RU2783126C2 - Polymer systems for particle dispersion - Google Patents

Abstract

FIELD: oil production.

SUBSTANCE: present invention relates to the field of oil production, where, when injecting working fluids under pressure into underground reservoirs, it is necessary to retain particles in a suspension for prevention of their precipitation during a long period of time regardless extreme temperature-baric conditions. The invention relates to a group of inventions: a concentrate of well treatment liquid, a method for hydraulic fracture of an underground reservoir, a method for gravel filling, a method for drilling of a wellbore, a system for cementation of a wellbore, a method for cementation of an oil well, and a method for treatment of an underground well. This concentrate of well treatment liquid contains: water-soluble polymer; at least one substance selected from a surfactant and/or a mutual solvent, in amount of 10-57 % by wt.; a hydrophobic solvent, a value of hydrophilic-lipophilic balance (HLB) of which is 0-6; and either 0.2-3 % by wt. or 0.2-10 % by wt. of a suspending reagent. Water-soluble polymer contains: at least one hydrophobic monomer selected from a group consisting of n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide, myristyl methacrylate, myristyl methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof; and at least one hydrophilic monomer selected from a group consisting of acrylate, acrylate salts, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, salts of 2-acrylamido-2-methylpropansulfonic acid, and combinations thereof. This concentrate is a non-settling suspension.

EFFECT: development of polymer systems for dispersion of particles capable of being subjected to fast hydration and used for maintenance of particle dispersions during a long period of time.

20 cl, 2 dwg, 11 tbl, 6 ex

Description

[0001] This patent application claims priority under 35 U.S.C. § 119(e) based on U.S. Provisional Application No. 62/608020, filed December 20, 2017, the full disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] There are many areas in which keeping particles in suspension is critical (eg, pigment particles in paint or varnish type compositions). More specifically, in the field of oil production, multiple steps are carried out by injecting working fluids under pressure into subterranean formations, in which it is often useful to keep particles in suspension to prevent their settling, despite the extreme pressure and temperature conditions commonly experienced in a subterranean formation.

[0003] In order to suppress the process of separation by deposition, additives can be included that allow you to keep the particles in suspension. A number of such additives have been described, including, in particular, crosslinked or non-crosslinked polymers, polysaccharides and their derivatives, such as xanthan gum, cellulose ethers, or alternatively guar gums and their derivatives, crosslinked with borate or zirconate. However, it turns out that these suspending reagents (reagents for maintaining the solid phase in suspension) decompose when the temperature exceeds 150°C. Accordingly, such limitation renders the listed additives unsuitable for higher temperature applications (typically above 150°C, often 150 to 200°C, in fact even in the range up to over 200°C). In addition, in the case of the use of these polymeric reagents near oil-bearing formations, namely, in particular, in such working fluids as drilling fluid for formation opening, well completion fluid, fracturing fluid, acidizing fluid or buffer fluids, these agents have the disadvantage of decomposing in the form of insoluble residues which cannot be properly removed.

[0004] Another disadvantage is that the hydration of polymers in oilfield applications is generally a slow process. Such a process typically involves at least several minutes of mixing the polymer, either hydrocarbon slurry or dry polymer, with water in a fluid path containing various compartments. Although the hydration process and time have been reduced in recent decades due to numerous efforts, they are still not as fast as we would like, that is, they provide more than 80% of the final fluid viscosity in less than 1 or 1.5 minutes. Long hydration times require that such an operation be carried out in a dedicated hydration unit, such as a continuous precision mixer (PCM), in addition to a mixing unit, such as a programmable optimum density (POD) mixer. The equipment and energy costs of such a process are high. Although numerous continuous mixing systems are currently used in the oilfield, none of them is completely satisfactory, and there remains a significant need for systems with improved hydration properties.

BRIEF DESCRIPTION OF GRAPHICS

[0005] FIG. 1 is a plot of viscosity versus time and temperature for slurry formulation 1-1.

[0006] FIG. 2 is a plot of viscosity versus time and temperature for a 2-1 slurry formulation.

BRIEF DESCRIPTION OF THE INVENTION

[0007] The present invention provides polymer systems that are capable of undergoing rapid hydration and that can be used to maintain particle dispersions over an extended period of time. Such polymer systems can also be used to maintain particle dispersions for extended periods of time at elevated temperatures and/or high brine conditions.

DETAILED DESCRIPTION OF THE INVENTION

[0008] The present inventors have discovered polymeric particle dispersion systems that unexpectedly have improved hydration properties while providing improved particle dispersion capability. In one embodiment, the suspension time of particles of an aqueous composition comprising water and a polymer of the present invention is at least 1 hour. In another embodiment, the particle suspension time is at least 2 hours. In another embodiment, the particle suspension time is at least 4 hours. In another embodiment, the particle suspension time is 24 hours. In one embodiment, the aqueous composition suspends the particles at a temperature of from about 68°F (20°C) to about 350°F (about 177°C) (or any temperature within that range).

[0009] In one embodiment, the polymer system is a well treatment fluid concentrate comprising a water-soluble polymer containing at least one hydrophobic monomer selected from n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide , myristil methacrylate, myristil methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof, and

[0010] at least one hydrophilic monomer selected from acrylate, acrylate salts, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof;

[0011] at least one substance selected from a surfactant, a mutual solvent, or a combination thereof, wherein the total amount of the surfactant and/or mutual solvent in the concentrate is from 30% wt. up to 57% wt.; or from 30% wt. up to 50% wt.; or from 10% wt. up to 50% wt.; from 10% wt. up to 57% wt. based on the total weight of the concentrate;

[0012] a hydrophobic solvent whose hydrophilic-lipophilic balance (HLB) value is from 0 to 6; and from about 0.2% of the mass. up to about 3% wt. or from about 0.2% of the mass. up to about 10% wt. suspending reagent based on the total weight of the concentrate, while the specified concentrate is a non-settling suspension.

[0013] In one embodiment, the surfactant is selected from alkylbenzenesulfonates, alkyl betaines, alkylamidopropyl betaines, and combinations thereof.

[0014] In one embodiment, the mutual solvent is selected from the group of compounds of Formula I:

[0015] where each R ₁ , R ₂ and R ₃ independently represents a linear or branched C ₁ -C ₈ alkyl group; compounds of formula II:

[0016] where each R ₁ , R ₂ , R ₃ and R ₄ independently represents a linear or branched C ₁ -C ₈ alkyl group; ethoxylated and/or propoxylated linear or branched alcohols; and their combinations.

[0017] In one embodiment, the hydrophobic solvent having an HLB value of 0 to 6 is selected from toluene, xylene, ethylbenzenes, aromatic naphthas, produced hydrocarbons, diesel fuel, kerosene, paraffin oil, mineral oil, and combinations thereof.

[0018] In one embodiment, the suspending agent is selected from organophilic bentonite, hectorite, smectite, montmorillonite, attapulgite, kaolinite, and any combination thereof.

[0019] As used herein, the term "non-settling suspension" refers to homogeneous aqueous suspensions that do not settle within 24 hours.

[0020] According to one embodiment, the proposed concentrate additionally contains water in an amount of from about 0.01% of the mass. up to about 5% wt. based on the total weight of the concentrate.

[0021] In one embodiment, the polymer systems are used in subterranean formations. In the present description, the term "subterranean formation" is used in the broadest sense and includes both rock containing hydrocarbons, in particular oil, and various layers of rock that are intersected to gain access to such oil-bearing rock and allow production of hydrocarbons. As used herein, rock is used to refer to any type of constituent material of a solid subterranean formation, whether or not such formation constituent material is, strictly speaking, rock. Thus, in particular, the expression "oil rock" is used herein as a synonym for "oil reservoir" and refers to any subterranean formation containing hydrocarbons, in particular oil, regardless of the nature of the material containing such hydrocarbons (rock or sand, for example).

[0022] Among the well treatment fluids injected under pressure into subterranean formations, mention may be made, in particular, of various completion and workover fluids, in particular drilling fluids, whether or not they are used to gain access to oil bearing rock. or for drilling the reservoir itself (“break-in”), or fracturing fluids, or alternatively completion fluids, well control fluids or workover fluids, or annulus fluids, or parquet fluids, or buffer fluids acidizing fluids or fluids, or also cementing fluids.

[0023] In one embodiment, the polymer comprises at least one hydrophobic monomer selected from n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide, myristyl methacrylate, myristyl methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof; and at least one hydrophilic monomer selected from acrylate, acrylate salts, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof. In one embodiment, the hydrophilic monomers include acrylamide and 2-acrylamido-2-methylpropane sulfonic acid.

[0024] According to one embodiment, the polymer includes hydrophilic monomers in a total amount of from about 50% of the mass. up to about 99.9% of the mass. relative to the weight of the polymer. According to another implementation variant, the polymer includes hydrophilic monomers in a total amount of from about 80% of the mass. up to about 99.9% of the mass. relative to the weight of the polymer. According to another implementation variant, the polymer includes hydrophobic monomers in a total amount of from about 0.01% of the mass. up to about 50% wt. relative to the weight of the polymer. According to another implementation variant, the polymer includes hydrophobic monomers in a total amount of from about 0.01% of the mass. up to about 20% wt. relative to the weight of the polymer.

[0025] In one embodiment, the polymer has a thiocarbonylthio functional group at its end position.

[0026] In one embodiment, the polymer is in a non-settling slurry, wherein the particle size of the polymer powder in the slurry is from about 5 microns to about 400 microns.

[0027] In another embodiment, the polymer powder comprises polymer particles having a size of from about 5 microns to about 400 microns and a molecular weight of from about 10,000 to about 20,000,000 g/mol, said polymer comprising acrylamide and 2-acrylamido-2- methylpropane sulfonic acid and at least one hydrophobic monomer selected from n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide, myristyl methacrylate, myristyl methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof. In one embodiment, the hydrophobic monomer is selected from lauryl methacrylate, lauryl methacrylamide, and combinations thereof.

[0028] In one embodiment, the polymers of the present invention are prepared by micellar polymerization. The polymer system includes block copolymers (P) containing at least one chain (C) of the type obtained by micellar polymerization, to keep solid particles (p) in suspension in the working fluid (F), in which the specified chain (C) is soluble.

[0029] More specifically, according to a certain aspect, the subject of the present invention is the use of the above-mentioned block copolymers as a suspending agent in a working fluid (F) injected under pressure into a subterranean formation, while said working fluid (F) contains at least a part solid particles (p) and/or brought into contact with at least a portion of the solid particles (p) in the underground formation after its injection.

[0030] As used herein, the term “chain soluble in working fluid (F)” means a chain (C) whose solubility in working fluid (F) at 20° C. is typically greater than or equal to 0.5% (5000 ppm), preferably greater than or equal to 1%.

[0031] Micellar polymerization schematically consists in carrying out the polymerization of hydrophilic monomers in a hydrophilic medium containing micelles containing hydrophobic monomers. Examples of micellar polymerization have been described, in particular, in US patent No. 4432881 or else in Polymer , Vol. 36, No.16, pp. 3197-3211 (1996), which documents can be referenced for more information.

[0032] The chain (C) of the polymers (P) used according to the present invention is a chain that is generally soluble in the working fluid (F) and which is predominantly composed of a number of hydrophilic units interrupted at various points by many hydrophobic sequences (B) essentially the same size. The polymer according to the present invention may consist of a chain (C) or may be a block copolymer in which the specified chain (C) is one of the blocks.

[0033] The hydrophobic sequences (B) are preferably polymer sequences insoluble in the working fluid (F), whose solubility at 20° C. in the working fluid (F) is typically less than or equal to 0.1% (1000 ppm).

[0034] Copolymers (P) containing the chain (C) mentioned above are suitable for holding solid particles (p) in suspension. They may be particles present in the subterranean formation and/or particles injected into the subterranean formation, usually together with copolymers (such as, for example, proppant particles).

