阅读说明：本技术 耐盐型低温自破胶滑溜水降阻剂 (Salt-tolerant low-temperature self-breaking slickwater resistance reducing agent ) 是由 祝纶宇 伊卓 刘希 方昭 胡晓娜 杨金彪 李雅婧 于 2019-10-18 设计创作，主要内容包括：本发明涉及石油工程领域,公开了一种耐盐型低温自破胶滑溜水降阻剂,其中,所述降阻剂包含丙烯酰胺聚合物和氧化剂；所述氧化剂选自双氧水或过氧化甲乙酮；所述丙烯酰胺聚合物由N,N-二甲基丙烯酰胺所提供的结构单元A；基于降阻剂的总重量,所述氧化剂的含量为0.05-1wt％,优选为0.1-0.85wt％。本发明所提供的耐盐型自破胶降阻剂,在具有常规降阻剂的减阻性能的同时,在50～60℃的地层温度下,具有自动均匀破胶的功能。本发明同时具有无油相、无表面活性剂的环保性能,也降低了原材料成本和制备成本。(The invention relates to the field of petroleum engineering and discloses a salt-tolerant low-temperature self-breaking slickwater resistance reducing agent, wherein the resistance reducing agent comprises an acrylamide polymer and an oxidant; the oxidant is selected from hydrogen peroxide or methyl ethyl ketone peroxide; the acrylamide polymer is a structural unit A provided by N, N-dimethylacrylamide; the content of the oxidizer is 0.05 to 1 wt%, preferably 0.1 to 0.85 wt%, based on the total weight of the friction reducer. The salt-tolerant self-gel-breaking resistance reducing agent provided by the invention has the resistance reducing performance of a conventional resistance reducing agent and has the function of automatically and uniformly breaking gel at the formation temperature of 50-60 ℃. The invention has the environmental protection performance of no oil phase and no surfactant, and reduces the cost of raw materials and preparation cost.)

1. A self-breaking friction reducer, wherein the friction reducer comprises an acrylamide polymer and an oxidizer; the oxidant is selected from hydrogen peroxide and/or methyl ethyl ketone peroxide; the acrylamide polymer contains a structural unit A provided by N, N-dimethylacrylamide;

the content of the oxidizer is 0.05-2 wt%, preferably 0.1-0.85 wt%, based on the total weight of the friction reducer.

2. The friction reducer of claim 1 wherein the acrylamide polymer further comprises structural units B;

wherein the structural unit B is provided by at least one of 2-acrylamide-2-dimethylpropanesulfonic acid, 2-acrylamide-2-dimethylpropanesulfonic acid sodium salt, styrene sulfonic acid and styrene sodium sulfonate;

preferably, the content of the structural unit A is 20-100 wt% and the content of the structural unit B is 0-80 wt% based on the total weight of the copolymer;

more preferably, the content of the structural unit a is 60 to 90% by weight and the content of the structural unit B is 10 to 40% by weight, based on the total weight of the copolymer.

3. The resistance reducing agent according to claim 1, wherein the weight average molecular weight of the polymer is 300-1400 ten thousand, preferably 600-1000 ten thousand.

4. A preparation method of a self-gel-breaking friction reducer, wherein the method comprises the following steps:

(1) uniformly mixing a polymerization monomer, a stabilizer, an oxidant, a precipitating agent and water to obtain a clear solution;

(2) in an inert atmosphere, mixing a reducing agent with the clarified solution to perform a first reaction to obtain an emulsion;

(3) and mixing a post-positioned reducing agent with the emulsion to perform a second reaction to obtain the low-temperature self-gel-breaking resistance-reducing agent.

