MXPA06006512A - Zwitterionic polymers comprising betaine-type units and use of zwitterionic polymers in drilling fluids - Google Patents

Abstract

The invention relates to novel polymers comprising betaine-type units and to the use of zwitterionic polymers in drilling fluids, for example, as a clay swelling inhibitor and/or as an accretion-inhibiting agent and/or as a fluid-rheology-controlling agent and/or a filtrate-reducing agent and/or a lubricant.

Description

ZWITTERIONIC POLYMERS THAT INCLUDE BETAINE AND TYPE UNITS USE OF Z-ITTERIONIC POLYMERS IN DRILLING FLUIDS Description of the invention The subject of the present invention consists of new polymers comprising betaine-type units and the use of zwitterionic polymers in drilling fluids, in particular as an agent to inhibit the swelling of clays. . During well drilling operations, in particular wells designed to recover oil and / or underground gas fields, drilling fluids are used designed to lubricate, clean and cool drilling tools and drill head and / or to discharge the material released during drilling operations (clear rocks). Drilling fluids are also used to clean the well. They also provide the necessary pressure to support the well wall before consolidation. Fluids are usually referred to as "drilling mud". After drilling, the well walls are generally consolidated with a cement material. During drilling, rock walls, particularly clayey rocks sensitive to water, have a tendency to swell. Operational problems are related to these clays. The swelling can interfere with the flow of the fluid or the passage of the drilling tool. In addition, the swelling can lead to the disintegration of the wall. This disintegration can cause irregularities in the well and thus create points of mechanical weakness. In addition, the disintegrated clay material is released into the fluid and can present problems of fluid viscosity control: clay materials, in the presence or absence of a high concentration of salts (brine) have a tendency to increase viscosity extensively. This increase can be dangerous: if it becomes too high, the drilling tools are damaged. The well can still become unusable. In addition, cleared clay rocks may have the tendency to aggregate together in the drilling fluid. This phenomenon is determined as an accretion phenomenon. The accretion can interfere with the circulation of the fluids and can mechanically block the drill head (phenomenon of spherical trephine). To solve these problems. It is known to add to the drilling fluids polymers designed to consolidate the walls (consolidation of the hole). Thus, it is commonly used, inter alia, for partially hydrolyzed polyacrylamides (PHPA). It is believed that these polymers form a polymeric film on the surface of the walls, encapsulate more or less the cleared rocks and thus inhibit the hydration and / or disintegration of the clays. However, the performance of these polymers is limited since they have the tendency to return to excessively viscous fluids at high concentration. In addition, the performance of these polymers is limited under high-temperature-high-pressure (HTHP) drilling conditions. Furthermore, it is known that other polymers can be added to drilling fluids, for example in order to adjust their rheological properties, in particular in the presence of salts. Thus, some studies have been carried out on copolymers comprising betaine-type units and frequently acrylamide units. Known agents for inhibiting the swelling of clays can still promote the accretion. Thus, copolymers based on acrylamide and based on sulfobetaines or phosphobetaines are disclosed in WO 00/01746 (French Institute of Petroleum). It is indicated herein that these copolymers are effective as viscosifying agents and as agents for modifying the surfaces of suspended particles. Increasingly restrictive legislation is aimed at limiting the use of polymers comprising acrylamide units. Sooner or later, some of these polymers will be suitable for use in some countries. Replacement solutions are necessary. US 5 026 490 discloses other copolymers comprising sulfobetaine units and their use as a deflocculating agent for drilling muds. US 6 346 588 discloses other copolymers comprising sulfobetaine units, the formulation of which in a drilling fluid is facilitated. US 4 607 076 discloses other copolymers comprising sulfobetaine units and their use as a viscosifying agent in the presence of brine. The present invention provides a novel polymer comprising betaine-type units. Another object of the present invention is to provide a polymer that can be used as a clay swelling inhibitor and / or as a filtering reducing agent and / or as a lubricating agent and / or as a 2-in-1 agent for lubrication and for swelling inhibition of clay, for example in drilling fluids, in particular in aqueous or non-aqueous fluids, especially in silicate-based fluids. In addition, the invention provides replacement solutions for polymers comprising acrylamide units. Thus, the invention provides a zwitterionic polymer comprising units comprising a betaine group, characterized in that it comprises: - at least 35 mol% of units comprising a betaine group, the betaine group comprises a cationic group and an anionic group, and - additional units chosen from: - alkoxylated units of the following formula: -CH2-CHR6 [-X2- (CH2-CH2-0) n -R7] - in which: - Rs is a hydrogen atom or a methyl group, - X2 is a group of formula -C0-0-, -CO-NH- or - n is integer or average number greater than or equal to 1, - R7 is a hydrogen atom, an alkyl group or a tristyrylphenyl group, and / o - hydroxylated units of the following formula: -CH2-CHR6 [-X2-R8] - in which: - Rd is a hydrogen atom or a methyl group, - X2 is a group of formula -CO-O-, -CO-NH or -R8 is a hydrocarbon group of at least two carbon atoms comprising at least two -OH groups, preferably in s consecutive carbon atoms. The invention is also concerned with a drilling fluid and more particularly with a drilling fluid for oil and / or gas wells comprising the polymer. The fluid can be in particular a silicate-based fluid. The invention is also concerned with the use of a zwitterionic polymer comprising at least 35 mol% of units comprising a betaine group, the betaine group comprising a cationic group and an anionic group, in a drilling fluid as a swelling inhibitor. . of clay and / or as an accretion inhibiting agent and / or as a piercing consolidating agent that controls the fluid rheology agent and / or as a filtering reducing agent and / or as a lubricating agent, for example as a bore consolidation agent or to inhibit the accretion of cleared perforated rocks (inhibition of the spheric phenomenon) or borehole lubrication or as a 2 in 1 agent for lubrication and consolidation or inhibition of accretion or for inhibition of clay swelling (or borehole consolidation) and inhibition of accretion. The polymer can also be used as a filtrate reducing agent.