[0035] According to the present invention, micellar polymerization can generally be used in cases where the following substances are copolymerized (usually by a radical method) in an aqueous dispersion medium (usually water or a water/alcohol mixture): hydrophilic monomers in a dissolved or dispersed state in specified environment; and hydrophobic monomers in micelles of a surfactant formed in said medium by incorporating such a surfactant at a concentration greater than its critical micelle concentration (cmc).

[0036] The content of hydrophobic monomers, corresponding to the ratio of the mass of hydrophobic monomers to the total mass of hydrophobic and hydrophilic monomers, preferably greater than or equal to 0.01%, preferably greater than 0.1%, in fact even greater than 0.2%, and less than or equal to 5 %. In general, the percentage of hydrophobic units in chain (C) is of the same order, usually greater than or equal to 0.05%, preferably greater than 0.1%, in fact even greater than 0.2% and less than or equal to 5%.

[0037] It is believed that in micellar polymerization, the hydrophobic monomers present in the micelles are in the "micellar solution". Said micellar solution is a microheterogeneous system which is generally isotropic, optically transparent and thermodynamically stable.

[0038] It should be noted that a micellar solution of the type used in micellar polymerization should be distinguished from a microemulsion. In particular, unlike a microemulsion, a micellar solution is formed at any concentration above the critical micelle concentration of the surfactant used, the only condition being that the hydrophobic monomer is soluble at least to some extent in the interior of the micelles. In addition, a micellar solution differs from an emulsion in the absence of a homogeneous internal phase: micelles contain a very small number of molecules (usually less than 1000, in general less than 500 and usually from 1 to 100, most often from 1 to 50 monomers, and at most several hundred molecules of surfactant when surfactant is present), the micellar solution generally having physical properties similar to those of non-monomer surfactant micelles. In addition, in general, the micellar solution is transparent to visible light, given the small size of the micelles, which does not lead to refractive phenomena, unlike emulsion droplets, which refract light and give it a characteristic cloudy or white appearance.

[0039] The micellar polymerization process results in characteristic block copolymers that all contain multiple hydrophobic blocks of substantially the same size, which size can be controlled. In particular, given the retention of hydrophobic monomers within micelles, each of the hydrophobic blocks contains essentially the same specific number n _H of hydrophobic monomers, which number can be calculated as follows (Macromolecular Chem. Physics, 202). 8, 1384-1397, 2001):

n _H = N _agg . [M _H ]/( [SAW] - cmc)

where:

N _agg is the surfactant aggregation number, which reflects the amount of surfactant present in each micelle;

[M _H ] is the molar concentration of the hydrophobic monomer in the medium;

[surfactant] is the molar concentration of the surfactant in the medium; and

cmc is the critical concentration (molar) of micellization.

[0040] Thus, the micellar polymerization method makes it possible to effectively control the amount of hydrophobic units introduced into the resulting polymers, namely: overall control of the mole fraction of hydrophobic units in the polymer (by adjusting the concentration ratio of the two monomers); and more specific regulation of the amount of hydrophobic units present in each of the hydrophobic blocks (by changing the parameters affecting n _H defined above).

[0041] The chain (C), generally soluble in the working fluid (F), which is obtained by micellar polymerization, contains:

a hydrophilic component consisting of hydrophilic monomers corresponding to a hydrophilic polymer chain having a solubility typically greater than or equal to 1% (10,000 ppm) at 20°C when added alone to the working fluid (F),

hydrophobic component consisting of hydrophobic sequences, each of which has a solubility in the working fluid (F) at 20°C, usually less than or equal to 0.1% (1000 ppm).

[0042] In many cases, the chain (C) can be described as a hydrophilic chain having the above solubility (at least 1%), to which side hydrophobic groups are grafted. In particular, in this case, the chain (C) has a total solubility at 20°C in the working fluid (F), which preferably remains greater than or equal to 0.1%, in fact even 0.5%.

[0043] According to a particular embodiment, chain (C) is of the type obtained by a method comprising a micellar radical polymerization step (e) in which the following substances are brought into contact in an aqueous medium (M):

hydrophilic monomers dissolved or dispersed in said aqueous medium (M) (usually water or water/alcohol mixtures);

hydrophobic monomers in the form of a micellar solution, namely a solution containing in a dispersed state in the medium (M) micelles containing these hydrophobic monomers (in particular, it is possible to provide such a dispersed state when using at least one surfactant); and

at least one radical polymerization initiator, said initiator typically being water-soluble or water-dispersible.

[0044] According to a preferred embodiment, chain (C) is of the type obtained by a method comprising a micellar radical polymerization step (E) in which the following substances are brought into contact in an aqueous medium (M):

hydrophilic monomers dissolved or dispersed in said aqueous medium (M) (usually water or water/alcohol mixtures);

hydrophobic monomers in the form of a micellar solution, namely a solution containing in a dispersed state in the medium (M) micelles containing these hydrophobic monomers (in particular, it is possible to provide such a dispersed state when using at least one surfactant);

at least one radical polymerization initiator, said initiator typically being water-soluble or water-dispersible; and

at least one agent that regulates radical polymerization.

[0045] Stage (E) is similar to stage (e) described above, but it uses an additional regulating agent. This step, known as "controllable nature micellar radical polymerization", has been described in particular in WO 2013/060741. All alternative forms described herein can be used in the present invention.

[0046] In the understanding of the present description, the term "radical polymerization control agent" means a compound capable of increasing the lifetime of growing polymer chains in a polymerization reaction and imparting a "living" or controlled character to polymerization. Such a control agent is typically a reversible chain transfer agent used in controlled radical polymerization processes termed RAFT (Reversible Chain Transfer Polymerization) or MADIX (Xanthate Exchange Macromolecular Design), which typically use a reversible attachment and fragmentation polymerization process. , such as processes described, for example, in WO 96/30421, WO 98/01478, WO 99/35178, WO 98/58974, WO 00/75207, WO 01/42312, WO 99/35177, WO 99/31144, FR 2 794 464 or WO 02/26836.

[0047] In one embodiment, the radical polymerization control agent used in step (E) is a compound containing a thiocarbonylthio -S(C=S)- group. Thus, for example, said agent may be a compound containing a xanthate group (containing -SC=S-O- functional groups), such as xanthate. Other types of control agents may be contemplated (eg, of the type used in CRP (Controlled Radical Polymerization) or ATRP (Atom Transfer Radical Polymerization)).

[0048] According to a specific embodiment, the control agent used in step (E) may be a polymer chain resulting from controlled radical polymerization and containing a group capable of controlling radical polymerization (the well-known "living" type polymer chain). Thus, for example, the control agent may be a polymeric chain (preferably hydrophilic or water-dispersible) functionalized at the end of the chain with a xanthate group or, more generally, containing a -SC=S- group, for example, obtained in accordance with MADIX technology.

[0049] Alternatively, the control agent used in step (E) is a non-polymeric compound containing a radical polymerization control group, in particular a thiocarbonylthio-S(C=S)- group.

[0050] According to a specific alternative form, the radical polymerization control agent used in step (E) is a polymer, preferably an oligomer, water-soluble or dispersible in water and containing a thiocarbonylthio -S(C=S)- group, e.g. xanthate -SC =SO-group. Further, in the present specification, such a polymer capable of acting both as a polymerization control agent and as a monomer in step (E) is also referred to as a "prepolymer". Typically, said prepolymer is obtained by radical polymerization of hydrophilic monomers in the presence of a control agent containing a thiocarbonylthio -S(C=S)- group, such as xanthate. Thus, for example, according to the preferred embodiment illustrated at the end of this description, the control agent used in step (E) may advantageously be a prepolymer containing a thiocarbonylthio -S(C=S)- group, e.g. xanthate -SC=SO - the group obtained at the completion of stage (E ⁰ ) controlled radical polymerization before stage (E). In this stage (E ⁰ ), as a rule, it is possible to bring into contact hydrophilic monomers, mostly identical to the monomers used in stage (E); a radical polymerization initiator; and a control agent containing a thiocarbonylthio-S(C=S)-group, such as xanthate.

[0051] The use of the above step (E ⁰ ) to step (E) allows, schematically, to hydrophilize a large number of control agents containing thiocarbonylthio functional groups (for example, xanthates, which are quite hydrophobic in nature), by converting them from prepolymers, soluble or dispersible in medium (M) in step (E). The prepolymer synthesized in step (E ⁰ ) preferably has a short polymer chain, eg containing a sequence of less than 50 monomer units, in fact even less than 25 monomer units, eg 2 to 15 monomer units.

[0052] When using step (E), the polymers of the present invention contain chains (C) having a "controlled" structure, namely, all chains (C) present in the polymers are essentially the same size and the same structure. Chains (C) contain, in particular, blocks (B) in essentially the same number and proportion

[0053] As it turns out, the specific polymers (P) used in the context of the present invention, due to the presence of hydrophobic sequences in the hydrophilic polymer chain, provide a regulatory effect on the working fluid, which is particularly effective: not wishing to be bound by theory, it seems that the hydrophobic units in the hydrophilic chains and/or in different hydrophilic chains tend to associate with each other.

[0054] According to one embodiment, the injected working fluid (F) includes polymers (P) but does not contain solid particles (p), while it collides with the specified particles (p) in the subterranean formation after it is injected. Association then occurs between the particles and polymers under reservoir conditions. Such a working fluid can, for example, be pumped during a drilling operation, and then, in formation conditions, the rock fragments formed during drilling play the role of particles (p).

[0055] According to an alternative embodiment, the injected working fluid (F) contains at least a part and, as a rule, all of the particles (p) associated with the polymer (P) before injection, it should be understood that the specified fluid may not necessarily collide in the underground reservoir and with other particles (p).

[0056] In this context, in particular, two forms can be envisaged:

[0057] Form 1: polymers (P) and particles (p) are mixed during the preparation of the working fluid (F) directly at the operation site or upstream, usually by adding particles (p) in a dry state or optionally dispersed condition to a composition containing polymers (P) in solution.

[0058] Form 2: the working fluid (F) is obtained mainly directly at the operation site from a composition (pre-mixed) prepared upstream (hereinafter referred to as "mixture") containing polymers (P) and at least part of the particles (p), usually in a dispersing liquid. To obtain a working fluid (F) such a mixture is mixed with other components of the working fluid (F).

[0059] In some embodiments, the polymers (P) associated with the particles (p) can be used as a dispersing and stabilizing agent to disperse the particles (p) while providing an agent to control the absorption of the working fluid.

[0060] As used herein, "fluid loss control" refers to suppression of the "fluid loss" effect observed when a pressurized working fluid is injected into a subterranean formation: the liquid phase present in the working fluid tends to seep into the constituent rock of the subterranean formation. formation, which can damage the well and, in fact, even violate its integrity. When such hydraulic fluids applied under pressure contain insoluble compounds (which is very often the case, in particular in the case of oil-cement slurries or drilling fluids or hydraulic fracturing fluids), the effect of absorption of the hydraulic fluid at the same time provokes risks of loss of control over the injected working fluids. and an increase in the concentration of insoluble compounds in the working fluid, which can lead to an increase in viscosity, which affects the mobility of the working fluid.

[0061] In particular, when the hydraulic fluid (F) is a fracturing fluid, a cementing fluid, or a drilling fluid, the presence of copolymers (P) allows control of fluid loss by limiting, in fact even completely suppressing, leakage of the fluid ( F), usually water or an aqueous composition, into a subterranean formation in which mining takes place.

[0062] Various specific advantages and embodiments of the present invention will now be described in more detail.

[0063] WORKING FLUID (F). In the understanding of the present description, the term "working fluid" means any homogeneous or heterogeneous medium containing a liquid or viscous vector, which optionally carries a liquid or thickened dispersed phase and/or solid particles, while the specified medium is completely amenable to pumping using devices for pumping under pressure applied in the application in question.

