An alcohol-based polymer thickener, its preparation method and application

Abstract

This invention belongs to the field of oil and gas well reservoir stimulation technology, specifically relating to an alcohol-based polymer thickener, its preparation method, and its application. The alcohol-based polymer thickener, by mass percentage, comprises the following components: 40-55% copolymer polymer powder, 42-58% polyether alcohol, 1-1.5% organobentonite, and 1-1.5% surfactant; wherein the copolymer polymer powder is formed by polymerization of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine monomers as copolymer raw materials. This invention introduces multiple betaine groups and fluorinated groups into the molecular structure, combined with the polyether alcohol dispersed phase, to achieve high thickening properties and sand-carrying capacity at low concentrations. It also results in less residue and lower surface tension after gel breaking, reducing reservoir contamination and transportation costs, and is suitable for fracturing operations in unconventional oil and gas reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well reservoir stimulation technology, specifically relating to an alcohol-based polymer thickener, its preparation method, and its application. Background Technology

[0002] In the development of unconventional oil and gas resources, the stimulation of tight sandstone reservoirs relies on the technical approach of creating long fractures with high-viscosity fluids and supporting artificial fractures with high sand ratios. The performance of the fracturing fluid thickener directly determines the construction effect and the quality of reservoir protection.

[0003] Currently, the mainstream thickeners in the industry are mainly divided into two categories: (1) Crosslinked guar gum: Although this type of thickener can provide high viscosity, it will produce water-insoluble substances after breaking the gum. These insoluble substances are easy to block the micro-fractures and pore throats of the reservoir, causing irreversible reservoir damage and significantly reducing the oil and gas production after the modification; (2) Traditional polymers: Most of them are emulsion or suspension types, and their dispersed phase is mainly oil phase (such as white oil). When the amount of thickener is large, the oil phase is easy to remain in the reservoir, causing oil phase pollution; and the thickening effect of traditional polymers is limited at low concentrations, and a large amount of it is required to meet the sand carrying requirements, which not only increases the transportation cost, but also further aggravates the reservoir pollution risk. In order to solve the above problems, the industry has tried to develop alcohol-based thickener technology, but the existing solutions still have obvious defects:

[0004] Chinese invention patent CN112442352A discloses a "thickening agent with a mixed alcohol as the dispersed phase," which requires first synthesizing a polymer emulsion via a reverse emulsion method, and then compounding it with a mixed alcohol and a crosslinking agent. The system still contains white oil and relies on the crosslinking agent to achieve the target viscosity, increasing formulation complexity and cost. Chinese invention patent CN113292985A discloses an "ethylene glycol-dispersed alcohol-based guar gum fracturing fluid system," where the core thickener is still guar gum, failing to address the fundamental problem of reservoir contamination by guar gum residue after gel breaking. Chinese invention patent CN112375557B discloses an "alcohol-soluble slickwater system with an organic alcohol solvent," which does not specify the main polymer type of the drag-reducing agent, only evaluating the solution viscosity at a 0.1 wt% dosage, without addressing thickening performance and actual application dosage, thus failing to support fracturing operation requirements. Chinese invention patent CN111574989B... The publicly disclosed "high-temperature resistant alcohol-based fracturing fluid system" uses powdered polymer as the thickener. The solution preparation requires mixing high flash point alcohol with water (alcohol / water ratio 20-100%). The excessively high alcohol content leads to a significant increase in solution preparation costs and poor economic efficiency.

[0005] Therefore, developing an alcohol-based polymer thickener with excellent thickening effect at low concentrations, good temperature and shear resistance, little residue after gel breaking, no oil phase pollution, and controllable cost has become a key requirement in the field of unconventional oil and gas reservoir fracturing technology. Summary of the Invention

[0006] To address the problems of severe reservoir contamination, poor thickening effect at low concentrations, and high cost of existing thickeners, this invention provides an alcohol-based polymer thickener, its preparation method, and its application. This thickener, through molecular structure design (introducing polybetaine groups and fluorine-containing groups) and dispersion phase optimization (using polyether alcohol to replace the oil phase), achieves the technical goals of high thickening at low concentrations, easy gel breaking and backflow, and low reservoir damage, while simplifying the preparation process and reducing industrialization costs.

