Fracturing fluid containing a polymer of crystalline form of 2-acrylamido-2-methylpropanesulfonate sodium salt and hydraulic fracturing method

Abstract

The present invention relates to a fracturing fluid comprising at least one propane and at least one water-soluble polymer obtained from the crystalline form of 2-acrylamido-2-methylpropanesulfonate sodium salt ATBS.Na. The present invention also relates to a method for preparing the fluid and a method of hydraulic fracturing using the fluid.

Description

[Technical Field]

[0001] The present invention relates to a fracturing fluid comprising at least one propane and at least one water-soluble polymer prepared from the crystalline form of 2-acrylamido-2-methylpropanesulfonate sodium salt.

[0002] The present invention also relates to a method for hydraulic fracturing of unconventional underground hydrocarbon reservoirs (petroleum and / or gas) using the aforementioned fluid. [Background technology]

[0003] The production of hydrocarbons (petroleum and / or gas) contained in unconventional underground reservoirs has been under development for several years, and for economical hydrocarbon production, it is necessary to create fracturing sections in the aforementioned reservoirs.

[0004] In the prior art and the subsequent description of the present invention, the terms “unconventional underground reservoir” or “unconventional reservoir” mean sediments that do not exist in the form of deposits in porous, permeable rock and therefore require specific extraction techniques (see Les hydrocarbures de roche-mere en France Rapport provisoire - CGIET n° 2011-04-G -, Sustainable Development, Transport and Housing - April 2011). Unconventional gas reservoirs may refer to shale gas, coalbed methane, or tight gas. Unconventional oil reservoirs may refer to heavy oil, shale oil, or tight oil.

[0005] The reserves contained in unconventional reservoirs are enormous and extend to extremely wide areas that were previously unextractable, such as shale, tight gas, and source rock hydrocarbons like coal gas. In the United States, shale gas is widely developed and currently accounts for 46% of all natural gas produced in the U.S., up from 28% in 1998. Very large sedimentary basins are known as Barnett Shale, Ville Fayette Shale, Mowry Shale, Marcellus Shale, and Utica Shale. The development of tight reservoirs has been made possible by advances in drilling technology.

[0006] Production technology has indeed evolved from vertical to horizontal wells, reducing the number of production wells required and the surface area occupied, allowing for wider coverage of the reservoir volume and enabling the recovery of as much gas or oil as possible. However, insufficient permeability prevents hydrocarbons from easily moving from the source rock to the well, making it difficult to produce gas or oil in large quantities economically. Therefore, stimulation work, particularly hydraulic fracturing, is necessary to increase the permeability and production surface of the rock in contact with the well.

[0007] Hydraulic fracturing The purpose of hydraulic fracturing is to increase permeability and create a larger gas or oil production surface. In reality, low permeability, natural barriers by dense layers, and watertightness caused by drilling operations severely limit production. Gas or oil contained in unconventional reservoirs cannot easily move from the rock to the well without stimulation.

[0008] These hydraulic fracturing operations in horizontal wells began in the Appalachian region in 1960, and today tens of thousands of operations are carried out across the United States.

[0009] The techniques for surveying, reservoir modeling, drilling, cementing, and stimulation are becoming increasingly sophisticated, and implementation equipment is being introduced that allows these operations to be carried out in increasingly shorter times, along with accurate results analysis.

[0010] Stimulation of reservoirs by hydraulic fracturing These operations involve injecting water at high pressure and very high flow rates to create fracturing zones distributed perpendicularly to the production well. This procedure is generally carried out in multiple steps to create fracturing zones along the entire length of the horizontal well, enabling the handling of the maximum reservoir volume.

[0011] To keep these crushing sections open, propane (e.g., sand, plastic, or calibrated ceramics) is added to prevent them from closing and maintain the capillary action created even after the pressurization is stopped.

[0012] Water alone has low viscosity, making it insufficient to achieve good propane placement efficiency. Therefore, there are limitations to its ability to retain propane in place within the crushing section. To solve this problem, crushing fluids containing thickening compounds have been developed.

[0013] By definition, a compound is considered to be a viscous compound if it increases the viscosity of the solution in which it is dissolved (as described in the prior art and the present invention).

[0014] In addition to having thickening properties, the compound must have a specific rheological profile. In fact, under the high shear conditions experienced during the injection of the fracturing fluid, the compound must be able to produce a low viscosity so as not to hinder the transport and pumping of the fluid containing the propane. Once the shear decreases after injection, the compound must produce sufficient viscosity to support the propane and retain it within the fracturing section.

[0015] Therefore, the thickening compound, which is generally a polymer, needs to be given shear-reducing viscosity properties in the solution such that it has a relatively low viscosity when pressed (under high shear) and a high viscosity when the shear decreases in order to maintain the state in which the propane is suspended in the crushed part.

[0016] The viscoelastic properties of polymers in solution should also be considered. This viscoelasticity and its importance in applications are described in document SPE 147206 (Fracturing Fluid Comprised of Components Source Solely from the Food Industry Provides Superior Proppant Transport - David Loveless, Jeremy Holtsclaw, Rajesh Saini, Phil Harris, and Jeff Fleming, SPE, Halliburton) by visual observation in static or dynamic experiments, or by rheological measurements such as the measurement of viscosity coefficient and elastic modulus (G' and G'') or rheometer measurement of viscosity as a function of shear. Therefore, elastic properties are advantageous for ensuring the transport and suspension of fractured propane.

[0017] Therefore, the selection of polymers is not trivial, and thorough rheological research is necessary to obtain satisfactory results.

[0018] Among the aqueous thickening compounds belonging to the prior art, natural substances such as guar gum and their derivatives, such as hydroxypropyl guar (HPG) or carboxymethylhydroxypropyl guar (CMHPG); and cellulose derivatives such as carboxymethylcellulose or hydroxyethylcellulose may be mentioned. These compounds are described in particular in U.S. Patents 4,033,415, 3,888,312, and 4,801,389. Document SPE 152596 (Hydraulic Fracturing 101: What Every Representative, Environmentalist, Regulator, Reporter, Investor, University Researcher, Neighbor and Engineer Should Know About Estimating Frac Risk and Improving Frac Performance in Unconventional Gas and Oil Wells - George E. King, Apache Corporation) discusses in detail the latest advances in the performance of fracturing fluids.

[0019] However, these natural substances, particularly guar derivatives, are also useful in other applications such as the food or textile industries, and the boom in developing oil and gas resources from unconventional reservoirs is competing with these other applications. This is putting pressure on the availability of these products and creating cost issues.

[0020] Other compounds derived from petrochemicals may also possess thickening properties. Synthetic polymers can be mentioned. Partially hydrolyzed poly(meth)acrylamides and poly(meth)acrylates, as well as polymers thereof, are particularly well known. These polymers exhibit viscosity, particularly due to their molar mass and inter-chain ionic repulsion. These polymers are described in British Patent No. 951147, U.S. Patent No. 3,727,689, U.S. Patent No. 3,841,402, or U.S. Patent No. 3,938,594. The mechanisms governing viscosity are related to hydrodynamic volume increases due to inter-chain and intra-chain repulsion, inter-chain entanglement, etc.

[0021] However, in the presence of high salt concentrations or high temperatures during use, these polymers do not exhibit strong entanglement and repulsion, resulting in a significant decrease in viscosity, particularly after shearing during the pumping process. Furthermore, these polymers generally do not possess sufficient viscoelastic properties to support propane within the crushed section. To obtain the aforementioned propane suspension properties, the amount of these polymers added must be increased to a high level. However, such amounts are not economically practical.

[0022] The polymers used to provide viscosity-enhancing properties can also, advantageously, act as friction reducers, thereby reducing load reduction in turbulent media and enabling a significant increase in flow rate for the same output and pipe diameter.

[0023] Synthetic polymers based on sodium 2-acrylamide-2-methylpropanesulfonate exhibit interesting friction-reducing properties in aqueous solutions. These polymers are also known for their resistance to shear and thermal decomposition, particularly in saline water. However, very high molecular weight polymers based on sodium 2-acrylamide-2-methylpropanesulfonate are difficult to obtain, and it goes without saying that solubility problems arise as the molecular weight of these polymers increases. Nevertheless, to obtain optimal friction reduction and high viscosity generation, it is essential that the polymer dissolves quickly, especially in saline aqueous solutions, and that the polymer has a very high molecular weight. [Overview of the project]

[0024] The applicant has discovered and developed a fracturing fluid that ensures an improved viscosity-enhancing effect in saline (brine) or non-saline aqueous (water) solutions while simultaneously providing a very high friction-reducing effect.

[0025] In addition, the good solubility of the polymer in the fracturing fluid, combined with its sulfonic and anionic properties, allows for the avoidance of adsorption of the polymer to rock, which in turn leads to the restoration of conductivity and, consequently, an increase in hydrocarbon production yield (petroleum and / or gas). Petroleum (oil) from underground reservoirs is also called petroleum. It is usually a mixture of hydrocarbons.

[0026] According to the present invention, the improved performance of the polymer-containing crushing fluid obtained from the crystalline form of sodium 2-acrylamido-2-methylpropanesulfonate salt, referred to herein as ATBS.Na, makes it possible to reduce the amount of product required (especially the polymer), and therefore, the overall water consumption and emissions of greenhouse gases such as CO2 can be reduced.

[0027] A first aspect of the present invention relates to a fracturing fluid comprising at least one propane and at least one water-soluble polymer obtained from the crystalline form of ATBS.Na.

[0028] A second aspect of the present invention relates to a method for producing a fracturing fluid using at least one water-soluble polymer obtained from the crystalline form of ATBS.Na.

[0029] A third aspect of the present invention relates to a method for hydraulic fracturing of unconventional underground oil or gas storage tanks using the fracturing fluid of the present invention.

[0030] A fourth aspect of the present invention relates to a method for reducing friction using a fracturing fluid in hydraulic fracturing operations of unconventional underground oil or gas storage tanks using the fracturing fluid of the present invention. [Modes for carrying out the invention]

[0031] The term "polymer" should be understood to mean a homopolymer or copolymer. The term "copolymer" should be understood to mean a polymer obtained from at least two different monomers. Therefore, it may be a copolymer of at least two monomers selected from anionic monomers, cationic monomers, nonionic monomers, zwitterionic monomers, hydrophobic monomers, and mixtures thereof.

[0032] The term "hydrophilic monomer" refers to an octanol-water partition coefficient K of 1 or less. ow It should be understood that this refers to a monomer having a partition coefficient K ow It is identified in a 1:1 volume ratio octanol-water mixture at 25°C and a pH of 6–8.

[0033] The term "hydrophobic monomer" refers to an octanol-water partition coefficient greater than 1 K ow It should be understood that this refers to a monomer having a partition coefficient K ow It is identified in a 1:1 volume ratio octanol-water mixture at 25°C and a pH of 6–8.

[0034] The terms "crystal" or "crystalline form" refer to a solid material in which its constituent elements (atoms, molecules, or ions, etc.) are arranged in a highly regular microscopic structure, forming a crystalline lattice that extends in all directions. Amorphous solids are not included.

[0035] Octanol-water partition coefficient K ow This represents the concentration (g / L) ratio of monomers between the octanol phase and the aqueous phase. This is defined as follows:

[0036]

number

[0037] By definition, a water-soluble polymer is defined as 10 g / L while stirring at 25°C. -1 This refers to a polymer that, when dissolved in water at a certain concentration, yields an aqueous solution.

[0038] "X and / or Y" should be understood to mean "X" or "Y" or "X and Y".

[0039] The present invention also includes all possible combinations of the various embodiments disclosed, whether they are preferred embodiments or given as examples. Furthermore, where ranges of values ​​are indicated, limit values ​​are included within those ranges. The disclosure also includes all combinations between the limit values ​​of these ranges. For example, the value range "1 to 20, preferably 5 to 15" means the ranges "1 to 5", "1 to 15", "5 to 20", and "15 to 20", as well as the disclosure of the values ​​1, 5, 15, and 20.

[0040] Crystal form of ATBS.Na The crystal form of ATBS.Na has a powder X-ray diffraction pattern that includes peaks at positions where the 2θ angles are 11.7°; 12.2°; 13.2°, 13.5°, 15.6°, 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°. The uncertainty of these peaks is generally on the order of ±0.1°.

[0041] X-ray crystallography, radiation crystallography, or X-ray diffraction is an analytical technique used to examine the structure of crystalline substances at the atomic scale. This is based on the physical phenomenon of X-ray diffraction. A diffractometer using a copper X-ray source can be used.