[0064] The term "liquid or viscous vector" of the working fluid (F) means the working fluid itself or the solvent in the case when the specified working fluid contains dissolved compounds and / or a continuous phase, in the case when the specified working fluid contains dispersed elements ( drops of liquid or thickened dispersed phase, solid particles, etc.).

[0065] In a very suitable embodiment, the working fluid (F) is an aqueous fluid. As used herein, the term "aqueous" means that said working fluid contains water as a liquid or viscous vector, either as the sole component of a liquid or viscous vector, or in combination with other water-soluble solvents.

[0066] In case solvents other than water are present in the liquid or viscous working fluid vector (F), water predominantly remains the predominant solvent in the liquid or viscous vector, predominantly present in a proportion of at least 50% by weight, in fact even at least 75% by weight, based on the total weight of the solvents in the liquid or viscous vector.

[0067] In one embodiment, the working fluid (F) is selected from fresh water, sea water, brines, salt water, produced water, recycled water, industrial waste water, oil production waste water, and combinations thereof.

[0068] PARTICLES (p). The concept of "particle" in the sense in which it is used in the present description, is not limited to the concept of individual particles. In a more general sense, it denotes solid components that can be dispersed in the working fluid in the form of objects (individual particles, aggregates, etc.), for which all dimensions are less than 5 mm, preferably less than 2 mm, for example, less than 1 mm .

[0069] Particles (p) according to the present invention can be selected from: calcium carbonate or cement, silica or sand, ceramics, clay, barite, hematite, carbon black and/or mixtures thereof.

[0070] According to a specific embodiment of the present invention, the particles (p) are particles of sand or cement.

[0071] POLYMERS (P).

[0072] Hydrophilic monomers. Typically, chain (C) may contain monomers selected from:

[0073] carboxylic acids, which are ethylenically unsaturated sulfonic acids and phosphonic acids and/or derivatives thereof, such as acrylic acid (AA), methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, fumaric acid, monoesters of monoethylenically unsaturated dicarboxylic acids containing 1 to 3 and preferably 1 to 2 carbon atoms, e.g. monomethyl maleate, vinyl sulfonic acid, meta-allylsulfonic acid, sulfoethyl acrylate , sulfoethyl methacrylate, sulfopropylacrylate, sulfopropyl methacrylate, 1-allyloxy-2-hydroxypropylsulfonate, 2-hydroxy-3-acryloyl-oxypropyl-sulfonic acid, 2-hydroxy-3-methacryloyl-oxypropyl-sulfonic acid, styrenesulfonic acids, 2-acrylamido-2- methylpropanesulfonic acid, vinylphosphonic acid, α-methylvinylphosphonic acid and allylphosphonic acid;

[0074] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with C ₂ -C ₃ alkanediols, e.g. -hydroxypropyl methacrylate and polyalkylene glycol methacrylates;

[0075] amides of α,β-ethylenically unsaturated monocarboxylic acids and their N-alkyl and N,N-dialkyl derivatives, such as acrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-isopropylmethacrylamide, N,N-dimethylmethacrylamide, N, N-diethylmethacrylamide, morpholinylmethacrylamide and methylolacrylamide (acrylamide and N,N-dimethylmethacrylamide proved to be particularly preferred);

[0076] N-vinyl lactams and their derivatives, for example, N-vinylpyrrolidone or N-vinylpiperidone;

[0077] Open chain N-vinylamide compounds, for example, N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide, N -vinyl-N-methylpropionamide and N-vinylbutyramide;

[0078] esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with amino alcohols, for example, N,N-dimethylaminomethyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl acrylate, and N,N-dimethylaminopropyl methacrylate;

[0079] amides of α,β-ethylenically unsaturated mono- and dicarboxylic acids with diamines containing at least one primary or secondary amino group, such as N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(dimethylamino)ethyl ]methacrylamide, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N-[4-(dimethylamino)butyl]acrylamide and N-[4-(dimethylamino)butyl]methacrylamide ;

[0080] N-diallylamines, N,N-diallyl-N-alkylamines, their acid addition salts and their quaternization products, wherein the alkyl used in the present invention is preferably C ₁ -C ₃ alkyl;

[0081] N,N-diallyl-N-methylamine and N,N-diallyl-N,N-dimethylammonium compounds, eg chlorides and bromides;

[0082] nitrogen-containing heterocycles substituted with vinyl and allyl, for example,

N-vinylimidazole, N-vinyl-2-methylimidazole, heteroaromatic compounds substituted with vinyl and allyl, for example 2- and 4-vinylpyridine, 2- and 4-allylpyridine and their salts;

[0083] sulfobetaines; and

[0084] salts of the monomers listed above;

[0085] mixtures and combinations of two or more monomers and/or their salts listed above.

[0086] According to a specific implementation variant of the listed monomers may, in particular, include acrylic acid (AA).

[0087] In yet another embodiment, the hydrophilic monomers in chain (C) comprise (and typically consist of) methacrylamide monomers, or more generally methacrylamido monomers, including:

[0088] acrylamide monomers, namely acrylamide (Am), dimethylacrylamide (DMA), their sulfonate derivative, in particular acrylamide-methylpropane-sulfonic acids (AMPS);

[0089] Quaternary ammonium compound APTAC ((3-acrylamidopropyl)trimethylammonium chloride) and sulfopropyl-dimethylammonio-propylacrylamide;

[0090] Methacrylamido monomers such as sulfopropyl-dimethylammonio-propylmethacrylamide (SPP) or sulfohydroxy-propyldimethylammonio-propylmethacrylamide.

[0091] In a particular embodiment, the hydrophilic monomers in chain (C) are acrylamides. The acrylamide is preferably a non-copper stabilized acrylamide.

[0092] In a particular embodiment, the hydrophilic monomers in chain (C) are selected from acrylamides, dimethylacrylamides (DMA), acrylamide methyl propane sulfonic acids (AMPS), acrylic acids (AA), salts thereof, and mixtures thereof.

[0093] In a specific embodiment, the hydrophilic monomers in chain (C) can generally have a polymerizable acrylamide-type functional group and a side chain consisting of ethylene oxide or propylene oxide chains, or based on N-isopropylacrylamide or N-vinylcaprolactam.

[0094] Hydrophobic monomers. As non-limiting examples of a hydrophobic monomer forming insoluble blocks that can be used according to the present invention, there may be mentioned in particular:

[0095] vinylaromatic monomers such as styrene, α-methylstyrene, para-chloromethylstyrene, vinyltoluene, 2-methylstyrene, 4-methylstyrene, 2-(n-butyl)styrene, 4-(n-decyl)styrene, or tert-butylstyrene;

[0096] halogenated vinyl compounds such as vinyl or vinylidene halides, for example vinyl or vinylidene chlorides or fluorides, corresponding to the formula R _b R _c C=CX ¹ X ² ,

where: X ¹ = F or Cl

X ² \u003d H, F or Cl

each group of R _b and R _c is independently:

- H, Cl, F; or

- an alkyl group, preferably chlorinated and/or fluorinated, more preferably perchlorinated or perfluorinated;

[0097] Esters of α,β-ethylenically unsaturated mono- or dicarboxylic acid with C ₂ -C ₃₀ alkanols, e.g. -butyl ethacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, 1,1,3,3-tetramethylbutyl methacrylate, ethylhexyl methacrylate, n-nonyl methacrylate, n-decyl methacrylate, n-undecyl methacrylate, tridecyl methacrylate, myristyl methacrylate, pentadecyl methacrylate, palmityl methacrylate heptadecyl methacrylate, nonadecyl methacrylate, arachidyl methacrylate, behenyl methacrylate, lignoceryl methacrylate, cerotinyl methacrylate, melissinyl methacrylate, palmitoleoyl methacrylate, oleyl methacrylate, linoleyl methacrylate, linoleyl methacrylate, stearyl methacrylate, lauryl methacrylate, cetyl methacrylate, erucyl methacrylate, and mixtures thereof;

[0098] esters of vinyl or allyl alcohol with C ₁ -C ₃₀ monocarboxylic acids, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate, and mixtures thereof;

[0099] ethylenically unsaturated nitriles such as acrylonitrile, methacrylonitrile, and mixtures thereof;

[00100] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with C ₃ -C ₃₀ alkanediols, e.g. -hydroxy-2-ethylhexyl acrylate and 3-hydroxy-2-ethylhexyl methacrylate and the like;

[00101] Primary amides of α,β-ethylenically unsaturated mono- and dicarboxylic acids and N-alkyl and N,N-dialkyl derivatives such as N-propylmethacrylamide, N-(n-butyl)methacrylamide, N-(t-butyl)methacrylamide , N-butylphenylacrylamide, N-methyl-N-hexylacrylamide, N,N-dihexylacrylamide, hexylmethacrylamide, N-(n-octyl)methacrylamide, N-(1,1,3,3-tetramethylbutyl)methacrylamide, N-ethylhexylmethacrylamide, N -(n-nonyl)methacrylamide, N-(n-decyl)methacrylamide, N-(n-undecyl)methacrylamide, N-tridecylmethacrylamide, N-myristyl methacrylamide, N-pentadecyl methacrylamide, N-palmityl methacrylamide, N-heptadecyl methacrylamide, N-nonadecyl methacrylamide, N-arachidyl methacrylamide, N-behenyl methacrylamide, N-lignoceryl methacrylamide, N-cerotinyl methacrylamide, N-melissinyl methacrylamide, N-palmitoleoyl methacrylamide, N-oleyl methacrylamide, N-linoleyl methacrylamide, N-linoleyl methacrylamide, N-stearyl methacrylamide and N-lauryl methacrylamide;

[00102] N-vinyl lactams and their derivatives such as N-vinyl-5-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone, N- vinyl-7-methyl-2-caprolactam and N-vinyl-7-ethyl-2-caprolactam and the like;

[00103] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with amino alcohols, eg N,N-dimethylamino-cyclohexyl methacrylate;

[00104] Amides of α,β-ethylenically unsaturated mono- and dicarboxylic acids with diamines containing at least one primary or secondary amino group, e.g. N-[4-(dimethylamino)butyl]acrylamide, N-[4-(dimethylamino)butyl ]methacrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[4-(dimethylamino)cyclohexyl]acrylamide, N-[4-(dimethylamino)cyclohexyl]methacrylamide and the like; and

[00105] monoolefins (C ₂ -C ₈ ) and non-aromatic hydrocarbons containing at least two conjugated double bonds, for example, ethylene, propylene, isobutylene, isoprene, butadiene, and the like.

[00106] In a preferred embodiment, the hydrophobic monomers used in the present invention may be selected from:

[00107] C ₁ -C ₃₀ alkyl and preferably C ₄ -C ₂₂ alkyl α,β-unsaturated esters, in particular alkyl acrylates and methacrylates, such as methyl-, ethyl-, butyl-, 2-ethylhexyl-, isooctyl- , lauryl, isodecyl, stearyl, octyl, myristyl, pentadecyl, cetyl, oleyl or erucyl acrylates and methacrylates (lauryl methacrylate has proven particularly preferred in particular);

[00108] C ₁ -C ₃₀ alkyl and preferably C ₄ -C ₂₂ alkyl α,β-unsaturated amides, in particular alkylacrylamides and alkylmethacrylamides such as methyl-, ethyl-, butyl-, 2-ethylhexyl-, isooctyl-, lauryl, isodecyl, stearyl, octylmyristyl, pentadecyl, cetyl, oleyl or erucyl acrylamide or methacrylamide (lauryl methacrylamide has proven to be especially preferred in particular);

[00109] esters of vinyl or allyl alcohols and saturated carboxylic acids such as vinyl or allyl acetate, propionate, versatate, or stearate;

[00110] α,β-unsaturated nitriles containing from 3 to 12 carbon atoms, such as acrylonitrile or methacrylonitrile; α-olefins and conjugated dienes; vinylaromatic monomers such as styrene, α-methylstyrene, p-chloromethylstyrene, vinyltoluene, 2-methylstyrene, 4-methylstyrene, 2-(n-butyl)styrene, 4-(n-decyl)styrene or tert-butylstyrene; mixtures and combinations of two or more of the monomers listed above.

