Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/62—Compositions for forming crevices or fractures
  • C09K8/66—Compositions based on water or polar solvents
  • C09K8/68—Compositions based on water or polar solvents containing organic compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/84—Compositions based on water or polar solvents
  • C09K8/86—Compositions based on water or polar solvents containing organic compounds
  • C09K8/88—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
  • C09K2208/28—Friction or drag reducing additives

Definitions

• TITLE WATER SOLUBLE POLYMER DISPERSION FOR HYDRAULIC FRACTURING
• the invention relates to an injection fluid for hydraulic fracturing comprising at least one synthetic water-soluble polymer, said fluid being a dispersion prepared by diluting a previously distilled inverse emulsion of said polymer with brine.
• the invention also relates to a method for the hydraulic fracturing of underground reservoirs of unconventional oil and gas using said injection fluid.
• Production techniques have in fact evolved from vertical wells to horizontal wells, reducing the number of production wells required and their footprint in ground and allowing better coverage of the volume of the tank to recover as much gas or oil as possible.
• the permeabilities are insufficient for the hydrocarbon to migrate easily from the source rock to the well, and thus allow the gas or oil to be produced economically and in quantity. It is therefore necessary to increase the permeability and the production surfaces by stimulation operations and in particular by hydraulic fracturing of the rock in contact with the well.
• Hydraulic fracturing aims to create additional permeability and generate larger gas or oil production surfaces. Indeed, the low permeability, the natural barriers of compact layers and the waterproofing by drilling operations strongly limit production. The gas or oil contained in the unconventional reservoir cannot easily migrate from the rock to the well without stimulation.
• a propping agent for example sand, plastic materials or calibrated ceramics
• Water alone is not sufficient to achieve good proppant placement efficiency due to its low viscosity. This limits its ability to hold the proppant in place in the fractures.
• fracturing fluids containing viscosifying compounds have been developed.
• a compound is said to be viscosifying when it increases the viscosity of the solutions in which it is dissolved.
• the compound In addition to having viscosifying properties, the compound must have a particular rheological profile. Indeed, the compound must be able to generate a low viscosity so as not to interfere with the transport and pumping of the fluid containing the proppant during the strong shears undergone during the injection of the fracturing fluid. Once injected, this same compound must be able to generate sufficient viscosity when the shear decreases to support the proppant in order to maintain it in the fractures.
• Fracturing fluids generally include a polymer which must therefore provide shear-thinning properties to the solution in order to have a relatively low viscosity during injection (at high shear) and a high viscosity in order to maintain the proppant in suspension at the level of the fracture when the shear decreases.
• viscosifying compounds of aqueous solutions belonging to the state of the art, mention may be made of natural substances such as guar gums and their derivatives such as hydroxypropylguar (H PG), or carboxymethylhydroxypropyl guar (CMHPG); cellulose derivatives such as carboxymethyl cellulose or hydroxyethyl cellulose.
• H PG hydroxypropylguar
• CMHPG carboxymethylhydroxypropyl guar
• cellulose derivatives such as carboxymethyl cellulose or hydroxyethyl cellulose.
• petrochemical compounds can have viscosifying properties. Mention may be made of synthetic polymers. Poly(meth)acrylamides, optionally partially hydrolyzed, and poly(meth)acrylates and their copolymers are particularly known. These polymers develop viscosity thanks to their molar mass and the inter-chain ionic repulsions. These polymers are described in patents GB951 147, US3727689, US3841402 or even US3938594. The mechanism governing viscosity is related to an increase in hydrodynamic volume through intra-chain repulsions, inter-chain entanglements, etc.
• these polymers do not develop strong entanglements and repulsions, which results in a strong reduction in their viscosifying power, especially after having undergone the shearing of the step pumping. Furthermore, these polymers generally do not have sufficient viscoelastic properties to support the proppant in the fracture. The dosage of these polymers must be increased to levels too high to achieve the suspending properties of the proppant. However, the necessary dosage levels are not economically viable.