[0042] Powders formed from a specific crystal phase always show diffraction peaks in the same directions. This diffraction pattern thus forms the true signature of the said crystal phase. Therefore, it is possible to identify the nature of each crystal phase within a mixture or a pure product.

[0043] This signature is specific to each organic or inorganic crystalline compound and is in the form of a list of peaks located at the angle of 2θ (2-theta).

[0044] This technique is used for the characterization of the properties of substances, particularly the different crystal forms that can exist for the same chemical molecule.

[0045] The said crystal form of ATBS.Na has, in the Fourier transform infrared spectrum, 3576 cm -1 , 3485 cm -1 , 3310 cm -1 , 3079 cm -1 , 2975 cm -1 , 1658 cm -1 , 1629 cm -1 , 1543 cm -1 , 1403 cm -1, 1321cm -1 , 1301cm -1 , 1205cm -1 , 1187cm -1 , 1163cm -1 , 1046cm -1 , 980cm -1 , 629cm -1 It includes peaks. The uncertainty of these peaks is generally ±8cm. -1 This is the order.

[0046] Infrared measurement is performed, for example, with an 8cm single-reflection ATR polarizing accessory. -1 This is performed using a Perkin Elmer Spectrum 100 spectrometer with high precision, and is carried out by Fourier transform.

[0047] Fourier transform infrared spectroscopy is the analysis of vibrations emitted, absorbed, or scattered by molecules. This technique is highly sensitive to so-called short interactions (the influence of a unit mesh on bonding). In most cases, the Fourier transform infrared spectra of different crystal systems differ significantly. Therefore, the Fourier transform infrared spectra reflect the details of the aforementioned crystal structure of a chemical compound.

[0048] Generally, and unless otherwise specified, X-ray diffraction patterns and infrared spectra are obtained at 20°C and an absolute pressure of 1 atmosphere (101,325 Pa).

[0049] The crystalline form of ATBS.Na has a concentration of more than 500 mJ, preferably 1000 mJ (1 mJ = 10⁻¹⁰ mJ). -3 It has a minimum ignition energy of less than 1 joule.

[0050] Minimum ignition energy represents the minimum energy required to ignite a product (chemical compound). This energy can be electrical or thermal. Minimum ignition energy is essential information when considering the risk of explosion during product handling (transportation, storage, reaction, molding, etc.).

[0051] The minimum ignition energy depends on the properties (composition) of the powder and its polymer structure (particle size, crystal form, specific surface area).

[0052] For solids, this energy represents the minimum energy required for an electric spark that is likely to ignite cloud-like dust. The higher the minimum ignition energy, the lower the risk the solid poses when used, handled, or stored.

[0053] The minimum ignition energy is measured according to the NF EN 13821 standard.

[0054] The crystalline form of ATBS.Na exhibits two thermal phenomena at 49.8°C, 144.8°C, 169.8°C, and 254.3°C, as determined by differential scanning calorimetry. The uncertainty regarding the observation of these phenomena is generally on the order of 10°C (±10°C), and favorably on the order of 5°C or less.

[0055] The aforementioned thermal phenomenon is measured by differential scanning calorimetry (DSC). This technique uses the measurement of the change in heat associated with the thermal denaturation of a compound when the compound is heated at a constant rate, for example, at a heating rate of 10°C / min.

[0056] Method for producing crystalline forms of sodium salts The method for producing the crystalline form of ATBS.Na includes at least the following sequential steps. 1) To form an aqueous solution or aqueous suspension SA2, mix 2-acrylamido-2-methylpropanesulfonic acid with aqueous solution SA1 and at least one sodium salt base, preferably for at least 1 minute; 2) To form suspension S1, distill the aqueous solution or aqueous suspension SA2 at a pressure of 700 mbar or less; 3) Separating the suspension S1 into solid and liquid components, and isolating the crystals of the suspension S1 obtained at the end of step 2) in the form of composition C1. The resulting crystal is the aforementioned crystalline form of ATBS.Na.

[0057] In step 1), “sodium salt base” should be understood to mean at least one inorganic sodium salt Brønsted base, such as sodium hydroxide, sodium carbonate, sodium bicarbonate, or a mixture thereof.

[0058] The temperature and mixing time in step 1) can vary, in particular, depending on the concentration of 2-acrylamido-2-methylpropanesulfonic acid (ATBS). Those skilled in the art will know how to adjust the temperature and mixing time to optimize crystal formation.

[0059] The method for producing the crystalline form of the sodium salt can be carried out for any form of ATBS, such as needle-shaped or hydrated forms.

[0060] The above manufacturing method may be carried out with ATBS of any purity.

[0061] Therefore, the method may be carried out downstream of any type of method for producing ATBS. It may also be carried out on ATBS crystals that have already been obtained.

[0062] Step 1 of the method for producing the crystalline form of sodium salt): ATBS is produced by the manufacturing methods described above (acrylonitrile, fuming sulfuric acid, and isobutylene). ATBS may be in the form of a fine powder, or it may be molded under controlled conditions by methods such as compression, granulation, or extrusion.

[0063] The addition of ATBS to the aqueous solution SA1 may be carried out before, after, or in parallel with the sodium salt base, preferably in parallel. Preferably, the aqueous solution SA1 is water.

[0064] The sodium salt base may be added as an aqueous solution. In this case, part or all of the aqueous solution of the sodium salt base may be aqueous solution SA1.

[0065] Advantageously, the concentration of ATBS sodium salt in the aqueous solution or aqueous suspension SA2 is 1% by weight to the saturation concentration, preferably 10% by weight to the saturation concentration, more preferably 20% by weight to the saturation concentration, more preferably 30% by weight to the saturation concentration, more preferably 40% by weight to the saturation concentration, and even more preferably 50% by weight to the saturation concentration, based on the weight of the aqueous solution or aqueous suspension SA2.

[0066] The ATBS and the sodium salt base may be added all at once or in several stages. Adding them in several stages is preferable. Adding them all at once is preferable.

[0067] When added in several stages, the ATBS and the sodium salt base are added in portions.

[0068] When the ATBS and the sodium salt base are added in portions, there is no limit to the number of portions, and advantageously there are at least two portions, preferably at least three portions.

[0069] There are no restrictions on the order in which the ATBS and the sodium salt base are added. They may be added simultaneously (i.e., in parallel), one by one in sequence (first the ATBS, then the sodium salt base, or vice versa), or in a different manner (first portion of ATBS, then first portion of the sodium salt base, then second portion of ATBS, then second portion of the sodium salt base, etc.), and preferably they are added simultaneously.

[0070] If these are added one by one in sequence or by other means, the addition of the second compound (whether the ATBS or the sodium salt base) may begin before the addition of the first compound is completed.

[0071] The first portion F1 of ATBS advantageously corresponds to at least 1 mol%, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol%, and even more preferably at least 20 mol% of the total ATBS present in the aqueous solution or aqueous suspension SA2.

[0072] The second portion F2 of ATBS advantageously corresponds to at least 1 mol%, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol%, and even more preferably at least 20 mol% of the total ATBS present in the aqueous solution or aqueous suspension SA2.

[0073] The third portion F3 of ATBS advantageously corresponds to at least 1 mol%, preferably at least 5 mol%, more preferably at least 10 mol%, even more preferably at least 15 mol%, and even more preferably at least 20 mol% of the total ATBS present in the aqueous solution or aqueous suspension SA2.

[0074] In a particular embodiment, the method is carried out continuously, in which case the ATBS and the sodium salt base are added continuously.

[0075] The amount of ATBS in the aqueous solution or aqueous suspension SA2 is advantageously 10 to 90% by weight, preferably 20 to 85% by weight, and more preferably 30 to 80% by weight, relative to the total weight of the aqueous solution or aqueous suspension SA2.

[0076] The mixing step 1) (ATBS + sodium salt base) is advantageously carried out at a temperature of 0 to 90°C, preferably 5 to 60°C, more preferably 10 to 40°C, in order to obtain an aqueous solution or aqueous suspension SA2.

[0077] In certain embodiments, the aqueous solution or suspension SA2 may contain one or more organic solvents.

[0078] In some embodiments, the aqueous solution SA1 may contain one or more organic solvents.

[0079] The amount of organic solvent can vary depending on the temperature and the amount of ATBS or sodium salt base. This amount is not limited as long as it does not prevent obtaining the aforementioned crystalline form of ATBS.Na. Methods for determining this limit are well known to those skilled in the art and are common practice. Generally, aqueous solutions or aqueous suspensions SA2 contain more water (by volume) than organic solvent.

[0080] The one or more organic solvents are advantageously selected from the following compounds: - Organic acids, preferably carboxylic acids containing 1 to 8 carbon atoms; - Preferably amides containing 1 to 8 carbon atoms; - Alcohols that preferably contain 1 to 8 carbon atoms; - Preferably ketones containing 3 to 8 carbon atoms; - Ethers, which are advantageously composed of 2 to 8 carbon atoms; - Preferably esters containing 2 to 8 carbon atoms; - Alkanes, preferably containing 4 to 8 carbon atoms, more preferably 5 to 6 carbon atoms; - Preferably halogenated hydrocarbon compounds containing 1 to 8 carbon atoms; - Preferably nitriles containing 1 to 8 carbon atoms; or - These mixtures.

[0081] When an organic solvent is used in the present invention, the temperature can be adjusted so that the solvent-water mixture remains in a liquid state.

[0082] These compounds may be linear or branched. They may be saturated or contain unsaturated bonds. Unsaturated bonds correspond to double or triple bonds (e.g., C=C or C≡C).

[0083] The organic solvent is preferably selected from acrylonitrile, isopropanol, acrylic acid, acetic acid, or a mixture thereof. The organic solvent is preferably acrylonitrile.

[0084] The organic solvent is generally a liquid at the temperature in which steps 2) and 3) are carried out. Furthermore, it is advantageously partially miscible with water, and preferably completely miscible with water.

[0085] The aforementioned organic solvent may, if necessary, be used to solubilize impurities or by-products present with the ATBS used to form the aqueous solution or aqueous suspension SA2. However, ATBS is not necessarily soluble in the aforementioned solvent.

[0086] In preferred embodiments of the present invention, the aqueous solution or aqueous suspension SA2 does not contain an organic solvent.

[0087] In a preferred embodiment of the present invention, the aqueous solution SA1 does not contain an organic solvent.

[0088] The time for mixing the aqueous solution SA1 and the ATBS is advantageously at least 1 minute, preferably 1 to 600 minutes, more preferably 5 to 400 minutes, and even more preferably 10 to 240 minutes.

[0089] The compounds in step 1) can be mixed using a variety of techniques. Examples, but not limited to, include stirrers, loop reactors, static mixers, microreactors, piston reactors, stirred filter dryers such as Nutsche, paddle mixers, double cone mixers, plowshare mixers, and disc mixers.

[0090] The pH in step 1) is advantageously controlled to be 6-14, preferably 8-14, more preferably 10-14, even more preferably 12-14, and even more preferably 13-14.

[0091] The amount of ATBS.Na in the aqueous solution SA2 or aqueous suspension SA2 is advantageously 10 to 90% by weight, preferably 20 to 90% by weight, preferably 30 to 90% by weight, preferably 50 to 90% by weight, preferably 20 to 85% by weight, and more preferably 30 to 80% by weight, relative to the total weight of the aqueous solution or aqueous suspension SA2.

[0092] Step 2 of the method for producing the crystalline form of sodium salt): The distillation of the aqueous solution or aqueous suspension SA2 is carried out at a pressure of 700 mbar or less. This distillation is generally carried out in a vacuum distillation apparatus, which is typically an evaporator. Therefore, it is also referred to as "vacuum distillation" in this specification.

[0093] When an aqueous solution or aqueous suspension SA2 is distilled, typically by passing it through an evaporator, crystals of ATBS.Na begin to form. Thus, ATBS, at least one sodium salt base, and crystalline solid particles of ATBS.Na coexist in the aqueous solution or aqueous suspension SA2.

[0094] The aqueous solution or aqueous suspension SA2 may be distilled using an evaporator. This may be a falling film evaporator, a rising film evaporator, a scraped thin film evaporator, a short-pass evaporator, a forced-circulation evaporator, a helical tube evaporator, or a flash evaporator. It may also be a continuous stirring reactor. Preferably, the distillation is carried out in a scraped thin film evaporator, a short-pass evaporator, or a forced-circulation evaporator. More preferably, the distillation is carried out in a scraped thin film evaporator.

