WO2004106457A2

WO2004106457A2 - Aqueous fluid comprising a boronate polymer and a ligand polymer and use thereof in the exploitation of oil and gas deposits

Info

Publication number: WO2004106457A2
Application number: PCT/FR2004/001242
Authority: WO
Inventors: Bruno Bavouzet; Mathias Destarac
Original assignee: Rhodia Chimie
Priority date: 2003-05-23
Filing date: 2004-05-19
Publication date: 2004-12-09
Also published as: FR2855180B1; WO2004106457A3; FR2855180A1

Abstract

The invention relates to an aqueous fluid used in the exploitation of deposits of oil and gas, comprising at least one boronate polymer with at least one boronate function or a precursor, at least one ligand polymer with at least two groups which may react with the boronate group(s) or precursor(s), said groups having a cis arrangement and carried on vicinal atoms or two atoms separated by a supplementary atom, at least one salt which is soluble in the fluid, at a level of at least 0.01 % by weight with relation to the weight of the fluid and less than the limit of solubility of the salt(s) in said fluid. The invention further relates to the use of said fluid as fracturing fluid or as drilling fluid.

Description

AQUEOUS FLUID COMPRISING A BORONATE POLYMER AND A

LIGAND POLYMER AND USE IN THE EXPLOITATION OF

OIL OR GAS DEPOSITS

The subject of the present invention is an aqueous fluid usable in the field of the exploitation of oil or gas deposits, comprising a polymer with boronate functions, a ligand polymer having bonds capable of reacting with the boronate functions and a salt soluble in the aqueous medium, as well as the use of said fluid as drilling fluid, or stimulation fluid, preferably fracturing fluid.

In the field of the exploitation of oil or gas deposits, the use of viscoelastic fluids is known. In some cases, it is desired that these fluids have gel properties which can be degraded by means of simple parameters, such as pH in particular.

Thus, the use is known in such fluids, the use of polysaccharides such as guar, combined with borax. In this way, the hydroxyl groups of several polysaccharide chains react with the borax to create a compound in the form of a gel. The difficulty with this type of gel is that its temperature resistance is limited to that of the polysaccharide used and to the temperature dependence of the complexing state of the borax.

The present invention therefore aims to provide an aqueous fluid used in the field of exploitation of oil or gas deposits, not having the aforementioned drawbacks.

These and other objects are achieved by the present invention, which therefore has as its first object an aqueous fluid used in the exploitation of oil or gas deposits comprising

at least one boronate polymer comprising at least one boronate or precursor function,

- At least one ligand polymer having at least two groups capable of reacting with the boronate or precursor functions; said groups being in the cis position and carried by vicinal atoms or by two atoms separated by an additional atom, - at least one salt soluble in the fluid, present in a content of at least 0.01% by weight relative to the weight of fluid and less than the limit of solubility of the salt or salts in said fluid. It also relates to the use of the above-mentioned aqueous fluid as a fracturing fluid.

Finally, the invention relates to the use of said aqueous fluid as drilling fluid, stimulation fluid, preferably fracturing fluid. The aqueous fluid according to the invention represents an alternative to the use of fluids comprising guar and borax for example. The aqueous fluid according to the invention can quite simply replace the fluids based on guar and borax. It is of particular interest in the context of use under particularly restrictive operating conditions, for example at relatively high temperature. In general, the presence in boron atom compositions of borax can sometimes be considered, rightly or wrongly, as possibly generating ecological or toxicological problems. The fluid according to the invention can therefore represent an alternative to fluids comprising guar and borax: The fluid according to the invention can comprise fewer boron atoms, for similar or improved rheological performances, in comparison with fluids comprising guar and borax.

First of all, the fluid according to the invention has intrinsic viscoelasticity properties different from those of guar borax type associations. Indeed, the association of the boronate polymer with the ligand polymer makes it possible to modify the elasticity, the viscosity of the association, compared to a combination of guar and borax.

In addition, the association has a thermal resistance at least equivalent, or even often improved compared to systems implemented conventionally. Indeed, and without wishing to be limited by such an explanation, the multiplication of anchor points between the boronate polymer and the ligand polymer strengthens the cohesion of the polymer, which will have the consequence of increasing the temperature range at which the association can be implemented without degradation of the viscoelastic properties of the association, and in particular of increasing the maximum temperature beyond which the rheological properties are degraded.

Furthermore, according to one embodiment of the invention, the block structure of certain boronate polymers means that the boronate functions are localized fairly precisely along the polymer chain; it has the consequence of promoting better control of the structure and properties of the association of these boronate polymers with a ligand polymer.

In addition, the bonds between the boronate polymer and the ligand polymer may or may not be favored, depending on the conditions of use of this association, more particularly on the pH, or the presence or absence of a competitive molecule. Consequently, according to these conditions, one can observe a triggering effect of the reaction of the boronate or precursor function with the reactive function, or of destabilization of the link. It is likewise possible, in the case of a ligand polymer of the polysaccharide type for example, to destabilize the gel obtained by the association with the use of enzyme making it possible to degrade the polysaccharide.

However, other advantages will become more clearly apparent from the description and the examples which follow.

As indicated above, the aqueous fluid comprises at least one boronate-functional polymer.

First of all, it is recalled that the boronate functions are functions corresponding to the following formula, -B (OH) 3-, having a counterion such as a monovalent ion chosen in particular from alkali metals. They come from the neutralization of the boronic acid function of formula: -B (OH) 2, a function which is a weak acid which can be neutralized by a strong or weak base. It is specified that the term boronate will be used hereinafter, unless otherwise mentioned, to denote a boronic acid or boronate function in the form of a salt. The term “precursor of boronate functions” denotes functions of boronate ester type -B (OR) 2 where the abovementioned radical R corresponds to an alkyl function, or of borane type -BH3.

