Long-acting anti-scaling fracturing fluid and preparation method thereof

Abstract

The long-acting anti-scaling fracturing fluid is prepared from the following components in percentage by mass: 0.2 to 0.5 percent of a thickening agent, 0.02 to 0.1 percent of a multifunctional auxiliary agent, 0.02 to 0.05 percent of an anti-scaling agent, 0.01 to 0.05 percent of a gel breaker and the balance of water. The preparation method of the long-acting anti-scaling fracturing fluid comprises the following steps: weighing the components, sequentially adding the thickening agent and the water, uniformly stirring, adding the multifunctional additive, uniformly stirring, respectively adding the anti-scaling agent and the gel breaker, and uniformly stirring to obtain the long-acting anti-scaling fracturing fluid. According to the long-acting anti-scaling fracturing fluid and the preparation method thereof, the phenomena of oil pipe blockage, pump blockage and the like caused by scaling in the production process after oil and gas well fracturing transformation can be eliminated or retarded, the production time efficiency of an oil well is guaranteed, and cost reduction and efficiency improvement are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of fracturing fluid for oil and gas well fracturing construction, relates to a long-acting anti-scaling fracturing fluid, and also relates to a preparation method of the long-acting anti-scaling fracturing fluid. Background Art

[0002] Shale oil and gas horizontal wells are developed and put into production by hydraulic fracturing. Complex fracture networks are created by large displacement, and large amounts of liquid are used to supplement formation energy to improve oil recovery efficiency. Serious scaling problems occur in the post-fracturing production process, causing frequent blockages in the oil pipes and pump jams, affecting the normal operation of oil production equipment, reducing production efficiency, and increasing production costs. In response to the serious scaling problem in oil fields, the main method of alleviating scaling is to add chemical anti-scaling agents during the production process. The disadvantage of this method is that it has a short action time and only works in the wellbore, requiring long-term continuous injection, low anti-scaling efficiency, and incomplete anti-scaling. Summary of the invention

[0003] The purpose of the present invention is to provide a long-term anti-scaling fracturing fluid, which has the characteristics of long-term anti-scaling, cost reduction and efficiency improvement.

[0004] Another object of the present invention is to provide a method for preparing a long-lasting anti-scaling fracturing fluid.

[0005] The technical solution adopted by the present invention is that the long-term anti-scaling fracturing fluid is composed of the following components in terms of mass percentage: 0.2% to 0.5% thickener, 0.02% to 0.1% multifunctional additive, 0.02% to 0.05% anti-scaling agent, 0.01% to 0.05% breaker, and the balance is water.

[0006] The present invention is also characterized in that:

[0007] The thickener is any one of partially hydrolyzed polyacrylamide, poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid) or acrylamide-N,N-dimethylallylnonylammonium bromide copolymer.

[0008] Calculated by the mass percentage of the multifunctional additive, the multifunctional additive is a mixture of 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactant, 25% to 40% of quaternary ammonium salt surfactant and 5% to 20% of water.

[0009] The fluorocarbon surfactant is any one of polyethylene glycol perfluoroalkyl ester, 3-tri-epoxyhexafluoropropaneamidopropyl (2-sulfite)ethyl dimethylammonium, N-[3-(dimethylamino)-propyl]-perfluorosulfonamide or N-(2-perfluorooctylsulfonamideethyl)-β,β'-iminodipropionic acid disodium amino acid;

[0010] The quaternary ammonium salt surfactant is any one of 3-(triethoxysilyl)propyldimethyloctadecylammonium chloride, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide or propylene oxidetrimethylammonium chloride.

[0011] The scale inhibitor is a ternary copolymer composed of methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid and sodium hypophosphite, wherein methacryloyloxyethyl trimethyl ammonium chloride is a main chain monomer, acrylic acid is a side chain monomer, sodium hypophosphite is a detection monomer, the mass ratio of methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid and sodium hypophosphite is 1: (0.25-0.35): (0.08-0.25), and the molecular weight of the ternary copolymer is 2000 g / mol-20000 g / mol.