Polymer The polymer according to the invention comprises at least two types of units. It is thus a copolymer. The polymer is preferably a random copolymer. According to a preferred embodiment, the polymer does not comprise units other than those mentioned. The polymer preferably exhibits only the units comprising a betaine group and the alkoxylated units or only the units comprising a betaine group and the hydroxylated units. The polymer is thus preferably a binary copolymer, in contrast to a terpolymer. Unless indicated otherwise, when the term "molar mass" is used, the reference shall be to the average molar mass in absolute weight, expressed in g / mol. The latter can be determined by aqueous gel permeation chromatography (GPC), by light scattering (DDL or also MALLS), with an aqueous eluent or an organic eluent (for example dimethylacetamide, dimethylformamide and the like), depending on the composition of the polymer. In the present patent application, the term "unit derived from a monomer" denotes a unit that can be obtained directly from the monomer by polymerization. Thus, for example, a unit that is derived from an ester of acrylic or methacrylic acid does not include a unit of the formula -CH2-CH (COOH) -, -CH2-C (CH3) (COOH) - or -CH2-CH ( OH) -, respectively, for example obtained by polymerization of an ester of acrylic acid, an ester of methacrylic acid or vinyl acetate respectively and then hydrolysis. A unit that is derived from acrylic or methacrylic acid includes for example a unit obtained by polymerization of a monomer (for example, an ester of acrylic or methacrylic acid) and then by reacting the polymer obtained (for example by hydrolysis), to obtain unit of formula -CH2-CH (COOH) - or -CH2-C (CH3) (COOH) -. A unit derived from vinyl alcohol includes, for example, a unit obtained by polymerizing a monomer (for example a vinyl ester) and then by reacting the obtained polymer (for example by hydrolysis), to obtain units of the formula -CH2- CH (OH) -. As the first group of units, the polymer comprises units comprising a betaine group comprising a cationic group and an anionic group. Within these units, the number of positive charges equals the number of negative charges. The units are electrically neutral. These units are zwitterionic units and the polymer is thus zwitterionic. The polymer is thus generally electrically neutral, since the other units are neutral. This is the case for the polyalkoxylated units or the hydroxylated units present in the polymer. The molar ratio of units comprising a betaine group is at least 35%. The betaine group exhibits a permanent anionic charge and a permanent cationic charge within at least one pH range. This permanent anionic charge can be contributed by one or more carbonate, sulfonate, phosphate, phosphonate, phosphinate or ethenolate anions and the like. The cationic charge can. to be contributed by one or more onium or inium cations of the nitrogen family (ammonium, pyridinium, imidazolinium cations), the phosphorus family (phosphonium and the like) or the sulfur family (sulfonium and the like). Preferably the betaine groups are pendant groups of the polymer (they are positioned in a comb-like manner along the macromolecular chain of the polymer). The betaine groups can be represented, in the case of cations of the nitrogen family, by the following formulas (I) to (V), which exhibit a cationic charge in the center of the functional group and an anionic charge at the end of the functional group and formula (VI), which exhibits an anionic charge at the center of the functional group and a cationic charge at the end of the functional group: - (3) C «? ñ * -A »O * (H) ~. { R) C -Wjflf? -R-A-O) - W (RKR £.}. -R- W (V) -R-A * (-Ow) -R-N ^ tR'MR ^ 7) (VI) - in which formulas (I) to (IV); the symbols R1, R2 and R5, which are identical or different, represent an alkyl radical comprising from 1 to 7 carbon atoms, preferably from 1 to 2 carbon atoms, the symbols R3 and R4 represent hydrocarbon radicals forming, with the nitrogen atom, a nitrogenous heterocycle optionally comprising one or more other heteroatoms, in particular nitrogen, - the symbol Rd represents a hydrocarbon radical forming, with the nitrogen atom, a saturated or unsaturated nitrogenous heterocycle optionally comprising one or more of other heteroatoms, in particular nitrogen, - the symbol R represents a linear or branched alkylene radical comprising from 1 to 15 carbon atoms, preferably from 2 to 4 carbon atoms, optionally substituted by one or more hydroxyl groups or a ylene radical , the symbol A represents S (= 0) (= 0), 0P (= 0) (0), 0P (= 0) (0R '), P = (0) (OR') or P (= 0) ( R '), where R' represents an alkyl radical comprising from 1 to 7 carbon atoms or a phenyl radical, - in which formula (V): - the symbols R1, R2 and R have the definitions given above, the symbol W represents a functional group ethenolate of the formula: C (0 (")) = C (C = N) 2 0-C (0) -C (_) (C = N) 2 0-C (0) -C (-C = N) (= C = NM) - in which formula (VI): - the symbols R1 and R2 have the definitions given above, - the symbol R7, which is identical or different from R1 or R2, represents an alkyl radical comprising from 1 to 7 carbon atoms; carbon, preferably from 1 to 2 carbon atoms, - the symbol A 'represents -0-P (= 0) -0 ~. In the case of cations of the phosphorus family, mention may be made of the betaine groups of formulas (VII) and (VIII): -P + > (R1 (R2) -R-A-0 <-) (VID -R-A-- (-oM) -R-P (+) (R1) (R2) (R7) (vi11) - in which formula (VII) the symbols R1, R2, R and A have the definitions given above, - in which formula (VIII): the symbols R1, R2, R7 and R and A have the definitions given above, - the symbol A 'represents -0-P (= 0) -0 ~. In the case of cations of the sulfur family, mention may be made of the betaine groups of formula (IX) and (X): -S (+) (R1) -R-A-O'- '(IX) -R-A' (-O'- ') -R-St + > (R1) (R2) (X) - in which formula (IX) the symbols Rx, R and A have the definitions given above, - in which formula (X): - the symbols R1, R2 and R have the definitions given above, - the symbol A 'represents -0-P (= 0) -0-. The units comprising a betaine group and optionally the alkoxylated and / or hydroxylated units preferably form a polyalkylene hydrocarbon chain (also referred to as a backbone chain), optionally interrupted by one or more nitrogen or sulfur atoms. The betaine groups may be connected to the carbon atoms of a hydrocarbon chain of the polymer via in particular a divalent or polyvalent hydrocarbon unit (eg, alkylene or arylene) optionally interrupted by one or more heteroatoms, in particular oxygen, a unit of ester, an amide unit or otherwise by a valence bond. In the polymer, the body of units comprising a betaine group may be composed of identical or different units. The polymer can in particular be obtained by radical polymerization in aqueous solution of monomers comprising a monomer of formula: CH2 = CHR6 [-X- (CH2-CH2-0) n-R7] or a monomer of formula CH2 = CHR6 [ -X2-R8] and of monomers comprising an ethylenically unsaturated betaine group, in particular ethylenically unsaturated monomers bearing at least one betaine group of the above formula (I) to (X).

The monomers may exhibit, by way of example: - one or more mono- or poly-unsaturated hydrocarbon radicals (in particular vinyl, allyl, styryl and the like), one or more mono- or polyethylenically unsaturated ester radicals (in particular acrylate, methacrylate, maleate and the like), one or more mono- or polyethylenically unsaturated amide radicals (in particular acrylamido, methacrylamido and the like). The units comprising a betaine group may be derived from at least one betaine monomer selected from the group consisting of the following monomers: alkyl sulfonates or phosphonates of alkyl acrylates or dialkylammonium methacrylates, acrylamido or methacrylamido, such as: sulfopropyldimethylaminoethylmethacrylate, sold by Raschig under the name SPE: - sulfoethyldimethylammonioethyl methacrylate and sulfobutyldimethylammonioethyl methacrylate: the synthesis of which is described in the document "Sulfobetaine zwitterionomers based on n-butyl acrylate and 2-ethoxyethyl acrylate: monomer synthesis and copolymerization behavior", Journal of Polymer Science, 40, 511-523 (2002), - sulfohydroxypropyl dimethylammonioethyl methacrylate: - Sulfopropyldimethylammoniopropylacrylamide: the synthesis of which is described in the document "Synthesis and solubility of the poly (sulfobetaine) s and the corresponding cationic polymers: 1. Synthesis and characterization of sulphobetaines and the corresponding cationic monomers by nuclear magnetic resonance spectra", Wen-Fu Lee and Chang-Chang Tsai, Polymer, 35 (10), 2210-2217 (1994), -sulfopropyldimethylammonium propylmethacrylamide, sold by Raschig under the name SPP: ÍS) - sulfohidroxipropildimetilamoniopropyl methacrylamide Sulfopropyl diethylammonium ethyl methacrylate: the synthesis of which is described in the document "Poly (sulphopropylbetaines): 1. Synthesis and characterization", V. M. Monroy Soty and J. C. Galin, Polymer, 1984, Vol. 25, 121-128, - sulfohydroxypropyl diethylammonioethyl methacrylate: - heterocyclic betaine monomers, such as: - sulphobetaines derived from piperazine: the synthesis of which is described in the document "Hydrophobically Modified Zwitterionic Polymers: Synthesis, Bul Properties, and Miscibility with Inorganic Salts ", P.

Koberle and A. Laschewsky, Macromolecules, 27, 2165-2173 (1994), - sulfobetaines derived from 2-vinylpyridine and 4-vinylpyridine, such as: 2-vinyl-1- (3-sulfopropyl) pyridinium betaine (2SPV), sold by Raschig under the name SPV: 4-vinyl-l- (3-sulfopropyl) pyridinium betaine (4SPV), the synthesis of which is disclosed in the document "Evidence of ionic aggregates in some ampholytic polymers by electron microscopy transmission", V. M. Castaño and A. E. González, J.

