Multifunctional variable viscosity slickwater fracturing fluid additive, its preparation method and application

Abstract

The application discloses a multifunctional variable-viscosity slick water fracturing fluid additive, a preparation method and application, relates to the slick water fracturing technical field, and solves the technical problem that the multifunctionalization of the fracturing fluid additive is difficult to be realized through simple compounding, wherein the nano anti-swelling agent particles are added into white oil containing a hydrocarbon-fluorocarbon surfactant mixed emulsified system to obtain an oil phase, the water phase is composed of a water-soluble vinyl monomer aqueous solution and an initiator, the fracturing fluid additive is prepared through high-speed shearing emulsification, nitrogen deoxygenation, reverse-phase emulsion polymerization reaction of oxidation and reduction initiation, and demulsification process of reverse-phase surfactant. The application has the anti-swelling performance, and the anti-swelling performance is synergistically provided with the ammonium ion in the water phase; the use amount of the ordinary hydrocarbon surfactant is reduced, the surface interfacial activity is good under the reasonable addition amount, and the gel breaking fluid has a relatively low surface interfacial tension.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield exploitation, more particularly to the technical field of slick water fracturing. BACKGROUND

[0002] With the boom of unconventional oil and gas resource exploitation, volume fracturing has become an effective measure for the reconstruction of tight oil, and the slick water fracturing technology is conducive to the communication of micro-fractures. The technology generally has a high construction discharge capacity, and the friction reducer in the slick water fracturing fluid must have good friction reduction performance in the construction operation, so as to better reduce the construction pressure, meet the requirements of large discharge capacity construction, and reduce the construction difficulty.

[0003] The traditional friction reducer prepared slick water cannot suspend and transport proppants for a long time because the final fluid viscosity is too low, only small mesh sand in the early stage is pumped by the slick water, and in order to improve the permeability, linear or crosslinked gel is used to transport large particle size proppants into the main fracture in the later stage. Many current hydraulic fracturing operations adopt a mixed method by combining the low viscosity slick water stage with the high viscosity linear gel or crosslinked gel stage, so that separate hydration and mixing equipment is usually required to prepare the fluid in advance, which is labor-intensive.

[0004] In order to adapt to the increasingly large factory fracturing operation, it is necessary to integrate and simplify the existing fracturing fluid additives, and to optimize the preparation of the friction reducer, the thickening agent, the cleanup additive, the clay stabilizer, etc. into a multi-functional fracturing fluid additive by technical means, which is an important development trend of the current fracturing fluid development.

[0005] Since the clay stabilizer is mainly a cationic quaternary ammonium salt and a polymerized cation, and the cleanup additive is a compound of various surfactants mainly including fluorocarbon surfactants, both of which exist in the form of aqueous solution. However, the fracturing fluid friction reducer, guar gum, etc. exist in the form of solid or suspended emulsion, reverse emulsion, which will rapidly absorb water and swell when encountering a small amount of water, resulting in unstable system or even gel, and it is difficult to realize the multi-functionality of the fracturing fluid additive by simple compounding. SUMMARY

[0006] The present application aims to solve the technical problem that the friction reducer, guar gum, etc. in the existing fracturing fluid additive will rapidly absorb water and swell when encountering a small amount of water, resulting in unstable system or even gel, and it is difficult to realize the multi-functionality of the fracturing fluid additive by simple compounding, and provides a multi-functional viscosity-changing slick water fracturing fluid additive, a preparation method and application.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution: a method for preparing a multifunctional variable viscosity slippery water fracturing fluid additive, wherein nano-sized anti-swelling agent particles are added to white oil containing a hydrocarbon-fluorocarbon surfactant mixed emulsion system to obtain an oil phase, and an aqueous phase composed of a water-soluble vinyl monomer aqueous solution and an initiator is prepared by high-speed shear emulsification, nitrogen deoxygenation, redox-induced reverse emulsion polymerization reaction, and demulsification process of reverse surfactant to obtain the fracturing fluid additive.

[0008] In the technical solution of this application, in order to realize the multifunctionality of fracturing fluid additives and achieve the functions of drag reduction, proppant carrying, anti-swelling, and efficient flowback of fracturing fluid, and to overcome the difficulties of the prior art, superhydrophobic nano anti-swelling agent particles with oil dispersion but water non-dispersibility are introduced around the reverse emulsion polymerization process. The nano anti-swelling agent particles cannot dissolve in water in aqueous solution, so they have good compatibility with polymer molecular chains. During the gel breaking process, the nano anti-swelling agent particles also degrade to release cationic centers, which have anti-swelling properties and synergistically enhance with ammonium ions in the aqueous phase to provide good anti-swelling performance.