Preferably, the polymers used in the context of the present invention are water-soluble or water-dispersible. The term “water-soluble or water-dispersible” denotes polymers which, at 20 ° C., at a concentration of

0.1% by weight in aqueous solution does not show macroscopic phase separation after one hour.

Furthermore, the boronate polymer used in the invention is such that the number of moles of boronate or precursor functions per polymer chain, p, is at least 1, more particularly at least 3, preferably d '' at least 5.

Advantageously, the boronate polymer is such that p is less than the average degree of polymerization, DPn, more particularly less than or equal to 0.5DPn, preferably less than or equal to 0.1 DPn.

More particularly, the boronate polymer is such that the average degree of polymerization is at least 10, more particularly at least 20, preferably at least 50 and is less than or equal to 106.

According to a first variant of the invention, the polymers used in the context of the present invention are random polymers.

According to a second variant of the invention, the polymers are block polymers.

Whatever the variant, the structure of the polymers can be linear, branched (grafted or comb), or of star structure. If the boronate polymer is in statistical form, it may or may not have along the chain a concentration gradient.

If the boronate polymer has a block structure, the number of blocks can advantageously be two or three. Still in the case of such a structure, each of the blocks of the polymer can be either a homopolymer, or a random copolymer, or a copolymer having a concentration gradient.

In addition, in the case of a diblock polymer, preferably only one of the blocks comprises one or more boronate or precursor functions.

In the case of a triblock polymer, according to a first particular embodiment, a block comprises one or more boronate or precursor functions; this block can be located at the end or not of said polymer. According to this mode, the two blocks not comprising boron may or may not be of the same composition. According to another particular embodiment, two blocks of the polymer comprise one or more boronate or precursor functions; said blocks are preferably located at the ends of the polymer. It is further specified that the composition of the two blocks comprising boron may or may not be identical.

Finally, in the case where the polymer according to the invention is of star structure, each of the branches can be either a homopolymer, or a random copolymer, or a block copolymer in the above sense, or a copolymer having a concentration gradient .

It is specified that directly adjacent blocks, whether they constitute the various fragments of a block polymer or of a star structure polymer, are differentiated from each other by the fact that their chemical composition is different. By different chemical composition is meant more particularly that the chemical nature of at least one of the monomers is different from one block to another, and / or that the respective proportions of the monomers from one block to another are different.

It is recalled that the polymer used in the present invention comprises more than ten repeat monomer units.

In addition, in the following text, mention will only be made of polymers, knowing that depending on the context, it may be a copolymer or a homopolymer.

These boronate polymers can be obtained by radical polymerization, controlled (or living) or not, by cationic, anionic polymerization, by ring opening polymerization (in particular anionic or cationic), or by chemical modification of a first polymer (obtained by polymerization radical, condensation, etc.).

The grafted or combed polymers can also be obtained by methods known as direct grafting and copolymerization. The direct grafting consists in polymerizing the monomer (s) chosen (s) by the radical route, in the presence of the selected polymer to form the skeleton of the final product. If the monomer / skeleton couple as well as the operating conditions are judiciously chosen, then there may be a transfer reaction between the growing macroradical and the skeleton. This reaction generates a radical on the skeleton and it is from this radical that the graft grows. The primary radical originating from the initiator can also contribute to the transfer reactions.

As regards copolymerization, it first implements the grafting at the end of the future pendant segment, of a function which can be polymerized by the radical route. This grafting can be carried out by usual methods of organic chemistry. Then, in a second step, the macromonomer thus obtained is polymerized with the monomer chosen to form the skeleton and a so-called "comb" polymer is obtained.

Preferably, the polymer is obtained by implementing a so-called controlled or living polymerization. As examples of polymerization, reference may in particular be made to the following documents:

- Methods of applications WO 98/58974, WO 00/75207 and WO 01/42312 which implement a radical polymerization controlled by control agents of xanthates type,

- radical polymerization process controlled by dithioester type control agents of application WO 98/01478,

- Process of application WO 99/03894 which implements polymerization in the presence of nitroxide precursors,

- radical polymerization process controlled by dithiocarbamate type control agents of application WO 99/31144, - radical polymerization process controlled by dithiocarbazate type control agents of application WO 02/26836.

- radical polymerization process controlled by control agents of the dithiophosphoroesters type of application WO 02/10223,

- Process of application WO 96/30421 which uses radical atom transfer polymerization (ATRP),

- radical polymerization process controlled by iniferters type control agents according to the teaching of Otu et al., Makromol. Chem. Rapid. Commun., 3, 127 (1982),

- radical polymerization process controlled by degenerative transfer of iodine according to the teaching of Tatemoto et al., Jap. 50, 127, 991 (1975), Daikin Kogyo Co

Itd Japan and Matyjaszewski et al., Macromolecules, 28, 2093 (1995), - radical polymerization process controlled by tetraphenylethane derivatives, disclosed by D. Braun et al. In Macromol. Symp. 111, 63 (1996), or

- radical polymerization process controlled by organocobalt complexes described by Wayland et al. In J.Am.Chem.Soc. 116.7973 (1994).

The processes for preparing star-shaped polymers can be essentially classified into two groups. The first corresponds to the formation of the polymer arms from a multifunctional compound constituting the center ("core-first" technique) (Kennedy, JP and coll. Macromolecules, 29, 8631 (1996), Deffieux, A. and coll Ibid, 25, 6744, (1992), Gnanou, Y. and coll. Ibid, 31, 6748 (1998)) and the second corresponds to a method where the polymer molecules which will constitute the arms are first synthesized and then bonded together on a heart to form a star-shaped polymer ("arm-first" technique).