• the polymers used to have viscosifying properties can advantageously also be friction reducers making it possible to reduce the pressure drop in a turbulent medium and greatly increase the flow rate at identical power and pipe diameter.
• Synthetic polymers based on 2-acrylamido-2-methylpropane sulfonic acid and/or its salts have interesting friction reduction properties in aqueous solution. These polymers are also known for their resistance to shear and thermal degradation, especially in salt solutions. However, obtaining very high molecular weight polymer based on 2-acrylamido-2-methylpropane sulfonic acid is difficult, not to mention that these polymers have solubility problems when their molecular weight increases. However, to have an optimal phenomenon of friction reduction and a strong generation of viscosity, it is essential that the polymer is dissolved quickly in particular in saline solution and that it has a very high molecular weight.
• the preferred physical form of these polymers is the powder because it makes it possible to have a high percentage by weight of active material.
• the physical powder form of these polymers can be obtained by drying, thermo-drying, spraying (spray drying in English) and drum drying (drum drying in English).
• spraying spraying in English
• drum drying drum drying in English.
• suitable equipment for example a wet grinding unit for powders such as a PSU (Polymer Slicing Unit).
• Inverse polymer emulsions are also interesting, but they require rigorous optimization of their formulation so that their inversion in an aqueous medium is the fastest and their stability (during storage and transport) is guaranteed (especially during freeze/thaw cycles) .
• the Applicant has found and developed an injection fluid for hydraulic fracturing which makes it possible to have high friction reduction and viscosifying effects.
• This injection fluid is in the form of a water-soluble polymer dispersion and it is prepared by diluting a previously distilled inverse polymer emulsion with brine.
• the prior dilution of the distilled polymer emulsion (polymer dispersion) with a brine significantly increases its ability to subsequently invert in the injection salt waters (during injection into Training underground), which implies effective (rapid and almost total) dissolving of the polymer to maximize its application effect.
• a first aspect of the invention therefore relates to an injection fluid F for hydraulic fracturing comprising at least one synthetic water-soluble polymer P with a weight-average molecular weight greater than or equal to 1 million daltons, said fluid being prepared according to a process comprising the following successive steps: a) An inverse emulsion E comprising between 15% and 40% by weight of polymer P, between 20 and 60% by weight of water and at least one hydrocarbon solvent, the percentages being expressed by weight relative to the weight of the emulsion E, b) the inverse emulsion E is distilled to obtain a dispersion D comprising between 40 and 60% by weight of polymer particles P, less than 10% by weight of water and at least one hydrocarbon solvent, the percentages being expressed by weight relative to the weight of the dispersion D, c) the dispersion D is diluted with 1% to 15% by weight of an aqueous solution S comprising between 20 and 60% by weight of salts, the s percentages being expressed by weight relative to the weight of dispersion D.
• a second aspect of the invention relates to a process for the hydraulic fracturing of an underground oil or unconventional gas reservoir using the injection fluid F according to the invention.
• a third aspect of the invention relates to a method of reducing friction using an injection fluid F in a hydraulic fracturing operation of an underground reservoir of unconventional oil or gas using the injection fluid F according to the invention.
• water-soluble polymer means a polymer which yields an aqueous solution without insoluble particles when dissolved with stirring for 4 hours at 25°C and with a concentration of 20 gL -1 in water .
• the "weight average molecular weight" of the synthetic water-soluble polymer P is determined by measuring the intrinsic viscosity.
• the intrinsic viscosity can be measured by methods known to those skilled in the art and can in particular be calculated from the reduced viscosity values for different concentrations by a graphical method consisting in plotting the reduced viscosity values (on the ordinate axis) as a function of the concentrations (on the abscissa axis) and by extrapolating the curve at zero concentration.
• the intrinsic viscosity value is read on the ordinate axis or using the least squares method. Then the weight average molecular weight can be determined by the famous Mark-Houwink equation:
• [q] represents the intrinsic viscosity of the polymer determined by the solution viscosity measurement method
• M represents the molecular weight of the polymer
• a represents the Mark-Houwink coefficient
• K depend on the particular polymer-solvent system. Tables known to those skilled in the art give the values of a and K according to the polymer-solvent system.
