阅读说明：本技术 一种压裂用乳液聚合物及其制备方法和应用 (Emulsion polymer for fracturing and preparation method and application thereof ) 是由 苏智青 李应成 沙鸥 夏燕敏 许汇 孙慧 朱益兴 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种压裂用乳液聚合物及其制备方法和应用。该压裂用乳液聚合物含有丙烯酰胺单体结构单元、阴离子单体结构单元、非离子单体结构单元、表面活性单体结构单元,以及任选的阳离子单体结构单元,其中,所述表面活性单体结构单元选自式(I)、式(II)、式(III)和式(IV)所示的中的一种或多种。本发明的压裂用乳液聚合物在高盐条件下具有较高的增粘能力,在低浓度条件下具有较好的减阻效率,能够简化现有压裂施工工艺,实现稠化剂和减阻剂的一剂多效的效果,而且在盐水中能快速分散并溶解,满足了压裂施工中对耐盐和速溶的要求。(The invention discloses an emulsion polymer for fracturing and a preparation method and application thereof. The emulsion polymer for fracturing contains an acrylamide monomer structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, a surface active monomer structural unit and an optional cationic monomer structural unit, wherein the surface active monomer structural unit is selected from one or more of the structural units shown in formula (I), formula (II), formula (III) and formula (IV). The emulsion polymer for fracturing has higher tackifying capability under the condition of high salt and better drag reduction efficiency under the condition of low concentration, can simplify the existing fracturing construction process, realizes the multi-effect of one thickening agent and drag reduction agent, can be quickly dispersed and dissolved in saline water, and meets the requirements of salt tolerance and instant dissolution in fracturing construction.)

1. An emulsion polymer for fracturing, which contains an acrylamide monomer structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, a surface active monomer structural unit and an optional cationic monomer structural unit, wherein the surface active monomer structural unit is selected from one or more of structural units shown in a formula (I), a formula (II), a formula (III) and a formula (IV),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

2. The emulsion polymer for fracturing of claim 1, wherein each R is₁Each independently selected from hydrogen atom, C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); each R₂、R₃And R₄Each independently selected from C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); a. b is independently 3-14.

3. The emulsion polymer for fracturing as claimed in claim 1 or 2, wherein the content of the acrylamide monomer structural unit is 25 to 75 parts by weight, the content of the anionic monomer structural unit is 0.1 to 25 parts by weight, the content of the nonionic monomer structural unit is 0.1 to 15 parts by weight, the content of the surface active monomer structural unit is 0.001 to 5 parts by weight, and the content of the cationic monomer structural unit is 0 to 15 parts by weight;

preferably, the anionic monomer structural unit is a structural unit derived from an anionic monomer, wherein the anionic monomer is selected from acrylic acid, alkali metal salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, alkali metal salts of methacrylic acid, ammonium salts of methacrylic acid, vinylsulfonic acid, alkali metal salts of vinylsulfonic acid, ammonium salts of vinylsulfonic acid, p-vinylbenzenesulfonic acid, alkali metal salts of p-vinylbenzenesulfonic acid, ammonium salts of p-vinylbenzenesulfonic acid, maleic acid, alkali metal salts of maleic acid, ammonium salts of maleic acid, fumaric acid, alkali metal salts of fumaric acid, ammonium salts of fumaric acid, vinylbenzenesulfonic acid, alkali metal salts of vinylbenzenesulfonic acid, ammonium salts of vinylbenzenesulfonic acid, allylsulfonic acid, alkali metal salts of allylsulfonic acid, ammonium salts of allylsulfonic acid, allylbenzenesulfonic acid, alkali metal salts of allylbenzenesulfonic acid, allylsulfonic acid, ammonium salts of allyl, One or more of ammonium salts of allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, alkali metal salts of 2-acrylamido-2-methylpropanesulfonic acid, and ammonium salts of 2-acrylamido-2-methylpropanesulfonic acid;

preferably, the nonionic monomer structural unit is a structural unit derived from a nonionic monomer, wherein the nonionic monomer is selected from one or more of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropyl methacrylamide, methylol methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and vinyl pyrrolidone;

preferably, the cationic monomer building block is a building block derived from a cationic monomer, wherein the cationic monomer is selected from one or more of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, epoxypropyl benzyl trimethyl ammonium chloride, epoxypropyl ethoxytrimethyl ammonium chloride, and epoxypropyl-trimethyl ammonium chloride-terminated polyethylene glycol.

4. The emulsion polymer for fracturing of any one of claims 1 to 3, wherein the emulsion polymer for fracturing has a weight average molecular weight of 800 to 2500 ten thousand, preferably 1500 to 2500 ten thousand; the molecular weight distribution is 0.2-0.8.

5. A preparation method of an emulsion polymer for fracturing comprises the following steps:

a) mixing an acrylamide monomer, an anionic monomer, a nonionic monomer, a surface active monomer, a cosolvent and a solvent, and optionally a cationic monomer, and adjusting the pH value to 5-10 to obtain an aqueous solution I;

b) dissolving an emulsifier in an oil solvent to obtain an oil solution II;

c) mixing an oxidant and an initiator to obtain an aqueous solution III, mixing the aqueous solution III with the aqueous solution I obtained in the step a), then mixing the aqueous solution I with the oil solution II obtained in the step b), and emulsifying to obtain an emulsion;

d) mixing the emulsion with a solution containing a reducing agent, carrying out redox reaction, and mixing with a phase transfer agent;

wherein the surface active monomer is selected from one or more of structures shown in a formula (V), a formula (VI), a formula (VII) and a formula (VIII),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄The same or different, are independently selected fromC₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

6. The method of claim 5, wherein each R is₁Each independently selected from hydrogen atom, C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); each R₂、R₃And R₄Each independently selected from C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); a. b is independently 3-14.

7. The method according to claim 5 or 6, wherein the amount of the acrylamide monomer is 25 to 75 parts by weight, the amount of the anionic monomer is 0.1 to 25 parts by weight, the amount of the nonionic monomer is 0.1 to 15 parts by weight, the amount of the surface active monomer is 0.001 to 5 parts by weight, the amount of the cosolvent is 0.1 to 10 parts by weight, the amount of the solvent is 10 to 70 parts by weight, and the amount of the cationic monomer is 0 to 15 parts by weight, the feeding amount of the emulsifier is 20-70 parts by weight, the feeding amount of the oil solvent is 50-90 parts by weight, the feeding amount of the oxidant is 0.00005-0.001 part by weight, the feeding amount of the initiator is 0.00001-0.001 part by weight, the feeding amount of the solution containing the reducing agent is 0.000005-0.001 part by weight, and the feeding amount of the phase transfer agent is 10-50 parts by weight, wherein the solution containing the reducing agent is calculated by the reducing agent, and the solvent is calculated by deionized water;

preferably, in the solution containing the reducing agent, the concentration of the reducing agent is 0.5-2 wt%;