[00111] In a preferred embodiment, particularly when the hydraulic fluid (F) is a fracturing fluid, hydrophobic monomers that are weakly bonded to chain (C) can be used. This allows, if necessary, to remove polymers introduced into the subterranean formation (due to their amphiphilic nature, the polymers of the present invention generally exhibit a tendency to self-associate and usually form gels that are difficult to remove; in particular, when subjected to temperature and/or pH, it is possible the breakdown of hydrophobic monomers, unless they are too strongly bound to the polymer, making it possible to remove them from the working fluid). Suitable hydrophobic monomers for this embodiment are, in particular, the esters listed above.

[00112] It should be noted that when other monomers are used, removal from working fluids is still possible using a well-known method in which "thinners" such as oxidizers are added. The previous embodiment makes it possible to dispense with the use of such "thinners", which is reflected, in particular, in a reduction in cost. According to one embodiment of the present invention, the diluent is selected from peroxides, persulfates, peracids, bromates, chlorates, chlorites, and combinations thereof.

[00113] According to a specific embodiment, the molecular weight of the polymer may be from about 10,000 g/mol to about 20,000,000 g/mol. In another embodiment, the molecular weight of the polymer is from about 100,000 g/mol to about 10,000,000 g/mol. In another embodiment, the molecular weight of the polymer is from about 500,000 g/mol to about 50,000,000 g/mol.

[00114] RADICAL POLYMERIZATION AGENT. The control agent used in step (E) or, optionally, step (E ⁰ ) of the method according to the present invention is advantageously a compound containing a thiocarbonylthio -S(C=S)- group. In a particular embodiment, the control agent may contain multiple thiocarbonylthio groups. Optionally, it may be a polymer chain containing such a group.

[00115] Thus, such a control agent may, for example, correspond to formula (A) below:

[00116]

in which Z represents: a hydrogen atom, a chlorine atom, an optionally substituted alkyl or optionally substituted aryl radical, an optionally substituted heterocycle, an optionally substituted alkylthio radical, an optionally substituted arylthio radical, an optionally substituted alkoxy radical, an optionally substituted aryloxy radical, optionally substituted amino radical, optionally substituted hydrazine radical, optionally substituted alkoxycarbonyl radical, optionally substituted aryloxycarbonyl radical, optionally substituted acyloxy or carboxyl radical, optionally substituted aroyloxy radical, optionally substituted carbamoyl radical, cyano radical, dialkyl or diarylphosphonato radical, dialkyl phosphinato or diaryl phosphinato radical or polymer chain, and R ₁ is an optionally substituted alkyl, acyl, aryl, aralkyl, alkenyl or alkynyl group, saturated or unsaturated, aromatic, optional an optionally substituted carbocycle or heterocycle, or a polymer chain which is preferably hydrophilic or water-dispersible when said agent is used in step (E).

[00117] The R ₁ or Z groups, when substituted, may be substituted with optionally substituted phenyl groups, optionally substituted aromatic groups, saturated or unsaturated carbocycles, saturated or unsaturated heterocycles, or groups selected from the following list: alkoxycarbonyl or aryloxycarbonyl (-COOR ), carboxyl (-COOH), acyloxy (-O2CR), carbamoyl (-CONR ₂ ), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (-OH) , amino (-NR ₂ ), halogen, perfluoroalkyl C _n F _2n+1 , allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl, hydrophilic or ionic groups such as alkali metal salts and carboxylic acids, alkali metal salts and sulfonic acids, polyalkylene oxide (PEO, PPO) chains, cationic substituents (quaternary ammonium salts), wherein R represents an alkyl or aryl group or a polymer chain.

[00118] For the control agents of formula (A) used in step (E), it is generally preferred that the R ₁ group be of a hydrophilic nature. Such a group is preferably a water-soluble or water-dispersible polymer chain.

[00119] Alternatively, the R ₁ group may be amphiphilic, that is, exhibit both a hydrophilic and a lipophilic nature. Preferably R ₁ is not hydrophobic.

[00120] With respect to the control agents of formula (A) used in step (E ⁰ ), R ₁ can generally be a substituted or unsubstituted, preferably substituted, alkyl group. The control agent of formula (A) used in step (E ⁰ ) may, however, contain other types of R ₁ groups, such as a ring or a polymer chain.

[00121] Optionally substituted alkyl, acyl, aryl, aralkyl, or alkynyl groups typically contain 1 to 20 carbon atoms, preferably 1 to 12, and more preferably 1 to 9 carbon atoms. They can be linear or branched. They may also be substituted with oxygen atoms, in particular in the form of esters, sulfur atoms or nitrogen atoms.

[00122] Among the alkyl radicals, in particular, methyl, ethyl, propyl, butyl, pentyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, decyl or dodecyl radicals can be mentioned.

[00123] Alkyne groups are radicals typically containing 2 to 10 carbon atoms; they contain at least one acetylenic unsaturation, such as an acetylenyl radical.

[00124] An acyl group is a radical typically containing 1 to 20 carbon atoms with a carbonyl group.

[00125] Among the aryl radicals, in particular, mention may be made of a phenyl radical which optionally contains a substituent, in particular a nitro or hydroxyl functional group.

[00126] Among the aralkyl radicals, in particular, mention may be made of a benzyl or phenethyl radical which optionally contains a substituent, in particular a nitro or hydroxyl functional group.

[00127] When R ₁ or Z is a polymer chain, such a polymer chain may be formed by radical or ionic polymerization or by polycondensation.

[00128] Preferably, as a control agent for step (E), as well as for step (E ⁰ ), use, if necessary, compounds containing xanthate -S(C=S)O-, trithiocarbonate, dithiocarbamate or dithiocarbazate functional group, for example, containing an O-ethyl-xanthate functional group of the formula -S(C=S)OCH ₂ CH ₃ .

[00129] When carrying out step (E ⁰ ), it is particularly preferred to use a compound selected from xanthates, trithiocarbonates, dithiocarbamates and dithiocarbazates as control agents in this step. Xanthates have proven to be particularly effective, in particular those containing the O-ethyl-xanthate -S(C=S)OCH ₂ CH ₃ functional group, such as O-ethyl-S-(1-(methoxycarbonyl)ethyl) xanthate (CH ₃ CH(CO ₂ CH ₃ ))S(C=S)OEt. Another possible control agent in step (E ⁰ ) is dibenzyl trithiocarbonate of the formula PhCH ₂ S(C=S)SCH ₂ Ph (where Ph = phenyl).

[00130] Living prepolymers obtained in step (E ⁰ ) by using the control agents listed above have proven to be particularly preferred in step (E).

[00131] Initiating and conducting radical polymerization in steps (E) and (E ⁰ ). When a radical polymerization initiator is used in step (E), such initiator is preferably water-soluble or water-dispersible. Apart from such a preferred condition, any radical polymerization initiator (source of free radicals) well known and corresponding to the conditions selected for said steps can be used in step (E) and step (E ⁰ ) of the process according to the present invention.

[00132] Thus, the radical polymerization initiator used according to the present invention can, for example, be selected from initiators commonly used in radical polymerization. Such an initiator may be, for example, one of the following initiators:

[00133] hydrogen peroxides such as: tert-butyl hydroperoxide, cumene hydroperoxide, tert-butylperoxyacetate, tert-butylperoxybenzoate, tert-butylperoxyoctoate, tert-butylperoxyneodecanoate, tert-butylperoxyisobutyrate, lauroyl peroxide, tert-amyl peroxypivalate, tert-butylperoxypivalate, dicumyl peroxide, potassium persulfate or ammonium persulfate,

[00134] azo compounds such as: 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-butanenitrile), 4,4'-azobis(4-pentanoic acid), 1,1'-azobis( cyclohexanecarbonitrile), 2-(tert-butylazo)-2-cyanopropane, 2,2'-azobis[2-methyl-N-(1,1)-bis(hydroxymethyl)-2-hydroxyethyl]propionamide, 2,2'- azobis(2-methyl-N-hydroxyethyl]propionamide, 2,2'-azobis(N,N'-dimethyleneisobutyramidine) dichloride, 2,2'-azobis(2-amidinopropane) dichloride, 2,2'-azobis(N, N'-dimethyleneisobutyramide), 2,2'-azobis(2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide), 2,2'-azobis(2-methyl-N-[ 1,1-bis(hydroxymethyl)ethyl]propionamide), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] or 2,2'-azobis(isobutyramide) dihydrate,

[00135] redox systems containing combinations such as:

[00136] mixtures of hydrogen peroxide, alkyl peroxide, peresters, percarbonates, and the like. and any iron salt, titanium salt, zinc formaldehyde sulfoxylate or sodium formaldehyde sulfoxylate and reducing sugars,

[00137] alkali metal or ammonium persulfates, perborates or perchlorates in combination with an alkali metal bisulfite such as sodium metabisulfite and reducing sugars, and

[00138] Alkali metal persulfates in combination with arylphosphinic acid such as benzenephosphonic acid and the like and reducing sugars.

[00139] As a rule, the amount of initiator used is preferably determined so that the amount of radicals formed is at most 50 mol. % and preferably at most 20 mol. % relative to the amount of control agent or chain transfer agent.

[00140] Particularly in step (E), it is generally advantageous to use a radical redox type initiator, having, inter alia, the advantage that heating of the reaction medium is not required (no thermal initiation), and, in addition, the authors of the present invention have now found that such an initiator is suitable for micellar polymerization in stage (E).

[00141] Thus, the radical polymerization initiator used in step (E) can typically be a redox initiator, typically requiring no heat to thermally initiate it. Typically, it is a mixture of at least one oxidizing agent with at least one reducing agent.

[00142] The oxidizing agent present in such a redox system is preferably a water soluble agent. Said oxidizing agent can be selected, for example, from peroxides such as: hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, t-butylperoxyacetate, t-butylperoxybenzoate, t-butylperoxyoctoate, t-butylperoxyneodecanoate, t-butylperoxyisobutyrate, lauroyl peroxide, t-amylperoxypivalate, t -butyl peroxy pivalate, dicumyl peroxide, benzoyl peroxide, sodium persulfate, potassium persulfate, ammonium persulfate or also potassium bromate.

[00143] The reducing agent present in the redox system is also preferably a water soluble agent. Such a reducing agent can generally be selected from sodium formaldehyde sulfoxylate (particularly in its dihydrate form known as Rongalit or anhydride form), ascorbic acid, erythorbic acid, sulfites, bisulfites or metasulfites (in particular alkali metal sulfites, bisulfites or metasulfites) , nitrilotrispropionamides and tertiary amines and ethanolamines (which are preferably water soluble).

[00144] Possible redox systems include combinations such as:

[00145] mixtures of water-soluble persulfates with water-soluble tertiary amines,

[00146] mixtures of water-soluble bromates (for example, alkali metal bromates) with water-soluble sulfites (for example, alkali metal sulfites),

[00147] mixtures of hydrogen peroxide, alkyl peroxide, peresters, percarbonates, and the like. and any iron salt, titanium salt, zinc formaldehyde sulfoxylate or sodium formaldehyde sulfoxylate and reducing sugars,

[00148] alkali metal or ammonium persulfates, perborates or perchlorates in combination with an alkali metal bisulfite such as sodium metabisulfite and reducing sugars, and

[00149] Alkali metal persulfates in combination with arylphosphinic acid such as benzenephosphonic acid and the like and reducing sugars.

