Fluorosilane modified gemini surfactant and preparation method thereof, resistance reducing agent and preparation method thereof, and polymer fracturing fluid

Abstract

The invention provides a fluorosilane modified gemini surfactant and a preparation method thereof, a resistance reducing agent and a preparation method thereof, and a polymer fracturing fluid. The fluorosilane modified gemini surfactant has a structure as shown in a formula I, wherein R1 is selected from one or a combination of more than two of saturated alkyl, alkylaryl, alkylalkyloxy, alkylacyl and unsaturated alkyl with 1-8 carbons, and R2 is selected from one or a combination of more than two of alkyl, alkylaryl, alkylalkyloxy, alkylacyl and unsaturated alkyl with 1-8 carbons; (CF2) the number of n in n is 1 to 18; x <-> is Br <-> and / or I <->; and R2 is selected from one or a combination of more than two of straight-chain saturated alkyl, branched-chain saturated alkyl, alkylaryl, alkylalkoxy, alkyl ester group and unsaturated alkyl with 1-8 carbons. According to the invention, the fluorosilane modified gemini surfactant is used as a hydrophobic monomer of the resistance reducing agent, so that the synthesized resistance reducing agent has a single-head and double-tail gemini surfactant structure, the tackifying and sand-carrying capabilities are improved, and the surface and interface tension of a gel breaking solution and reservoir rocks is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas field fracturing fluid, and particularly relates to fluorosilane modified gemini surfactant, its preparation method, friction reducer, its preparation method and polymer fracturing fluid. BACKGROUND

[0002] As a hydraulic fracturing treatment method, slickwater fracturing can use a large amount of water to fracture the formation at a high pumping rate and deliver proppant into the fracture. Slickwater fracturing has gained widespread attention and popularity in unconventional reservoirs due to its simplicity, less polymer use, less damage to the formation, low cost and a series of advantages. A key ingredient used in slickwater fracturing fluid is friction reducer, which helps to reduce the friction loss when the fracturing fluid flows at high speed through the pipeline. The reduction of friction resistance can significantly reduce the power required by the pump, thereby reducing the cost. The most widely used friction reducer in slickwater fracturing fluid is high molecular weight acrylamide-based copolymer. These polymers have good shear stability and thermal stability, as well as effective friction reduction performance. Most of the commercially available friction reducer products are acrylamide polymers, but as the base fluid salinity increases, its friction reduction performance and viscosity decrease. In addition, another big problem of slickwater fracturing fluid is that due to the low viscosity of the fluid, the proppant delivery capacity is limited, which may be attributed to the low addition amount of polymer in the fluid, resulting in an average of 200,000 to 600,000 cubic meters of water required for each unconventional well to complete the injection of an appropriate amount of proppant in the fracture. Fresh water has always been used as the base fluid for slickwater fracturing, but due to the limited fresh water resources, it is becoming more and more difficult to obtain slickwater fracturing.

[0003] In order to reduce fresh water consumption, increase the use of high-salt seawater or produced water as slick water fracturing base fluid, a large amount of research work has been done on the design and synthesis of salt-resistant friction reducer for slick water fracturing, which is committed to reducing friction under the condition of high salinity, and making the fluid thick, so as to suspend and transport more proppant. CN117417754A discloses a hydrolysis-resistant polymerizable surfactant and a preparation method thereof. A new monomer with surface activity and double bond is prepared by reacting allyl fatty alcohol polyoxyethylene ether acid chloride with dodecyl primary amine. The new monomer can significantly reduce the surface tension of aqueous solution, has strong hydrolysis resistance and strong spreading ability on low-energy hydrophobic surface, and is suitable for coating and oil field chemical field. CN114195927A provides a thickening agent, a composition for forming the same, an emulsion polymer, a fracturing fluid system and application thereof, to solve the problem that the existing fracturing fluid system cannot simultaneously meet the requirements of small formation damage, less residue, shear resistance and convenient preparation process. The composition of the thickening agent comprises: acrylamide, N,N dimethyl acrylamide, sodium acrylate, cationic polymerizable surfactant, viscoelastic surfactant, organic salt, inorganic salt, initiator and water; wherein the cationic polymerizable surfactant is a polymer formed by copolymerization of a fatty tertiary amine with C atom number of 12-22 and a halogenated olefin, and the molecular weight is 303-443. However, the above polymerizable surfactant and friction reducer cannot simultaneously have low surface tension, low damage and good thickening, salt resistance and friction reduction effect.

[0004] Therefore, how to form an efficient multifunctional friction reducer to improve the fracturing effect of unconventional oil and gas reservoirs, thereby reducing reservoir damage, is still a current technical challenge. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a fluorosilane modified gemini surfactant, a preparation method thereof, a friction reducer and a preparation method thereof, and a polymer fracturing fluid. The gemini surfactant as a hydrophobic monomer can be copolymerized with acrylamide and salt-resistant monomers to form a friction reducer molecule with a single-head double-tail chain with strong hydrophobicity and low surface energy, which is used for polymer fracturing fluid.