Cardoso, O. Mañero and V. M. Monroy, J. Mater. Res., 5 (3), 654-657 (1990): 1- vinyl-3- (3-sulfopropyl) imidazolium betaine; the synthesis of which is described in the document "Aqueous solution properties of a poly (vinyl imidazoliupt sulphobetaine)", JC Salomone, W. Volkson, AP Oison, SC Israel, Polymer, 19, 1157-1162 (1978), alkyl sulfonates or dialkylammonium alkyl allyl phosphonates, such as sulfopropyl methyldiallylammonium betaine: the synthesis of which is described in the document "New poly (carbobetaine) s made from zwitterionic diallylammonium monomers", Favresse, Philippe; Laschewsky, Andre, Macromolecular Chemistry and Physics, 200 (4), 887-895 (1999), dialkylammonium alkyl sulfonates or phosphonates alkyl styrenes, such as: The synthesis of which is described in the document "Hydrophobically Modified Zwitterionic Polymers: Synthesis, Bulk Properties, and Miscibility with Inorganic Salts", P. Koberle and A. Laschewsky, Macromolecules, 27, 2165-2173 (1994), - resulting betaines of ethylenically unsaturated anhydrides and dienes, such as: the synthesis of which is described in the document "Hydrophobically Modified Zwitterionic Polymers: Synthesis, Bulk Properties, and Miscibility with Inorganic Salts", P. Koberle and A. Laschewsky, Macromolecules, 27, 2165-1273 (1994), - phosphobetaines, such as: (MPC) or alternatively: The synthesis of MPC and VPC is revealed in EP 810 239 Bl (Biocompatibles, Alister et al.). betaines resulting from cyclic acetals, such as ((dicyanoethanolate) ethoxy) dimethylammoniumpropyl methacrylamide: the synthesis of which is described by M-L. Pujol - Fortín et al. in the document "Poly (ammonium alkoxy-dicyanatoethenolates) as new hydrophobic and highly dipolar poly (zwitterions) 1. Synthesis", Macromolecules, 24, 4523-4530 (1991). The polymer according to the invention can also be obtained in a known manner by chemical modification of a polymer referred to as the precursor polymer. Thus, the sulfobetaine units can be obtained by chemical modification, using a sultone (propane sultone, butane sultone), a haloalkylsulfonate or any other sulphonated electrophilic compound of a polymer comprising pendant amine functional groups. A few synthetic examples are given later in the present: twenty The main routes of access by chemical modification of a precursor polymer by sultones and haloalkylsulfonates are described in particular in the following documents: - "Synthesis and aqueous solution behavior of copolymers containing sulfobetaine moieties in side chains", I.V. Berlinova, I.V. Dimitrov, R.G. Kalinova, N.G. Vladimirov, Polymer, 41, 831-837 (2000"Poly (sulfobetaine) s and corresponding cationic polymers: 3. Synthesis and dilute aqueous solution properties of poly (sulfobetaine) s derived from styrene-maleic anhydride", Wen-Fu Lee and Chun -Hsiung Lee, Polymer, 38 (4), 971-979 (1997) "Poly (sulfobetaine) s and corresponding cationic polymers." VIII Synthesis and aqueous solution of a cationic poly (methyl iodide quaternized styrene-N, N-dimethylaminopropyl maleamidic acid) copolymer ", Lee, Wen-Fu and Chen, Yan-Ming, Jornal of Applied Polymer Science, 80, 1619-1626 (2001) -" Synthesis of polybetaines with narrow molecular mass distribution and controlled architecture ", Andrew B. Lowe, Norman C. Billingham and Steven P. Armes, Chem. Commun. , 1555-1556 (1996) "Synthesis and Properties of Low-Polydispersity Poly (sulfopropylbetaine) s and Their Block Copolymers", Andrew B. Lowe, Norman C. Billingham and Steven P. Armes, Macromolecules, 32, 2141-2146 (1999) ) - Japanese patent application published on December 21, 1999 under number 11-349826. The preparation of polyphosphonate- and phosphinatebetaines by chemical modification is reported in "New polymeric phosphonate-, phosphinate- and carboxybetaines", T. Hamaide, Macromolecular Chemistry, 187, 1097-1107 (1986). According to a preferred embodiment, the units comprising a betaine group exhibit one of the following formulas: • -fCfi ~ ~? " - (SPE) - or © 10 -? SHPP) - The polymer according to the invention can also comprise alkoxylated units of the following formula: -CH2-CHE6 [-X2-. { CE2 ~ m2-Q) - wherein: - R6 is a hydrogen atom or a methyl group, - X2 is a group of formula -C0-0-, -CO-NH- or - CHsH4-CH -, - n is an integer or average number greater than or equal to 1, - R7 is a hydrogen atom, an alkyl group or a tristyrylphenyl group. Preferably, the alkoxylated units are units derived from a monomer of the following formula: -CH2 = CHCH3C00- (CH2-CH2-0) n -R7 in which: - n is an integer number or average number greater than or equal to 1, - R7 is an alkyl group comprising 1 to 30 carbon atoms or a tristyrylphenyl group. According to a first preferred form, the monomer is such that: - n is greater than or equal to 10, preferably greater than or equal to 15, and - R7 is a methyl group. Mention is made, as an example of alkoxylated monomer for this first embodiment, of α-monomethacrylate? -methoxy PEG 1000, for example, Bisomer S10W sold by Laporte, in which n is equal to about 22. According to a second preferred form , the monomer is such that: - n is greater than or equal to 10, and - R7 is an alkyl group comprising from 12 to 30 carbon atoms, preferably from 18 to 25. Mention is made as an example of alkoxylated monomer, for this second embodiment, Sipomer BEM sold by Rhodia, in which n is equal to approximately 25 and the number of carbon atoms is 22. According to a third preferred form, the monomer is such that: - n is greater than or equal to 10, and - R7 is a tristyrylphenyl group. Mention is made, as an example of alkoxylated monomer for this third embodiment, of Sipomer SEM 25 sold by Rhodia, in which: - n is equal to about 25. According to a fourth preferred form, the monomer is such that: - n is greater than or equal to 10, and - R7 is a hydrogen atom. The polymer according to the invention can also comprise hydroxylated units of the following formula: -CH2-CHR6 [-X2-R8] - in which: - Rs is a hydrogen atom or a methyl group, - X2 is a group of -C0-0-, -CO-NH or - C6H -CH2-, - R8 is a hydrocarbon group of at least two carbon atoms comprising at least two -OH groups, preferably at two consecutive carbon atoms. They can be, for example, units of formula: wherein R and the group Re, hydrogen or methyl group. The following units are mentioned -iGMAn} * ' { MMf Mention may be made, as an example of resulting monomers in such units after (co) polymerization, of glycerol monoacrylate (GMAc) or glycerol monomethacrylate (GMMA, sold by Rohm): S Aü dMWIA Hydroxylated units can also be obtained by chemical modification of a precursor polymer comprising, for example, epoxy units: Mention may be made, as an example of monomers resulting in such units after the (co) polymerization, of glycidyl acrylate (GA) or glycidyl methacrylate (GMA): The weight average molecular weight is preferably between 5000 g / mol and 400,000 g / mol (relative value, calibrated in aqueous GPC with poly (ethylene oxide) standards.) The average molecular mass in absolute weight can preferably be between 10,000 and 4,000,000 g / mol According to an advantageous embodiment, the polymer comprises: - from 65 to 99% by mol of units comprising a betaine group, - from 55 to 1% by mol of alkoxylated units, preferably: - from 70 to 90% by mol, preferably from 80 to 90% by mol, of units comprising a betaine group, from 10 to 30% by mol, preferably from 10 to 20% by mol, of alkoxylated units. In another advantageous embodiment, the polymer comprises: 80 to 100% mol (excluding) units comprising a betaine group, 20 to 0 mol% (exclusive) of hydroxylated units.

Perforation Fluids The invention is concerned, in accordance with another aspect with a preparation fluid comprising the polymer.

