Integrated fracturing fluid and preparation method thereof

Abstract

The present invention provides an integrated fracturing fluid and a preparation method thereof. The fracturing fluid comprises: 0.02-0.5% drag reducing and tackifying agent, 0.1-0.5% nanoemulsion, 0.02-0.1% nonionic fluorocarbon surfactant, 0.003-0.05% bactericide, 0-0.5% viscosity modifier, 0-0.5% clay stabilizer, 0-0.1% gel breaker, 0.05-0.2% modifier, 0.1-0.5% gas generator, and the balance is water. The preparation method of the fracturing fluid is as follows: adding the drag reducing and tackifying agent to water, adding the bactericide, clay stabilizer, modifier, nanoemulsion, and nonionic fluorocarbon surfactant; adding the viscosity modifier according to the viscosity requirement; then adding the gas generator and gel breaker; or adding the gas generator and gel breaker to a sand mixing tank and mixing them together with the mixed liquid and sand. The integrated fracturing fluid provided by the present invention has low friction, adjustable viscosity, and high sand suspension performance at the same viscosity.

Description

Technical Field

[0001] The invention relates to an integrated fracturing fluid and a preparation method thereof, and belongs to the technical field of oilfield chemistry. Background Art

[0002] Unconventional gas reservoirs, such as shale oil and gas and tight oil and gas, have become key areas of focus and hotspots in oil and gas exploration and development. Currently, volumetric fracturing is the primary method used to reconstruct these unconventional reservoirs. The required fracturing fluids are primarily slickwater and gels (linear gels, frozen gels, or weak gels). In practice, variable-viscosity slickwater fracturing fluids with adjustable viscosity are more commonly used. Low viscosity fracturing fluids function as standard slickwater fracturing fluids, medium viscosity fracturing fluids function as linear gel fracturing fluids, and high viscosity fracturing fluids function as weak gels or frozen gels. Low-viscosity fracturing fluids offer low friction but poor sand suspension performance, while high-viscosity fracturing fluids offer good sand suspension performance but high friction. Furthermore, excessively high viscosity results in simpler fractures, making it difficult to form a complex fracture network, thus compromising the ultimate fracturing effect. Therefore, developing high-performance integrated fracturing fluids is a key research priority for volumetric fracturing fluids.

[0003] CN110003877A discloses a method for resisting high-mineralization clean viscous and slippery water. The cross-linking agent is an organic boron / zirconium composite cross-linking agent, which is cross-linked with a viscosity-changing and drag-reducing agent to increase viscosity.

[0004] CN111763511A discloses a method for preparing an integrated self-crosslinking thickener-modified polymer for fracturing and its formulation, which can be used to prepare both slickwater and suspended sand fracturing fluids. The thickener is a high-molecular-weight polymer emulsion obtained through inverse emulsion polymerization. The thickener is added at a dosage of 0.06-0.12% in slickwater and 1-2% in suspended sand fracturing fluids. The method utilizes changes in polymer concentration to achieve viscosity variations in slickwater fracturing fluids.

[0005] CN113025302A discloses an integrated self-crosslinking fracturing fluid, which utilizes a self-crosslinking emulsion-type fracturing fluid thickener. By preparing aqueous solutions of different mass fractions as fracturing fluids, i.e., 0.05-0.4% thickener solution is used as a slick water fracturing fluid, and 0.4-2.0wt% thickener solution is used as a suspended sand fracturing fluid. Switching between slick water and suspended sand fluids can be achieved by adjusting the added amount.

[0006] CN112375557A discloses an alcohol-soluble slick water for fracturing, which is composed of 20.0-60.0% of polyacrylamide polymer, 0.5-4.0% of nanoparticles, 0.1-3% of surfactant and organic alcohol.

[0007] CN112126419A discloses a continuously prepared sand suspension solution comprising 1 to 10 parts of a viscosity-changing agent, 1 to 5 parts of a cross-linking agent, 900 to 1000 parts of water, and 20 to 60 parts of a proppant.

[0008] CN111635749A discloses a slickwater system that combines drag reduction and sand suspension. The system is composed of 0.02-0.3 wt% of a fast-dissolving associative polymer drag reducer, 0.01-0.1 wt% of a nonionic surfactant and / or anionic surfactant, 0.1-2 wt% of a clay stabilizer, and water. The viscosity is adjustable within the range of 20 mPa.s.

[0009] CN111647106A discloses a viscoelastic polymer emulsion type slippery water and suspended sand liquid, and adopts inverse emulsion polymerization to prepare nano-scale viscoelastic polymer emulsion, overcoming the disadvantage of low copolymerization rate of existing associative monomers in the inverse emulsion polymerization process.

[0010] Under the same fracturing displacement conditions, the existing technology to improve the suspended sand performance mainly relies on fracturing fluid viscosity increase: relying on increasing the concentration of polymer drag reducers or thickeners to increase viscosity, or relying on cross-linking with cross-linkers at a certain polymer concentration to increase viscosity, or relying on intramolecular and intermolecular association after the concentration of hydrophobic associating polymer drag reducers or thickeners reaches a certain level to increase viscosity.

[0011] However, these existing technologies have at least the following problems: improving the sand-suspending performance requires significantly increasing the concentration of the drag reducer or thickener and the corresponding cross-linking agent concentration, which results in high fracturing fluid costs; under the same conditions, the higher the viscosity of the fracturing fluid, the greater the frictional resistance, resulting in high frictional resistance in the existing technology under high-viscosity conditions, increasing the construction pump pressure; in order to improve the sand-suspending performance, the viscosity of the fracturing fluid is significantly increased, but the excessively high viscosity of the fracturing fluid will result in relatively simple cracks produced by fracturing, and the complexity of the fracture network formed by fracturing is low, which affects the volume fracturing effect. Summary of the Invention

[0012] To solve the above technical problems, the present invention aims to provide an integrated fracturing fluid and a preparation method thereof. The integrated fracturing fluid provided by the present invention has the advantages of low friction, adjustable viscosity, and high sand suspension performance under the same viscosity conditions.

[0013] To achieve the above objectives, the first aspect of the present invention provides an integrated fracturing fluid, which includes the following components, in mass percentage: 0.02%-0.5% of a drag reducing and tackifying agent, 0.1%-0.5% of a nanoemulsion, 0.02%-0.1% of a first non-ionic fluorocarbon surfactant, 0.003%-0.05% of a fungicide, 0-0.5% of a viscosity regulator, 0-0.5% of a clay stabilizer, 0-0.1% of a gel breaker, 0.05%-0.2% of a modifier, 0.1%-1% of a gas generating agent, and the balance being water.

[0014] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid contains a viscosity regulator, based on the total mass of the integrated fracturing fluid as 100%, the content of the viscosity regulator can generally be controlled to be 0.1-0.5%.

[0015] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid contains a breaker, based on the total mass of the integrated fracturing fluid as 100%, the content of the breaker can generally be controlled to be 0.02-0.1%.

[0016] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid contains a clay stabilizer, based on the total mass of the integrated fracturing fluid as 100%, the content of the clay stabilizer can generally be controlled to be 0.01-0.5%.

[0017] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid is a low viscosity fracturing fluid (kinematic viscosity ≤ 5 mm 2 / s), it includes the following components, calculated by mass percentage: 0.02%-0.05% of a drag reducing and viscosity increasing agent, 0.1%-0.5% of a nanoemulsion, 0.02%-0.1% of a first nonionic fluorocarbon surfactant, 0.003%-0.05% of a fungicide, 0-0.5% of a clay stabilizer, 0.05%-0.2% of a modifier, 0.1%-0.5% of a gas generating agent, and the balance is water. More preferably, when the integrated fracturing fluid is a low-viscosity fracturing fluid, it includes the following components, calculated by mass percentage: 0.03%-0.05% of a drag reducing and tackifying agent, 0.1%-0.4% of a nanoemulsion, 0.02%-0.08% of a first non-ionic fluorocarbon surfactant, 0.005%-0.02% of a fungicide, 0.1%-0.3% of a clay stabilizer, 0.08%-0.15% of a modifier, 0.2%-0.4% of a gas generating agent, and the balance is water.

[0018] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid is a medium-viscosity fracturing fluid (apparent viscosity of 12-30 mPa·s), it includes the following components, by mass percentage: 0.2%-0.5% of a drag reducing and tackifying agent, 0.1%-0.5% of a nanoemulsion, 0.02%-0.1% of a first non-ionic fluorocarbon surfactant, 0.003%-0.05% of a fungicide, 0-0.5% of a clay stabilizer, 0.02-0.1% of a gel breaker, 0.05%-0.2% of a modifier, 0.1%-0.5% of a gas generating agent, and the balance is water. More preferably, when the integrated fracturing fluid is a medium-viscosity fracturing fluid, it includes the following components, calculated by mass percentage: 0.2%-0.4% of a drag reducing and tackifying agent, 0.1%-0.4% of a nanoemulsion, 0.02%-0.08% of a first non-ionic fluorocarbon surfactant, 0.005%-0.02% of a fungicide, 0.1%-0.3% of a clay stabilizer, 0.02%-0.08% of a gel breaker, 0.08%-0.15% of a modifier, 0.2%-0.4% of a gas generating agent, and the balance is water.