preferably, the anionic monomer is selected from acrylic acid, alkali metal salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, alkali metal salts of methacrylic acid, ammonium salts of methacrylic acid, vinylsulfonic acid, alkali metal salts of vinylsulfonic acid, ammonium salts of vinylsulfonic acid, p-vinylbenzenesulfonic acid, alkali metal salts of p-vinylbenzenesulfonic acid, ammonium salts of p-vinylbenzenesulfonic acid, maleic acid, alkali metal salts of maleic acid, ammonium salts of maleic acid, fumaric acid, alkali metal salts of fumaric acid, ammonium salts of fumaric acid, vinylbenzenesulfonic acid, alkali metal salts of vinylbenzenesulfonic acid, ammonium salts of vinylbenzenesulfonic acid, allylsulfonic acid, alkali metal salts of allylsulfonic acid, ammonium salts of allylsulfonic acid, allylbenzenesulfonic acid, alkali metal salts of allylbenzenesulfonic acid, ammonium salts of allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, one or more of an alkali metal salt of 2-acrylamido-2-methylpropanesulfonic acid and an ammonium salt of 2-acrylamido-2-methylpropanesulfonic acid;

preferably, the nonionic monomer is selected from one or more of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropyl methacrylamide, methylolmethacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and vinylpyrrolidone;

preferably, the cosolvent is selected from one or more of sodium formate, urea, thiourea and anhydrous sodium sulfate;

preferably, the solvent is deionized water;

preferably, the cationic monomer is selected from one or more of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, epoxypropyl benzyl trimethyl ammonium chloride, epoxypropyl ethoxy trimethyl ammonium chloride, and epoxypropyl-trimethyl ammonium chloride-terminated polyethylene glycol;

preferably, the oil solvent is selected from one or more of aliphatic hydrocarbon, aromatic hydrocarbon, mineral oil and vegetable oil;

more preferably, the aliphatic hydrocarbon is selected from one or more of cyclohexane, hexane, heptane, octane and isooctane;

more preferably, the aromatic hydrocarbon is selected from one or more of benzene, toluene, ethylbenzene, xylene and cumene;

more preferably, the mineral oil is selected from one or more of liquid paraffin, white oil, gasoline, diesel oil and kerosene;

more preferably, the vegetable oil is selected from one or more of peanut oil, soybean oil, sunflower oil and castor oil;

preferably, the oxidizing agent is selected from one or more of persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, tert-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate and dicyclohexyl peroxydicarbonate;

preferably, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutyrimidazoline hydrochloride, and azobisisobutyronitrile formamide;

preferably, the reducing agent is selected from one or more of sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N-dimethylaniline, tartaric acid, ferrous sulfate, N-diethylaniline, ferrous pyrophosphate, silver nitrate, mercaptan, ferrous chloride, tetraethyleneimine, glycerol and pentaerythritol;

preferably, the emulsifier and the phase inverter are respectively and independently selected from one or more of fatty alcohol polyoxypropylene polyoxyethylene ether shown in formula (i), aromatic alcohol polyoxypropylene polyoxyethylene ether shown in formula (ii), fatty acid polyoxypropylene polyoxyethylene ester shown in formula (iii), fatty amine polyoxypropylene polyoxyethylene ether shown in formula (iv), sorbitan oleate, sorbitan stearate, sorbitan palmitate and sorbitan laurate,

wherein R is¹、R²And R³Each independently selected from C₁～C₂₈A hydrocarbon group of (a); r⁴And R⁵From hydrogen atoms or C₁～C₂₈And R is a hydrocarbon group of⁴And R⁵Cannot be simultaneously hydrogen atoms; m is selected from 0-30; n is 1-40;

preferably, R¹、R²And R³Each independently selected from C₆～C₁₄A hydrocarbon group of (a); r⁴And R⁵From hydrogen atoms or C₆～C₁₄And R is a hydrocarbon group of⁴And R⁵Cannot be simultaneously hydrogen atoms; m is selected from 3-16; n is selected from 3 to 16.

8. The method according to any one of claims 5 to 7, wherein in step a), the pH is adjusted to 6 to 8;

preferably, in step b), the temperature of the dissolution is not more than 25 ℃, preferably 0-25 ℃;

preferably, in step c), the emulsification conditions comprise: the rotating speed is 10000-25000 r/min, and the emulsifying time is 2-15 min;

preferably, in step d), the mixing conditions of the emulsion with the reducing agent comprise: the temperature is 5-15 ℃;

preferably, in step d), the redox reaction conditions include: the temperature is 40-50 ℃ and the time is 1-4 h.

9. An emulsion polymer for fracturing prepared by the method of any one of claims 5 to 8.

10. Use of the emulsion polymer for fracturing of any of claims 1 to 4 and 9 and/or the emulsion polymer for fracturing prepared according to the method of any of claims 5 to 8 in a fracturing process.

Technical Field

The invention belongs to the field of fracturing fluids, and particularly relates to an emulsion polymer for fracturing and a preparation method and application thereof.

Background

As an important measure for stratum reconstruction of an oil and gas reservoir, fracturing is rapidly developed and widely applied, the efficiency is remarkably increased, fracturing construction is carried out in 7 months in 2004 by taking 11-53 wells as an example of a Chinese oilfield well, 663 tons of oil are increased in the year, namely 4.42 tons of oil are increased in the day, the daily income is about 16575 yuan calculated by 75 dollars/barrel of crude oil, and the income is increased by about 250 ten thousand in the year.

The two most main parts in the fracturing fluid are respectively a thickening agent (thickening agent) and a drag reducer, wherein the thickening agent mainly plays a role in increasing the viscosity of the fluid and improving the sand carrying capacity of the fluid, and the drag reducer mainly plays a role in reducing the turbulent flow resistance and reducing the energy consumption. In the application, the fracturing fluid thickening agent mainly takes natural macromolecules such as guar gum and the like, part of synthetic polymers are also used as the thickening agent for the fracturing fluid, and the drag reducer mainly takes the synthetic polymers as the main components. The most commonly used fracturing fluid in China is a water-based fracturing fluid, which can be roughly 3 types: (1) natural plant gum fracturing fluid; (2) a cellulosic fracturing fluid; (3) and synthesizing the polymer fracturing fluid. The fracturing fluid systems have the advantages, are widely applied to various oil fields at home and abroad, and achieve good yield increasing effect. However, these fracturing fluid systems still have defects, such as insufficient temperature resistance, incomplete gel breaking, poor crosslinking controllability and the like. The natural polymer has the great defects, for example, even the first-grade hydroxypropyl guar gum has the water-insoluble content of more than 8 percent, and simultaneously has more residues, so that the damage to stratum and cracks is great; and the crosslinking condition is alkalescent and is not suitable for alkali-sensitive stratum. Meanwhile, the demand of the guanidine gum market caused by the sharp increase of the demand quantity is short, the price is high, and the price is one of the bottlenecks of the fracturing technology, and the highest price reaches more than 15 ten thousand per ton once in 2012. Moreover, the common emulsion polyacrylamide mainly comprises acrylamide and acrylic acid, mainly depends on high molecular weight to provide viscosity, is sensitive to salt, and cannot provide high aqueous phase viscosity under the condition of high salt.