[0009] Compared with existing reverse emulsion polymerization processes, the introduction of nonionic fluorocarbon surfactants as reaction emulsifiers and demulsifiers reduces the amount of ordinary hydrocarbon surfactants required. With appropriate dosage, fluorocarbon surfactants exhibit good interfacial activity, resulting in a lower interfacial tension in the demulsified liquid.

[0010] Furthermore, the preparation method specifically includes the following steps:

[0011] Step 1: Mix hydrocarbon-fluorocarbon surfactant and white oil evenly to obtain an oil phase, and add nano anti-swelling agent particles to the oil phase;

[0012] Step 2: Prepare a solution of the water-soluble monomer, adjust the pH to 6.5-7.5 with ammonia solution, add 1% wt ammonium persulfate solution and 0.5% wt azobisisobutyrazoline hydrochloride VA-044 solution to obtain the aqueous phase;

[0013] Step 3: Add the aqueous phase to the oil phase containing nano anti-swelling agent particles from Step 1, and emulsify by high-speed shearing to obtain a reverse emulsion;

[0014] Step 4: Purge with nitrogen to remove oxygen, add 0.5% wt sodium bisulfite solution dropwise. When the temperature rises to 35℃, stop adding sodium bisulfite solution and start cooling with an ice-water bath to control the reaction temperature at 40-45℃. After stopping the water bath temperature control and maintaining the temperature for the reaction, the temperature will start to drop. Add 0.5% wt sodium bisulfite solution in the later stage and continue until the temperature stops dropping. The reaction is then complete. The reaction time is 2-5 hours.

[0015] Step 5: Add the antiphase surfactant and stir to obtain the fracturing fluid additive.

[0016] Furthermore, the preparation method of the nano anti-swelling agent particles is as follows: by weight, 200g of allyl dimethyl hydroxyethyl ammonium chloride, 45g of octadecyl acrylate, and 5g of pentaerythritol allyl ether are dissolved in 500g of ethyl acetate. After purging with nitrogen to remove oxygen for 1 hour, the temperature is raised to 40-50℃, and 0.6g of azobisisobutyl cyanide is added to initiate precipitation polymerization. Then, the mixture is filtered and dried to obtain the final product.

[0017] Furthermore, in the fracturing fluid additive, the mass of the nano-anti-swelling agent particles accounts for 4.0-10.0 wt% of the total mass of the fracturing fluid additive, the mass of the water-soluble vinyl monomer accounts for 20-40 wt% of the total mass of the fracturing fluid additive, the mass of the white oil accounts for 15-25 wt% of the total mass of the fracturing fluid additive, the mass of the hydrocarbon-fluorocarbon surfactant accounts for 2.0-3.0 wt% of the total mass of the fracturing fluid additive, the mass of the ammonium persulfate accounts for 0.0001-0.002 wt% of the total mass of the fracturing fluid additive, the mass of the azobisisobutyrazoline hydrochloride accounts for 0.0001-0.005 wt% of the total mass of the fracturing fluid additive, the mass of the reverse surfactant accounts for 0.5-3 wt% of the total mass of the fracturing fluid additive, the mass of the sodium bisulfite accounts for 0.005-0.025 wt% of the total mass of the fracturing fluid additive, and the balance is water.

[0018] Furthermore, the water-soluble vinyl monomer is a mixture of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid, wherein the molar ratio of acrylamide, acrylic acid, and 2-acrylamide-2-methylpropanesulfonic acid is 50-80:20-40:0-20.

[0019] Furthermore, hydrocarbon-fluorocarbon surfactants include Span 20, Span 80, Span 85, Tween 20, Tween 80, Tween 81 and perfluorobutyric acid diethanolamide, and one or more of Span 20, Span 80, Span 85, Tween 20, Tween 80, Tween 81 and perfluorobutyric acid diethanolamide.

[0020] Furthermore, the reverse surfactant includes one or more of fatty alcohol polyvinyl ether AEO7, fluorocarbon surfactant FM21, and fluorocarbon surfactant FM10.

[0021] Furthermore, the fracturing fluid additive is prepared into a 0.05-0.10 wt% aqueous solution to obtain drag-reducing water with a drag reduction rate greater than 70%.

[0022] Furthermore, the fracturing fluid additive is prepared into a 1.0% wt aqueous solution to obtain a proppant-carrying fluid, which is then subjected to a reaction at 100°C for 170 seconds. -1 After shearing for 2 hours, the apparent viscosity is greater than 60 mPa·s.