[0019] According to a specific embodiment of the present invention, preferably, when the integrated fracturing fluid is a high-viscosity fracturing fluid (apparent viscosity of 50-200 mPa·s), it includes the following components, by mass percentage: 0.3%-0.5% of a drag reducing and tackifying agent, 0.1%-0.5% of a nanoemulsion, 0.02%-0.1% of a first non-ionic fluorocarbon surfactant, 0.003%-0.05% of a bactericide, 0.1-0.5% of a viscosity regulator, 0-0.5% of a clay stabilizer, 0.06-0.1% of a gel breaker, 0.05%-0.2% of a modifier, 0.1%-0.5% of a gas generating agent, and the balance is water. More preferably, when the integrated fracturing fluid is a high-viscosity fracturing fluid, it includes the following components, calculated by mass percentage: 0.3%-0.5% of a drag reducing and tackifying agent, 0.1%-0.4% of a nanoemulsion, 0.02%-0.08% of a first non-ionic fluorocarbon surfactant, 0.005%-0.02% of a bactericide, 0.25%-0.45% of a viscosity regulator, 0.1%-0.3% of a clay stabilizer, 0.06-0.1% of a gel breaker, 0.08%-0.15% of a modifier, 0.2%-0.4% of a gas generating agent, and the balance is water.

[0020] In the above-mentioned integrated fracturing fluid, preferably, the drag reducing and viscosity increasing agent is a mixture of hydrolyzed polyacrylamide and / or its derivatives and non-hydrolyzed polyacrylamide and / or its derivatives. More preferably, the mass ratio of the hydrolyzed polyacrylamide and / or its derivatives to the non-hydrolyzed polyacrylamide and / or its derivatives is (10-15):1.

[0021] In the above-mentioned integrated fracturing fluid, preferably, in the drag reducing and tackifying agent, the viscosity average molecular weight of the hydrolyzed polyacrylamide and / or its derivatives is 5 million to 15 million, and the degree of hydrolysis is 20% to 30%; the viscosity average molecular weight of the non-hydrolyzed polyacrylamide and / or its derivatives is 5 million to 15 million.

[0022] The drag-reducing and viscosity-increasing agent used in the fracturing fluid of the present invention is a mixture of hydrolyzed polyacrylamide and / or its derivatives and non-hydrolyzed polyacrylamide and / or its derivatives, with a mass ratio of (10-15):1 and a viscosity-average molecular weight of 5 million to 15 million. The hydrolyzed polyacrylamide contains a large number of carboxyl groups, which, at a certain concentration, undergo cross-linking with the central ions of the cross-linking agent (i.e., the viscosity modifier of the present invention), thereby forming a network structure, significantly increasing the viscosity of the fracturing fluid and improving the sand-suspending performance by virtue of the high viscosity. The non-hydrolyzed polyacrylamide, on the other hand, is used at a lower concentration than the hydrolyzed polyacrylamide and, at a certain concentration, does not undergo cross-linking with the central ions of the cross-linking agent (i.e., the viscosity modifier of the present invention), remaining in a non-cross-linked linear polymer state and expanding in the fracturing fluid, thereby ensuring that the fracturing fluid still has high drag-reducing properties under high viscosity conditions. Therefore, the present invention overcomes the contradiction between low friction and high sand-suspending properties of the fracturing fluid by combining hydrolyzed polyacrylamide and / or its derivatives with non-hydrolyzed polyacrylamide and / or its derivatives in a specific ratio.

[0023] In the above-mentioned integrated fracturing fluid, preferably, the nanoemulsion is a nanoemulsion with an average particle size of ≤150 nm.

[0024] In the above-mentioned integrated fracturing fluid, preferably, based on the total mass of the nanoemulsion as 100%, it includes the following components: 10%-20% fluorine-containing silicone oil, 5%-10% gemini fluorocarbon surfactant, 15%-25% second nonionic fluorocarbon surfactant, 5%-10% nano-silica, 1%-10% lower alcohol, and the balance is water.

[0025] In the above-mentioned integrated fracturing fluid, preferably, in the nanoemulsion, the fluorine-containing silicone oil includes one or a combination of hydroxy fluorosilicone oil, vinyl fluorosilicone oil, methyl fluorosilicone oil and polyether fluorosilicone oil.

[0026] In the above-mentioned integrated fracturing fluid, preferably, in the nanoemulsion, the general structural formula of the gemini fluorocarbon surfactant is: n F 2n+1 N + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C n F 2n+1 , where n is 2-4.

[0027] More preferably, the gemini fluorocarbon surfactant is prepared by the following steps: in parts by weight, at 20-40° C., 1-3 parts of fluorine-containing brominated alkanes are added to a solvent, stirred and mixed evenly (the stirring speed is preferably 100-300 rpm), and then 0.5-1.5 parts of tetramethylbutanediamine are added dropwise (the dropping speed is preferably uniformly added within 10-20 minutes), and a quaternization reaction is carried out under stirring (the stirring speed is preferably 100-300 rpm). After reacting for 0.5-2 hours, the resulting precipitate is the gemini fluorocarbon surfactant. Among them, it is particularly preferred that the fluorine-containing brominated alkanes include one or more combinations of heptafluoro-2-bromopropane, pentafluorobromoethane, and 1-nonafluorobutyl bromide. The solvent may include acetone, etc., and its amount may be 7-10 parts by weight. In addition, the precipitate obtained after the reaction can be subjected to conventional filtering, washing, and other operations, and the present invention does not specifically limit these conventional operations.

[0028] In the above-mentioned integrated fracturing fluid, preferably, in the nanoemulsion, the second non-ionic fluorocarbon surfactant includes one or more of the following: polyoxyethylene ethers of fluorinated fatty alcohols, polyoxyethylene ethers of fluorinated phenols, polyoxyethylene ethers of fluorinated alkylsulfonyl alcoholamines, polyoxyethylene esters of fluorinated carboxylic acids, and polyoxyethylene ethers of fluorinated thiols. More specifically, the second non-ionic fluorocarbon surfactant includes, but is not limited to, one or more of the following: DuPont's Capstone FS-30 non-ionic fluorocarbon surfactant, Guangzhou Shunrun New Material Technology Co., Ltd.'s FCF-204 non-ionic fluorocarbon surfactant, 3M's FC4430 non-ionic fluorocarbon surfactant, 3M's FC4432 non-ionic fluorocarbon surfactant, Sichuan Kehongda Group's KHD011 non-ionic fluorocarbon surfactant, Guangzhou Kanglun Xifu Silicone Technology Co., Ltd.'s KX-109 non-ionic fluorocarbon surfactant, DuPont's Capstone FS-3100 non-ionic fluorocarbon surfactant, Anhui Jinao Chemical Co., Ltd.'s AF4018-Y non-ionic fluorocarbon surfactant, and the like.

[0029] In the above-mentioned integrated fracturing fluid, preferably, in the nanoemulsion, the particle size of the nano-silica is 15-50 nm.

[0030] In the above-mentioned integrated fracturing fluid, preferably, in the nanoemulsion, the lower alcohol includes one or a combination of methanol, ethanol, propanol and butanol.

[0031] In the above-mentioned integrated fracturing fluid, preferably, the nanoemulsion is prepared by the following steps: according to the content of each component in the above-mentioned nanoemulsion, add a gemini fluorocarbon surfactant and a nonionic fluorocarbon surfactant to water at 10-40°C and a stirring speed of 120-600rpm, and then stir for 10-30 minutes; then add a lower alcohol and continue stirring for 10-30 minutes; then add nano-silicon dioxide and continue stirring for 10-30 minutes; then add fluorine-containing silicone oil dropwise and continue stirring for 30-60 minutes; finally, use ultrasonic treatment for 20-40 minutes to obtain the nanoemulsion. More preferably, the frequency of the ultrasonic wave is 15-20 kHz. Preferably, the dripping speed of the fluorine-containing silicone oil is 30 minutes and the dripping is completed evenly.

[0032] The fracturing fluid of the present invention adopts the above-mentioned nanoemulsion with an average droplet diameter of ≤150nm, which can enter the fine cracks of the formation and play the role of gas-liquid replacement and improving formation imbibition.