[0007] To overcome the shortcomings of the prior art, the present invention provides the following technical solution:

[0008] An alcohol-based polymer thickener, by mass percentage, comprises the following components: 40-55% copolymer polymer powder, 42-58% polyether alcohol, 1-1.5% organobentonite, and 1-1.5% surfactant; wherein the copolymer polymer powder is polymerized from acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine monomer as copolymer raw materials, and the mass fraction ratio of the three raw materials during polymerization is: 80-85% acrylamide, 10-12% 2-acrylamide-2-methylpropanesulfonic acid, and 3-10% unsaturated fluorinated betaine monomer.

[0009] Furthermore, the polyether alcohol is selected from one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, and polyethylene glycol 1000;

[0010] And / or, the surfactant is one or more of Span 60, Span 80, Tween 60, and Tween 80.

[0011] In addition, the present invention also provides a method for preparing the alcohol-based polymer thickener as described above, comprising the following steps: adding copolymer powder to polyether alcohol, then adding organic bentonite and surfactant, and stirring thoroughly for 0.5 to 1 hour to obtain the alcohol-based polymer thickener.

[0012] Furthermore, the method for preparing the copolymer powder includes the following steps:

[0013] S1. Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and unsaturated fluorinated betaine monomer to deionized water at 2 to 3 times the total mass of monomers, then add 5 to 10% of low molecular weight alcohol and 0.1 to 0.3% of surfactant, stir thoroughly to dissolve and obtain a mixture.

[0014] S2. At a temperature of 35~50℃, nitrogen gas is introduced into the mixture for 30 min, then an initiator accounting for 0.005~0.01% of the total mass of the monomer is added, the temperature is raised to 65~80℃, and the mixture is stirred for 4~6 h to obtain the crude product.

[0015] S3. The crude product is purified by precipitation with anhydrous ethanol. The purified product is dried to constant weight under vacuum at 30-50°C. After granulation, crushing and sieving through a 100-200 mesh sieve, the copolymer powder is obtained.

[0016] Further, the low molecular weight alcohol is selected from one or more of isobutanol, ethylene glycol, propylene glycol, butanediol, glycerol, glycerol, butanetetramethylol, pentanediol, and hexanediol; the surfactant is selected from one or more of sodium dodecyl sulfate, sodium dodecyl ether sulfate, ammonium lauryl sulfate, and sodium dodecylbenzene sulfonate; and the initiator is selected from one or more of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanopentanoic acid, and azobisisopropylimidazoline.

[0017] Further, in step S1, the method for preparing the unsaturated fluorinated betaine monomer includes the following steps:

[0018] (1) Synthesis of polytertiary amine intermediate: 3,3′-iminobis(N,N-dimethylpropylamine) and 25 mL of 25% sodium hydroxide solution were added to 50 mL of solvent and stirred thoroughly. Then, a solution of methacryloyl chloride dissolved in 50 mL of the same solvent was slowly added dropwise to the above mixture. The temperature was controlled and the mixture was stirred continuously during the addition. After the addition was completed, the reaction was continued for 1 h. The reactants were allowed to stand and separate into layers. The lower layer was washed, dried and desolventized to obtain the crude product of polytertiary amine intermediate.

[0019] (2) Purification of polytert-term amine intermediates: Add polymerization inhibitors to the crude polytert-term amine intermediates, perform vacuum distillation, and collect the fractions in the temperature range of 92~125℃ to obtain high-purity polytert-term amine intermediates;

[0020] (3) Quaternization reaction: The high-purity polytertiary amine intermediate was mixed with 100 mL of solvent and placed in an environment of 0~5℃. The mixture was stirred and nitrogen gas was introduced to purge the air. 100 mL of solvent was mixed with 3-fluoro-1,3-propanesulfonate lactone and slowly added dropwise to the above mixture at 0~5℃. After the addition was completed, the temperature was raised and the reaction was continued for 10 h. After the reaction was completed, the solid product was collected, washed and dried to obtain unsaturated fluorinated betaine monomer.