[0023] Furthermore, the fracturing fluid additive is prepared into a 1.0% wt water solution to obtain a sand-carrying fluid. When the fluid is broken up with 0.05% ammonium persulfate at 60°C, the viscosity of the broken fluid is less than 5 mPa·s within 1 hour, the anti-swelling rate can reach 80%, the surface tension is less than 25 mN / m, and the interfacial tension is less than 2 mN / m.

[0024] In the technical solution of this application, the manufacturer of perfluorobutyric acid diethanolamide is Sichuan Ainengjie Technology Co., Ltd., and the manufacturers of fluorocarbon surfactants FM21 and FM10 are Hangzhou Renshan Technology Co., Ltd.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. This application relates to the reverse emulsion polymerization process and introduces superhydrophobic nano anti-swelling agent particles that are oil-dispersible but water-insoluble. The nano anti-swelling agent particles cannot dissolve in water in aqueous solution, so they have good compatibility with polymer molecular chains. During the depolymerization process, the nano anti-swelling agent particles also degrade to release cationic centers, thus having anti-swelling properties. They also synergistically enhance with ammonium ions in the aqueous phase to provide good anti-swelling properties.

[0027] 2. Compared with the existing reverse emulsion polymerization process, nonionic fluorocarbon surfactants are introduced as reaction emulsifiers and demulsifiers. Fluorocarbon surfactants play an emulsifying and demulsifying role in the polymerization process, reducing the amount of ordinary hydrocarbon surfactants. With reasonable addition, they have good interfacial activity, resulting in a lower interfacial tension in the demulsified liquid.

[0028] 3. The multifunctional variable viscosity slippery water fracturing fluid additive prepared in this application is formulated into a 0.05-0.10% wt clear aqueous solution to obtain drag-reducing water with a drag reduction rate of more than 70%.

[0029] 4. The multifunctional variable viscosity slickwater fracturing fluid additive prepared in this application is formulated into a 1.0% wt clear aqueous solution to obtain a proppant-carrying fluid. After shearing at 100℃ and 170 s⁻¹ for 2 hours, the apparent viscosity is greater than 60 mPa·s.

[0030] 5. The multifunctional variable viscosity slickwater fracturing fluid additive prepared in this application is formulated into a 1.0% wt clear aqueous solution to obtain a proppant-carrying fluid. When broken up with 0.05% ammonium persulfate at 60℃, the viscosity of the broken fluid is less than 5 mPa·s within 1 hour, its anti-swelling rate can reach 80%, its surface tension is less than 25 mN / m, and its interfacial tension is less than 2.

[0031] mN / m. Attached Figure Description

[0032] Figure 1This is a schematic diagram illustrating the particle dispersion performance of the anti-swelling agent of the present invention;

[0033] Figure 2 This is the present invention. Figure 1 Particle size distribution of A;

[0034] Figure 3 This is the reaction temperature rise curve of Example 2 of the present invention;

[0035] Figure 4 The rheological data of the fracturing fluid additive solution prepared in Example 4 with 1.0% tap water at 100°C were tested.

[0036] Figure 5 The rheological data of the fracturing fluid additive solution prepared in Example 4 with 0.5% tap water at 80°C were tested.

[0037] Figure 6 The results are the drag reduction rate test results of the product configured as a solution in Example 2;

[0038] Figure 7 This is a schematic diagram of the structure of nano-anti-swelling agent particles.

[0039] Specific implementation party

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0041] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0042] Example 1

[0043] Weigh 200g of allyl dimethyl hydroxyethyl ammonium chloride, 45g of octadecyl acrylate, and 5g of pentaerythritol allyl ether and dissolve them in 500g of ethyl acetate. After purging with nitrogen to remove oxygen for 1 hour, raise the temperature to 40-50℃ to initiate precipitation polymerization. Add 0.6g of initiator azobisisobutyl cyanide in three portions at 1.5-hour intervals. After the initiator is added, continue the reaction at the temperature for 2 hours. Cool to room temperature, then filter and dry to obtain anti-swelling agent granular powder.

[0044] Weigh 0.25g of the anti-swelling agent granules and disperse them in 50g of No. 3 white oil. Sonicate the dispersion for 5 minutes to obtain a uniform dispersion. Figure 1 As shown in Figure A, the particle size was measured using a nanolaser particle size analyzer. Figure 2As shown, the average particle size D50 is 572.4 nm, indicating that the anti-swelling agent particles of this application are at the nanoscale. 0.25 g of anti-swelling agent powder was weighed and slowly added to 50 g of deionized water. The mixture was magnetically stirred at 50°C for 4 hours. The anti-swelling agent particles did not disperse or dissolve. Figure 1 As shown in Figure B, the particle size could not be measured. This indicates that the anti-swelling agent particles of this application are oil-dispersible but water-insoluble cationic superhydrophobic particles.