5. The preparation method according to claim 4, wherein the amount of the polymerized monomer is 10-30 wt%, the amount of the stabilizer is 1-1.5 wt%, the amount of the precipitant is 10-35 wt%, the amount of the oxidant is 0.12-0.38 wt%, the amount of the reducing agent is 0.12-0.38 wt%, and the amount of the post-reducing agent is 0.78-2.5 wt%, based on the total weight of the friction reducer;

preferably, based on the total weight of the resistance reducing agent, the dosage of the polymerized monomer is 15-30 wt%, the dosage of the stabilizer is 1.1-1.4 wt%, the dosage of the precipitation agent is 15-25 wt%, the dosage of the oxidizing agent is 0.15-0.5 wt%, the dosage of the reducing agent is 0.15-0.3 wt%, and the dosage of the post-reducing agent is 0.19-0.21 wt%;

more preferably, based on the total weight of the resistance reducing agent, the dosage of the polymerized monomer is 17-20 wt%, the dosage of the stabilizer is 1.2-1.3 wt%, the dosage of the precipitation agent is 17-23 wt%, the dosage of the oxidizing agent is 0.2-0.3 wt%, the dosage of the reducing agent is 0.19-0.21 wt%, and the dosage of the post-reducing agent is 1.5-1.6 wt%;

still more preferably, the amount of said oxidizing agent and reducing agent is such that the ratio between the molar amount of electrons taken up by the oxidizing agent and the molar amount of electrons lost by the reducing agent during said first reaction is greater than 1, preferably in the range of 1.5 to 15: 1.

6. The method of claim 4 or 5, wherein the polymerized monomers comprise N, N-dimethylacrylamide and optionally a salt-tolerant monomer;

preferably, the salt-tolerant monomer is selected from at least one of 2-acrylamide-2-dimethyl propane sulfonic acid, 2-acrylamide-2-dimethyl propane sodium sulfonate, styrene sulfonic acid and styrene sodium sulfonate;

preferably, the stabilizer is selected from at least one of polyvinyl alcohol, polyethylene oxide, poly 2-acrylamide-based 2-dimethylpropanesulfonic acid sodium, cellulose water-soluble derivatives and vegetable gums;

preferably, the precipitation agent is selected from at least one of sodium sulfate, potassium sulfate and ammonium sulfate;

preferably, the oxidizing agent is selected from hydrogen peroxide and/or methyl ethyl ketone peroxide;

preferably, the reducing agent is selected from at least one of sodium thiosulfate, sodium bisulfite, sodium sulfite, and sodium metabisulfite;

preferably, the post-reducing agent is selected from at least one of ethanolamine, diethanolamine, and triethanolamine.

7. The preparation method of claim 6, wherein in the polymerized monomers, the N, N-dimethylacrylamide is used in an amount of 20-100 wt%, and the salt-tolerant monomer is used in an amount of 0-80 wt%;

preferably, the N, N-dimethylacrylamide is used in an amount of 60 to 90 wt% and the salt-tolerant monomer is used in an amount of 10 to 40 wt%, based on the total amount of the polymerized monomers.

8. The production method according to any one of claims 4 to 7, wherein the conditions of the first reaction include: the reaction temperature is 20-35 ℃, preferably 28-31 ℃; the reaction time is 4-24h, preferably 5-7 h;

preferably, the conditions of the second reaction include: the reaction temperature is 20-35 ℃, and the optimized temperature is 22-30 ℃; the reaction time is 5-20min, preferably 10-15 min.

9. The low-temperature self-breaking friction reducer prepared by the preparation method of any one of claims 4 to 8, wherein the friction reducer comprises 0.05 to 2 wt%, preferably 0.1 to 0.85 wt%, of an oxidizing agent, relative to the total weight of the friction reducer.

10. Use of a low temperature self-breaking friction reducer of any one of claims 1-3 and 9 in a water-based fracturing technology, preferably a slickwater fracturing system.

Technical Field

The invention relates to the field of oil exploitation, in particular to an environment-friendly slickwater fracturing resistance reducing agent and a preparation method thereof.

Background

Since the middle of the last century, hydraulic fracturing technology has been the major production increasing technology in oil and gas development at home and abroad. After the new century, the hydraulic fracturing technology is highly regarded as a key technology for unconventional resource development of compact sandstone oil gas, coal bed gas, shale oil gas and the like.