As an example of synthesis of this type of polymer, reference may be made to patent WO 00/02939.

In general, it is preferred that the block polymers used according to the invention come from a controlled radical polymerization process using, as control agent, one or more compounds chosen from dithioesters, thioethers-thiones, dithiocarbamates, and xanthates. In a particularly advantageous manner, the block polymers used according to the invention result from a controlled radical polymerization carried out in the presence of control agents of the xanthat type.

According to a preferred embodiment, the block polymer can be obtained according to one of the methods of applications WO 98/58974, WO 00/75207 or WO 01/42312 which implement a radical polymerization controlled by agents for controlling xanthates type, said polymerization being able to be carried out in particular in bulk, in solvent or in aqueous emulsion.

According to a first embodiment, the polymers are obtained by polymerization in the presence of at least one monomer having one or more boronate or precursor functions. Preferably, said monomers have a boronate or precursor function.

According to another embodiment, the polymers are obtained in two blocks, for example, by controlled or uncontrolled radical polymerization. The process consists, firstly, in preparing a polymer devoid of boronate or precursor functions, then secondly, in introducing the latter once the polymer obtained, by reaction of appropriate groups present on said polymer with at least one compound carrying a reactive group with that or those carried by the polymer and carrying one or more boronate or precursor functions. Thus, according to this latter possibility, the polymer obtained has at least one group reacting with a reactive group present on the compound further comprising the boronate function or functions, in particular by a condensation or addition reaction. For example, the polymer may comprise a carboxylic acid group which will react with an amino function of a boronate reagent, or vice versa.

Thus, a method can be implemented comprising the following steps:

(a) contacting:

- ethylenically unsaturated monomers, - a source of free radicals, and - at least one control agent of formula (I):

S w

C - S - R1 (I)

/ OR in which: R represents:

- H or Cl;

- an alkyl, aryl, alkenyl or alkynyl group; - a carbon cycle, saturated or not, optionally aromatic;

- a heterocycle, saturated or not, optionally aromatic;

- an alkylthio group,

- an alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, or carbamoyl group;

- a cyano, dialkyl- or diaryl-phosphonato, dialkyl- or diaryl-phosphinato group; - a polymer chain,

a group (R ² ) O-, (R2) (R'2) N-, in which the radicals R2 and R'2, which are identical or different, each represent:

- an alkyl, acyl, aryl, alkenyl or alkynyl group;

- a carbon cycle, saturated or not, optionally aromatic; or - a heterocycle, saturated or not, optionally aromatic; and

R1 represents:

an alkyl, acyl, aryl, alkenyl or alkynyl group,

- a carbon cycle, saturated or not, optionally aromatic;

- a heterocycle, saturated or not, optionally aromatic; or - a polymer chain,

(b) a step of controlled radical polymerization is carried out, following step (a), or several successive steps of controlled radical polymerization, in which each step is brought into contact: - ethylenically unsaturated monomers different from those used in the previous step,

- a source of free radicals, and

- The functionalized polymer from the previous step. It is understood that one of the polymerization steps (a) and (b) defined above leads to the formation of the anchoring block, and that another of the polymerization steps of steps (a) and (b) leads to the formation of another block.

It should in particular be noted that the ethylenically unsaturated monomers used in steps (a) and (b) are chosen from the monomers as defined above.

In general, the polymerization steps (a) and (b) are carried out in a solvent medium consisting of water and / or an organic solvent such as tetrahydrofuran or a linear Cj-Cδ aliphatic alcohol, cyclic or branched such as methanol, ethanol, or cyclohexanol, or a diol such as ethylene glycol. Optionally, the polymers synthesized can undergo a reaction for the purification of their sulfur chain end, for example by methods of the hydrolysis, oxidation, reduction, pyrolysis or substitution type.

According to the first variant, the polymer used in the context of the present invention is obtained by radical polymerization, controlled or not, and preferably controlled, in the presence of a portion of at least one monomer comprising a boronate or precursor function and on the other hand, at least one monomer which is devoid of this type of function.

More particularly, the monomer comprising the boronate or precursor function is chosen, for example, from acryloylbenzene boronic acid, methacryloylbenzene boronic acid, 4-vinylbenzene boronic acid, 3-acrylamido phenyl boronic acid, the 3-methacrylamido phenyl boronic acid, alone or in mixtures, or in the form of salts.

As regards the monomer or monomers free of boronate or precursor function, their respective nature and proportion are determined so that the resulting polymer is water-soluble or water-dispersible within the meaning of the invention.

Thus, the monomer or monomers free of the boronate function or its precursor, can be chosen from hydrophobic monomers.

The term “hydrophobic monomer” means a monomer chosen from those which, once homopolymerized with a degree of polymerization of between 40 and 100, give a polymer which is subjected to macroscopic phase decantation, at 25 ° C., at a concentration of 01 at 1% by weight, at the pH of use of the fluid according to the invention. The fluid is generally used at a temperature of 20 to 150 ° C, at a pH of 8 to 10. By way of illustration of this type of monomer, there may be mentioned: the esters of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation, optionally fluorinated, optionally bearing a group hydroxyl, - αβ-ethylenically unsaturated nitriles, vinyl ethers, vinyl esters, vinyl aromatic monomers, vinyl or vinylidene halides, hydrocarbon monomers, linear or branched, aromatic or not, comprising at least one ethylenic unsaturation, alone or in mixtures, as well as the macromonomers derived from such monomers.