In addition, the synthesized dry powder polymer needs special dissolving equipment and has complex preparation process. The current volume fracturing makes the fracturing construction put higher demands on the instant dissolution of the polymer. Meanwhile, the fracturing fluid has various auxiliaries, a complex formula and large mutual influence among the auxiliaries, so that the fracturing emulsion polymer which can simultaneously give consideration to thickening and resistance reduction can effectively reduce the complexity of a system, reduce the mutual influence among the auxiliaries, meet the requirement of fracturing construction on instant dissolution, simplify preparation equipment and realize cost reduction and efficiency improvement.

Disclosure of Invention

The invention aims to solve the technical problems of the prior art and provides an emulsion polymer for fracturing and a preparation method and application thereof. The emulsion polymer for fracturing has high tackifying capability under the condition of high salt and high drag reduction efficiency under the condition of low concentration, can simplify the existing fracturing construction process, realizes the multi-effect of one thickening agent and one drag reduction agent, and reduces the mutual influence among various auxiliary agents in construction.

To this end, the first aspect of the present invention provides an emulsion polymer for fracturing, which comprises an acrylamide monomer structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, a surface active monomer structural unit, and optionally a cationic monomer structural unit, wherein the surface active monomer structural unit is selected from one or more of structural units represented by formula (I), formula (II), formula (III) and formula (IV),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are independently selected from ester, amide, methylene, or a mixture thereof,Oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

The second aspect of the invention provides a preparation method of an emulsion polymer for fracturing, which comprises the following steps:

a) mixing an acrylamide monomer, an anionic monomer, a nonionic monomer, a surface active monomer, a cosolvent and a solvent, and optionally a cationic monomer, and adjusting the pH value to 5-10 to obtain an aqueous solution I;

b) dissolving an emulsifier in an oil solvent to obtain an oil solution II;

c) mixing an oxidant and an initiator to obtain an aqueous solution III, mixing the aqueous solution III with the aqueous solution I obtained in the step a), then mixing the aqueous solution I with the oil solution II obtained in the step b), and emulsifying to obtain an emulsion;

d) mixing the emulsion with a solution containing a reducing agent, carrying out redox reaction, and mixing with a phase transfer agent;

wherein the surface active monomer is selected from one or more of structures shown in a formula (V), a formula (VI), a formula (VII) and a formula (VIII),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride ion, chloride ionA bromide ion or an iodide ion.

The third aspect of the invention provides the emulsion polymer for fracturing prepared by the method.

In a fourth aspect, the invention provides the use of a fracturing emulsion polymer as described above and/or prepared according to the method described above in a fracturing process.

Detailed Description

In order that the present invention may be more readily understood, the following detailed description of the invention is given by way of example only, and is not intended to limit the scope of the invention.

As previously mentioned, current dry powder polymers are complex to dissolve and do not meet current large volume drag reduction requirements. In addition, the existing emulsion type propylene milling amine polymer has poor salt resistance and cannot provide higher aqueous phase viscosity under the high-salt condition. In addition, the existing emulsion polymers for fracturing cannot achieve both thickening and drag reduction effects. At present, a multi-effect emulsion polymer for fracturing, which has higher tackifying capability under a high-salt condition, has better drag reduction efficiency under a low-concentration condition and can realize both thickening and drag reduction, needs to be researched and developed.

The first aspect of the invention provides an emulsion polymer for fracturing, which comprises an acrylamide monomer structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, a surface active monomer structural unit and an optional cationic monomer structural unit, wherein the surface active monomer structural unit is selected from one or more structural units shown in a formula (I), a formula (II), a formula (III) and a formula (IV),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈Of (2) a hydrocarbon group；R₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

In the present invention, in the formula (II) and the formula (III), it is preferable that a and b are not 0 at the same time. For example, in formula (II), a and b are not 0 at the same time.

In the invention, the position of the a chain segment and the b chain segment can be changed, which means that the position of the a chain segment and the position of the b chain segment in the formula (II), the formula (III), the formula (VI) and the formula (VII) can be changed,

for example, formula (II) may be:

for another example, formula (III) can be:

in the present invention, in the structural units represented by the formula (I), the formula (II), the formula (III) and the formula (IV), each a and b may be the same or different, and each R is₁、R₂、R₃And R₄May be the same or different.

According to a preferred embodiment of the invention, each R₁Each independently selected from hydrogen atom, C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); each R₂、R₃And R₄Each independently selected from C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); a. b is independently 3-14.

According to a preferred embodiment of the present invention, in the emulsion polymer for fracturing, the content of the acrylamide monomer structural unit is 25 to 75 parts by weight, the content of the anionic monomer structural unit is 0.1 to 25 parts by weight, the content of the nonionic monomer structural unit is 0.1 to 15 parts by weight, the content of the surface active monomer structural unit is 0.001 to 5 parts by weight, and the content of the cationic monomer structural unit is 0 to 15 parts by weight.

According to a preferred embodiment of the invention, the anionic monomer building block is a building block derived from an anionic monomer selected from the group consisting of acrylic acid, alkali metal salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, alkali metal salts of methacrylic acid, ammonium salts of methacrylic acid, vinylsulfonic acid, alkali metal salts of vinylsulfonic acid, ammonium salts of vinylsulfonic acid, p-vinylbenzenesulfonic acid, alkali metal salts of p-vinylbenzenesulfonic acid, ammonium salts of p-vinylbenzenesulfonic acid, maleic acid, alkali metal salts of maleic acid, ammonium salts of maleic acid, fumaric acid, alkali metal salts of fumaric acid, vinylbenzenesulfonic acid, alkali metal salts of vinylbenzenesulfonic acid, ammonium salts of vinylbenzenesulfonic acid, allylsulfonic acid, alkali metal salts of allylsulfonic acid, ammonium salts of allylsulfonic acid, allylbenzenesulfonic acid, allylsulfonic, One or more of an alkali metal salt of allylbenzenesulfonic acid, an ammonium salt of allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, an alkali metal salt of 2-acrylamido-2-methylpropanesulfonic acid, and an ammonium salt of 2-acrylamido-2-methylpropanesulfonic acid.

According to a preferred embodiment of the present invention, in the anionic monomer, the alkali metal salt is selected from one or more of lithium salt, sodium salt and potassium salt. For example, the sodium salt may be sodium acrylate, sodium methacrylate, sodium vinylsulfonate, sodium p-vinylbenzenesulfonate, sodium maleate, sodium fumarate, sodium vinylbenzenesulfonate, sodium allylsulfonate, sodium allylbenzenesulfonate, sodium 2-acrylamido-2-methylpropanesulfonate. Lithium and potassium salts are similar to sodium salts.