[0095] Generally, an evaporator is a device that includes an inlet for the solution to be processed (aqueous solution or aqueous suspension SA2), an outlet for discharging the distilled solvent (water and any organic solvent), and an outlet for discharging the suspension S1.

[0096] The residence time of the aqueous solution or aqueous suspension SA2 in a distillation apparatus (preferably under reduced pressure), which is preferably an evaporator, i.e., the distillation time at a pressure of 700 mbar or less, is preferably between 1 second and 600 seconds, preferably between 3 seconds and 300 seconds, and more preferably between 30 seconds and 100 seconds. The residence time corresponds to the time required to carry out step 2), i.e., the time required to produce suspension S1 by distillation of the aqueous solution or aqueous suspension SA2. In other words, if an evaporator is used, it is the residence time of the ATBS (and / or the crystalline form of its sodium salt) between the inlet and outlet of the apparatus. This residence time varies depending on the amount of water (and any organic solvent), ATBS, and sodium salt base present in the aqueous solution or aqueous suspension SA2. To those skilled in the art, it is well known how to adjust this residence time for the purpose of obtaining the crystalline form of ATBS.Na depending on the amount of components of the aqueous solution or aqueous suspension SA2.

[0097] The distillation may be carried out in a vertical or horizontal evaporator. Preferably, it is carried out in a vertical evaporator.

[0098] The aqueous solution or aqueous suspension SA2 can be circulated in a parallel or countercurrent flow with respect to the vapor generated by evaporation. Preferably, it is circulated in a countercurrent flow with respect to the vapor in the distillation apparatus. In other words, the aqueous solution or aqueous suspension SA2 is preferably introduced into the distillation apparatus, preferably into the evaporator, in a parallel or countercurrent flow with respect to the distilled solvent.

[0099] The aqueous solution or aqueous suspension SA2 may be circulated in one or more evaporators in series before obtaining the suspension S1. Preferably, it is circulated in a single evaporator.

[0100] The pressure during distillation is advantageously between 1 and 700 mbar absolute pressure (1 mbar = 100 Pa). It is preferably less than 700 mbar absolute pressure, more preferably less than 600 mbar absolute pressure, more preferably less than 500 mbar absolute pressure, more preferably less than 400 mbar absolute pressure, more preferably less than 300 mbar absolute pressure, more preferably less than 200 mbar absolute pressure, more preferably less than 100 mbar absolute pressure, and even more preferably less than 50 mbar absolute pressure, and advantageously greater than 1 mbar absolute pressure. Absolute pressure corresponds to pressure relative to zero pressure (vacuum).

[0101] Generally, the pressure during distillation is preferably in the range of 10-700 mbar, preferably 20-700 mbar, preferably 40-700 mbar, more preferably 50-600 mbar, more preferably 50-500 mbar, more preferably 50-400 mbar, more preferably 50-300 mbar, more preferably 100-700 mbar, more preferably 200-700 mbar, more preferably 500-700 mbar, and more preferably 40-100 mbar.

[0102] In certain embodiments, step 2) includes step 2') (optionally performed) to assist in the evaporation of the solvent. Step 2') consists of raising the temperature of the aqueous solution or aqueous suspension SA2, in other words, the distillation according to step 2') is carried out under heating.

[0103] In some embodiments, in step 2), the aqueous solution or aqueous suspension SA2 is preferably heated to a temperature of 5°C to 95°C, preferably greater than 10°C to 60°C, and more preferably greater than 20°C to 40°C.

[0104] The heating during distillation can be carried out by various techniques. Examples, but not limited to, include heating with steam, heating with hot water, heating with electricity, heating by vapor compression, or heating using a heat pump. Therefore, the distillation apparatus may be a double-walled type in which a high-temperature heat-conducting fluid circulates between two walls.

[0105] The aqueous solution or aqueous suspension SA2 is preferably heated to a temperature of over 5°C to 95°C, preferably over 10°C to 60°C, and more preferably over 20°C to 40°C.

[0106] When the aqueous solution or aqueous suspension SA2 is heated, the temperature is preferably higher than the temperature in step 1).

[0107] The temperature of the aqueous solution or aqueous suspension SA2 is advantageously raised at a gradient of 0.1 to 10°C / hour, preferably 0.2 to 9°C / hour, more preferably 0.3 to 8°C / hour, and even more preferably 0.5 to 5°C / hour.

[0108] In some embodiments, the temperature of the aqueous solution or aqueous suspension SA2 is advantageously raised in a gradient of 10 to 150°C / hour, preferably 30 to 110°C / hour, more preferably 50 to 100°C / hour, and even more preferably 60 to 90°C / hour.

[0109] The temperature rise does not have to be constant throughout the entire process. For example, the aqueous solution or aqueous suspension SA2 may be heated at a rate of 5°C per hour for the first three hours, and then at a rate of 10°C per hour until the final temperature is reached.

[0110] According to another specific embodiment of the present invention, step 2) may include step 2'') (optionally performed) after or instead of step 2'), which helps to increase the productivity and profitability of the method of the present invention by promoting the crystallization of the sodium salt of the ATBS to the crystalline form. Step 2'') consists of lowering the temperature of the aqueous solution or aqueous suspension SA2.

[0111] The aqueous solution or aqueous suspension SA2 is advantageously cooled to a temperature of 5 to less than 95°C, preferably 10 to less than 60°C, more preferably 20 to less than 40°C, and even more preferably 10 to 40°C.

[0112] In some embodiments, step 2) further includes a cooling step.

[0113] The cooling step is advantageously carried out at a temperature of 5°C to 95°C, preferably greater than 10°C to 60°C, and more preferably greater than 10°C to 40°C.

[0114] In some embodiments, the temperature in the cooling step is reduced in a gradient of 0.1 to 8°C / hour, preferably 0.2 to 8°C / hour, more preferably 0.3 to 8°C / hour, and even more preferably 0.5 to 5°C / hour.

[0115] In some embodiments, the temperature of the cooling step is advantageously lower than the heating temperature of step 2) and / or step 1).

[0116] In some embodiments, the cooling step is performed on an aqueous solution or aqueous suspension SA2, and / or on a concentrated aqueous solution or aqueous suspension SA2, and / or on a suspension S1.

[0117] If the aqueous solution or aqueous suspension SA2 is cooled (step 2''), the temperature is advantageously lower than the temperature in step 2) and step 2') which is performed optionally.

[0118] According to a preferred embodiment, the temperature in step 2'') is the same as or lower than the temperature in step 1).

[0119] In some embodiments, no organic solvent or aqueous solution is added in step 2'' to obtain ATBS.Na crystals.

[0120] The temperature of the aqueous solution or aqueous suspension SA2 is advantageously decreased at a gradient of 0.1 to 8°C / hour, preferably 0.2 to 8°C / hour, more preferably 0.3 to 8°C / hour, and even more preferably 0.5 to 5°C / hour.

[0121] The rate of temperature decrease does not have to be constant throughout the entire process. For example, the aqueous solution or aqueous suspension SA2 may be cooled at a rate of 5°C per hour for the first 3 hours, and then at a rate of 8°C per hour until the final temperature is reached.

[0122] While the aqueous solution or aqueous suspension SA2 is being cooled, crystals of ATBS.Na are formed, and suspension S1 is obtained.

[0123] In certain embodiments, crystals of previously obtained ATBS.Na may be added during this step for the purpose of modifying the formation of suspension S1, which constitutes crystal seeding and allows for better control of the crystallization temperature, crystal size, particle size distribution, purity of the final product, and possibly yield. Crystals of ATBS sodium salt added by this method have a powder X-ray diffraction pattern that advantageously includes peaks at positions where 2θ(±0.1°) is 11.7°;12.2°;13.2°;13.5°;15.6°;16.8°;17.8°;18.5°;19.1°;20.6°;21.4°;23.3°;25.1°;25.8°;26.9°;29.1°;29.5°;31.0°;33.0°;33.6°;34.4°;35.2°;35.9°;37.1°;38.4°;39.6°;41.1°;42.9°;45.1°;46.0°;47.2°;47.6°.

[0124] According to a particular embodiment of the present invention, the solvent distilled in step 2) can be partially or entirely recycled to form the aqueous solution or aqueous suspension SA2 of step 1). In other words, the distilled solvent is advantageously at least partially recycled into the aqueous solution SA2.

[0125] According to another specific embodiment of the present invention, the distilled solvent may be partially or entirely recycled, with or without a pretreatment step, in step 4), which is optionally performed, to wash the sodium salt crystals of ATBS obtained after the solid-liquid separation of step 3).

[0126] The resulting suspension S1 advantageously contains 30 to 90% by weight of ATBS.Na crystalline form relative to the total weight of the suspension S1. Preferably, it contains 50 to 90% by weight, more preferably 30 to 80% by weight of the ATBS.Na crystalline form, and even more preferably 50 to 60% by weight.

[0127] In step 2), the pH is advantageously greater than 10, preferably greater than 11, more preferably greater than 12, and even more preferably 13-14.

[0128] Step 3 of the method for producing the crystalline form of ATBS sodium salt): The crystals of the sodium salt of ATBS contained in the suspension S1 obtained after step 2) are isolated in the solid-liquid separation step and become composition C1.

[0129] The solid-liquid separation step can be carried out using a variety of techniques. Examples, but not limited to, include the use of a centrifuge, decanter, filter press, agitated filter, belt filter, disc filter, or rotary drum filter. The solid-liquid separation is preferably carried out using a centrifuge. The solid-liquid separation may also be carried out by gravity sedimentation.

[0130] Step 3) is advantageously carried out at a temperature of -20 to 40°C, preferably -5 to 30°C.

[0131] After step 3) of solid-liquid separation, the ATBS sodium salt crystals are preferably not dried.

[0132] The content of ATBS sodium salt crystals in the isolated composition C1 is advantageously 40-99% by weight, preferably 60-99% by weight, more preferably 60-98% by weight, and even more preferably 80-99% by weight, relative to the weight of composition C1. The remainder of composition C1 may be water and / or the sodium salt of solubilized ATBS, and optionally the sodium salt base introduced in step 1).

[0133] After the completion of step 3), the crystal is characterized as an ATBS.Na crystal.

[0134] In a particular embodiment, all or part of the liquid phase obtained after the solid-liquid separation is used in the aqueous solution or aqueous suspension SA2 of step 1).

[0135] In step 4), the pH is advantageously controlled to 6-14, preferably 8-14, more preferably 10-14, even more preferably 12-14, and even more preferably 13-14.

[0136] Step 4 of the method for producing the crystalline form of ATBS sodium salt): In step 4), which may be performed as desired, composition C1, which contains ATBS.Na crystals obtained at the end of step 3), is washed with a washing solution.

[0137] The washing solution may be water, an aqueous solution of a sodium salt base (which may be saturated or unsaturated), or a solution of ATBS sodium salt (preferably the crystalline form of ATBS.Na) (which may be saturated or unsaturated), and preferably a saturated solution of ATBS sodium salt.

[0138] Examples of sodium salt solutions include solutions of sodium hydroxide, sodium carbonate, sodium bicarbonate, or mixtures thereof.

[0139] The cleaning solution may contain one or more organic solvents.

[0140] Advantageously, the cleaning solution does not contain organic solvents.

[0141] As already shown in Step 1), the organic solvent is advantageously selected from organic acids, amides, alcohols, ketones, ethers, esters, alkanes, halogenated hydrocarbon compounds, nitriles, or mixtures thereof. The organic solvent is preferably selected from acrylonitrile, isopropanol, acetic acid, or mixtures thereof. More preferably, the organic solvent is acrylonitrile.

[0142] In a particular embodiment, the composition C1 obtained at the end of step 3) is cleaned by spraying a cleaning solution onto the composition C1.

[0143] In a particular embodiment, the composition C1 obtained at the end of step 3) is washed by suspending the composition C1 in the washing solution.

[0144] The weight ratio of the cleaning aqueous solution to composition C1 obtained at the end of step 3) is advantageously 0.05:1 to 10:1, more preferably 0.1:1 to 5:1.

[0145] This washing step is advantageously carried out at a temperature of -5 to 40°C, preferably 0 to 30°C. Those skilled in the art know how to adjust the temperature so as not to solubilize the ATBS.Na crystals.

[0146] The ATBS.Na crystals obtained at the end of step 4), which is performed as desired, can be isolated from the washing solution in the form of composition C2 by a solid-liquid separation step.

