Polymer system for particle dispersion

Abstract

The present disclosure provides an aqueous composition comprising water and a polymer, the polymer comprises at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, myristyl (meth) acrylate, pentadecane (meth) acrylate, cetyl (meth) acrylate, oleyl (meth) acrylate, erucyl (meth) acrylate, vinyl acetate, vinyl propionate, and at least one of the following monomers. A vinyl versatate, a vinyl stearate, an allyl acetate, an allyl propionate, an allyl versatate, an allyl stearate, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of an acrylate, an acrylate, an acrylamide, a 2-acrylamido-2-methylpropanesulfonic acid, a 2-acrylamido-2-methylpropanesulfonic acid salt, and combinations thereof, wherein the composition exhibits a particle suspension time of at least 1 hour.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of the invention patent application with the application date of November 28, 2017, application number 201780073933.5, and invention name “Polymer system for particle dispersion”. Background Art

[0002] There are many fields in which it is crucial to keep particles in suspension (for example particles of pigments in paint or varnish type compositions). More precisely, in the field of oil recovery, many stages are carried out by injecting fluids under pressure into underground formations, where it is often useful to keep the particles in suspension in order to prevent them from settling out, despite the extreme temperature and pressure conditions typically used in underground formations.

[0003] For the purpose of suppressing the phenomenon of sedimentation separation, it is possible to add additives that make it possible to keep particles suspended. A certain number of these additives have been described, and these additives particularly include crosslinked or non-crosslinked polymers, polysaccharides and their derivatives, such as xanthan gum, cellulose ethers or alternative guar gum, and its derivatives crosslinked with borates or zirconates. However, it can be seen that when the temperature exceeds 150°C, these suspending agents decompose. This limitation therefore makes these additives unable to be used for applications under higher temperatures (typically greater than 150°C, often between 150°C and 200°C, indeed even ranges up to greater than 200°C). In addition, near oil-bearing rocks, i.e., particularly in the case of using these agents in fluids such as drilling fluids, completion fluids, fracturing fluids, acidizing fluids or spacer fluids, they exhibit the disadvantage of decomposing in the form of insoluble residues that cannot be properly removed. Summary of the invention

[0004] The present disclosure provides polymer systems that can be used to maintain particle dispersion for extended periods of time. The polymer systems can also be used to maintain particle dispersion for extended periods of time at elevated temperatures and / or under high saline conditions. Dry polymer systems that can withstand rapid hydration are also provided.

[0005] In an embodiment, a method for fracturing a subterranean formation comprises the step of injecting an aqueous fracturing fluid into at least a portion of the subterranean formation at a pressure sufficient to fracture the formation, wherein the fracturing fluid comprises a polymer comprising:

[0006] at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and

[0007] At least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof.

[0008] In another embodiment, a method of acidizing a subterranean formation penetrated by a wellbore includes the steps of:

[0009] (a) injecting a treatment fluid into the wellbore at a pressure below a fracturing pressure of a subterranean formation, the treatment fluid having a first viscosity and comprising an aqueous acid solution and a polymer, the polymer comprising:

[0010] at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and

[0011] at least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof;

[0012] (b) forming at least one void in the subterranean formation with the treatment fluid; and (c) allowing the treatment fluid to reach a second viscosity greater than the first viscosity.

[0013] Also provided is an aqueous composition comprising water and a polymer, the polymer comprising:

[0014] at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and

[0015] At least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamides, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonate, and combinations thereof, wherein the composition exhibits a particle suspension time of at least 1 hour.

[0016] In yet another embodiment, a powder composition comprises polymer particles having a particle size from about 5 μm to about 400 μm and a molecular weight ranging from about 10,000 to 20,000,000, wherein the polymer comprises acrylamide and 2-acrylamido-2-methylpropanesulfonic acid monomers and at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, erucyl (meth)acrylate, erucyl (meth)acrylamide, and combinations thereof. DETAILED DESCRIPTION

[0017] The inventors have found polymer systems for particle dispersion, which can be used unexpectedly in a lower amount compared to conventional carrier systems, while providing enhanced particle dispersion capabilities. In an embodiment, an aqueous composition comprising water and a polymer of the present disclosure exhibits a particle suspension time of at least 1 hour. In another embodiment, the particle suspension time lasted at least 2 hours. In another embodiment, the particle suspension time lasted at least 4 hours. In another embodiment, the particle suspension time lasts for a period of 24 hours. In an embodiment, the aqueous composition makes particle suspension at a temperature of about 68 ° F to about 350 ° F (or any temperature within this range).

[0018] In an embodiment, these polymer systems are used in combination with underground formations. In the present specification, the concept of "underground formation" should be understood in its broadest sense and includes both rocks containing hydrocarbons (especially oil), and various rock layers that are penetrated in order to reach such oil-bearing rocks and ensure the extraction of hydrocarbons. Within the meaning of the present specification, the concept of "rock" is used to represent any type of constituent material of a solid underground formation, whether or not the material constituting it is strictly speaking a rock. Therefore, in particular, the expression "oil-bearing rock" is used herein as a synonym for "oil-bearing reservoir" and represents any underground formation containing hydrocarbons, especially oil, regardless of the nature of the material containing these hydrocarbons (e.g., rock or sand).

[0019] Among the fluids injected under pressure into underground formations, mention may be made in particular of the various fluids used for the completion and servicing of wells, in particular drilling fluids, whether they are used to reach the oil-bearing rock or to drill into the reservoir itself ("drilling"), or fracturing fluids, or alternatively completion fluids, control or servicing fluids or annular fluids or packer fluids or spacer fluids or acidizing fluids, or also fluids used for cementing.

[0020] In an embodiment, the polymer comprises at least one hydrophobic monomer selected from the following: n-hexyl (meth) acrylate, n-octyl (meth) acrylate, octyl (meth) acrylamide, lauryl (meth) acrylate, lauryl (meth) acrylamide, myristyl (meth) acrylate, myristyl (meth) acrylamide, pentadecyl (meth) acrylate, pentadecyl (meth) acrylamide, cetyl (meth) acrylate, cetyl (meth) acrylamide, oleyl (meth) acrylate, oleyl (meth) acrylamide, mustard (meth) acrylate, mustard (meth) acrylamide, and combinations thereof; and at least one hydrophilic monomer selected from the following: acrylate, acrylate, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salt, and combinations thereof. In an embodiment, the hydrophilic monomer comprises acrylamide and 2-acrylamido-2-methylpropanesulfonic acid.

[0021] In an embodiment, the polymer comprises a total amount of hydrophilic monomers from about 50 wt % to about 99.9 wt % of the polymer. In another embodiment, the polymer comprises a total amount of hydrophilic monomers from about 80 wt % to about 99.9 wt % of the polymer. In another embodiment, the polymer comprises a total amount of hydrophobic monomers from about 0.01 wt % to about 50 wt % of the polymer. In another embodiment, the polymer comprises a total amount of hydrophobic monomers from about 0.01 wt % to about 20 wt % of the polymer.

[0022] In embodiments, the polymer comprises a thiocarbonylthio functional group at a terminal position.

[0023] In an embodiment, the polymer is in the form of a powder having a particle size from about 5 μm to about 400 μm. In another embodiment, the particle size is in the range of from about 50 μm to about 200 μm. In yet another embodiment, the polymer is in a slurry comprising a solvent or hydrocarbon phase, and a suspension aid, wherein the particle size of the polymer powder in the slurry is in the range of from about 5 μm to about 400 μm.

[0024] In another embodiment, the polymer powder comprises polymer particles having a particle size from about 5 μm to about 400 μm and a molecular weight from about 10,000 g / mol to about 20,000,000 g / mol, wherein the polymer comprises acrylamide and 2-acrylamido-2-methylpropanesulfonic acid monomers and at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, erucyl (meth)acrylate, erucyl (meth)acrylamide, and combinations thereof. In an embodiment, the hydrophobic monomer is selected from lauryl (meth)acrylate, lauryl (meth)acrylamide, and combinations thereof.

[0025] In an embodiment, the polymer of the present disclosure is prepared via micellar polymerization. The polymer system comprises a sequential copolymer (P) for keeping solid particles (p) suspended in a fluid (F), the sequential copolymer comprising at least one chain (C) of a type obtained by micellar polymerization, in which the chain (C) is soluble.

[0026] More precisely, according to a particular aspect, the subject of the present disclosure is the use of the above-mentioned sequential copolymer as a suspending agent in a fluid (F) injected under pressure into an underground formation, wherein said fluid (F) contains at least a portion of these solid particles (p) and / or after the injection of the fluid is brought into contact with at least a portion of these solid particles (p) inside the underground formation.