[0012] The gel breaker is any one of sodium persulfate, ammonium persulfate, low-temperature β-mannanase or Beilex 160.

[0013] Another technical solution adopted by the present invention is a method for preparing a long-acting anti-scaling fracturing fluid, which is specifically implemented according to the following steps:

[0014] Step 1, weigh the following components respectively according to mass percentage: thickener 0.2%-0.5%, multifunctional additive 0.02%-0.1%, anti-scaling agent 0.02%-0.05%, debonding agent 0.01%-0.05%, and the balance is water;

[0015] Step 2, add the weighed thickener and water into a glass container in sequence, stir evenly, and obtain a main agent;

[0016] Step 3, adding the weighed multifunctional auxiliary agent to the main agent solution obtained in step 2, and stirring evenly to obtain the base solution;

[0017] Step 4: Add the weighed anti-scaling agent and gel breaker into the base fluid of step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

[0018] Another technical solution of the present invention is also characterized in that:

[0019] In step 1, the preparation method of the multifunctional additive is: adding 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactant, 25% to 40% of quaternary ammonium salt surfactant, and 5% to 20% of water into a glass container, and stirring evenly at room temperature.

[0020] In step 1, the preparation method of the anti-scaling agent is: methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid, and sodium hypophosphite are weighed in a mass ratio of 1: (0.25-0.35): (0.08-0.25), and added into a reactor for ternary copolymerization.

[0021] The temperature in the reactor is 60°C to 90°C and the reaction time is 2h to 5h.

[0022] The beneficial effects of the present invention are:

[0023] 1) For unconventional oil and gas reservoirs such as shale oil and gas, tight oil and gas, which have production scaling problems after fracturing transformation, it can eliminate or slow down the occurrence of oil pipe blockage, pump jamming and other phenomena caused by scaling during the production process of oil and gas wells after fracturing transformation, ensure the production timeliness of oil wells, and achieve cost reduction and efficiency improvement.

[0024] 2) By adding a long-term anti-scaling agent with anti-scaling properties to the fracturing fluid, the long-term anti-scaling fracturing fluid is injected into the formation through fracturing construction, and the capillary force of the dense reservoir is used to enter the deep reservoir, so that it stays in the formation for a long time, thereby promoting oil-water replacement, playing a long-term anti-scaling role, reducing formation blockage damage, and thus achieving the purpose of increasing production;

[0025] 3) It achieves multiple functions such as anti-scaling and seam creation, without the need for special filling processes, thus reducing the cost of later filling;

[0026] 4) The raw materials are easily available, the preparation process is simple, the preparation process is safe, the anti-scaling efficiency is high, and the anti-scaling effect lasts for a long time. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0028] The long-acting anti-scaling fracturing fluid of the present invention is composed of the following components in terms of mass percentage: 0.2% to 0.5% of a thickener, 0.02% to 0.1% of a multifunctional auxiliary agent, 0.02% to 0.05% of an anti-scaling agent, 0.01% to 0.05% of a gel breaker, and the remainder is water.

[0029] The thickener is any one of partially hydrolyzed polyacrylamide, poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid) or acrylamide-N,N-dimethylallylnonylammonium bromide copolymer.

[0030] Calculated by the mass percentage of the multifunctional additive, the multifunctional additive is a mixture of 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactant, 25% to 40% of quaternary ammonium salt surfactant and 5% to 20% of water.

[0031] The fluorocarbon surfactant is any one of polyethylene glycol perfluoroalkyl ester, 3-tri-epoxyhexafluoropropaneamidopropyl (2-sulfite)ethyl dimethylammonium, N-[3-(dimethylamino)-propyl]-perfluorosulfonamide or N-(2-perfluorooctylsulfonamideethyl)-β,β'-iminodipropionic acid disodium amino acid;

[0032] The quaternary ammonium salt surfactant is any one of 3-(triethoxysilyl)propyldimethyloctadecylammonium chloride, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide or propylene oxidetrimethylammonium chloride.