[0147] The solid-liquid separation step can be carried out using a variety of techniques. Examples, but not limited to, include the use of vertical or horizontal centrifuges, decanters, filter presses, belt filters, disc filters, push filters, or rotary drum filters. The solid-liquid separation may also be carried out by gravity sedimentation.

[0148] In certain embodiments, all or part of the recovered washing solution may be reused in step 4), with or without the pretreatment step.

[0149] In a particular embodiment, all or part of the recovered washing solution may be used in the aqueous solution SA1 and / or aqueous solution or aqueous suspension SA2 of step 1), with or without a pretreatment step.

[0150] The pH of the washing solution in step 5 is advantageously controlled to 6-14, preferably 8-14.

[0151] Step 5 of the method for producing the crystalline form of ATBS.Na): In step 5), which may be performed as desired, composition C1 obtained at the end of step 3) or composition C2 obtained at the end of step 4) is dried.

[0152] The drying step can be carried out using a variety of techniques. Examples, but not limited to, include the use of all convection, conduction, or radiation drying techniques (fluidized bed dryers, through-bed dryers, belt conveyor drying, microwaves, heated agitated filters, high-frequency radiation, infrared radiation, and spraying).

[0153] The drying operation may be carried out under atmospheric pressure, or under reduced pressure.

[0154] The drying step may be carried out discontinuously (batch drying) or continuously.

[0155] Other steps in the method for producing the crystalline form of ATBS.Na: In the process of the above-mentioned manufacturing method, i.e., in steps 1) to 5), and notwithstanding the foregoing steps, at least one polymerization inhibitor may be introduced for the purpose of preventing possible polymerization of ATBS or a salt thereof. This inhibitor may be selected, not limited to, hydroquinone, paramethoxyphenol, phenothiazine, 2,2,6,6-tetramethyl(piperidine-1-yl)oxyl, 4-hydroxy-2,2,6,6-tetramethyl(piperidine-1-yl)oxyl, phenylenediamine derivatives, or mixtures thereof.

[0156] The inhibitor is preferably paramethoxyphenol or 4-hydroxy-2,2,6,6-tetramethyl(piperidine-1-yl)oxyl.

[0157] The amount of the inhibitor introduced is preferably 0.001% to 5% by weight, more preferably 0.01% to 1% by weight, relative to the amount of ATBS introduced in step 1).

[0158] The inhibitor may be introduced in one or more of the steps of the method. Preferably, an additional amount of the inhibitor is introduced in step 1). More preferably, the inhibitor is part of the aqueous solution SA1 introduced in step 1).

[0159] The above manufacturing method (steps 1) to 5)) may be carried out continuously or discontinuously (batch manufacturing).

[0160] Polymer composition The polymer is obtained from the crystalline form of ATBS.Na, and, advantageously, from at least one other monomer that can be selected from hydrophilic nonionic monomers, and / or hydrophilic anionic monomers, and / or hydrophilic cationic monomers, and / or hydrophilic zwitterionic monomers, and / or hydrophobic monomers, and mixtures thereof. The polymer may be a polymer or homopolymer of a plurality of different monomers.

[0161] Advantageously, the hydrophilic nonionic monomers that can be used in the present invention include, in particular, acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide (e.g., N,N-dimethylacrylamide or N,N-diethylacrylamide), N,N-dialkylmethacrylamide, alkoxylated acrylates, N-vinylpyrrolidone, N-methylol(meth)acrylamide, N-vinylcaprolactam, N-vinylformamide (NVF), N-vinylacetamide, N-vinylimidazole, N-vinyl The water-soluble vinyl monomers are selected from the group including cucinimide, acryloylmorpholine (ACMO), glycidyl methacrylate, vinyl acetate, glyceryl methacrylate, diacetone acrylamide, methacrylic anhydride, acrylonitrile, maleic anhydride, itaconamide, hydroxyalkyl (meth)acrylate, thioalkyl (meth)acrylate, isoprenol and its alkoxylated derivatives, hydroxyethyl (meth)acrylate and its alkoxylated derivatives, hydroxypropyl acrylate and its alkoxylated derivatives, and mixtures thereof. Among the nonionic monomers, the alkyl group is preferably C1-C5, and more preferably C1-C3. The alkyl group is preferably a linear alkyl group. Preferably, the hydrophilic nonionic monomer is acrylamide.

[0162] The water-soluble polymer preferably contains 0 to 99 mol%, preferably 40 to 95 mol%, and more preferably 45 to 90 mol%, of hydrophilic nonionic monomers.

[0163] Advantageously, apart from the crystalline form of ATBS.Na, the hydrophilic anionic monomers that can be used in the present invention can be selected from a large group. These monomers may have a vinyl functional group (preferably acrylic, malee, fuma, malon, itacone, or allyl) and may contain a carboxylic acid group, a phosphonic acid group, a phosphoric acid group, a sulfate group, or a sulfonic acid group, or other anionic charged groups. Examples of suitable monomers include acrylic acid; methacrylic acid; dimethylacrylic acid; itaconic acid; C1-C3 hemiesters of itaconic acid; acryloyl chloride; crotonic acid; maleic acid; fumaric acid; 3-acrylamido-3-methylbutanoic acid; and strong acid monomers having a sulfonic acid functional group or a phosphonic acid functional group, such as vinyl sulfonic acid, vinyl phosphonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-methylidenepropane-1,3-disulfonic acid, 2-sulfoethyl methacrylate, sulfopropyl methacrylate, sulfopropyl Examples include acrylic acrylate, allylphosphonic acid, ethylene glycol methacrylate phosphate, 2-acrylamido-2-methylpropanesulfonic acid (ATBS), 2-acrylamido-2-methylpropanedisulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, diethylallylphosphonate, carboxyethyl acrylate, etc.; water-soluble salts of these monomers, such as alkali metal salts (different from the crystalline form of ATBS.Na), alkaline earth metal salts, or ammonium salts; and mixtures thereof. Preferably, the hydrophilic anionic monomer is acrylic acid and / or a salt thereof.

[0164] The water-soluble polymer preferably contains 1 to 100 mol%, preferably 2 to 60 mol%, more preferably 5 to 30 mol%, and even more preferably 5 to 20 mol% of anionic hydrophilic monomers (different from the crystalline form of ATBS.Na). These proportions also include monomers of the crystalline form of ATBS.Na according to the present invention.

[0165] In certain embodiments of the present invention, the hydrophilic anionic monomer, other than the crystalline form of ATBS.Na, may be salinated.

[0166] According to the present inventors, chlorination refers to the -R of the anionic monomer. a The proton of at least one acidic functional group of the (=O)-OH type (in this case R represents P, S, or C) is replaced with a metal cation or an ammonium cation, -R a This means forming a (=O)-OX type salt (where X is a metal cation or an organic cation). In other words, the non-chlorinated form is the acidic form of the monomer, for example, in the case of a carboxylic acid functional group, R b -C(=O)-OH corresponds to the above monomer, while the chloride form of the monomer is R b -C(=O)-O - X + This corresponds to the form, X + This corresponds to an alkali cation or an organic cation. The chlorination of the acidic functional group of the branched-chain water-soluble polymer may be partial or whole. The chlorination form is advantageously equivalent to a salt of an alkali metal (Li, Na, K, etc.), an alkaline earth metal (Ca, Mg, etc.), or an ammonium (e.g., ammonium ion or tertiary ammonium). A preferred salt is a sodium salt.

[0167] The aforementioned chlorination may be carried out before, during, or after polymerization.

[0168] In certain embodiments of the present invention, the water-soluble polymer advantageously comprises 1 to 100 mol%, preferably 20 to 100 mol%, more preferably 50 to 100 mol%, and even more preferably 80 to 100 mol%, of a hydrophilic anionic monomer in chloride form. These proportions include the crystalline monomer of ATBS.Na according to the present invention.

[0169] Advantageously, the hydrophilic cationic monomers that can be used in the present invention are selected from monomers derived from vinyl-type units (preferably acrylamide, acrylic, allyl, or malein), and these monomers have a phosphonium or quaternary ammonium functional group. Particularly, and without limitation, these may be mentioned: diallyldialkylammonium salts such as diallyldimethylammonium chloride (DADMAC); acidified or quaternary salts of dialkylaminoalkyl (meth)acrylamide, e.g., methacrylamide-propyltrimethylammonium chloride (MAPTAC), acrylamide-propyltrimethylammonium chloride (APTAC); acidified or quaternary salts of dialkylaminoalkyl acrylates such as quaternary or chlorinated dimethylaminoethyl acrylate (DMAEA); quaternary or chlorinated dimethylaminoethyl acrylates These include acidified or quaternized salts of dialkylaminoalkyl methacrylates such as noethyl methacrylate (DMAEMA); acidified or quaternized salts of N,N-dimethylallylamine; acidified or quaternized salts of diallylmethylamine; acidified or quaternized salts of diallylamine; vinylamines obtained by hydrolysis (basic or acidic) of an amide group -N(R2)-CO-R1 (where R1 and R2 are independently hydrogen atoms or alkylated chains having 1 to 6 carbon atoms), such as vinylamines obtained from the hydrolysis of vinylformamide; vinylamines obtained by Hoffmann decomposition; and mixtures thereof. Advantageously, the alkyl group is C1 to C7, preferably C1 to C3, and may be linear, cyclic, saturated, or unsaturated. Preferably, it is quaternized dimethylaminoethyl acrylate.

[0170] Methods for preparing quaternized monomers, such as using an RX-type quaternizing agent in which R is an alkyl group and X is a halogen or sulfate, are well known to those skilled in the art.

[0171] The term "quaternary amine" refers to a molecule that can alkylate a tertiary amine.

[0172] The quaternizing agent may be selected from dialkyl sulfates containing 1 to 6 carbon atoms or alkyl halides containing 1 to 6 carbon atoms. Preferably, the quaternizing agent is selected from methyl chloride, benzyl chloride, dimethyl sulfate, or diethyl sulfate. In addition, the present invention also includes DADMAC, APTAC, and MAPTAC monomers in which the counterion is a sulfate ion, fluoride ion, bromide ion, or iodide ion instead of a chloride ion.

[0173] The water-soluble polymer preferably contains 0 to 20 mol%, more preferably 0 to 6 mol%, of hydrophilic cationic monomers.

[0174] Advantageously, the hydrophilic zwitterionic monomer may be a derivative of a vinyl-type unit (preferably acrylamide, acrylic, allyl, or malein), the monomer having a quaternary amine or ammonium functional group and a carboxylic acid (or carboxylate), sulfonic acid (or sulfonate), or phosphoric acid (or phosphate) functional group. In particular, and without limitation, may be mentioned, 2-((2-(acryloyloxy)ethyl)dimethylammonio)dimethylammonio)ethane-1-sulfonate, 3-((2-(acryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate, 4-((2-(acryloyloxy)ethyl)dimethylammonio)butane-1-sulfonate, [2-(acryloyloxy)ethyl](dimethylammonio)acetate Dimethylaminoethyl acrylate derivatives such as 2-((2-(methacryloyloxy)ethyl)dimethylammonio)ethane-1-sulfonate, 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate, 4-((2-(methacryloyloxy)ethyl)dimethylammonio)butane-1-sulfonate, and [2-(methacryloyloxy)ethyl](dimethylammonio)acetate. Dimethylaminopropylacrylamide derivatives such as noethyl methacrylate derivatives, 2-((3-acrylamidopropyl)dimethylammonio)ethane-1-sulfonate, 3-((3-acrylamidopropyl)dimethylammonio)propane-1-sulfonate, 4-((3-acrylamidopropyl)dimethylammonio)butane-1-sulfonate, [3-(acryloyloxy)propyl](dimethylammonio)acetate, 2-((3-methacrylamidopropyl)dimethylammonio)ethane-1-sulfonate, 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate, 4-((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate, and [3-(methacryloyloxy)propyl](dimethylammonio)acetate, as well as mixtures thereof.

[0175] Other hydrophilic zwitterionic monomers, particularly those described by the applicant in International Publication No. 2021 / 123599, may also be used.

[0176] The polymer preferably contains 0 to 20 mol%, more preferably 0 to 10 mol%, of hydrophilic zwitterionic monomers.