[0006] To achieve the above purpose, the present application provides a fluorosilane modified gemini surfactant, wherein the fluorosilane modified gemini surfactant has the structure shown in formula I:

[0007]

[0008] wherein R1 is selected from one or a combination of more than two of saturated alkyl of 1-8 carbons, alkylaryl of 1-8 carbons, alkylalkoxy of 1-8 carbons, alkylacyl of 1-8 carbons, unsaturated alkyl of 1-8 carbons, etc.; (CF2) n n is 1-18; X- Br - and / or I - R2 is selected from one or a combination of two or more of a linear saturated alkyl group of 1-8 carbons, a branched saturated alkyl group of 1-8 carbons, an alkylaryl group of 1-8 carbons, an alkylalkoxy group of 1-8 carbons, an alkyl ester group of 1-8 carbons, an unsaturated alkyl group of 1-8 carbons, and the like.

[0009] According to a specific embodiment of the present application, preferably, the R1 is selected from one or a combination of two or more of a methylene group, an ethylene group, a propylene group, a butylene group, a hexylene group, a phenylene group, a benzylidene group, a phenylethylene group, a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a formyl group, an acetyl group, a propionyl group, a butyryl group, a hexanoyl group, a vinylene group, a propenylene group, a butenylene group, a hexenylene group, and the like.

[0010] According to a specific embodiment of the present application, preferably, the R2 is selected from one or a combination of two or more of a methyl group, an ethyl group, a propyl group, a butyl group, a 2-methylpropyl group, a 2-methylbutyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenyl group, a benzyl group, a phenethyl group, an acetyloxy group, a propionyloxy group, a butyryloxy group, a propenoyl group, a propenoxy group, a propenoxy methyl group, a propenoxy ethyl group, and the like.

[0011] According to a specific embodiment of the present application, preferably, the fluorosilane-modified gemini surfactant has a viscosity average molecular weight of 500-1800.

[0012] According to a specific embodiment of the present application, preferably, the fluorosilane-modified gemini surfactant has a structure of:

[0013]

[0014] The present application also provides a preparation method of the above fluorosilane-modified gemini surfactant, wherein the preparation method comprises:

[0015] (1) ring-opening reaction of γ-butyrolactone in the presence of a catalyst to generate a di-tert-ammonium monomer containing a hydroxyl group;

[0016] (2) reaction of the di-tert-ammonium monomer containing a hydroxyl group with acryloyl chloride to generate a di-tert-ammonium monomer containing an acrylate group;

[0017] (3) reaction of the di-tert-ammonium monomer containing an acrylate group with a fluorine-substituted silane to generate a corresponding quaternary ammonium salt, thereby obtaining the fluorosilane-modified gemini surfactant.

[0018] According to a specific embodiment of the present application, preferably, the volume ratio of the hydroxyl-containing ditertiary amine monomer to acryloyl chloride is (10-20):(3-6); the volume ratio of the acrylate-containing ditertiary amine monomer to fluorine-substituted silane is (4-8):(3-10).

[0019] According to a specific embodiment of the present application, preferably, the fluorine-substituted silane comprises one or a combination of two or more of trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, trimethoxy(3,3,3-trifluoropropyl)silane, trimethoxy(1H,1H,2H,2H-tridecafluoro-n-octyl)silane, trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, 3,3,3-trifluoropropyltriethoxysilane, dimethylmethoxy(3,3,3-trifluoropropyl)silane, triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane, 11-pentafluorophenoxyundecyltriethoxysilane, (E)-trimethyl(3,3,3-trifluoro-1-propenyl)silane, etc.

[0020] According to a specific embodiment of the present application, preferably, the fluorine-substituted silane is added in the form of a bromide and / or an iodide, and specifically one or a combination of two or more of the above-listed bromides and / or iodides of the fluorine-substituted silane can be used.

[0021] According to a specific embodiment of the present application, preferably, the catalyst comprises one or a combination of two or more of diisobutylaluminum hydride, tribromophosphine, cyclotriphosphazene base, sodium hydroxide, potassium hydroxide, sodium bicarbonate, triethylamine, etc.

[0022] In the above preparation method, preferably, the preparation method of the fluorosilane-modified gemini surfactant specifically comprises the following steps:

[0023] (1) 50-200 mL of 3,3-iminobis(N,N-dimethylpropylamine) and 500-1000 mL of tetrahydrofuran (THF) are added to a flask, and nitrogen is introduced into the reactor; 200-400 mL of a toluene solution of diisobutylaluminum hydride is added to a feeding funnel, and then added to the reaction liquid in a dropwise manner, and after reaction at 0-25℃ for 5-12 hours, the reaction bottle is warmed to 15-30℃, 15-40 mL of γ-butyrolactone is added to the reaction mixture, and refluxed for 6-16 hours; the reaction mixture is poured into a separation funnel, and the organic layer is separated from the water layer, and extracted with 50-150 mL of chloroform for 3-5 times, and the solvent is removed by a rotary evaporator to obtain a hydroxyl-containing ditertiary amine monohydric alcohol;