[0027] Within the meaning of the present description, the term "chain soluble in fluid (F)" is understood to mean a chain (C) which typically has a solubility in fluid (F) greater than or equal to 0.5% (5,000 ppm) at 20°C, preferably greater than or equal to 1%.

[0028] Micellar polymerization schematically includes the polymerization of hydrophilic monomers in a hydrophilic medium, which contains micelles containing hydrophobic monomers. Examples of micellar polymerization have been particularly described in U.S. Patent No. 4,432,881 or in Polymer [polymer], Vol. 36, No. 16, pp. 3197-3211 (1996), and other details can be referenced to these documents.

[0029] The chain (C) of the polymer (P) used according to the invention is a chain which as a whole is soluble in the fluid (F) and which is mainly formed by a series of hydrophilic units interrupted at different points by a plurality of hydrophobic sequences (B) of approximately the same size. The polymer of the present disclosure may consist of the chain (C) or may be a block copolymer in which the chain (C) constitutes one of the blocks.

[0030] The hydrophobic sequence (B) is preferably a polymer sequence that is insoluble in the fluid (F), typically having a solubility in the fluid (F) of less than or equal to 0.1% (1,000 ppm) at 20°C.

[0031] The copolymer (P) comprising the above chains (C) is suitable for keeping solid particles (p) in suspension. They may be particles present in an underground formation and / or particles injected into an underground formation, typically associated with the copolymer (e.g. like proppant particles).

[0032] According to the invention, micellar polymerization may typically be used, in which the following are copolymerized (typically by a free radical pathway) in an aqueous dispersion medium (typically water or a water / alcohol mixture): hydrophilic monomers, which are dissolved or dispersed in the medium; and hydrophobic monomers, which are in surfactant micelles formed in the medium by introducing a surfactant into the medium at a concentration above the critical micelle concentration (cmc) of the surfactant.

[0033] Preferably, the content of hydrophobic monomers, corresponding to the ratio of the weight of hydrophobic monomers relative to the total weight of hydrophobic and hydrophilic monomers, is greater than or equal to 0.01%, preferably greater than 0.1%, indeed even greater than 0.2%, and less than or equal to 5%. Overall, the percentage of hydrophobic units in chain (C) is of the same order of magnitude, typically greater than or equal to 0.05%, preferably greater than 0.1%, indeed even greater than 0.2%, and less than or equal to 5%.

[0034] In micellar polymerization, the hydrophobic monomers present in these micelles are said to be in a "micellar solution." The micellar solution referred to is a microscopically inhomogeneous system that is generally isotropic, optically transparent and thermodynamically stable.

[0035] It should be noted that the micellar solutions of the type used in micellar polymerization should be distinguished from microemulsions. Specifically, compared to microemulsions, micellar solutions are formed at any concentration exceeding the critical micelle concentration of the surfactant used, with the only condition being that the hydrophobic monomers are soluble at least to a certain extent in the internal space of these micelles. In addition, micellar solutions differ from emulsions in that there is no internal homogeneous phase: these micelles contain a very small number of molecules (typically less than 1000, generally less than 500 and typically from 1 to 100, most often 1 to 50 monomers and at most several hundred surfactant molecules when there is a surfactant) and micellar solutions generally have physical properties similar to those of surfactant micelles without monomers. In addition, in general, micellar solutions are transparent relative to visible light, considering the small size of the micelles (which do not cause refraction phenomena), which is different from the droplets of emulsions (these droplets refract light and make the emulsion produce its characteristic turbidity or white appearance).

[0036] The micellar polymerization technique produces characteristic sequential polymers, each of which contains a number of hydrophobic blocks of approximately the same size, and wherein this size can be controlled. Specifically, given the confinement of the hydrophobic monomers in the micelle, each hydrophobic block contains approximately the same defined number n. H hydrophobic monomers, it is possible to calculate this number n as follows H (Macromolecular Chem. Physics, 202, 8, 1384-1397, 2001): n H =N agg .[M H ] / ([Surfactant]-cmc) in: N agg is the aggregation number of the surfactant, which reflects the number of surfactants present in each micelle; [M H ] is the molar concentration of the hydrophobic monomer in the medium; [Surfactant] is the molar concentration of surfactant in the medium; and cmc is the critical micelle (molar) concentration.

[0037] The micellar polymerization technique thus makes it possible to advantageously control the hydrophobic units introduced into the polymer formed, namely: generally controlling the molar fraction of the hydrophobic units in the polymer (by adjusting the concentration ratio of the two monomers); and more specifically controlling the number of hydrophobic units present in each of the hydrophobic blocks (by varying the ratio affecting n defined above). H parameters).

[0038] The chains (C) obtained by micellar polymerization, which are entirely soluble in a fluid (F), comprise: a hydrophilic component consisting of hydrophilic monomers, corresponding to hydrophilic polymer chains, which, if introduced alone into the fluid (F), would have a solubility at 20° C. typically greater than or equal to 1% (10,000 ppm), A hydrophobic component consisting of hydrophobic sequences each having a solubility in the fluid (F) at 20° C. typically less than or equal to 0.1% (1000 ppm).

[0039] In many cases, the chain (C) can be described as a hydrophilic chain with the above-mentioned solubility (at least 1%), to which the pendant hydrophobic groups are grafted. In particular, in this case, the chain (C) as a whole has a solubility in the fluid (F) preferably greater than or equal to 0.1%, indeed even 0.5% at 20°C.

[0040] According to a particular embodiment, the chains (C) are of the type obtained by a process comprising a stage (e) of micellar radical polymerization in which: hydrophilic monomers, which are dissolved or dispersed in the aqueous medium (M), typically water or a water / alcohol mixture; hydrophobic monomers in the form of micellar solutions, ie solutions containing micelles comprising these hydrophobic monomers in a dispersed state in a medium (M) (this dispersed state may in particular be obtained using at least one surfactant); and At least one free radical polymerization initiator, which is typically water soluble or water dispersible.

[0041] According to a preferred embodiment, the chains (C) are of the type obtained by a process comprising a stage (E) of micellar free radical polymerization in which: hydrophilic monomers, which are dissolved or dispersed in the aqueous medium (M), typically water or a water / alcohol mixture; hydrophobic monomers in the form of micellar solutions, ie solutions containing micelles comprising these hydrophobic monomers in a dispersed state in a medium (M) (this dispersed state may in particular be obtained using at least one surfactant); at least one free radical polymerization initiator, which is typically water soluble or water dispersible; and at least one free radical polymerization controller.

[0042] Stage (E) is similar to stage (e) described above, but with the use of additional control agents. This stage, known under the name "controlled nature micellar free radical polymerization", has been described in particular in WO 2013 / 060741. All alternatives described in this document can be used here.

[0043] Within the meaning of the present specification, the term "free radical polymerization controller" is understood to mean a compound capable of extending the lifetime of the growing polymer chain in a polymerization reaction and conferring activity or controllability to the polymerization. This controller is typically a reversible transfer agent as used in controlled radical polymerization represented by the terms RAFT or MADIX (which typically use a reversible addition-fragmentation transfer process), such as those 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.

[0044] In an embodiment, the free radical polymerization control agent used in stage (E) is a compound comprising a thiocarbonylthio -S (C=S)- group. Thus, for example, it may be a compound comprising a xanthate group (with a -SC=SO- functional group), such as a xanthate. Other types of control agents (such as those used in CRP or ATRP) can be envisaged.

[0045] According to a particular embodiment, the control agent used in stage (E) may be a polymer chain resulting from a controlled free-radical polymerization and carrying groups capable of controlling free-radical polymerization (itself a polymer chain of the “living” type, of a well-known type). Thus, for example, the control agent may be a polymer chain (preferably hydrophilic or water-dispersible) functionalized at the chain end with a xanthate group, or more generally comprising a -SC=S- group, for example obtained according to the MADIX technique.

[0046] Alternatively, the control agent used in stage (E) is a non-polymeric compound carrying groups ensuring control of the free-radical polymerization, in particular thiocarbonylthio —S(C═S)— groups.

[0047] According to a specific alternative form, the free radical polymerization control agent used in stage (E) is a polymer, advantageously an oligomer, having water-soluble or water-dispersible properties and carrying thiocarbonylthio -S(C=S)- groups (e.g. xanthate -SC=SO- groups). This polymer, which is able to act both as a control agent and a monomer for the polymerization in stage (E), is also indicated as a "prepolymer" in the continuation of this description. Typically, this prepolymer is obtained by free radical polymerization of hydrophilic monomers in the presence of a control agent carrying thiocarbonylthio -S(C=S)- groups (e.g. xanthate). Thus, for example, according to an advantageous embodiment presented at the end of this description, the control agent used in stage (E) can advantageously be a stage (E) of controlled free radical polymerization preceding stage (E). 0 ) is obtained at the end of the prepolymer with thiocarbonylthio -S(C=S)- groups (e.g. xanthate -SC=SO- groups). At this stage (E 0 ), the following can typically be brought into contact: a hydrophilic monomer (advantageously the same as that used in stage (E); a free radical polymerization initiator and a control agent carrying a thiocarbonylthio -S(C=S)- group, such as a xanthate.

