charged group of the carboxylate or sulfonate type; - and the monomers [K] which correspond to the general formula [11]: wherein R 'is a hydrogen atom or a methyl group, R 5 is a divalent group of the type ~ (CH 2) n-, with l < n < 4, and G ~ is a negatively charged group of the carboxylate or sulfonate type.

5. The process according to one of claims 1 to 4, characterized in that at least one copolymer derived from at least one monomer selected from the monomers of [A] to [K] and at least one anionic monomer chosen is involved. among the monomers containing carboxylate groups or sulfonate groups.

6. The process according to claim 5, characterized in that said anionic monomer is selected from the monomers of acrylate, methacrylate, itaconate, 2-acrylamido-2-sulfonate methyl propane, 2-methacryloyloxy ethane sulfonate, acrylamido-3-methyl butanoate, styrene sulfonate, styrene carboxylate, vinyl sulfonate, maleic anhydride or maleic acid.

7. The process according to one of claims 1 to 6, characterized in that at least one copolymer derived from at least one monomer selected from the monomers of [A] to [K] and at least one neutral monomer chosen is involved. among the monomers of the acrylamide, alkyl acrylamide or vinyl acetamide type.

8. The process according to one of claims 1 to 7, characterized in that at least one copolymer derived from at least one monomer selected from the monomers of [C] to [K] and at least one monomer of the type is put into operation. of N-vinyl lactam chosen from N-vinyl-2-pyrrolidone, N-vinyl-d-valerolactam and N-vinyl-e-caprolactam, in the proportions of 1 to 99% mol.

9. The process according to one of claims 1 to 8, characterized in that said polymer has a molecular mass of 3000 to several million.

10. The process according to one of claims 1 to 9, characterized in that said polymer is added to the fluid to be treated at a concentration of 0.05% by mass with respect to water.

11. The process according to one of claims 1 to 10, characterized in that said polymer is added in the fluid to be treated together with an at least one alcohol containing from 1 to 6 carbon atoms.

12. The process according to claim 11, characterized in that said alcohol is chosen from mono-, di-, tricyethylene glycol, ethanol or methanol.

13. The process according to one of claims 11 to 12, characterized in that said alcohol is added in a proportion of 0.5 to 20% by mass with respect to the water present in the fluid to be treated.

14. The process according to one of claims 11 to 13, characterized in that said polymer is previously dissolved in a hydroalcoholic medium and is then added to the medium to treat, so that a final polymer concentration of 0.05 to 3% by mass is obtained with respect to the water present in the fluid to be treated.

15. The process according to one of claims 1 to 14, characterized in that said water-soluble polymer is used in a medium of pure water or in a salty medium.