[0033] In the above-mentioned integrated fracturing fluid, preferably, the first non-ionic fluorocarbon surfactant comprises one or more of the following: polyoxyethylene ethers of fluorinated fatty alcohols, polyoxyethylene ethers of fluorinated phenols, polyoxyethylene ethers of fluorinated alkylsulfonyl alcoholamines, polyoxyethylene esters of fluorinated carboxylic acids, and polyoxyethylene ethers of fluorinated thiols. More specifically, the first non-ionic fluorocarbon surfactant includes, but is not limited to, one or more of the following: DuPont's Capstone FS-30 non-ionic fluorocarbon surfactant, Guangzhou Shunrun New Material Technology Co., Ltd.'s FCF-204 non-ionic fluorocarbon surfactant, 3M's FC4430 non-ionic fluorocarbon surfactant, 3M's FC4432 non-ionic fluorocarbon surfactant, Sichuan Kehongda Group's KHD011 non-ionic fluorocarbon surfactant, Guangzhou Kanglun Xifu Silicone Technology Co., Ltd.'s KX-109 non-ionic fluorocarbon surfactant, DuPont's Capstone FS-3100 non-ionic fluorocarbon surfactant, Anhui Jinao Chemical Co., Ltd.'s AF4018-Y non-ionic fluorocarbon surfactant, and the like. The first nonionic fluorocarbon surfactant can synergistically act with the nanoemulsion of the present invention to reduce the surface tension of the fracturing fluid and reduce the capillary resistance of the fracturing fluid flowing in fine fractures of the formation.

[0034] In the above-mentioned integrated fracturing fluid, preferably, the bactericide includes one or a combination of aldehyde bactericides, quaternary ammonium salt bactericides, and isothiazolinone bactericides.

[0035] In the above-mentioned integrated fracturing fluid, preferably, the aldehyde fungicide includes one or a combination of glutaraldehyde, formaldehyde and acrolein.

[0036] In the above-mentioned integrated fracturing fluid, preferably, the quaternary ammonium salt fungicide includes one or a combination of tetradecyldimethylbenzylammonium chloride, dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride and dodecyldimethylbenzylammonium bromide.

[0037] In the above-mentioned integrated fracturing fluid, preferably, the isothiazolinone fungicide includes methylisothiazolinone and / or methylchloroisothiazolinone.

[0038] The bactericide used in the fracturing fluid of the present invention can kill bacteria in the fracturing fluid and inhibit bacterial growth, thereby avoiding problems such as corrosion caused by bacterial growth and blockage of fine cracks caused by bacterial metabolites.

[0039] In the above-mentioned integrated fracturing fluid, the viscosity modifier preferably comprises one or a combination of water-soluble zirconium salts, water-soluble titanium salts, water-soluble chromium salts, and water-soluble aluminum salts. More preferably, the viscosity modifier comprises one or a combination of water-soluble organic zirconium salts, water-soluble organic titanium salts, water-soluble organic chromium salts, and water-soluble organic aluminum salts obtained by complexing water-soluble zirconium salts, water-soluble titanium salts, water-soluble chromium salts, and water-soluble organic aluminum salts with polyhydroxy alcohols. The viscosity modifier used in the present invention can cross-link with the hydrolyzed polyacrylamide and / or its derivatives in the drag reducing and tackifying agent of the present invention to significantly increase the viscosity of the fracturing fluid.

[0040] In the integrated fracturing fluid described above, the water-soluble organic zirconium salt preferably comprises a complex obtained by a complexation reaction between zirconium oxychloride and one or more of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, diethylene glycol ether, and triethylene glycol. More specifically, in the complexation reaction, the mass ratio of zirconium oxychloride to polyhydroxy alcohol may be (5-20):(80-95), the complexation reaction temperature may be 50-90°C, and the reaction time may be 1-6 hours.

[0041] In the above-mentioned integrated fracturing fluid, preferably, the water-soluble organic titanium salt includes one or more of di(triethanolamine)diisopropyl titanate, tetraisopropyl orthotitanate, diisopropyl orthotitanate dilactate and diisopropyl orthotitanate diacetylacetonate, etc.; or a complex obtained by the complexation reaction of one or more of the combination of di(triethanolamine)diisopropyl titanate, tetraisopropyl orthotitanate, diisopropyl orthotitanate dilactate and diisopropyl orthotitanate diacetylacetonate with one or more of the combination of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol ether and triethylene glycol. More specifically, in the complex reaction, the mass ratio of one or more of diisopropyl di(triethanolamine)titanate, tetraisopropyl orthotitanate, diisopropyl orthotitanate dilactate, and diisopropyl orthotitanate diacetylacetonate to the polyhydroxy alcohol can be (5-20):(80-95), the complex reaction temperature can be 50-90°C, and the reaction time can be 1-6h.

[0042] In the integrated fracturing fluid described above, preferably, the water-soluble organic chromium salt comprises a complex obtained by a complex reaction between one or more combinations of chromium lactate, chromium acetate, chromium chloride, and chromium sulfate and one or more combinations of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol ether, and triethylene glycol. More specifically, in the complex reaction, the mass ratio of one or more combinations of chromium lactate, chromium acetate, chromium chloride, and chromium sulfate to the polyhydroxy alcohol can be (10-20):(80-90), the complex reaction temperature can be 50-90°C, and the reaction time can be 1-3 hours.

[0043] In the above-mentioned integrated fracturing fluid, preferably, the water-soluble organic aluminum salt comprises a complex obtained by a complex reaction between one or more combinations of potassium aluminum sulfate dodecahydrate, aluminum sulfate, aluminum lactate, aluminum acetate, and aluminum chloride and one or more combinations of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol ether, and triethylene glycol. More specifically, in the complex reaction, the mass ratio of one or more combinations of potassium aluminum sulfate dodecahydrate, aluminum sulfate, aluminum lactate, aluminum acetate, and aluminum chloride to the polyhydroxy alcohol can be (15-25):(75-85), the complex reaction temperature can be 50-90°C, and the reaction time can be 1-3 hours.

[0044] In the above-mentioned integrated fracturing fluid, preferably, the clay stabilizer includes one or a combination of tetramethylammonium chloride, potassium chloride, and polyquaternium salt.

[0045] In the aforementioned integrated fracturing fluid, the breaker preferably comprises one or a combination of ammonium persulfate, sodium persulfate, and potassium persulfate. The breaker employed in the present invention can, through its oxidation action, break and degrade the gel produced by the drag-reducing viscosity-enhancing agent and the cross-linking of the drag-reducing viscosity-enhancing agent with the viscosity modifier, thereby reducing the adhesion and clogging damage of the polymer to the formation.

[0046] In the above-mentioned integrated fracturing fluid, preferably, the modifier includes a silane modifier. More preferably, the silane modifier includes one or more of N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, and N-β-aminoethyl-γ-aminopropyltrimethoxysilane. The modifier used in the present invention can be adsorbed on the surface of sand (i.e., ceramsite and / or quartz sand, etc.) during the fracturing process, so that the surface of the sand changes from hydrophilic oil-enhancing to lipophilic and hydrophobic, thereby absorbing the dissolved gas in the fracturing fluid and / or the gas generated by the gas generating agent of the present invention, so that the adsorbed gas surrounds the surface of the sand, thereby suspending the sand in the fracturing fluid.

[0047] In the above-mentioned integrated fracturing fluid, preferably, the gas generating agent includes effervescent tablet particles, etc. More preferably, the effervescent tablet particles are effervescent tablet particles with citric acid as the acid source, sodium bicarbonate as the alkali source, and polyethylene glycol as the capsule coating. Particularly preferably, the gas generating agent is prepared by the following steps: dissolving polyethylene glycol (preferably PEG-6000) in water (the temperature of the water can be 80-90°C) to form a viscous substance (the mass fraction of polyethylene glycol in the viscous substance is 60%-90%), and dividing it into two parts (the mass ratio of the two viscous substances can be 1:1-1:1.8); mixing citric acid and sodium bicarbonate with the two viscous substances respectively (the mass ratio of citric acid to the viscous substance can be 1:1-1:1.2, and the mass ratio of sodium bicarbonate to the viscous substance can be 1:1-1:1.2), stirring evenly, drying (the drying temperature can be 30-45°C), and then crushing into powder to obtain acid source powder and alkali source powder respectively; Polyethylene glycol (preferably PEG-800) is added to the acid source powder and the alkali source powder respectively (based on the total weight of the acid source powder and the polyethylene glycol being 100%, the amount of polyethylene glycol added in this step can be 3%-8%; based on the total weight of the alkali source powder and the polyethylene glycol being 100%, the amount of polyethylene glycol added in this step can be 3%-8%), and mixed evenly to obtain an acid source viscous material and an alkali source viscous material, respectively; the acid source viscous material, the alkali source viscous material, and polyethylene glycol (preferably PEG-6000) are mixed in a weight ratio of (1-2):(1-2.5):(0.1-0.2), and after mixing evenly, tableting, granulation (and / or crushing) are obtained to obtain effervescent tablet particles, namely the gas generating agent.