[0048] Use the above stage (E) before stage (E) 0 ) makes it possible to render these control agents hydrophilic, schematically by converting a large number of control agents carrying thiocarbonylthio functional groups (e.g. xanthates, which are rather hydrophobic in nature) from prepolymers that are soluble or dispersible in the medium (M) of stage (E). Preferably, at stage (E 0 ) have short polymer chains, for example sequences comprising less than 50 monomer units, indeed even less than 25 monomer units, for example between 2 and 15 monomer units.

[0049] When stage (E) is used, the polymer according to the invention comprises chains (C) with a "controlled" structure, ie all chains (C) present on the polymer have approximately the same size and the same structure. Chains (C) especially comprise approximately the same number and proportion of blocks (B).

[0050] The specific polymers (P) used in the context of the present invention turn out to provide a particularly effective control effect on fluids due to the presence of hydrophobic sequences in the hydrophilic polymer chains: without wishing to be bound by theory, it appears that hydrophobic units within one hydrophilic chain and / or different hydrophilic chains have a tendency to associate with each other.

[0051] In an embodiment, the injected fluid (F) comprises polymer (P) but no solid particles (p), and it encounters said particles (p) in the underground formation after its injection. The association between the particles and the polymer then takes place in situ. Such a fluid may, for example, be injected during a drilling operation and the rock cuttings formed during the drilling then perform the role of the particles (p) in situ.

[0052] According to an alternative variant, the injected fluid (F) comprises, before the injection, at least a portion and generally all of the particles (p) associated with the polymer (P), it being understood that it may optionally encounter other particles (p) within the underground formation.

[0053] Two forms can be specifically envisaged in this context:

[0054] Version 1: The polymer (P) and the particles (p) are mixed, typically by adding the particles (p) in dry state or optionally in dispersed state, to a composition comprising the polymer (P) in solution, at an operational or upstream location during formulation of the fluid (F).

[0055] Form 2: The fluid (F) is advantageously manufactured at the operating site from a composition (premix) prepared upstream, generally comprising the polymer (P) and at least a portion of the particles (p) in a dispersion liquid (hereinafter indicated by the term "blend"). To form the fluid (F), this blend is mixed with the other ingredients of the fluid (F).

[0056] In some embodiments, the polymer (P) associated with the particles (p) can be used as a dispersing and stabilizing agent for dispersing the particles (p) while providing the function of an agent for controlling fluid loss.

[0057] The concept of "controlling fluid loss" refers here to the suppression of the "fluid loss" effect observed when injecting a fluid under pressure in an underground formation: the liquid present in the fluid has a tendency to penetrate into the constituent rocks of the underground formation, which can damage the well, indeed even compromise its integrity. When these fluids used under pressure contain insoluble compounds (which is very often the case, in particular for oil-cement slurries or drilling or fracturing fluids), the fluid loss effect simultaneously entails the risk of losing control of the injected fluid, the concentration of insoluble compounds of the fluid increases, which can lead to an increase in viscosity, which affects the fluidity of the fluid.

[0058] In particular when the fluid (F) is a fracturing fluid, a cementing fluid or a drilling fluid, the presence of the copolymer (P) makes it possible to obtain control of fluid losses by limiting, indeed even completely inhibiting, the escape of the fluid (F) (typically water or an aqueous composition) into the underground formation in which production is taking place.

[0059] Various specific advantages and embodiments of the present invention will now be described in more detail.

[0060] Fluid (F). The term "fluid" is understood to mean, within the meaning of the present description, any homogeneous or heterogeneous medium comprising a liquid or viscous carrier which optionally transports a liquid or gelled dispersed phase and / or solid particles, said medium being generally pumpable by means of means for injection under pressure used in the application under consideration.

[0061] The term "liquid or viscous carrier" of the fluid (F) is to be understood as meaning the fluid itself, or the solvent, in the case where the fluid contains dissolved compounds, and / or the continuous phase, in the case where the fluid contains dispersed elements (droplets of liquid or gelled dispersed phase, solid particles, and the like).

[0062] According to a highly suitable embodiment, the fluid (F) is an aqueous fluid. The term "aqueous" is here understood to mean that the fluid comprises water as liquid or viscous carrier, either as the sole component of the liquid or viscous carrier or in combination with other water-soluble solvents.

[0063] In the case of the presence of solvents other than water in the liquid or viscous carrier of the fluid (F), water advantageously remains the main solvent within the liquid or viscous carrier, advantageously present in a proportion of at least 50% by weight, indeed even at least 75% by weight, relative to the total weight of solvents in the liquid or viscous carrier.

[0064] In an embodiment, the fluid (F) is selected from fresh water, seawater, brine, brackish water, produced water, reclaimed water, industrial wastewater, wastewater associated with oil production, and combinations thereof.

[0065] Particle (p). The concept of "particle" is not limited to the concept of individual particles in the meaning used in this specification. It more generally refers to a solid entity that can be dispersed in a fluid in the form of objects (individual particles, aggregates, and the like), the overall size of which is less than 5 mm, preferably less than 2 mm, for example less than 1 mm.

[0066] The particles (p) according to the present invention may be selected from: calcium carbonate or cement, silica or sand, ceramics, clay, barite, hematite, carbon black and / or mixtures thereof.

[0067] According to a particular embodiment of the invention, the particles (p) are sand or cement particles.

[0068] Polymer (P).

[0069] Hydrophilic monomers. Chain (C) may typically comprise a monomer selected from:

[0070] Ethylenically unsaturated carboxylic acids, 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, monoethylenically unsaturated dicarboxylic acid monoesters containing from 1 to 3 and preferably from 1 to 2 carbon atoms, for example monomethyl maleate, vinylsulfonic acid, (meth)allylsulfonic acid, sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 1-allyloxy-2-hydroxypropylsulfonate, 2-hydroxy-3-acryloyloxypropylsulfonic acid, 2-hydroxy-3-methacryloyloxypropylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylphosphonic acid, α-methylvinylphosphonic acid and allylphosphonic acid;

[0071] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with C2-C3-alkanediols, for example 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl ethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate and polyalkylene glycol (meth)acrylates;

[0072] α,β-ethylenically unsaturated monocarboxylic acid amides and their N-alkyl and N,N-dialkyl derivatives, such as acrylamide, methacrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, morpholinyl(meth)acrylamide and hydroxymethylacrylamide (acrylamide and N,N-dimethyl(meth)acrylamide have proven to be particularly advantageous);

[0073] N-vinyllactams and derivatives thereof, such as N-vinylpyrrolidone or N-vinylpiperidone;

[0074] 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;

[0075] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with amino alcohols, for example N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl acrylate and N,N-dimethylaminopropyl (meth)acrylate;

[0076] 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:

[0077] N-diallylamine, N,N-diallyl-N-alkylamine, their acid addition salts and their quaternary ammonium products, wherein the alkyl group used is preferably a C1-C3 alkyl group;

[0078] N,N-diallyl-N-methylamine and N,N-diallyl-N,N-dimethylammonium compounds, such as the chlorides and bromides;

[0079] Nitrogen-containing heterocycles substituted by vinyl and allyl groups, such as N-vinylimidazole, N-vinyl-2-methylimidazole, heteroaromatic compounds substituted by vinyl and allyl groups, such as 2- and 4-vinylpyridine, 2- and 4-allylpyridine, and salts thereof;

[0080] sulfobetaines; and

[0081] Salts of the above monomers;

[0082] Mixtures and combinations of two or more of the above monomers and / or their salts.

[0083] According to a specific embodiment, these monomers may especially include acrylic acid (AA).

[0084] According to another embodiment, the hydrophilic monomers of chain (C) include (and typically consist of) (meth)acrylamide monomers, or more generally (meth)acrylamide-based monomers, including:

[0085] Acrylamide monomers, i.e. acrylamide (Am), dimethylacrylamide (DMA), their sulfonate derivatives, especially acrylamidomethylpropanesulfonic acid (AMPS);

[0086] Quaternary ammonium APTAC and sulfopropyl dimethyl ammonium propyl acrylamide;

[0087] Methacrylamide-based monomers, such as sulfopropyldimethylammoniumpropylmethacrylamide (SPP) or sulfohydroxypropyldimethylammoniumpropylmethacrylamide.

[0088] According to a specific embodiment, the hydrophilic monomer of chain (C) is acrylamide. The acrylamide is preferably an acrylamide that is not stabilized by copper.