It can be an aqueous or non-aqueous fluid. It can be a silicate-based aqueous fluid (or "silicate-based mud") or silicate-free aqueous fluid. It can be an aqueous fluid based on phosphate or free of phosphate. Phosphate free fluids and silicate free fluids may be concerned. The polymer content of the drilling fluid is advantageously between 0.1% and 10%, preferably between 0.1% and 5% and more preferably still between 1% and 3%. Polymers comprising hydroxylated units are particularly advantageous for aqueous silicate-based fluids or uses in these fluids. Polymers comprising alkoxylated units are particularly advantageous for silicate-free aqueous fluids. A brief description of the drilling operations is given below. The drilling operations consist in digging a hole using a hole or trephine, made in particular of tungsten carbide, attached to hollow tubes screwed from end to end. In general, slurry or drilling fluid, comprising additives in a liquid vehicle is injected into the tube chain. This sludge subsequently returns via the borehole, to the outside of the tubes and transports separated rock components during the drilling operation. At the same time, the mud loaded with rocks establishes a back pressure that consolidates the hole. The mud is subsequently extracted from the drill hole in order to be released from the rocks that are present in it before being reinjected into the hollow drill pipes. Under such operating conditions, the additives added to the mud confer a specific rheological behavior to it. This is because, when subjected to very high shearing stresses and high temperatures, as is the case in the trephine, the fluid has to have a sufficiently low viscosity to facilitate the discharge thereof towards the outside of the hollow tubes. The contrast, the same fluid, loaded with rocks, has to exhibit a high viscosity in order to keep the cuts dragged during drilling in suspension. Drilling fluids (slurries) are known to the person skilled in the art. The exact composition of the fluid may depend on the fate of the fluid. It may depend in particular on the temperatures and pressures at which the fluid will be subjected, of the nature of the rocks through which the well passes and the nature of the drilling equipment. The drilling fluids further comprise a liquid vehicle and additives dissolved or dispersed in the liquid vehicle. Borehole consolidation agents and filtrate reducing agents are such additives. In a liquid vehicle it can be water (the drilling fluid is a water-based composition comprising additives dissolved or dispersed in water). In this case, the term "water mud" is frequently used. It should be mentioned that water is frequently seawater. According to a specific form, the liquid vehicle is a silicate-based vehicle ("silicate-based mud"). Silicate-based sludge is a category of water sludge comprising silicates. They are known to the person skilled in the art. These sludges are highly effective in terms of protecting the clays sensitive to water, they are not very expensive and are considered to have a low impact on the environment. They are able to block fissures in clays with a size of a few nanometers to tens of microns. However, they have disadvantages in terms of the accretion of the cuts and blocking of the drill heads (rounding of the hole). Another disadvantage is the high operational pH (approximately 12), which causes risks in terms of safety of working conditions and / or impact on the environment, also as poor lubrication. Liquid sodium or potassium silicates are solutions of water-soluble glasses with the chemical formula: M2On (Si02), where M can be Na + or K + and n is the molar ratio (the number of Si02 molecules per molecule of M20). n preferably ranges from 1.5 to 3.3 for commercial products. In drilling fluids, the proportion of 2.0 is commonly used. It is believed that silicates protect natural clays sensitive to water from invasion by water via two mechanisms: - gelation: the fluid in the pores of the clays has a pH close to neutral. When the silicate oligomers are brought to this pH, they polymerize and form three-dimensional networks. precipitation: the fluid in the pores of the clays comprises Ca2 + and Mg2 + cations that interact with the silicate oligomers to form insoluble precipitates. The liquid vehicle can also be a water-in-oil emulsion. In this case, the term is often used "oil mud". The latter are more expensive than water sludge but may be preferred in the case of drilling very deep wells (HP / HT (high pressure / high temperature) conditions). The polymer can be used with both types of vehicles. However, water-based vehicles (water mud) are preferred, in particular silicate-based vehicles (silicate-based mud). The polymer according to the invention can participate in the composition of the drilling fluid by replacing or complementing a bore consolidation agent and / or filtering reducing agents and / or lubricating agents and / or accretion inhibiting agents.

Mention should be made of among the additives that can be included in the drilling fluids, in addition to the borehole consolidation agents and / or filtering reducing agents of: - agents to control the rheology: they can be agents that return to the viscoelastic fluid , cutting slimming agents or thickening agents. Mention should be made, for example, of polyscarides, such as guar gum or starch, xanthan gums and derivatives of these compounds. - agents to control the ionic strength of the fluid.

They are for example salts. - emulsifiers, in particular in oil sludges, for example the emulsifiers disclosed in patent application WO 01/94495. - dispersants. - scale inhibitors, for example polymers comprising units derived from acrylic acid or vinylsulfonic acid. - agents for controlling the density of the fluid, for example various sulphate. - oxygen scavengers and / or other chemical stabilizers. However, additional details with respect to certain compounds that can participate in the composition of drilling fluids are given below.

The drilling fluids may comprise polyphosphates, tannins, lignosulfonates, lignin derivatives, peat and lignites, polyacrylates or polinaphthalenesulfonates, alone or as a mixture. The amount of thickening or dispersing agent may vary. By way of indication, this amount is between 0 and 1%, with respect to the total weight of the fluid. The drilling fluid according to the invention may additionally comprise an oxygen scavenger. The purpose of this type of additive is to purify the oxygen present in the drilling muds, which can effect the decomposition of certain additives. Mention may be made, among products of this type, for example of hydroxylamines, hydrazine, sulphites, bisulfites, dithionites or borohydrides. According to a specific embodiment, hydrazine is used as an oxygen scavenger since it does not effect the formation of insoluble precipitates that promote the appearance of blockages in the well. The hydrazine can be in anhydrous or hydrated form, in the form of salts such as for example the chlorite or sulfate or also the carbohydrazide form. In general, the additive content of this type varies between 0 and 0.25%. The drilling fluid according to the invention may further comprise at least one weighting compound and / or at least one inorganic colloid. The weighing components contribute to maintaining a sufficient hydrostatic pressure in the well and keeping suspended the rocks dragged during the drilling operation. Such compounds are conventionally chosen from the soluble salts mentioned above and salts of low solubility or very low solubility. Mention may be made, among salts of low solubility, without pretending to be restricted thereto of alkaline earth metal sulfates, silicates or carbonates, such as barium sulfate or calcium carbonate. It is also possible to use alkaline earth metal or zinc bromides, such as potassium bromide or zinc bromide. You can also make use of iron oxides or sulfur or iron sub-arsenate. Strontium sulfate can also be used although it certainly, in some cases of high density of galen (lead sulphide). Inorganic colloids, which are substantially insoluble compounds under the conditions of use of the fluid according to the invention are agents that modify the rheology of the medium and which make it possible to keep the cuts in suspension in the latter. Atapulgite, barite or bentonite, alone or as a mixture, are the most commonly used examples of them. It should be noted, if use is made of a fluid comprising an inorganic colloid, the latter will preferably be attapulgite. The content of weighing compounds and inorganic colloids depends on several factors that are not only technical. This is because, insofar as these contents are determined very clearly according to the nature of the fund through which the well passes, the scale of the cost generated by the use of these additives is taken into account (presence or absence of the point, cost and the like). Very often and still with the aim of minimizing the expenses incurred, the preparation of the drilling fluid is carried out with the water present in the drilling site. Thus, it is common to have formation water available (in contrast to water types of composition, ie with water types prepared for a specific purpose) loaded with salts, such as seawater, types of brine water or types of water hard. In this case, the content of salts in the water used varies according to the origin of the latter. However, it can happen that the available water is drained of water or water that is not significantly charged. In this case, it may be appropriate to add salts such as chlorides, for example. It is also possible, if necessary, to add inorganic salts in order to promote the precipitation of certain ions, if present, in particular divalent ions. Mention can be made, for example, of the addition of sodium carbonate, in order to precipitate calcium bicarbonate or sodium bicarbonate, in order to precipitate lime, in particular during re-perforation operations in cement. Mention may also be made of the addition of gypsum or calcium chloride, in order to limit the swelling of clays or the addition of calcium hydroxide or shale lime, in order to separate bicarbonates from sludge contaminated by carbon dioxide. Once again, the salt content depends on the rocks through which the well passes and the types of water available at the operation site and the operations can be carried out in the presence of fluids saturated with salts. Very clearly, the drilling fluid according to the present invention can comprise standard additives of the category of high molecular weight polysaccharides, such as succinoglycan, welan or gelan, for use as viscosifying agents. Other additives that are conventional in applications concerning the exploitation of oil fields can participate in the composition of the fluid. Thus, mention can be made of agents for the transfer of free radicals, such as lower alcohols, thioureas or hydroquinone, biocides, chelating agents, surfactants, antifoaming agents or corrosion inhibitors, for example.