According to a preferred embodiment of the present invention, in the anionic monomer, the ammonium salt is a salt having an ammonium ion and/or an organic amine salt. Wherein the salt having ammonium ion can be ammonium acrylate, ammonium methacrylate, ammonium vinylsulfonate, ammonium p-vinylbenzenesulfonate, ammonium maleate, ammonium fumarate, ammonium vinylbenzenesulfonate, ammonium allylsulfonate, ammonium allylbenzenesulfonate, or ammonium 2-acrylamido-2-methylpropanesulfonate. Wherein the organic ammonium salt can be an ammonium salt formed by acid and ethanolamine and/or triethanolamine. For example, ammonium salts of acrylic acid, ammonium salts formed from acrylic acid and ethanolamine and/or triethanolamine. The ammonium salts of the other substances are similar to the ammonium salts of acrylic acid.

Further preferably, the anionic monomer is acrylic acid and/or sodium 2-acrylamido-2-methylpropanesulfonate.

According to a preferred embodiment of the present invention, the nonionic monomer structural unit is a structural unit derived from a nonionic monomer, wherein the nonionic monomer is selected from one or more of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropyl methacrylamide, methylol methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and vinyl pyrrolidone.

According to a preferred embodiment of the present invention, the cationic monomer building block is a building block derived from a cationic monomer, wherein the cationic monomer is selected from one or more of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, epoxypropyl benzyl trimethyl ammonium chloride, epoxypropyl ethoxytrimethyl ammonium chloride and epoxypropyl-trimethyl ammonium chloride capped polyethylene glycols.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing has a weight average molecular weight of 800 to 2500 ten thousand, preferably 1500 to 2500 ten thousand.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing has a molecular weight distribution of 0.2 to 0.8.

The second aspect of the invention provides a preparation method of an emulsion polymer for fracturing, which comprises the following steps:

a) mixing an acrylamide monomer, an anionic monomer, a nonionic monomer, a surface active monomer, a cosolvent and a solvent, and optionally a cationic monomer, and adjusting the pH value to 5-10 to obtain an aqueous solution I;

b) dissolving an emulsifier in an oil solvent to obtain an oil solution II;

c) mixing an oxidant and an initiator to obtain an aqueous solution III, mixing the aqueous solution III with the aqueous solution I obtained in the step a), then mixing the aqueous solution I with the oil solution II obtained in the step b), and emulsifying to obtain an emulsion;

d) mixing the emulsion with a solution containing a reducing agent, carrying out redox reaction, and mixing with a phase transfer agent;

wherein the surface active monomer is selected from one or more of structures shown in a formula (V), a formula (VI), a formula (VII) and a formula (VIII),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each R₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

In the present invention, in formula (VI) and formula (VII), it is preferable that a and b are not 0 at the same time. For example, in formula (VI), a and b are not both 0 at the same time.

In the present invention, when the synthesis is carried out using the surface active monomer represented by the formula (V), the sulfonic acid group in the formula (V) will become a sodium sulfonate group due to a neutralization process occurring at the time of the synthesis, and therefore the surface active monomer structural unit derived from the structural unit of the formula (V) formula (I) has a sodium sulfonate group.

According to a more preferred embodiment of the invention, each R is₁Each independently selected from hydrogen atom, C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); each R₂、R₃And R₄Each independently selected from C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); a. b is independently 3-14.

For example, the surface active monomer is cetyl dimethyl allyl ammonium chloride (formula (IX)), sodium 2-acrylamidotetradecyl sulfonate (formula (X)), allyl polyoxyethylene polyoxypropylene ether (EO10PO5, formula (XI)), etc.,

according to a preferred embodiment of the present invention, the amount of the acrylamide monomer is 25 to 75 parts by weight, the amount of the anionic monomer is 0.1 to 25 parts by weight, the amount of the nonionic monomer is 0.1 to 15 parts by weight, the amount of the surface active monomer is 0.001 to 5 parts by weight, the amount of the cosolvent is 0.1 to 10 parts by weight, the amount of the solvent is 10 to 70 parts by weight, the amount of the cationic monomer is 0 to 15 parts by weight, the amount of the emulsifier is 20 to 70 parts by weight, the amount of the oil solvent is 50 to 90 parts by weight, the amount of the oxidant is 0.00005 to 0.001 part by weight, the amount of the initiator is 0.00001 to 0.001 part by weight, the amount of the solution containing the reducing agent is 0.000005 to 0.001 part by weight, and the amount of the phase transfer agent is 10 to 50 parts by weight, wherein the solution containing the reducing agent is calculated by the reducing agent and the solvent is deionized water. Within the preferable dosage range of the invention, the obtained fracturing emulsion has better thickening or drag reduction effect.

According to a preferred embodiment of the present invention, the concentration of the reducing agent in the solution containing the reducing agent is 0.5 to 2% by weight. Such as 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, and any value therebetween.

According to a preferred embodiment of the invention, the anionic monomer is selected from acrylic acid, alkali metal salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, alkali metal salts of methacrylic acid, ammonium salts of methacrylic acid, vinylsulphonic acid, alkali metal salts of vinylsulphonic acid, ammonium salts of vinylsulphonic acid, p-vinylbenzenesulphonic acid, alkali metal salts of p-vinylbenzenesulphonic acid, ammonium salts of maleic acid, alkali metal salts of maleic acid, ammonium salts of maleic acid, fumaric acid, alkali metal salts of fumaric acid, ammonium salts of fumaric acid, vinylbenzenesulphonic acid, alkali metal salts of vinylbenzenesulphonic acid, ammonium salts of vinylbenzenesulphonic acid, allylsulphonic acid, alkali metal salts of allylsulphonic acid, ammonium salts of allylsulphonic acid, allylbenzenesulphonic acid, alkali metal salts of allylbenzenesulphonic acid, ammonium salts of allylbenzenesulphonic acid, 2-acrylamido-2-methylpropanesulphonic acid, 2-methylpropanesulphon, One or more of an alkali metal salt of 2-acrylamido-2-methylpropanesulfonic acid and an ammonium salt of 2-acrylamido-2-methylpropanesulfonic acid.

According to a preferred embodiment of the present invention, in the anionic monomer, the alkali metal salt is selected from one or more of lithium salt, sodium salt and potassium salt. For example, the sodium salt may be sodium acrylate, sodium methacrylate, sodium vinylsulfonate, sodium p-vinylbenzenesulfonate, sodium maleate, sodium fumarate, sodium vinylbenzenesulfonate, sodium allylsulfonate, sodium allylbenzenesulfonate, sodium 2-acrylamido-2-methylpropanesulfonate. Lithium and potassium salts are similar to sodium salts.