It is recalled that the term macromonomer designates a macromolecule carrying one or more polymerizable functions. More particularly, suitable: - esters of (meth) acrylic acid with an alcohol comprising 1 to 12 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate , n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl acrylate; vinyl acetate, vinyl Versatate®, vinyl propionate, vinyl chloride, vinylidene chloride, methyl vinyl ether, ethyl vinyl ether; the vinyl nitriles include more particularly those having 3 to 12 carbon atoms, such as in particular acrylonitrile and methacrylonitrile; - styrene, α-methylstyrene, vinyltoluene, paramethylstyrene or paratertiobutylstyrene, butadiene, isoprene, chloroprene; alone or in mixtures, as well as the macromonomers derived from such monomers.

The preferred monomers are the esters of acrylic acid with linear or branched C1-C4 alcohols such as methyl, ethyl, propyl and butyl acrylate, vinyl esters such as vinyl acetate, styrene, α-methylstyrene. The polymer according to the invention can also be obtained by polymerization of hydrophilic monomers.

The term “hydrophilic monomer” means a monomer chosen from those which, once homopolymerized with a degree of polymerization of between 40 and 100, give a soluble polymer at 25 ° C., at a concentration of 01 to 1% by weight, at pH d use of the fluid according to the invention. The fluid is generally used at a temperature of 20 to 150 ° C, at a pH of 8 to 10.

More particularly, mention is made of the monomers chosen from amides of mono- or polycarboxylic acids, linear, branched, cyclic or aromatic, comprising at least one ethylenic unsaturation or derivatives, such as (meth) acrylamide, N-methyloI (meth) acrylamide; cyclic amides of vinylamine, such as N-vinylpyrrolidone; N-vinyl monomers such as N-vinylcaprolactone, N-vinylcaprolactam, N-vinylacetamide; ethylenic monomers comprising a ureido group such as ethylene urea ethyl (meth) acrylamide, or ethylene urea ethyl (meth) acrylate; hydrophilic esters derived from (meth) acrylic acid such as for example 2-hydroxyethyl (meth) acrylate; vinyl esters making it possible to obtain polyvinyl alcohol blocks after hydrolysis, such as vinyl acetate, vinyl Versatate®, vinyl propionate, alone, in combination, as well as the macromonomers derived from such monomers.

However, the preferred hydrophilic monomers are acrylamide, methacrylamide, N-vinylpyrrolidone, alone or as a mixture, or in the form of a macromonomer. According to another possibility, the polymer according to the invention can be obtained from at least one monomer chosen from monomers comprising at least one carboxylic, sulfonic, sulfuric, phosphonic, phosphoric, sulfosuccinic function, or the corresponding salts.

In particular, the following monomers can be used in the presence of the monomer or monomers comprising the boronate function or its precursor:

- linear, branched, cyclic or aromatic mono- or polycarboxylic acids, N-substituted derivatives of such acids; monoesters of polycarboxylic acids, comprising at least one ethylenic unsaturation;

- linear, branched, cyclic or aromatic vinyl carboxylic acids; - amino acids comprising one or more ethylenic unsaturations; alone or as mixtures, their precursors, their sulfonic or phosphonic counterparts, as well as the macromonomers derived from such monomers; the monomers or macromonomers which may be in the form of salts.

As examples of monomers, there may be mentioned without intending to be limited thereto: - acrylic acid, methacrylic acid, fumaric acid, itaconic acid, citraconic acid, maleic acid, acrylamido glycolic acid, 2-propene 1- sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, α-acrylamido methylpropane sulfonic acid, 2-sulfoethylene methacrylate, sulfopropyl acrylic acid, l bis-sulfopropyl acrylic acid, bis-sulfopropyl methacrylic acid, sulfatoethyl methacrylic acid, hydroxyethyl methacrylic acid phosphate ester, as well as alkali metal salts, such as sodium, potassium, or ammonium; - vinyl sulfonic acid, vinylbenzene sulfonic acid, vinyl phosphonic acid, vinylidene phosphoric acid, vinyl benzoic acid, as well as alkali metal salts, such as sodium, potassium, or ammonium ;

- N-methacryloyl alanine, N-acryloyl-hydroxy-glycine; alone or in mixtures, as well as the macromonomers derived from such monomers.

It would not go beyond the scope of the present invention to use precursor monomers of those which have just been mentioned. In other words, these monomers have units which, once incorporated in the polymer chain, can be transformed, in particular by chemical treatment such as hydrolysis, to restore the aforementioned anionic species. For example, the fully or partially esterified monomers of the aforementioned monomers can be used to be, subsequently, wholly or partially hydrolyzed.

Finally, another possibility consists in carrying out radical polymerization in the presence, in addition to the monomer or monomers comprising the boronate function or its precursor, of at least one monomer chosen from: aminoalkyl (meth) acrylates, (meth) acrylamides aminoalkyl; monomers comprising at least one secondary, tertiary or quaternary amine function, or a heterocyclic group containing a nitrogen atom, vinylamine, ethylene imine; - diallyldialkyl ammonium salts; alone or as mixtures, or the corresponding salts, as well as the macromonomers derived from such monomers.

Said monomers can have a counterion chosen from halides such as, for example, chlorine, sulphates, hydrosulphates, alkylsulphates (for example comprising 1 to 6 carbon atoms), phosphates, citrates, formates, acetates.

Examples of suitable monomers include, among others, the following monomers:

- dimethyl amino ethyl (meth) acrylate, dimethyl amino propyl (meth) acrylate, ditertiobutyl aminoethyl (meth) acrylate, dimethyl amino methyl (meth) acrylamide, dimethyl amino propyl (meth) acrylamide;

- ethylene imine, vinylamine, 2-vinylpyridine, 4-vinylpyridine;

- trimethylammonium ethyl (meth) acrylate chloride, trimethylammonium ethyl acrylate methyl sulfate, benzyl dimethylammonium ethyl (meth) acrylate chloride, 4-benzoylbenzyl dimethyl ammonium ethyl acrylate chloride, trimethyl ammonium ethyl (meth) chloride acrylamido, trimethyl ammonium chloride, vinylbenzyl;

- diallyldimethyl ammonium chloride; alone or as mixtures, or their corresponding salts, as well as the macromonomers derived from such monomers.