[0024] (2) In a flask, 50-100 mL of dichloromethane and 40-80 mL of di-tert-butylamine monohydric alcohol containing hydroxyl were added and cooled to 0℃, then 12-24 mL of acryloyl chloride was added to a feeding funnel containing 20-30 mL of organic solvent, and the solution was added dropwise to the reaction flask; after the reaction was completed, the solvent was evaporated, washed with saturated 20-50 mL NaHCO3 and Na2CO3 mixed aqueous solution; the aqueous solution was introduced into a separation funnel and extracted with dichloromethane 3-6 times; the solvent was evaporated and the product was purified by column chromatography; the total eluent was evaporated to obtain a yellow oil;

[0025] (3) In a flask, 20-40 mL of di-tert-butylamine monomer containing acrylate and 15-50 mL of bromo or iodo fluorosilane were added, and 50-200 mL of organic solvent was added, and refluxed at 50-90℃ for 6-12 hours; the solvent was distilled off under reduced pressure to obtain a fluorosilane modified gemini surfactant.

[0026] In some specific embodiments, preferably, in steps (2), (3), the organic solvent is one or a combination of more than two of isopropyl alcohol, 70% ethanol, diethyl ether, acetone, dichloromethane, tetrahydrofuran, cyclohexane, ethyl acetate, triethylamine, N,N dimethylformamide, etc.

[0027] In some specific embodiments, preferably, the preparation method of the halide (bromo, iodo) of the fluorosilane comprises: mixing 50-100 mL of fluorosilane with 60-120 mL of bromine water or I2 KI solution, heating and stirring under reflux at 80-120℃ for 6-12 hours, then sequentially separating by a separation funnel, washing with 20-50 mL of Na2S2O3 solution and 20-50 mL of water, separating by a separation funnel, drying with P2O5, and then distilling under reduced pressure to obtain the halide of the fluorosilane.

[0028] The application also provides a resistance reducing agent, wherein, taking the mass of water as 100%, the raw material composition of the resistance reducing agent comprises: 12%-27% of acrylamide, 0.5%-10.5% of salt-tolerant anionic monomer, 0.01%-1.5% of gemini surfactant, 0.1%-5% of cosolvent, 0.005%-0.15% of initiator, and water; the gemini surfactant is the above-mentioned fluorosilane modified gemini surfactant.

[0029] According to the specific embodiments of the application, preferably, the salt-tolerant anionic monomer comprises one or a combination of more than two of acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, sodium allylsulfonate, sodium 2-acrylamido dodecane sulfonate, sodium p-styrene sulfonate, 3-acrylamido-3-methyl butyric acid, etc.

[0030] According to a specific embodiment of the present application, preferably, the co-solvent comprises one or a combination of two or more of thiourea, urea, ethylene glycol, polyethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, isopropyl alcohol, butanol, Tween 80, β-cyclodextrin, sodium dodecyl sulfonate, etc.

[0031] According to a specific embodiment of the present application, preferably, the initiator comprises one or a combination of two or more of ammonium persulfate-sodium bisulfite system, potassium persulfate-sodium bisulfite system, benzoyl peroxide-N,N-dimethyl aniline, azobisdimethylaminoformamide hydrochloride, azobisdimethylimidazoline hydrochloride, azobisdimethylpropyl imidazoline hydrochloride, azoisobutyl cyanamide formamide, etc.

[0032] According to a specific embodiment of the present application, preferably, the preparation method of the friction reducer comprises:

[0033] Acrylamide is added to water, and then a salt-tolerant anionic monomer is added, and the pH is adjusted to 7-10, followed by the addition of the fluoroalkylsilane modified gemini surfactant and the co-solvent; then oxygen is excluded, and the temperature is kept constant, and an initiator solution is added dropwise to perform a polymerization reaction; after the reaction, the product is washed, cut, and dried to obtain the friction reducer.

[0034] According to a specific embodiment of the present application, preferably, the temperature of the polymerization reaction is 25-60℃; the time of the polymerization reaction is 3-8 hours; and the temperature of the constant temperature is the temperature at which the polymerization reaction occurs.

[0035] In the above preparation method, preferably, the preparation method of the friction reducer specifically comprises the following steps:

[0036] In a glass reaction kettle equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 12%-27% of acrylamide is added to water, and stirred at a speed of 200-800 r·min -1 for 3-10 minutes until completely dissolved; 0.5%-10.5% of a salt-tolerant anionic monomer is added, and the pH is adjusted to 7-10 using an aqueous NaOH solution, followed by the addition of 0.01%-1.5% of a cationic polymerizable fluoroalkylsilane modified gemini surfactant and 0.1%-5% of a co-solvent; after stirring at a speed of 200-800 r·min -1 for 3-10 minutes, nitrogen is introduced for 15-60 minutes to exclude oxygen, and the temperature is kept constant in the range of 25-60℃; an initiator solution is added dropwise, the amount of the initiator is 0.005%-0.15%, and the addition is completed uniformly in 1-2 hours; the reaction is stopped after heating for 3-8 hours; the product is repeatedly washed with ethanol to obtain a white gel, which is cut, washed, and dried to obtain a powder friction reducer.