[0048] The gas generating agent used in the present invention can gradually dissolve the polyethylene glycol-wrapped capsule in the fracturing fluid by stirring, thereby allowing the acid source and the alkali source to contact in the fracturing fluid. The acid-base reaction releases carbon dioxide gas, which is adsorbed around the surface of the sand with the modifier adsorbed on the surface, thereby suspending the sand in the fracturing fluid.

[0049] A second aspect of the present invention provides a method for preparing the above-mentioned integrated fracturing fluid, which comprises the following steps:

[0050] When preparing indoors:

[0051] S1. Under stirring conditions of 60-200 rpm, based on the total mass of the integrated fracturing fluid as 100%, add 0.02%-0.5% of the drag reducing and tackifying agent to water (the amount of water is calculated by adding the amounts of other components to make up 100%), and stir to mix evenly;

[0052] S2, then adding 0.003%-0.05% of a fungicide, 0-0.5% of a clay stabilizer, 0.05%-0.2% of a modifier, 0.1%-0.5% of a nanoemulsion, and 0.02%-0.1% of a first nonionic fluorocarbon surfactant, stirring and mixing to obtain a first mixed solution;

[0053] S3. Add 0-0.5% of a viscosity modifier to the first mixed solution according to the viscosity requirement of the desired fracturing fluid, and stir and mix uniformly to obtain a second mixed solution;

[0054] S4. Add 0.1%-1% of a gas generating agent and 0-0.1% of a breaker to the second mixed liquid, and stir evenly to obtain the integrated fracturing fluid (when the fracturing fluid of the present invention does not contain a viscosity modifier, the gas generating agent and the optional breaker are added to the first mixed liquid);

[0055] When preparing on-site:

[0056] The preparation steps of S1-S3 are the same as those for indoor preparation. The preparation steps of S4 are as follows: 0.1%-1% of gas generating agent and 0-0.1% of gel breaker are added to the mixing tank of the sand mixing truck, and mixed evenly with the second mixed liquid and sand in the mixing tank of the sand mixing truck.

[0057] In the preparation method of the present invention, when the integrated fracturing fluid of the present invention is a low-viscosity fracturing fluid, a medium-viscosity fracturing fluid, and a high-viscosity fracturing fluid, respectively, the amount of each component has been described above and will not be repeated here. Those skilled in the art should understand that the fracturing fluid is configured according to the amount of each component in the fracturing fluid of different viscosities described above and the above-mentioned preparation method.

[0058] The integrated fracturing fluid provided by the present invention has the following advantages and beneficial effects:

[0059] Under the same viscosity, the fracturing fluid provided by the present invention has higher sand suspension performance than conventional fracturing fluids, especially low-viscosity slick water fracturing fluids and medium-viscosity linear gel fracturing fluids. The fracturing fluid provided by the present invention has lower friction than conventional fracturing fluids, and the drag reduction rate is increased by 2.1-11.2 percentage points, and the higher the viscosity, the greater the increase in the drag reduction rate. At the same time, the fracturing fluid provided by the present invention has better sand suspension performance than conventional fracturing fluids of the same viscosity, especially in the high-viscosity gel fracturing fluid provided, the suspended sand did not settle within 10 minutes (in conventional gel fracturing fluids of the same viscosity, the suspended sand settled by 10% within 10 minutes). Therefore, the integrated fracturing fluid provided by the present invention has the advantages of low friction, adjustable viscosity, and high sand suspension performance under the same viscosity conditions. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0061] Example 1

[0062] This embodiment provides an integrated fracturing fluid, which includes the following components, in percentage by mass: 0.03% drag reducing and tackifying agent, 0.1% nanoemulsion, 0.02% nonionic fluorocarbon surfactant, 0.005% fungicide, 0.2% clay stabilizer, 0.08% modifier, 0.2% gas generating agent, and the balance is water.

[0063] The drag reducing and thickening agent is a mixture of polyacrylamide with a viscosity average molecular weight of 9.8 million and a hydrolysis degree of 22% and non-hydrolyzed polyacrylamide with a viscosity average molecular weight of 10 million±1 million, and the mass ratio of the two is 12:1.

[0064] The nanoemulsion has an average particle size of 100 nm. Based on the total mass of the nanoemulsion as 100%, it comprises: 15% methyl fluorosilicone oil (Guangzhou Daxi Chemical Raw Materials Co., Ltd., 8012-300), 6% Gemini fluorocarbon surfactant C3F7N + (CH3)2-CH2CH2CH2CH2-(CH3)2N +C3F7 (self-made: in parts by weight, at 25°C, 2 parts of heptafluoro-2-bromopropane are added to 8 parts of acetone, and the mixture is uniformly mixed under stirring at 200 rpm, and then 1 part of tetramethylbutanediamine is added dropwise, and the addition is uniform and complete over 10 minutes. Quaternization reaction is carried out under stirring at 200 rpm. After the reaction is carried out for 1 hour, the precipitate is filtered and the obtained precipitate is the prepared gemini fluorocarbon surfactant), 22% nonionic fluorocarbon surfactant (DuPont, Capstone FS-30), 6% nano-silica with an average particle size of 20 nm, 5% methanol and the balance water.

[0065] The nanoemulsion is prepared by the following steps: according to the content of each component in the nanoemulsion, water is added to the reaction kettle, and the gemini fluorocarbon surfactant C3F7N is stirred at 35°C and 300 rpm. + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C3F7 and a nonionic fluorocarbon surfactant were added to the reaction kettle and stirred for 20 minutes; methanol was then added and the stirring was continued for 20 minutes; nano-silica was then added and the stirring was continued for 20 minutes; methyl fluorosilicone oil was added dropwise at a rate of 30 minutes and the stirring was continued for 40 minutes; finally, ultrasonic treatment with a frequency of 20 kHz was performed for 30 minutes to obtain the nanoemulsion.

[0066] The nonionic fluorocarbon surfactant is Capstone FS-30 produced by DuPont.

[0067] The bactericide is glutaraldehyde.

[0068] The clay stabilizer is tetramethylammonium chloride.

[0069] The modifier is N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane (Wuhan Xinweiye Chemical Co., Ltd.).

[0070] The gas generating agent is an effervescent tablet granule with citric acid as the acid source, sodium bicarbonate as the alkali source, and polyethylene glycol as the coating. It is prepared by the following steps: dissolving polyethylene glycol (PEG-6000) in 80-90°C hot water to form a viscous substance, wherein the mass fraction of polyethylene glycol (PEG-6000) in the viscous substance is 60%-90%, and dividing it into two parts (the mass ratio of the two viscous substances is 1:1); mixing citric acid and sodium bicarbonate with the two viscous substances respectively, the mass ratio of citric acid to the viscous substance is 1:1-1:1.2, and the mass ratio of sodium bicarbonate to the viscous substance is 1:1-1:1.2, and after stirring evenly, drying at 30-45°C, and then crushing into powder to obtain acid source powder and alkali source powder respectively; adding the acid source powder, Polyethylene glycol (PEG-800) is added to the alkali source powder, with the total weight of the acid source powder and the polyethylene glycol (PEG-800) being 100%, and the total weight of the polyethylene glycol (PEG-800) being 3%-8%, and the mixture is mixed uniformly to obtain an acid source viscous material and an alkali source viscous material, respectively; the acid source viscous material, the alkali source viscous material, and the polyethylene glycol (PEG-6000) are mixed in a weight ratio of 2:1:0.1, and after uniform mixing, tableting, granulation, and pulverization are performed to obtain effervescent tablet particles.

[0071] The preparation method of the integrated fracturing fluid of this embodiment includes the following steps: slowly adding 0.03% of the drag reducing and viscosity increasing agent to water under stirring at 100 rpm and stirring and mixing uniformly; then, sequentially adding 0.005% of the fungicide, 0.2% of the clay stabilizer, 0.08% of the modifier, 0.1% of the nanoemulsion, and 0.02% of the non-ionic fluorocarbon surfactant and stirring and mixing uniformly; finally, adding 0.2% of the gas generating agent and stirring uniformly to obtain the integrated fracturing fluid.

[0072] Comparative Example 1-1

[0073] The nanoemulsion was removed from the fracturing fluid components of Example 1, and the remaining components and contents as well as the fracturing fluid preparation method were the same to obtain the fracturing fluid of Comparative Example 1-1.

[0074] Comparative Example 1-2

[0075] The nanoemulsion was replaced in the fracturing fluid components of Example 1, and the remaining components and contents as well as the fracturing fluid preparation method were the same to obtain the fracturing fluid of Comparative Example 1-2.