[0089] According to a specific embodiment, the hydrophilic monomer of chain (C) is selected from acrylamide, dimethylacrylamide (DMA), acrylamidomethylpropanesulfonic acid (AMPS), acrylic acid (AA), salts thereof and mixtures thereof.

[0090] According to a specific embodiment, the hydrophilic monomer of chain (C) may typically have polymerizable functional groups of the acrylamide type and side chains consisting of ethylene oxide or propylene oxide chains, or based on N-isopropylacrylamide or N-vinylcaprolactam.

[0091] Hydrophobic Monomers. As non-limiting examples of hydrophobic monomers constituting the insoluble block that can be used according to the invention, mention may in particular be made of:

[0092] Vinyl aromatic monomers, such as styrene, α-methylstyrene, p-chloromethylstyrene, vinyltoluene, 2-methylstyrene, 4-methylstyrene, 2-(n-butyl)styrene, 4-(n-decyl)styrene or tert-butylstyrene;

[0093] A halogenated vinyl compound, such as a vinyl or vinylidene halide, for example a vinyl or vinylidene chloride or fluoride, corresponding to the formula R b R c C=CX 1 X 2 , Where: X 1 =F or Cl X 2 =H, F or Cl R b and R c Each of these independently represents: -H, Cl, F; or - alkyl, preferably chlorinated and / or fluorinated alkyl, more advantageously perchlorinated or perfluorinated alkyl;

[0094] α, β-ethylenically unsaturated mono- or di-carboxylic acids and C2-C 30Esters of alkanols, for example, methyl ethyl acrylate, ethyl (meth)acrylate, ethyl ethyl acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, tert-butyl ethyl acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 1,1,3,3-tetramethylbutyl (meth)acrylate, ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, tridecyl (meth)acrylate, propyl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecanyl (meth)acrylate, nonadecanyl (meth)acrylate, eicosyl (meth)acrylate, behenyl (meth)acrylate, lignoceryl (meth)acrylate, hexacosyl (meth)acrylate, triacontyl (meth)acrylate, palmitoleyl (meth)acrylate, oleyl (meth)acrylate, linoleyl (meth)acrylate, linoleyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, erucyl (meth)acrylate, and mixtures thereof;

[0095] Vinyl alcohol or allyl alcohol with C1-C 30 Esters of monocarboxylic acids, for example vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and mixtures thereof;

[0096] Ethylenically unsaturated nitriles such as acrylonitrile, methacrylonitrile and mixtures thereof;

[0097] α,β-ethylenically unsaturated mono- and dicarboxylic acids with C3-C 30 Esters of alkanediols, such as 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate, 3-hydroxy-2-ethylhexyl acrylate and 3-hydroxy-2-ethylhexyl methacrylate, and the like;

[0098] Primary amides of α,β-ethylenically unsaturated mono- and dicarboxylic acids with N-alkyl and N,N-dialkyl derivatives, such as N-propyl(meth)acrylamide, N-(n-butyl)(meth)acrylamide, N-(tert-butyl)(meth)acrylamide, N-butylphenylacrylamide, N-methyl-N-hexylacrylamide, N,N-dihexylacrylamide, hexyl(meth)acrylamide, N-(n-octyl)(meth)acrylamide, N-(1,1,3,3-tetramethylbutyl)(meth)acrylamide, N-ethylhexyl(meth)acrylamide, N-(n-nonyl)(meth)acrylamide, N-(n-decyl)(meth)acrylamide, N-(n-undecyl)(meth)acrylamide, N-tridecyl( (meth)acrylamide, N-pentadecyl(meth)acrylamide, N-hexadecyl(meth)acrylamide, N-heptadecyl(meth)acrylamide, N-nonadecyl(meth)acrylamide, N-eicosyl(meth)acrylamide, N-docosyl(meth)acrylamide, N-tetracosyl(meth)acrylamide, N-hexacosyl(meth)acrylamide, N-triacontyl(meth)acrylamide, N-palmitoleoyl(meth)acrylamide, N-oleyl(meth)acrylamide, N-linoleyl(meth)acrylamide, N-linolenyl(meth)acrylamide, N-stearyl(meth)acrylamide and N-lauryl(meth)acrylamide;

[0099] 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;

[0100] Esters of α,β-ethylenically unsaturated mono- and dicarboxylic acids with amino alcohols, for example N,N-dimethylaminocyclohexyl (meth)acrylate;

[0101] Amides of α,β-ethylenically unsaturated mono- and dicarboxylic acids with diamines containing at least one primary or secondary amino group, such as 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

[0102] Monoolefins (C2-C8) and non-aromatic hydrocarbons containing at least two conjugated double bonds, such as ethylene, propylene, isobutylene, isoprene, butadiene, and the like.

[0103] According to a preferred embodiment, the hydrophobic monomer used according to the present invention can be selected from:

[0104] C1-C 30 Alkyl and preferably C4-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 mustard acrylates and methacrylates (lauryl methacrylate in particular has proven to be particularly advantageous);

[0105] C1-C 30 Alkyl and preferably C4-C 22 Alkyl α,β-unsaturated amides, in particular alkyl acrylamides and alkyl methacrylamides, such as methyl-, ethyl-, butyl-, 2-ethylhexyl-, isooctyl-, lauryl-, isodecyl-, stearyl-, octyl-, myristyl-, pentadecyl-, cetyl-, oleyl- or erucyl acrylamide or -methacrylamide (lauryl methacrylamide in particular has proven to be particularly advantageous);

[0106] Vinyl or allyl alcohol esters of saturated carboxylic acids, such as vinyl or allyl acetates, propionates, tertiary carbonates or stearates;

[0107] α,β-unsaturated nitriles containing from 3 to 12 carbon atoms, such as acrylonitrile or methacrylonitrile; α-olefins and conjugated dienes; vinyl aromatic 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 above monomers.

[0108] According to an advantageous embodiment, in particular when the fluid (F) is a fracturing fluid, hydrophobic monomers can be used which are weakly bound to the chains (C). This makes it possible, if necessary, to remove the polymer introduced into the underground formation (the polymers of the invention generally have self-associating properties and tend to form gels which are difficult to remove, given their amphiphilic nature; under the influence of temperature and / or pH in particular, it is possible to cleave these hydrophobic monomers, if they are not too strongly bound to the polymer, which makes their removal from the fluid possible). Suitable hydrophobic monomers for this embodiment are in particular the abovementioned esters.

[0109] It should be noted that when other monomers are used, it is still possible to remove from the fluid, by techniques known per se, a "breaking agent" such as an oxidizing agent is added. The preceding embodiment makes it possible to dispense with the use of such a "breaking agent", which is reflected in particular in terms of cost reduction. In an embodiment, the breaking agent is selected from peroxides, persulfates, peracids, bromates, chlorates, chlorites, and combinations thereof.

[0110] According to a specific embodiment, the polymer can exhibit a molecular weight from about 10,000 g / mol to about 20,000,000 g / mol. In another embodiment, the molecular weight of the polymer is in the range of from about 100,000 g / mol to about 10,000,000 g / mol. In another embodiment, the molecular weight of the polymer is in the range of from about 500,000 g / mol to about 5,000,000 g / mol.

[0111] Free radical polymerization agent. Used in stage (E) of the process of the present invention or, where appropriate, in stage (E 0 ) is advantageously a compound carrying a thiocarbonylthio -S(C=S)- group. According to a specific embodiment, the control agent may carry several thiocarbonylthio groups. It may optionally be a polymer chain carrying such a group.

[0112] Thus, this control agent may, for example, correspond to the following formula (A):

[0113] wherein Z represents a hydrogen atom, a chlorine atom, an optionally substituted alkyl or optionally substituted aryl group, an optionally substituted heterocyclic ring, an optionally substituted alkylthio group, an optionally substituted arylthio group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, an optionally substituted amino group, an optionally substituted hydrazino group, an optionally substituted alkoxycarbonyl group, an optionally substituted aryloxycarbonyl group, an optionally substituted acyloxy group or a carboxyl group, an optionally substituted aroyloxy group, an optionally substituted carbamoyl group, a cyano group, a dialkyl- or diarylphosphonic acid group, a dialkyl-phosphinic acid group or a diaryl-phosphinic acid group, or a polymer chain, and R1 represents an optionally substituted alkyl, acyl, aryl, aralkyl, alkenyl or alkynyl group, a saturated or unsaturated aromatic optionally substituted carbocyclic or heterocyclic ring, or a polymer chain, which is preferably hydrophilic or water-dispersible when the reagent is used in stage (E).