[0045] Anti-swelling agent particle structure such as Figure 7 As shown, It represents octadecyl acrylate. Represents positive charge. It represents pentaerythritol allyl ether.

[0046] Figure 2 The corresponding table is as follows:

[0047]

[0048] Example 2

[0049] (1) Preparation of initiator solution:

[0050] Prepare 0.5% wt VA-044 (azobisisobutyrazoline hydrochloride) solution, 1% wt ammonium persulfate aqueous solution and 0.5% wt sodium bisulfite aqueous solution using deionized water respectively;

[0051] (2) Oil phase preparation:

[0052] Add 220g of industrial white oil, 20g of Span 80, 3g of Tween 81, 2g of perfluorobutyric acid diethanolamide, and 55g of nano anti-swelling agent particles to a 1000mL open reactor, and stir magnetically until homogeneous to obtain the oil phase.

[0053] (3) Aqueous phase preparation

[0054] In a 1000mL beaker, weigh 180g acrylamide, 85g acrylic acid, 30g 2-acrylamide-2-methylpropanesulfonic acid and 260g deionized water, stir magnetically until homogeneous, and the molar ratio of the three water-soluble vinyl monomers is 65.67:30.57:3.75.

[0055] Weigh 125g of ammonia solution and slowly add it dropwise to the monomer aqueous solution for neutralization, controlling the neutralization temperature below 25℃. After neutralization, the pH is 6.55.

[0056] Add 6 mL of 0.5% wt VA-044 and 1 mL of 1% wt ammonium persulfate aqueous solution;

[0057] (4) High-speed shear emulsification

[0058] The aqueous and oil phases were added to a beaker and homogenized at 12000 r / min for 5 min to obtain a viscous emulsion. The apparent viscosity was measured to be 750 mPa·s using a six-speed viscometer (100 rpm).

[0059] (5) Nitrogen gas deoxygenation and polymerization reaction

[0060] Nitrogen gas was purged for 1 hour to remove oxygen. The temperature was controlled at 17–20°C using an ice-water bath. 0.5% wt sodium bisulfite solution was added dropwise at a rate of 1.0 mL / h using a metering pump. The initial reaction temperature was 17.6°C. When the temperature rose to 35°C, the addition of sodium bisulfite solution was stopped. The reaction temperature was then controlled at 40–45°C using an ice-water bath. When the temperature began to drop, the ice-water bath was removed. After maintaining the temperature for a period of time, when the temperature began to drop again, sodium bisulfite solution was added at a rate of 5.0 mL / h. This was continued until the temperature stopped dropping, at which point the reaction was complete. The reaction time was 2.5 hours, as shown in Figure 3.

[0061] (6) Debridement

[0062] Add 20g of fatty alcohol polyvinyl ether AEO7 and 1g of fluorocarbon surfactant FM21, and continue stirring for 30 minutes to obtain fracturing fluid additive.

[0063] Example 3

[0064] (1) Preparation of oil phase:

[0065] Add 260g of industrial white oil, 10g of Span 20, 12g of Span 80, 4g of Tween 81, 1.5g of perfluorobutyric acid diethanolamide, and 80g of anti-swelling granules to a 1000mL open reactor, and stir magnetically until homogeneous to obtain the oil phase.

[0066] (2) Aqueous phase preparation

[0067] In a 1000mL beaker, weigh 180g acrylamide, 85g acrylic acid, 30g 2-acrylamide-2-methylpropanesulfonic acid and 220g deionized water, stir magnetically until homogeneous, and the molar ratio of the three water-soluble vinyl monomers is 68.40:22.48:9.12.

[0068] Weigh 110.6g of ammonia solution and slowly add it dropwise to the monomer aqueous solution for neutralization, controlling the neutralization temperature below 25℃. After neutralization, the pH is 6.75.

[0069] Add 8 mL of 0.5% wt VA-044 and 1.5 mL of 1% wt ammonium persulfate aqueous solution;

[0070] (3) High-speed shear emulsification

[0071] The aqueous and oil phases were added to a beaker and homogenized at 12000 r / min for 5 min to obtain a viscous emulsion. The apparent viscosity was measured to be 840 mPa·s using a six-speed viscometer (100 rpm).