In the case of the second variant, the first step consists in preparing a polymer free of boronate or precursor function but comprising groups which will be capable of reacting with at least one compound carrying one or more boronate or precursor functions.

All that has been indicated above remains valid except for the fact that the monomers containing boronate or precursor functions are replaced by monomers carrying one or more functions capable of reacting once the polymer obtained, with a reactive group present in the compound bearing the boronate or precursor function. Among the reactive groups that can be envisaged, mention may be made, inter alia, of carboxylic, amino, hydroxyl groups, alone or in combination.

In accordance with a particular embodiment of the invention, the boronate polymer is a polymer comprising at least one block of hydrophobic nature optionally having at least one hydrophilic unit, and at least one hydrophilic block having at least one hydrophobic unit. Note that the polymer is always water-soluble or water-dispersible within the meaning of the invention.

A hydrophobic unit is such that if the polymer consisted only of such a unit, with a degree of polymerization of between 40 and 100, the polymer would be subjected to macroscopic phase decantation, at 25 ° C., at a concentration from 01 to 1% by weight, at the pH of use of the fluid according to the invention. The fluid is generally used at a temperature of 20 to 150 ° C, at a pH of 8 to 10.

A hydrophilic unit is such that if the polymer consisted only of such a unit, with a degree of polymerization of between 40 and 100, the polymer would be soluble at 25 ° C., at a concentration of 01 to 1% by weight , at the pH of use of the fluid according to the invention. The fluid is generally used at a temperature of 20 to 150 ° C, at a pH of 8 to 10.

Preferably, the block of hydrophobic nature comprises less than 70% by weight of hydrophilic units relative to the weight of the units present in said block, preferably from 1 to 50% by weight.

Furthermore, the block of hydrophilic nature of the polymer preferably comprises 1 to 33% by weight of hydrophobic units relative to the weight of the units present in said block, preferably from 2 to 15% by weight.

It is specified that the boronate or precursor functions are preferably located in the hydrophilic blocks of the polymer.

Advantageously, the mass ratio of the hydrophilic blocks and the hydrophobic blocks of the boronate polymer is between 95/5 and 20/80. As indicated above, the aqueous fluid according to the invention comprises at least one ligand polymer having at least two groups capable of reacting with the boronate or precursor functional group (s); said groups being carried by vicinal atoms (or adjacent atoms, position 1, 2) or by two atoms separated by an additional atom (position 1, 3). Advantageously, the atoms are carbon atoms.

According to another characteristic, said ligand polymer is such that the groups capable of reacting with the boronate or precursor function (s) are in the cis position relative to each other. Preferably, the groups capable of reacting with a boronate function are hydroxyl groups, originating from alcohol and / or carboxylic acid functions, optionally associated with amino groups, more particularly primary or secondary.

Thus the ligand compound may comprise at least one or more sets of at least two hydroxyl groups, originating from alcohol and / or carboxylic acid functions, one or more sets of at least one hydroxyl group, originating from alcohol and / or acid functions carboxylic, associated with at least one amino group, preferably primary or secondary, or the combination of these two possibilities. If the ligand compound is a polymer, the latter comprises more than ten repeating units.

In addition, it is preferably chosen from compounds of which at least one of the monomers from which it is obtained has one or more sets of at least two hydroxyl groups, originating from alcohol and / or carboxylic acid functions, a or several sets of at least one hydroxyl group, originating from alcohol and / or carboxylic acid functions, associated with at least one amino group, preferably primary or secondary, or alternatively the combination of these two possibilities. It can moreover be chosen from compounds of which at least two monomers have at least one hydroxyl group each, or one has at least one hydroxyl group and the other has at least one hydroxyl group or at least one amino group, of so that once the two monomers are combined in the polymer, the two reactive functions are carried either by two vicinal atoms or by two atoms separated by an additional atom.

It is preferred to use polymers having a molar mass by weight greater than or equal to 2000 g / mole, preferably greater than or equal to 20000 g / mole (absolute masses, measured by size exclusion chromatography coupled with the MALLS method). Among the suitable polymers, mention may be made of synthetic polymers such as polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, copolymers comprising dihydroxyethyl (meth) acrylate or alternatively glyceryl (meth) acrylate, for example. Mention may likewise be made of polymers comprising at least one osidic unit.

The monomers and oligomers previously listed are suitable for this embodiment and reference may be made thereto.

With regard to polymers having at least one osidic unit, certain polysaccharides, natural or modified, of animal or vegetable origin, biogums, having the reactive groups described above, are also suitable.

As natural polysaccharides, there may be mentioned, without limitation, alginates, galactomannans such as guar gum, locust bean gum, Tara gum, cassia gum; Karaya gum; carrageenans, in particular λ-carrageenan; chitin derivatives, such as chitosan; starches; glucomannans; dextran; pullulan.

It is likewise possible to use the derivatives of these polymers modified so as to have a cationic character, such as the cationic derivatives of guar or carob (Jaguar® C13S, Jaguar® C162 marketed by RHODIA). It is also possible to use the nonionic derivatives of these polymers, such as hydroxypropylguars, anionic derivatives such as carboxymethylguars, or mixed nonionic / anionic derivatives such as carboxyhydroxypropylguars or nonionic / cationic such as ammonium-hydroxypropyl guars.