[0021] Further, in step (1), the solvent is selected from one of dichloromethane, chloroform, tetrahydrofuran, or diethyl ether; the amount of 3,3′-iminobis(N,N-dimethylpropylamine) is 0.1 mol; the amount of methacryloyl chloride is 0.12 mol; the stirring is magnetic stirring, and the temperature control range of the dropping stage is 0~5℃; the washing includes washing twice with distilled water and then washing twice with saturated brine; the drying is drying with anhydrous magnesium sulfate overnight; and the solvent removal treatment is rotary evaporation to remove the solvent.

[0022] Further, in step (2), the polymerization inhibitor is one of phenothiazine, hydroquinone, hydroquinone monomethyl ether or 2,6-di-tert-butyl-4-methylphenol;

[0023] In step (3), the solvent is one of acetone, acetonitrile, tetrahydrofuran or methanol; the amount of the high-purity polytert-amine intermediate is 0.1 mol, and the amount of 3-fluoro-1,3-propanesulfonate lactone is 0.31 mol; the dropping time is 1-2 h; the target temperature for heating after the dropping is completed is 40 °C; the solid product is collected by vacuum filtration, the washing is washing the filter cake multiple times with acetone, and the drying is drying in a vacuum drying oven at 40-50 °C until constant weight.

[0024] In addition, the present invention also provides an application of the alcohol-based polymer thickener described above in unconventional oil and gas reservoir fracturing.

[0025] Furthermore, the unconventional oil and gas reservoir is a tight sandstone reservoir; in application, an alcohol-based polymer thickener is dissolved in deionized water at a mass fraction of 1.0 wt% to form a high-viscosity liquid for fracturing operations. During the operation, the sand ratio is controlled at 30%, and the fracturing is carried out at 100℃ for 100 seconds. -1 Under shear rate conditions, the solution viscosity is >80 mPa·s after shearing for 90 min, and the viscosity of the broken gel is <5 mPa·s and the surface tension is <28 mN / m after gel breaking.

[0026] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0027] (1) Polyether alcohol is used to replace the oil phase dispersant, and there is no white oil residue; the polybetaine group and fluorine group contained in the polymer molecule give the degummed liquid good surface activity (surface tension <28mN / m), and the viscosity after degumming is <5mPa.s, which is easy to return to the ground and avoid residue clogging the reservoir. The gas testing effect is better than that of traditional thickeners.

[0028] (2) Through the hydrophobic association between fluorine-containing groups and betaine groups, a viscosity of >80 mPa·s can be achieved at a low concentration of 1.0 wt% (100℃, 100s). -1 After shearing for 90 minutes, the viscosity in Example 1 even reached 115.2 mPa·s, which is much higher than that of commercially available alcohol-based thickeners (comparative Example 1 is only 68.3 mPa·s), which can reduce the amount of thickener used and reduce transportation and construction costs;

[0029] (3) The sulfonic acid groups introduced into the polymer molecules improve the salt resistance and high temperature resistance, and can withstand high temperatures of 100℃ and 100s. -1It can maintain a stable thickening effect even under high shear conditions, and adapt to the complex geological conditions of unconventional reservoirs. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein:

[0031] Figure 1 The shear rheological curve of a 1.0 wt% solution of the alcohol-based polymer thickener in Example 1 is shown.

[0032] Figure 2 The shear rheological curve of a 1.0 wt% solution of alcohol-based polymer thickener in Example 5 is shown.

[0033] Figure 3 The shear rheological curve of a 1.0 wt% solution of alcohol-based polymer thickener in Example 3 is shown.