[0072] (4) Nitrogen purging for oxygen removal and polymerization reaction

[0073] Nitrogen gas was purged for 1 hour to remove oxygen. The temperature was controlled at 17–20°C using an ice-water bath. 0.5% wt sodium bisulfite solution was added dropwise at a rate of 1.0 mL / h using a metering pump. The initial reaction temperature was 17.4°C. When the temperature rose to 35°C, the addition of sodium bisulfite solution was stopped. The reaction temperature was then controlled at 40–45°C using an ice-water bath. When the temperature began to drop, the ice-water bath was removed. The reaction was maintained at this temperature for a period of time. When the temperature began to drop again, sodium bisulfite solution was added at a rate of 3 mL / h. This process was continued until the temperature stopped dropping. The reaction was then complete. The reaction time was 3.5 hours.

[0074] (6) Debridement

[0075] Add 20g of fatty alcohol polyvinyl ether AEO7 and 1.2g of fluorocarbon surfactant FM10, and continue stirring for 30 minutes to obtain fracturing fluid additive.

[0076] Example 4

[0077] (1) Preparation of oil phase:

[0078] Add 240g of industrial white oil, 15g of Span 80, 5g of Span 20, 2g of Span 85, 4g of Tween 80, 1.4g of perfluorobutyric acid diethanolamide, and 75g of anti-swelling agent granules to a 1000mL open reactor, and stir magnetically until homogeneous to obtain the oil phase.

[0079] (2) Aqueous phase preparation

[0080] In a 1000mL beaker, weigh 165g acrylamide, 100g acrylic acid, 50g 2-acrylamide-2-methylpropanesulfonic acid and 220g deionized water, stir magnetically until homogeneous, and the molar ratio of the three water-soluble vinyl monomers is 58.77:35.12:6.11.

[0081] Weigh 154.0g of ammonia solution and slowly add it dropwise to the monomer aqueous solution for neutralization, controlling the neutralization temperature below 25℃. After neutralization, the pH is 6.55.

[0082] Add 4 mL of 0.5% wt VA-044 and 1.5 mL of 1% wt ammonium persulfate aqueous solution;

[0083] (3) High-speed shear emulsification

[0084] The aqueous and oil phases were added to a beaker and homogenized at 12000 r / min for 5 min to obtain a viscous emulsion. The apparent viscosity was measured to be 900 mPa·s using a six-speed viscometer (100 rpm).

[0085] (4) Nitrogen purging for oxygen removal and polymerization reaction

[0086] Nitrogen gas was purged for 1 hour to remove oxygen. The temperature was controlled at 17–20°C using an ice-water bath. 0.5% wt sodium bisulfite solution was added dropwise at a rate of 1.0 mL / h using a metering pump. The initial reaction temperature was 17.8°C. When the temperature rose to 35°C, the addition of sodium bisulfite solution was stopped. The reaction temperature was then controlled at 40–45°C using an ice-water bath. When the temperature began to drop, the ice-water bath was removed. The reaction was kept at this temperature for a period of time. When the temperature began to drop again, sodium bisulfite solution was added at a rate of 5 mL / h. This was continued until the temperature stopped dropping. The reaction was then complete. The reaction time was 3.5 hours.

[0087] (6) Debridement

[0088] Add 20g of fatty alcohol polyvinyl ether AEO7, 0.4g of fluorocarbon surfactant FM10 and 0.8g of fluorocarbon surfactant FM21, and continue stirring for 30 minutes to obtain fracturing fluid additive.

[0089] Example 5

[0090] (1) Preparation of oil phase:

[0091] Add 240g of industrial white oil, 15g of Span 80, 5g of Span 20, 2g of Span 85, 2g of Tween 80, 2g of Tween 81, 1.2g of perfluorobutyric acid diethanolamide, and 100g of anti-swelling agent granules to a 1000mL open reactor and stir magnetically until homogeneous to obtain the oil phase.

[0092] (2) Aqueous phase preparation

[0093] In a 1000mL beaker, weigh 130g acrylamide, 50g acrylic acid, 120g 2-acrylamide-2-methylpropanesulfonic acid and 220g deionized water, stir magnetically until homogeneous, and the molar ratio of the three water-soluble vinyl monomers is 58.96:22.36:18.67.

[0094] Weigh 120.0g of ammonia solution and slowly add it dropwise to the monomer aqueous solution for neutralization, controlling the neutralization temperature below 25℃. After neutralization, the pH is 6.55.