[0114] The R or Z group, when substituted, may be substituted by an optionally substituted phenyl group, an optionally substituted aromatic group, a saturated or unsaturated carbocyclic ring, a saturated or unsaturated heterocyclic ring, or a group selected from the group consisting of an alkoxycarbonyl or aryloxycarbonyl group (-COOR), a carboxyl group (-COOH), an acyloxy group (-O2CR), a carbamoyl group (-CONR2), a cyano group (-CN), an alkylcarbonyl group, an alkylarylcarbonyl group, an arylcarbonyl group, an aralkylcarbonyl group, a phthalimido group, a maleimido group, a succinimidyl group, an amidino group, a guanidino group, a hydroxyl group (-OH), an amino group (-NR2), a halogen group, a perfluoroalkyl group C n F 2n+1 , allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl, groups exhibiting hydrophilicity or ionicity (such as alkali metal salts of carboxylic acids, alkali metal salts of sulfonic acids), polyoxyalkylene (PEO, PPO) chains, cationic substituents (quaternary ammonium salts), R represents an alkyl or aryl group, or a polymer chain.

[0115] For the control agent of formula (A) used in stage (E), the R1 group is generally preferably of hydrophilic nature. Advantageously, it is a water-soluble or water-dispersible polymer chain.

[0116] The R1 group may alternatively be amphiphilic, ie exhibit both hydrophilic and lipophilic properties. R1 is preferably not hydrophobic.

[0117] About the use in stage (E 0 ) of the control agent of formula (A), R1 may typically be a substituted or unsubstituted, preferably substituted alkyl. Nevertheless, for stage (E 0 ) of the formula (A) may contain other types of R1 groups, in particular rings or polymer chains.

[0118] Optionally substituted alkyl, acyl, aryl, aralkyl or alkynyl groups generally exhibit from 1 to 20 carbon atoms, preferably from 1 to 12 and more preferably from 1 to 9 carbon atoms. They may be straight-chain or branched. They may also be substituted by oxygen atoms (especially in the form of esters), sulfur atoms or nitrogen atoms.

[0119] Mention may in particular be made among the alkyl radicals of methyl, ethyl, propyl, butyl, pentyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, decyl or dodecyl.

[0120] Alkynyl groups are groups having 2 to 10 carbon atoms in total; they exhibit at least one acetylenic unsaturation, such as ethynyl.

[0121] An acyl group is a group which generally exhibits from 1 to 20 carbon atoms and a carbonyl group.

[0122] Among the aryl radicals, mention may especially be made of phenyl radicals optionally substituted, in particular by nitro or hydroxy functions.

[0123] Among the aralkyl radicals, mention may especially be made of benzyl or phenethyl radicals, in particular optionally substituted by a nitro or hydroxy function.

[0124] When R1 or Z is a polymer chain, the polymer chain may be generated by free radical or ionic polymerization or by self-condensation.

[0125] Advantageously, a compound with a xanthate -S(C=S)O-, trithiocarbonate, dithiocarbamate or dithiocarbazinate functional group, for example a compound with an O-ethylxanthate functional group of the formula -S(C=S)OCH2CH3, is used as a control agent in stage (E) and also in stage (E 0 ) (where appropriate).

[0126] When the phase (E 0 ), it is particularly advantageous to use as control agent in this stage a compound selected from the group consisting of xanthates, trithiocarbonates, dithiocarbamates and dithiocarbazinates. Xanthates have proven to be very particularly advantageous, in particular those with an O-ethylxanthate-S(C=S)OCH2CH3 functional group, such as O-ethyl-S-(1-(methoxycarbonyl)ethyl)xanthate (CH3CH(CO2CH3))S(C=S)OEt. Stage (E 0 ) is dibenzyl trithiocarbonate having the formula PhCH2S(C=S)SCH2Ph ​​(wherein Ph=phenyl).

[0127] It is proved that by using the above control agent in step (E 0 ) are particularly advantageous for carrying out stage (E).

[0128] Phase (E) and (E 0 ) is preferably water-soluble or water-dispersible when used in stage (E). Apart from this preference, any free radical polymerization initiator (source of free radicals) known per se and suitable for the conditions selected for these stages can be used in stage (E) and in stage (E) of the process of the invention. 0 )middle.

[0129] Therefore, the free radical polymerization initiator used according to the present invention can be selected, for example, from the initiators conventionally used for free radical polymerization. It can be, for example, one of the following initiators:

[0130] Hydrogen peroxide, such as tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-butyl peroxyoctanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxyisobutyrate, lauroyl peroxide, tert-amyl peroxypivalate, tert-butyl peroxypivalate, diisopropylbenzene peroxide, benzoyl peroxide, potassium persulfate or ammonium persulfate,

[0131] Azo compounds, such as: 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-butyronitrile), 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'-dimethyleneisobutylamidine) 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,

[0132] A redox system comprising a combination of:

[0133] Mixtures of hydrogen peroxide, alkyl peroxides, peresters, percarbonates and the like with any iron salt, trivalent titanium salt, zinc formaldehyde sulfoxylate or sodium formaldehyde sulfoxylate, and reducing sugars,

[0134] Alkali metal or ammonium persulfates, perborates, or perchlorates in combination with an alkali metal bisulfite (such as sodium metabisulfite) and a reducing sugar, and

[0135] Alkali metal persulfates in combination with an arylphosphinic acid (such as benzenephosphinic acid and the like) and a reducing sugar.

[0136] Typically, the amount of the initiator to be used is preferably determined so that the amount of free radicals generated relative to the amount of the control agent or transfer agent is at most 50 mol % and preferably at most 20 mol %.

[0137] Very particularly, in stage (E), it has generally proven advantageous to use free radical initiators of the redox type, which in particular exhibit the advantage of not requiring heating of the reaction medium (non-thermal initiation) and whose inventors have now furthermore found that free radical initiators of the redox type are suitable for the micellar polymerization of stage (E).

[0138] Thus, the free radical polymerization initiator used in stage (E) may typically be a redox initiator, typically not requiring heating for its thermal initiation. It is typically a mixture of at least one oxidizing agent and at least one reducing agent.

[0139] The oxidizing agent present in this redox system is preferably a water-soluble agent. Such an oxidizing agent can be selected, for example, from peroxides such as hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-butyl peroxyoctanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxyisobutyrate, lauroyl peroxide, tert-amyl peroxypivalate, tert-butyl peroxypivalate, diisopropylbenzene peroxide, benzoyl peroxide, sodium persulfate, potassium persulfate, ammonium persulfate or also potassium bromate.

[0140] The reducing agent present in the redox system is also preferably a water-soluble agent. Such reducing agents can typically be selected from sodium formaldehyde sulfoxylate (especially in the form of its dihydrate, known under the name Rongalite, or in the form of anhydrides), ascorbic acid, isoascorbic acid, sulfites, bisulfites or pyrosulfites (especially alkali metal sulfites, bisulfites or pyrosulfites), nitrilotripropionamide and tertiary amines and ethanolamines (preferably water-soluble).

[0141] Possible redox systems include combinations of:

[0142] A mixture of a water-soluble persulfate and a water-soluble tertiary amine,

[0143] A mixture of a water-soluble bromate (e.g., an alkali metal bromate) and a water-soluble sulfite (e.g., an alkali metal sulfite),

[0144] Mixtures of hydrogen peroxide, alkyl peroxides, peresters, percarbonates and the like with any iron salt, trivalent titanium salt, zinc formaldehyde sulfoxylate or sodium formaldehyde sulfoxylate, and reducing sugars,

[0145] Alkali metal or ammonium persulfates, perborates, or perchlorates in combination with an alkali metal bisulfite (such as sodium metabisulfite) and a reducing sugar, and

[0146] Alkali metal persulfates in combination with an arylphosphinic acid (such as benzenephosphinic acid and the like) and a reducing sugar.

[0147] An advantageous redox system comprises (and preferably consists of) a combination of ammonium persulfate and sodium formaldehyde sulfoxylate.

[0148] In general, and in particular in the case of redox systems of the ammonium persulfate / sodium formaldehyde sulfoxylate type, it has proven to be preferred that the reaction medium of stage (E) is free of copper. In the case of the presence of copper, it is generally desirable to add a copper complexing agent (such as EDTA) in an amount capable of masking the presence of this copper.

[0149] Whatever the nature of the initiator used, stage (E 0 ) can be carried out in any suitable physical form (for example as a solution in water or in a solvent such as an alcohol or THF, an emulsion in water ("latex" process) or in bulk form) while controlling the temperature and / or pH as appropriate so as to render the entity liquid and / or soluble or insoluble.