[0037] The application further provides a polymer fracturing fluid, wherein the polymer fracturing fluid comprises the above resistance reducing agent and water; and the addition amount of the resistance reducing agent is 0.1%-0.6% based on 100% of the mass of the water.

[0038] According to a specific embodiment of the application, preferably, the preparation method of the polymer fracturing fluid comprises: weighing a certain amount of the powder resistance reducing agent and dissolving the powder resistance reducing agent in water under stirring to prepare the polymer fracturing fluid.

[0039] Compared with the prior art, the application has the following beneficial effects:

[0040] (1) The fluorosilane modified gemini surfactant provided by the application has the advantages of both fluorine-containing surfactants with super-high surface activity and organic silicon surfactants with excellent high and low temperature resistance and weather resistance, because the bond energy of C-F bond and C-Si (or Si-O) bond in the fluorosilane modified monomer is high. Therefore, when the fluorosilane modified gemini surfactant is used as a polymerization monomer of a resistance reducing agent, the fluorosilane modified gemini surfactant has multiple properties such as hydrophobicity, oil repellency, temperature resistance, weather resistance, chemical inertness and low surface energy. In addition, the fluorosilane modified gemini surfactant has the functions of bactericide and clay stabilizer due to the presence of a quaternary ammonium salt structure. Compared with common hydrophobic monomers, the fluorosilane-containing hydrophobic monomer has stronger hydrophobicity, so that the synthesized resistance reducing agent polymer has stronger hydrophobic binding.

[0041] (2) The resistance reducing agent provided by the application uses the polymerizable fluorosilane modified gemini surfactant as a hydrophobic monomer of the resistance reducing agent, so that the synthesized resistance reducing agent has a gemini surfactant structure with a single head and double tails, and has strong micelle-forming capacity and a lower critical micelle concentration value than corresponding conventional surfactants, so that the efficiency of reducing the surface tension of a solution is higher. In addition, the resistance reducing agent can improve the strong water wettability of a rock surface, increase the contact angle of retained water, reduce capillary resistance and reservoir damage, improve the viscosity increasing and sand carrying capacity, reduce the surface interfacial tension between a gel breaking liquid and a reservoir rock, and promote liquid flowback.

[0042] (3) The polymer fracturing fluid provided by the application has a simple formula, and the polymer has the functions of resistance reduction, viscosity increase, temperature and shear resistance, anti-swelling, cleanup assistance and sterilization, so that the functions of one agent are realized, the on-site fracturing fluid injection process is greatly simplified, and the fracturing efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a synthesis schematic diagram of the fluorosilane modified gemini surfactant.

[0044] Figure 2 It is a nuclear magnetic resonance hydrogen spectrum of the fluorosilane modified gemini surfactant 1.

[0045] Figure 3NMR spectrum of hydrogen of resistance reducer 1 in the example.

[0046] Figure 4 Viscosity test results of the polymer fracturing fluid in Example 1 at room temperature.

[0047] Figure 5 Resistance reduction rate test results of the polymer fracturing fluid in Example 1 at room temperature.

[0048] Figure 6 Surface tension test results of the polymer fracturing fluid breaker in Example 1 at room temperature.

[0049] Figure 7 Linear expansion rate test results of the polymer fracturing fluid breaker with a concentration of 0.4% in Example 1 at room temperature.

[0050] Figure 8 Rheological curve of the polymer fracturing fluid with a concentration of 0.4% in Example 1. DETAILED DESCRIPTION

[0051] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it should not be understood as limiting the scope of the present application.

[0052] Preparation Example:

[0053] As shown in Figure 1 , the preparation of the cationic polymerizable fluorosilane modified gemini surfactant 1 includes the following steps:

[0054] (1) Connect a dry 2000 mL three-necked round-bottom flask to a 250 mL addition funnel and a condenser. Add 50 mL of 3,3-imino bis(N,N-dimethylpropylamine) and 700 mL of THF to the round-bottom flask, and introduce nitrogen into the reactor. Add 225 mL of a toluene solution of diisobutylaluminum hydride to the addition funnel, and then add it to the reaction solution in a dropwise manner; after reacting at 0°C for 7 hours, warm the reaction bottle to 23°C, and add 17 mL of γ-butyrolactone to the reaction mixture and reflux for 12 hours. Then pour the reaction mixture into a separation funnel, separate the organic layer from the water layer, extract with 100 mL of chloroform for 3 times, and remove the solvent with a rotary evaporator to obtain a di-tert-butylamine monohydric alcohol containing a hydroxyl group.

[0055] (2) A dry 250 mL round bottom flask was connected to a 50 mL addition funnel, and 50 mL of dichloromethane and 40 mL of di-tert-butylamine monohydroxy alcohol were added. The flask was cooled to 0°C, then 16 mL of acryloyl chloride was added to a 30 mL addition funnel containing 30 mL of acetone, and the solution was added dropwise to the reaction flask for reaction. After the reaction was completed, the solvent was evaporated, and the aqueous solution was washed with 30 mL of a saturated NaHCO3 and Na2CO3 mixed aqueous solution for 3 times. After washing, the aqueous solution was introduced into a separation funnel and extracted with dichloromethane for 3 times; the solvent was evaporated, and the product was purified using column chromatography; the total eluent was evaporated to obtain a yellow oil, which was the di-tert-butylamine monomer containing acrylate.