As modified polysaccharides which may fall within the scope of the present invention, mention may also be made of cellulose derivatives such as dihydroxypropylcellulose or other hydroxyalkylated derivatives of cellulose.

As biogums which can be used in the context of the association according to the invention, there may be mentioned in particular the polysaccharides obtained by fermentation under the action of bacteria or fungi belonging for example to Xanthomonas, of the genus

Arthrobacter, genus Azobacter, genus Agrobacter, genus Alcaligenes, genus Rhizobium, genus Sclerotium, genus Corticium, genus Sclerotinia.

As examples of biogums, there may be mentioned more particularly xanthan gum, scleroglucans, succinoglycans.

It should be noted that the abovementioned polysaccharides can be used in native form or chemically modified so as to give them an ionic or nonionic character different from the native form.

Among the polymers of which at least one of the monomer units comprises at least one hydroxyl group and one amino group, mention may be made, for example, of certain proteins, or the polymers obtained in particular from amino acids. The same compounds can also be used, generally in the form of water-soluble polymers modified by hydrophobic groups covalently linked to the polymer backbone as described in patent EP 281 360.

Of course, it would not be departing from the scope of the present invention to use as a ligand compound a mixture of one or more of the species described above.

Preferably, as the ligand compound, at least one polymer chosen from polysaccharides such as galactomannans (guar, carob preferably) or glucomannans and their derivatives, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, copolymers comprising

(meth) glyceryl acrylate.

The content of ligand compound in the aqueous fluid is more particularly less than or equal to 5% by weight of fluid, preferably between 0.01 and 0.5%.

In addition, the content of boronate polymer in the fluid is more especially between 0.001 and 1% by weight of the fluid, preferably between 0.01 and 0.5% by weight of the fluid.

Finally, the aqueous fluid according to the invention comprises at least one salt soluble in the fluid, present at a content of at least 0.01% by weight relative to the weight of fluid and less than the solubility limit of the salt or salts in said fluid.

As suitable soluble salts, there may be mentioned, inter alia, chlorides of alkali or alkaline earth metals, iodides, sulfates, carbonates, bicarbonates, phosphates, silicates, of alkali metals, alone or as a mixture. If necessary, and depending on the applications, the fluid can comprise at least one gas such as air, nitrogen, carbon dioxide. It can also include liquefied gases such as liquid carbon dioxide.

The present invention further relates to the use of the aqueous fluid which has just been detailed, as a fluid for the exploitation of oil or gas deposits, such as a drilling fluid or a fluid stimulation. The use is particularly advantageous for the simulation of oil wells, and more particularly for fracturing. The invention therefore preferably relates to the use of the aqueous fluid which has just been detailed, as fracturing fluid. The use as stimulation fluid, according to the invention, and more particularly as fracturing fluid, is particularly advantageous at relatively high operating temperatures, of the order of 120 ° C. to 150 ° C. The pH is generally from 8 to 10, and often above 9. We do not observe, with a fluid according to the invention, significant and / or rapid degradation of the viscoelastic properties, which could make said fluid difficult to use. The fracturing operation can advantageously be a fracturing with carbon dioxide, in which liquid carbon dioxide is injected into the fracturing fluid. The use as a fracturing fluid can advantageously be a use as a fracturing fluid with carbon dioxide, the fluid comprising liquid carbon dioxide.

The use of a fracturing fluid consists of injecting the fluid into the well at a rate, pressure and shear rate sufficient to create cracks in the rocks crossed, and thus increase the permeability of rocks comprising petroleum or gas.

Fracturing techniques are described in particular in US Pat. No. 5,551,516, and in “Oilfield Applications”, Encyclopedia of Polymer Science and Engineering, vol. 10, pp 328-366.

The fracturing fluid generally comprises solid particles whose role is to keep open the cracks created during the fracturing operation. The particles are dispersed, for example in suspension, in the fluid, transported in the cracks. They prevent them from closing again when the pressure decreases in the rock, because of a degradation, suffered or caused, of viscosity of the fluid, or because of a voluntary operation on the flow rate, the pressure or the rate of shear.

More particularly, these solid particles can be chosen from sand, quartz, siliceous quartz, sintered bauxite, glass beads, ceramic beads, aluminum particles, fragments of nutshells, etc. The particle size of these particles is typically 20-40 mesh. Usually, the quantity of solid particles in the fluid is between 0.2 and 0.3 kg of particles per liter of fracturing fluid.

It should be noted that the fracturing fluids can include thermal stabilizing agents, such as for example sodium thiosulfates and thiosulfites, thiourea, methanol, ethylene glycol, isopropanol, etc.

Where appropriate, the fracturing fluid can comprise an additive limiting the swelling of clays, such as, for example, potassium chloride, calcium chloride, calcium sulfate (gypsum) etc. Generally, the content of this type of compound, when present, is between 1 and 4% by weight of the fluid. The fracturing fluid can of course comprise other elements commonly used in the field, such as antifoam or scale inhibitors.

These fluids are obtained by simple mixing of the various elements which constitute them in the desired proportions. The invention likewise relates to the use of the aqueous fluid as a drilling fluid, in the field of the exploitation of oil or gas deposits.

In addition to the boronate polymer, the ligand polymer and a soluble salt, the drilling fluids may include thinning or dispersing agents.

Thus, can enter into the composition of drilling fluids, polyphosphates, tannins, lignosulfonates, lignin derivatives, peat and lignites, polyacrylates, polynaphthalene sulfonates, alone or as a mixture.

The amount of fluidizing or dispersing agent is variable. As an indication, this is between 0 and 1% relative to the weight of the fluid.