According to a preferred embodiment of the present invention, in the anionic monomer, the ammonium salt is a salt having an ammonium ion and/or an organic amine salt. Wherein the salt having ammonium ion can be ammonium acrylate, ammonium methacrylate, ammonium vinylsulfonate, ammonium p-vinylbenzenesulfonate, ammonium maleate, ammonium fumarate, ammonium vinylbenzenesulfonate, ammonium allylsulfonate, ammonium allylbenzenesulfonate, or ammonium 2-acrylamido-2-methylpropanesulfonate. Wherein the organic ammonium salt can be an ammonium salt formed by acid and ethanolamine and/or triethanolamine. For example, ammonium salts of acrylic acid, ammonium salts formed from acrylic acid and ethanolamine and/or triethanolamine. The ammonium salts of the other substances are similar to the ammonium salts of acrylic acid.

Further preferably, the anionic monomer is acrylic acid and/or sodium 2-acrylamido-2-methylpropanesulfonate.

According to a preferred embodiment of the invention, the non-ionic monomer is selected from one or more of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropyl methacrylamide, methylol methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and vinylpyrrolidone.

According to a preferred embodiment of the invention, the co-solvent is selected from one or more of sodium formate, urea, thiourea and anhydrous sodium sulphate.

According to an embodiment of the present invention, the solvent may be a liquid capable of dissolving acrylamide monomer, anionic monomer, nonionic monomer, surface active monomer, co-solvent, and optionally cationic monomer, and preferably, the solvent is deionized water.

According to a preferred embodiment of the present invention, the cationic monomer is selected from one or more of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, epoxypropyl benzyl trimethyl ammonium chloride, epoxypropyl ethoxy trimethyl ammonium chloride and epoxypropyl-trimethyl ammonium chloride terminated polyethylene glycol.

According to a preferred embodiment of the present invention, the oil solvent is selected from one or more of aliphatic hydrocarbons, aromatic hydrocarbons, mineral oils and vegetable oils. Preferably, the aliphatic hydrocarbon is selected from one or more of cyclohexane, hexane, heptane, octane and isooctane. Preferably, the aromatic hydrocarbon is selected from one or more of benzene, toluene, ethylbenzene, xylene and cumene. Preferably, the mineral oil is selected from one or more of liquid paraffin, white oil, gasoline, diesel oil and kerosene. Preferably, the vegetable oil is selected from one or more of peanut oil, soybean oil, sunflower oil and castor oil. Preferably, the white oil is a number 5 white oil.

According to an embodiment of the present invention, the oxidizing agent is selected from one or more of persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, potassium bromate, t-butyl hydroperoxide, lauroyl peroxide, cumene hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, t-butyl peroxybenzoate, t-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, and dicyclohexyl peroxydicarbonate.

According to a preferred embodiment of the invention, the initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutyrimidazoline hydrochloride and azobisisobutyro-cyano formamide.

According to an embodiment of the present invention, the reducing agent is selected from one or more of sodium bisulfite, sodium thiosulfate, sodium dithionite, sodium metabisulfite, tetramethylethylenediamine, ferrous ammonium sulfate, sodium formaldehyde sulfoxylate, N-dimethylaniline, tartaric acid, ferrous sulfate, N-diethylaniline, ferrous pyrophosphate, silver nitrate, mercaptans, ferrous chloride, tetraethyleneimine, glycerol and pentaerythritol.

According to an embodiment of the present invention, the emulsifier and the phase inverter are respectively and independently selected from one or more of fatty alcohol polyoxypropylene polyoxyethylene ether represented by formula (i), aromatic alcohol polyoxypropylene polyoxyethylene ether represented by formula (ii), fatty acid polyoxypropylene polyoxyethylene ester represented by formula (iii), fatty amine polyoxypropylene polyoxyethylene ether represented by formula (iv), sorbitan oleate, sorbitan stearate, sorbitan palmitate and sorbitan laurate,

wherein R is¹、R²And R³Each independently selected from C₁～C₂₈A hydrocarbon group of (a); r⁴And R⁵From hydrogen atoms or C₁～C₂₈And R is a hydrocarbon group of⁴And R⁵Cannot be simultaneously hydrogen atoms; m is selected from 0-30; n is 1-40;

preferably, R¹、R²And R³Each independently selected from C₆～C₁₄A hydrocarbon group of (a); r⁴And R⁵From hydrogen atoms or C₆～C₁₄And R is a hydrocarbon group of⁴And R⁵Cannot be simultaneously hydrogen atoms; m is selected from 3-16; n is selected from 3 to 16.

For example, the emulsifier is sorbitan oleate and/or fatty alcohol-polyoxyethylene ether (the structural formula is formula (v), which is formula (i), m is 0, R is¹Is C₁₃H₂₇N is 12),

for example, the phase transfer agent is fatty alcohol polyoxypropylene polyoxyethylene ether (the structural formula is formula (vi), which is formula (i), m is 0, R is¹Is C₁₃H₂₇N is 8),

in the preparation method, the phase inversion agent is added, so that the water solubility of the emulsion polymer product for fracturing is improved, the dissolving time is shortened, the polymer molecular chain can be fully dissolved in water, and the drag reduction rate is improved.

According to a preferred embodiment of the invention, in step a), the pH is adjusted to 6 to 8. For example, the pH is 6, 7, 8, and any value in between. In the present invention, sodium hydroxide, potassium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium carbonate, potassium carbonate and the like can be used for adjusting the pH, and sodium hydroxide is preferred. When the synthesis conditions are too acidic (e.g., pH 4 and below 4), the drag reduction rate may decrease due to too low a molecular weight; the viscosity is low. When the synthesis conditions are too basic (for example, pH values of 11 and 11 or more), the polymerization causes side reactions in the polymerization to increase, the molecular weight to be too high, and the drag reduction rate to decrease; side reactions increase crosslinking during polymerization, the dissolution time increases significantly, and the increase in insolubles also decreases viscosity. Therefore, in the preferable pH value range (the pH value is 5-10) of the invention, the emulsion polymer for fracturing with better effect can be synthesized more favorably.

According to a preferred embodiment of the invention, in step b), the temperature of dissolution is not greater than 25 ℃, preferably 0 to 25 ℃. For example, 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, and any value therebetween. The temperature of the solution can be cooled by using a cooling jacket. The emulsion polymer for fracturing of the present invention is preferably synthesized in a preferable temperature range of the present invention.

According to a preferred embodiment of the invention, in step c), the conditions of emulsification comprise: the rotating speed is 10000-25000 r/min, and the emulsifying time is 2-15 min. In the present invention, the emulsifying apparatus may be a high shear emulsifying machine which is conventional in the art.

According to a preferred embodiment of the invention, in step d), the mixing conditions of the emulsion with the reducing agent comprise: the temperature is 5-15 ℃. In the invention, the equipment for mixing the emulsion and the reducing agent can be a reaction kettle, and the mixing of the emulsion and the reducing agent can be controlled to be 5-15 ℃ by a water bath method. The conditions for mixing the emulsion with the reducing agent may further include: and introducing inert gas under continuous stirring at the stirring speed of 200-500 r/min. The purpose of introducing the inert gas is to remove oxygen in the reaction vessel.

According to a preferred embodiment of the present invention, in step d), the redox reaction conditions include: the temperature is 40-50 ℃ and the time is 1-4 h. For example, at 40 ℃ for 2 h.