[0076] The replaced nanoemulsion does not contain the gemini fluorocarbon surfactant C3F7N + (CH3)2-CH2CH2CH2CH2-(CH3)2N +C3F7, and other components and contents are the same as those in Example 1. It is prepared by the following steps: according to the contents of the components in the above-mentioned nanoemulsion, water is added to the reactor, a nonionic fluorocarbon surfactant (DuPont, Capstone FS-30) is added to the reactor at 35°C and a stirring speed of 300 rpm, and stirred for 20 minutes; methanol is then added and stirring is continued for 20 minutes; nano-silica is then added and stirring is continued for 20 minutes; methyl fluorosilicone oil is added dropwise at a speed of 30 minutes, and stirring is continued for 40 minutes to obtain the nanoemulsion.

[0077] Conventional slickwater fracturing fluid A:

[0078] Based on the total mass of the conventional slick water fracturing fluid A as 100%, it is prepared by 0.1% of a polyacrylamide emulsion with a viscosity-average molecular weight of 9.9 million and a degree of hydrolysis of 25% (Chengdu Nengte Technology Development Co., Ltd., CT1-20D), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), and the balance of water.

[0079] Conventional slickwater fracturing fluid B:

[0080] Based on the total mass of the conventional slick water fracturing fluid B as 100%, it is prepared by 0.03% of a hydrophobically associating polymer powder with a viscosity-average molecular weight of 8.8 million (Chengdu Nengte Technology Development Co., Ltd., CT1-20B), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), and the balance water.

[0081] The fracturing fluids prepared in Example 1 and Comparative Examples 1-1 and 1-2 had low viscosities. The main properties of the fracturing fluids were tested in accordance with the industry standard NB / T 14003.1-2015, "Shale Gas Fracturing Fluids - Part 1: Slickwater Performance Indicators and Evaluation Methods." The test results for the main properties of the fracturing fluids are shown in Table 1.

[0082] Table 1 Main properties of fracturing fluids of Example 1 and Comparative Example 1-1 and Comparative Example 1-2

[0083]

[0084] The suspended sand performance test was performed according to the following steps: 500mL of Example 1 fracturing fluid, Comparative Example 1-1 fracturing fluid, Comparative Example 1-2 fracturing fluid, conventional slick water fracturing fluid A, and conventional slick water fracturing fluid B were poured into the Wu Yin mixer, 150g of 40-70 mesh ceramsite was added to the Wu Yin mixer, and after stirring at a stirring speed of 500 revs / min for 2 minutes, all were immediately poured into a 1000mL graduated cylinder, the timing was started, and the ceramsite sedimentation was recorded to characterize the suspended sand performance of the fracturing fluid. The slower the ceramsite sedimentation, the better the suspended sand performance of the fracturing fluid. The suspended sand performance test results are shown in Table 2.

[0085] Table 2 Fracturing fluid sand suspension performance of Example 1 and Comparative Example 1-1 and Comparative Example 1-2

[0086]

[0087]

[0088] As can be seen from Tables 1 and 2 above, compared with Example 1, after removing the nanoemulsion from the fracturing fluid formula in Comparative Example 1-1, the exclusion rate is greatly reduced (from 62% to 42%), indicating that the nanoemulsion in Example 1 can improve the flow properties of the fracturing fluid in fine cracks and increase the backflow rate through effects such as dialysis, which is very beneficial for reducing the damage of the fracturing fluid; other properties have not changed significantly.

[0089] Compared with Example 1, in Comparative Examples 1-2, after the nanoemulsion composition in the fracturing fluid formula was changed (the Gemini fluorocarbon surfactant and the ultrasonic treatment were removed), the exclusion rate was significantly reduced (from 62% to 45%), indicating that the nanoemulsion in Example 1 can improve the flow properties of the fracturing fluid in fine cracks and increase the flowback rate through dialysis and other effects, which is very beneficial for reducing the damage of the fracturing fluid; other properties did not change significantly; the nanoemulsions in Comparative Examples 1-2 did not achieve the same effect as the nanoemulsion in Example 1.

[0090] Compared with Example 1, the drag reduction rates of conventional slickwater fracturing fluids A and B were reduced by 2.1 percentage points and 10.1 percentage points, respectively. The sand suspension performance of conventional slickwater fracturing fluids A and B was changed from "starting to settle after 20 seconds, half settling in 3 minutes, and completely settling in 10 minutes" in Example 1 to "starting to settle at 0 seconds and completely settling in 10 seconds", indicating that the fracturing fluid of Example 1 improved the drag reduction performance of low-viscosity slickwater fracturing fluids and significantly improved the sand suspension performance of low-viscosity slickwater fracturing fluids.

[0091] Example 2

[0092] This embodiment provides an integrated fracturing fluid, which includes the following components, in percentage by mass: 0.2% drag reducing and tackifying agent, 0.2% nanoemulsion, 0.03% nonionic fluorocarbon surfactant, 0.004% fungicide, 0.2% clay stabilizer, 0.02% gel breaker, 0.1% modifier, 0.3% gas generating agent, and the balance is water.

[0093] The drag reducing and thickening agent is a mixture of polyacrylamide with a viscosity average molecular weight of 11.7 million and a hydrolysis degree of 28% and non-hydrolyzed polyacrylamide with a viscosity average molecular weight of 11.5 million, and the mass ratio of the two is 14:1.

[0094] The nanoemulsion has an average particle size of 130 nm. Based on the total mass of the nanoemulsion as 100%, it includes: 18% hydroxy fluorosilicone oil (Wuhan Rongcan Biotechnology Co., Ltd.), 7% Gemini fluorocarbon surfactant C2F5N + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C2F5 (self-made: in parts by weight, at 30°C, 1.5 parts of pentafluorobromoethane were added to 7 parts of acetone, and the mixture was stirred at 150 rpm, followed by dropwise addition of 1 part of tetramethylbutanediamine. The mixture was added evenly over 12 minutes, and quaternization reaction was carried out under stirring at 150 rpm. After 1.5 hours of reaction, the precipitate was filtered and the obtained precipitate was the prepared gemini fluorocarbon surfactant), 20% non-ionic fluorocarbon surfactant (Guangzhou Shunrun New Material Technology Co., Ltd., FCF-204), 5% nano-silica with an average particle size of 20 nm, 7% ethanol and the balance water.

[0095] The nanoemulsion is prepared by the following steps: the content of each component in the nanoemulsion is adjusted, water is added to the reaction kettle, and the gemini fluorocarbon surfactant C2F5N is stirred at 35°C and 300rpm. + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C2F5 and a nonionic fluorocarbon surfactant were added to a reaction kettle and stirred for 30 minutes; ethanol was then added and the stirring was continued for 15 minutes; nano-silica was then added and the stirring was continued for 20 minutes; hydroxy fluorosilicone oil was added dropwise at a speed of 30 minutes and the stirring was continued for 45 minutes; and finally, ultrasonic treatment with a frequency of 16 kHz was performed for 30 minutes to obtain the nanoemulsion.

[0096] The nonionic fluorocarbon surfactant is FCF-204 produced by Guangzhou Shunrun New Material Technology Co., Ltd.

[0097] The bactericide is dodecyltrimethylammonium chloride.

[0098] The clay stabilizer is a polyquaternium salt.

[0099] The gel breaker is potassium persulfate.

[0100] The modifier is 3-aminopropyltriethoxysilane.

[0101] The gas generating agent is an effervescent tablet granule in which the acid source is citric acid, the alkali source is sodium bicarbonate, and the polyethylene glycol is used as a coating. The specific preparation steps are the same as those in Example 1.

[0102] The preparation method of the integrated fracturing fluid of this embodiment includes the following steps: slowly adding 0.2% of the drag reducing and viscosity increasing agent to water under stirring at 150 rpm and stirring to mix evenly; then, sequentially adding 0.004% of the fungicide, 0.2% of the clay stabilizer, 0.1% of the modifier, 0.2% of the nanoemulsion, and 0.03% of the non-ionic fluorocarbon surfactant and stirring to mix evenly; finally, adding 0.3% of the gas generating agent and 0.02% of the gel breaker and stirring to mix evenly to obtain the integrated fracturing fluid.

[0103] Comparative Example 2

[0104] The modifier and gas generating agent were removed from the fracturing fluid components of Example 2, and the remaining components and contents as well as the fracturing fluid preparation method were the same to obtain the fracturing fluid of Comparative Example 2.

[0105] Conventional linear gel fracturing fluid C:

[0106] Based on the total mass of the conventional linear gel fracturing fluid C as 100%, it is prepared by 0.4% of a polyacrylamide emulsion with a viscosity-average molecular weight of 9.9 million and a degree of hydrolysis of 25% (Chengdu Nengte Technology Development Co., Ltd., CT1-20D), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), and the balance water.