• the synthetic water-soluble polymer P of the invention has an average molecular weight advantageously greater than or equal to 1 million daltons, even more advantageously greater than or equal to 1.5 million daltons and even more advantageously greater than or equal to 2 million daltons. It is advantageously less than or equal to 20 million daltons.
• the synthetic water-soluble polymer P of the invention has an average molecular weight advantageously comprised between 1 million daltons and 20 million daltons, even more advantageously comprised between 1.5 million daltons and 20 million daltons, even more advantageously comprised between 2 million daltons and 20 million daltons.
• the inverse emulsion E comprising the synthetic water-soluble polymer P obtained by radical polymerization during step a) of the process for obtaining the fluid F contains:
• hydrophilic phase comprising at least one water-soluble structured polymer
• the lipophilic phase can be a mineral oil, a vegetable oil, a synthetic oil or a mixture of several of these oils.
• mineral oil are mineral oils comprising saturated hydrocarbons of the aliphatic, naphthenic, paraffinic, isoparaffinic, cycloparaffinic or naphthyl type.
• synthetic oil are hydrogenated polydecene or hydrogenated polyisobutene, esters such as octyl stearate or butyl oleate. Exxon's Exxsol® product line is a perfect fit.
• the weight ratio of the hydrophilic phase to the lipophilic phase in the inverse emulsion is preferably from 50/50 to 90/10.
• the term "emulsifying agent” means an agent capable of emulsifying water in an oil and an "inverting agent” is an agent capable of emulsifying an oil in water.
• an inverting agent is considered to be a surfactant with an HLB greater than or equal to 10
• an emulsifying agent is a surfactant with an HLB strictly less than 10.
• the hydrophilic-lipophilic balance (HLB) of a chemical compound is a measure of its degree of hydrophilicity or lipophilicity, determined by calculating the values of different regions of the molecule, as described by Griffin in 1949 (Griffin WC, Classification of Surface-Active Agents by HLB, Journal of the Society of Cosmetic Chemists, 1949, 1, pages 311-326).
• Griffin's method based on calculating a value based on the chemical groups of the molecule.
• Griffin assigned a dimensionless number between 0 and 20 to give information about water and oil solubility.
• Substances with an HLB value of 10 are distributed between the two phases, so that the hydrophilic group (molecular mass Mh) projects completely into the water while the hydrophobic hydrocarbon group (molecular mass Mp) is adsorbed in the non-phase. watery.
• HLB 20 (Mh / M)
• the inverse emulsion E according to the invention is prepared by radical polymerization.
• An aqueous solution comprising the monomer(s) making it possible to obtain the polymer P is emulsified in an oily phase comprising the emulsifying agent(s).
• the polymerization is carried out by adding a free radical initiator.
• a free radical initiator Reference may be made, as initiator, to redox couples, with cumene hydroperoxide, tertiary butylhydroxyperoxide or persulfates among the oxidizing agents, sodium sulfite, sodium metabisulfite and Mohr's salt among the agents reducers.
• Azo compounds such as 2,2'-azobis (isobutyronitrile) and 2,2'-azobis (2-amidinopropane) hydrochloride can also be used.
• the polymerization is generally carried out in an isothermal, adiabatic or temperature-controlled manner. That is, the temperature is kept constant, usually between 10 and 60°C (isothermal), or the temperature is allowed to rise naturally (adiabatic) and in this case the reaction is usually started at a lower temperature at 10°C and the final temperature is usually above 50°C or, finally, the temperature increase is controlled so as to have a temperature curve between the isothermal curve and the adiabatic curve (controlled temperature).
• the polymerization can be carried out under a pressure below atmospheric pressure, optionally under conditions making it possible to evaporate part of the water and of the hydrocarbon solvent from the reaction medium and to preconcentrate the emulsion.
