阅读说明：本技术 环保型高温自破胶降阻剂及其制备方法与应用 (Environment-friendly high-temperature self-gel-breaking resistance-reducing agent and preparation method and application thereof ) 是由 祝纶宇 伊卓 刘希 方昭 胡晓娜 李雅婧 杨金彪 于 2019-10-21 设计创作，主要内容包括：本发明涉及石油工程领域,公开了一种环保型高温自破胶降阻剂,其中,所述降阻剂包含丙烯酰胺共聚物和氧化剂；所述氧化剂选自氯酸盐；所述共聚物由丙烯酰胺所提供的结构单元A；基于所述降阻剂的总重量,所述氧化剂的含量为0.1-1wt％,优选为0.15-0.35wt％。本发明所提供的环保型高温自破胶降阻剂,在具有常规降阻剂的减阻性能的同时,在120℃以上的地层温度下,具有自动均匀破胶的功能。本发明同时具有无油相、无表活剂的环保性能,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 an environment-friendly high-temperature self-breaking resistance reducing agent, wherein the resistance reducing agent comprises an acrylamide copolymer and an oxidant; the oxidant is selected from chlorate; structural unit A provided by acrylamide of the copolymer; the content of the oxidizer is 0.1-1 wt%, preferably 0.15-0.35 wt%, based on the total weight of the friction reducer. The environment-friendly high-temperature self-breaking gel-reducing resistance agent provided by the invention has the resistance-reducing performance of the conventional resistance agent and has the function of automatically and uniformly breaking gel at the formation temperature of more than 120 ℃. 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. An environment-friendly high-temperature self-gel-breaking resistance-reducing agent, wherein the resistance-reducing agent comprises an acrylamide copolymer and an oxidant; the oxidant is selected from chlorate; the copolymer contains a structural unit A provided by acrylamide and a structural unit B provided by a carboxylic acid monomer;

the content of the oxidizer is 0.1-1 wt%, preferably 0.15-0.35 wt%, based on the total weight of the friction reducer.

2. The friction reducer according to claim 1, wherein the content of the structural unit a is 40-80 wt%, and the content of the structural unit B is 60-20 wt%, based on the total weight of the copolymer;

preferably, the content of the structural unit A is 60 to 75 wt% and the content of the structural unit B is 25 to 40 wt% based on the total weight of the copolymer;

preferably, the carboxylic acid monomer is selected from at least one of acrylic acid, sodium acrylate, methacrylic acid and sodium methacrylate.

3. The resistance reducer according to claim 1 or 2, wherein the weight average molecular weight of the copolymer is 300-1400 ten thousand, preferably 600-1000 ten thousand;

the oxidant is sodium chlorate and/or potassium chlorate.

4. A preparation method of an environment-friendly high-temperature self-gel-breaking resistance-reducing agent 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) and mixing a reducing agent with the clarified solution in an inert atmosphere to perform a polymerization reaction to obtain the environment-friendly high-temperature self-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 0.5-1.5 wt%, the amount of the precipitation agent is 10-25 wt%, the amount of the oxidant is 0.1-0.35 wt%, and the amount of the reducing agent is 0.12-0.45 wt%, based on the total weight of the resistance reducing agent;

preferably, based on the total weight of the resistance reducing agent, the dosage of the polymerized monomer is 15-25 wt%, the dosage of the stabilizer is 1-1.4 wt%, the dosage of the precipitation agent is 15-20 wt%, the dosage of the oxidizing agent is 0.15-0.3 wt%, and the dosage of the reducing agent is 0.15-0.4 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 17-19 wt%, the dosage of the oxidizing agent is 0.18-0.25 wt%, and the dosage of the reducing agent is 0.19-0.21 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 8: 1.

6. The production method according to claim 4 or 5, wherein the polymerized monomers include acrylamide and carboxylic acid monomers;

preferably, the carboxylic acid monomer is selected from at least one selected from the group consisting of acrylic acid, sodium acrylate, methacrylic acid and sodium methacrylate;

preferably, the stabilizer is selected from at least one of sodium poly-2-acrylamido-2-dimethylpropanesulfonate, a water-soluble derivative of cellulose and a vegetable gum;

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 sodium chlorate and/or potassium chlorate;

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

7. The method according to claim 6, wherein the weight ratio of the acrylamide to the carboxylic acid monomer in the polymerized monomers is 40-80:60-20, preferably 60-75: 25-40.