Effects of clay swelling inhibitor During the preparation of wells, particularly during the drilling of wells proposed for the recovery of oil and / or gas, drilling is frequently carried out through clay rocks, in particular through shales. These rocks have a tendency to swell when in contact with drilling fluids, in particular when in contact with aqueous fluids. The swelling is a consequence of the penetration of the fluid into the rocks. Such swelling presents several problems. Swelling along the walls of the well creates protuberances that interfere with the movement of the drilling fluid and the drilling tools. In addition, swelling can result in disintegration, creating bumps along the walls. These prominences and protuberances can create points of mechanical weakness in the well. The disintegrated material is composed of fine platelets that can detrimentally affect the rheological properties of the fluid and thus interfere with its movement and / or block the drilling tool. A clay swelling inhibitor is aimed to prevent the penetration of the fluid into the rocks along the walls and inhibit swelling and / or disintegration. The consolidation of the hole can be a concern. Clear clayey rocks, particularly schists, suspended in fluids can present problems. These suspended rocks can swell, break and thus modify the rheological properties of the fluids, as explained above. A clay swelling inhibitor is targeted to prevent penetration to suspended rocks and / or inhibit disintegration.

Accretion Inhibiting Agent In addition, suspended rocks may have the tendency to aggregate together. The term used is accretion. The formed aggregates can interfere with the movement of fluid and tools. In addition, they can surround the drill head and thus block it (trephine rounding phenomenon). An accretion inhibiting agent for cleared perforated rocks is aimed at preventing these phenomena. It should be noted that a conventional agent can form a film or be adsorbed on the surface of the cleared rocks, without however preventing its agglomeration (accretion) A deficiently appropriate clay swelling inhibitor can still promote this accretion.

There are requirements for agents that combine the inhibition of clay swelling and the inhibition of accretion.

Filtering reducing agent The reduction of the filtrate is the evasion loss of fluid in the well by infiltration to the rocks. The loss of fluid will be avoided for economic reasons (cost of fluid), for reasons of safety and for reasons of productivity. This is because, if the fluid is lacking, the drilling tools may be damaged, due to overheating, poor lubrication or mechanical blockage by poorly discharged rocks and require a temporary stoppage of the drilling operation. In addition, the polymers according to the invention exhibit advantageous rheological properties (increase in viscosity) in the presence of high salt concentrations (brine). Polymers that can be used in particular as 2-in-1 agents or agents of higher value, combining several functions chosen from the following: inhibition of clay swelling and / or consolidation of auger, - inhibition of accretion and / or inhibition of blockade drilling head (inhibition of trephine rounding), - lubrication, - filtrate reduction, - rheology control. The uses as agents 2 in 1 simplify technically and economically the formulations of the fluids. The uses as inhibitors of clay swelling and accretion inhibiting agents are particularly advantageous. They can be used as rheology control agents and 2-in-1 clay swelling inhibitor, thus simplifying the formulations both technically and economically.

Uses As mentioned above, the invention is also concerned with the use in a drilling fluid, as inhibitor of clay swelling and / or as a filtering reducing agent, of a polymer comprising at least 35 mol% of units that comprising a betaine group, the betaine group comprises a cationic group and an anionic group. In the context of this use, all that has been previously indicated with respect to the polymer can be made use of and is not again indicated in the present, the presence of the alkoxylated or hydroxylated units, however being optional. It should be mentioned that the polymer, in the context of this use, preferably does not comprise units other than the units comprising a betaine group and optionally the alkoxylated or hydroxylated units. Advantageously, according to one embodiment, the polymer comprises: - from 65 to 99% by mol of units comprising a betaine group, - from 55 to 1% by mol of alkoxylated units, preferably: - from 80 to 90% by mol of units to be comprise a betaine group, - from 10 to 20% by mole of alkoxylated units. Advantageously, according to another embodiment, the polymer comprises: 80 to 100 mol% (excluded) of units comprising a betaine group, 20 to 0 mol% (exclusive) of hydroxylated units. In aqueous silicate-based drilling fluids, advantageous use is made of the polymer comprising the hydroxylated units. In aqueous silicate-free drilling fluids, use is made of the polymer comprising the alkoxylated units. In the context of the use according to the invention, the drilling fluid is preferably a fluid for drilling a well designed for the recovery of oil and / or gas. The polymer content of the drilling fluid is advantageously between 0.1% and 10%, preferably between 0.1% and 5% and more preferably still between 1% and 3%.

In the context of the use according to the invention, the polymer is a clay swelling inhibitor. This can be a borehole consolidation agent. Thus it can also be or alternatively, an accretion inhibiting agent for clear drilled rocks. In the context of use, the polymer can be, also or alternatively, a filtering reducing agent. Other details or advantages of the invention will become more clearly apparent in light of the examples below, without limiting nature.

EXAMPLES Example 1: Polymer comprising SPE units and poly-alkoxylated units (03VTA003, "SPE / PEG 70/30") A copolymer comprising 70% by number of units that are derived from SPE and 30% by number of units that are derived from Bisomer S10W, with an average molar mass in number NM = 15,000 g / mol and a weight-average molar mass MW = 26,000 g / mol (relative value measured by aqueous GPC with standardization of poly (ethylene oxide) samples) ), is prepared by radical polymerization in a water / ethanol mixture as follows: 5.60 g of SPE (that is, 0.020 mol%) sold by Raschig, 9.45 g of Bisomer S10W (that is, 0.009 mol%) ) sold by Laporte, 398 g of water and 261.90 g of ethanol are charged, at room temperature, to a 1.5 L jacketed multi-necked SVL reactor equipped with a Teflon bonding stirrer and connected to a thermostat. This mixture is subsequently heated to 78 ° C. When this temperature is reached (time recorded as t °), the following is introduced: - all at once (at °): 0.8250 g of ammonium persulfate (that is, 0.004 mol) dissolved in 20 g of water, - continuously for 2 hours 30 minutes (from t ° at ° + 2 hours 30 minutes) using a syringe driver: 2. 4750 g of ammonium persulfate dissolved in 60 g of water, continuously for 2 hours (from t ° to ° + 2 hours) using a syringe driver: a solution containing 50.85 g of SPE (that is, 0.182 moles), 84.15 g of Bisomer S10W (that is, 0.078 moles) and 205.8 g of water. Once the final introduction is complete (at t ° + 2 hours 30 minutes), the reaction medium is maintained at 70 ° C for 1.5 hours. Then the heating stops. When the reactor has returned to room temperature, water is added and then the ethanol is evaporated on a rotary evaporator. The final product is an aqueous solution characterized by a solid content of 27.3 ^ (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours), a pH of 2.0 and Brookfield viscosity of 36 mPa »s (measured with an RV1 spindle at 50 rpm, at temperature ambient) . The average absolute molar masses are also measured: MW = 65,000 g / mol, NM = 8,000 g / mol.