[0033] The anti-scaling agent is a carboxylic acid copolymer. The carboxylic acid copolymer is composed of methacryloyloxyethyl trimethyl ammonium chloride as a main chain monomer, acrylic acid as a side chain monomer, and sodium hypophosphite as a detection monomer. The copolymer is ternary copolymerized in a mass ratio of 1: (0.25-0.35): (0.08-0.25). Ammonium persulfate is used as an initiator in an amount of 2%-8% of the total mass of the three monomers. The pH of the polymerization reaction system is adjusted to be approximately neutral with a sodium hydroxide solution. The copolymer is obtained by free radical polymerization in an aqueous solution. The molecular weight range of the obtained carboxylic acid copolymer is 2000g / mol-20000g / mol.

[0034] The gel breaker is any one of sodium persulfate, ammonium persulfate, low-temperature β-mannanase or Beilex 160.

[0035] The advantages of the long-term anti-scaling fracturing fluid of the present invention are as follows: a polymer anti-scaling agent compatible with the main agent and auxiliary agent of the fracturing fluid is added to the fracturing fluid to obtain a long-term anti-scaling fracturing fluid, which is injected into the reservoir transformation volume during fracturing, and the retained formation fracturing fluid is used to prevent scale and reduce formation blockage. After the well is opened and production is resumed, when water in the formation enters the wellbore, the anti-scaling agent also enters the production wellbore to ensure long-term flow, prevent scale on the formation, wellbore and ground as a whole, achieve the purpose of long-term anti-scaling, realize multiple functions such as anti-scaling and seam creation, do not require special process for injection, and reduce the cost of later injection.

[0036] The preparation method of the long-acting anti-scaling fracturing fluid is specifically implemented according to the following steps:

[0037] Step 1, weigh the following components respectively according to mass percentage: thickener 0.2%-0.5%, multifunctional additive 0.02%-0.1%, anti-scaling agent 0.02%-0.05%, debonding agent 0.01%-0.05%, and the balance is water;

[0038] The preparation method of the multifunctional additive is as follows: 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactants, 25% to 40% of quaternary ammonium salt surfactants, and 5% to 20% of water are added into a glass container and stirred evenly at room temperature.

[0039] The preparation method of the anti-scaling agent is as follows: methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid and sodium hypophosphite are weighed in a mass ratio of 1: (0.25-0.35): (0.08-0.25), and added into a reactor for ternary copolymerization. The temperature in the reactor is 60°C-90°C and the reaction time is 2h-5h.

[0040] Step 2, add the weighed thickener and water into a glass container in sequence, stir to make them evenly dispersed, and obtain a main agent;

[0041] Step 3, adding the weighed multifunctional auxiliary agent to the main agent solution obtained in step 2, stirring to make it evenly dispersed to obtain the base solution;

[0042] Step 4: Before use, add the weighed anti-scaling agent and gel breaker into the base fluid of step 3 respectively, and stir evenly to obtain a long-lasting anti-scaling fracturing fluid.

[0043] The preparation method of the long-acting anti-scaling fracturing fluid of the present invention has the advantages of easily available raw materials, simple preparation process, safe preparation technology, high anti-scaling efficiency and long anti-scaling action time.

[0044] Embodiment 1:

[0045] The long-acting anti-scaling fracturing fluid of the present invention is composed of the following components in terms of mass percentage:

[0046] Thickener partially hydrolyzed polyacrylamide: 0.2%, multifunctional auxiliary agent: 0.02%; the multifunctional auxiliary agent is composed of 15% silicon dioxide nanoparticles, 40% fluorocarbon surfactant polyethylene glycol perfluoroalkyl ester, 40% quaternary ammonium salt surfactant 3-(triethoxysilyl)propyl dimethyl octadecyl ammonium chloride, and 5% water;

[0047] Anti-scaling agent: methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite terpolymer, molecular weight 20000 g / mol: 0.02%;

[0048] Degumming agent ammonium persulfate: 0.01%;

[0049] The balance is water.