[0095] Add 7.5 mL of 0.5% wt VA-044 and 2 mL of 1% wt ammonium persulfate aqueous solution;

[0096] (3) High-speed shear emulsification

[0097] The aqueous and oil phases were added to a beaker and homogenized at 12000 r / min for 5 min to obtain a viscous emulsion. The apparent viscosity was measured to be 1080 mPa·s using a six-speed viscometer (100 rpm).

[0098] (4) Nitrogen purging for oxygen removal and polymerization reaction

[0099] Nitrogen gas was purged for 1 hour to remove oxygen. The temperature was controlled at 17–20°C using an ice-water bath. 0.5% wt sodium bisulfite solution was added dropwise at a rate of 1.0 mL / h using a metering pump. The initial reaction temperature was 17.8°C. When the temperature rose to 35°C, the addition of sodium bisulfite solution was stopped. The reaction temperature was then controlled at 40–45°C using an ice-water bath. When the temperature began to drop, the ice-water bath was removed. The reaction was maintained at this temperature for a period of time. When the temperature began to drop again, sodium bisulfite solution was added at a rate of 5 mL / h. This process was continued until the temperature stopped dropping. The reaction was then complete. The reaction time was 4.0 h.

[0100] (6) Debridement

[0101] Add 21g of fatty alcohol polyvinyl ether AEO7, 0.5g of fluorocarbon surfactant FM21 and 0.5g of fluorocarbon surfactant FM10, and continue stirring for 30 minutes to obtain fracturing fluid additive.

[0102] Comparative Example

[0103] (1) Oil phase preparation

[0104] Add 220g of industrial white oil, 20g of Span 80, and 3g of Tween 81 to a 1000mL open reactor, and stir magnetically until homogeneous to obtain the oil phase.

[0105] (3) Aqueous phase preparation

[0106] In a 1000mL beaker, weigh 180g acrylamide, 85g acrylic acid, 30g 2-acrylamide-2-methylpropanesulfonic acid and 260g deionized water, stir magnetically until homogeneous, and the molar ratio of the three water-soluble vinyl monomers is 65.67:30.57:3.75.

[0107] Weigh 125g of ammonia solution and slowly add it dropwise to the monomer aqueous solution for neutralization, controlling the neutralization temperature below 25℃. After neutralization, the pH is 6.55.

[0108] Add 6 mL of 0.5% wt VA-044 and 2 mL of 1% wt ammonium persulfate aqueous solution;

[0109] (4) High-speed shear emulsification

[0110] The aqueous and oil phases were added to a beaker and homogenized at 12000 r / min for 5 min using a homogenizer to obtain a viscous emulsion. The apparent viscosity was measured to be 720 mPa·s using a six-speed viscometer (100 rpm).

[0111] (5) Nitrogen gas deoxygenation and polymerization reaction

[0112] Nitrogen gas was purged for 1 hour to remove oxygen. The temperature was controlled at 17-20°C using an ice-water bath. 0.5% wt sodium bisulfite solution was added dropwise at a rate of 1.0 mL / h using a metering pump. The initial reaction temperature was 17.4°C. When the temperature rose to 35°C, the addition of sodium bisulfite solution was stopped. The reaction temperature was then controlled at 40-45°C using an ice-water bath. Sodium bisulfite solution was added later until the temperature stopped decreasing. The reaction was then complete. The reaction time was 3.5 hours.

[0113] (6) Debridement

[0114] Add 23g of fatty alcohol polyvinyl ether AEO7 and continue stirring for 30 minutes to obtain fracturing fluid additive.

[0115] Application Example 1

[0116] The multifunctional variable viscosity slickwater fracturing fluid additives prepared in Examples 2-5 were used to prepare solutions of 0.1% wt, 0.5% wt, and 1.0% wt in tap water (total salinity 235 mg / L), respectively. Their apparent viscosities were tested using a six-speed viscometer, and the results are shown in Table 1 below.

[0117] Table 1 Apparent viscosity of fracturing fluid additives at different concentrations

[0118]

[0119] As shown in the table above, the viscosity of the prepared multifunctional slickwater fracturing fluid additive increases with increasing concentration. Therefore, the viscosity-changing function can be achieved by adjusting the concentration in real time.

[0120] The rheological data of a 1.0% fracturing fluid additive solution prepared in Example 4 using tap water at 100°C were tested, as detailed below. Figure 4 .Depend on Figure 4 It can be seen that the fracturing fluid prepared with 1% additive maintains a viscosity of 60 mPa·s after being subjected to constant temperature shearing at 100℃ for 2 hours, which shows good temperature and shear resistance and can meet the requirements of fracturing operations in oil and gas wells with well temperatures below 100℃.