[00150] A preferred redox system includes (and preferably consists of) a combination of ammonium persulfate and sodium formaldehyde sulfoxylate.

[00151] In general, and in particular when using a redox system of the ammonium persulfate/sodium formaldehyde sulfoxylate type, it is preferred that the reaction medium in step (E) be free of copper. When copper is present, it is generally desirable to add a copper complexing agent, such as EDTA, in an amount capable of masking its presence.

[00152] Regardless of the nature of the initiator used, the radical polymerization in the (E ⁰ ) step can be carried out in any suitable physical form, e.g., in solution in water or in a solvent, e.g., alcohol or THF, in an emulsion in water ("latex" process) or more, if necessary, by adjusting the temperature and/or pH to bring the components into a liquid and/or soluble or insoluble state.

[00153] After step (E), taking into account the specific use of the control agent, polymers functionalized with transfer groups (living polymers) are obtained. This "living" nature allows, if desired, to use these polymers in the subsequent polymerization reaction in accordance with a well-known method. Alternatively, if necessary, transfer groups can be deactivated or destroyed, for example by hydrolysis, ozonolysis or reaction with amines, in accordance with well known methods. Thus, in a specific embodiment, the process of the present invention may include, after step (E), a step (E1) of hydrolysis, ozonolysis, or reaction with amines capable of deactivating and/or destroying all or part of the transfer groups present in the resulting polymer. in step (E).

[00154] Surfactants. To obtain a micellar solution of hydrophobic monomers used in stage (E), you can use any suitable surfactant in a non-limiting manner; for example, surfactants selected from the following list may be used:

[00155] Anionic surfactants can be selected from:

[00156] alkyl ester sulfonates, e.g., formula R-CH(SO ₃ M)-CH ₂ COOR', or alkyl ester sulfates, e.g., formula CH(OSO ₃ M)-CH ₂ COOR', where R is A C ₈ -C ₂₀ and preferably a C ₁₀ -C ₁₆ alkyl radical, R' is a C ₁ -C ₆ and preferably a C ₁ -C ₃ alkyl radical, and M is an alkali metal cation, for example a sodium cation or an ammonium cation. Mention may especially be made of methyl ester sulfonates whose R radical is a C ₁₄ -C ₁₆ radical;

[00157] alkylbenzenesulfonates, more specifically C ₉ -C ₂₀ alkylbenzenesulfonates, primary or secondary alkylsulfonates, in particular C ₈ -C ₂₂ alkylsulfonates or alkylglycerol sulfonates;

[00158] alkyl sulfates, for example of the formula ROSO ₃ M, where R is a C ₁₀ -C ₂₄ and preferably a C ₁₂ -C ₂₀ alkyl or hydroxyalkyl radical and M is a cation as defined above;

[00159] alkyl ether sulfates, e.g. of the formula RO(OA) _n SO ₃ M, where R is a C ₁₀ -C ₂₄ and preferably a C ₁₂ -C ₂₀ alkyl or hydroxyalkyl radical, OA is an ethoxylated and/or propoxylated group , M is a cation as defined above, and n generally ranges from 1 to 4, such as, for example, lauryl ether sulfate with n = 2;

[00160] alkylamide sulfates, for example of the formula RCONHR'OSO ₃ M, where R is a C ₂ -C ₂₂ and preferably a C ₆ -C ₂₀ alkyl radical, R' is a C ₂ -C ₃ alkyl radical and M is a cation defined above, as well as their polyalkoxylated (ethoxylated and/or propoxylated) derivatives (alkylamide ether sulfates);

[00161] salts of saturated or unsaturated fatty acids, such as, for example, C ₈ -C ₂₄ and preferably C ₁₄ -C ₂₀ acids, and alkaline earth metal cation, N-acyl-N-alkyl taurates, alkyl isethionates, alkyl succinamates and alkyl sulfosuccinates, alkyl glutamates, complex monoesters or diesters of sulfosuccinates, N-acylsarcosinates or polyethoxycarboxylates;

[00162] phosphate monoesters and diesters, for example, having the following formula: (RO) _x -P(=O)(OM) _x , where R is optionally a polyalkoxylated alkyl, alkylaryl, arylalkyl, or aryl radical, x and x' are equal to 1 or 2, provided that the sum of x and x' is 3 and M is an alkaline earth metal cation;

[00163] Nonionic surfactants can be selected from:

[00164] alkoxylated fatty alcohols, e.g. laureth-2, laureth-4, laureth-7 or oleta-20, alkoxylated triglycerides, alkoxylated fatty acids, alkoxylated sorbitan esters, alkoxylated fatty amines, alkoxylated di(1-phenylethyl)phenols,

alkoxylated tri(1-phenylethyl)phenols, alkoxylated alkylphenols, products obtained by condensing ethylene oxide with a hydrophobic compound obtained by condensing propylene oxide with propylene glycol, such as Pluronic products supplied by BASF, products obtained by condensing ethylene oxide with a compound, obtained by the condensation of propylene oxide with ethylenediamine, such as the Tetronic products supplied by BASF, alkyl polyglycosides, such as those described in US Pat. No. _4,565,647 , or alkyl _glycosides or fatty acid amides, for example , fatty acid monoalkanolamides, for example cocamide MEA (monoethanolamine) or cocamide MIPA (monoisopropanolamine);

[00165] Amphoteric surfactants (true amphoteric compounds containing an ionic group and possibly an ionic group with an opposite charge, or zwitterionic compounds containing two opposite charges at the same time) can be:

[00166] betaines, typically in particular carboxybetaines, for example lauryl betaine (Mirataine BB from Rhodia) or octyl betaine or cocobetaine (Mirataine BB-FLA from Rhodia); amidoalkyl betaines such as cocamidopropyl betaine (CAPB) (Mirataine BDJ from Rhodia or Mirataine BET C-30 from Rhodia);

[00167] sulfobetaines or sultaines such as cocamidopropyl hydroxysultaine (Mirataine CBS from Rhodia);

[00168] alkylamphoacetates and alkylamphodiacetates, such as, for example, containing a cocoyl or lauryl chain (Miranol C2M Conc. NP, C32, L32, in particular from Rhodia);

[00169] alkylamphopropionates or alkylamphodipropionates (Miranol C2M SF);

[00170] alkylamphohydroxypropyl sultaines (Miranol CS);

[00171] alkylamine oxides, for example lauramine oxide (INCI);

[00172] Cationic surfactants may optionally be polyethoxylated primary, secondary or tertiary fatty amine salts, quaternary ammonium salts such as tetraalkylammonium, alkylamidoalkylammonium, trialkylbenzylammonium, trialkylhydroxyalkylammonium or alkylpyridinium chlorides or bromides, imidazoline derivatives, or amine oxides having a cationic nature . An example of a cationic surfactant is cetrimonium chloride or bromide (International Cosmetic Ingredient Nomenclature, INCI);

[00173] The surfactants used according to the present invention may be block copolymers containing at least one hydrophilic block and at least one hydrophobic block other than the hydrophilic block, which are obtained mainly according to the method of polymerization, in which:

[00174] (a ₀ ) at least one hydrophilic (respectively hydrophobic) monomer, at least one source of free radicals and at least one agent of the type -S(C=S)-, which regulates radical polymerization, are combined in the aqueous phase;

[00175] (a ₁ ) the polymer obtained at the completion of step (a ₀ ) is contacted with at least one hydrophobic (respectively hydrophilic) monomer other than the monomer used in step (a ₀ ), and at least with one source of free radicals; whereby a diblock copolymer is obtained.

[00176] Polymers of the triblock type or containing more blocks can optionally be obtained by carrying out, after step (a ₁ ), step (a ₂ ), in which the polymer obtained after the completion of step (a ₁ ) is brought into contact with at least one monomer other than the monomer used in step (a ₁ ) and at least one source of free radicals; and, more generally, by carrying out (n + 1) steps such as steps (a ₁ ) and (a ₂ ) described above, where n is an integer, typically in the range 1 to 3, with each step (a _n ), when n≥ 1, the polymer obtained at the end of step (a _n-1 ) is brought into contact with at least one monomer other than the monomer used in step (a _n-1 ), and at least at least one source of free radicals. According to the present invention, for example, certain types of copolymers can be used, which are described in WO03068827, WO03068848 and WO2005/021612.

[00177] In one embodiment, one or more polymers of the present invention are present in the aqueous composition. According to another implementation variant of one or more polymers proposed in the present invention, are present in the aqueous composition in an amount of from about 0.001% of the mass. up to about 10% wt. based on the total weight of the aqueous composition.

[00178] The present invention also provides methods of using the proposed polymers and corresponding compositions.

[00179] In one embodiment, a method for fracturing a subterranean formation includes the step of injecting a water-based fracturing fluid into at least a portion of the subterranean formation at pressures sufficient to fracture the formation, said fracturing fluid comprising a concentrate as provided herein. invention.

[00180] In one embodiment, prior to injection of the water-based fracturing fluid, the polymer is in the form of a powder with a particle size of about 5 microns to about 400 microns. According to one embodiment, the polymer is present in an amount of from about 0.001 wt. up to about 10% wt. based on the total weight of the fracturing fluid.

[00181] In one embodiment, the fracturing fluid suspends the particles at a temperature of about 68°F (20°C) to about 350°F (about 177°C). In another embodiment, the fracturing fluid suspends the particles at a temperature of from about 250°F (about 121°C) to about 350°F (about 177°C). In another embodiment, the fracturing fluid suspends the particles at a temperature of from about 300°F (about 149°C) to about 350°F (about 177°C).

[00182] In one embodiment, the fracturing fluid further comprises a proppant. According to one embodiment, the proppant is used in an amount of about 20% by weight. up to about 60% wt. based on the total weight of the fracturing fluid.

[00183] In one embodiment, the fracturing fluid further comprises a clay stabilizer. In one embodiment, the clay stabilizer is selected from choline chloride, potassium chloride, ammonium chloride, sodium chloride, calcium chloride, and combinations thereof. In one embodiment, the clay stabilizer is present in an amount of about 0.01 wt. up to about 30% wt. based on the total weight of the fracturing fluid.

[00184] In another embodiment, the fracturing fluid further comprises a friction reducing polymer. In one embodiment, the friction reducing polymer is selected from synthetic polymers, natural polymers, semi-synthetic polymers, and mixtures thereof. The natural and semi-synthetic polymer can be selected from xanthan gum, guar gum, modified guar gum such as cationic guar gum or hydroxypropyl guar gum, scleroglucan, schizophyllan, cellulose derivatives such as carboxymethyl cellulose, and mixtures thereof. In one embodiment, said polymer is a synthetic anionic or cationic or nonionic or amphoteric polymer based on nonionic monomers and/or cationic monomers and/or anionic monomers.

[00185] In one embodiment, the proposed method for fracturing a subterranean formation includes an initial step of pumping a proppant-depleted fracturing fluid into the formation to initiate formation and propagation of a fracture in the subterranean formation, followed by a series of steps of injecting a proppant-rich fracturing fluid into the formation, at In this case, the initial stage of pumping a proppant-depleted fracturing fluid into the formation includes the use of a water-based hydraulic fluid system containing a polymer selected from synthetic polymers, natural polymers, semi-synthetic polymers and mixtures thereof, and the stages of pumping a proppant-rich fracturing fluid into the formation include the use of a composition according to the present invention. The natural and semi-synthetic polymer can be selected from xanthan gum, guar gum, modified guar gum such as cationic guar gum or hydroxypropyl guar gum, scleroglucan, schizophyllan, cellulose derivatives such as carboxymethyl cellulose, and mixtures thereof. In one embodiment, said polymer is a synthetic anionic or cationic or nonionic or amphoteric polymer based on nonionic monomers and/or cationic monomers and/or anionic monomers.