[0050] The preparation method of the long-acting anti-scaling fracturing fluid comprises the following specific steps:

[0051] Step 1. Weigh the following components according to mass percentage: 0.2% partially hydrolyzed polyacrylamide, 0.02% multifunctional additive, 0.02% anti-scaling agent, 0.01% degumming agent ammonium persulfate, and the balance is water.

[0052] Among them, the preparation method of the multifunctional auxiliary agent is: add 15g of silica nanoparticles, 40g of fluorocarbon surfactant polyethylene glycol perfluoroalkyl ester, 40g of quaternary ammonium surfactant 3-(triethoxysilyl)propyl dimethyl octadecyl ammonium chloride into a 200mL beaker, add 5g of water, and stir evenly at room temperature.

[0053] The preparation method of the anti-scaling agent is as follows: 13 g of methacryloyloxyethyl trimethyl ammonium chloride, 4.5 g of acrylic acid, and 1.1 g of sodium hypophosphite are added into a reactor, the temperature in the reactor is set to 60° C., and the reaction time is 5 h, to synthesize the anti-scaling agent, and the molecular weight of the terpolymer of methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite is 20,000 g / mol.

[0054] Step 2. Add the weighed partially hydrolyzed polyacrylamide and water into a 2L beaker and stir thoroughly to make it evenly dispersed to obtain the main agent.

[0055] Step 3. Add the weighed multifunctional auxiliary agent into the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0056] Step 4. Before use, add the weighed anti-scaling agent and gel breaker ammonium persulfate to the base fluid obtained in step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

[0057] Example 2

[0058] The long-acting anti-scaling fracturing fluid of the present invention is composed of the following components in terms of mass percentage: 0.5% of a thickener poly(2-acrylamide-2-methylpropanesulfonic acid), 0.1% of a multifunctional auxiliary agent, 0.05% of an anti-scaling agent with a molecular weight of 2000 g / mol, 0.05% of a breaker sodium persulfate, and the balance is water.

[0059] The multifunctional additive is composed of 20% of silicon dioxide nanoparticles, 35% of fluorocarbon surfactant 3-tri-epoxyhexafluoropropane amide propyl (2-sulfite) ethyl dimethyl ammonium, 35% of quaternary ammonium surfactant hexadecyl trimethyl ammonium chloride, and 10% of water;

[0060] Anti-scaling agent: methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite terpolymer, molecular weight 2000g / mol:

[0061] The method for preparing the long-acting anti-scaling fracturing fluid of the present invention comprises the following steps:

[0062] Step 1. Weigh the following components according to mass percentage: 0.5% thickener poly (2-acrylamide-2-methylpropane sulfonic acid), 0.1% multifunctional additive, 0.05% anti-scaling agent with a molecular weight of 2000 g / mol, 0.05% degumming agent sodium persulfate, and the balance is water.

[0063] Among them, the preparation method of the multifunctional additive is: add 20g of silica nanoparticles, 35g of fluorocarbon surfactant 3-triepoxyhexafluoropropaneamide propyl (2-sulfite) ethyl dimethyl ammonium, 35g of quaternary ammonium surfactant hexadecyltrimethylammonium chloride in a 200mL beaker, add 10g of water, and stir evenly to obtain the multifunctional additive.

[0064] The preparation method of the anti-scaling agent is as follows: 15.6 g of methacryloyloxyethyl trimethyl ammonium chloride, 3.2 g of acrylic acid, and 3.3 g of sodium hypophosphite are added into a reactor. The temperature in the reactor is set at 80° C. and the reaction time is 3 h, and a terpolymer of methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite is synthesized to obtain an anti-scaling agent, and the molecular weight is 2000 g / mol.