[0150] After carrying out stage (E), polymers functionalized with transfer groups (active polymers) are obtained, given the specific use of control agents. This active characteristic makes it possible, if desired, to use these polymers in subsequent polymerization reactions according to techniques well known per se. Alternatively, if desired, it is possible to deactivate or destroy the transfer groups according to means known per se, for example by hydrolysis, ozonolysis or reaction with amines. Thus, according to a particular embodiment, the process of the invention may comprise, after stage (E), a stage (E1) of hydrolysis, ozonolysis or reaction with amines, which stage (E1) is able to deactivate and / or destroy all or part of the transfer groups present on the polymer prepared in stage (E).

[0151] Surfactants. To prepare the micellar solution of the hydrophobic monomer used in stage (E), any suitable surfactant may be used in a non-limiting manner; surfactants selected from the following list may be used, for example:

[0152] Anionic surfactants may be selected from:

[0153] Alkyl ester sulfonate (e.g., alkyl ester sulfonate having the formula R—CH(SO3M)—CH2COOR′) or alkyl ester sulfate (e.g., alkyl ester sulfate having the formula R—CH(OSO3M)—CH2COOR′), wherein R represents a C8-C 20 And preferably C 10 -C 16 alkyl, R' represents a C1-C6 and preferably a C1-C3 alkyl, and M represents an alkali metal cation (for example a sodium cation or an ammonium cation). Very particular mention may be made of methyl ester sulfonates, in which the R group is C 14 -C 16 Group;

[0154] Alkylbenzene sulfonates (more particularly C9-C 20 Alkylbenzene sulfonates), primary or secondary alkyl sulfonates (especially C8-C22 Alkyl sulfonates), or alkyl propylene glycol sulfonates;

[0155] Alkyl sulfates, for example those of the formula ROSO3M, wherein R represents C 10 -C 24 And preferably C 12 -C 20 alkyl or hydroxyalkyl, and M represents a cation having the same definition as above;

[0156] Alkyl ether sulfates, for example having the formula RO(OA) n Alkyl ether sulfates of SO3M, wherein R represents C 10 -C 24 And preferably C 12 -C 20 alkyl or hydroxyalkyl, OA represents an ethoxylated and / or propoxylated group, M represents a cation having the same definition as above, and n generally varies from 1 to 4, such as, for example, lauryl ether sulfate wherein n=2;

[0157] Alkylamide sulfates (e.g., alkylamide sulfates having the formula RCONHR'OSO3M, wherein R represents a C2-C 22 And preferably C6-C 20 alkyl, R' represents a C2-C3 alkyl group, and M represents a cation having the same definition as above) and also their polyalkoxylated (ethoxylated and / or propoxylated) derivatives (alkylamide ether sulfates);

[0158] Saturated or unsaturated fatty acids (e.g. C8-C 24 And preferably C 14 -C 20 acid) and an alkaline earth metal cation, N-acyl-N-alkyl taurates, alkyl isethionates, alkyl succinamates and alkyl sulfosuccinates, alkyl glutamates, mono- or diesters of sulfosuccinic acid, N-acyl sarcosinates or salts of polyethoxyformates;

[0159] Monoester and diester phosphates, for example those having the formula: (RO) x -P(=O)(OM) x , in which R represents an optionally polyalkoxylated alkyl, alkaryl, arylalkyl or aryl group, x and x′ are equal to 1 or 2, with the proviso that the sum of x and x′ is equal to 3, and M represents an alkaline earth metal cation;

[0160] The nonionic surfactant may be selected from:

[0161] Alkoxylated fatty alcohols, such as laureth-2, laureth-4, laureth-7 or oleth-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 resulting from the condensation of ethylene oxide with a hydrophobic compound resulting from the condensation of propylene oxide with propylene glycol (such as the Pluronic products sold by BASF), products resulting from the condensation of ethylene oxide with a compound resulting from the condensation of propylene oxide with ethylenediamine (such as the Tetronic products sold by BASF), alkyl polyglycosides (such as those described in U.S. Pat. No. 4,565,647), or alkyl glucosides; or fatty acid amides, such as C8-C 20 Fatty acid amides, in particular fatty acid monoalkanolamides, such as cocamide MEA or cocamide MIPA;

[0162] Amphoteric surfactants (true zwitterionic entities comprising an ionic group and a potentially ionic group of opposite charge, or zwitterionic entities comprising two oppositely charged groups simultaneously) can be:

[0163] Betaines, in general, in particular carboxybetaines, for example lauryl betaine (Mirataine BB from Rhodia) or octyl betaine or cocobetaine (Mirataine BB-FLA from Rhodia); amidoalkylbetaines, such as cocoamidopropyl betaine (CAPB) (Mirataine BDJ from Rhodia or Mirataine BET C-30 from Rhodia);

[0164] Sulfobetaine or sultaine, such as cocamidopropyl hydroxysultaine (Mirataine CBS from Rhodia);

[0165] Alkylamphoacetates and alkylamphodiacetates, such as, for example, those containing cocoyl or lauryl chains (especially Miranol C2M Conc. NP, C32, L32 from Rhodia);

[0166] Alkylamphopropionate or alkylamphodipropionate (Miranol C2M SF);

[0167] Alkylamphohydroxypropyl sulfobetaine (Miranol CS);

[0168] Alkylamine oxides, for example laurylamine oxide (INCI);

[0169] The cationic surfactant may optionally be a polyethoxylated primary, secondary or tertiary fatty amine salt, a quaternary ammonium salt such as a tetraalkylammonium, alkylamidoalkylammonium, trialkylbenzylammonium, trialkylhydroxyalkylammonium or alkylpyridinium chloride or bromide, an imidazoline derivative or an amine oxide having a cationic nature. Examples of cationic surfactants are cetyltrimethylammonium chloride or bromide (INCI);

[0170] The surfactant used according to the invention may be a block copolymer comprising at least one hydrophilic block and at least one hydrophobic block different from the hydrophilic block, advantageously obtained according to a polymerization process in which:

[0171] (a0) mixing together in an aqueous phase at least one hydrophilic (respectively hydrophobic) monomer, at least one free radical source and at least one -S(C=S)- type free radical polymerization controller;

[0172] (a1) contacting the polymer obtained at the end of stage (a0) with at least one hydrophobic (respectively hydrophilic) monomer different from the monomer used in stage (a0) and with at least one source of free radicals; thereby obtaining a diblock copolymer.

[0173] Polymers of the triblock type or polymers comprising more blocks can optionally be obtained by carrying out, after stage (a1), a stage (a2), in which the polymer obtained at the end of stage (a1) is brought into contact with at least one monomer different from the monomer used in stage (a1) and with at least one source of free radicals; and more generally, carrying out (n+1) stages of the type described above, stages (a1) and (a2), and n is an integer typically ranging from 1 to 3, wherein in each stage (a1) in which n≥1 n ), so that in stage (a n-1 The polymer obtained at the end of stage (a) is different from at least one n-1 ) and at least one free radical source. For example, copolymers of the type described in WO03068827, WO03068848 and WO 2005 / 021612 can be used according to the invention.

[0174] In an embodiment, one or more polymers of the present disclosure are present in an aqueous composition. In another embodiment, one or more polymers of the present disclosure are present in the aqueous composition in an amount ranging from about 0.001 wt% to about 10 wt% based on the total weight of the aqueous composition.

[0175] In an embodiment, the hydration rate of the powder polymer of the present disclosure increases under low shear mixing (e.g., less than 10,000rpm). In an embodiment, before being added to water, the dry polymer is combined with mineral oil. In another embodiment, before being added to water, the dry polymer is pre-treated or post-treated with a solvent (e.g., a mutually soluble solvent). In yet another embodiment, a hydrating surfactant is combined during polymer manufacture. In another embodiment, the example of a hydrating surfactant includes but is not limited to EO / PO copolymers, such as ANTAROX 31R1, ANTAROX LAEP 16, and ANTAROXBL 225. In another embodiment, the example of a solvent includes but is not limited to ethylene glycol, propylene glycol, ethylene glycol monobutyl ether (EGMBE), and "green" solvents such as RHODISOLV DIB.

[0176] The present disclosure also provides methods for utilizing the polymers and related compositions of the present invention.

[0177] In an embodiment, a method for fracturing a subterranean formation comprises the step of injecting an aqueous fracturing fluid into at least a portion of the subterranean formation at a pressure sufficient to fracture the formation, wherein the fracturing fluid comprises a polymer of the present disclosure. In an embodiment, the polymer comprises: at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of acrylates, acrylates, acrylamides, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonate, and combinations thereof.

[0178] In an embodiment, the polymer is in the form of a powder having a particle size from about 5 μm to about 400 μm prior to injecting the aqueous fracturing fluid. In an embodiment, the polymer is present in an amount ranging from about 0.001 wt% to about 10 wt% based on the total weight of the fracturing fluid.