[00186] In one embodiment, a method for fracturing a subterranean formation adjacent to a wellbore includes the steps of pumping an initial proppant-depleted water-based hydraulic fluid system containing a friction reducing polymer into at least a portion of a subterranean formation at a rate that causes pressure loss across friction, followed by pumping a proppant-rich water-based fluid system containing a friction-reducing polymer and a concentrate of the present invention into at least a portion of a subterranean formation, said proppant-lean water-based fluid system comprising a friction-reducing polymer , which is the same or different friction reducing polymer found in proppant-rich water-based fluid systems.

[00187] In one embodiment, the proposed method for fracturing a subterranean formation further comprises the step of pumping a breaker into at least a portion of the subterranean formation. According to one embodiment of the present invention, the breaker includes an enzymatic breaker. In one embodiment, the enzymatic breaker is selected from oxidoreductase, oxidase, ligase, asparaginase, and mixtures thereof.

[00188] In one embodiment, the fracturing fluid is selected from fresh water, sea water, brines, salt water, produced water, recycled water, industrial waste water, oil production waste water, and combinations thereof.

[00189] According to another embodiment, a fracturing fluid is provided comprising a polymer at a mass concentration of from about 0.1 ppt (parts per trillion) to about 200 ppt based on the total volume of the composition, a plurality of proppant particles at a mass concentration of from about 0, 1 lb/gal (about 11.98 kg/m ³ ) to about 12 lb/gal (about 1438 kg/m ³ ) based on the total volume of the composition, and a thinner present in a mass concentration of 0 ppt to about 20 ppt per calculated on the total volume of the composition.

[00190] Also provided is a method for acidifying a formation intersected by a wellbore, comprising the steps of injecting into the wellbore at a pressure below the fracturing pressure of a well treatment fluid comprising a concentrate of the present invention and an aqueous acid solution, and allowing the well treatment fluid to acidify the formation and /or perform self-diverting in the formation. As used herein, the term "self-diverting" refers to a composition that thickens when the formation is stimulated and thereby diverts any remaining acid to lower permeability zones in the formation.

[00191] In one embodiment, a method for acidifying a subterranean formation intersected by a wellbore comprises the steps of: (a) injecting into the wellbore at a pressure below the fracturing pressure of the subterranean formation a well treatment fluid having a first viscosity and comprising an aqueous acid solution and a concentrate according to the present invention; (b) forming at least one void space in the subterranean formation with the well treatment fluid; and (c) causing the well treatment fluid to achieve a second viscosity greater than the first viscosity.

[00192] In one embodiment, the proposed method further comprises generating at least one void in the subterranean formation with the well treatment fluid after said fluid has reached a second viscosity.

[00193] In another embodiment, the proposed method further comprises reducing the viscosity of the well treatment fluid to a viscosity that is less than the second viscosity.

[00194] Optionally, the well treatment fluid further comprises one or more additives. In one embodiment, said fluid contains one or more additives selected from corrosion inhibitors, iron control agents, clay stabilizers, calcium sulfate scale inhibitors, scale inhibitors, mutual solvents, non-emulsifiers, anti-blocking agents, biocides, wax inhibitors, indicators and their combinations. In one embodiment, the corrosion inhibitor is selected from alcohols (eg, acetylene hydrocarbons); cationic compounds (eg quaternary ammonium salts, imidazolines and alkyl pyridines); and non-ionic compounds (for example, alcohol ethoxylates). In one embodiment, such an additive is a dry additive. According to another implementation variant, one or more dry additives are mixed with the composition proposed in the present invention.

[00195] Suitable aqueous acid solutions include acids compatible with the polymers of the present invention for use in the acidification process. In one embodiment, the aqueous acid solution is selected from hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, sulfamic acid, and combinations thereof. In one embodiment, the well treatment fluid contains up to 30 wt % acid. relative to the total mass of the liquid.

[00196] In one embodiment, the compositions of the present invention are combined with a brine to thicken the liquid. In one embodiment, the brine is a high density (eg, density in the range of about 8.5 to about 21 pounds per gallon (about 1020 to about 2500 kg/ ^m3 )) solids-free salt composition ("heavy"), suitable for use in drilling, completion and stimulation of underground oil and gas wells. Working fluids used in the drilling, completion and stimulation of underground oil and gas wells include, but are not limited to, well completion fluids, perforating buffer fluids, water-based drilling fluids, reverse emulsion drilling fluid, gravel pack, drilling fluids for reservoir completions, parquet fluids, workover fluids, displacement fluids, fracturing fluids, and remedial fluids.

[00197] Compositions of the present invention can also be used to limit or prevent damage to a pump during surface transport of proppant. During surface transport, proppant (eg sand) can settle causing damage to the pump. Maintaining the flow of sand is essential for oil production in economic terms. In case of mechanical damage or clogging of the well or pump with sand, a major overhaul is required. The tubulars are retrieved and the well is thoroughly de-sanded prior to re-installation using a mechanical bailer, mobile pumping unit to transport sand to the surface, a jet pump, foam treatment, or other methods. Oil production is resumed after the pump is reinstalled.

[00198] According to one embodiment, a method for suspending and transporting proppant at a surface (e.g., above ground) includes the step of mixing water-based hydraulic fluid and proppant and transporting such a combination through at least one pump, said hydraulic fluid containing a concentrate according to the present invention.

[00199] The compositions of the present invention can also be used in drilling fluids or muds for drilling. Drilling mud or drilling mud is a specially formulated mud circulating through the drill bit in the wellbore during drilling of the wellbore. The drilling fluid is circulated back to the surface of the wellbore along with cuttings for removal from the well. The drilling fluid maintains a certain, equilibrium hydrostatic pressure in the wellbore, which allows all or most of the drilling fluid to circulate back to the surface. In addition, among other things, the drilling fluid facilitates cooling and lubrication of the drill bit, helps support the drill pipe and drill bit, and maintains the integrity of the borehole walls and prevents the well from flowing due to hydrostatic head. In one embodiment, a method for drilling a wellbore is provided, comprising the step of pumping a composition described herein into the wellbore.

[00200] The compositions of the present invention can also be used in gravel packing methods. Some oil and gas wells are filled with loose formations containing loose fine particles and sand. When producing fluids from such wells, loose fines and sand can migrate with the produced fluids and can damage equipment such as electric submersible pumps (ESPs) and other systems. For this reason, when completing such wells, sand screens may be required to control sand production. For hydrocarbon wells, especially horizontal wells, the completed well contains screen sections with a perforated inner tube and an overlying screen portion. The purpose of such a filter is to block the flow of solids into the interior of the production tubing string.

[00201] The gravel pack operation is one way to reduce the influx of solids before it reaches the sand screen. In gravel packing, gravel (eg sand) is used to pack the annulus around the sand screen. Gravel is a material in the form of particles of a certain size, such as graded sand or proppant. When placed around the sandscreen in the annulus, the gravel pack acts as a filter to prevent any fines and sand in the formation with produced fluids from migrating into the sandscreen. In addition, the gravel pack provides the reservoir with a stabilizing force that can prevent annulus failure. In general, gravel backfill is used to stabilize the formation and maintain well productivity. Gravel backfill is used in combination with hydraulic fracturing, but at much lower pressures.

[00202] In one embodiment, a gravel packing method includes the step of transporting a hydraulic fluid through at least one pump and a subterranean gravel pack, said hydraulic fluid carrying the gravel pack for placement in a wellbore and containing a concentrate of the present invention.

[00203] Compositions of the present invention may also be used in circulating fluids in drilling operations and/or to remove debris from a wellbore. The well, into which the circulating fluid is injected, traverses the underground reservoir. When drilling out, the barrier in the wellbore is first milled, which leaves behind waste such as rubber and metal. Alternatively, the waste in the wellbore may contain sand, residual fluids, nylon, carbon composites, etc. The site is cleaned with circulating water or brine and the composition of the present invention injected into such a zone.

[00204] Drilling out is typically performed with a coiled tubing unit (with a hydraulic downhole motor and milling/biting) or a composite pipe. Coiled tubing is more commonly used in horizontal wells. During drilling out, circulating fluid is introduced into the wellbore at the end of the pipeline or pipe and returned to the annulus. In one embodiment, the drilling out method includes the steps of milling a barrier in the wellbore, circulating a working fluid containing a composition of the present invention through the wellbore, and removing debris from the wellbore in the circulating fluid. In another embodiment, the wellbore is cleaned of debris by circulating a fluid containing a composition of the present invention through the wellbore and removing the debris from the wellbore in the circulating fluid.

[00205] The compositions of the present invention can be used in various stages of wellbore cementing operations. Wellbore preparation for cementing operations can be important in terms of providing optimal zonal isolation. Generally, wellbores can be cleaned and prepared for injection of the cement composition by a fluid line preceding the cement composition, which may contain buffer fluids, drilling fluids, water-based drilling fluids, and the like. Buffer fluids can be used to prepare the wellbore to displace the drilling fluid prior to the introduction of the cement composition. Buffer fluids can improve solids removal efficiency while separating the drilling fluid from a physically incompatible fluid such as a cement composition. In addition, buffer fluids can be placed between different drilling fluids during a drilling fluid change, or between a drilling fluid and a completion brine. According to one embodiment, a buffer fluid is provided that contains the composition described in the present invention. According to another implementation variant of the proposed system containing the composition described in the present invention, for use in a buffer fluid; a base fluid for use in a buffer fluid; and a pump fluid in fluid communication with a pipe in fluid communication with the wellbore, said pipe being configured to carry a buffer fluid into the wellbore. According to another implementation variant, a system is provided that includes a buffer fluid containing a composition described in the present invention, and a pump working fluid associated through a fluid connection with a pipe in fluid communication with the wellbore, while said pipe is configured to transfer the buffer fluid into the wellbore.

[00206] In another embodiment, the compositions of the present invention are used in flush fluids. In one embodiment, a method is provided, comprising the step of introducing a drilling fluid into a wellbore traversing at least a portion of a subterranean formation, said drilling fluid comprising a composition as described herein. Flushing fluids are used to dilute and disperse drilling fluid particles and to separate drilling and cementing fluids. Flushing fluids can be used with water or oil based drilling fluids. In one embodiment, both the pipe and the formation are prepared for the cementing operation using the drilling fluids.

[00207] Compositions of the present invention can also be used as cement suspending agents (eg, hydraulic cement). After drilling of the wellbore is completed, a string of tubing, such as casing, passes through the wellbore. Next, primary cementing is typically performed in which a cementing fluid, typically containing water, cement and particulate additives, is pumped through the tubing string into the annulus between the tubing string and the wellbore walls to cause the cementing fluid to set to form an impermeable cement string and, thereby sealing the annulus. It is also possible to carry out subsequent secondary cementing operations, ie any cementing operation after the primary cementing operation. One example of a secondary cementing operation is pressurized remedial cementing, in which a cementing fluid is injected under pressure into areas of lost integrity in the annulus to isolate such areas.

[00208] A common problem in oil well cementing is the leakage of filtrate from the cement slurry into porous low pressure zones in the subsurface surrounding the annulus. Such fluid loss is undesirable because it can dehydrate the cement slurry and cause thick cement solids filter cakes that can plug the wellbore; in addition, fluid loss can damage sensitive formations. The present invention provides a method comprising the steps of: suspending a cement composition with water, mixing the composition according to the present invention with the resulting slurry to obtain a cement slurry characterized by reduced fluid loss, and cementing a casing string in a wellbore by placing said cement slurry between the casing string and an open wellbore wall.