The water-based fracturing technology used in unconventional resource development is primarily a slickwater fracturing fluid system. The slickwater fracturing fluid mainly comprises a resistance reducing agent and other fracturing additives. The slickwater fracturing fluid is high in discharge capacity to press open the stratum, so that longer cracks can be formed; the slippery water adopting the high-concentration resistance reducing agent can partially replace guar gum sand-carrying liquid, and sand carrying and spreading are realized. The resistance reducing agent used in the slickwater fracturing fluid is mainly acrylamide polymer, and the prior art is mainly water-in-oil type inverse emulsion polyacrylamide. Other fracturing additives include cleanup additives to reduce formation sensitivity and promote fluid flowback, clay stabilizers to prevent clay swelling migration, and breakers to hydrate flowback after fracturing.

In normal construction operations, the various additives are in liquid form and can be automatically metered, mixed and pumped using metering pumps. The gel breaker is usually solid particles or powder, and the solid is usually not metered in a construction site under the condition, so that manual addition is required. This increases the complexity, uncertainty of the process and also creates a significant human hazard. In the new drag reducer fracturing application, the drag reducer adopts high-concentration additive to form sand carrying liquid, which puts more severe requirements on the gel breaker.

Disclosure of Invention

The invention aims to solve the problems that the gel breaker cannot be added automatically and accurately and the gel breaking effect is easy to fluctuate in the conventional slickwater fracturing fluid system, and provides a low-temperature self-gel-breaking resistance reducing agent, a preparation method and application thereof.

In order to achieve the above object, a first aspect of the present invention provides a self-breaking friction reducer, wherein the friction reducer comprises an acrylamide polymer and an oxidizer; the oxidant is selected from hydrogen peroxide and/or methyl ethyl ketone peroxide; the acrylamide polymer contains a structural unit A provided by N, N-dimethylacrylamide;

the content of the oxidizer is 0.05-2 wt%, preferably 0.1-0.85 wt%, based on the total weight of the friction reducer.

The second aspect of the present invention provides a method for preparing a self-breaking friction reducer, wherein the method comprises:

(1) uniformly mixing a polymerization monomer, a stabilizer, an oxidant, a precipitating agent and water to obtain a clear solution;

(2) in an inert atmosphere, mixing a reducing agent with the clarified solution to perform a first reaction to obtain an emulsion;

(3) and mixing a post-positioned reducing agent with the emulsion to perform a second reaction to obtain the low-temperature self-gel-breaking resistance-reducing agent.

In a third aspect, the invention provides a low-temperature self-breaking friction reducer prepared by the preparation method of the invention, wherein the friction reducer contains 0.05-2 wt%, preferably 0.1-0.85 wt% of an oxidizing agent relative to the total weight of the friction reducer.

In a fourth aspect, the invention provides an application of the low-temperature self-gel-breaking resistance-reducing agent in a water-based fracturing technology, preferably a slickwater fracturing system.

By the technical scheme, the low-temperature self-gel-breaking resistance-reducing agent, the preparation method and the application thereof provided by the invention have the following beneficial effects:

the resistance reducing agent provided by the invention is a water-in-water type resistance reducing agent, and has the function of automatically and uniformly breaking the gel at the formation temperature of 50-60 ℃ on the premise of keeping the resistance reducing performance of the resistance reducing agent compared with the conventional water-in-oil resistance reducing agent. The resistance reducing agent provided by the invention saves the process link of applying the gel breaker by workers in the fracturing operation field and saves the cost of the gel breaker. The invention has the environmental protection performance of no oil phase and no surfactant, and reduces the cost of raw materials and preparation cost.

The invention adopts a double aqueous phase reaction polymerization system to prepare the resistance reducing agent, and the continuous phase of the resistance reducing agent is an aqueous phase. In the preparation process, the feeding sequence of the oxidant and the reducing agent and the adding rate of the reducing agent are adjusted, so that the gel breaker is added in advance in the preparation process of the resistance reducing agent, and an equal-proportion uniform liquid phase is formed together with the resistance reducing agent. Therefore, accurate metering pumping is realized, slickwater with uniform gel breaker is formed and directly enters the well, and the process cost is reduced.