[0107] Conventional linear gel fracturing fluid D:

[0108] Based on the total mass of the conventional linear gel fracturing fluid D as 100%, it is prepared by 0.25% of a hydrophobically associating polymer powder with a viscosity-average molecular weight of 8.8 million (Chengdu Nengte Technology Development Co., Ltd., CT1-20B), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), and the balance of water.

[0109] The fracturing fluids prepared in Example 2 and Comparative Example 2 were medium-viscosity fracturing fluids. Their primary properties were tested according to the industry standard NB / T 14003.3-2017, "Shale Gas Fracturing Fluids - Part 3: Continuously Mixed Fracturing Fluid Performance Indicators and Evaluation Methods." Bacterial content was tested according to the industry standard NB / T 14003.1-2015, "Shale Gas Fracturing Fluids - Part 1: Slickwater Performance Indicators and Evaluation Methods." The results of the primary fracturing fluid properties are shown in Table 3. Suspended sand performance was tested according to the method described in Example 1, and the results are shown in Table 4.

[0110] Table 3 Main properties of fracturing fluids of Example 2 and Comparative Example 2

[0111]

[0112] Table 4 Fracturing fluid sand suspension performance of Example 2 and Comparative Example 2

[0113]

[0114] It can be seen from Tables 3 and 4 above that, compared with Example 2, after the modifier and gas generating agent are removed from the fracturing fluid formula of Comparative Example 2, the discharge rate is reduced from 55% to 45%, indicating that the modifier and gas generating agent in Example 2 can improve the flow properties of the fracturing fluid in fine cracks and increase the flowback rate by generating gas energy; at the same time, after the modifier and gas generating agent are removed from the fracturing fluid formula of Comparative Example 2, the sand suspension performance changes from "starting to settle after 1 minute, settling half after 5 minutes, and no obvious further settling from the 5th minute to the 10th minute" in Example 2 to "starting to settle after 2 seconds, settling half after 30 seconds, and completely settling after 90 seconds", indicating that the fracturing fluid of Example 2 greatly improves the sand suspension performance of the medium-viscosity slick water fracturing fluid; other properties have not changed significantly.

[0115] Compared with Example 2, the drag reduction rates of conventional linear gel fracturing fluids C and D were reduced by 7.3 percentage points and 2.3 percentage points, respectively. The sand suspension performance of conventional linear gel fracturing fluids C and D changed from "starting to settle after 1 minute, settling halfway after 5 minutes, and no obvious further settling from the 5th to the 10th minute" in Example 2 to "starting to settle after 2 seconds, settling halfway after 20 seconds, and completely settling after 1 minute." This shows that the fracturing fluid of Example 2 improves the drag reduction performance of medium-viscosity slick water and significantly improves the sand suspension performance of low-viscosity slick water fracturing fluids.

[0116] Example 3

[0117] This embodiment provides an integrated fracturing fluid, which includes the following components, in percentage by mass: 0.3% drag reducing and tackifying agent, 0.3% nanoemulsion, 0.05% nonionic fluorocarbon surfactant, 0.01% fungicide, 0.3% viscosity regulator, 0.2% clay stabilizer, 0.08% gel breaker, 0.15% modifier, 0.2% gas generating agent, and the balance is water.

[0118] The drag reducing and thickening agent is a mixture of polyacrylamide with a viscosity average molecular weight of 8.1 million and a hydrolysis degree of 22% and non-hydrolyzed polyacrylamide with a viscosity average molecular weight of 780, and the mass ratio of the two is 10:1.

[0119] The nanoemulsion has an average particle size of 130 nm. Based on the total mass of the nanoemulsion as 100%, it includes: 15% vinyl fluorosilicone oil (Guangzhou Kangxi Organic Silicone Material Co., Ltd., KX-205), 5% Gemini fluorocarbon surfactant C2F5N + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C2F5 (self-made: in parts by weight, at 30°C, 1.5 parts of pentafluorobromoethane were added to 7 parts of acetone, and the mixture was stirred at 150 rpm, followed by dropwise addition of 1 part of tetramethylbutanediamine. The mixture was added dropwise evenly over 12 minutes, and quaternization reaction was carried out under stirring at 150 rpm. After 1.5 hours of reaction, the precipitate was filtered and the obtained precipitate was the prepared gemini fluorocarbon surfactant), 20% nonionic fluorocarbon surfactant (3M Company, FC4430), 5% nano-silica with an average particle size of 30 nm, 9% propanol and the balance water.

[0120] The nanoemulsion is prepared by the following steps: according to the content of each component in the nanoemulsion, water is added to the reaction kettle, and the gemini fluorocarbon surfactant C2F5N is stirred at 30°C and 300 rpm. + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C2F5 and a nonionic fluorocarbon surfactant were added to the reaction kettle and stirred for 15 minutes; propanol was then added and the stirring was continued for 20 minutes; nano-silica was then added and the stirring was continued for 25 minutes; vinyl fluorosilicone oil was then added dropwise at a rate of 30 minutes and the stirring was continued for 40 minutes; finally, ultrasonic treatment was performed with a frequency of 18 kHz for 25 minutes to obtain the nanoemulsion.

[0121] The nonionic fluorocarbon surfactant is FC4430 from 3M Company.

[0122] The bactericide is methylisothiazolinone.

[0123] The viscosity modifier is a complex formed by a complexation reaction between zirconium oxychloride and sorbitol. The viscosity modifier is prepared by mixing zirconium oxychloride, sorbitol, and water in a weight ratio of 20:50:30, and reacting the mixture at 60°C for 1 hour to obtain the viscosity modifier.

[0124] The clay stabilizer is potassium chloride.

[0125] The gel breaker is ammonium persulfate.

[0126] The modifier is N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

[0127] The gas generating agent is an effervescent tablet granule in which the acid source is citric acid, the alkali source is sodium bicarbonate, and the polyethylene glycol is used as a coating. The specific preparation steps are the same as those in Example 1.

[0128] The preparation method of the integrated fracturing fluid of this embodiment includes the following steps: slowly adding 0.3% of the drag reducing and viscosity increasing agent to water under stirring at 150 rpm and stirring and mixing uniformly; then, sequentially adding 0.01% of the fungicide, 0.2% of the clay stabilizer, 0.15% of the modifier, 0.3% of the nanoemulsion, and 0.05% of the non-ionic fluorocarbon surfactant and stirring and mixing uniformly; then, adding 0.3% of the viscosity modifier and stirring and mixing uniformly; and finally, adding 0.2% of the gas generating agent and 0.08% of the gel breaker and stirring uniformly to obtain the integrated fracturing fluid.

[0129] Comparative Example 3-1

[0130] In the fracturing fluid components of Example 3, all 0.3% of the drag reducing and tackifying agent was replaced with hydrolyzed polyacrylamide (without non-hydrolyzed polyacrylamide) with a molecular weight of 8.1 million and a degree of hydrolysis of 22%. The remaining components and contents and the fracturing fluid preparation method were the same to obtain the fracturing fluid of Comparative Example 3-1.

[0131] Comparative Example 3-2

[0132] In the fracturing fluid components of Example 3, the mass percentage of the drag reducing and viscosity increasing agent in the fracturing fluid was replaced with 0.7%, and the remaining components and contents and the fracturing fluid preparation method were the same to obtain the fracturing fluid of Comparative Example 3-2.

[0133] Conventional gel fracturing fluid E:

[0134] Based on the total mass of the conventional gel fracturing fluid E as 100%, it is prepared by 0.4% of a polyacrylamide emulsion with a viscosity-average molecular weight of 9.9 million and a degree of hydrolysis of 25% (Chengdu Nengte Technology Development Co., Ltd., CT1-20D), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), 0.4% of an organic zirconium crosslinking agent (which is the same as the viscosity modifier in Example 3), and the remainder of water.

[0135] Conventional gel fracturing fluid F:

[0136] Based on the total mass of the conventional gel fracturing fluid F as 100%, it is prepared by: 0.25% of a hydrophobically associating polymer powder with a viscosity-average molecular weight of 8.8 million (Chengdu Nengte Technology Development Co., Ltd., CT1-20B), 0.1% of a drainage aid (Chengdu Nengte Technology Development Co., Ltd., CT5-12), 0.005% of a fungicide (Chengdu Nengte Technology Development Co., Ltd., CT10-4), 0.4% of an organic zirconium crosslinker (which is the same as the viscosity modifier in Example 3), and the balance water.

[0137] The fracturing fluids prepared in Example 3 and Comparative Examples 3-1 and 3-2 are high-viscosity fracturing fluids. The main properties of the fracturing fluids were tested according to the industry standard NB / T 14003.3-2017, "Shale Gas Fracturing Fluids - Part 3: Performance Indicators and Evaluation Methods for Continuously Mixed Fracturing Fluids." Bacterial content was tested according to the industry standard NB / T 14003.1-2015, "Shale Gas Fracturing Fluids - Part 1: Performance Indicators and Evaluation Methods for Slickwater." The test results for the main properties of the fracturing fluids are shown in Table 5. The sand suspension performance was tested according to the test method in Example 1, and the test results are shown in Table 6.