[0179] In an embodiment, the fracturing fluid suspends the particles at a temperature from about 68° F. to about 350° F. In another embodiment, the fracturing fluid suspends the particles at a temperature from about 250° F. to about 350° F. In another embodiment, the fracturing fluid suspends the particles at a temperature from about 300° F. to about 350° F.

[0180] In an embodiment, the fracturing fluid further comprises a surfactant. In an embodiment, the surfactant is selected from, but not limited to, tridecyl alcohol ethoxylate and EO / PO block copolymers (e.g., ANTAROX 31R1, ANTAROX LAEP 16, ANTAROX BL 225). In an embodiment, the surfactant is present in an amount ranging from about 0.01 wt % to about 10 wt % based on the weight of the polymer.

[0181] In an embodiment, the fracturing fluid further comprises a proppant. In an embodiment, the proppant is used in an amount ranging from about 20 wt % to about 60 wt % based on the total weight of the fracturing fluid.

[0182] In an embodiment, the fracturing fluid further comprises a clay stabilizer. In an embodiment, the clay stabilizer is selected from choline chloride, potassium chloride, ammonium chloride, sodium chloride, calcium chloride, and combinations thereof. In an embodiment, the clay stabilizer is present in an amount ranging from about 0.01 wt % to about 30 wt % based on the total weight of the fracturing fluid.

[0183] In embodiments, the method further comprises the step of injecting a fracking agent into at least a portion of the subterranean formation.

[0184] In an embodiment, the fracturing fluid is selected from fresh water, seawater, brine, brackish water, produced water, reclaimed water, industrial wastewater, wastewater associated with oil production, and combinations thereof.

[0185] In another embodiment, a fracturing fluid is provided, comprising a polymer at a mass concentration of from about 0.1 ppt 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 to about 12 lb / gal based on the total volume of the composition, and a rupturing agent present at a mass concentration of from 0 ppt to about 20 ppt based on the total volume of the composition.

[0186] Also provided is a method of acidizing a formation penetrated by a wellbore, the method comprising the steps of injecting into the wellbore a treatment fluid comprising an aqueous solution of a polymer according to the present disclosure and an acid at a pressure below the formation fracturing pressure, and allowing the treatment fluid to acidify the formation and / or self-divert into the formation. As used herein, the term "self-diverting" refers to a composition that increases in viscosity as it stimulates the formation and, in doing so, diverts any remaining acid to lower permeability zones in the formation.

[0187] In an embodiment, a method for acidizing a subterranean formation penetrated by a wellbore comprises the following steps: (a) injecting a treatment fluid into the wellbore at a pressure below the fracturing pressure of the subterranean formation, the treatment fluid having a first viscosity and comprising an aqueous solution of an acid and a polymer, the polymer comprising: at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylate, and pentadecyl (meth)acrylate. Alkyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of acrylates, acrylates, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salts, and combinations thereof; (b) forming at least one void in the underground formation with the treatment fluid; and (c) allowing the treatment fluid to reach a second viscosity greater than the first viscosity.

[0188] In embodiments, the method further comprises forming at least one void in the subterranean formation with the treatment fluid after the fluid has reached the second viscosity.

[0189] In another embodiment, the method further comprises reducing the viscosity of the treatment fluid to a viscosity less than the second viscosity.

[0190] Optionally, the treatment fluid further comprises one or more additives. In an embodiment, the fluid comprises one or more additives selected from corrosion inhibitors, iron control agents, clay stabilizers, scale inhibitors, miscible solvents, non-emulsifiers, anti-slugging agents, and combinations thereof. In an embodiment, the corrosion inhibitor is selected from alcohols (e.g., acetylenes); cationic agents (e.g., quaternary ammonium salts, imidazolines, and alkyl pyridines); and nonionic agents (e.g., alcohol ethoxylates).

[0191] Suitable aqueous solutions of acids include aqueous solutions of acids used in the acidification process that are compatible with the polymers of the present disclosure. In embodiments, the aqueous solution of the acid is selected from hydrochloric acid, hydrofluoric acid, formic acid, acetic acid, sulfamic acid, and combinations thereof. In embodiments, the treatment fluid comprises an acid in an amount up to 30 wt % based on the total weight of the fluid.

[0192] The compositions disclosed herein can also be used to limit or prevent pump damage during surface transport of proppant. During surface transport, proppant (e.g., sand) may settle, causing pump damage. Maintaining sand production is necessary to produce oil at an economical rate. If mechanical failure occurs or the wellbore or pump is clogged with sand, well repair is required. Take out the tubing, and before reinstalling, use a mechanical mud pump, a surface pump truck (pump-to-surface truck), a jet pump, a foam treatment or other technology to thoroughly remove the sand in the well. Restart oil production after the pump is reinstalled.

[0193] In an embodiment, a method for suspending and transporting a proppant on a surface (e.g., above ground) includes the steps of mixing an aqueous fluid and a proppant and transporting the combination by at least one pump, wherein the fluid comprises a polymer comprising at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamides, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salts, and combinations thereof.

[0194] The compositions disclosed herein can also be used in gravel packing methods. Some oil and gas wells are completed in unconsolidated formations that contain loose fines and sand. When fluids are produced from these wells, the loose fines and sand may migrate with the produced fluids and may damage equipment, such as electric submersible pumps (ESPs) and other systems. For this reason, the completion of these wells may require sand screens for sand control. For hydrocarbon wells, especially horizontal wells, the completion has a screen section with a perforated inner tube and an overlying screen section. The purpose of the screen is to prevent particulate matter from flowing into the interior of the production pipe.

[0195] A gravel packing operation is a method of reducing the influx of particulate matter before it reaches the sand screen. In a gravel packing operation, gravel (e.g., sand) is packed in the wellbore annulus around the sand screen. Gravel is a particulate material of a specific size, such as graded sand or proppant. When packed in the wellbore annulus around the sand screen, the packed gravel acts as a filter to prevent any fines and sand from the formation from migrating into the sand screen with the produced fluid. The packed gravel also provides stabilizing force to the producing formation, which can prevent the wellbore annulus from collapsing. Typically, gravel packing is used to stabilize the formation and maintain well productivity. Gravel packing is applied in conjunction with hydraulic fracturing, but at much lower pressures.

[0196] In an embodiment, a gravel packing method includes the steps of conveying a fluid through at least one pump and underground gravel packing, wherein the fluid comprises a polymer comprising at least one hydrophobic monomer selected from the group consisting of n-hexyl (meth)acrylate, n-octyl (meth)acrylate, octyl (meth)acrylamide, lauryl (meth)acrylate, lauryl (meth)acrylamide, myristyl (meth)acrylate, myristyl (meth)acrylamide, pentadecyl (meth)acrylate, pentadecyl (meth)acrylamide, cetyl (meth)acrylate, cetyl (meth)acrylamide, oleyl (meth)acrylate, oleyl (meth)acrylamide, mustard (meth)acrylate, mustard (meth)acrylamide, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamides, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salts, and combinations thereof.

[0197] While specific embodiments have been discussed, the description is illustrative only and not restrictive. Many variations of the present disclosure will become apparent to those skilled in the art upon reviewing this description.

[0198] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this specification belongs.

[0199] As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0200] As used herein, and unless otherwise indicated, the term "about" or "approximately" means an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or "approximately" means within 1, 2, 3, or 4 standard deviations. In certain 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 a given value or range.

[0201] In addition, it should be understood that any numerical range listed herein is intended to include all subranges contained therein. For example, a range of "1 to 10" is intended to include and include all subranges between the listed minimum value of 1 and the listed maximum value of 10; that is, having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Because these disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless otherwise clearly indicated, the various numerical ranges specified in this application are approximate.

[0202] The present disclosure will be further illustrated by reference to the following examples. The following examples are illustrative only and are not intended to be limiting.

[0203] Example 1 - Synthesis of associative polymer (PPS) (polyacrylamide / AMPS / LMAM 2,000,000 g / mol).

[0204] 29.3 g of 30% SDS solution, 89.03 g of distilled water and 1.66 g of lauryl methacrylamide (LMAM) monomer are introduced into a 500 ml round-bottom flask at room temperature (20° C.). The mixture is stirred for 6 hours using a magnetic stirring bar until a clear micellar solution is obtained. 32.9 g of the micellar solution thus prepared, 7.53 g of water, 40.7 g of acrylamide (50% by weight in water), 32 g of AMPS (51% by weight in water), 0.454 g of Rhodixan A1 (1.0% by weight in ethanol) and 6.00 g of ammonium persulfate (0.67% by weight in water) are introduced into a 250 ml round-bottom flask at room temperature (20° C.). The mixture is degassed by sparging with nitrogen for 20 minutes. 1.5 g of sodium sulfoxylate formaldehyde in the form of a 0.13% by weight aqueous solution are added to the medium in a single portion. The mixture is degassed by sparging with nitrogen for 15 minutes. The polymerization is then maintained under stirring for 16 hours at room temperature (20° C.).