• the synthetic water-soluble polymer P preferably results from the polymerization of monounsaturated ethylenic monomers which may be nonionic and/or anionic and/or cationic and/or zwiterrionic. These monomers are preferably the following:
• - nonionic monomers chosen from the group comprising acrylamide, methacrylamide, N-alkylacrylamides, N-alkylmethacrylamides, N,N-dialkylacrylamides, N,N-dialkylmethacrylamides, alkoxylated esters of acrylic acid , alkoxylated esters of methacrylic acid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkylacrylates, hydroxyalkyl methacrylates,
• - anionic monomers chosen from the group comprising monomers having a carboxylic function and their salts including acrylic acid, methacrylic acid, itaconic acid, maleic acid; monomers having a sulphonic acid function and their salts, including acrylamido tert-butyl sulphonic acid (ATBS), allyl sulphonic acid and methallyl sulphonic acid and their salts; monomers having a phosphonic acid function and their salts,
• - cationic monomers chosen from the group comprising quaternized or salified dimethylaminoethyl acrylate (ADAME); dimethylaminoethyl methacrylate (MADAME) quaternized or salified; diallyldimethylammonium chloride (DADMAC); acrylamidopropyltrimethylammonium chloride (APT AC); methacrylamidopropyltrimethylammonium chloride (MAPTAC),
• - zwitterionic monomers chosen from the group comprising sulfobetaine monomers such as sulfopropyl dimethylammonium ethyl methacrylate, sulfopropyl dimethylammonium propylmethacrylamide, sulfopropyl 2-vinylpyridinium; THE phosphobetaine monomers, such as phosphato ethyl trimethylammonium ethyl methacrylate; carboxybetaine monomers.
• the water-soluble polymer P can comprise at least one LCST or UCST group.
• an LCST group corresponds to a group whose solubility in water for a given concentration is modified beyond a certain temperature and according to salinity.
• This is a group with a transition temperature by heating defining its lack of affinity with the solvent medium.
• the lack of affinity with the solvent results in an opacification or a loss of transparency which may be due to precipitation, aggregation, gelling or viscosification of the medium.
• the minimum transition temperature is called “LCST” (lower critical solubility temperature, from the acronym “Lower Critical Solution Temperature”).
• LCST lower critical solubility temperature
• a UCST group corresponds to a group whose solubility in water for a given concentration is modified below a certain temperature and according to salinity.
• This is a group with a cooling transition temperature defining its lack of affinity with the solvent medium.
• the lack of affinity with the solvent results in an opacification or a loss of transparency which may be due to precipitation, aggregation, gelling or viscosification of the medium.
• the maximum transition temperature is called “UCST” (upper critical solubility temperature, from the acronym “Upper Critical Solution Temperature”).
• UCST upper critical solubility temperature, from the acronym “Upper Critical Solution Temperature”.
• the water-soluble polymer P in the inverse emulsion E can be linear or structured by at least one structural agent, which can be chosen from the group comprising polyethylenically unsaturated monomers (having at least two unsaturated functions), such as, for example, vinyl functions , allylics, acrylics and epoxies and one can cite for example methylene bis acrylamide (MBA), diallylamine, triallylamine, tetraallylammonium chloride, polyethylene glycol dimethacrylate or even by macroinitiators such as polyperoxides, polyazos and polytransfer agents such as polymercaptants polymers or even hydroxyalkylacrylates, epoxyvinyls.
• MVA methylene bis acrylamide
• macroinitiators such as polyperoxides, polyazos and polytransfer agents such as polymercaptants polymers or even hydroxyalkylacrylates, epoxyvinyls.
• the water-soluble polymer P can also be structured using techniques of controlled radical polymerization (CRP) or, and more particularly, of the RAFT (Reversible Addition Fragmentation Chain Transfer) type in inverse emulsion.