[0056] (3) In a 250 mL round bottom flask, 100 mL of trimethoxy (1H, 1H, 2H, 2H-tridecafluoro-n-octyl) silane was heated and stirred at 90°C with 75 mL of bromine water for 8 hours, then separated by a separation funnel, washed with 30 mL of Na2S2O3 solution and 40 mL of water, separated by a separation funnel, dried with P2O5, and then distilled under reduced pressure to obtain bromo-trimethoxy (1H, 1H, 2H, 2H-tridecafluoro-n-octyl) silane. In a dry 500 mL round bottom flask, 20 mL of di-tert-butylamine monomer containing acrylate and 39 mL of bromo-trimethoxy (1H, 1H, 2H, 2H-tridecafluoro-n-octyl) silane were added, and 100 mL of triethylamine was added, and refluxed at 80°C for 8 hours. After the reaction product was cooled, the solvent was removed by distillation under reduced pressure to obtain a white paste product, which was the cationic polymerizable fluorosilane modified Gemini surfactant 1, having a structural formula as shown in Formula II, and its proton nuclear magnetic resonance spectrum is shown in Figure 1. Figure 2

[0057]

[0058] Example 1

[0059] The present embodiment provides a preparation method of a polymer fracturing fluid, which comprises the following steps:

[0060] (a) In a glass reaction kettle equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 20% of acrylamide was added to water, which was taken as 100% by mass of water, and stirred at a speed of 500 r·min-1for 5 minutes until completely dissolved. 4.8% of 2-acrylamido-2-methylpropane sulfonic acid was added, and the pH was adjusted to 8 with an aqueous NaOH solution, followed by the addition of 0.2% of cationic polymerizable fluorosilane modified Gemini surfactant 1 and 2% of urea, and stirred at a speed of 500 r·min-1for 5 minutes until completely dissolved. -1 -1 ​​After stirring at a constant speed for 5 minutes, nitrogen gas was introduced for 30 minutes to remove oxygen. The mixture was kept at 40°C, and 10 mL of azobisisopropylimidazoline hydrochloride (0.5% aqueous solution) was added dropwise. The amount of initiator was 0.05%, and the addition was completed uniformly over 1.5 hours. Heating was stopped after 6 hours of reaction. The product was repeatedly washed with ethanol to obtain a white gel-like substance. After being cut, washed, and dried, powdered drag reducer 1 was obtained, possessing the structural formula shown in Formula III. Its 1H NMR spectrum is shown below. Figure 3 As shown.

[0061] (b) Weigh 1-6g of powder drag reducer 1 and dissolve it in 1000mL of water under stirring to prepare different polymer fracturing fluids 1 with concentrations of 0.1-0.6%.

[0062]

[0063] The following investigation explores the effect of the dosage of powdered drag reducer (i.e., the concentration of polymer fracturing fluid) on the performance of polymer fracturing fluid. Using water as a 100% concentration, the viscosity, drag reduction rate, surface tension, linear expansion rate, and rheological properties of polymer fracturing fluid at different concentrations were tested. The results are as follows:

[0064] Figure 4 This shows the relationship between the concentration and viscosity of polymer fracturing fluid, from... Figure 4 It can be seen that with the addition of drag-reducing agent at concentrations of 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, and 0.6%, the viscosity of the polymer fracturing fluid varies between 19.5 and 84 mPa·s, indicating that adjusting the amount of drag-reducing agent can make the fracturing fluid more viscous.

[0065] Figure 5 The relationship between the concentration of polymer fracturing fluid and the drag reduction rate is shown. Figure 5 It can be seen that the drag reduction rate of the polymer fracturing fluid with a concentration of 0.1% is 72.3%, which shows a good drag reduction effect.

[0066] Figure 6 This shows the relationship between the concentration of polymer fracturing fluid and its surface tension, from... Figure 6 It can be seen that the surface tension of the polymer fracturing fluid with a concentration of 0.1%-0.6% is less than 28mN / m, and the requirement of low surface tension can be achieved without the addition of drainage aids.

[0067] Figure 7 The linear expansion rate of the polymer fracturing fluid rupture solution at a concentration of 0.4% is shown. Figure 7It can be seen that the linear expansion rate of the fracturing fluid breaker with a concentration of 0.4% to the tight sandstone is 1.90, and the linear expansion rate of water to the tight sandstone is 8.64, so the anti-swelling rate of the fracturing fluid breaker with a concentration of 0.4% is 78.01%, which has weak water sensitivity damage.

[0068] Figure 8 The rheological curve of the polymer fracturing fluid with a concentration of 0.4% is shown, and the test parameters are: shearing for 50 minutes at 120°C and 170s -1 Figure 8 It can be seen that the viscosity of the fracturing fluid with a concentration of 0.4% after shearing is still 30.36mPa·s, and the viscosity retention rate is 56.25%.