[0065] Step 2. Add the weighed poly(2-acrylamide-2-methylpropanesulfonic acid) and water into a 2L beaker and stir thoroughly to make them evenly dispersed to obtain the main agent.

[0066] Step 3. Add the weighed multifunctional auxiliary agent into the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0067] Step 4. Before use, add the anti-scaling agent and the gel breaker sodium persulfate to the base fluid obtained in step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

[0068] Example 3

[0069] The long-acting anti-scaling fracturing fluid of the present invention is composed of the following components in terms of mass percentage: 0.3% of a thickener poly(2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid), 0.04% of a multifunctional auxiliary agent, 0.03% of an anti-scaling agent with a molecular weight of 8000 g / mol, 0.02% of a gel breaker low-temperature β-mannanase, and the balance is water.

[0070] The multifunctional additive is composed of 25% of silicon dioxide nanoparticles, 30% of fluorocarbon surfactant N-[3-(dimethylamino)-propyl]-perfluorosulfonamide, 30% of quaternary ammonium surfactant dodecyltrimethylammonium bromide, and 15% of water;

[0071] The method for preparing the long-acting anti-scaling fracturing fluid of the present invention comprises the following steps:

[0072] Step 1. Weigh the following components according to mass percentage: 0.3% thickener poly (2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid), 0.04% multifunctional additive, 0.03% anti-scaling agent with a molecular weight of 8000 g / mol, 0.02% gel breaker low-temperature β-mannanase, and the balance is water.

[0073] Among them, the preparation method of the multifunctional additive is: add 25g of silica nanoparticles, 30g of fluorocarbon surfactant N-[3-(dimethylamino)-propyl]-perfluorosulfonamide, 30g of quaternary ammonium surfactant dodecyltrimethylammonium bromide into a 200mL beaker, add 15g of water, and stir evenly to obtain the multifunctional additive.

[0074] The preparation method of the anti-scaling agent is as follows: 13.8 g of methacryloyloxyethyl trimethyl ammonium chloride, 4.2 g of acrylic acid, and 2.2 g of sodium hypophosphite are added into a reactor. The temperature in the reactor is set at 70° C. and the reaction time is 4 h, and a terpolymer of methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite is synthesized to obtain an anti-scaling agent, and the molecular weight is 8000 g / mol.

[0075] Step 3. Add the weighed poly(2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid) and water into a 2L beaker, stir well to make them evenly dispersed, and obtain the main agent.

[0076] Step 3. Add the weighed multifunctional auxiliary agent into the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0077] Step 4. Before construction and use, add the anti-scaling agent and the gel breaker low-temperature β-mannanase to the base fluid obtained in step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

[0078] Example 4

[0079] The long-acting anti-scaling fracturing fluid of the present invention is composed of the following components by weight percentage:

[0080] Thickener acrylamide-N,N-dimethylallylnonylammonium bromide copolymer: 0.4%;

[0081] Multifunctional additive: 0.06%, composed of 30% silica nanoparticles, 25% fluorocarbon surfactant N-(2-perfluorooctanesulfonamideethyl)-β,β'-iminodipropionic acid disodium amino acid, 25% quaternary ammonium surfactant propylene oxide trimethylammonium chloride, and 20% water;

[0082] Anti-scaling agent: methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite terpolymer (molecular weight 5000 g / mol): 0.04%;

[0083] Gel breaker Bailishi 160: 0.03%;

[0084] The balance is water.

[0085] The method for preparing the long-acting anti-scaling fracturing fluid of the present invention comprises the following steps:

[0086] Step 1. Weigh the following components according to mass percentage: thickener acrylamide-N,N-dimethylallylnonylammonium bromide copolymer: 0.4%;

[0087] Multifunctional additive: 0.06%,

[0088] Anti-scaling agent: methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite terpolymer (molecular weight 5000 g / mol): 0.04%;

[0089] Gel breaker Bailishi 160: 0.03%;

[0090] The balance is water.