Example 2: Polymer comprising SPE units and poly-alkoxylated units (03VTA002, "SPE / PEG 85/15") A copolymer comprising 85% by number of units that are derived from SPE and 15% by number of units that are derived of Bisomer S10W, with an average molar mass in number NM = 15,000 g / mol and a weight-average molar mass MW = 23,000 g / mol (relative value measured by aqueous GPC with standardization of poly (ethylene oxide) samples), is prepared by radical polymerization in a water / ethanol mixture as follows: 8.90 g of SPE (that is, 0.032 moles) sold by Raschig, 6.09 g of Bisomer S10W (that is, 0.006 moles) sold by Laporte, 403.75 g of water and 261.90 g of ethanol are charged at room temperature to a 1.5 L jacketed multi-jacketed SVL reactor equipped with a Teflon bonding stirrer and connected to a thermostat. This mixture is subsequently heated to 78 ° C. When this temperature is reached (time recorded as t °), the following is introduced: - all at once (at °): 1.0650 g of ammonium persulfate (that is, 0.005 moles) dissolved in 20 g of water, - continuously for 2 hours 30 minutes (from t ° to ° + 2 hours) using a syringe driver: 3.2100 g of ammonium persulfate dissolved in 20 g of water, continuously for 2 hours (from t ° to ° + 2 hours) using a syringe driver: a solution containing 80.3 g of SPE (that is, 0.287 moles), 54.75 g of Bisomer S10W (that is, 0.051 moles) and 169 g of water. Once the final introduction is complete (at t ° + 2 hours 30 minutes), the reaction medium is maintained at 78 ° C for 1.5 hours. Then the heating is stopped. When the reactor has returned to room temperature, water is added and then the ethanol is evaporated in a rotary evaporator. The final product is an aqueous solution characterized by a solids content of 21.9% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours), a pH of 2.0 and a viscosity of Brookfield 31 mPa * s (measured with an RV1 spindle at 50 rpm, at room temperature). The absolute average molar masses are also measured: MW = 57,500 g / mol, NM = 6,500 g / mol.

Example 3: Polymer comprising SPE units and poly-alkoxylated units (03VTA001, "SPE / PEG 92.5 / 7.5") A copolymer comprising 92.5% by number of units that are derived from SPE and 7.5% by number of units that are derived of Bisomer SIOW, with an average molar mass in number NM = 14,000 g / mol and a weight-average molar mass MW = 21,000 g / mol (relative value), is prepared in the same way, at a solids content of 25.3% in weight, in a 70/30 mixture of water / ethanol. The absolute average molar masses are also measured: MW = 54,000 g / mol, NM = 7,500 g / mol.

Example 4: Homopolymer comprising units of SPE (03VTA149, "SPE") A polymer comprising essentially derived units of SPE, with weight-average molar mass MW = 11,300 g / mol (relative value), is prepared to a content of solids of 30% by weight, by radical polymerization in water in the following manner: 90 g of SPE and 403.75 g of water are charged, at room temperature, to a 500 ml three-neck reactor equipped with a consolidation stirrer. of Teflon and submerged in a thermostatically controlled oil bath. The reaction medium is subsequently heated to 98 ° C. When this temperature is reached (time recorded as t °), the following is introduced: - all at once (at °): 1.84 g of ammonium persulfate dissolved in 20 g of water, all at once at + 5 minutes : 1.84 g of ammonium persulfate dissolved in 20 g of water, all at once at + 10 minutes: 1.84 g of ammonium persulfate dissolved in 20 g of water, all at once at + 15 minutes: 1.84 g of ammonium persulfate dissolved in 20 g of water. Once the final introduction is complete (at t ° + 15 minutes), the reaction medium is maintained at 78 ° C for 5 hours 45 minutes (until t ° + 6 hours). The heating is stopped subsequently. The final product is an aqueous solution characterized by a solids content of 30% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours), a pH of 1.5 and a viscosity of Brookfield of 30 mPa »s (measured with an RV1 spindle, at 50 rpm, at room temperature). The absolute molar masses are also measured: PM = ,000 g / mol, NM = 4,000 g / mol.

Example 5: Polymer comprising SPE units and vicinal diol units (03VTA021, "SPE / GMMA 99.9 / 0.1"): A copolymer comprising 99.9% by number of units that are derived from SPE and 0.1% by number of units of GMMA, with an average molar mass in number NM = 22,000 g / mol and a weight-average molar mass MW = 216,000 g / mol (relative value), is prepared by radical polymerization in a water / ethanol mixture as follows: 289.82 g of SPE (ie, 1.073 moles) sold by Raschig, 0.18 g of GMMA (ie, 0.001 mole) sold by Rohm and 430 g of water are charged at room temperature to a jacketed multi-collar SVL reactor of 1.5 L equipped with Teflon bonding stirrer and connected to a thermostat. This mixture is subsequently heated to 80 ° C. When this temperature is reached (time recorded as t °), the following is introduced all at once (at t °): 0.2206 g of ammonium persulfate (that is, 0.001 moles) dissolved in 20 g of water. The reaction medium is maintained at 80 ° C for 6 hours. Then the heating is stopped. The final product is an aqueous solution characterized by a solids content of 41.7% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours). This solution is too viscous for its pH and its Brookfield viscosity to be able to be measured under the same conditions as for the polymers described in the previous examples. The absolute average molar masses are also measured: MW = 2,000,000 g / mol, NM = 900,000 g / mol.

Example 6: Polymer comprising SPE units and vicinal diol units (03VTA022, "SPE / GMMA 95/5"): A copolymer comprising 95% by number of units that are derived from SPE and 5% by number of GMMA units , with a number-average molar mass NM = 44,000 g / mol and a weight-average molar mass MW = 230,000 g / mol (relative value), is prepared by radical polymerization in a water / ethanol mixture as follows: 291.21 g SPE (ie, 1.073 moles) sold by Raschig, 8.79 g of GMMA (ie, 0.055 moles) sold by Rohm, and 430 g of water are charged at room temperature to a 1.5 L jacketed multiple-jacketed SVL reactor with stirrer securing Teflon and connected to a thermostat. This mixture is subsequently heated to 80 ° C. When this temperature is reached (time recorded as t °), the following is introduced all at once (at t °): 0.2253 g of ammonium persulfate (that is, 0.001 moles) dissolved in 20 g of water. The reaction medium is maintained at 80 ° C for 6 hours. Then the heating is stopped. The final product is an aqueous solution characterized by a solids content of 42.8% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours). This solution is too viscous for its pH and its Brookfield viscosity to be able to be measured under the same conditions as for the polymers described in the previous examples. The absolute average molar masses are also measured: MW = 3,400,000 g / mol, NM = 1,600,000 g / mol. Example 7: Homopolymer comprising SHPP units (04CVG031, "SHPP"): The monomer (SHPP) is synthesized and then polymerized, the final polymer is characterized by a weight average molar mass of 200,000 g / mol (relative value). 57.16 g of CHPSNa (sodium chlorohydroxypropyl sulphate), sold by Raschig), that is, 0.291 moles and 943.92 g of water are charged at room temperature to a 1.5L jacketed multi-jacketed SVL reactor equipped with a Teflon bonding stirrer and connected to a thermostat. CHPSNa dissolves in a few minutes with shaking ~ 5 minutes). The pH of this solution is subsequently adjusted to 7.5 using 10% diluted sodium hydroxide solution. Then 47.72 g of dimethylaminopropylmethacrylamide, sold by Rohm, is introduced, that is 0.280 moles. The mixture is heated to 80 ° C and maintained at this temperature for 4 hours. The aqueous solution thus obtained (solution I) is characterized by a solids content of 2.7% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours) and a pH of 8.7. . The NMR analysis "" "H in D20 shows that the tertiary amine monomer has been converted virtually completely to the sulfobetaine monomer: 93% of the dimethylaminopropyl methacrylamide is converted to the SHPP monomer. 36. 67 g of this solution I and 137.5 g of water are charged at room temperature to a 1.5L jacketed multi-necked SVL reactor equipped with a Teflon bonding stirrer and connected to a thermostat. The mixture is heated to 85 ° C. When this temperature is reached (time recorded at °), the following is introduced: continuously for 2 hours (from t ° to ° + 2 hours) using a syringe driver: 330 g of solution I, continuously for 4 hours (from t ° at ° + 4 hours) using a syringe driver: a solution containing 0.313 g of ammonium persulfate dissolved in 45.89 g of water. Once the final introduction is complete (at t ° + 4 hours), the reaction medium is maintained at 85 ° C for 4 hours (from t ° + 4 hours at t ° + 8 hours). The heating is stopped subsequently. The final product is an aqueous solution characterized by a solids content of 18% (calculated by weighing a known quantity of solution before drying and after drying at 115 ° C for 2 hours) and a pH of 6.3. The absolute molar masses are also measured: PM = 880,000 g / mol, NM = 300,000 g / mol.