According to a preferred embodiment of the present invention, the time for mixing with the phase inversion agent in step d) is 0.5 to 2 hours.

According to a preferred embodiment of the present invention, the method for preparing the emulsion polymer for fracturing comprises

a) Mixing an acrylamide monomer, an anionic monomer, a nonionic monomer, an active monomer, a cosolvent and a solvent, and optionally a cationic monomer, and adjusting the pH value to 5-10 to obtain an aqueous solution I;

b) dissolving an emulsifier in an oil solvent, and controlling the temperature to be not more than 25 ℃ to obtain an oil solution II;

c) mixing an oxidant and an initiator to obtain an aqueous solution III, then adding the aqueous solution III into the aqueous solution I obtained in the step a), then adding the aqueous solution I into the oil solution II obtained in the step b), and emulsifying for 5min at the rotating speed of 10000-25000 r/min under a high-speed shearing emulsifying machine to obtain an emulsion;

d) adding the emulsion into a reaction kettle, setting the stirring speed at 200-500r/min, introducing inert gas for deoxygenation under continuous stirring, then controlling the temperature at 5-15 ℃ through a water bath, slowly dropwise adding a solution containing a reducing agent into the emulsion, slowly heating at the heating rate of 0.05-0.5 ℃/min, maintaining the stirring speed at 200-500r/min until the temperature is raised to 40-50 ℃, carrying out redox reaction for 1-4 h, then slowly dropwise adding a phase transfer agent, and stirring for 0.5-2 h.

The third aspect of the invention provides the emulsion polymer for fracturing prepared by the method.

According to a preferred embodiment of the invention, the emulsion polymer for fracturing comprises an acrylamide monomer structural unit, an anionic monomer structural unit, a nonionic monomer structural unit, a surface active monomer structural unit and an optional cationic monomer structural unit, wherein the surface active monomer structural unit is selected from one or more of structural units shown in a formula (I), a formula (II), a formula (III) and a formula (IV),

wherein each R is₁Same or different, each independently selected from hydrogen atom or C₁～C₂₈A hydrocarbon group of (a); each one ofR₂、R₃And R₄Same or different, each independently selected from C₁～C₂₈A hydrocarbon group of (a); r₅Selected from hydrogen atoms, amino groups, carboxylic acid groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, mercapto groups or halogens; each a and b are the same or different and are respectively 0-40 independently, and the positions of the chain segments of the a and the b can be exchanged; x, Y and Z are each independently selected from ester group, amide group, methylene group, oxygen atom, -CH₂-O-or-NH-; m^-Selected from fluoride, chloride, bromide or iodide.

In the present invention, in the formula (II) and the formula (III), it is preferable that a and b are not 0 at the same time. For example, in formula (II), a and b are not 0 at the same time.

In the present invention, in the structural units represented by the formula (I), the formula (II), the formula (III) and the formula (IV), each a and b may be the same or different, and each R is₁、R₂、R₃And R₄May be the same or different.

According to a preferred embodiment of the invention, each R₁Each independently selected from hydrogen atom, C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); each R₂、R₃And R₄Each independently selected from C₆～C₁₈Alkyl or C₆～C₁₈An aromatic group of (a); a. b is independently 3-14.

According to a preferred embodiment of the present invention, in the emulsion polymer for fracturing, the content of the acrylamide monomer structural unit is 25 to 75 parts by weight, the content of the anionic monomer structural unit is 0.1 to 25 parts by weight, the content of the nonionic monomer structural unit is 0.1 to 15 parts by weight, the content of the surface active monomer structural unit is 0.001 to 5 parts by weight, and the content of the cationic monomer structural unit is 0 to 15 parts by weight.

According to a preferred embodiment of the invention, the anionic monomer building block is a building block derived from an anionic monomer selected from the group consisting of acrylic acid, alkali metal salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, alkali metal salts of methacrylic acid, ammonium salts of methacrylic acid, vinylsulfonic acid, alkali metal salts of vinylsulfonic acid, ammonium salts of vinylsulfonic acid, p-vinylbenzenesulfonic acid, alkali metal salts of p-vinylbenzenesulfonic acid, ammonium salts of p-vinylbenzenesulfonic acid, maleic acid, alkali metal salts of maleic acid, ammonium salts of maleic acid, fumaric acid, alkali metal salts of fumaric acid, vinylbenzenesulfonic acid, alkali metal salts of vinylbenzenesulfonic acid, ammonium salts of vinylbenzenesulfonic acid, allylsulfonic acid, alkali metal salts of allylsulfonic acid, ammonium salts of allylsulfonic acid, allylbenzenesulfonic acid, allylsulfonic, One or more of an alkali metal salt of allylbenzenesulfonic acid, an ammonium salt of allylbenzenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, an alkali metal salt of 2-acrylamido-2-methylpropanesulfonic acid, and an ammonium salt of 2-acrylamido-2-methylpropanesulfonic acid.

According to a preferred embodiment of the present invention, in the anionic monomer, the alkali metal salt is selected from one or more of lithium salt, sodium salt and potassium salt. For example, the sodium salt may be sodium acrylate, sodium methacrylate, sodium vinylsulfonate, sodium p-vinylbenzenesulfonate, sodium maleate, sodium fumarate, sodium vinylbenzenesulfonate, sodium allylsulfonate, sodium allylbenzenesulfonate, sodium 2-acrylamido-2-methylpropanesulfonate. Lithium and potassium salts are similar to sodium salts.

According to a preferred embodiment of the present invention, in the anionic monomer, the ammonium salt is a salt having an ammonium ion and/or an organic amine salt. Wherein the salt having ammonium ion can be ammonium acrylate, ammonium methacrylate, ammonium vinylsulfonate, ammonium p-vinylbenzenesulfonate, ammonium maleate, ammonium fumarate, ammonium vinylbenzenesulfonate, ammonium allylsulfonate, ammonium allylbenzenesulfonate, or ammonium 2-acrylamido-2-methylpropanesulfonate. Wherein the organic ammonium salt can be an ammonium salt formed by acid and ethanolamine and/or triethanolamine. For example, ammonium salts of acrylic acid, ammonium salts formed from acrylic acid and ethanolamine and/or triethanolamine. The ammonium salts of the other substances are similar to the ammonium salts of acrylic acid.

Further preferably, the anionic monomer is acrylic acid and/or sodium 2-acrylamido-2-methylpropanesulfonate.

According to a preferred embodiment of the present invention, the nonionic monomer structural unit is a structural unit derived from a nonionic monomer, wherein the nonionic monomer is selected from one or more of methacrylamide, dimethylacrylamide, diethylacrylamide, methylolacrylamide, hydroxyethylacrylamide, dimethylaminopropyl methacrylamide, methylol methacrylate, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and vinyl pyrrolidone.