• CRP controlled radical polymerization
• RAFT Reversible Addition Fragmentation Chain Transfer
• the inverse emulsion E of water-soluble polymer P may comprise: a hydrophilic phase comprising at least one water-soluble (co)polymer P, a lipophilic phase, at least one interfacial polymer composed of at least one monomer of formula ( I): [Chem 1]
• Ri, R 2 , R3 are independently selected from the group consisting of a hydrogen atom, a methyl group, a carboxylate group and ZX,
• X is a group selected from alkanolamides, sorbitan esters, ethoxylated sorbitan esters, glyceryl esters, and polyglycosides; X comprising a hydrocarbon chain preferably comprising from 6 to 24 carbon atoms, saturated or unsaturated, linear, branched or cyclic, optionally aromatic.
• the interfacial polymer obtained by polymerization of at least one monomer of formula (I) forms an envelope at the interface of the hydrophilic phase and the lipophilic phase.
• the hydrophilic phase is in the form of micrometric droplets dispersed, advantageously emulsified, in the lipophilic phase.
• the average size of these droplets is advantageously between 0.01 and 30 ⁇ m, more advantageously between 0.05 and 3 ⁇ m.
• the interfacial polymer therefore comes to be placed at the interface between the hydrophilic phase and the lipophilic phase at the level of each droplet.
• the interfacial polymer partially or totally envelopes each of these droplets.
• the average size of the droplets is advantageously measured with a laser measuring device using conventional techniques which form part of the general knowledge of those skilled in the art. A Mastersizer type device from the Malvern company can be used for this purpose.
• the interfacial polymer comprises between 0.0001 and 10%, more advantageously between 0.0001 and 5% even more advantageously from 0.0001 to 1%, by number of monomer of formula (I), relative to the number total monomers.
• the interfacial polymer forms an envelope around the droplets forming the hydrophilic phase.
• the interfacial polymer can comprise at least one structural agent.
• the structural agent is advantageously chosen from diamine diacrylamides or methacrylamides; acrylic esters of di, tri, or tetrahydroxy compounds; methacrylic esters of di, tri, or tetrahydroxy compounds; divinyl compounds preferentially separated by an azo group; diallylic compounds preferentially separated by an azo group; vinyl esters of di or trifunctional acids; allyl esters of di or trifunctional acids; methylenebisacrylamide; diallylamine; triallylamine; tetraallylammonium chloride; divinylsulfone; polyethylene glycol dimethacrylate and diethylene glycol diallyl ether.
• the inverse emulsion E comprises from 0.5% to 5.0% by weight, the percentages being expressed by weight relative to the weight of the emulsion E, of at least one emulsifying agent preferably chosen from esters of sorbitan, polyethoxylated sorbitan esters, polyethoxylated fatty acids, polyethoxylated fatty alcohols, polyesters having an average molecular weight between 1000 and 3000 daltons resulting from the condensation between a poly(isobutenyl) succinic acid or its anhydride and a polyethylene glycol , block copolymers with an average molecular weight of between 2500 and 3500 daltons resulting from the condensation between hydroxystearic acid and a polyethylene glycol, ethoxylated fatty amines, derivatives of di-alkanol amides, stearyl methacrylate copolymers, and mixtures of these emulsifying agents.
• This emulsifying agent is added to the lipophilic
• a natural or synthetic polymer (described in particular in US Pat. No. 10,647,908) can be added at the end of the radical polymerization reaction of step a) of the process for obtaining the fluid F.
• the natural polymers there are, for example, the guar gums, and their derivatives such as hydroxypropylguar (HPG), or carboxymethylhydroxypropyl guar (CMHPG); cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose or hydroxypropyl cellulose.
• the polymer P predominates with respect to the natural polymer, preferably the polymer P represents from 50 to 100% by weight, preferably from 70 to 100%, more preferably from 90 to 100%, relative to the total weight of the polymer P + natural polymer.
• Step b) of the process for obtaining the injection fluid F consists in distilling the inverse emulsion E to obtain a dispersion D, the polymer P is therefore, after distillation, in the form of (solid) particles, comprising between 40 and 60% by weight of polymer particles P, less than 10% by weight of water and at least one hydrocarbon solvent, the percentages being expressed by weight relative to the weight of the dispersion D.