[0091] Among them, the preparation method of the multifunctional additive is: add 30g of silica nanoparticles, 25g of fluorocarbon surfactant N-(2-perfluorooctanesulfonamideethyl)-β,β'-iminodipropionic acid disodium amino acid, 25g of quaternary ammonium surfactant propylene oxide trimethylammonium chloride into a 200mL beaker, add 20g of water, and stir evenly to obtain the multifunctional additive.

[0092] The preparation method of the anti-scaling agent is as follows: 14.7 g of methacryloyloxyethyl trimethyl ammonium chloride, 3.6 g of acrylic acid, and 2.8 g of sodium hypophosphite are added into a reactor. The temperature in the reactor is set at 90° C. and the reaction time is 2 h, and a terpolymer of methacryloyloxyethyl trimethyl ammonium chloride-acrylic acid-sodium hypophosphite (molecular weight 5000 g / mol) of the anti-scaling agent is synthesized.

[0093] Step 2. Add the weighed acrylamide-N,N-dimethylallylnonylammonium bromide copolymer and water into a 2L beaker, stir thoroughly to make it evenly dispersed, and obtain the main agent.

[0094] Step 3. Add the multifunctional auxiliary agent to the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0095] Step 4. Before construction and use, add the anti-scaling agent and the gel breaker Beilex 160 to the base fluid obtained in step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

[0096] Comparative Example 5

[0097] Comparative Example 5 is a fracturing fluid without any anti-scaling agent. This comparative example is composed of the following components by mass percentage:

[0098] Thickener poly (2-acrylamide-2-methylpropanesulfonic acid): 0.5%;

[0099] Multifunctional additive: 0.1%, composed of 20% silica nanoparticles, 35% fluorocarbon surfactant 3-tri-epoxyhexafluoropropaneamide propyl (2-sulfite) ethyl dimethyl ammonium, 35% quaternary ammonium surfactant hexadecyl trimethyl ammonium chloride, and 10% water;

[0100] Degumming agent sodium persulfate: 0.05%;

[0101] The balance is water.

[0102] The specific preparation process of fracturing fluid is as follows:

[0103] Step 1. Weigh each component according to the above mass percentage;

[0104] Among them, the preparation method of the multifunctional auxiliary agent is: add 20g of silica nanoparticles, 35g of fluorocarbon surfactant 3-triepoxyhexafluoropropaneamide propyl (2-sulfite) ethyl dimethyl ammonium, 35g of quaternary ammonium surfactant hexadecyltrimethylammonium chloride into a 200mL beaker, add 10g of water, and stir evenly to obtain the multifunctional auxiliary agent of the present invention.

[0105] Step 2. Add 5.0 g of poly(2-acrylamide-2-methylpropanesulfonic acid) and 993.0 g of water into a 2 L beaker, and stir thoroughly to make it evenly dispersed to obtain a main agent.

[0106] Step 3. Add 1.0 g of the multifunctional auxiliary agent to the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0107] Step 4. Before use in construction, add 0.5 g of a gel breaker, sodium persulfate, to the base fluid obtained in step 3, and stir evenly to obtain a control fracturing fluid system.

[0108] Comparative Example 6

[0109] Comparative Example 6 is set up, and the commercially available anti-scaling agent aminotrimethylenephosphonic acid is added to the fracturing fluid system. This comparative example is composed of the following components by mass percentage:

[0110] Thickener poly (2-acrylamide-2-methylpropanesulfonic acid): 0.5%;

[0111] Multifunctional additive: 0.1%, composed of 20% silica nanoparticles, 35% fluorocarbon surfactant 3-tri-epoxyhexafluoropropaneamide propyl (2-sulfite) ethyl dimethyl ammonium, 35% quaternary ammonium surfactant hexadecyl trimethyl ammonium chloride, and 10% water;

[0112] Commercially available antiscalant aminotrimethylenephosphonic acid: 0.05%;

[0113] Degumming agent sodium persulfate: 0.05%;

[0114] The balance is water.