Drawings

FIG. 1 shows the temperature and shear resistance results of the water-based fracturing fluid of example 1 at 60 ℃;

figure 2 shows the temperature and shear resistance results of the water-based fracturing fluid of example 1 at 50 ℃.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a self-breaking friction reducer in a first aspect, wherein the friction reducer comprises an acrylamide polymer and an oxidant; the oxidant is selected from hydrogen peroxide and/or methyl ethyl ketone peroxide; the acrylamide polymer contains a structural unit A provided by N, N-dimethylacrylamide;

the content of the oxidizer is 0.05-2 wt%, preferably 0.1-0.85 wt%, based on the total weight of the friction reducer.

In the invention, the inventor researches and discovers that when the resistance reducing agent contains 0.05-2 wt% of an oxidant, the oxidant can play a role and an effect of a gel breaker, so that the resistance reducing agent can have an automatic and uniform gel breaking function at the formation temperature of 50-60 ℃, a process link of applying the gel breaker by a fracturing operation field worker is omitted, uniform mixing and metered addition of the gel breaker and the resistance reducing agent can be realized, and the problem of gel breaking effect fluctuation caused by uneven mixing or dosage fluctuation of the gel breaker and the resistance reducing agent is avoided.

Further, in order to further improve the demulsification effect of the friction reducer, the content of the oxidant is preferably 0.1-0.85 wt% relative to the total weight of the friction reducer.

In the present invention, the solid content of the resistance reducing agent is 10 to 30 wt%, preferably 15 to 25 wt%.

According to the invention, the acrylamide polymer also contains structural units B; wherein the structural unit B is provided by at least one of 2-acrylamide-2-dimethylpropanesulfonic acid, 2-acrylamide-2-dimethylpropanesulfonic acid sodium salt, styrene sulfonic acid and styrene sodium sulfonate.

In the invention, the inventor researches and discovers that the acrylamide polymer containing the structural unit A is adopted as the matrix material of the resistance reducing agent, can be quickly dissolved and thickened under high-salinity configuration water, provides resistance reducing performance, and is suitable for configuration and use of reinjection water in a fracturing operation site.

Furthermore, the structural unit B is introduced into a polymer chain of the acrylamide polymer, so that the salt resistance of the resistance reducing agent can be further improved, and the resistance reducing performance of the resistance reducing agent can be still realized under the condition of high salinity configured water.

In order to further improve the automatic demulsification effect of the friction reducer under the conditions of high salinity and low temperature, the inventor researches the content of each structural unit in the copolymer, and finds that when the content of the structural unit A is 20-100 wt% and the content of the structural unit B is 0-80 wt% based on the total weight of the copolymer, the prepared friction reducer is more prone to automatic demulsification under the conditions of low temperature and high salinity.

Furthermore, when the content of the structural unit A is 60-90 wt% and the content of the structural unit B is 10-40 wt% based on the total weight of the copolymer, the provided drag reducer has a more excellent automatic demulsification effect.

According to the present invention, the weight average molecular weight of the copolymer is 300-1400 ten thousand, preferably 600-1000 ten thousand.

According to the invention, the oxidizing agent is chosen from hydrogen peroxide and/or methyl ethyl ketone peroxide.

In the invention, the hydrogen peroxide is preferably hydrogen peroxide with the mass concentration of 30 wt%.

The second aspect of the present invention provides a method for preparing a low-temperature self-gel-breaking friction reducer, wherein the method comprises:

(1) uniformly mixing a polymerization monomer, a stabilizer, an oxidant, a precipitating agent and water to obtain a clear solution;

(2) in an inert atmosphere, mixing a reducing agent with the clarified solution to perform a first reaction to obtain an emulsion;

(3) and mixing a post-positioned reducing agent with the emulsion to perform a second reaction to obtain the low-temperature self-gel-breaking resistance-reducing agent.