[0034] Figure 4 The shear rheology curve of a 1.0 wt% solution of alcohol-based polymer thickener in Example 6 is shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0036] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0037] According to a first aspect of the present invention, an alcohol-based polymer thickener is provided, comprising, by mass percentage: 40-55% copolymer polymer powder, 42-58% polyether alcohol, 1-1.5% organobentonite, and 1-1.5% surfactant; wherein the copolymer polymer powder is polymerized from acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine monomer as copolymer raw materials, and the mass fraction ratio of the three raw materials during polymerization is: 80-85% acrylamide, 10-12% 2-acrylamide-2-methylpropanesulfonic acid, and 3-10% unsaturated fluorinated betaine monomer.

[0038] This invention synthesizes a tritertiary amine monomer of acrylic acid, which reacts with a fluorinated propanesulfonic acid lactone to obtain a fluorinated triquaternary ammonium salt unsaturated monomer. This monomer is then copolymerized with acrylamide and AMPS to form a thickener macromolecule, which is then pulverized, ground, and dispersed in polyether alcohol to form an alcohol-based polymer thickener. This invention introduces polybetaine groups and fluorinated groups into the polymer molecule. On the one hand, this improves the thickening ability of the polymer molecule under low concentration conditions through hydrophobic association; on the other hand, it possesses good surface activity, making it easy for the depolymerized liquid to be returned to the formation after application. The presence of numerous sulfonic acid groups in the molecular structure also enhances the stability of the macromolecule. Using polyether alcohol as the dispersed phase increases the polymer content in the product, reduces dissolution time, and minimizes the damage to the reservoir from external fluids.

[0039] The alcohol-based polymer thickener provided by this invention solves the core problems of traditional thickeners, such as reservoir contamination, poor thickening effect at low concentrations, and high cost, through molecular structure design (containing fluorinated betaine groups + sulfonic acid groups) and dispersion phase optimization (polyether alcohol). When applied in unconventional oil and gas reservoir fracturing, it can achieve the technical goals of low damage, high thickening, and high sand carrying capacity, and has significant technical value and economic prospects.

[0040] In the above-mentioned alcohol-based polymer thickeners, as a preferred embodiment, the polyether alcohol includes, but is not limited to, one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, and polyethylene glycol 1000; the surfactant includes, but is not limited to, one or more of Span 60, Span 80, Tween 60, and Tween 80.

[0041] According to a second aspect of the present invention, a method for preparing the alcohol-based polymer thickener as described above is provided, comprising the following steps: adding copolymer powder to a polyether alcohol, then adding organobentonite and a surfactant, and stirring thoroughly for 0.5 to 1 hour to obtain the alcohol-based polymer thickener. The polymer thickener powder has a mass fraction of 40 to 55%, the polymeric alcohol has a mass fraction of 42 to 58%, the organobentonite has a mass fraction of 1 to 1.5%, and the surfactant has a mass fraction of 1 to 1.5%.

[0042] Specifically, the preparation method of the copolymer powder includes the following steps:

[0043] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to water at 2-3 times their total monomer mass. Then, 5-10% of a low-molecular-weight alcohol and 0.1-0.3% of a surfactant were added, and the mixture was stirred thoroughly to dissolve, yielding a solution. Nitrogen gas was bubbled into the solution at 35-50°C for 30 minutes. Then, 0.005-0.01% of an initiator was added, and the temperature was raised to 65-80°C. The mixture was stirred for 4-6 hours to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30-50°C to constant weight, and then granulated, pulverized, and sieved through a 100-200 mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups. During preparation, the total mass of the reactants is calculated as follows: the mass fraction of the three monomers is: acrylamide 80-85%, 2-acrylamide-2-methylpropanesulfonic acid 10-12%, and unsaturated fluorinated betaine acrylate monomer 3-10%.