[0069] Example 2

[0070] The embodiment provides a preparation method of a polymer fracturing fluid, and the preparation method comprises the following steps:

[0071] (a) 24% of acrylamide is added to water in a glass reaction kettle provided with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet pipe, taking the mass of water as 100%, and stirring at a speed of 600r·min -1 for 10 minutes until completely dissolved. 5.8% of acrylic acid is added, and the pH is adjusted to 9 with a NaOH aqueous solution. Then, 0.5% of a cationic polymerizable fluorosilane modified gemini surfactant 1 and 4% of urea are added, and stirring is performed at a speed of 600r·min -1 for 10 minutes. Nitrogen is introduced for 45 minutes to remove oxygen, and the temperature is kept at 40°C. 10mL of an initiator ammonium persulfate: sodium bisulfite aqueous solution (concentration is 0.9%) in a ratio of 1:2 is added dropwise, the amount of the initiator is 0.09%, and the dropwise addition is uniformly completed in 2 hours. The reaction is stopped after 8 hours of heating. The product is repeatedly washed with ethanol to obtain a white gelatinous substance. After being cut, washed and dried, a powder friction reducer 2 is prepared, which has a structural formula shown in formula IV.

[0072] (b) 1-6g of the powder friction reducer 2 is weighed and dissolved in 1000mL of water under stirring to prepare different polymer fracturing fluids 2 with concentrations of 0.1-0.6%.

[0073]

[0074] Example 3

[0075] The embodiment provides a preparation method of a polymer fracturing fluid, and the preparation method comprises the following steps:

[0076] ​(a) Taking water as 100% by mass, 18% acrylamide is added to water in a glass reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet pipe, at a rate of 400 r·min. -1 Stir at a constant speed for 5 minutes until completely dissolved. Add 4.5% acrylic acid and 6% 2-acrylamido-2-methylpropanesulfonic acid sequentially, adjust the pH to 8 with NaOH aqueous solution, then add 0.8% cationic polymerizable fluorosilane-modified gemini surfactant and 1.5% urea, stirring at 600 rpm for 5 minutes. -1 After stirring at a constant speed for 5 minutes, nitrogen gas was introduced for 45 minutes to remove oxygen. The mixture was kept at a constant temperature of 50°C, and 10 ml of azobisisobutyramidine hydrochloride (1% aqueous solution) was added dropwise. The amount of initiator was 0.1%, and the addition was completed uniformly over 2 hours. Heating was stopped after 5 hours of reaction. The product was repeatedly washed with ethanol to obtain a white gel-like substance. After being cut, washed, and dried, powdered drag-reducing agent 3 was obtained, which has the structural formula shown in Formula V.

[0077] (b) Weigh 1-6g of powder drag reducer 3 and dissolve it in 1000mL of water under stirring to prepare different polymer fracturing fluids 3 with concentrations of 0.1-0.6%.

[0078]

[0079] Example 4

[0080] This embodiment provides a method for preparing a polymer fracturing fluid, which includes the following steps:

[0081] (a) Taking water as 100% by mass, 20% acrylamide is added to water in a glass reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet pipe, and the mixture is stirred at 600 r·min. -1 Stir at a constant speed for 5 minutes until completely dissolved. Add 9.5% 3-acrylamide-3-methylbutyric acid, adjust the pH to 8 with NaOH aqueous solution, then add 0.3% cationic polymerizable fluorosilane-modified gemini surfactant and 1.2% urea, stirring at 300 rpm for 5 minutes. -1 After stirring at a constant speed for 5 minutes, nitrogen gas was introduced for 30 minutes to remove oxygen. The mixture was kept at a constant temperature of 30°C, and 10 mL of an aqueous solution of benzoyl peroxide and N,N-dimethylamine (concentration 0.6%) was added dropwise. The amount of initiator was 0.06%, and the addition was completed uniformly over 2 hours. Heating was stopped after 5 hours of reaction. The product was repeatedly washed with ethanol to obtain a white gel-like substance. After being cut, washed, and dried, powdered drag reducer 4 was obtained, which has the structural formula shown in Formula VI.

[0082] (b) Weigh 1-6g of powder drag reducer 4 and dissolve it in 1000mL of water under stirring to prepare different polymer fracturing fluids 4 with concentrations of 0.1-0.6%.

[0083]

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a polymer fracturing fluid, which includes the following steps:

[0086] (a) Taking water as 100% by mass, 20% acrylamide is added to water in a glass reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet pipe, and the mixture is stirred at 500 r·min. -1 Stir at a constant speed for 5 minutes until completely dissolved. Add 4.8% 2-acrylamido-2-methylpropanesulfonic acid, adjust the pH to 8 with NaOH aqueous solution, then add 2% urea, stirring at 500 rpm. -1 After stirring at a constant speed for 5 minutes, nitrogen gas was introduced for 30 minutes to remove oxygen. The mixture was kept at a constant temperature of 40°C, and 10 mL of initiator azobisisopropylimidazoline hydrochloride (0.5% aqueous solution) was added dropwise. The amount of initiator was 0.05%, and the addition was completed uniformly over 1.5 hours. Heating was stopped after 6 hours of reaction. The product was repeatedly washed with ethanol to obtain a white gel-like substance, which was then cut, washed, and dried to obtain powdered drag-reducing agent 5.