[0177] Distribution coefficient K ow Hydrophobic monomers with a value greater than 1 can also be used in the production of polymers according to the present invention. These are preferably selected from the following list: (i) C4~C 30 Alkyl chain, or (ii) arylalkyl (C4~C 30 Alkyl, C4~C 30 (iii) Aryl) chain, or (iv) Propoxylated chain, or (v) Ethoxylated chain, or (v) (meth)acrylic acid ester with ethoxylated and propoxylated chains; Alkylaryl sulfonate (C4~C 30 Alkyl, C4~C 30 Ariel); (i)C4~C 30 Alkyl chain, or (ii) arylalkyl (C4~C 30 Alkyl, C4~C 30 (iii) a propoxylated chain, or (iv) an ethoxylated chain, or (v) a monosubstituted or disubstituted (meth)acrylamide having an aryl chain, or a propoxylated chain; anionic or cationic monomer derivatives of (meth)acrylamide or (meth)acrylic acid having a hydrophobic chain; vinylpyridine, and mixtures thereof. The hydrophobic monomer may contain a halogen atom, such as chlorine.

[0178] Among these hydrophobic monomers: -The alkyl group is preferably C4~C 20 And more preferably C4~C8. C6~C 20 Alkyl groups are preferably linear, while C4-C5 alkyl groups are preferably branched. - The arylalkyl group is preferably C7~C 25And more preferably C7~C 15 That is the case. - The ethoxylated chain preferably contains 1 to 200, preferably 6 to 100, and more preferably 10 to 40 -CH2-CH2-O- groups. - The propoxylated chain preferably contains 1 to 50, more preferably 1 to 20 -CH2-CH2-CH2-O- groups.

[0179] Preferred hydrophobic monomers belonging to these classes include, for example, 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, erucyl(meth)acrylate, erucyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, 2-ethylhexylacrylate, C4~C 22 Itaconic acid hemiester, C4~C 22 Acidified or quaternary salts of dialkylaminoalkyl (meth)acrylates, C4~C 22 Acidified or quaternized salts of dialkylaminoalkyl(meth)acrylamide, vinylpyridine, acrylamide undecanoic acid, and mixtures thereof. - Cationic allyl derivatives of formula (I) or (II):

[0180] [ka]

[0181] During the ceremony: R: Independently, an alkyl chain containing 1 to 4 carbon atoms; R1: Alkyl or arylalkyl chain containing 8 to 30 carbon atoms; X: A halide selected from the group consisting of bromides, chlorides, iodides, and fluorides, and any negatively charged counterion; Furthermore, preferably, a (meth)acryloyl-type hydrophobic cationic derivative corresponding to formula (III):

[0182] [ka]

[0183] During the ceremony: - A represents O or N-R5 (preferably, A represents N-R5). - R2, R3, R4, R5, R6, R7: Independently, alkyl chains containing hydrogen or 1 to 4 carbon atoms. - Q: An alkyl chain containing 1 to 20 carbon atoms, - R8: Alkyl or arylalkyl chain containing 8 to 30 carbon atoms, - X: A halide selected from the group consisting of bromides, chlorides, iodides, and fluorides, and any negatively charged counterion.

[0184] The hydrophobic monomer contained in the aforementioned water-soluble polymer is preferably less than 5 mol%.

[0185] If the polymer contains a hydrophobic monomer, the hydrophobic monomer is present in an amount that maintains the water solubility of the polymer.

[0186] In the present invention, monomers having fluorescent functional groups may be used. Monomers having fluorescent functional groups can be detected by any suitable method, such as fluorescence photometry using a fixed-wavelength fluorometer. Generally, monomers having fluorescent functional groups are detected at excitation and emission maxima, which can be identified using a scanning fluorometer.

[0187] Monomers having fluorescent functional groups are selected from, for example, the following monomers: sodium or potassium styrenesulfonate, styrenesulfonic acid, vinylimidazole and its derivatives, 9-vinylanthracene and its derivatives, N-9-xanthenylacrylamide and its derivatives, allyldibenzosverenol and its derivatives, cinconicin and its derivatives, quininone and its derivatives, cinconinone and its derivatives, N,N-dimethyl-N-[3-[N'-(4-methoxynaphthalimide)]]propyl-N-(2-hydroxy-3-allyloxy)propylammonium hydroxide, and mixtures thereof.

[0188] When functionalized with allyl, vinyl, or acrylic double bonds, other fluorescent compounds can be used, such as pyranine and its derivatives, coumarin and its derivatives, quinolaxin and its derivatives, pinacyanol and its derivatives, xanthohydrol and its derivatives, dabusil and its derivatives, 3-hydroxy-2-methylene-3-(1-naphthyl)propionic acid and its derivatives, rhodamine and its derivatives, N-dibenzoberylacrylamide and its derivatives, naphthalene derivatives, fluorescein and its derivatives, pyrene and its derivatives, carbostyryl and its derivatives, pyrazoline and its derivatives, and mixtures thereof.

[0189] In a preferred embodiment, the polymer does not contain monomers having fluorescent functional groups.

[0190] In certain embodiments of the present invention, the water-soluble polymer may comprise at least one cyclic monomer having a hydrolyzable functional group. Advantageously, the cyclic monomer having a hydrolyzable functional group, or the cyclic monomer itself, may be selected from cyclic ketene acetals, thionolactones, and mixtures thereof.

[0191] The cyclic ketene acetal is advantageously selected from 2-methylene-1,3-dioxepane (MDO), 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4-phenyl-1,3-dioxolane (MPDL), 2-methylene-1,3,6-trioxocan (MTC), and mixtures thereof. Preferably, it is 2-methylene-1,3-dioxepane (MDO).

[0192] The thionolactone is advantageously selected from dibenzo[c,e]oxepin(7H)-5-thion (DOT), ε-thionocaprolactone, 3,3-dimethyl-2,3-dihydro-5H-benzo[e][1,4]dioxepin-5-thion (DBT), and mixtures thereof. Preferably, it is 3,3-dimethyl-2,3-dihydro-5H-benzo[e][1,4]dioxepin-5-thion.

[0193] In certain embodiments of the present invention, the water-soluble polymer may comprise at least one group having an LCST.

[0194] According to the general knowledge of those skilled in the art, a group having an LCST corresponds to a group whose water solubility at a given concentration is modified above a certain temperature and depending on the salt concentration. This is a group that has a heating transition temperature that determines its lack of affinity to the solvent. This lack of affinity to the solvent results in opacity or loss of transparency, which can be due to precipitation, aggregation, gelation, or viscosity increase of the medium. The lowest transition temperature is known as the LCST (lower critical solution temperature). At each concentration of a group having an LCST, a heating transition temperature is observed. It is higher than the LCST, which is the minimum point on the curve. Below this temperature, the polymer is soluble in water, and above this temperature, the polymer loses its solubility in water.

[0195] In certain embodiments of the present invention, the water-soluble polymer may contain at least one group having UCST.

[0196] According to the general knowledge of those skilled in the art, a group having UCST corresponds to a group whose water solubility at a given concentration is modified below a certain temperature and depending on the salt concentration. This is a group that has a cooling transition temperature that determines the lack of affinity with the solvent. The lack of affinity with the solvent results in opacity or loss of transparency, which can be due to precipitation, aggregation, gelation, or viscosity increase of the medium. The highest transition temperature is known as UCST (upper critical solution temperature). At each concentration of a group having UCST, a cooling transition temperature is observed. It is lower than the UCST, which is the maximum point on the curve. Above this temperature, the polymer is soluble in water, and below this temperature, the polymer loses its solubility in water.

[0197] The amounts of different monomers are adjusted by those skilled in the art so as not to exceed 100 mol% when producing the water-soluble polymer.

[0198] Water-soluble polymers

[0199] The 2-acrylamido-2-methylpropanoic acid used to obtain the water-soluble polymer is, advantageously, at least 50 mol%, preferably 70-100 mol%, of which is the crystalline form of the sodium salt before polymerization. More preferably, 100 mol% of the ATBS is the crystalline form of the sodium salt.

[0200] In certain embodiments of the present invention, the water-soluble polymer is advantageously obtained from 1 to 99 mol%, preferably 2 to 60 mol%, more preferably 5 to 30 mol%, and even more preferably 5 to 20 mol%, of anionic hydrophilic monomers, the proportions of which include monomers of the crystalline form of ATBS.Na.

[0201] In certain embodiments of the present invention, the water-soluble polymer may contain 1 to 100 mol%, preferably 1 to 99 mol%, more preferably 2 to 60 mol%, and more preferably 3 to 50 mol%, of which at least 50 mol%, preferably 70 to 100 mol%, of the ATBS used is the crystalline form of the sodium salt, and more preferably 100 mol%, of the ATBS used is the crystalline form of the sodium salt.

[0202] In certain embodiments of the present invention, the water-soluble polymer comprises 1 to 99 mol%, preferably 40 to 95 mol%, more preferably 45 to 90 mol%, of a nonionic hydrophilic monomer; and 1 to 99 mol%, preferably 5 to 60 mol%, more preferably 10 to 55 mol%, of ATBS, wherein at least 50 mol%, preferably 70 to 100 mol%, of the ATBS used is the crystalline form of the sodium salt. More preferably, 100 mol%, of the ATBS used is the crystalline form of the sodium salt.

[0203] In a preferred embodiment of the present invention, the water-soluble polymer is a polymer based on acrylamide and ATBS, wherein at least 50 mol% of the ATBS used is the crystalline form of the sodium salt. Preferably, the water-soluble polymer is a polymer consisting of acrylamide, acrylic acid, and ATBS, wherein at least 50 mol% of the ATBS used is the crystalline form of the sodium salt.

[0204] The polymer may be partially or completely hydrolyzed after treatment.

[0205] In preferred embodiments of the present invention, the water-soluble polymer is a polymer of ATBS, which is the crystalline form of the sodium salt, and a salt of acrylic acid, or a polymer of ATBS, which is the crystalline form of the sodium salt, and a hydrolyzable nonionic monomer.

[0206] The hydrolyzable nonionic monomer is preferably selected from acrylamide; methacrylamide; N-mono-derivatives of acrylamide or methacrylamide; N,N-derivatives of acrylamide or methacrylamide; and esters of acrylic acid or methacrylic acid. Preferably, it is acrylamide.

[0207] According to the present invention, the water-soluble polymer may have a linear, branched, crosslinked, star-shaped, or comb-shaped structure. These structures can be obtained, according to the general knowledge of those skilled in the art, for example, by incorporating initiators, transfer agents, polymerization techniques such as RAFT (reversible addition-cleavage chain transfer), NMP (nitroxide-mediated polymerization), or ATRP (atomic transfer radical polymerization), or by selecting the concentration of structural monomers.

[0208] The water-soluble polymer may be further structured with a branching agent. A structured polymer is a non-linear polymer having side chains such that, when dissolved in water, the polymer exhibits a high degree of entanglement, resulting in very high low-gradient viscosities.

[0209] The aforementioned branching agent is advantageous in that, - A structural agent may be selected from the group including polyethylene unsaturated monomers (having at least two unsaturated functional groups), vinyl functional groups, particularly allyl functional groups or acrylic functional groups, for example, methylenebisacrylamide (MBA), triallylamine, or tetraallylammonium chloride, or 1,2-dihydroxyethylenebis-(N-acrylamide). - A monomer having at least two epoxy functional groups - A monomer having at least one unsaturated and one epoxy functional group, - Transport agents such as polyperoxides, polyazoids, and polymercaptant polymers, as well as macroinitiators such as polyols. - Functionalized polysaccharides, - Water-soluble metal composite composed of the following: * Examples include, but are not limited to, metals with a valency greater than 3, such as aluminum, boron, zirconium, or titanium, and * Ligands having a hydroxyl functional group, Selected from.

[0210] The amount of branching agent in the water-soluble polymer is advantageously less than 40,000 ppm, preferably less than 10,000 ppm, and more preferably less than 5,000 ppm, relative to the total weight of the monomers of the water-soluble polymer.

[0211] In a particular embodiment, the amount of branching agent is equal to at least 0.1 ppm, preferably at least 1 ppm, more preferably at least 10 ppm, more preferably at least 100 ppm, and even more preferably at least 1000 ppm, relative to the total weight of the monomers of the water-soluble polymer.

[0212] If the water-soluble polymer contains a branching agent, the polymer may remain water-soluble. Those skilled in the art will know how to adjust the amount of branching agent, and possibly the amount of transfer agent, required to obtain this result.

[0213] In a preferred embodiment of the present invention, the water-soluble polymer is a water-soluble polymer that does not contain a branching agent.

[0214] In certain embodiments, the water-soluble polymer may include a transfer agent.