Example 8: Fluid comprising a polymer An aqueous drilling mud formulation A is prepared comprising the following ingredients: - Salt water comprising 200 g / 1 of NaCl, - NaOH, in order to obtain a pH of 10, - Xanthan gum, 2 ppb (23 P Rhodopol, sold by Rhodia) (or 0.5% weight / volume), - Anti-foaming agent, 0.1% by weight (Bevaloid 6092, sold by Rhodia), - Test additive (polymer according to Examples 1 to 8 or other). A formulation B of the silicate-based drilling mud is prepared comprising the following ingredients: Brine 20% Antifoaming agent (Bevaloid 6092) 0.1% Thickening agent, xanthan gum (Rhodopol 23P, Rhodia) 0.5% Silicates (Silicate 60N20, Rhodia) 5% (dry matter) Test additive (polymer according to examples 1 to 8, or other) 1% or 3% KOH or NaOH, in order to adjust the pH to 12 Recovery test in the cuts Clay particles are used to simulate the cuts. The clay used is Oxford clay, 2-4 mm, sold by Hanson Brick, a highly reactive and dispersive clay.

The particles are screened for a final size distribution of 2-4 mm. 30 g of screened particles are added to 350 ml of the test formulation. The flasks are placed in a rolling oven at 65 ° C for 16 hours (hot rolling). After the lamination, the samples are cooled and the particles are recovered on a screen (2 mm) and washed with a brine solution. The excess formulation is carefully separated using adsorbent paper. The particles are heavy. The particles are dried in an oven at 50 ° C until a stable weight is obtained, in order to have an accurate indication of the water content inside the particles. The particles are again weighed and the percentage of moisture restoration is calculated. The high levels of restoration and low moisture content indicate an inhibiting effect on clay swelling.

Extrusion test Hot lamination is carried out in the presence of the clay particles at 65 ° C for 16 hours, as indicated above. After this, the particles are recovered in a sieve, washed with brine and extruded in a CT 15 compression device from Adamel Lhomargy at a speed of 40 mm / min. The pressure needed to extrude the particles is measured. It depends on the degree of hydration of the particles.

The harder the particles, the higher the pressure, the better the protection with respect to water penetration and thus the better the inhibiting effect on clay swelling.

Results Eight different additives are tested at different concentrations in the fluid according to the example (concentration by weight on a dry basis). the results are given in Table I. Table I Polivis PW, sold by Ava.

Anti-Accretion Test 175 ml of the formulation / sludge and 15 g of the clay particles are placed in 250 ml polypropylene flasks. A pre-weighed steel bar is added to them and the flasks are placed horizontally on moving rollers at room temperature for 1 min. The bar is subsequently removed from the flask and photographed. It is subsequently placed in an oven at 105 ° C at constant weight. The following is calculated:% accretion = weight (g) of dry particles stuck to the bar / weight (g) of the particles used for the test *. * The moisture content is taken into account in order to calculate the starting weight of the clays. The lower the value, the better. The results are presented in Table II below.

Table II

Claims (41)