[0044] In the above-mentioned method for preparing the copolymer powder, as a preferred embodiment, the low molecular weight alcohol includes, but is not limited to, one or more of isobutanol, ethylene glycol, propylene glycol, butanediol, glycerol, butanetetramethylol, pentanediol, and hexanediol. The surfactant includes, but is not limited to, sodium dodecyl sulfate, sodium dodecyl ether sulfate, ammonium lauryl sulfate, and sodium dodecylbenzene sulfonate. The initiator includes, but is not limited to, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanopentanoic acid, and azobisisopropylimidazoline.

[0045] In the above preparation method, as a preferred embodiment, the preparation method of the unsaturated fluorinated betaine monomer includes the following steps:

[0046] (1) Add 50 mL of dichloromethane to a beaker, then add 18.7 g (0.1 mol) of 3,3′-iminobis(N,N-dimethylpropylamine) and 25 mL of 25% sodium hydroxide solution to the beaker. After stirring thoroughly, transfer the mixture to a three-necked flask. Add 50 mL of dichloromethane to the beaker, then add 12.54 g (0.12 mol) of methacryloyl chloride. After stirring thoroughly, transfer the mixture to a constant pressure funnel. Stir magnetically, and control the temperature at 0-5℃. Slowly add the methacryloyl chloride to the three-necked flask through a constant pressure dropping funnel to allow the methacryloyl chloride to react with 3,3′-iminobis(N,N-dimethylpropylamine). After the addition is complete, continue the reaction for 1 h. Then pour the reactants into a separatory funnel and let them stand to separate into layers. Wash the lower layer twice with distilled water, then twice with saturated saline solution. Dry the mixture overnight with anhydrous magnesium sulfate, and remove the dichloromethane by rotary evaporation to obtain the polytert-amine intermediate. The synthetic reaction involves an amidation reaction between 3,3′-iminobis(N,N-dimethylpropylamine) and methacryloyl chloride to generate a multifunctional monomer containing a tertiary amine structure, as shown in the following reaction formula:

[0047] .

[0048] (2) Add crude polytertiary amine intermediate and a small amount of polymerization inhibitor to a Krüger distillation flask, distill under reduced pressure, and collect the fraction at 92-125℃ to obtain high-purity polytertiary amine intermediate.

[0049] (3) Add 0.1 mol of the polytert-amine intermediate and 100 mL of tetrahydrofuran (THF) to a three-necked flask, place it in an ice bath, start stirring, and purge air with nitrogen. Add 100 mL of THF and 0.31 mol of 3-fluoro-1,3-propanesulfonic acid lactone to a constant-pressure dropping funnel, and start adding dropwise at 0-5℃ for 1-2 h. After the addition is complete, remove the ice bath, slowly heat to 40℃, and continue the reaction for 10 h.

[0050] In the reaction, the polytertiary amine intermediate (a polyfunctional tertiary amine containing an unsaturated double bond) generated in the first step undergoes a quaternization reaction with 3-fluoro-1,3-propanesulfonate lactone (a fluorinated cyclic sulfonate ester on the right), introducing a fluorinated betaine structure at the tertiary amine site, ultimately generating an unsaturated fluorinated betaine monomer. The reaction formula is as follows:

[0051] ;

[0052] After the reaction was complete, the solid was collected by vacuum filtration. The filter cake was washed several times with acetone to remove unreacted reactants and impurities. The obtained solid product was dried to constant weight in a vacuum drying oven at 40–50°C.

[0053] In the above preparation method, as a preferred embodiment, the solvent used for the synthesis of the polytert-amine intermediate is one of dichloromethane, trichloromethane, tetrahydrofuran, or diethyl ether. The polymerization inhibitor used for the purification of the polytert-amine intermediate is one of phenothiazine, hydroquinone, hydroquinone monomethyl ether, or 2,6-di-tert-butyl-4-methylphenol; the solvent used for the quaternization reaction of the polytert-amine intermediate is one of acetone, acetonitrile, tetrahydrofuran, or methanol.