According to a preferred embodiment of the present invention, the cationic monomer building block is a building block derived from a cationic monomer, wherein the cationic monomer is selected from one or more of methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methylpropyl trimethyl ammonium chloride, dimethylethyl allyl ammonium chloride, dimethyldiallyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, epoxypropyl trimethyl ammonium chloride, epoxypropyl benzyl trimethyl ammonium chloride, epoxypropyl ethoxytrimethyl ammonium chloride and epoxypropyl-trimethyl ammonium chloride capped polyethylene glycols.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing has a weight average molecular weight of 800 to 2500 ten thousand, preferably 1500 to 2500 ten thousand.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing has a molecular weight distribution of 0.2 to 0.8.

In a fourth aspect, the invention provides the use of a fracturing emulsion polymer as described above and/or prepared according to the method described above in a fracturing process.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing of the present invention can be used as a thickener or drag reducer in a fracturing fluid.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing of the present invention is used as a thickener in a concentration of more than 0.3 to 6% by weight.

According to a preferred embodiment of the present invention, the emulsion polymer for fracturing of the present invention is used as a drag reducer when the concentration thereof is more than 0.05 to 0.2% by weight.

According to the invention, anionic monomers, nonionic monomers, surface active monomers and optional cationic monomers are introduced into the polyacrylamide subjected to inverse emulsion polymerization, so that the viscosity of the polymerized emulsion in saline water is greatly improved, and meanwhile, the emulsion polymer can realize the drag reduction effect of the polymer at low concentration, so that one agent has multiple effects; and the complex emulsifier and the phase inversion agent are matched for use, so that the emulsion in a water-in-oil state can be rapidly dispersed and dissolved in the saline water, and the requirements on salt resistance and instant dissolution in fracturing construction are met.

[ example 1 ]

This example illustrates the preparation of the emulsion polymer for fracturing of the present invention.

a) Adding 45 parts by weight of acrylamide, 5 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 3 parts by weight of vinyl pyrrolidone, 1 part by weight of hexadecyl dimethyl allyl ammonium chloride and 0.5 part by weight of urea into 60 parts by weight of deionized water, and adjusting the pH value to 7 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 60 parts by weight of sorbitan oleate and 4 parts by weight of fatty alcohol-polyoxyethylene ether in 50 parts of No. 5 white oil, and controlling the temperature to be 25 ℃ to obtain an oil solution II;

c) mixing 0.0009 part by weight of potassium bromate with 0.0001 part by weight of azobisisobutyronitrile to obtain an aqueous solution III, adding the aqueous solution III into the aqueous solution I obtained in the step a), and uniformly stirring the mixture at a controlled temperature of 25 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, then controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.008 part by weight of aqueous solution containing sodium metabisulfite (the concentration of the sodium metabisulfite is 1 wt%) into the emulsion, slowly heating at a heating rate of 0.1 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 45 ℃, carrying out redox for 2h, slowly dropwise adding 32 parts by weight of fatty alcohol polyoxypropylene polyoxyethylene ether, and stirring for 1 h to obtain an emulsion polymer for fracturing;

the weight-average molecular weight of the emulsion polymer for fracturing was determined to be 1700 ten thousand, and the molecular weight distribution was determined to be 0.21. (the weight average molecular weight was measured by a static light scattering method (the same below); and the molecular weight distribution was measured by a static light scattering method (the same below)).

[ example 2 ]

This example illustrates the preparation of the emulsion polymer for fracturing of the present invention.

a) Adding 45 parts by weight of acrylamide, 5 parts by weight of acrylic acid, 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid sodium salt, 3 parts by weight of sodium p-vinylbenzenesulfonate, 1 part by weight of 2-acrylamidotetradecyl sodium salt and 0.5 part by weight of urea into 60 parts by weight of deionized water, and adjusting the pH value to 6 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 60 parts by weight of sorbitan oleate and 4 parts by weight of fatty alcohol-polyoxyethylene ether in 50 parts of No. 5 white oil, and controlling the temperature to be 25 ℃ to obtain an oil solution II;

c) mixing 0.0009 part by weight of potassium bromate with 0.0001 part by weight of azobisisobutyronitrile to obtain an aqueous solution III, adding the aqueous solution III into the aqueous solution I obtained in the step a), and uniformly stirring the mixture at a controlled temperature of 25 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.008 part by weight of aqueous solution containing sodium metabisulfite (the concentration of the sodium metabisulfite is 1 wt%) into the emulsion, slowly heating at a heating rate of 0.1 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 45 ℃, carrying out redox for 2h, slowly dropwise adding 32 parts by weight of fatty alcohol polyoxypropylene polyoxyethylene ether, and stirring for 1 h to obtain the emulsion polymer for fracturing.

The weight average molecular weight of the emulsion polymer for fracturing was 1800 ten thousand and the molecular weight distribution was 0.29.

[ example 3 ]

This example illustrates the preparation of the emulsion polymer for fracturing of the present invention.

a) Adding 45 parts by weight of acrylamide, 5 parts by weight of acrylic acid, 10 parts by weight of dimethyldiallylammonium chloride, 3 parts by weight of vinyl pyrrolidone, 1 part by weight of allyl polyoxyethylene polyoxypropylene ether (EO10PO5) and 0.5 part by weight of urea into 60 parts by weight of deionized water, and adjusting the pH value to be 8 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 60 parts by weight of sorbitan oleate and 4 parts by weight of fatty alcohol-polyoxyethylene ether in 50 parts of No. 5 white oil, and controlling the temperature to be 25 ℃ to obtain an oil solution II;

c) mixing 0.0009 part by weight of potassium bromate with 0.0001 part by weight of azobisisobutyronitrile to obtain an aqueous solution III, adding the aqueous solution III into the aqueous solution I obtained in the step a), and uniformly stirring the mixture at a controlled temperature of 25 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.008 part by weight of aqueous solution containing sodium metabisulfite (the concentration of the sodium metabisulfite is 1 wt%) into the emulsion, slowly heating at a heating rate of 0.1 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 45 ℃, carrying out redox for 2h, slowly dropwise adding 32 parts by weight of fatty alcohol polyoxypropylene polyoxyethylene ether, and stirring for 1 h to obtain the emulsion polymer for fracturing.

The weight average molecular weight of the emulsion polymer for fracturing was determined to be 2100 ten thousand, and the molecular weight distribution was determined to be 0.19.

[ example 4 ]

This example illustrates the preparation of the emulsion polymer for fracturing of the present invention.

a) Adding 25 parts by weight of acrylamide, 0.1 part by weight of vinyl benzene sulfonic acid, 0.1 part by weight of dimethyl diallyl ammonium chloride, 0.001 part by weight of allyl polyoxyethylene polyoxypropylene ether (EO10PO5) and 0.1 part by weight of thiourea into 70 parts by weight of deionized water, and adjusting the pH value to be 5 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 10 parts by weight of sorbitan palmitate and 10 parts by weight of sorbitan laurate in 50 parts of peanut oil, and controlling the temperature to be 5 ℃ to obtain an oil solution II;

c) mixing 0.00005 weight part of tert-butyl hydroperoxide and 0.00001 weight part of azobisisoheptonitrile to obtain an aqueous solution III, adding into the aqueous solution I obtained in the step a), and stirring uniformly at the controlled temperature of 5 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, then controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.01 part by weight of aqueous solution containing ammonium ferrous sulfate (the concentration of the ammonium ferrous sulfate is 0.5 wt%) into the emulsion, slowly heating up at a heating rate of 0.5 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 40 ℃, carrying out redox for 2h, slowly dropwise adding 10 parts by weight of sorbitan laurate, and stirring for 1 h to obtain the emulsion polymer for fracturing.