In the invention, a double aqueous phase reaction polymerization system is adopted to prepare the resistance reducing agent, and the continuous phase is an aqueous phase. In the preparation process, the feeding sequence of the oxidant and the reducing agent is adjusted, so that the gel breaker is added in advance in the preparation process of the resistance reducing agent, and the gel breaker and the copolymer in the resistance reducing agent form a uniform liquid phase together. Therefore, the accurate metering pumping of the resistance reducing agent is realized, when the resistance reducing agent is used for slickwater, the accurate metering pumping of the resistance reducing agent and a gel breaker can be realized, meanwhile, the provided resistance reducing agent can automatically perform emulsion breaking, and the actual requirement of the fracturing technology is met.

In the invention, in order to ensure the automatic gel breaking capability of the resistance reducing agent at low temperature, a certain amount of post-reducing agent is added into a polymerization system, and the inventor researches and discovers that the post-reducing agent and a residual oxidizing agent of a polymer form a redox initiation system, so that the activation temperature of the oxidizing agent is reduced, and the prepared resistance reducing agent has the low-temperature gel breaking performance.

In order to ensure that the prepared resistance reducing agent can realize the effect of automatic demulsification under the conditions of high-mineralization and low-temperature stratum, when the inventor prepares the resistance reducing agent, the amounts of the components used have been studied and have shown that when based on the total weight of the drag reducer, the dosage of the polymerization monomer is 10-30 wt%, the dosage of the stabilizer is 1-1.5 wt%, the dosage of the precipitating agent is 10 to 35 weight percent, the dosage of the oxidizing agent is 0.12 to 0.38 weight percent, when the dosage of the reducing agent is 0.12 to 0.38 weight percent and the dosage of the post reducing agent is 0.78 to 2.5 weight percent, the prepared resistance reducing agent can maintain the resistance reducing performance of the resistance reducing agent, under the stratum temperature of 50-60 ℃ and the high salinity (30000mg/L), the automatic and uniform gel breaking can be realized, and the fracturing fluid can be further applied to the fracturing technology.

Further, when the dosage of the polymerized monomer is 15-30 wt%, the dosage of the stabilizer is 1.1-1.4 wt%, the dosage of the precipitating agent is 15-25 wt%, the dosage of the oxidizing agent is 0.15-0.5 wt%, the dosage of the reducing agent is 0.15-0.3 wt%, and the dosage of the post reducing agent is 0.19-0.21 wt%, based on the total weight of the resistance reducing agent, the resistance reducing agent with more excellent performance can be obtained.

Furthermore, based on the total weight of the resistance reducing agent, the dosage of the polymerized monomer is 17-20 wt%, the dosage of the stabilizer is 1.2-1.3 wt%, the dosage of the precipitating agent is 17-23 wt%, the dosage of the oxidizing agent is 0.2-0.3 wt%, the dosage of the reducing agent is 0.19-0.21 wt%, and the dosage of the post reducing agent is 1.5-1.6 wt%.

Through a large number of experiments and further researches, the inventor finds that when the amount of the oxidant and the reducing agent is larger than 1 in the first reaction process, the prepared friction reducer has good friction reducing performance, and further, when the amount of the oxidant and the reducing agent is larger than 1 in the first reaction process, the ratio of the molar amount of the electrons obtained by the oxidant to the molar amount of the electrons lost by the reducing agent is 1.5-15:1, the prepared friction reducer has more excellent effect.

In the present invention, the molar amount of electrons obtained by the oxidizing agent refers to the total molar amount of electrons required to be obtained when the oxidizing agent is completely reduced.

The molar amount of electron loss of the reducing agent refers to the total molar amount of electrons that need to be lost when the reducing agent is completely oxidized.

In the invention, the oxidant hydrogen peroxide is completely reduced to form water; the oxidizing agent methyl ethyl ketone peroxide is completely reduced to become methyl ethyl ketone.

According to the invention, the polymerized monomers comprise N, N-dimethylacrylamide and optionally salt-resistant monomers.

According to the invention, the salt-tolerant monomer is selected from at least one of 2-acrylamide-based 2-dimethylpropanesulfonic acid, sodium 2-acrylamide-based 2-dimethylpropanesulfonate and N-vinyl pyrrolidone.