[0087] (b) Weigh 1-6g of powder drag reducer 5 and dissolve it in 1000mL of water under stirring to prepare different polymer fracturing fluids 5 with concentrations of 0.1-0.6%.

[0088] Comparative Example 2

[0089] This comparative example provides a method for preparing a polymer fracturing fluid, which includes the following steps:

[0090] (a) Taking water as 100% by mass, 20% acrylamide is added to water in a glass reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet pipe, and the mixture is stirred at 600 r·min. -1 Stir at a constant speed for 5 minutes until completely dissolved. Add 9.5% 3-acrylamide-3-methylbutyric acid, adjust the pH to 8 with NaOH aqueous solution, then add 2% urea, and stir at 300 rpm for 5 minutes. -1After stirring for 5 minutes, oxygen was removed by passing nitrogen for 30 minutes, and the temperature was kept constant at 30°C. 10 mL of an initiator, a benzoyl peroxide solution with a concentration of 0.6% in N,N-dimethylaniline, was added dropwise, and the amount of the initiator was 0.06%. The addition was completed uniformly in 2 hours, and the reaction was stopped after 5 hours. The product was repeatedly washed with ethanol to obtain a white gel, which was cut, washed, and dried to obtain a powder of the friction reducer 6.

[0091] (b) 1-6 g of the powder of the friction reducer 6 was weighed into 1000 mL of water under stirring to prepare different polymer fracturing fluids 6 with a concentration of 0.1-0.6%.

[0092] The viscosity, temperature resistance and shear resistance, friction reduction rate, surface tension, anti-swelling rate, and core permeability damage rate of the polymer fracturing fluids prepared in Examples 1-4 and Comparative Examples 1-2 at room temperature were tested, and the results are shown in Table 1. The test methods of the above properties are as follows:

[0093] Core permeability damage rate test method: a multifunctional core displacement device was used to displace the core with formation water to obtain the initial permeability, i.e., the permeability K1 of the core before damage; the core was displaced with the fracturing fluid to obtain the core permeability at damage; the core was displaced with formation water to obtain the damaged core permeability K2. The core permeability damage rate was calculated according to formula (1):

[0094]

[0095] In the formula, η d represents the core permeability damage rate, %; K1 and K2 represent the permeabilities of the core before and after damage, mD.

[0096] Friction reduction rate test method: a pipeline friction meter was used to test the friction of clean water P0 under the conditions of a pipe diameter of 8 mm and a linear velocity of 10 m / s, and then to test the friction of the fracturing fluid P1 under the same conditions. The friction reduction rate was calculated according to formula (2):

[0097]

[0098] Anti-swelling rate test method: a linear dilatometer was used to test the swelling height of the rock sample, and the anti-swelling rate of the fracturing fluid was calculated based on the linear swelling rate of clean water.

[0099] Viscosity retention rate calculation method: a rheometer was used to test the viscosities of the polymer fracturing fluids at 170 s -1 , 120°C and 1 h of shearing, and the percentage of the viscosity after shearing to the viscosity before shearing was the viscosity retention rate.

[0100] Table 1. Test results of 0.4% polymer fracturing fluid

[0101]

[0102] The experimental results recorded in Table 1 show that, taking a 0.4% polymer fracturing fluid as an example, the polymer fracturing fluids prepared in Examples 1-4, compared with polymer fracturing fluids without the addition of cationic polymerizable fluorosilane-modified gemini surfactant 1 as a polymerizable hydrophobic monomer (Comparative Examples 1-2), exhibit lower surface tension and core damage rate, as well as higher viscosity, viscosity retention, anti-swelling rate, and drag reduction rate. The cationic polymerizable fluorosilane-modified gemini surfactant 1, as a drag-reducing agent, enhances the viscosity-increasing, temperature and shear resistance, drag reduction, and anti-swelling properties of the polymer fracturing fluid, while reducing surface tension and core damage rate.

Claims

1. A fluorosilane-modified gemini surfactant, wherein, This fluorosilane-modified gemini surfactant has the structure shown in Formula I: R1 is selected from one or more combinations of saturated alkyl groups with 1-8 carbons, alkylaryl groups with 1-8 carbons, alkylalkoxy groups with 1-8 carbons, alkylacyl groups with 1-8 carbons, and unsaturated alkyl groups with 1-8 carbons. (CF2) n The number of n in the set is 1-18; X - For Br - and / or I - ; R2 is selected from one or more combinations of straight-chain saturated alkyl groups with 1-8 carbons, branched saturated alkyl groups with 1-8 carbons, alkyl aryl groups with 1-8 carbons, alkyl alkoxy groups with 1-8 carbons, alkyl ester groups with 1-8 carbons, and unsaturated alkyl groups with 1-8 carbons.