8. The production method according to any one of claims 4 to 7, wherein the conditions for the polymer reaction include: the reaction temperature is 25-40 ℃, and preferably 28-35 ℃; the reaction time is 4-24h, preferably 5-7 h.

9. The environment-friendly high-temperature self-breaking friction reducer prepared by the preparation method of any one of claims 4 to 8, wherein the friction reducer comprises 0.1 to 1 wt%, preferably 0.15 to 0.35 wt%, of an oxidant based on the total weight of the friction reducer.

10. Use of the environmentally friendly high temperature self-breaking friction reducer of any one of claims 1-3 and 9 in water-based fracturing technology, preferably slickwater fracturing systems.

Technical Field

The invention relates to the field of oil exploitation, in particular to an environment-friendly high-temperature self-gel-breaking resistance-reducing agent and a preparation method and application 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 an environment-friendly high-temperature self-gel-breaking resistance reducing agent, a preparation method and application thereof.

In order to achieve the above object, the present invention provides, in a first aspect, an environment-friendly high-temperature self-breaking friction reducer, wherein the friction reducer comprises an acrylamide copolymer and an oxidant; the oxidant is selected from chlorate; the copolymer contains a structural unit A provided by acrylamide and a structural unit B provided by a carboxylic acid monomer;

the content of the oxidizer is 0.1-1 wt%, preferably 0.15-0.35 wt%, based on the total weight of the friction reducer.

The second aspect of the invention provides a preparation method of an environment-friendly high-temperature self-gel-breaking resistance-reducing agent, 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) and mixing a reducing agent with the clarified solution in an inert atmosphere to perform a polymerization reaction to obtain the environment-friendly high-temperature self-breaking resistance-reducing agent.

The third aspect of the invention provides an environment-friendly high-temperature self-breaking resistance-reducing agent prepared by the preparation method.

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

By the technical scheme, the environment-friendly high-temperature self-breaking resistance-reducing agent and the preparation method and 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 under the high-temperature stratum of more than 120 ℃ 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 required by applying 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 120 ℃.

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 an environment-friendly high-temperature self-gel-breaking resistance reducer, wherein the resistance reducer comprises an acrylamide copolymer and an oxidant; the oxidant is selected from chlorate; the copolymer contains a structural unit A provided by acrylamide and a structural unit B provided by a carboxylic acid monomer;

the content of the oxidizer is 0.1-1 wt%, preferably 0.15-0.35 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 0.1-1 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 under the high-temperature formation condition of more than 120 ℃, 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 gel breaking effect of the friction reducer, the content of the oxidant is preferably 0.15-0.35 wt% relative to the total weight of the friction reducer.

In the invention, the inventor researches and discovers that the acrylamide copolymer containing the structural unit A and the structural unit B is used as the matrix material of the resistance reducing agent, so that the resistance reducing performance and the uniform gel breaking performance under high-temperature formation conditions of the resistance reducing agent can be further improved, the gel breaking time is proper, and the resistance reducing agent is suitable for configuration and use of a fracturing operation site.

Specifically, due to the introduction of the structural unit B, the prepared resistance reducing agent has larger hydrodynamic volume occupation, so that the resistance reducing effect can be generated at a lower addition amount. Meanwhile, the structure of B is similar to that of A, so that the chain lock degradation of the polymer can continuously occur in the gel breaking process.

In order to further improve the automatic gel breaking effect of the resistance reducing agent under the high-temperature condition, the inventor researches the content of each structural unit in the copolymer, and finds that when the content of the structural unit A is 40-80 wt% and the content of the structural unit B is 60-20 wt% based on the total weight of the copolymer, the prepared resistance reducing agent is more prone to automatic gel breaking under the high-temperature condition.

Furthermore, when the content of the structural unit A is 60-75 wt% and the content of the structural unit B is 25-40 wt% based on the total weight of the copolymer, the provided friction reducer has a more excellent automatic gel breaking effect.

According to the present invention, the carboxylic acid monomer is selected from at least one of acrylic acid, sodium acrylate, methacrylic acid and sodium methacrylate.

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 sodium chlorate and/or potassium chlorate.

The second aspect of the invention provides a preparation method of an environment-friendly high-temperature self-gel-breaking resistance-reducing agent, 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) and mixing a reducing agent with the clarified solution in an inert atmosphere to perform a polymerization reaction to obtain the environment-friendly high-temperature self-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 the gel breaker can be realized, meanwhile, the provided resistance reducing agent can automatically break gel, and the actual requirement of the fracturing technology is met.