[0121] The rheological data of a 0.5% fracturing fluid additive solution prepared in Example 4 using tap water at 80°C were tested. See below for details. Figure 5 .Depend on Figure 5It can be seen that the fracturing fluid prepared with 0.5% additives maintains a viscosity of 50 mPa·s after being subjected to constant temperature shearing at 80℃ for 2 hours, which shows good temperature and shear resistance and can meet the requirements of fracturing operations in oil and gas wells with well temperatures below 80℃.

[0122] Application Example 2

[0123] In accordance with the requirements of section 7.7.1.1 of the standard "SY / T 5107-2016 Performance Evaluation Formula for Water-based Fracturing Fluids", a standard brine solution was prepared. The composition of the standard brine solution was: 2.0% KCl + 5.5% NaCl + 0.45% MgCl2 + 0.55% CaCl2.

[0124] The multifunctional variable viscosity slickwater fracturing fluid additives prepared in Examples 2-5 were used to prepare 1.0% wt and 1.5% wt solutions respectively with 10% standard mineralized water (8500 mg / L). Their apparent viscosity was tested using a six-speed viscometer, and the results are shown in Table 2 below:

[0125] Table 2 Apparent viscosity of fracturing fluid additives at different concentrations

[0126]

[0127]

[0128] Application Example 3

[0129] The multifunctional variable viscosity slickwater fracturing fluid additives prepared in Examples 2-5 were each prepared into 1.0% wt solutions with tap water (total mineralization 235 mg / L), and 0.04% ammonium persulfate was added. The solutions were stirred evenly and placed in an 80°C water bath for gel breaking for 4 hours. After complete gel breaking, the surface tension and interfacial tension with kerosene were tested.

[0130] Table 3 Interfacial Tension of Fracturing Fluid Breaker

[0131]

[0132] The fracturing fluid prepared with the fracturing fluid additive provided by the present invention, compared with the comparative example, has a significant effect of reducing the interfacial tension after the introduction of fluorocarbon surfactant. The surface tension of the rupture fluid is less than 25 mN / m and the interfacial tension is less than 2 mN / m.

[0133] Application Example 4

[0134] (1) Preparation of the breaking solution

[0135] The multifunctional variable viscosity slick water fracturing fluid additives prepared in Examples 2-5 were each prepared into 1.0% wt solutions with tap water (total mineralization 235 mg / L), and 0.04% ammonium persulfate was added. The solutions were stirred evenly and placed in an 80°C water bath for gel breaking for 4 hours. After complete gel breaking, the anti-swelling rate of the clay was tested.

[0136] (2) Anti-swelling rate test

[0137] ① Weigh 0.5000g of sodium bentonite 200 mesh, add it to a 10mL centrifuge tube, add 10mL of gel breaking solution, stir, disperse evenly, and let stand for 2 hours;

[0138] ② Centrifuge the above centrifuge tubes at 1500 r / min for 15 minutes and read the volume V1 of the bentonite;

[0139] ③ Calculate the anti-expansion rate:

[0140]

[0141] V1 - Volume of clay after swelling in the colloid breaker

[0142] 0.6 - Kerosene expansion volume

[0143] Table 4. Fracturing fluid gel breaking agent surface tension agent anti-swelling rate

[0144] Example 2 Example 3 Example 4 Example 5 Comparative Example 1 0.5% KCl V1 / mL 3.4 3.1 3 2.4 7 3.6 Anti-bloat rate / % 70.21 73.40 74.47 80.85 31.91 68.09

[0145] When the anti-swelling agent particles are subjected to free radical degradation under the action of high-temperature ammonium persulfate, they form polypropyl dimethyl hydroxyethyl ammonium chloride molecular chain segments, which can be effectively adsorbed on the clay surface and embedded in the crystal lattice, thus exhibiting the anti-swelling effect of clay.

[0146] The fracturing fluid prepared with the fracturing fluid additive provided by the present invention has a significantly improved anti-swelling rate compared with the comparative example, with the addition of anti-swelling agent particles. Its anti-swelling rate is better than that of 0.5% KCl solution, and the highest anti-swelling rate is above 80%.

[0147] Application Example 5

[0148] The product from Example 2 was prepared into a 0.05–0.15% solution. The drag reduction rate was tested using a pipeline friction analyzer at Jiangsu Hai'an Petrochemical Plant. The test results are as follows: Figure 6 As shown.