[0115] The specific preparation process of the comparative example fracturing fluid is as follows:

[0116] Step 1. Weigh each component according to the above mass percentage;

[0117] Among them, the preparation method of the multifunctional additive is: add 20g of silica nanoparticles, 35g of fluorocarbon surfactant 3-triepoxyhexafluoropropaneamide propyl (2-sulfite) ethyl dimethyl ammonium, 35g of quaternary ammonium surfactant hexadecyltrimethylammonium chloride in a 200mL beaker, add 10g of water, and stir evenly to obtain the multifunctional additive.

[0118] Step 2. Add 5.0 g of poly(2-acrylamide-2-methylpropanesulfonic acid) and 993.0 g of water into a 2 L beaker, and stir thoroughly to make it evenly dispersed to obtain a main agent.

[0119] Step 3. Add 1.0 g of the multifunctional auxiliary agent to the main agent solution obtained in step 2, and stir to fully dissolve it to obtain the base solution.

[0120] Step 4. Before use, add 0.5 g of scale inhibitor aminotrimethylenephosphonic acid and 0.5 g of gel breaker sodium persulfate to the base fluid obtained in step 3, and stir evenly to obtain a control fracturing fluid system.

[0121] The long-term anti-scaling fracturing fluid of the present invention: the amount of the long-term anti-scaling agent added is 0.02% to 0.05% of the fracturing fluid, wherein the long-term anti-scaling agent is fully stirred after being added to the fracturing fluid to make it evenly mixed, and during the fracturing construction, 20% to 30% of the total liquid volume of the fracturing fluid containing the long-term anti-scaling agent is pumped, and the well is shut down for 10 to 15 days after the construction is completed. The above percentages are weight percentages. The long-term anti-scaling fracturing fluids prepared in the above Examples 1, 2, 3 and 4 and conventional fracturing fluid systems are used in oil well reservoir reconstruction, and a comparative test of permeability after core displacement is carried out indoors, and the comparative data are shown in Table 1.

[0122] Table 1 Anti-scaling and damage performance of Examples 1 to 6

[0123] Reagents Permeability recovery rate <![CDATA[Scale inhibition rate of CaCO3]]> <![CDATA[Scale inhibition rate of CaSO4]]> <![CDATA[BaSO4 scale inhibition rate]]> Anti-scaling time Example 1 52.68％ 92.40％ 91.50％ 92.50％ 6 months Example 2 51.20％ 94.20％ 92.70％ 91.40％ 6 months Example 3 49.15％ 94.30％ 91.60％ 93.70％ 6 months Example 4 48.85％ 94.10％ 90.30％ 92.80％ 6 months Comparative Example 5 50.72％ — — — 1 month Comparative Example 6 51.94％ 50.40％ 49.10％ 40％ 1 month

[0124] As can be seen from Table 1, the permeability recovery rate of the long-acting anti-scaling fracturing fluid of the present invention after core displacement is comparable to that of the conventional commercial anti-scaling agent fracturing fluid system and the fracturing fluid system without adding anti-scaling agent, proving that the long-acting anti-scaling agent added in the present invention has no effect on reservoir damage;

[0125] As can be seen from Table 1, the anti-scaling efficiency of the long-acting anti-scaling fracturing fluid of the present invention is greater than 90%, and the anti-scaling time is 6 months, which is relatively long. The anti-scaling time of the fracturing fluid system prepared with conventional commercial anti-scaling agents and the fracturing fluid system without adding anti-scaling agents is about 1 month. Therefore, the anti-scaling performance of the long-acting anti-scaling fracturing fluid of the present invention is significantly better than that of the existing conventional commercial anti-scaling agent fracturing fluid system.

Claims

1. Long-term anti-scaling fracturing fluid, characterized in that: The invention is composed of the following components in percentage by mass: 0.2% to 0.5% of thickener, 0.02% to 0.1% of multifunctional auxiliary agent, 0.02% to 0.05% of anti-scaling agent, 0.01% to 0.05% of degumming agent, and the balance is water.