[0205] Example 2 - Hydrated viscosity.

[0206] The PPS polymer powder prepared in Example 1 was added to 0.3% choline chloride in a Waring blender at high shear rate (10,000 RPM) for 3 minutes and then centrifuged to remove trapped bubbles. Viscosity was measured using Ofite 1100. Typical viscosity of 0.3% polymer is 200-1000 cps at room temperature (25°C) and 100 s-1.

[0207] Example 3 - Viscosity testing for proppant suspension.

[0208] The PPS polymer powder prepared using Example 1 was added to 0.3% choline chloride in a blender at a shear rate (10,000 RPM) for 3 minutes and then centrifuged to remove trapped bubbles. Rheological testing was performed immediately after centrifugation at 400 psi pressure using an OFITE 1100 viscometer. Once the temperature reached the target, 100, 75, 50 and 25 s -1 The temperature was increased incrementally from 80°F to 425°F. Generally, polymer solutions exhibiting viscosities above 50 cps are able to suspend sand.

[0209] Example 4 - Sand Suspension Test.

[0210] Sand settling tests were performed in fresh water with 0.3% polymer powder (PPS) from Example 1. 400 g of fluid and 250 g of sand were mixed thoroughly and then placed in an oven at 180° F. After 3 hours and 24 hours, the sand was still well suspended.

[0211] For comparison, 0.42% guar powder was dispersed in fresh water. 400 g of guar fluid and 250 g of sand were mixed and heated to 65°C. Sand separation was measured at 1 hour, 3 hours and 24 hours. After 3 hours at 65°C, there was about 50% sand settling for the guar solution compared to no sand separation observed in the 0.3% PPS polymer solution. After 24 hours at 65°C, there was almost complete sand settling for the guar compared to no sand settling for the PPS polymer solution.

[0212] Example 5 - Viscosity reduction using a rupture agent.

[0213] 0.1% ammonium persulfate (APS) was added to the 0.3% PPS polymer solution prepared in Example 3, which was then blended and centrifuged. Rheological testing was performed immediately after centrifugation using an OFITE 1100 viscometer at 400 psi pressure at 250°F and a shear rate of 100 s-1. The viscosity dropped significantly to close to 0 cps.

[0214] The disclosed subject matter has been described with reference to specific details of specific embodiments thereof. Such details are not intended to be considered as limitations on the scope of the disclosed subject matter, except to the extent they are included in the appended claims.

[0215] Therefore, the exemplary embodiments described herein are well adapted to achieve the objects and advantages mentioned and those inherent therein. The specific embodiments disclosed above are merely illustrative, as the exemplary embodiments described herein can be modified and practiced in different but equivalent ways that are obvious to those skilled in the art who benefit from the teachings herein. In addition, except as described in the claims below, it is not intended to limit the details of the structure or design shown herein. It is therefore obvious that the specific illustrative embodiments disclosed above can be changed, combined or modified and all such changes are considered to be within the scope and spirit of the exemplary embodiments described herein. The exemplary embodiments described herein illustratively disclosed herein can be appropriately practiced in the absence of any elements not specifically disclosed herein and / or any optional elements disclosed herein. Although the compositions and methods are described in terms of "comprising", "containing" or "including" various components or steps, these compositions and methods can also be "essentially composed of" or "composed of": these various components, substances and steps. As used herein, the term "consisting essentially of" should be understood to mean including the listed components, materials, or steps and such additional components, materials, or steps that do not substantially affect the basic and novel characteristics of the composition or method. In some embodiments, a composition "consisting essentially of" according to an embodiment of the present disclosure includes the listed components or materials, excluding any additional components or materials that change the basic and novel characteristics of the composition. If there is any conflict in the use of a word or term in this specification and in one or more patents or other documents that may be incorporated by reference into this application, the definition consistent with this specification shall be adopted.

Claims

1. A method for fracturing a subterranean formation, the method comprising the step of injecting an aqueous fracturing fluid into at least a portion of the subterranean formation at a pressure sufficient to fracture the formation, wherein the fracturing fluid comprises a polymer comprising: At least one hydrophobic monomer selected from the group consisting of: n-Hexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, oleyl (meth)acrylate, mustard (meth)acrylate, vinyl acetate, vinyl propionate, vinyl tert-carbonate, vinyl stearate, allyl acetate, allyl propionate, allyl tert-carbonate, allyl stearate, and combinations thereof; and At least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamides, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof.

2. The method of claim 1, wherein: The polymer comprises hydrophilic monomers in a total amount of from about 50 wt % to about 99.9 wt % of the polymer.

3. The method of claim 1, wherein: The polymer comprises hydrophobic monomers in a total amount of from about 0.01 wt % to about 50 wt % of the polymer.

4. The method of claim 1, wherein: Prior to injecting the aqueous fracturing fluid, the polymer is in the form of a powder comprising a particle size ranging from about 5 μm to about 400 μm.

5. The method of claim 1, wherein: The polymer contains thiocarbonylthio functional groups at the terminal positions.

6. The method of claim 1, wherein: The polymer comprises a molecular weight of from about 10,000 to about 20,000,000.

7. The method of claim 1, wherein: The aqueous fracturing fluid includes the polymer in an amount ranging from about 0.001 wt % to about 10 wt % based on the total weight of the aqueous fracturing fluid.

8. The method of claim 1, wherein: The aqueous fracturing fluid further comprises a surfactant.

9. The method of claim 8, wherein: The surfactant is present in an amount ranging from about 0.001 wt % to about 50 wt % based on the weight of the polymer.

10. The method of claim 1, wherein: The aqueous fracturing fluid further comprises a proppant.

11. The method of claim 10, wherein: The proppant is present in an amount ranging from about 20 wt % to about 60 wt % based on the total weight of the aqueous fracturing fluid.

12. The method of claim 10, wherein: The aqueous fracturing fluid suspends the proppant at a temperature of about 68°F to about 350°F.

13. The method of claim 1, wherein: The aqueous fracturing fluid is selected from the group consisting of fresh water, seawater, brine, brackish water, produced water, reclaimed water, industrial wastewater, wastewater associated with oil production, and combinations thereof.

14. An aqueous composition comprising water and a polymer, the polymer comprising: At least one hydrophobic monomer selected from the group consisting of: n-Hexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, oleyl (meth)acrylate, mustard (meth)acrylate, vinyl acetate, vinyl propionate, vinyl tert-carbonate, vinyl stearate, allyl acetate, allyl propionate, allyl tert-carbonate, allyl stearate, and combinations thereof; and At least one hydrophilic monomer selected from the group consisting of acrylates, acrylate salts, acrylamides, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid salts, and combinations thereof, wherein the composition exhibits a particle suspension time of at least 1 hour.

15. The aqueous composition according to claim 14, wherein The composition exhibits a particle suspension time of at least 2 hours.

16. The aqueous composition according to claim 14, wherein The polymer is in the form of a powder comprising a particle size from about 5 μm to about 400 μm.

17. The aqueous composition according to claim 14, wherein The polymer contains thiocarbonylthio functional groups at the terminal positions.

18. The aqueous composition according to claim 14, wherein The polymer comprises a molecular weight of from about 10,000 g / mol to about 20,000,000 g / mol.

19. A powder composition comprising polymer particles having a particle size of from about 5 μm to about 400 μm and a molecular weight ranging from about 10,000 to 20,000,000, wherein the polymer comprises acrylamide and 2-acrylamido-2-methylpropanesulfonic acid monomers and at least one hydrophobic monomer selected from the group consisting of: n-Hexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, oleyl (meth)acrylate, mustard (meth)acrylate, vinyl acetate, vinyl propionate, vinyl tert-carbonate, vinyl stearate, allyl acetate, allyl propionate, allyl tert-carbonate, allyl stearate, and combinations thereof.

20. The powder composition according to claim 19, wherein The hydrophobic monomer is lauryl (meth)acrylate.

21. A method for suspending and transporting a proppant, the method comprising mixing an aqueous fluid and a proppant and transporting the combination by at least one pump, wherein the fluid comprises a polymer in an amount ranging from about 0.001 wt % to about 10 wt % based on the total weight of the combination, and the polymer comprises at least one hydrophobic monomer selected from the group consisting of: n-Hexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, oleyl (meth)acrylate, mustard (meth)acrylate, vinyl acetate, vinyl propionate, vinyl tertiary carbonate, vinyl stearate, allyl acetate, allyl propionate, allyl tertiary carbonate, allyl stearate, and combinations thereof; and at least one hydrophilic monomer selected from the group consisting of acrylates, acrylates, acrylamides, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-2-methylpropane sulfonates, and combinations thereof.

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