• the distillation is carried out under reduced pressure , preferably at a pressure of between 20 and 250 mbar and at a temperature of between 10 and 110°C.
• the polymer P is in the form of (solid) particles.
• the particles of synthetic water-soluble polymer P in dispersion D have an average size of between 0.01 ⁇ m and 100 ⁇ m, even more preferably between 0.1 ⁇ m and 5 ⁇ m.
• average size is meant in the present invention the average diameter of the particles.
• the particle size analysis is carried out according to conventional techniques known to those skilled in the art.
• An example of a device for measuring mean particle diameter is the Mastersizer from Malvern Instruments.
• step c) of the process for obtaining the injection fluid F of the invention preferably added to the dispersion (D) between 0.2 and 10% by weight, the percentages being expressed by weight relative to the weight of the dispersion D, of at least one reversing agent.
• the reversing agent is preferably chosen from ethoxylated nonylphenol, preferably having 4 to 10 ethoxylations; ethoxylated/propoxylated alcohols preferably having an ethoxylation/propoxylation comprising between 12 and 25 carbon atoms; ethoxylated tridecyl alcohols; polyethoxylated fatty acids, poly(ethoxylated/propoxylated) fatty alcohols; ethoxylated sorbitan esters; polyethoxylated sorbitan laurate; polyethoxylated castor oil; heptaoxyethyl lauryl alcohol; polyethoxylated sorbitan monostearate; polyethoxylated alkyl phenol cetyl ether; polyethylene oxide alkyl aryl ether; N-cetyl-N-ethyl morpholinium ethosulfate; sodium lauryl sulphate; condensation products of fatty alcohols with ethylene oxide; condensation products
• Step c) of the process for obtaining the injection fluid F consists in diluting the dispersion D with 1% to 15% by weight of an aqueous solution S containing between 20 and 60% salts, preferably between 25 and 45 %, the percentages being expressed by weight relative to the weight of dispersion D.
• Solution S is preferably a brine solution.
• At least a portion of the water of the solution S is extracted from the distillate of the emulsion E.
• the salts of the aqueous solution S are alkaline or alkaline-earth or ammonium salts or organic salts or a mixture of these salts. More preferentially, the salts are chosen from sodium chloride, ammonium sulphate, ammonium thiosulphate, ammonium chloride, choline chloride, monosaccharide salts or a mixture of these salts.
• step c) of the process for obtaining fluid F other compounds known to those skilled in the art can be added, such as those mentioned in document SPE 152596, for example:
• Biocides to prevent the development of bacteria in particular sulphate-reducing bacteria, which can form viscous masses that reduce passage surfaces. Mention may be made, for example, of glutaraldehyde, which is the most widely used, or else formaldehyde or isothiazolinones, and/or
• Oxygen scavengers such as ammonium bisulphite to prevent the destruction of other components by oxidation and corrosion of the injection tubes, and/or
• Anti-corrosion additives to protect the tubes against oxidation by residual quantities of oxygen such as N,N-dimethylformamide, and/or
• Lubricants such as oil distillates, and/or
• Iron chelators such as citric acid, EDTA (ethylene diamine tetraacetic acid), phosphonates, and/or
• Scale inhibitors such as phosphates, phosphonates, polyacrylates or ethylene glycol.
• the present invention therefore also relates to a process for the preparation of an injection fluid F comprising the following steps: a) An inverse emulsion E comprising between 15% and 40% by weight of a synthetic water-soluble polymer P of weight-average molecular weight greater than or equal to 1 million daltons, between 20 and 60% by weight of water and at least one hydrocarbon solvent, the percentages being expressed by weight relative to the weight of the emulsion E, b) The inverse emulsion E is distilled to obtain a dispersion D comprising between 40 and 60% by weight of polymer particles P, less than 10% by weight of water and at least one hydrocarbon solvent, the percentages being expressed by weight relative to the weight of the dispersion D, c) the dispersion D is diluted with 1% to 15% by weight of an aqueous solution S comprising between 20 and 60% by weight of salts, the percentages being expressed by weight relative to the weight of scatter d.