2. The long-acting anti-scaling fracturing fluid according to claim 1, characterized in that: The thickener is any one of partially hydrolyzed polyacrylamide, poly(2-acrylamide-2-methylpropanesulfonic acid), poly(2-acrylamide-2-methylpropanesulfonic acid-co-acrylic acid) or acrylamide-N,N-dimethylallylnonylammonium bromide copolymer.

3. The long-acting anti-scaling fracturing fluid according to claim 1, characterized in that: Calculated by the mass percentage of the multifunctional additive, the multifunctional additive is a mixture of 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactant, 25% to 40% of quaternary ammonium salt surfactant and 5% to 20% of water.

4. The long-acting anti-scaling fracturing fluid according to claim 3, characterized in that: The fluorocarbon surfactant is any one of polyethylene glycol perfluoroalkyl ester, 3-tri-epoxyhexafluoropropaneamidopropyl (2-sulfite) ethyl dimethyl ammonium, N-[3-(dimethylamino)-propyl]-perfluorosulfonamide or N-(2-perfluorooctylsulfonamideethyl)-β,β'-iminodipropionic acid disodium amino acid; The quaternary ammonium salt surfactant is any one of 3-(triethoxysilyl)propyldimethyloctadecylammonium chloride, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide or propylene oxidetrimethylammonium chloride.

5. The long-acting anti-scaling fracturing fluid according to claim 1, characterized in that: The anti-scaling agent is a ternary copolymer composed of methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid, and sodium hypophosphite, wherein methacryloyloxyethyl trimethyl ammonium chloride is a main chain monomer, acrylic acid is a side chain monomer, and sodium hypophosphite is a detection monomer. The mass ratio of methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid, and sodium hypophosphite is 1: (0.25-0.35): (0.08-0.25), and the molecular weight of the ternary copolymer is 2000 g / mol-20000 g / mol.

6. The long-acting anti-scaling fracturing fluid according to claim 1, characterized in that: The gel breaker is any one of sodium persulfate, ammonium persulfate, low-temperature β-mannanase or Beilex 160.

7. A method for preparing a long-lasting anti-scaling fracturing fluid, characterized in that: Please follow the steps below to implement: Step 1, weigh the following components respectively according to mass percentage: thickener 0.2%-0.5%, multifunctional additive 0.02%-0.1%, anti-scaling agent 0.02%-0.05%, debonding agent 0.01%-0.05%, and the balance is water; Step 2, add the weighed thickener and water into a glass container in sequence, stir evenly, and obtain a main agent; Step 3, adding the weighed multifunctional auxiliary agent to the main agent solution obtained in step 2, and stirring evenly to obtain the base solution; Step 4: Add the weighed anti-scaling agent and gel breaker into the base fluid of step 3 respectively, and stir evenly to obtain a long-term anti-scaling fracturing fluid.

8. The method for preparing the long-acting anti-scaling fracturing fluid according to claim 7, characterized in that: In step 1, the preparation method of the multifunctional auxiliary agent is: adding 15% to 30% of silicon dioxide nanoparticles, 25% to 40% of fluorocarbon surfactants, 25% to 40% of quaternary ammonium salt surfactants, and 5% to 20% of water into a glass container, and stirring evenly at room temperature.

9. The method for preparing the long-acting anti-scaling fracturing fluid according to claim 7, characterized in that: In step 1, the preparation method of the anti-scaling agent is: methacryloyloxyethyl trimethyl ammonium chloride, acrylic acid, and sodium hypophosphite are weighed in a mass ratio of 1: (0.25-0.35): (0.08-0.25), and added into a reaction kettle for ternary copolymerization.

10. The method for preparing the long-acting anti-scaling fracturing fluid according to claim 9, characterized in that: The temperature in the reactor is 60° C. to 90° C., and the reaction time is 2 h to 5 h.