[0215] The aforementioned transport agent is preferably methanol; isopropyl alcohol; sodium hypophosphate; calcium hypophosphate; magnesium hypophosphate; potassium hypophosphate; ammonium hypophosphate; formic acid; sodium formate; calcium formate; magnesium formate; potassium formate; ammonium formate; 2-mercaptoethanol; 3-mercaptopropanol; dithiopropylene glycol; thioglycerol; thioglycolic acid; thiohydroacrylic acid; thiolactic acid; thiomalic acid; cysteine; aminoethanethiol; thioglycolate; allyl phosphite; allyl mercaptans such as n-dodecyl mercaptan; sodium methallysulfonate; calcium methallylsulfonate; magnesium methallylsulfonate; potassium methallylsulfonate; ammonium methallylsulfonate; trialkyl(C) 12 ~C 15 ) Selected from alkyl phosphites such as phosphites, dioleylhydrogen phosphites, and dibutyl phosphites; dialkyldithiophosphates such as dioctylphosphonates; tertiary nonyl mercaptans; 2-ethylhexyl thioglycolates; n-octyl mercaptans; n-dodecyl mercaptans; tertiary dodecyl mercaptans; iso-octyl thioglycolates; 2-ethylhexyl thioglycolates; 2-ethylhexyl mercaptoacetates; polythiols; and mixtures thereof. Preferably, sodium hypophosphate or sodium formate.

[0216] The amount of the transfer agent in the water-soluble polymer is advantageously 0 to 100,000 ppm, preferably 0 to 10,000 ppm, more preferably 0 to 1,000 ppm, and even more preferably 0 to 100 ppm, relative to the total weight of the monomers of the polymer. If present, the transfer agent corresponds to at least 0.1 ppm, preferably at least 1 ppm, relative to the total weight of the monomers of the polymer.

[0217] In a particular embodiment of the present invention, the water-soluble polymer does not contain a transfer agent.

[0218] Generally speaking, the aforementioned water-soluble polymers do not require the development of any specific polymerization method. In fact, they may be obtained using any polymerization technique well known to those skilled in the art. These include solution polymerization; gel polymerization; precipitation polymerization; emulsion polymerization (aqueous or reversed phase); suspension polymerization; reactive extrusion polymerization; water-in-water polymerization; or micelle polymerization.

[0219] The polymerization is generally radical polymerization, preferably by reverse-phase emulsion polymerization or gel polymerization. Radical polymerization includes free radical polymerization using UV initiators, azo initiators, redox initiators, or thermal initiators, as well as controlled radical polymerization (CRP) or matrix polymerization techniques.

[0220] Controlled radical polymerization technologies are not limited to, but include iodine transfer polymerization (ITP), nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP), reversible addition-cleavage chain transfer (RAFT) polymerization including MADIX (Macromolecular Design by Interchange of Xanthates) technology, various modifications of organometallic radical polymerization (OMRP), and organic heteroatom-mediated radical polymerization (OHRP).

[0221] As previously described, the water-soluble polymer may be partially or completely hydrolyzed after treatment.

[0222] The post-hydrolysis treatment is a hydrolysis reaction of the polymer after the polymer has been formed by the polymerization of the monomers. This step involves reacting the hydrolyzable functional groups of the monomer, preferably nonionic functional groups, and more preferably amide or ester functional groups, with a hydrolyzing agent. This hydrolyzing agent may be an enzyme, an ion exchange resin, or a Brønsted metal acid (e.g., a hydrohalic acid) or a Brønsted base (e.g., an alkali metal hydroxide or an alkaline earth metal hydroxide). Preferably, the hydrolyzing agent is a Brønsted base. In the process of this step of post-hydrolysis of the water-soluble polymer, the number of carboxylic acid functional groups increases. In fact, carboxylate groups are generated by the reaction of the base with the amide or ester functional groups present in the water-soluble polymer.

[0223] If the production of the water-soluble polymer includes a drying step such as spray drying, drum drying, microwave drying, or drying in a fluidized bed, the polymer may be in the form of a liquid, gel, or solid.

[0224] The water-soluble polymer advantageously has a weight-average molecular weight of at least 500,000 g / mol, preferably 500,000 to 40 million g / mol, and more preferably 5 million to 30 million g / mol. The molecular weight is determined by the weight-average molecular weight.

[0225] The weight-average molecular weight is determined by the intrinsic viscosity of the polymer. The intrinsic viscosity may be measured by methods known to those skilled in the art, and can be calculated from reduced viscosity values ​​for different polymer concentrations by a graphing method consisting of plotting the reduced viscosity value (y-axis) against the concentration (x-axis) and extrapolating the curve to zero concentration. The intrinsic viscosity value is plotted on the y-axis, or the least squares method is used. Subsequently, the molecular weight can be determined using the Mark-Houwink formula: [η]=KM α In the formula, [η] represents the intrinsic viscosity of the polymer as determined by the solution viscosity method. K represents the experimental constant. M represents the molecular weight of the polymer. α represents the Mark-Houwink coefficient. K and α vary depending on the specific polymer-solvent system.

[0226] Fragmentation fluid The present invention relates to a fragmentation fluid comprising an aqueous phase, at least one proppant, and at least one water-soluble polymer, wherein the ATBS is in the crystalline form of ATBS.Na as described above before polymerization.

[0227] The aqueous phase is preferably selected from seawater, brine, and fresh water, and is preferably brine.

[0228] Brine is a solution containing water and organic or inorganic salts. Examples of the salts may include monovalent salts, divalent salts, trivalent salts, and mixtures thereof. Preferably, the brine contains at least 1000 mg / L of salts, preferably at least 5000 mg / L, more preferably at least 10,000 mg / L, and even more preferably at least 50,000 mg / L of salts, and even more preferably, the brine is saturated with salts.

[0229] The proppant can be selected from a non-limiting list including sand, ceramics, bauxite, glass beads, and resin-impregnated sand.

[0230] Preferably, the amount of proppant in the fragmentation fluid is 0.5 to 40% by weight, preferably 1 to 25% by weight, more preferably 1.5 to 20% by weight based on the total weight of the fragmentation fluid.

[0231] Advantageously, the fragmentation fluid contains a water-soluble polymer obtained from the crystalline form of ATBS.Na in an amount of 0.001% to 1% by weight, preferably 0.002% to 0.2% by weight based on the total weight of the fragmentation fluid.

[0232] The fragmentation fluid is, for example, as described in document SPE 152596, such as: - Clay swelling inhibitors such as potassium chloride or choline chloride, and / or - Biocides to prevent the growth of bacteria, especially sulfate-reducing bacteria. Sulfate-reducing bacteria can form viscous clumps that reduce pathway surfaces. Examples include glutaraldehyde, which is the most commonly used, or in practice formaldehyde, or isothiazolinone, and / or - Deoxidizing agents such as ammonium bisulfite to prevent the destruction of other components due to oxidation and corrosion of the press-fit pipe, and / or - N,N-dimethylformamide is preferred as a corrosion-preventive additive to protect the pipe from oxidation by residual oxygen, and / or - Lubricants such as petroleum distillates, and / or - Iron chelating agents such as citric acid, EDTA (ethylenediaminetetraacetic acid), phosphonates, and / or - Scale inhibitors such as phosphates, phosphonates, polyacrylates, or ethylene glycol. This may include other compounds known to those skilled in the art, such as the following.

[0233] Prior to being used in the crushing fluid, the water-soluble polymer according to the present invention may be in various solid or liquid forms. Preferably, it may be in the form of a powder, a water-in-oil reversed-phase emulsion, an aqueous multiphase fine particle suspension, or an oily multiphase fine particle suspension.

[0234] Method for manufacturing crushed fluid The present invention also relates to a method for producing a fracturing fluid by adding at least one water-soluble polymer (as described above) of the crystalline form of ATBS.Na to water or brine, wherein the water-soluble polymer is present before the formation of the fracturing fluid: - In powder form, - Or in the form of a water-in-oil reversed-phase emulsion, - Or in the form of an aqueous or oil-based multiphase fine particle suspension.

[0235] A method for producing a crushing fluid according to the present invention preferably includes the step of adding at least one propane to the fluid, as previously described.

[0236] If the water-soluble polymer added to the crushing fluid is in powder form before the formation of the crushing fluid, the average particle size of the polymer particles is advantageously less than 1.5 millimeters, preferably less than 850 micrometers, and more preferably less than 200 micrometers. The average particle size of the water-soluble polymer particles is advantageously greater than 5 μm.

[0237] The average particle size of the water-soluble polymer particles is the average particle size of the maximum dimensions, which is, for example, the diameter in the case of spherical particles. The average particle size is advantageously measured using a laser measuring device employing the prior art, which is part of the knowledge of those skilled in the art. For example, a Malvern Mastersizer, such as the MS2000, can be used for this purpose. Such devices can be used to measure the particle size distribution of particles in a liquid medium or in solid form by laser diffraction.

[0238] If the water-soluble polymer according to the present invention is a solid, it can be partially or completely dissolved in water using a polymer preparation unit such as a polymer slicing unit (PSU) disclosed in European Patent No. 2203245.

[0239] If the water-soluble polymer added to the crushing fluid is in the form of a water-in-oil reversed-phase emulsion before the formation of the crushing fluid, the concentration of the water-soluble polymer in the emulsion is preferably 5 to 60% by weight, more preferably 15 to 40% by weight, relative to the weight of the emulsion.

[0240] In preferred embodiments of the present invention, the water-in-oil reverse-phase emulsion may contain 0.01% to 70% by weight, preferably 5% to 20% by weight, of organic and / or inorganic salts relative to the weight of the emulsion. The salts may be selected from an unlimited list of sodium chloride, sodium sulfate, sodium bromide, ammonium sulfate, ammonium chloride, lithium chloride, lithium bromide, potassium chloride, potassium bromide, magnesium sulfate, aluminum sulfate, and mixtures thereof. Preferred salts are ammonium chloride and ammonium sulfate.

[0241] If the water-soluble polymer added to the crushing fluid is in the form of an aqueous multiphase fine particle suspension before the formation of the crushing fluid, the suspension is preferably: - At least one water-soluble polymer in the form of solid particles with an average particle size of 5 to 500 μm, in an amount of 15 to 60% by weight; - 15-45% by weight of at least one alkali metal salt and / or at least one alkaline earth metal salt; - At least one thickening agent other than the aforementioned water-soluble polymer; - At least 10% by weight of water, The suspension contains a Brookfield viscosity of 500 to 20,000 cps at a temperature of 20°C; and The suspension is 1.1-2 kg·L -1 It has a density of .

[0242] If the water-soluble polymer added to the crushing fluid is in the form of an oily multiphase fine particle suspension before the formation of the crushing fluid, the suspension is preferably: - At least one water-soluble polymer in the form of solid particles with an average particle size of 5 to 500 μm, in an amount of 15 to 60% by weight; - At least one thickening agent other than the aforementioned water-soluble polymer; - At least 10% by weight of oil, The suspension contains a Brookfield viscosity of 500 to 20,000 cps at a temperature of 20°C; and The suspension is 0.6 to 1.4 kg·L-1 has a density of

[0243] The Brookfield viscosity is measured using a Brookfield apparatus fitted with an LV module, the module being rotatable, for example, at a speed of 30 rpm, and the measurement being advantageously carried out at 20 °C. The density is measured at 20 °C, a pressure of 1 atm, i.e. 101,325 Pa.

[0244] Method for hydraulic fracturing of unconventional underground oil or gas reservoirs The present invention also relates to a method for hydraulic fracturing of an unconventional underground oil or gas reservoir, the method comprising producing a fracturing fluid as already described and injecting said fracturing fluid into the underground reservoir.

[0245] The injection is carried out under pressure in order to form fracture sections distributed along the entire length of the production well.

[0246] If desired, at least one oxidizing compound and / or at least one surfactant is injected into the reservoir before, during or after the formation of the fracture sections.

[0247] Injecting a surfactant helps to eliminate the viscosity created by the polymer by inhibiting hydrophobic intermolecular interactions, while injecting an oxidizing compound destroys the polymer. In either case, injection can re-establish a fluid viscosity close to that of water.

[0248] Examples of oxidizing compounds include bleaching agents (aqueous solutions of hypochlorites), hydrogen peroxide, ozone, chloramine, persulfates, permanganates, and perchlorates.

[0249] The chemical nature of the surfactant is not critical. It may be anionic, non-ionic, amphoteric, zwitterionic, and / or cationic. The surfactant compounds of the present invention preferably have an anionic charge.