[0054] According to a third aspect of the present invention, an application of the alcohol-based polymer thickener described above in fracturing of unconventional oil and gas reservoirs is provided. Preferably, the unconventional oil and gas reservoir is a tight sandstone reservoir; in application, the alcohol-based polymer thickener is dissolved in deionized water at a mass fraction of 1.0 wt% to form a high-viscosity liquid for fracturing operations. During the fracturing process, the sand ratio is controlled at 30%, and the fracturing is carried out at 100°C for 100 seconds. -1 Under shear rate conditions, the solution viscosity is >80 mPa·s after shearing for 90 min, and the viscosity of the broken gel is <5 mPa·s and the surface tension is <28 mN / m after breaking the gel.

[0055] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0056] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0057] Example 1

[0058] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 80g, 10g, and 10g respectively. 300g of deionized water was added and stirred to form a homogeneous solution. 5g of ethanol and 0.3g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a mixture. Nitrogen gas was bubbled into the mixture at 35-50℃ for 30min, and then 0.01g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65-80℃, and the reaction was stirred for 4-6h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30-50℃ to constant weight, granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0059] Add 55g of polymer powder containing unsaturated fluorinated betaine groups to 43g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0060] Example 2

[0061] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 80 g, 12 g, and 8 g, respectively. 300 g of deionized water was added and stirred to form a homogeneous solution. 5 g of ethanol and 0.3 g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a crude product. Nitrogen gas was bubbled into the mixture at 35–50 °C for 30 min, and then 0.01 g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65–80 °C, and the reaction was stirred for 4–6 h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30–50 °C to constant weight, and then granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0062] Add 53g of polymer powder containing unsaturated fluorinated betaine groups to 45g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0063] Example 3

[0064] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 82 g, 12 g, and 6 g, respectively. 300 g of deionized water was added and stirred to form a homogeneous solution. 5 g of ethanol and 0.3 g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a mixture. Nitrogen gas was bubbled into the mixture at 35–50 °C for 30 min, and then 0.01 g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65–80 °C, and the reaction was stirred for 4–6 h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30–50 °C to constant weight, and then granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0065] Add 50g of polymer powder containing unsaturated fluorinated betaine groups to 48g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0066] Example 4

[0067] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 82 g, 12 g, and 6 g, respectively. 300 g of deionized water was added and stirred to form a homogeneous solution. 5 g of ethanol and 0.3 g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a mixture. Nitrogen gas was bubbled into the mixture at 35–50 °C for 30 min, and then 0.01 g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65–80 °C, and the reaction was stirred for 4–6 h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30–50 °C to constant weight, and then granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0068] Add 48g of polymer powder containing unsaturated fluorinated betaine groups to 50g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0069] Example 5

[0070] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 82 g, 12 g, and 6 g, respectively. 300 g of deionized water was added and stirred to form a homogeneous solution. 5 g of ethanol and 0.3 g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a mixture. Nitrogen gas was bubbled into the mixture at 35–50 °C for 30 min, and then 0.01 g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65–80 °C, and the reaction was stirred for 4–6 h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30–50 °C to constant weight, and then granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0071] Add 53g of polymer powder containing unsaturated fluorinated betaine groups to 45g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0072] Example 6

[0073] Acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine acrylate monomers were added to a flask, with the three monomers weighing 82 g, 11 g, and 7 g, respectively. 300 g of deionized water was added and stirred to form a homogeneous solution. 5 g of ethanol and 0.3 g of sodium dodecyl sulfate were added, and the mixture was stirred thoroughly to dissolve, yielding a mixture. Nitrogen gas was bubbled into the mixture at 35–50 °C for 30 min, and then 0.01 g of initiator azobisisobutyrazoline hydrochloride was added. The temperature was raised to 65–80 °C, and the reaction was stirred for 4–6 h to obtain a crude product. The crude product was purified by precipitation with anhydrous ethanol, dried under vacuum at 30–50 °C to constant weight, and then granulated, pulverized, and sieved through a 200-mesh sieve to obtain a powdered polymer containing unsaturated fluorinated betaine groups.