[00209] It is also possible to precipitate a solid phase in a cement slurry under various conditions. For example, settling can occur when cement is placed in a wellbore drilled at a high angle to the vertical axis. Precipitation is also possible when using suspensions with a high water content. Undesirable effects of solids settling include free water and a density gradient in the set cement. Cement suspending agents (to keep cement solids in suspension) can be added to the cementing fluid to suppress settling. In one embodiment, the present invention provides a method comprising the steps of: providing a cementing fluid comprising an aqueous solution, hydraulic cement, and a cement slurry agent comprising the composition described in the present invention; placing a cementing fluid in a wellbore traversing a subterranean formation; and causing the cementing fluid to set in said wellbore.

[00210] During well construction, operation, and well abandonment, it may be necessary to perform operations that require minimizing or stopping the flow of working fluid between the wellbore and the formation. In most cases, such operations are performed to restore, extend or increase hydrocarbon production. In order to maintain well control, workover operations require that the well be filled with a fluid with a hydrostatic pressure in excess of the formation pressure. This operation is usually referred to as "killing" the well. Killing a well can be accomplished in a variety of ways, including the introduction of drilling or completion fluids that exert sufficient hydrostatic pressure in the wellbore to prevent formation fluid production. Such fluid is often present in the wellbore throughout the workover period.

[00211] The compositions of the present invention are suitable for use in well killing operations. In one embodiment, a method is provided for treating a subterranean well containing a wellbore, comprising the steps of: (i) placing a well treatment fluid containing a composition described herein into the wellbore such that said well treatment fluid is in contact with with a liner, a well screen, perforations, natural or artificial fractures or a subterranean formation, or combinations thereof; and (ii) allowing the well treatment fluid to pass into the liner, well screen, perforations, natural or man-made fractures, or the subterranean formation, wherein after the well treatment fluid has passed, further fluid movement between the wellbore and the subterranean formation is prevented or restricted. In one embodiment, the well treatment fluid further comprises saturated brine and/or particles.

[00212] While specific embodiments are discussed, the present disclosure is illustrative only and not restrictive. Many variations of the present invention will become apparent to those skilled in the art upon review of the foregoing description.

[00213] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly used by a person skilled in the art to which this specification pertains.

[00214] In the present specification and claims, the singular form includes plural nouns unless the context clearly indicates otherwise.

[00215] As used herein, and unless otherwise indicated, the term "about" or "approximately" means the margin of error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the specified value is measured or determined. In some embodiments, the term "about" or "approximately" means within 1, 2, 3, or 4 standard deviations. In some embodiments, the term "about" or "approximately" means within 50%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% , 1%, 0.5%, or 0.05% of the set value or range.

[00216] In addition, it should be understood that any range of numerical values given in this document includes all related subranges. For example, the range "1 to 10" is meant to include all sub-ranges between the stated minimum value of 1 and the stated maximum value of 10, including the stated minimum and maximum values; that is, it contains a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Since the described ranges of numerical values are continuous, they include every value between the minimum and maximum values. Unless expressly stated otherwise, the various ranges of numerical values given in this application are approximate values.

[00217] The present invention will be further described with reference to the following examples. The following examples are merely illustrative and are not intended to be limiting.

[00218] Example 1 - Suspension containing diethylene glycol hexyl ether.

[00219] Slurry preparation procedure: Slurry was prepared using a Waring mixer. ODC oil (a high purity mixture of hydrotreated isoparaffins and naphthenes with a very low level of polynuclear aromatics) and diethylene glycol hexyl ether were placed in a beaker and then Bentone® 155 was added and mixed at 1500 rpm to disperse. Water was added as a clay activator and mixed for 5 minutes. The water soluble polymer powder was then added. The stirring speed was adjusted to maintain swirl until all of the polymer powder was mixed into the mixture. The final speed was about 2000 rpm. Before the study, the suspension was left to mix for another 20 minutes.

[00220] Table 1. Composition 1-1 of the suspension

Weight, g Oil ODC 15.6 Bentone® (Benton) 155 1.48 Diethylene glycol hexyl ether 42.5 Solvay Associated Water Soluble Polymer 41.4 Water 0.1

[00221] Hydration procedure: Eagle Ford water with 1K total dissolved solids (TDS) was used. 1.45 g of the suspension was added to 200 ml of 1K TDS water in a 500 ml Waring mixer over 3 minutes at 2500 rpm. To reduce the foam level, the liquid was centrifuged for 1 minute at 4000 rpm. Immediately thereafter, the viscosity was measured using an OFITE Model 900 viscometer available from OFI Testing Equipment, Inc. (Houston, Texas).

[00222] Table 2. Eagle Ford Water Composition

Water Eagle Ford pH: 8.93 Specific gravity (g/cm ³ ) 1.002 Sodium (ppm) 365 Calcium (ppm) ten Magnesium (ppm) 5 Barium (ppm) <25 Potassium (ppm) <10 Iron (ppm) 0 Chloride (ppm) 180 Sulfate (ppm) 85 Carbonate (ppm) 240 Bicarbonate (ppm) 122 TDS (ppm) 1007

[00223] Suspension stability test: The temperature of the suspension was adjusted to provide a temperature of 75°F (about 24°C) (+/- 3°F (+/- 3°C)). Prior to testing, a slurry sample from the mixer was stirred for 5 minutes. The suspension was poured into a graduated cylinder up to the 100 ml mark. The cylinder was covered, placed in an incubator at 75°F (about 24°C) (+/- 3°F (+/- 3°C)) and left intact for 24 hours. After 24 hours, the free oil content was measured and recorded. After stabilization of the suspension at room temperature for 24 hours, less than 2% free oil was determined.

[00224] Viscosity: The viscosity was 35.8 cP at 300 rpm, 44.8 cP at 200 rpm, and 67.7 cP at 100 rpm. Viscosity was also tested on a GRACE Instrument M5600 HPHT rheometer. The viscosity was kept above 50 centipoise at temperatures up to 250°F (about 121°C) at 100 s ^-1 . (Fig. 1).

[00225] Sand Suspension: The resulting hydration fluid was also used in the sand suspension study. Sand in the amount of 2 pounds/gallon (about 240 kg/m ³ ) was well mixed with liquid, then placed in an oven at 85°C for 20 hours. No noticeable sand settling was observed.

[00226] Example 1a - Comparative example (without diethylene glycol hexyl ether).

[00227] By comparison, completely replacing the diethylene glycol hexyl ether in the slurry with ODC oil after 24 hours produced a stable slurry containing less than 2% free oil, but low viscosity measurements indicated poor hydration: 3.1 cP at 300 rpm . 3.1 cP at 200 rpm and 3.8 cP at 100 rpm. Viscosity was also tested on a GRACE Instrument M5600 HPHT rheometer. The viscosity was kept below 10 centipoise at 100 s ^-1 and temperatures from 75°F (about 24°C) to 300°F (about 149°C). The sand could not be suspended.

[00228] Table 3. Composition 1-2 suspensions

Weight, g Oil ODC 58.1 Benton 155 1.48 Diethylene glycol hexyl ether 0 Solvay Associated Water Soluble Polymer 42.5 Water 0.1

[00229] Example 2 - Suspension containing Rhodiasolv® (Rhodiasolv) IRIS (diester solvent).

[00230] The procedure for obtaining a suspension: The suspension was obtained using a vertical mixer. ODC oil was added to the beaker and then Bentone® 155 was added and mixed at 750 rpm to disperse. Rhodiasolv® (Rhodiasolv) IRIS was then added and mixed for 5 minutes. Next, the water-soluble polymer powder was added. The stirring speed was adjusted to maintain swirl until all of the polymer powder was mixed into the mixture. The final speed was approximately 1400 rpm. Before the study, the suspension was left to mix for another 15 minutes.

[00231] Hydration procedure: Fresh water was used for hydration. 1.45 g of the suspension was added to 200 ml fresh water in a 500 ml Waring mixer over 3 minutes at 2500 rpm. To reduce the foam level, the liquid was centrifuged for 1 minute at 4000 rpm. Immediately afterwards, the viscosity was measured using an OFITE Model 900 viscometer.

[00232] Slurry Stability Test: The temperature of the slurry was adjusted to 75°F (about 24°C) (+/- 3°F (+/- 3°C)). Prior to testing, a slurry sample from the mixer was stirred for 5 minutes. The suspension was poured into a graduated cylinder up to the 100 ml mark. The cylinder was covered, placed in an incubator at 75°F (about 24°C) (+/- 3°F (+/- 3°C)) and left intact for 24 hours. After 24 hours, the free oil content was measured and recorded. After stabilization of the suspension at room temperature for 24 hours, less than 2% free oil was determined.

[00233] Table 4. Composition 2-1 of the suspension

Weight, g Oil ODC 32.34 Bentone® (Benton) 155 0.62 Rhodiasolv® (Rhodiasolv) IRIS 25.00 Solvay Associated Water Soluble Polymer 41.39

[00234] Viscosity: The viscosity was 56.2 cP at 300 rpm, 74.7 cP at 200 rpm, and 112.7 cP at 100 rpm. Viscosity was also tested on a GRACE Instrument M5600 HPHT rheometer. The viscosity was kept above 50 centipoise at temperatures up to 250°F (about 121°C) at 100 s ^-1 . (Fig. 2).

[00235] Example 2a - Comparative example (without Rhodiasolv® (Rhodiasolv) IRIS).

[00236] By comparison, completely replacing Rhodiasolv® (Rhodiasolv) IRIS in suspension with ODC oil resulted in a stable suspension containing approximately 10% free oil after 24 hours, but low viscosity measurements indicated poor hydration: 3.0 cP at 300 rpm, 3.2 cP at 200 rpm and 3.5 cP at 100 rpm. Viscosity was also tested on a GRACE Instrument M5600 HPHT rheometer. The viscosity was kept below 10 centipoise at 100 s ^-1 and temperatures from 75°F (about 24°C) to 300°F (about 149°C). The sand could not be suspended.

[00237] Table 5. Composition 2-2 suspensions

Weight, g Oil ODC 57.34 Bentone® (Benton)155 0.62 Solvay Associated Water Soluble Polymer 41.39

[00238] Example 3 - Solvent study (comparative).

[00239] The slurry was made using a Waring mixer. The mixing bowl was filled with ODC oil as drilling fluid and Hexyl Carbitol™ solvent. Next was added Bentone® (Benton) 155. The mixture was stirred at 1500 rpm for dispersion. Water was added as a clay activator and mixed for 5 minutes. An associative water soluble polymer powder from Solvay was then added. The stirring speed was adjusted to maintain swirl until all the powder was mixed into the mixture. The final speed was about 2000 rpm. Before the study, the suspension was left to mix for another 20 minutes.

[00240] Table 6. Comparative suspension formulations

Active solvent level (%) 0% 0.2% 5.0% ten% twenty% Oil ODC as drilling fluid 58.1 57.9 53.0 48.0 37.9 Bentone® (Benton) 155 1.48 1.48 1.48 1.48 1.48 Solvent Hexyl Carbitol™ 0.0 0.2 5.05 10.11 20.22 Solvay Associated Water Soluble Polymer 41.4 41.4 41.4 41.4 41.4 Water 0.1 0.1 0.1 0.1 0.1

[00241] Changed the ratio of oil as a drilling fluid and solvents Hexyl Carbitol™, corresponding to a given active level of the solvent within the suspension. The amount of all other additives remained the same.

[00242] Hydration Procedure: Eagle Ford water with 1K TDS was used. 200 ml of 1K TDS water was poured into a 500 ml mixer bowl. The water was stirred at 2500 rpm using a Waring mixer. 1.45 g of the suspension was added to the bowl of the mixer and mixed for 30 seconds. 150 ml of the liquid was poured into a beaker and then the viscosity was measured for 10 minutes using an OFITE Model 900 viscometer available from OFI Testing Equipment, Inc. (Houston, Texas).