[0138] Table 5 Main properties of fracturing fluids of Example 3 and Comparative Examples 3-1 and 3-2

[0139]

[0140] Table 6 Fracturing fluid sand suspension performance of Example 3 and Comparative Example 3-1 and Comparative Example 3-2

[0141]

[0142]

[0143] As can be seen from Tables 5 and 6 above, compared with Example 3, in Comparative Example 3-1, after all the drag-reducing and viscosity-increasing agents in the fracturing fluid formula were replaced with hydrolyzed polyacrylamide (without non-hydrolyzed polyacrylamide), the drag reduction rate decreased from 71.2% to 61.1%. This indicates that the non-hydrolyzed polyacrylamide in Example 3 does not participate in cross-linking and can maintain a linear polymer state, thereby ensuring a high drag reduction rate, while the hydrolyzed polyacrylamide participates in cross-linking to form a spatial network structure, which reduces the drag reduction rate; other properties do not change significantly.

[0144] Compared with Example 3, in Comparative Example 3-2, after the concentration of the drag reducing and thickening agent in the fracturing fluid formula was increased to 0.7%, the drag reduction rate decreased from 71.2% to 35.1%, and the whole frozen gel could not be restored after being gelled and then crushed, indicating that too high a concentration of the drag reducing and thickening agent will lead to over-crosslinking, brittle colloid, increased friction resistance of the fracturing fluid, and reduced drag reduction rate.

[0145] Compared with Example 3, the drag reduction rates of conventional jelly fracturing fluids E and F were reduced by 11.2 percentage points and 6.2 percentage points, respectively, while the sand suspension performance changed from "no obvious sedimentation within 10 minutes" in Example 3 to "10% sedimentation of ceramsite in 10 minutes", indicating that Example 3 significantly improved the drag reduction and sand suspension performance of the high-viscosity jelly fracturing fluid.

[0146] Example 4

[0147] This embodiment provides an integrated fracturing fluid, which includes the following components, in percentage by mass: 0.4% drag reducing and tackifying agent, 0.4% nanoemulsion, 0.08% nonionic fluorocarbon surfactant, 0.03% fungicide, 0.3% viscosity regulator, 0.4% clay stabilizer, 0.1% gel breaker, 0.15% modifier, 0.3% gas generating agent, and the balance is water.

[0148] The drag reducing and thickening agent is a mixture of polyacrylamide with a viscosity average molecular weight of 12.1 million and a hydrolysis degree of 30% and non-hydrolyzed polyacrylamide with a viscosity average molecular weight of 1140, and the mass ratio of the two is 13:1.

[0149] The nanoemulsion has an average particle size of 150 nm. Based on the total mass of the nanoemulsion as 100%, it includes: 8% hydroxy fluorosilicone oil (Wuhan Rongcan Biotechnology Co., Ltd.), 7% vinyl fluorosilicone oil (Guangzhou Kangxi Organic Silicone Material Co., Ltd., KX-205), 8% Gemini fluorocarbon surfactant C2F5N + (CH3)2-CH2CH2CH2CH2-(CH3)2N +C2F5 (self-made: in parts by weight, at 30°C, 1.5 parts of pentafluorobromoethane were added to 7 parts of acetone, and the mixture was stirred at 150 rpm, followed by dropwise addition of 1 part of tetramethylbutanediamine. The mixture was added dropwise evenly over 12 minutes, and quaternization reaction was carried out under stirring at 150 rpm. After 1.5 hours of reaction, the precipitate was filtered and the obtained precipitate was the prepared gemini fluorocarbon surfactant), 18% nonionic fluorocarbon surfactant (3M Company, FC4432), 8% nano-silica with an average particle size of 40 nm, 6% ethanol and the balance water.

[0150] The nanoemulsion is prepared by the following steps: according to the content of each component in the above nanoemulsion, water is added to the reaction kettle, and the gemini fluorocarbon surfactant C2F5N is stirred at 35°C and 500rpm. + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C2F5 and a nonionic fluorocarbon surfactant were added to the reaction kettle and stirred for 15 minutes; propanol was then added and the stirring was continued for 20 minutes; nano-silica was then added and the stirring was continued for 20 minutes; hydroxyl fluorosilicone oil and vinyl fluorosilicone oil were added dropwise at a speed of 30 minutes and the stirring was continued for 35 minutes; finally, ultrasonic treatment was performed with a frequency of 30 kHz for 35 minutes to obtain the nanoemulsion.

[0151] The nonionic fluorocarbon surfactant is FC4432 from 3M Company.

[0152] The bactericide is dodecyldimethylbenzyl ammonium bromide.

[0153] The viscosity modifier is a complex formed by the complexation reaction of di(triethanolamine)diisopropyl titanate and glycerol. It is prepared by mixing di(triethanolamine)diisopropyl titanate, glycerol, and water in a weight ratio of 25:38:37, and reacting the mixture at 70°C for 2 hours to obtain the viscosity modifier.

[0154] The clay stabilizer is tetramethylammonium chloride.

[0155] The gel breaker is sodium persulfate.

[0156] The modifier is 3-aminopropyltriethoxysilane.

[0157] The gas generating agent is an effervescent tablet granule in which the acid source is citric acid, the alkali source is sodium bicarbonate, and the polyethylene glycol is used as a coating. The specific preparation steps are the same as those in Example 1.

[0158] The preparation method of the integrated fracturing fluid of this embodiment includes the following steps: slowly adding 0.4% of the drag reducing and viscosity increasing agent to water under stirring at 180 rpm, and stirring and mixing uniformly; then, sequentially adding 0.03% of the fungicide, 0.4% of the clay stabilizer, 0.15% of the modifier, 0.4% of the nanoemulsion, and 0.08% of the non-ionic fluorocarbon surfactant, and stirring and mixing uniformly; then, adding 0.3% of the viscosity modifier, and stirring and mixing uniformly; and finally, adding 0.3% of the gas generating agent and 0.1% of the gel breaker, and stirring uniformly to obtain the integrated fracturing fluid.

[0159] The fracturing fluids prepared in Example 4, Example 3, Comparative Examples 3-1, and Comparative Examples 3-2 are high-viscosity fracturing fluids. The main properties of the fracturing fluids were tested according to the industry standard NB / T 14003.3-2017, "Shale Gas Fracturing Fluids - Part 3: Performance Indicators and Evaluation Methods for Continuously Mixed Fracturing Fluids." Bacterial content was tested according to the industry standard NB / T 14003.1-2015, "Shale Gas Fracturing Fluids - Part 1: Slickwater Performance Indicators and Evaluation Methods." The test results for the main properties of the fracturing fluids are shown in Table 7. Suspended sand performance was tested according to the method described in Example 1, and the test results are shown in Table 8.

[0160] Table 7 Main properties of fracturing fluids of Example 4, Example 3, Comparative Example 3-1 and Comparative Example 3-2

[0161]

[0162] Table 8 Fracturing fluid sand suspension performance of Example 4, Example 3, Comparative Example 3-1, and Comparative Example 3-2

[0163]

[0164] It can be seen from Tables 7 and 8 above that the performance of the fracturing fluid of Example 4 is comparable to that of Example 3 in all aspects.

[0165] In summary, at the same viscosity, the fracturing fluid provided by the present invention has higher sand-suspending performance than conventional fracturing fluids, particularly low-viscosity slickwater fracturing fluids and medium-viscosity linear gel fracturing fluids. The fracturing fluid provided by the present invention has lower friction than conventional fracturing fluids, with the drag reduction rate increased by 2.1-11.2 percentage points, and the higher the viscosity, the greater the increase in drag reduction. Furthermore, the fracturing fluid provided by the present invention has better sand-suspending performance than conventional fracturing fluids of the same viscosity, particularly in the high-viscosity gel fracturing fluid provided, where the suspended sand did not settle within 10 minutes (compared to a conventional gel fracturing fluid of the same viscosity, where the suspended sand settled by 10% within 10 minutes).