According to the invention, the stabilizer is selected from at least one of polyvinyl alcohol, polyethylene oxide, poly 2-acrylamide-based 2-dimethylpropanesulfonic acid, cellulose water-soluble derivatives and vegetable gums.

In the invention, the weight average molecular weight of the poly 2-acrylamide 2-dimethylpropanesulfonic acid is 30-50 ten thousand.

In the present invention, the vegetable gum can be a vegetable gum commonly used in the prior art, such as guar gum and its derivatives.

According to the invention, the precipitation agent is selected from at least one of sodium sulfate, potassium sulfate and ammonium sulfate.

According to the invention, the oxidizing agent is chosen from hydrogen peroxide and/or methyl ethyl ketone peroxide.

According to the present invention, the reducing agent is selected from at least one of sodium thiosulfate, sodium bisulfite, sodium sulfite, and sodium metabisulfite.

In the present invention, the reducing agent is introduced into the polymerization system in the form of an aqueous solution, and preferably, the reducing agent is a sodium bisulfite solution having a mass concentration of 10 to 16% by weight, the reducing agent is a sodium thiosulfate solution having a mass concentration of 15% by weight, the reducing agent is a sodium metabisulfite solution having a mass concentration of 20% by weight, and the reducing agent is sodium sulfite having a mass concentration of 16 to 20% by weight.

According to the invention, the post-reducing agent is selected from at least one of ethanolamine, diethanolamine and triethanolamine.

According to the invention, in the polymerized monomers, the N, N-dimethylacrylamide is used in an amount of 20-100 wt%, and the salt-resistant monomer is used in an amount of 0-80 wt%.

According to the invention, the N, N-dimethylacrylamide is used in an amount of 60-90 wt% and the salt-tolerant monomer is used in an amount of 10-40 wt%, based on the total amount of the polymerized monomers.

According to the invention, the conditions of the first reaction comprise: the reaction temperature is 20-35 ℃, preferably 28-31 ℃; the reaction time is 4-24h, preferably 5-7 h.

According to the invention, the conditions of the second reaction comprise: the reaction temperature is 20-35 ℃, and the optimized temperature is 22-30 ℃; the reaction time is 5-20min, preferably 10-15 min.

In a third aspect, the invention provides a low-temperature self-breaking friction reducer prepared by the preparation method of the invention, wherein the friction reducer contains 0.05-2 wt%, preferably 0.1-0.85 wt% of an oxidizing agent relative to the total weight of the friction reducer.

In a fourth aspect, the invention provides an application of the low-temperature self-gel-breaking resistance-reducing agent in a water-based fracturing technology, preferably a slickwater fracturing system.

The present invention will be described in detail below by way of examples.

The content of the oxidant in the resistance reducing agent is calculated by the content of the residual oxidant after the oxidant is consumed by the reducing agent according to the amount of the substances in the preparation process;

the resistance reducing performance of the resistance reducing agent adopts a friction resistance tester, and the obtained resistance reducing agent product is tested under the discharge capacity of 30L/min;

the viscosity of the glue solution and the viscosity of the gel breaking solution of the slickwater are measured by a rheometer at the temperature of 60 ℃ and the shear rate of 170S^-1Carrying out the test;

water-in-oil drag reducing agent available from Shandong Baomo Moscow Co., Ltd;

other raw materials used in this example and comparative example were all commercially available.

Example 1

At room temperature, 5g of 1788 type polyvinyl alcohol, 224.07g of deionized water, 58g of N, N-dimethylacrylamide, 18g of 2-acrylamide-2-dimethylpropanesulfonate and 3.58g of 30 wt% hydrogen peroxide are added into a 500ml three-neck flask, and after uniform dissolution, 80g of ammonium sulfate is added and fully dissolved to form a clear solution. Nitrogen was passed through for 20 minutes with stirring. Under the protection of nitrogen, 5g of 16 wt% sodium bisulfite solution is uniformly added within 6 hours at the temperature of 30 ℃, and the molar ratio of electrons obtained by an oxidant to electron loss of a reducer is 4.1: 1. the system gradually whitens within that 6 hours, forming a white emulsion. 6.35g of diethanolamine is added, and the mixture is stirred for 15 minutes at room temperature to obtain a resistance reducing agent A1, and tests show that the content of an oxidant in the resistance reducing agent A1 is 0.2 wt%, the solid content is 19 wt%, the content of an N, N-dimethylacrylamide structural unit in an acrylamide polymer is 76 wt%, and the content of a structural monomer B is 24 wt%.