[00243] Table 7. Apparent viscosity (cP) studies (comparative)

Content Active solvent level (%) Time (min) one 2 3 5 ten Apparent viscosity (cP) @100 rpm 0 7.3 7.3 7.3 7.2 7.2 0.2 6.5 6.7 6.8 6.9 6.9 5 7.3 7.2 7.1 7.1 7.1 ten 9 8.9 9.1 9.2 9.3 twenty 10.6 10.4 9.6 9.6 9.5

[00244] The apparent viscosity was measured over 10 minutes to determine the rate of hydration as well as the final viscosity. Although active solvent levels were increased from 0% to 20%, there was no significant improvement in final viscosity. The viscosity number did not change during such a period of time, which means that hydration has not progressed beyond its initial stage.

[00245] Table 8. Viscosity (cP) studies (comparative)

Content Active solvent level (%) 0 0.2 5 ten twenty Viscosity (cP) 300 rpm 10.2 10.7 7.4 6.4 11.1 200 rpm 8.8 9.7 7.5 6.9 11.6 100 rpm 9.1 9.7 9.1 8.1 12.4

[00246] Viscosity at 100-300 rpm was measured for a slurry containing 0 to 20% active solvent. No significant differences were observed within this range.

[00247] Example 4 - Solvent study.

[00248] The slurry was made using a Waring mixer. ODC oil was added as drilling fluid and Hexyl Carbitol™ solvent was added to the mixing bowl. Next was added Bentone® (Benton) 155. The mixture was stirred at 1500 rpm for dispersion. Water was added as a clay activator and mixed for 5 minutes. An associative water soluble polymer powder from Solvay was then added. The stirring speed was adjusted to maintain swirl until all the powder was mixed into the mixture. The final speed was about 2000 rpm. Before the study, the suspension was left to mix for another 20 minutes.

[00249] Table 9. Suspension formulations

Active solvent level (%) thirty% 40% fifty% 57% Oil ODC as drilling fluid 27.8 17.7 7.6 0.5 Bentone® (Benton) 155 1.48 1.48 1.48 1.48 Solvent Hexyl Carbitol™ 30.32 40.43 50.54 57.62 Solvay Associated Water Soluble Polymer 41.4 41.4 41.4 41.4 Water 0.1 0.1 0.1 0.1

[00250] Changed the ratio of oil as a drilling fluid and solvents Hexyl Carbitol™, corresponding to a given active level of the solvent within the suspension. The amount of all other additives remained the same.

[00251] Hydration Procedure: Eagle Ford water with 1K TDS was used. 200 ml of 1K TDS water was poured into a 500 ml mixer bowl. The water was stirred at 2500 rpm using a Waring mixer. 1.45 g of the suspension was added to the bowl of the mixer and mixed for 30 seconds. 150 ml of liquid was poured into a beaker, and then the viscosity was measured using an OFITE Model 900 viscometer for 10 minutes.

[00252] Table 10. Apparent viscosity (cP) studies

Content Active solvent level (%) Time (min) one 2 3 5 ten Apparent viscosity (cP) @100 rpm thirty 30.3 35.1 36.4 35.7 31 40 31.8 34.6 35 34.2 34.3 fifty 48.2 49.3 43.2 36.4 36.3 57 49.7 66.8 68.6 56.9 45.2

[00253] The apparent viscosity was measured over 10 minutes to determine the rate of hydration as well as the final viscosity. Solvent levels from 30% to 57% resulted in a 3 to 5 times increase in viscosity compared to an active level of 0 to 20%. No significant difference in viscosity was observed after 1 minute and 10 minutes, which means that the hydration process was completed after only 1 minute.

[00254] Table 11. Viscosity studies (cp)

Content Active solvent level (%) thirty 40 fifty 57 Viscosity (cP) 300 rpm 11.3 26.6 32.1 20.6 200 rpm 11.7 34.2 36 26 100 rpm 13 47.4 50.6 35.9

[00255] Viscosity at 100-300 rpm was measured for a slurry containing 30 to 57% active solvent. The formulation containing 30% active solvent did not show a significant difference in viscosity compared to the formulation containing 20% active solvent. However, formulations with 40-57% active solvent showed a significant improvement in viscosity. An active level of 40 to 50% showed the maximum viscosity range.

[00256] The proposed subject matter has been described with reference to specific details of its specific embodiments. Such details are not intended to be construed as limiting the scope of the proposed subject matter except and to the extent that they are included in the appended claims.

[00257] Accordingly, the exemplary embodiments described herein are well adapted in terms of achieving the goals and benefits mentioned, as well as those goals and benefits that are inherent in these implementation options. The specific implementations described above are illustrative only, as the exemplary implementations described herein may be modified and practiced in various but equivalent ways that will be apparent to those skilled in the art who benefit from the ideas set forth herein. . In addition, no restrictions are directed to the details of construction or design shown in this document, except as described below in the claims. Therefore, it is obvious that the specific illustrative implementation options described above can be changed, combined or modified, and all such options are considered within the scope and spirit of the exemplary implementation options described herein. The exemplary embodiments provided herein, described herein by way of illustration, may suitably be practiced in the absence of any element not expressly described herein and/or any optional element described herein. Although the compositions and methods are described in terms of "having", "comprising", or "comprising" various components or steps, said compositions and methods may also "consist essentially of" or "consist of" various components, materials, and steps. As used herein, the term "consisting essentially of" is to be understood to mean including the recited components, substances, or steps, and such additional components, substances, or steps that do not significantly affect the essential and novel properties of the composition or method. In some embodiments, a composition of the present invention that "consists essentially of" the listed components or substances does not contain any additional components or substances that change the basic and new properties of the composition. If there is any conflict in the use of a word or term in the specification of the present invention and in one or more patent or other documents that may be incorporated herein by reference, definitions that are consistent with the present specification should be used.

Claims (38)

1. A well treatment fluid concentrate comprising: a. a water-soluble polymer containing: i. at least one hydrophobic monomer selected from the group consisting of n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide, myristyl methacrylate, myristyl methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof, and ii. at least one hydrophilic monomer selected from the group consisting of acrylate, acrylate salts, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salts, and combinations thereof; b. at least one substance selected from a surfactant, a mutual solvent, or a combination thereof, while the total amount of a surfactant and/or mutual solvent in the concentrate is from 10 to 57% by weight. based on the total weight of the concentrate; c. a hydrophobic solvent having a hydrophilic-lipophilic balance (HLB) value of 0 to 6; and d. from 0.2 to 3% wt. suspending agent, wherein said concentrate is a non-settling suspension. 2. The concentrate according to claim. 1, characterized in that the specified polymer contains hydrophilic monomers in a total amount of from about 50% of the mass. up to about 99.9% of the mass. relative to the weight of the polymer. 3. The concentrate according to claim. 1, characterized in that the specified polymer contains hydrophobic monomers in a total amount of from about 0.01 wt%. up to about 50% wt. relative to the weight of the polymer. 4. The concentrate according to claim 1, characterized in that the polymer in the final position of the end group contains a thiocarbonylthio functional group. 5. The concentrate according to claim. 1, characterized in that the molecular weight of the specified polymer is from about 10,000 to about 20,000,000. 6. The concentrate according to claim 1, additionally containing water in an amount of from about 0.01% of the mass. up to about 5% wt. based on the total weight of the concentrate. 7. The concentrate according to claim 1, containing a surfactant selected from the group consisting of alkylbenzenesulfonates, alkyl betaines, alkylamidopropyl betaines, and combinations thereof. 8. The concentrate according to claim 1, characterized in that the total amount of surfactant and / or mutual solvent in the concentrate is from 30 to 57 wt%. based on the total weight of the concentrate. 9. A concentrate according to claim 1 containing a mutual solvent selected from the group consisting of compounds of formula I:

where each R ₁ , R ₂ and R ₃ independently represents a linear or branched C ₁ -C ₈ alkyl group; compounds of formula II:

where each R ₁ , R ₂ , R ₃ and R ₄ independently represents a linear or branched C ₁ -C ₈ alkyl group; ethoxylated and/or propoxylated linear or branched alcohols; and their combinations. 10. The concentrate according to claim 1, characterized in that the hydrophobic solvent is selected from the group consisting of toluene, xylene, ethylbenzenes, aromatic naphthas, produced hydrocarbons, diesel fuel, kerosene, paraffin oil, mineral oil, and combinations thereof. 11. The concentrate according to claim 1, wherein the suspending agent is selected from the group consisting of organophilic bentonite, hectorite, smectite, montmorillonite, attapulgite, kaolinite, and any combination thereof. 12. A method for fracturing a subterranean formation, comprising the step of injecting a water-based fracturing fluid into at least a portion of the subterranean formation at pressures sufficient to fracture the formation, said fracturing fluid comprising the concentrate of claim 1. 13. The method of claim 12 wherein the fracturing fluid further comprises water. 14. A method of fracturing a subterranean formation, comprising the steps of injecting an initial proppant-depleted water-based fluid system containing a friction reducing polymer into at least a portion of the subterranean formation at a rate that causes frictional pressure loss, followed by pumping the proppant-rich fluid system a water-based fluid system containing a friction reducing polymer and a concentrate according to claim 1, into at least a portion of a subterranean formation, wherein said water-based proppant-depleted hydraulic fluid system contains a friction reducing polymer that is the same friction reducing polymer. friction that is contained in or different from a proppant-rich water-based fluid system. 15. A method of gravel backfilling, which includes moving a working fluid through at least one pump and an underground gravel pack, while said working fluid carries a gravel pack for placement in a wellbore and contains a concentrate according to claim 1. 16. A method for drilling out a wellbore, comprising milling a barrier in the wellbore, circulating a working fluid containing the concentrate of claim 1 through the wellbore, and removing waste from the wellbore in the circulating fluid. 17. A system for wellbore cementing operations, including a buffer fluid containing a concentrate according to claim 1 and a pump working fluid associated by means of a fluid connection with a pipe in fluid communication with the wellbore, said pipe being configured to transfer the buffer fluid into wellbore. 18. The method of cementing an oil well, including providing a cementing fluid containing an aqueous solution, hydraulic cement and a cement suspension reagent containing a concentrate according to claim 1; placing a cementing fluid in a wellbore traversing a subterranean formation; and allowing the cementing fluid to set in said formation. 19. A method for treating a subterranean well containing a wellbore, comprising the steps of: (i) placing a well treatment fluid containing the concentrate of claim 1 into the wellbore so that said well treatment fluid is in contact with a liner, a well screen , perforations, natural or man-made fissures or subterranean formations, or combinations thereof; and (ii) allowing the well treatment fluid to pass into the liner, well screen, perforations, natural or man-made fractures, or the subterranean formation, wherein after the well treatment fluid has passed, further fluid movement between the wellbore and the subterranean formation is prevented or restricted. 20. A well treatment fluid concentrate, comprising: a. water-soluble polymer containing: i. at least one hydrophobic monomer selected from the group consisting of n-hexyl methacrylate, n-octyl methacrylate, octyl methacrylamide, lauryl methacrylate, lauryl methacrylamide, myristyl methacrylate, myristyl methacrylamide, pentadecyl methacrylate, pentadecyl methacrylamide, cetyl methacrylate, cetyl methacrylamide, oleyl methacrylate, oleyl methacrylamide, erucyl methacrylate, erucyl methacrylamide, and combinations thereof, and ii. at least one hydrophilic monomer selected from the group consisting of acrylate, acrylate salts, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salts, and combinations thereof; b. at least one substance selected from a surfactant, a mutual solvent, or a combination thereof, while the total amount of a surfactant and/or mutual solvent in the concentrate is from 10 to 57% by weight. based on the total weight of the concentrate; c. a hydrophobic solvent having a hydrophilic-lipophilic balance (HLB) value of 0 to 6; and d. from 0.2 to 10% wt. suspending agent based on the total weight of the concentrate, wherein said concentrate is a non-settling suspension.

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