The drilling fluid may further comprise at least one filtrate reducer, which are compounds adsorbed on the rocks constituting the walls of the well, thereby limiting the diffusion through the walls of the drilling of the various constituent elements of the fluid. By way of examples of compounds of this type, there may be mentioned without intending to be limited thereto, cellulose compounds, polyacrylamides, high molecular weight polyacrylates, succinoglycans, native starch or its derivatives, carbon. Among the cellulose compounds, unmodified or chemically modified celluloses such as carboxymethylcelluloses, hydroxyethylcelluloses and carboxyethyl-hydroxyethylcelluloses are compounds which are suitable as a filtrate reducer. Of course, nothing prevents the use of these products in combination if the conditions make it necessary.

The quantity of filtrate reducer strongly depends on the nature of the rocks crossed. However, as an indication, this is usually between 0 and 1% relative to the total weight of the fluid

The drilling fluid according to the invention can comprise an oxygen sensor. The purpose of this type of additive is to trap the oxygen present in drilling muds and which can cause degradation of certain additives.

Among the products of this type, mention may be made, for example, of hydroxylamines, hydrazine, sulfites, bisulfites, hydrosulfites. Preferably, hydrazine is used, which can be in an anhydrous or hydrated form, in the form of salts such as, for example, chloride, sulphate, or also in the form of carbohydrazide.

Generally the content of additive of this type varies between 0 and 0.25% by weight of the fluid. The drilling fluid may further comprise at least one weighting compound and / or at least one mineral colloid. The weighting elements help maintain sufficient hydrostatic pressure in the well and keep the entrained rocks in suspension during the drilling operation. Such compounds are conventionally chosen from the above-mentioned soluble salts and the sparingly or very sparingly soluble salts. Among the sparingly soluble salts, there may be mentioned without intending to be limited thereto, the sulfates, silicates or carbonates of alkaline earth metals, such as barium sulfate, calcium carbonate. It is likewise possible to use bromides of alkaline earth metals or of zinc such as potassium bromide, zinc bromide. It is also possible to use oxides or sulphide or as iron arsenate. It is also possible to use strontium sulphate, or even in certain cases of high density of Galena (lead sulphide).

Mineral colloids, which are compounds that are substantially insoluble under the conditions of use of the fluid according to the invention, are agents modifying the rheology of the medium and making it possible to keep the cuttings in suspension in the latter. Attapulgite, baryte, bentonite, alone or as a mixture, are the most commonly used examples. It should be noted that if a fluid comprising a mineral colloid is used, the latter will preferably be attapulgite. The contents of weights and mineral colloids depend on several factors which are not only technical. In fact, if these contents are obviously fixed according to the nature of the soils crossed, the importance of the cost generated by the use of these additives is taken into account (presence on site or not, cost, etc.). Mineral salts can also be added to the drilling fluid, if necessary, to promote the precipitation of certain ions, if they are present, and in particular divalent ions. Mention may be made, for example, of the addition of sodium carbonate to precipitate calcium, or baking soda to precipitate lime, in particular during reforings in cement. Mention may also be made of the addition of gypsum or calcium chloride to limit the swelling of clays, the addition of calcium hydroxide, or slaked lime, to debicarbonate sludges contaminated with carbon dioxide.

The salt content depends on the rocks crossed and the water available on the operating site and operations can be carried out in the presence of fluids saturated with salts.

Obviously, the drilling fluid according to the present invention can comprise usual additives from the class of high molecular weight polysaccharides, such as succinoglycan, wellan, gellan, useful as viscosants.

Other conventional additives for applications relating to the exploitation of petroleum deposits may enter into the composition of the fluid (drilling fluid or stimulation fluid, such as a fracturing fluid). Thus, we can mention free radical transfer agents, such as lower alcohols, thioureas, hydroquinone; biocides, chelating agents, surfactants, anti-foaming agents, anti-corrosion agents for example.

Finally, it is mentioned that the aqueous fluid according to the invention can be used as a fluid for the evacuation of excavation products, in particular in the sectors of construction in deep areas, the construction of tunnels or wells, or in the mining sector. In these applications, the excavation products are suspended in the fluid, by introducing the fluid into the area from which they must be eliminated. Document US 5,439,317 in examples of excavation applications.

Other details or advantages of the invention will become apparent from the example which follows, without being limiting.

Example 1: Preparation of a boronate block copolymer comprising one mole of boronate functions per polymer chain: "p (St) -b-p (AA) with boronate"

First stage:

380 g of water, 2.92 of sodium dodecyl sulphate and 0.15 g of carbonate are introduced at ambient temperature with stirring into a two-liter double-jacketed glass reactor fitted with mechanical stirring and maintained under an inert atmosphere. sodium.

The medium is then placed at 85 ° C.

At this temperature, 4.23 g of O-ethyl-S- (1-methoxycarbonyl) ethyl) xanthate [(CH ₃ CHCO ₂ CH ₃ ) S (C = S) OEt], 6 g of styrene and 0.1 g methacrylic acid are added to the middle. After 5 minutes of homogenization, a solution of 0.93 g of ammonium persulfate in 12.35 g of water is added. Then a mixture of 54 g of styrene and 0.89 g of methacrylic acid is introduced for one hour. The reaction medium is maintained at this temperature for one hour after the end of the introduction. A sample is then taken and analyzed by steric exclusion chromatography (CES). Its number-average molar mass Mn is equal to 3300 g / mol (calibration by linear polystyrene standards).

Its polymolecularity index Mw / Mn is equal to 2.39.