Example 2

At room temperature, in a 500ml three-neck flask, 4g of polyethylene oxide with a molecular weight of 30 ten thousand, 231.1g of deionized water, 58g of N, N-dimethylacrylamide, 18g of 2-acrylamido-2-dimethylpropanesulfonic acid, and 0.7g of methyl ethyl ketone peroxide were added, and after uniform dissolution, 80g of ammonium sulfate was added and sufficiently dissolved to form a clear solution. Nitrogen was passed through for 20 minutes with stirring. Under the protection of nitrogen, 5g of 10 wt% sodium bisulfite solution is uniformly added within 6 hours at the temperature of 30 ℃, and the molar ratio of electrons obtained by an oxidant to electron loss of a reducer is 2.1: 1. The system gradually whitens within that 6 hours, forming a white emulsion. 1.2g of monoethanolamine and 2g of diethanolamine are added, and the mixture is stirred for 15 minutes at room temperature to obtain a resistance reducing agent A2, and tests show that the content of an oxidant in the resistance reducing agent A2 is 0.09 wt%, the solid content is 19 wt%, the content of an N, N-dimethylacrylamide structural unit in an acrylamide polymer is 76 wt%, and the content of a structural monomer B is 24 wt%.

Example 3

At room temperature, 5.5g of carboxymethyl cellulose, 199.35g of deionized water, 75g of N, N-dimethylacrylamide, 25g of 2-acrylamido-2-dimethylpropanesulfonate, 1.8g of 30 wt% hydrogen peroxide and 0.2g of methyl ethyl ketone peroxide are added into a 500ml three-neck flask, and after uniform dissolution, 60g of ammonium sulfate and 20g of sodium sulfate are added and fully dissolved to form a clear solution. Nitrogen was passed through for 20 minutes with stirring. Under the protection of nitrogen, 10g of 15 wt% sodium thiosulfate solution is uniformly added within 10 hours at the temperature of 30 ℃, and the molar ratio of electrons obtained by an oxidant to electron loss of a reducing agent is 1.975: 1. The system gradually whitens within that 6 hours, forming a white emulsion. 1.15g of monoethanolamine and 2g of triethanolamine are added and stirred for 15 minutes at room temperature to obtain a resistance reducing agent A3, and tests show that the content of an oxidant in the resistance reducing agent A3 is 0.09 wt%, the solid content is 25 wt%, the content of an N, N-dimethylacrylamide structural unit in an acrylamide polymer is 75 wt%, and the content of a structural monomer B is 25 wt%.

Example 4

At room temperature, 5g of poly 2-acrylamide-based 2-dimethylpropanesulfonic acid sodium salt with the molecular weight of 50 ten thousand, 251.35g of deionized water, 40g of N, N-dimethylacrylamide and 9.65g of 30 wt% hydrogen peroxide are added into a 500ml three-neck flask, and after uniform dissolution, 40g of ammonium sulfate, 20g of potassium sulfate and 20g of sodium sulfate are added and fully dissolved to form a clear solution. Nitrogen was passed through for 20 minutes with stirring. Under the protection of nitrogen, 5g of 16% sodium sulfite solution is uniformly added within 6 hours under the condition of 30 ℃, and the molar ratio of electrons obtained by an oxidant to electron loss of a reducing agent is 13.4: 1. The system gradually whitens within that 6 hours, forming a white emulsion. And 5g of diethanolamine and 4g of triethanolamine are added, stirring is carried out at room temperature for 15 minutes to obtain the resistance reducing agent A4, and tests show that the content of the oxidant in the resistance reducing agent A4 is 0.67 wt%, the solid content is 10 wt%, the content of the N, N-dimethylacrylamide structural unit in the acrylamide polymer is 100 wt%, and the content of the structural monomer B is 0 wt%.