[0074] Add 42g of polymer powder containing unsaturated fluorinated betaine groups to 56g of polyethylene glycol 200, add 1g of organic bentonite and 1g of Span 60 surfactant, and stir thoroughly for 1 hour to obtain alcohol-based polymer thickener.

[0075] Performance testing:

[0076] The performance of the alcohol-based polymer thickeners prepared in Examples 1-6, as well as commercially available alcohol-based thickeners (Comparative Example 1) and white oil-based thickeners (Comparative Example 2), was tested. Test conditions: the samples were dissolved in deionized water at a concentration of 1.0 wt%, and the solutions were tested using a Hacker rheometer at 100°C for 100 seconds. -1 Shearing was performed at the shear rate for 90 min, and the viscosity of the solution was measured. After the gel was broken, the viscosity and surface tension of the broken liquid were measured. 20-40 mesh ceramsite with a sand ratio of 30% was used, and the sand carrying capacity was tested within 2 h. The results are shown in Table 1.

[0077] Table 1

[0078]

[0079] As shown in Table 1, the samples obtained according to the six embodiments of the present invention exhibit excellent shear resistance. The viscosity of the solution after shearing increases with the increase of the effective content in the alcohol-based thickener. In Example 1, the effective content reaches 55%, and the viscosity after shearing reaches 115.2 mPa·s, demonstrating good thickening effect. The viscosity of the comparative samples after shearing is less than 80 mPa·s. The viscosity of the gel-breaking solution of the example samples is less than 5 mPa·s, and the surface tension is less than 28 mN / m, meeting the requirements for field applications. The alcohol-based polymer thickener prepared by the present invention is superior to commercially available products in terms of thickening performance, gel-breaking performance, and sand-carrying performance, and has no risk of oil phase contamination, meeting the technical requirements of unconventional oil and gas reservoir fracturing.

[0080] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any technical solutions obtained by means of equivalent substitution or equivalent transformation should be covered within the protection scope of the present invention.

Claims

1. An alcohol-based polymer thickener, characterized in that, The product comprises, by mass percentage, the following components: 40-55% copolymer powder, 42-58% polyether alcohol, 1-1.5% organobentonite, and 1-1.5% first surfactant; wherein the copolymer powder is formed by polymerization of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and unsaturated fluorinated betaine monomer as copolymer raw materials, and the mass fraction ratio of the three raw materials during polymerization is: 80-85% acrylamide, 10-12% 2-acrylamide-2-methylpropanesulfonic acid, and 3-10% unsaturated fluorinated betaine monomer; The preparation method of the unsaturated fluorinated betaine monomer includes the following steps: (1) Synthesis of polytertiary amine intermediate: 3,3′-iminobis(N,N-dimethylpropylamine) and 25 mL of 25% sodium hydroxide solution were added to 50 mL of solvent and stirred thoroughly. Then, a solution of methacryloyl chloride dissolved in 50 mL of the same solvent was slowly added dropwise to the above mixture. The temperature was controlled and the mixture was stirred continuously during the addition. After the addition was completed, the reaction was continued for 1 h. The reactants were allowed to stand and separate into layers. The lower layer was washed, dried and desolventized to obtain the crude product of polytertiary amine intermediate. (2) Purification of polytert-term amine intermediates: Add polymerization inhibitors to the crude polytert-term amine intermediates, perform vacuum distillation, and collect the fractions in the temperature range of 92~125℃ to obtain high-purity polytert-term amine intermediates; (3) Quaternization reaction: The high-purity polytertiary amine intermediate was mixed with 100 mL of solvent and placed in an environment of 0~5℃. The mixture was stirred and nitrogen gas was introduced to purge the air. 100 mL of solvent was mixed with 3-fluoro-1,3-propanesulfonate lactone and slowly added dropwise to the above mixture at 0~5℃. After the addition was completed, the temperature was raised and the reaction was continued for 10 h. After the reaction was completed, the solid product was collected, washed and dried to obtain unsaturated fluorinated betaine monomer.