Mw represents the average molar mass by weight of the polymer. The reaction is continued by introducing a solution of 0.46 g of ammonium persulfate in 10 g of water, then adding a mixture of 345 g of ethyl acrylate and 6.91 g of methacrylic acid for 2:45. At this time, a solution of 37.6 g of ethyl acrylate and 3 g of 4-vinylphenyl boronic acid is introduced for 15 minutes. In parallel with the introduction of the monomers, a solution of 0.46 g of sodium carbonate in 125 g of water is introduced for 3 hours. After two hours of introduction of the reagents, a solution of 0.46 g of ammonium persulfate in 10 g of water is introduced.

The reaction is maintained for three hours after the end of the introduction of the reactants.

A sample is then taken and analyzed by steric exclusion chromatography (C.E.S.). Its average molar mass in number Mn is equal to 23900 g / mol (calibration by linear polystyrene standards).

Its polymolecularity index Mw / Mn is equal to 3.55.

Analysis of the sample by gas chromatography reveals that the conversion of the monomers is greater than 99%. In particular, the concentration of residual 4-vinylphenyl boronic acid is less than 5 ppm (measured by HPLC - high performance liquid chromatography).

Second step :

At the end of the synthesis described in the first step, 426 g of the copolymer emulsion is maintained at 85 ° C. 335 g of water are then added. The temperature is then lowered to 75 ° C. and a mixture of 498 g of water and 109 g of isopropanol is added to the latex. 211 g of sodium hydroxide solution

7.25 N are then introduced over a period of two hours. The hydrolysis is maintained for two hours after the end of the introduction of soda.

At the end of hydrolysis, a highly viscous aqueous gel is obtained. A 1 H NMR analysis of the copolymer resulting from the hydrolysis reveals that the sodium hydroxide has been completely consumed, creating sodium acrylate sites on the polymer chain.

Example 2 Fluid comprising the copolymer of Example 1

An aqueous fluid is prepared comprising: - 1% by weight of the copolymer of Example 1

- 0.36% by weight of depolymerized native guar with a molar mass of approximately 2 million g / mol

- sea water.

Claims

1. Aqueous fluid used in the exploitation of oil or gas deposits comprising: - at least one boronate polymer comprising at least one boronate or precursor function,

- At least one ligand polymer having at least two groups capable of reacting with the boronate or precursor functions; said groups being in the cis position and carried by vicinal atoms or by two atoms separated by an additional atom,

- At least one salt soluble in the fluid, present at a content of at least 0.01% by weight relative to the weight of fluid and less than the limit of solubility of the salt or salts in said fluid.

2. Fluid according to the preceding claim, characterized in that the boronate polymer is such that the number of moles of boronate or precursor functions per polymer chain, p, is at least 1, more particularly at least 3, of preferably at least 5.

3. Fluid according to one of the preceding claims, characterized in that the boronate polymer is such that p is less than the average degree of polymerization, DPn, more particularly less than or equal to 0.5DPn, preferably less than or equal to 0, 1 DPn.

4. Fluid according to one of the preceding claims, characterized in that the boronate polymer is such that the average degree of polymerization is at least 10, more particularly at least 20, preferably at least 50 and is less than or equal to 106.

5. Fluid according to one of the preceding claims, characterized in that the boronate polymer is a block polymer.

6. Fluid according to one of the preceding claims, characterized in that the boronate polymer is a polymer comprising at least one block of hydrophobic nature optionally having at least one hydrophilic unit, and at least one hydrophilic block having at least one hydrophobic unit.

7. Fluid according to the preceding claim, characterized in that the block of hydrophobic nature comprises less than 70% by weight of hydrophilic units relative to the weight of the units present in said block, preferably from 1 to 50% by weight.

8. Fluid according to one of claims 6 or 7, characterized in that the block of hydrophilic nature comprises 1 to 33% by weight of hydrophobic units relative to the weight of the units present in said block, preferably from 2 to 15% in weight.

9. Fluid according to one of the preceding claims, characterized in that the mass ratio of the hydrophilic blocks and the hydrophobic blocks is between 95/5 and 20/80.

10. Fluid according to one of claims 1 to 4, characterized in that the boronate polymer is a random polymer or having a concentration gradient.

11. Fluid according to one of the preceding claims, characterized in that the ligand polymer comprises at least one or more sets of at least two hydroxyl groups, originating from alcohol and / or carboxylic acid functions, one or more sets of at at least one hydroxyl group, originating from alcohol and / or carboxylic acid functions, associated with at least one amino group, preferably primary or secondary, or alternatively the combination of these two possibilities.

12. Fluid according to one of the preceding claims, characterized in that the ligand polymer is a polymer chosen from galactomannans, glucomannans, and their derivatives, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, copolymers comprising (meth) glyceryl acrylate.

13. Fluid according to one of the preceding claims, characterized in that the content of boronate polymer is between 0.001 and 1% by weight of the fluid, preferably between 0.01 and 0.5% by weight of the fluid.

14. Fluid according to one of the preceding claims, characterized in that the content of ligand polymer is less than or equal to 5% by weight of the fluid, preferably between 0.1 and 5% by weight of the fluid.

15. Fluid according to one of the preceding claims, characterized in that the soluble salts are chosen from alkali or alkaline-earth metal chlorides, iodides, sulfates, carbonates, bicarbonates, phosphates, silicates, of alkali metals, alone or as a mixture.

16. Fluid according to one of the preceding claims, characterized in that it comprises at least one gas such as air, nitrogen, or carbon dioxide.

17. Use of the fluid according to one of the preceding claims, as a fluid for stimulating the exploitation of oil or gas deposits.

18. Use according to claim 17 as a fracturing fluid.

19. Use according to claim 17, characterized in that the fluid is a fracturing fluid with liquid carbon dioxide.

20. Use according to claim 17 as a drilling fluid.

21. Use according to claim 18 or 19, at a temperature between 120 ° C and 150 ° C.