[0250] Preferably, the surfactant used is selected from anionic surfactants and their zwitterions, selected from the group including derivatives such as alkyl sulfate, alkyl ether sulfate, aryl alkyl sulfate, aryl alkyl ether sulfate, alkyl sulfonate, alkyl ether sulfonate, aryl alkyl sulfonate, aryl alkyl ether sulfonate, alkyl phosphate, alkyl ether phosphate, aryl alkyl phosphate, aryl alkyl ether phosphate, alkyl phosphonate, alkyl ether phosphonate, aryl alkyl phosphonate, aryl alkyl ether phosphonate, alkyl carboxylate, alkyl ether carboxylate, aryl alkyl carboxylate, aryl alkyl ether carboxylate, polyalkyl ether, aryl alkyl polyether, etc.

[0251] An alkyl chain is defined as a branched or unbranched chain having 6 to 24 carbon atoms, which may or may not have multiple units and may optionally contain one or more heteroatoms (O, N, S). An arylalkyl chain is defined as a branched or unbranched chain having 6 to 24 carbon atoms, which contains one or more aromatic rings and optionally contains one or more heteroatoms (O, N, S).

[0252] For reasons of cost, stability, and availability, the most commonly used surfactants are sulfonate or sulfate types in the form of alkali metal salts or ammonium salts.

[0253] A method for reducing friction of the fracturing fluid during hydraulic fracturing of unconventional underground oil or gas reservoirs. The present invention also relates to a method for reducing friction of a fracturing fluid in hydraulic fracturing operations of an unconventional underground oil or gas reservoir, comprising, as previously described, manufacturing the fracturing fluid and injecting the fracturing fluid into the underground reservoir.

[0254] Friction reduction reduces or eliminates losses (pressure) caused by friction during the injection of the crushing fluid.

[0255] The present invention and its advantages will become clear from the following embodiments. [Brief explanation of the drawing]

[0256] [Figure 1] Figure 1 shows the proton NMR spectrum of the ATBS needle crystal obtained according to Example 1. [Figure 2] Figure 2 shows the proton NMR spectrum of the ATBS.Na crystal obtained according to Example 2a. [Figure 3] Figure 3 shows the X-ray diffraction pattern of the ATBS crystal obtained according to Example 1. [Figure 4] Figure 4 shows the X-ray diffraction pattern of the ATBS.Na crystal obtained according to Example 2a. [Figure 5] Figure 5 shows the Fourier transform infrared spectrum of the ATBS crystal obtained according to Example 1. [Figure 6] Figure 6 shows the Fourier transform infrared spectrum of the ATBS.Na crystal obtained according to Example 2a. [Figure 7] Figure 7 shows the thermogram of the ATBS crystal obtained according to Example 1. [Figure 8] Figure 8 shows the thermogram of the ATBS.Na crystal obtained according to Example 2a. [Figure 9] Figure 9 shows the friction reduction rate of the polymer after post-hydrolysis treatment as a function of time. [Figure 10] Figure 10 shows the friction reduction rate of the terpolymer as a function of time. [Figure 11] Figure 11 shows the friction reduction rate of homopolymers as a function of time. [Figure 12] Figure 12 shows the friction reduction rate of the copolymer as a function of time. [Figure 13] Figure 13 shows an optical microscope image of the ATBS needle-shaped crystals obtained according to Example 1. [Figure 14] Figure 14 shows an optical microscope image of the ATBS.Na crystal obtained according to Example 2a. [Figure 15] Figure 115 shows the thermogram of the ATBS.Na crystal obtained according to Example 2b. [Figure 16] Figure 16 shows the thermogram of the ATBS.Na crystal obtained according to Example 2c. [Figure 17] Figure 17 shows a photograph of the ATBS.Na product obtained in solution according to Comparative Example 2b. [Figure 18] Figure 18 shows an optical microscope image of the ATBS.Na crystal obtained according to Comparative Example 2c. [Figure 19] Figure 19 shows an optical microscope image of the ATBS.Na crystal obtained according to Comparative Example 2d. [Figure 20] Figure 20 shows an optical microscope image of the ATBS.Na crystal obtained according to Comparative Example 2e. [Examples]

[0257] Example 1: 2-acrylamido-2-methylpropanesulfonic acid (ATBS) (A H ) synthesis 1522 g of acrylonitrile containing 0.4 wt% water is added to a 2000 ml reactor with a stirrer and double jacket, the mixture is stirred for 1 hour, and the temperature of the sulfonated mixture is maintained at -20°C by cooling with the double jacket of the reactor, and then 180 g of fuming sulfuric acid (18% oleum) with a H2SO4 titer of 104% is added.

[0258] 97 g of isobutylene is added to the sulfonated mixture at a rate of 1.6 g / min.

[0259] When adding isobutylene, the temperature of the mixture is controlled to 45°C. 2-acrylamido-2-methylpropanesulfonic acid particles precipitate from the mixture, and the solid content is approximately 20% by weight. The reaction mixture is filtered through a Buchner funnel and dried under reduced pressure at 50°C. The resulting solid is 2-acrylamido-2-methylpropanesulfonic acid (ATBS A H It is in the form of a very fine white powder.

[0260] Observation with an optical microscope (Figure 13) was performed using ATBS A H This indicates that the crystals have a needle-like shape.

[0261] Example 2a: 2-acrylamido-2-methylpropanesulfonate sodium salt (ATBS,Na A Na 2a) Formation of the aforementioned crystal form (the present invention) Add 439 g of 22% (by weight in water) sodium hydroxide aqueous solution to a 1000 ml reactor with a stirrer and double jacket. Add 452 g of ATBS A from Example 1. H Add this to the mixture mentioned earlier.

[0262] The mixture is stirred at 10°C for 30 minutes to form an aqueous solution SA2.

[0263] The aqueous solution SA2 is heated to 40°C under reduced pressure of 50 mbar for 20 minutes, then maintained at the same temperature under reduced pressure of 50 mbar for 30 minutes, and cooled to 10°C. The cooling time from 40°C to 10°C is 6 hours. A suspension S1 of ATBS.Na crystals is obtained. The suspension S1 is filtered using a Robatel vertical centrifuge. ATBS.Na A Na A solid of composition C1 containing 80% by weight of crystals of 2a is obtained.

[0264] Observation with an optical microscope (Figure 14) shows crystal A Na This indicates that 2a has both cylindrical and plate-like forms.

[0265] Example 2b: ATBS sodium salt (ATBS.Na A Na2b) Formation of the crystal form Except for distilling SA2 under 700 mbar, follow the procedure described in Example 2a to obtain ATBS.Na A Na Prepare crystal 2b.

[0266] Optical microscopy observation (Figure 15) shows crystal A obtained under these conditions. Na 2b is ATBS.Na A prepared in Example 2a. Na This indicates that it is identical to crystal 2a.

[0267] Example 2c: ATBS sodium salt (ATBS.Na A Na Formation of the crystal form in 2c) Except for shortening the cooling time to 3 hours and 45 minutes, the procedure described in Example 2a is followed, and ATBS.Na A Na Prepare 2c crystals.

[0268] Optical microscopy observation (Figure 16) shows that the crystals obtained under these conditions are ATBS.Na A Na This indicates that it is identical to crystal 2a.

[0269] Comparative Example 2a: Preparation of ATBS.Na crystals under atmospheric pressure (1 bar) (CE-A Na 2a) (Not obtained) The reaction is carried out according to the procedure described in Example 2a, except that SA2 is distilled under atmospheric pressure.

[0270] At the end of the cooling step, the aqueous solution SA2 does not form suspension S1, making it impossible to perform filtration or centrifugation to isolate the ATBS sodium salt crystals.

[0271] Comparative Example 2b: Preparation of ATBS sodium salt crystals (CE-A Na 2b) (Not obtained) The reaction was carried out according to the conditions described in Example 27 of U.S. Patent No. 6,331,647. Add 124 g of sodium hydroxide and 0.13 g of hydroquinone monomethyl ether to a 5000 ml reactor with a double jacket and a stirrer containing 400 g of water. Stir the medium until all of the sodium hydroxide is dissolved.

[0272] 632g ATBS A H Add the above mixture. Stir the mixture at 10°C for 30 minutes to form an aqueous solution of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid.

[0273] The resulting aqueous solution is filtered into a 3000 ml reactor equipped with an air purge tube and fitted with a distillation apparatus. The contents are heated and stirred while air is blown in below the water surface at 0.5 cubic feet per hour. The contents are heated to 50°C under reduced pressure of 933 mbar (approximately 700 milliliters of mercury). Once the water is removed, a yellowish, honey-like product is formed. The product is then transferred to a Robatel vertical centrifuge, but no solid is recovered.

[0274] Since a solid sample could not be obtained, observation using an optical microscope was not possible (Figure 17).

[0275] Comparative Example 2c: Preparation of ATBS sodium salt crystals (CE-A Na 2c) (Not obtained) The reaction was carried out according to the conditions described in Example 3 of the International Patent Application Publication No. 2013079507.

[0276] 100 g of ATBS.Na solution (16.77 wt%) is obtained according to Example 1 of International Publication No. 2013079507.

[0277] From the aforementioned ATBS.Na solution, 50 g of solvent (a mixture of acrylonitrile and methanol) is removed under reduced pressure (less than 700 mbar) at room temperature while introducing air into the ATBS.Na solution. ATBS.Na CE-A Na The 2c solid is obtained, filtered, washed with acrylonitrile / methanol, and then dried overnight at 50°C.

[0278] Optical microscopy observation (Figure 18) shows ATBS.Na CE-A Na This indicates that the dried solid of 2c does not correspond to the ATBS.Na crystals according to the present invention.

[0279] Comparative example 2d: ATBS.Na CE-A Na Preparation of 2d (not according to the present invention) The reaction is carried out according to the procedure described in Example 2a, except that SA2 is distilled under 720 mbar.

[0280] ATBS.Na CE-A Na A solid of composition C1 containing 80% by weight of 2d crystals is obtained.

[0281] Optical microscopy observation (Figure 19) shows ATBS.Na CE-A Na This indicates that the 2d crystal does not correspond to the ATBS.Na crystal according to the present invention.

[0282] Comparative example 2e: ATBS.Na CE-A Na Preparation of 2e (not according to the present invention) The reaction is carried out according to the procedure described in Example 2a, except that the cooling time is set to 3 hours and 20 minutes.

[0283] ATBS.Na CE-A Na A solid of composition C1 containing 80% by weight of 2e crystals is obtained.

[0284] Optical microscopy observation (Figure 20) shows ATBS.Na CE-A Na This indicates that the 2e crystal does not correspond to the ATBS.Na crystal according to the present invention.

[0285] Example 3: Product ATBS A from Examples 1 and 2a H and ATBS.Na A Na NMR analysis of the 2a product ATBS A H and ATBS.Na A Na 2a is analyzed by proton nuclear magnetic resonance (NMR).

[0286] Dissolve the sample in D2O. The NMR instrument is a Bruker model with a frequency of 400 MHz and a 5 mm BBO BB- 1 H attached.

[0287] The two proton spectra (Figures 1 and 2) are similar, and the peak assignments are consistent with the molecular structures of ATBS or its sodium salt.

[0288] Example 4: ATBS A from Examples 1 and 2a H and ATBS.Na A Na Analysis of the 2a product by X-ray diffraction ATBS A H and ATBS.Na A Na Pre-crush the crystals of 2a to form a powder and analyze it by X-ray diffraction over an angular range of 10° to 90°. The instrument used is a Rigaku MiniFlex II diffractometer equipped with a copper wire source.

[0289] ATBS.Na A Na The crystals of 2a (Figure 4) show an X-ray diffraction pattern with characteristic peaks at positions where 2θ (±0.1°) is 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°.

[0290] ATBS A H The same peaks are not observed in the X-ray diffraction pattern of (Figure 3).

[0291] Example 5: ATBS A H and ATBS.Na A Na Fourier transform infrared measurement of 2a The apparatus used for Fourier transform infrared measurement is a Perkin Elmer Spectrum 100 with a single reflection ATR polarization accessory of 8 cm -1 accuracy.

[0292] ATBS A H and ATBS.Na A Na 2a is sieved through a 100 μm sieve. The particles remaining on the sieve are dried and placed in an oven at 60 °C for at least 4 hours.

[0293] Place several hundred milligrams of the solid on the diamond of the ATR accessory and manually apply pressure using the accessory.

[0294] The following bands (Figure 6) are characteristic of the crystal form of ATBS.Na A Na 2a: 3576 cm -1 、3485 cm -1 、3310 cm -1 、3079 cm -1 、2975 cm -1 、1658 cm -1 、1629 cm -1 、1543 cm -1 、1403 cm -1 、1321 cm -1 、1301 cm -1 、1205 cm -1 、1187 cm -1 、1163 cm -1 、1046 cm -1 、980 cm -1 、629 cm -1 .