Claims

1. An integrated fracturing fluid, comprising the following components, by mass percentage: 0.02%-0.5% of a drag reducing and tackifying agent, 0.1%-0.5% of a nanoemulsion, 0.02%-0.1% of a first nonionic fluorocarbon surfactant, 0.003%-0.05% of a fungicide, 0-0.5% of a viscosity modifier, 0-0.5% of a clay stabilizer, 0-0.1% of a gel breaker, 0.05%-0.2% of a silane modifier, 0.1%-1% of a gas generating agent, and the balance being water; The drag reducing and viscosity increasing agent is a mixture of hydrolyzed polyacrylamide and / or its derivatives and non-hydrolyzed polyacrylamide and / or its derivatives; The nanoemulsion is a nanoemulsion with an average particle size of ≤150 nm; based on the total mass of the nanoemulsion being 100%, it comprises the following components: 10%-20% of fluorine-containing silicone oil, 5%-10% of a Gemini fluorocarbon surfactant, 15%-25% of a second nonionic fluorocarbon surfactant, 5%-10% of nano-silicon dioxide, 1%-10% of a lower alcohol, and the balance being water; the general structural formula of the Gemini fluorocarbon surfactant is: C n F 2n+1 N + (CH3)2-CH2CH2CH2CH2-(CH3)2N + C n F 2n+1 , where n is 2-4.

2. The integrated fracturing fluid according to claim 1, wherein: When the integrated fracturing fluid contains a viscosity modifier, the content of the viscosity modifier is 0.1-0.5%, based on the total mass of the integrated fracturing fluid being 100%.

3. The integrated fracturing fluid according to claim 1, wherein: When the integrated fracturing fluid contains a breaker, the content of the breaker is 0.02-0.1%, based on the total mass of the integrated fracturing fluid being 100%.

4. The integrated fracturing fluid according to claim 1, wherein: When the integrated fracturing fluid contains a clay stabilizer, the content of the clay stabilizer is 0.01-0.5%, based on the total mass of the integrated fracturing fluid being 100%.

5. The integrated fracturing fluid according to claim 1, wherein: The mass ratio of the hydrolyzed polyacrylamide and / or its derivatives to the non-hydrolyzed polyacrylamide and / or its derivatives is (10-15):

1.

6. The integrated fracturing fluid according to claim 1, wherein: The viscosity average molecular weight of the hydrolyzed polyacrylamide and / or its derivatives is 5 million to 15 million, and the degree of hydrolysis is 20% to 30%; the viscosity average molecular weight of the non-hydrolyzed polyacrylamide and / or its derivatives is 5 million to 15 million.

7. The integrated fracturing fluid according to claim 1, wherein: The fluorine-containing silicone oil includes one or a combination of hydroxy fluorosilicone oil, vinyl fluorosilicone oil, methyl fluorosilicone oil and polyether fluorosilicone oil.

8. The integrated fracturing fluid according to claim 1, wherein: The second nonionic fluorocarbon surfactant includes one or a combination of polyoxyethylene ethers of fluorinated fatty alcohols, polyoxyethylene ethers of fluorinated phenols, polyoxyethylene ethers of fluorinated alkylsulfonyl alcoholamines, polyoxyethylene esters of fluorinated carboxylic acids, and polyoxyethylene ethers of fluorinated thiols.

9. The integrated fracturing fluid according to claim 1, wherein: The particle size of the nano-silicon dioxide is 15-50 nm.

10. The integrated fracturing fluid according to claim 1, wherein: The lower alcohol includes one or a combination of methanol, ethanol, propanol and butanol.

11. The integrated fracturing fluid according to claim 1, wherein: The nanoemulsion is prepared by the following steps: adding a gemini fluorocarbon surfactant and a second nonionic fluorocarbon surfactant to water according to the content of each component in the nanoemulsion at 10-40° C. and a stirring speed of 120-600 rpm, and then stirring for 10-30 minutes; then adding a lower alcohol and continuing to stir for 10-30 minutes; then adding nano-silicon dioxide and continuing to stir for 10-30 minutes; then dropwise adding fluorine-containing silicone oil and continuing to stir for 30-60 minutes; and finally performing ultrasonic treatment for 20-40 minutes to obtain the nanoemulsion.

12. The integrated fracturing fluid according to claim 1, wherein: The first nonionic fluorocarbon surfactant includes one or a combination of polyoxyethylene ethers of fluorinated fatty alcohols, polyoxyethylene ethers of fluorinated phenols, polyoxyethylene ethers of fluorinated alkylsulfonyl alcoholamines, polyoxyethylene esters of fluorinated carboxylic acids, and polyoxyethylene ethers of fluorinated thiols.

13. The integrated fracturing fluid according to claim 1, wherein: The bactericide includes one or a combination of aldehyde bactericides, quaternary ammonium salt bactericides and isothiazolinone bactericides.

14. The integrated fracturing fluid according to claim 13, wherein: The aldehyde fungicide includes one or a combination of glutaraldehyde, formaldehyde and acrolein.

15. The integrated fracturing fluid according to claim 13, wherein: The quaternary ammonium salt fungicide includes one or a combination of tetradecyldimethylbenzyl ammonium chloride, dodecyltrimethylammonium chloride, dodecyldimethylbenzyl ammonium chloride and dodecyldimethylbenzyl ammonium bromide.

16. The integrated fracturing fluid according to claim 13, wherein: The isothiazolinone fungicide includes methylisothiazolinone and / or methylchloroisothiazolinone.

17. The integrated fracturing fluid according to claim 1, wherein: The viscosity modifier includes one or a combination of water-soluble zirconium salt, water-soluble titanium salt, water-soluble chromium salt and water-soluble aluminum salt; Alternatively, the viscosity modifier includes one or a combination of water-soluble organic zirconium salt, water-soluble organic titanium salt, water-soluble organic chromium salt and water-soluble organic aluminum salt obtained by complexing water-soluble zirconium salt, water-soluble titanium salt, water-soluble chromium salt and water-soluble organic aluminum salt with polyhydroxy alcohol respectively.

18. The integrated fracturing fluid according to claim 17, wherein: The water-soluble organic zirconium salt includes a complex obtained by a complex reaction between zirconium oxychloride and one or more of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal and triethylene glycol.

19. The integrated fracturing fluid according to claim 17, wherein: The water-soluble titanium salt includes diisopropyl di(triethanolamine)titanate and / or diisopropyl orthotitanate dilactate; the water-soluble organic titanium salt includes a complex obtained by the complexation reaction of diisopropyl di(triethanolamine)titanate and / or diisopropyl orthotitanate dilactate with one or more of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal and triethylene glycol.

20. The integrated fracturing fluid according to claim 17, wherein: The water-soluble organic chromium salt includes a complex obtained by a complex reaction between one or more combinations of chromium lactate, chromium acetate, chromium chloride and chromium sulfate and one or more combinations of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal and triethylene glycol.

21. The integrated fracturing fluid according to claim 17, wherein: The water-soluble organic aluminum salt includes a complex obtained by a complex reaction of one or more combinations of potassium aluminum sulfate dodecahydrate, aluminum sulfate, aluminum lactate, aluminum acetate and aluminum chloride with one or more combinations of sorbitol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, diethylene glycol acetal and triethylene glycol.

22. The integrated fracturing fluid according to claim 1, wherein: The clay stabilizer includes one or a combination of tetramethylammonium chloride, potassium chloride and polyquaternium salt.

23. The integrated fracturing fluid according to claim 1, wherein: The gel breaker includes one or a combination of ammonium persulfate, sodium persulfate and potassium persulfate.

24. The integrated fracturing fluid according to claim 1, wherein: The silane modifier includes one or a combination of N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane and N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

25. The integrated fracturing fluid according to claim 1, wherein: The gas generating agent includes effervescent tablet particles.

26. The integrated fracturing fluid according to claim 25, wherein: The effervescent tablet granules are effervescent tablet granules whose acid source is citric acid, whose alkali source is sodium bicarbonate, and whose capsule is wrapped with polyethylene glycol.

27. A method for preparing the integrated fracturing fluid according to any one of claims 1 to 26, comprising the following steps: When preparing indoors: S1. Under stirring conditions of 60-200 rpm, based on the total mass of the integrated fracturing fluid as 100%, 0.02%-0.5% of a drag reducing and tackifying agent is added to water and stirred to mix uniformly; S2, then adding 0.003%-0.05% of a fungicide, 0-0.5% of a clay stabilizer, 0.05%-0.2% of a modifier, 0.1%-0.5% of a nanoemulsion, and 0.02%-0.1% of a first nonionic fluorocarbon surfactant, stirring and mixing uniformly to obtain a first mixed solution; S3. Add 0-0.5% of a viscosity modifier to the first mixed solution according to the viscosity requirement of the desired fracturing fluid, and stir and mix uniformly to obtain a second mixed solution; S4. Add 0.1%-1% of a gas generating agent and 0-0.1% of a gel breaker to the second mixed liquid, and stir evenly to obtain the integrated fracturing fluid; When preparing on-site: The preparation steps of S1-S3 are the same as those for indoor preparation. The preparation steps of S4 are as follows: 0.1%-1% of gas generating agent and 0-0.1% of gel breaker are added into the mixing tank of the sand mixing truck, and mixed evenly with the second mixed liquid and sand in the mixing tank of the sand mixing truck.

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