1. CLAIMS 1. A zwitterionic polymer comprising units comprising a betaine group, characterized in that it comprises: - at least 35 mol% of units comprising a betaine group, the betaine group comprises a cationic group and an anionic group, and - units additional selected from: - alkoxylated units of the following formula: -CH2-CHRS [-X2- (CH2-CH2-0) n -R7] - in which: - Re is a hydrogen atom or a methyl group, - X2 is a group of formula -CO-O-, -CO-NH- or - CgH ~ CH-, - n is integer or average number greater than or equal to 1, - R7 is a hydrogen atom, an alkyl group or a tristyrylphenyl group, and / or - hydroxylated units of the following formula: -CH2-CHR6 [-X2-R8] - in which: - Rs is a hydrogen atom or a methyl group, - X2 is a group of formula -CO -O-, -CO-NH or - CgH -CH -, - R8 is a hydrocarbon group of at least two carbon atoms comprising at least two -OH groups, preferably e on two consecutive carbon atoms.
2. 2. The polymer according to any of the preceding claims, characterized in that the anionic group is a carbonate, sulfonate, phosphonate, phosphinate or ethenolate group and that the cationic group is an ammonium, pyridinium, imidazolinium, phosphonium or sulfonium group.
3. 3. The polymer according to any of the preceding claims, characterized in that the betaine groups are pending groups of the polymer.
4. The polymer according to any of the preceding claims, characterized in that the units comprising a betaine group and optionally the alkoxylated and / or hydroxylated units form a polyalkylene hydrocarbon chain optionally interrupted by one or more nitrogen or sulfur atoms.
5. The polymer according to any of the preceding claims, characterized in that the units comprise a betaine group: - derived from at least one betaine monomer selected from the group consisting of the following monomers: - dialkyl sulphonates or dialkyl phosphonates ammonium alkyl acrylates or methacrylates, acrylamido or methacrylamido, preferably: - methacrylate sulfopropildimetilamonioetilo, - methacrylate sulfoetildimetilamonioetilo, - methacrylate sulfobutildimetilamonioetilo, - methacrylate sulfohidroxipropildimetilamonioetilo, - sulfopropildimetilamoniopropilacrilamida, - sulfopropildimetilamoniopropilmetacrilamida, - methacrylate sulfopropildietilamonioetilo, - sulfohidroxipropildimetilamoniopropilmetacrilamida, - methacrylate sulfohidroxipropildietilamonioetilo , - heterocyclic betaine monomers, preferably: - sulphobetaines derived from piperazine, - sulfobetaines derived from 2-vinylpyridine and 4-vinylpyridine, very particularly 2-vinyl-1- (3-sulfopropyl) pyridinium betaine or 4-vinyl-1- (3-sulfopropyl) pyridinium betaine, - 1-vinyl-3- (3-sulfopropyl) imidazolium betaine, alkyl sulphonates or dialkylammonium alkyl allyl phosphonates, preferably sulfopropylmethyldiallylammonium betaine, alkyl sulfonates or dialkylmonium phosphonates alkyl styrenes, betaines resulting from ethylenically unsaturated anhydrides and dienes, phosphobetaines of the formulas: betaines resulting from cyclic acetals, preferably ((dicyanoethanolate) ethoxy) dimethylammonium propyl methacrylamide; or are derived from the chemical modification of units of a polymer precursor, preferably by chemical modification of a polymer comprising pendant amine functional groups, using a sulphonated electrophilic compound, preferably a sultone.
6. 6. The polymer according to any of the preceding claims, characterized in that the units comprising a betaine group exhibit one of the following formulas: twenty 25
7. 7. The polymer according to any of the preceding claims, characterized in that the alkoxylated units are units derived from a monomer of the following formula: CH2 = CHCH3COO- (CH2-CH2-0) n -R7 in which: - n is an integer or average number greater than or equal to 1, - R7 is an alkyl group comprising 1 to 30 carbon atoms or a tristyrylphenyl group .
8. 8. The polymer according to claim 7, characterized in that: - n is greater than or equal to 10, preferably greater than or equal to 15, and - R7 is a methyl group.
9. 9. The polymer according to claim 7, characterized in that: - n is greater than or equal to 10, and - R7 is an alkyl group comprising from 12 to 30 carbon atoms, preferably from 18 to 25.
10. 10. The polymer according to claim 7, characterized in that: - n is greater than or equal to 10, and - R7 is a tristyrylphenyl group.
11. The polymer according to any of claims 1 to 6, characterized in that: - n is greater than or equal to 10, and - R7 is a hydrogen atom.
12. 12. The polymer according to any of the preceding claims, characterized in that the hydroxylated units are chosen from units of the following formulas: - (GMAo) - - (GMMA) -
13. 13. The polymer according to any of the preceding claims, characterized in that it does not comprise other units, the polymer preferably exhibits only the units comprising a betaine group and the alkoxylated units or only the units comprising a betaine group and the hydroxylated units.
14. The polymer according to any of the preceding claims, characterized in that it exhibits a weight average molecular mass of between 5,000 g / mol and 400,000 g / mol, in relative value, measured by GPC calibrated with poly (ethylene oxide) standards. ).
15. 15. The polymer according to any of the preceding claims, characterized in that it comprises: - from 65 to 99% by mol of units comprising a betaine group, - from 55 to 1% by mol of alkoxylated units, preferably: - from 70 to 901 mol, preferably 80 to 90 mol%, of units comprising a betaine group, from 10 to 30 mol%, preferably from 10 to 20 mol%, of alkoxylated units.
16. 16. The polymer according to any of claims 1 to 14, characterized in that it comprises: - from 80 to 100% in mol (excluded) units comprising a betaine group, from 20 to 0 mol% (excluded) units hydroxylated
17. 17. A drilling fluid characterized in that it comprises the polymer according to any of the preceding claims.
18. 18. The drilling fluid according to claim 17, characterized in that the polymer content is between 0.1% and 10%, preferably between 0.1 and 5% and more preferably still between 1% and 3%.
19. 19. The use, in a drilling fluid, as a clay swelling inhibitor and / or as an accretion inhibiting agent and / or as a rheology control agent of the fluid and / or as a reducing agent of the filtrate and / or lubricating agent , of a polymer characterized in that it comprises at least 35 mol% of units comprising a betaine group, the betaine group comprises a cationic group and an anionic group.
20. 20. The use according to claim 19, characterized in that the polymer further comprises: - additional units chosen from: - alkoxylated units of the following formula: -CH2CHR6 [-X2- (CH2-CH2-0) n-R7] - wherein: - Rs is a hydrogen atom or a methyl group, - X2 is a group of formula -CO-O-, -CO-NH- or - n is an integer number or average number greater than or equal to 1, - R7 is a hydrogen atom, an alkyl group or a tristyrylphenyl group, and / or - hydroxylated units of the following formula: -CH2-CHRe [-X2-R8] - in which: - R6 is a hydrogen atom or a methyl group, - X2 is a group of formula -CO-O-, -CO-NH- or - CsH4-CH-, - R8 is a hydrocarbon group of at least two carbon atoms comprising at least two groups -OH, preferably on two consecutive carbon atoms.
21. 21. Use according to any of claims 19 or 20, characterized in that the anionic group is a carbonate, sulfonate, phosphate, phosphonate, phosphinate or ethenolate group and that the cationic group is an ammonium, pyridinium, imidazolinium, phosphonium or sulfonium group.
22. 22. The use according to any of claims 19 to 20, characterized in that the betaine groups are pending groups of the polymer.
23. 23. The use according to any of claims 19 to 22, characterized in that the units comprising a betaine group and optionally the alkoxylated and / or hydroxylated units form a polyalkylene hydrocarbon chain optionally interrupted with one or more nitrogen atoms or sulfur.
24. 24. The use according to any of claims 19 to 23, characterized in that the units comprise a betaine group: - they are derived from at least one betaine monomer selected from the group consisting of the following monomers: - alkyl sulfonates or phosphonates dialkylammonium alkyl acrylates or methacrylates, I acrylamido or methacrylamido, preferably: - methacrylate sulfopropildimetilamonioetilo, - methacrylate sulfoetildimetilamonioetilo, - methacrylate sulfobutildimetilamonioetilo, - methacrylate sulfohidroxipropildimetilamonioetilo, - sulfopropildimetilamoniopropilacrilamida, - sulfopropildimetilamoniopropilmetacrilamida, - methacrylate sulfopropildietilamonioetilo, - sulfohidroxipropildimetilamoniopropilmetacrilamida, - methacrylate sulfohydroxypropylethylammonioethyl, - heterocyclic betaine monomers, preferably: - sulphobetaines derived from piperazine, - sulfobetaines derived from 2-vinylpyridine and 4-vinyl pyridine, very particularly 2-vinyl-l- (3-sulfopropyl) pyridinium betaine or 4-vinyl-l- (3-sulfopropyl) pyridinium betaine, - l-vinyl-3- (3-sulfopropyl) imidazolium betaine, - alkyl sulfonates or dialkylammonium phosphonates alkyl alyls, preferably sulfopropylmethyldiallylammonium betaine, alkyl sulfonates or dialkylmonium phosphonates alkyl styrenes, -betaines resulting from ethylenically unsaturated anhydrides and dienes, phosphobetaines of the formulas: betaines resulting from cyclic acetals, preferably ((dicyanoethanolate) ethoxy) dimethylammonium propyl methacrylamide, - or are derived from the chemical modification of units of a polymer precursor, preferably by chemical modification of a polymer comprising pendant amine functional groups, using a compound sulfonated electrophilic, preferably a sultone.
25. 25. The use according to any of claims 19 to 24, characterized in that the units comprise a betaine group that exhibits one of the following formulas: 25
26. 26. The use according to any of claims 20 to 25, characterized in that the alkoxylated units are units derived from a monomer of the following formula: CH2 = CHCH3COO- (CH2-CH2-0) n-R7 in which: - n is an integer or average number greater than or equal to 1, - R7 is an alkyl group comprising 1 to 30 carbon atoms or a tristyrylphenyl group.
27. 27. Use according to claim 26, characterized in that: - n is greater than or equal to 10, preferably greater than or equal to 15, and - R7 is a methyl group.
28. 28. The use according to claim 26, characterized in that: - n is greater than or equal to 10, and - R7 is an alkyl group comprising from 12 to 30 carbon atoms, preferably from 18 to 25.
29. 29. The use in accordance with claim 26, characterized in that: - n is greater than or equal to 10, and - R7 is a tristyrylphenyl group.
30. 30. The use according to any of claims 20 to 25, characterized in that: - n is greater than or equal to 10, and - R7 is a hydrogen atom.
31. 31. The use according to any of claims 20 to 30, characterized in that the hydroxylated units are chosen from the units of the following formulas: - (GMAc) - (GMMA) -
32. 32. The use according to any of claims 19 to 31, characterized in that it does not comprise units other than the units comprising betaine groups and optionally the polyalkoxylated and / or hydroxylated units, the polymer preferably exhibits only the units comprising a betaine group and the alkoxylated units or only the units comprising a betaine group and the hydroxylated units.
33. 33. The use according to any of claims 19 to 32, characterized in that the polymer exhibits a weight average molecular mass of between 5,000 g / ml and 400,000 g / mol, in relative value, measured by GPC calibrated with poly standards. (ethylene oxide) .
34. 34. The use according to any of claims 20 to 33, characterized in that the polymer comprises: - from 65 to 99% by mol of units comprising a betaine group, - from 55 to 1% by mol of alkoxylated units, preferably : - from 80 to 90% in mol of units comprising a betaine group, - from 10 to 20% in mol of alkoxylated units.
35. 35. The use according to any of claims 20 to 33, characterized in that the polymer comprises: - from 80 to 100% in mol (excluded) units comprising a betaine group, - from 20 to 0% in mol (excl. ) of hydroxylated units.
36. 36. The use according to any of claims 19 to 35, characterized in that the drilling fluid is a fluid for drilling a well designed for the recovery of oil and / or gas.
37. 37. The use according to any of claims 19 to 36, characterized in that the polymer content of the drilling fluid is between 0.1% and 10%, preferably between 0.1 and 5% and more preferably still between 1% and 3% .
38. 38. The use according to any of claims 19 to 37, characterized in that the clay swelling inhibitor is a borehole consolidating agent.
39. 39. The use according to any of claims 19 to 37, characterized in that the accretion inhibiting agent is an agent that prevents the blockage of a drill head.
40. 40. The use according to any of claims 20 to 37, characterized in that the drilling fluid is a fluid based on aqueous silicate and in that the polymer comprises the hydroxylated units.
41. 41. The use according to any of claims 20 to 37, characterized in that the drilling fluid is a fluid freed from aqueous silicate and in that the polymer comprises the alkoxylated units.