[0295] ATBS A H does not show the same peaks in its infrared spectrum (Figure 5).

[0296] Example 6: Differential scanning calorimetry (DSC) of ATBS A H and ATBS.Na A Na 2a products The apparatus used is a Mettler DSC3.

[0297] ATBS A H and ATBS.Na A Na The crystals of 2a are analyzed under a nitrogen atmosphere with a heating gradient of 10°C / min. The initial temperature is 30°C, and the product is heated to 350°C.

[0298] ATBS A H The thermogram (Figure 7) shows a thermal effect at 195.15°C, a temperature generally considered to be the melting / decomposition point of ATBS. Subsequently, two exothermic decomposition phenomena are observed at 212.8°C and 288.4°C.

[0299] ATBS.Na A Na The thermogram of crystal 2a (Figure 8) shows four thermal phenomena at 49.8°C; 144.8°C; 169.8°C; and 254.3°C.

[0300] Example 7: Synthesis of polymers P1, P3, P5, and P7 of the present invention, and comparative polymers P2(CE), P4(CE), P6(CE), and P8(CE)

[0301] Example 7a: Post-hydrolysis treated polymer of ATBS / acrylamide (AM) P1 and P2 / P2c~e (CE)

[0302] Synthesis of polymer 1 P1 (the present invention) 761.9g of deionized water, 574.2g of acrylamide (50% by weight aqueous solution), 11.7g of urea, and 103.2g of ATBS.Na A Na Add the crystals from 2a to a 2000 mL beaker.

[0303] The resulting solution is cooled to 0-5°C and transferred to an adiabatic polymerization reactor. Nitrogen is bubbled in for 30 minutes to remove any trace amounts of dissolved oxygen.

[0304] Next, the following are added to the reactor: - 0.45 g of 2,2'-azobisisobutyronitrile, - 1.5 ml of a 5 g / L solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, - 1.5 ml of a 1 g / L solution of sodium hypophosphate, - 2.25 ml of 1 g / L solution of tert-butyl hydroperoxide, - 3.0 ml of a 1 g / L solution of ammonium sulfate and iron(II) hexahydrate (Mohr's salt).

[0305] After a few minutes, the nitrogen inlet is shut off and the reactor is closed. The polymerization reaction is carried out for 1 to 5 hours until the temperature reaches its peak. The resulting gel is cut into particles with a particle size of 1 to 6 mm.

[0306] Post-hydrolysis treatment of acrylamide: Next, 500.0 g of the previously cut gel is mixed with 22.5 g of 50% sodium hydroxide solution. The mixture is heated and maintained at a temperature of 90°C for 90 minutes.

[0307] Next, the gel is dried and pulverized to obtain polymer P1 in powder form.

[0308] Synthesis of comparative polymers P2 and P2c~P2e(CE) Polymer 2 (CE) was prepared according to the protocol described for P1, using ATBS.Na A Na 2a, 93.1g of ATBS A H And it is obtained by substituting with 36 g of a 50% by weight aqueous solution of sodium hydroxide.

[0309] Polymers P2c~P2e(CE) are prepared according to the protocol described for P1, using ATBS.Na A Na Prepare the solution by replacing 2a with CE-ANa2c, CE-ANa2d, and CE-ANa2e, respectively.

[0310] Example 7b: Acrylic acid (AA) / ATBS / AM terpolymer P3 (invention) and comparative polymers P4 / P4c~e (CE)

[0311] Polymer 3 P3 was prepared according to the protocol described for P1, using 1022 g of deionized water, 558.7 g of 50% acrylamide solution, 89 g of 50% sodium hydroxide solution, 80 g of glacial acrylic acid, 15.3 g of urea, and 125 g of ATBS.Na A Na Prepare using 2a.

[0312] Comparative polymer 4 P4(CE) was prepared according to the protocol described for P3, using ATBS.Na A Na 2a, 93.1g of ATBS A H And it is obtained by substituting with 36 g of a 50% by weight aqueous solution of sodium hydroxide.

[0313] Comparative polymers P4c to P4e (CE) were prepared according to the protocol described for P3, using ATBS.Na A Na Prepare the solution by replacing 2a with CE-ANa2c, CE-ANa2d, and CE-ANa2e, respectively.

[0314] Example 7c: Homopolymer P5 and comparative polymer P6 / P6c~e(CE) of the present invention

[0315] Polymer 5 P5 was prepared according to the protocol described for P1, using 800g of deionized water and 500g of ATBS.Na A Na Prepare using 2a.

[0316] Comparative polymer 6 P6(CE) was prepared according to the protocol described for P1, using ATBS.Na A Na 2a, 93.1g of ATBS A H And it is obtained by substituting with 36 g of a 50% by weight aqueous solution of sodium hydroxide.

[0317] Comparative polymers P6c~P6e(CE) were prepared according to the protocol described for P1, using ATBS.Na A Na Prepare the solution by replacing 2a with CE-ANa2c, CE-ANa2d, and CE-ANa2e, respectively.

[0318] Example 7d: Polymer P7 and comparative polymers P8 / P8c~e of the present invention for ATBS / AM

[0319] Polymer 7 P7 was prepared according to the protocol described for P1, using 1035 g of deionized water, 520.5 g of 50% acrylamide solution, 16.2 g of urea, and 285 g of ATBS.Na A Na Prepare using 2a.

[0320] Polymer 8 P8(CE) is prepared according to the protocol described for P1, using ATBS.Na A Na 2a, 93.1g of ATBS A H And it is obtained by substituting with 36 g of a 50% by weight aqueous solution of sodium hydroxide.

[0321] Polymers P8c~P8e(CE) are prepared according to the protocol described for P1, using ATBS.Na A Na Prepare the solution by replacing 2a with CE-ANa2c, CE-ANa2d, and CE-ANa2e, respectively.

[0322] Example 8: Preparation of crushing fluid

[0323] The previously prepared powdered polymer is dissolved in brine consisting of water, 85 g of sodium chloride (NaCl), and 33.1 g of calcium chloride (CaCl2·2H2O) per liter of brine, while stirring at a concentration of 10,000 ppm by weight.

[0324] The resulting polymer salt solution is then injected at a concentration of 0.05 pptg (parts per 1000 gallons) into the brine that will be recycled for the subsequent flow-loop test.

[0325] Example 9: Flow Loop Friction Reduction Test

[0326] To evaluate the friction reduction of each polymer, a flow loop tank was filled with 20 L of brine (the brine described in Example 5). Next, the brine was recirculated through the flow loop at a rate of 24 gallons per minute (1 gallon = 3.78541 liters). The polymer was added to the recirculated brine at a concentration of 0.5 pptg. The friction reduction rate was determined by measuring the pressure fluctuations within the flow loop.

[0327] The results are shown in Figures 9 to 12.

[0328] These results demonstrate that the pressurized fluid prepared using the polymer of the present invention provides improved friction reduction. Therefore, by preparing ATBS-based polymers P1, P3, P5, and P7 using ATBS.Na crystals of the present invention, the friction reduction properties of the fluid are further improved.

Claims

1. A fracturing fluid comprising at least one aqueous phase, propane, and at least one water-soluble polymer of 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, before polymerization, has 2θ of 11.7°; 12.2°; 13.2°; 13.5°; 15.6°; 16.8°; 17.8°; 18.5°; 19.1°; 20.6°; 21.4°; 23.3°; 25.1°; 25.8°; 26.9°; 29.1°; 29.5°; 31.0°; 33.0° A fractured fluid, which is the crystalline form of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid, having a powder X-ray diffraction pattern that includes peaks at the following positions: °; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.1°; 42.9°; 45.1°; 46.0°; 47.2°; 47.6°.

2. The crushing fluid according to claim 1, characterized in that at least 50 mol% of the 2-acrylamido-2-methylpropanesulfonic acid of the water-soluble polymer is the crystalline form of the sodium salt before polymerization.

3. The crushing fluid according to claim 1, characterized in that the water-soluble polymer is a polymer of the crystalline form of 2-acrylamido-2-methylpropanesulfonate sodium salt and at least one hydrophilic monomer selected from nonionic monomers, anionic monomers, cationic monomers, zwitterionic monomers, and mixtures thereof.

4. The crushing fluid according to any one of claims 1 to 3, characterized in that the water-soluble polymer contains 1 to 100 mol% of 2-acrylamido-2-methylpropanesulfonic acid, and at least 50 mol% of the 2-acrylamido-2-methylpropanesulfonic acid is the crystalline form of the sodium salt before polymerization.

5. The crushing fluid according to any one of claims 1 to 4, characterized in that the water-soluble polymer is a polymer of 2-acrylamido-2-methylpropanesulfonic acid, which is the crystalline form of the sodium salt, and a salt of acrylic acid, or an anionic polymer of 2-acrylamido-2-methylpropanesulfonic acid, which is the crystalline form of the sodium salt, and a hydrolyzable nonionic monomer.

6. The crushing fluid according to any one of claims 1 to 5, characterized in that it contains 0.001% to 1% by weight of a water-soluble polymer relative to the total weight of the crushing fluid.

7. A method for producing a crushed fluid according to any one of claims 1 to 6, comprising adding at least one water-soluble polymer of the crystalline form of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid to water or brine, wherein the water-soluble polymer is present before the formation of the crushed fluid: - In powder form, - Or in the form of a water-in-oil reversed-phase emulsion, - Or in the form of an aqueous or oil-based multiphase fine particle suspension, A method wherein the crystalline form of the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid is one of the following, and the powder X-ray diffraction pattern has peaks at positions where 2θ is 11.70°; 12.20°; 13.2°; 13.5°; 15.60°; 16.80°; 17.80°; 18.5°; 19.1°; 20.6°; 21.40°; 23.3°; 25.1°; 25.8°; 26.9°; 29.10°; 29.50°; 31.0°; 33°; 33.6°; 34.4°; 35.2°; 35.9°; 37.1°; 38.4°; 39.6°; 41.10°; 42.90°; 45.10°; 46.0°; 47.2°; 47.6°.

8. The method according to claim 7, characterized in that the water-soluble polymer is in powder form having an average polymer particle size of less than 1.5 millimeters before the formation of the crushing fluid.

9. The method according to claim 7, characterized in that the crushing fluid is in the form of a water-in-oil reversed-phase emulsion before the formation of the crushing fluid, and the concentration of the water-soluble polymer in the emulsion is preferably 5 to 60% by weight relative to the weight of the emulsion.

10. The method according to any one of claims 7 to 9, characterized in that the water-in-oil reverse-phase emulsion contains 0.01% to 70% by weight of an organic salt and / or an inorganic salt based on the weight of the emulsion.

11. The water-soluble polymer, before the formation of the crushed fluid, - At least one water-soluble polymer in the form of solid particles with an average particle size of 5 to 500 μm, present in an amount of 15 to 60% by weight; - 15 to 45% by weight of at least one alkali metal salt and / or at least one alkaline earth metal salt; - At least one thickening agent other than the water-soluble polymer of the present invention; - At least 10% by weight of water, It is in the form of an aqueous multiphase fine particle suspension containing, the suspension having a Brookfield viscosity of 500 to 20,000 cps at a temperature of 20°C; and The suspension is 1.1 to 2 kg / L. －１ The method according to any one of claims 7 to 10, characterized by having a density of the specified value.

12. The water-soluble polymer, before the formation of the crushed fluid, - At least one water-soluble polymer in the form of solid particles with an average particle size of 5 to 500 μm, present in an amount of 15 to 60% by weight; - At least one thickening agent other than the water-soluble polymer of the present invention; - At least 10% by weight of oil, It is in the form of an oily multiphase fine particle suspension containing, the suspension having a Brookfield viscosity of 500 to 20,000 cps at a temperature of 20°C; and The suspension is 0.6 to 1.4 kg / L －１ The method according to any one of claims 7 to 10, characterized by having a density of the specified value.

13. A method for hydraulic fracturing of an unconventional underground oil or gas reservoir, comprising: producing a fracturing fluid according to any one of claims 1 to 6; and injecting the fracturing fluid into the underground reservoir.

14. A method for reducing friction of a fracturing fluid in hydraulic fracturing operations of an unconventional underground oil or gas reservoir, comprising preparing a fracturing fluid according to any one of claims 1 to 6, and injecting the fracturing fluid into an underground reservoir.

Images