• a second aspect of the invention also relates to a process for the hydraulic fracturing of an underground reservoir of unconventional oil or gas, comprising the preparation of an injection fluid F as described previously, the dissolving in a salt water and injecting said fracturing fluid F into a subterranean formation.
• the injection is carried out under pressure so as to create fractures distributed all along the production well.
• the injection fluid F obtained by the method of the invention is dissolved in salt water to have a polymer concentration of between 0.01 and 10 g/L in this water. salty.
• the salt waters are sea waters or can advantageously be prepared with monovalent and/or polyvalent salts or combinations thereof.
• salts include, without limitation, sodium, lithium, potassium, aluminum, ammonium, phosphate, sulfate, magnesium, barium, nitrate and other inorganic salts and mixtures thereof.
• Salt waters preferably contain at least one of the following elements: sodium chloride, calcium chloride, sodium bromide, calcium bromide, barium chloride, magnesium chloride, zinc bromide, sodium formate and potassium formate .
• the salt water used for dissolving the injection fluid F contains more than 70,000 ppm of salts and preferably more than 100,000 ppm of salts, preferably the brine contains from 70,000 to 350,000 ppm of salts , preferably from 100,000 to 350,000 ppm.
• the divalent ratio R+ mass ratio: divalent salts/total salts of the salt water is greater than or equal to 0.20 and even more preferably R+ > 0.25.
• At least one proppant is added before or after it is dissolved in salt water.
• the proppant can be chosen without limitation from sand, ceramic, bauxite, glass beads, and sand impregnated with resin. It advantageously represents from 0.5 to 40%, more preferentially from 1 to 25% and even more preferentially from 1.5 to 20%, by weight relative to the total weight of the injection fluid F for hydraulic fracturing.
• At least one oxidizing compound and/or at least one surfactant compound is injected into the reservoir.
• the injection of surfactant makes it possible to eliminate the wettability with the rock, while the injection of the oxidizing compound destroys the copolymer. In both cases, the injection restores a fluid viscosity close to that of water.
• bleach aqueous solution of a hypochlorite salt
• hydrogen peroxide aqueous solution of a hypochlorite salt
• ozone aqueous solution of a hypochlorite salt
• chloramines aqueous solution of a hypochlorite salt
• persulphates permanganates or perchlorates.
• the chemical nature of the surfactant compound(s) is not critical. They can be anionic, nonionic, amphoteric, zwitterionic and/or cationic. Preferably, the surfactant compound(s) of the invention carry(s) anionic charges.
• the surfactant compounds used are chosen from anionic surfactants and their zwitterions chosen from the group comprising derivatives of alkyl sulphates, alkyl ether sulphates, arylalkyl sulphates, arylalkyl ether sulphates, alkyl sulphonates, alkyl ether sulphonates, d arylalkyl ether carboxylates, alkyl polyethers, arylalkyl polyethers...
• alkyl chain is defined as a chain of 6 to 24 carbons, branched or not, with or without several units, possibly comprising one or more heteroatoms, for example O, N or S, preferably 1, 2 or 3 heteroatoms.
• Arylalkyl chain is defined as a chain of 6 to 24 carbons, branched or not, comprising one or more aromatic rings and possibly comprising one or more heteroatoms, for example 1, 2 or 3 heteroatoms, preferably O, N or S.
• surfactants for reasons of cost, stability, and availability, are of the sulphonate or sulphate type, presented in the form of alkali metal or ammonium salts.
• a last aspect of the invention relates to a method for reducing friction during a hydraulic fracturing operation of an underground reservoir of oil or untreated gas. conventional, comprising the preparation of a fluid F as described previously, the dissolving in salt water and the injection of said fracturing fluid into an underground formation.