2. The alcohol-based polymer thickener according to claim 1, characterized in that, The polyether alcohol is selected from one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, and polyethylene glycol 1000; And / or, the first surfactant is one or more of Span 60, Span 80, Tween 60, and Tween 80.

3. A method for preparing an alcohol-based polymer thickener as described in claim 1 or 2, characterized in that, The process includes the following steps: adding copolymer powder to polyether alcohol, then adding organic bentonite and a first surfactant, and stirring thoroughly for 0.5 to 1 hour to obtain the alcohol-based polymer thickener.

4. The preparation method according to claim 3, characterized in that, The method for preparing the copolymer powder includes the following steps: S1. Add acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and unsaturated fluorinated betaine monomer to deionized water at 2 to 3 times the total mass of monomers, then add 5 to 10% of low molecular weight alcohol and 0.1 to 0.3% of a second surfactant, stir thoroughly to dissolve and obtain a mixture. S2. At a temperature of 35~50℃, nitrogen gas is introduced into the mixture for 30 min, then an initiator accounting for 0.005~0.01% of the total mass of the monomer is added, the temperature is raised to 65~80℃, and the mixture is stirred for 4~6 h to obtain the crude product. S3. The crude product is purified by precipitation with anhydrous ethanol. The purified product is dried to constant weight under vacuum at 30-50°C. After granulation, crushing and sieving through a 100-200 mesh sieve, the copolymer powder is obtained.

5. The preparation method according to claim 4, characterized in that, The low molecular weight alcohol is selected from one or more of isobutanol, ethylene glycol, propylene glycol, butanediol, glycerol, butanetetraethanolamine, pentanediol, and hexanediol; the second surfactant is selected from one or more of sodium dodecyl sulfate, sodium dodecyl ether sulfate, ammonium lauryl sulfate, and sodium dodecylbenzene sulfonate; the initiator is selected from one or more of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobiscyanopentanoic acid, and azobisisopropylimidazoline.

6. The preparation method according to claim 5, characterized in that, In step (1), the solvent is selected from dichloromethane, chloroform, tetrahydrofuran, or diethyl ether; the amount of 3,3′-iminobis(N,N-dimethylpropylamine) is 0.1 mol; the amount of methacryloyl chloride is 0.12 mol; the stirring is magnetic stirring, and the temperature control range during the dropping stage is 0~5℃; the washing includes washing twice with distilled water and then washing twice with saturated brine; the drying is drying with anhydrous magnesium sulfate overnight; and the solvent removal treatment is rotary evaporation to remove the solvent.

7. The preparation method according to claim 5, characterized in that, In step (2), the polymerization inhibitor is one of phenothiazine, hydroquinone, hydroquinone monomethyl ether, or 2,6-di-tert-butyl-4-methylphenol; In step (3), the solvent is one of acetone, acetonitrile, tetrahydrofuran or methanol; the amount of the high-purity polytert-amine intermediate is 0.1 mol, and the amount of 3-fluoro-1,3-propanesulfonate lactone is 0.31 mol; the dropping time is 1-2 h; the target temperature for heating after the dropping is completed is 40 °C; the solid product is collected by vacuum filtration, the washing is washing the filter cake multiple times with acetone, and the drying is drying in a vacuum drying oven at 40-50 °C until constant weight.

8. The application of an alcohol-based polymer thickener as described in claim 1 or 2 in unconventional oil and gas reservoir fracturing.

9. The application according to claim 8, characterized in that, The unconventional oil and gas reservoir is a tight sandstone reservoir. In application, an alcohol-based polymer thickener is dissolved in deionized water at a mass fraction of 1.0 wt% to form a high-viscosity liquid for fracturing operations. During the operation, the sand ratio is controlled at 30%, and the fracturing is carried out at 100℃ for 100 seconds. -1 Under shear rate conditions, the solution viscosity is >80 mPa·s after shearing for 90 min, and the viscosity of the broken gel is <5 mPa·s and the surface tension is <28 mN / m after gel breaking.

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