The weight average molecular weight of the emulsion polymer for fracturing was determined to be 1900 ten thousand, and the molecular weight distribution was determined to be 0.32.

[ example 5 ]

This example illustrates the preparation of the emulsion polymer for fracturing of the present invention.

a) Adding 75 parts by weight of acrylamide, 25 parts by weight of maleic acid, 1 part by weight of methacryloyloxyethyl trimethyl ammonium chloride, 15 parts by weight of hydroxymethyl methacrylate, 5 parts by weight of allyl polyoxyethylene polyoxypropylene ether (EO10PO5), and 10 parts by weight of anhydrous sodium sulfate into 10 parts by weight of deionized water, and adjusting the pH value to 5 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 70 parts by weight of sorbitan palmitate in 90 parts by weight of benzene, and controlling the temperature to be 20 ℃ to obtain an oil solution II;

c) 0.001 part by weight of sodium persulfate was mixed with 0.001 part by weight of dimethyl azodiisobutyrate to give an aqueous solution III, which was then added to the aqueous solution I obtained in step a) with stirring to homogeneity and at a controlled temperature of 20 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.5 part by weight of aqueous solution containing glycerol (the concentration of the glycerol is 2 wt%) into the emulsion, slowly heating at a heating rate of 0.05 ℃/min, maintaining the stirring speed at 300r/min until the temperature is raised to 50 ℃, carrying out redox for 2h, slowly dropwise adding 50 parts by weight of sorbitan oleate, and stirring for 1 h to obtain the emulsion polymer for fracturing.

The weight average molecular weight of the emulsion polymer for fracturing was 1800 ten thousand and the molecular weight distribution was 0.27.

[ COMPARATIVE EXAMPLE 1 ]

a) Adding 45 parts by weight of acrylamide and 5 parts by weight of acrylic acid into 60 parts by weight of deionized water, and adjusting the pH value to 7 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 60 parts by weight of sorbitan oleate and 4 parts by weight of fatty alcohol-polyoxyethylene ether in 50 parts of No. 5 white oil, and controlling the temperature to be 25 ℃ to obtain an oil solution II;

c) mixing 0.0009 part by weight of potassium bromate with 0.0001 part by weight of azobisisobutyronitrile to obtain an aqueous solution III, adding the aqueous solution III into the aqueous solution I obtained in the step a), and uniformly stirring the mixture at a controlled temperature of 25 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.008 part by weight of aqueous solution containing sodium metabisulfite (the concentration of the sodium metabisulfite is 1 wt%) into the emulsion, slowly heating at a heating rate of 0.1 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 45 ℃, carrying out redox for 2h, slowly dropwise adding 32 parts by weight of fatty alcohol polyoxypropylene polyoxyethylene ether, and stirring for 1 h to obtain the emulsion polymer for fracturing.

[ COMPARATIVE EXAMPLE 2 ]

a) Adding 45 parts by weight of acrylamide, 5 parts by weight of acrylic acid and 10 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid sodium salt into 60 parts by weight of deionized water, and adjusting the pH value to 7 by using sodium hydroxide to obtain an aqueous solution I;

b) dissolving 60 parts by weight of sorbitan oleate and 4 parts by weight of fatty alcohol-polyoxyethylene ether in 50 parts of No. 5 white oil, and controlling the temperature to be 25 ℃ to obtain an oil solution II;

c) mixing 0.0009 part by weight of potassium bromate with 0.0001 part by weight of azobisisobutyronitrile to obtain an aqueous solution III, adding the aqueous solution III into the aqueous solution I obtained in the step a), and uniformly stirring the mixture at a controlled temperature of 25 ℃. Then adding the mixture into the oil solution II obtained in the step b), and emulsifying for 5min at a rotating speed of 25000r/min under a high-speed shearing emulsifying machine to obtain emulsion;

d) adding the emulsion into a reaction kettle, introducing inert gas to remove oxygen for 30min at a stirring speed of 500r/min, controlling the temperature to be 15 ℃ through a water bath, slowly dropwise adding 0.008 part by weight of aqueous solution containing sodium metabisulfite (the concentration of the sodium metabisulfite is 1 wt%) into the emulsion, slowly heating at a heating rate of 0.1 ℃/min, maintaining the stirring rate at 300r/min until the temperature is raised to 45 ℃, carrying out redox for 2h, slowly dropwise adding 32 parts by weight of fatty alcohol polyoxypropylene polyoxyethylene ether, and stirring for 1 h to obtain the emulsion polymer for fracturing.

[ test examples ]

The dissolution time of the emulsion polymers for fracturing of examples 1 to 5 and comparative examples 1 to 2, the shear viscosity in 6000mg/L saline and the drag reduction rate were measured, respectively, and the results are shown in Table 1.

(1) The measurement of the dissolution time specifically comprises: 300g of deionized water was weighed into a beaker, and the emulsion polymer for fracturing was slowly added dropwise to the beaker at 500r/min and timed, and the dissolution time was recorded as the time during which the aqueous solution could be drawn down by contact with a stir bar.

(2) The measurement of the shear viscosity in 6000mg/L saline specifically comprises the following steps:

the emulsion polymer for fracturing was added to 6000mg/L of saline, and the concentration of the emulsion polymer for fracturing was 0.6% by weight. The shear viscosity was measured at 30 ℃ and a shear rate of 1701/s using a Haake rheometer coaxial cylinder model.

(3) The measurement of the drag reduction ratio specifically comprises the following steps:

the emulsion polymer for fracturing was added to deionized water at a concentration of 0.1 wt%. And (3) measuring the pipeline pressure difference under the discharge capacity of 12L/min at 25 ℃, and calculating according to a formula (I) to obtain the drag reduction rate.

Wherein P is₀Pressure difference P between two ends of pipeline when clear water flows₁Is the pressure difference between two ends of the pipeline when the polymer solution flows.

TABLE 1

According to the embodiment and the comparative example, and the results in table 1, it can be seen that the emulsion polymer for fracturing has higher tackifying capability under the condition of high salt and better drag reduction efficiency under the condition of low concentration, can simplify the existing fracturing construction process, and realizes multiple effects of one agent; and the complex emulsifier and the phase inversion agent are matched for use, so that the emulsion polymer in a water-in-oil state can be rapidly dispersed and dissolved in the saline water, and the requirements on salt resistance and instant dissolution in fracturing construction are met.

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.