Example 5

At room temperature, 6g of poly 2-acrylamide-based 2-dimethylpropanesulfonic acid with the molecular weight of 50 ten thousand, 236.86g of deionized water, 12g of N, N-dimethylacrylamide, 20g of sodium styrene sulfonate, 28g of 2-acrylamide-based 2-dimethylpropanesulfonic acid and 2.14g of methyl ethyl ketone peroxide are added into a 500ml three-neck flask, and after uniform dissolution, 80g of ammonium sulfate is added and fully dissolved to form a clear solution. Nitrogen was passed through for 20 minutes with stirring. Under the protection of nitrogen, under the condition of 30 ℃, 5g of 20 wt% sodium metabisulfite solution is uniformly added within 12 hours, and the molar ratio of electrons obtained by an oxidant to electron loss of a reducing agent is 5.8: 1. The system gradually whitens within that 6 hours, forming a white emulsion. And adding 10g of diethanol amine, and stirring at room temperature for 15 minutes to obtain a resistance reducing agent A5, wherein the resistance reducing agent A5 is tested to contain 0.44 wt% of an oxidant and 15 wt% of solid content, and in an acrylamide polymer, the content of an N, N-dimethylacrylamide structural unit is 20 wt% and the content of a structural monomer B is 80 wt%.

Comparative example 1

Referring to the method of example 1, the resistance reducing agent D1 was prepared, except that the oxidizing agent was potassium persulfate, the dosage was 0.4g, the molar ratio of electrons obtained by the oxidizing agent to electron lost by the reducing agent was 0.2:1, and the resistance reducing agent D1 was prepared without adding a post-reducing agent, and it was tested that the content of the oxidizing agent in the resistance reducing agent D1 was 0 wt%.

Comparative example 2

A conventional water-in-oil friction reducer D3 sold on the market, a monomer mass ratio, acrylamide: the ratio of 2-acrylamide 2-dimethylpropanesulfonic acid to 2-acrylamide 2-dimethylpropanesulfonic acid is 3:1, the solid content is 30 wt%, and the molecular weight is 800 ten thousand.

Test example 1

The slick water is prepared by adopting 30000mg/L mineralization degree simulation water and 0.1 volume percent of addition amount. The resistance reducing performance of the example and the comparative resistance reducing agent were tested, and the results are shown in table 1.

TABLE 1

	0.1% resistance reduction (%)
		A1	65.1
A2	64.5
		A3	69.6
A4	53.4
		A5	62.6
D1	64.3
		D2	66.5

Test example 2

The rheological viscosity performance of the drag reducer of the examples and comparative examples was tested using 30000mg/L mineralization simulated water, 1.2 volume percent addition formulated into high viscosity slickwater, and the results are shown in Table 2.

TABLE 2

	1.2 v% gum viscosity @25 ℃ (mPa.s)	1.2 v% gel breaker viscosity @60 ℃ (mPa.s)
			A1	58.89	1.35
A2	56.98	3.31
			A3	64.42	2.39
A4	52.16	0.76
			A5	58.29	1.13
D1	58.80	54.05
			D2	57.32	54.35

A graph of the rheological test data for example 1 and comparative example 1 is shown at @60 deg.C in FIG. 1 and at @50 deg.C in FIG. 2.

As can be seen from Table 1, the drag reducer provided by the invention has a drag reduction rate of over 50% under the conventional discharge capacity test, and excessive addition of the oxidant has no obvious influence on the performance of the drag reducer. As can be seen from fig. 1, fig. 2 and table 2, the conventional slickwater system cannot break gel without adding a gel breaker; the slippery water prepared by the resistance reducing agent provided by the invention can automatically break gel within 180 minutes at 55 +/-5 ℃ without adding a gel breaker, and the gel is broken thoroughly.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.