• Friction reduction makes it possible to reduce or eliminate friction-related losses during the injection of fracturing fluid.
• An aqueous phase is prepared with 42.1 g of an acrylamide solution (50% by weight in water), 9.1 g of acrylic acid, 10.1 g of a sodium hydroxide solution ( at 50% by weight in water), 0.49 g of a solution of diethylenetriaminepentaacetic acid (at 40% by weight in water), 0.02 g of a solution of tert-butyl hydroperoxide (at 70% by weight in water), 0.006 g of sodium hypophosphite and 9.134 g of water.
• An organic phase is prepared by mixing 20.1 g of an oil (Exxsol® D120 S) with 2.3 g of sorbitan monooleate, 0.5 g of 5-fold ethoxylated sorbitan monooleate and 5 g of a surfactant polymer .
• the aqueous phase is added to the organic phase under shear to form an emulsion.
• the emulsion is then degassed with a stream of nitrogen for 30 minutes while maintaining the temperature at 20°C.
• 0.75 g of sodium metabisulphite in solution (at 0.01% by weight in water) is injected for 90 minutes.
• the polymerization temperature is maintained between 40 and 55°C.
• the residual monomers are reacted by adding 0.4 g of a sodium bisulphite solution (at 40% by mass concentration).
• An inverting agent ethoxylated fatty alcohol (Lutensol TO89®) is added at 10% by weight to dispersion D1.
• An injection fluid F1 containing 50% by weight of polymer P1 is thus obtained.
• Dispersion D1 obtained in Example 2 is diluted by adding 18% of a saturated aqueous solution of sodium chloride and 10% of inverting agent (Lutensol TO89®).
• An injection fluid F2 containing 40% by weight of polymer P1 is thus obtained.
• Dispersion D1 obtained in example 2 is diluted by adding 18% by weight of a saturated aqueous solution of ammonium chloride and 10% of inverting agent (Lutensol TO89®). An injection fluid F3 containing 40% by weight of polymer P1 is thus obtained.
• Dispersion D1 obtained in example 2 is diluted by adding 18% by weight of a saturated aqueous solution of ammonium thiocyanate and 10% of inverting agent (Lutensol
• Dispersion D1 obtained in Example 2 is diluted by adding 18% by weight of a saturated aqueous solution of ammonium sulphate and 10% of inverting agent (Lutensol TO89®). An injection fluid F5 containing 40% by weight of polymer P1 is thus obtained.
• Dispersion D1 obtained in example 2 is diluted by adding 18% by weight of a saturated aqueous solution of ammonium thiosulfate and 10% of inverting agent (Lutensol TO89®). An injection fluid F6 containing 40% by weight of polymer P1 is thus obtained. Reversal tests
• injection fluids F1 (comparative) and F2 to F6 (according to the invention) are dissolved by following two different protocols.
• Protocol 1 direct addition of injection fluids in brine
• Protocol 2 (addition of injection fluids in water then addition of salts)
• injection fluids F2 to F6 By using injection fluids F2 to F6, the viscosity of polymer solutions P1 in seawater is higher. The polymer P1 in these injection fluids is released more easily into the seawater.
• the process for preparing the injection fluids according to the invention therefore makes it possible to improve the release of the polymer into the brine.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Polymerisation Methods In General (AREA)

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• 2021
  • 2021-09-15 FR FR2109669A patent/FR3126988B1/fr active Active
• 2022
  • 2022-09-13 CN CN202280062312.8A patent/CN118043430A/zh active Pending
  • 2022-09-13 US US18/689,064 patent/US12404446B2/en active Active
  • 2022-09-13 AR ARP220102477A patent/AR127048A1/es unknown
  • 2022-09-13 CA CA3230987A patent/CA3230987A1/fr active Pending
  • 2022-09-13 EP EP22789177.7A patent/EP4402220A1/de active Pending
  • 2022-09-13 WO PCT/EP2022/075444 patent/WO2023041539A1/fr not_active Ceased

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