Claims

1. A method for preparing a multifunctional variable viscosity slippery water fracturing fluid additive, characterized in that, The preparation method specifically includes the following steps: Step 1: Mix hydrocarbon-fluorocarbon surfactant and white oil evenly to obtain an oil phase, and add nano-anti-swelling agent particles to the oil phase; the preparation method of the nano-anti-swelling agent particles is as follows: by weight, dissolve 200g allyl dimethyl hydroxyethyl ammonium chloride, 45g octadecyl acrylate, and 5g pentaerythritol allyl ether in 500g ethyl acetate, purge with nitrogen for 1 hour to remove oxygen, heat to 40-50℃, add 0.6g azobisisobutyl nitrile to initiate precipitation polymerization, and then filter and dry to obtain the product; the hydrocarbon-fluorocarbon surfactant includes one or more of Span 20, Span 80, Span 85, Tween 20, Tween 80, and Tween 81 in combination with perfluorobutyric acid diethanolamide; Step 2: Prepare a solution of water-soluble vinyl monomers, adjust the pH to 6.5-7.5 with ammonia solution, add 1 wt% ammonium persulfate solution and 0.5 wt% azobisisobutyrazoline hydrochloride VA-044 solution to obtain an aqueous phase; the water-soluble vinyl monomers are a mixture of acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, with a molar ratio of acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid of 58.77-68.40:22.36-35.12:3.75-18.67; Step 3: Add the aqueous phase to the oil phase containing nano anti-swelling agent particles from Step 1, and emulsify by high-speed shearing to obtain a reverse emulsion; Step 4: Purge with nitrogen to remove oxygen, add 0.5wt% sodium bisulfite aqueous solution dropwise. When the temperature rises to 35℃, stop adding sodium bisulfite solution and start cooling with an ice-water bath to control the reaction temperature at 40-45℃. When the water bath temperature control is stopped, keep the reaction at this temperature. After the temperature starts to drop, add 0.5wt% sodium bisulfite solution in the later stage and continue until the temperature stops dropping. The reaction is then complete. The reaction time is 2-5 hours. Step 5: Add a reverse surfactant and stir to obtain a fracturing fluid additive. The reverse surfactant includes one or more of fatty alcohol polyvinyl ether (AEO7), fluorocarbon surfactant FM21, and fluorocarbon surfactant FM10. In the fracturing fluid additive, the mass of nano-anti-swelling agent particles accounts for 4.0-10.0 wt% of the total mass of the fracturing fluid additive, the mass of water-soluble vinyl monomer accounts for 20-40 wt% of the total mass of the fracturing fluid additive, the mass of white oil accounts for 15-25 wt% of the total mass of the fracturing fluid additive, the mass of hydrocarbon-fluorocarbon surfactant accounts for 2.0-3.0 wt% of the total mass of the fracturing fluid additive, the mass of ammonium persulfate accounts for 0.0001-0.002 wt% of the total mass of the fracturing fluid additive, the mass of azobisisobutyrazoline hydrochloride accounts for 0.0001-0.005 wt% of the total mass of the fracturing fluid additive, the mass of reverse surfactant accounts for 0.5-3 wt% of the total mass of the fracturing fluid additive, the mass of sodium bisulfite accounts for 0.005-0.025 wt% of the total mass of the fracturing fluid additive, and the balance is water.

2. The fracturing fluid additive prepared by the method for preparing a multifunctional variable viscosity slippery water fracturing fluid as described in claim 1.

3. The application of the fracturing fluid additive as described in claim 2 as drag-reducing water, characterized in that, The fracturing fluid additive is prepared into a 0.05-0.10 wt% aqueous solution to obtain drag-reducing water with a drag reduction rate greater than 70%.

4. The application of the fracturing fluid additive as described in claim 2 as a proppant-carrying fluid, characterized in that, The fracturing fluid additive was prepared into a 1.0 wt% aqueous solution to obtain a proppant-carrying fluid, which, when sheared at 100℃ and 170 s⁻¹ for 2 h, had an apparent viscosity greater than 60 mPa·s.

5. The application of the fracturing fluid additive as described in claim 2 as a proppant-carrying fluid, characterized in that, The fracturing fluid additive is prepared into a 1.0 wt% aqueous solution to obtain a sand-carrying fluid. When the fluid is broken up with 0.05% ammonium persulfate at 60°C, the viscosity of the broken fluid is less than 5 mPa·s within 1 hour, the anti-swelling rate can reach 80%, the surface tension is less than 25 mN / m, and the interfacial tension is less than 2 mN / m.

Images