2. The fluorosilane-modified gemini surfactant according to claim 1, wherein, R1 is selected from one or more combinations of methylene, ethylene, propylene, butylene, hexylene, phenylene, benzenemethylene, benzeneethylene, methoxy, ethoxy, propoxy, butoxy, methyleneyl, acetylene, propionyl, butyryl, hexanoyl, vinylene, propenyl, butenylene, and hexenylene.

3. The fluorosilane-modified gemini surfactant according to claim 1, wherein, R2 is selected from one or more combinations of methyl, ethyl, propyl, butyl, 2-methylpropyl, 2-methylbutyl, methoxy, ethoxy, propoxy, butoxy, phenyl, benzyl, phenethyl, acetoxy, propionyloxy, butyryloxy, acryloyl, acryloyloxy, acryloyloxymethyl, and acryloyloxyethyl.

4. The fluorosilane-modified gemini surfactant according to claim 1, wherein, The viscosity-average molecular weight of the fluorosilane-modified gemini surfactant is 500-1800.

5. The fluorosilane-modified gemini surfactant according to claim 1, wherein, The structure of the fluorosilane-modified gemini surfactant is as follows:

6. The method for preparing the fluorosilane-modified gemini surfactant according to any one of claims 1-5, wherein, The preparation method includes: (1) In the presence of a catalyst, γ-butyrolactone undergoes a ring-opening reaction to generate a hydroxyl-containing ditertiary amine monomer; (2) The hydroxyl-containing ditertiary amine monomer is reacted with acryloyl chloride to generate a ditertiary amine monomer containing acrylate groups; (3) The ditertiary amine monomer containing acrylate group is reacted with fluorinated silane to generate the corresponding quaternary ammonium salt, and fluorosilane modified gemini surfactant is obtained.

7. The preparation method according to claim 6, wherein, The volume ratio of the hydroxyl-containing ditertiary amine monomer to acryloyl chloride is (10-20):(3-6); The volume ratio of the acrylate-containing ditertiary amine monomer to the fluorinated silane is (4-8):(3-10).

8. The preparation method according to claim 6, wherein, The fluorinated silanes include one or more combinations of trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane, trimethoxy(3,3,3-trifluoropropyl)silane, trimethoxy(1H,1H,2H,2H-tridecylfluorooctyl)silane, trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane, 3,3,3-trifluoropropyltriethoxysilane, dimethylmethoxy(3,3,3-trifluoropropyl)silane, triethoxy-1H,1H,2H,2H-tridecylfluorooctylsilane, 11-pentafluorophenoxyundecyltriethoxysilane, and (E)-trimethyl(3,3,3-trifluoro-1-propenyl)silane.

9. The preparation method according to claim 6, wherein, The catalyst comprises one or more of the following: diisobutylaluminum hydride, phosphorus tribromide, cyclotriphosphazene base, sodium hydroxide, potassium hydroxide, sodium bicarbonate, and triethylamine.

10. A drag-reducing agent, wherein, Based on the mass of water (100%), the raw material composition of this drag reducer includes: 12%-27% acrylamide, 0.5%-10.5% salt-resistant anionic monomer, 0.01%-1.5% gemini surfactant, 0.1%-5% cosolvent, 0.005%-0.15% initiator, and water; The gemini surfactant is the fluorosilane-modified gemini surfactant according to any one of claims 1-5.

11. The drag-reducing agent according to claim 10, wherein, The salt-resistant anionic monomer includes one or more of the following: acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, sodium allyl sulfonate, sodium 2-acrylamido-dodecanesulfonate, sodium p-styrene sulfonate, and 3-acrylamido-3-methylbutyric acid.

12. The drag-reducing agent according to claim 10, wherein, The co-solvent includes one or more of the following: thiourea, urea, ethylene glycol, polyethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, isopropanol, butanol, Tween 80, β-cyclodextrin, and sodium dodecyl sulfonate.

13. The drag-reducing agent according to claim 10, wherein, The initiator includes one or more of the following: ammonium persulfate-sodium bisulfite system, potassium persulfate-sodium bisulfite system, benzoyl peroxide-N,N-dimethylamine, azobisisobutyramidine hydrochloride, azobisisobutyramidazole hydrochloride, azobisisopropylimidazoline hydrochloride, and azobisisobutyramidamide.

14. The method for preparing the drag-reducing agent according to any one of claims 10-13, wherein, The preparation method includes: Acrylamide was added to water, followed by the addition of a salt-resistant anionic monomer, and the pH was adjusted to 7-10. Then, the fluorosilane-modified gemini surfactant and cosolvent were added. After removing oxygen and maintaining a constant temperature, an initiator solution was added dropwise to carry out the polymerization reaction. The product after the reaction was washed, shredded, and dried to obtain the drag-reducing agent.

15. The preparation method according to claim 14, wherein, The polymerization reaction is carried out at a temperature of 25-60°C for 3-8 hours.

16. A polymer fracturing fluid, wherein, The polymer fracturing fluid comprises the drag-reducing agent as described in any one of claims 10-13, and water; the drag-reducing agent is added at a rate of 0.1%-0.6% based on 100% of the mass of water.

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