In order to ensure that the prepared friction reducer can realize the effect of automatic gel breaking under the condition of a high-temperature stratum, the inventor researches the use amount of each component in the preparation of the friction reducer, and the research shows that when the total weight of the friction reducer is taken as a reference, the use amount of the polymerization monomer is 10-30 wt%, the use amount of the stabilizer is 0.5-1.5 wt%, the use amount of the precipitant is 10-25 wt%, the use amount of the oxidant is 0.1-0.35 wt%, and the use amount of the reducing agent is 0.12-0.45 wt%, the prepared friction reducer can realize automatic and uniform gel breaking under the condition of the high-temperature stratum on the premise of keeping the resistance reducing performance of the friction reducer, and further can be applied to the fracturing technology.

Further, when the dosage of the polymerized monomer is 15-25 wt%, the dosage of the stabilizer is 1.0-1.4 wt%, the dosage of the precipitating agent is 15-20 wt%, the dosage of the oxidizing agent is 0.15-0.3 wt%, and the dosage of the reducing agent is 0.15-0.4 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 precipitation agent is 17-19 wt%, the dosage of the oxidizing agent is 0.18-0.25 wt%, and the dosage of the reducing agent is 0.19-0.21 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 1.5-8:1, 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 sodium chlorate becomes NaCl after being completely reduced; the potassium chlorate becomes KCl after being completely reduced.

According to the present invention, the polymerized monomers include acrylamide and carboxylic acid monomers.

According to the present invention, the carboxylic acid monomer is selected from at least one selected from the group consisting of acrylic acid, sodium acrylate, methacrylic acid and sodium methacrylate.

According to the invention, the stabilizer is selected from at least one of sodium poly-2-acrylamido-2-dimethylpropanesulfonate, a water-soluble derivative of cellulose and a vegetable gum.

In the invention, the weight average molecular weight of the poly-2-acrylamide-2-dimethylpropanesulfonic acid sodium 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 selected from sodium chlorate and/or potassium chlorate.

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

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 16% by weight, the reducing agent is a sodium dithionite solution having a mass concentration of 16% by weight, and the reducing agent is a sodium sulfite solution having a mass concentration of 16% by weight.

According to the invention, the ratio of acrylamide to carboxylic acid monomer in the polymerized monomers is 40-80: 60-20.

In the invention, the inventor researches and discovers that when the ratio of acrylamide to carboxylic acid monomers in the polymerized monomers meets the requirement in the preparation of the resistance reducing agent, the prepared resistance reducing agent has more excellent resistance reducing performance under the condition of high-temperature stratum.

Further, in the polymerized monomers, the ratio of acrylamide to carboxylic acid monomer is preferably 60-75: 25-40.

According to the invention, the polymerization conditions comprise: the reaction temperature is 25-40 ℃, and preferably 28-35 ℃; the reaction time is 4-24h, preferably 5-7 h.

The third aspect of the invention provides an environment-friendly high-temperature self-breaking friction reducer prepared by the preparation method of the invention, wherein the friction reducer contains 0.1-1 wt%, preferably 0.15-0.35 wt% of an oxidant based on the total weight of the friction reducer.

The fourth aspect of the invention provides an application of the environment-friendly high-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;

the other raw materials used in the examples and comparative examples of the present invention are all commercially available products

Example 1

At room temperature, 5g of poly 2-acrylamide-2-dimethylpropanesulfonate with the molecular weight of 50 ten thousand, 235g of deionized water, 50g of acrylamide, 24g of acrylic acid and 1g of potassium chlorate 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 3.2: 1. the system gradually whitens within 10 hours to form a white emulsion resistance reducer A1, and tests show that the resistance reducer A1 contains 0.22 wt% of an oxidizing agent and 18.5 wt% of solid content, and the acrylamide copolymer contains 68 wt% of an acrylamide structural unit and 32 wt% of a structural monomer B.

Example 2

At room temperature, 5g of poly 2-acrylamide-2-dimethylpropanesulfonate with the molecular weight of 50 ten thousand, 232.1g of deionized water, 55g of acrylamide, 22g of methacrylic acid and 0.9g of potassium chlorate 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% 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 2.9: 1. the system gradually whitens within 10 hours to form a white emulsion resistance reducer A2, and tests show that the resistance reducer A2 contains 0.19 wt% of an oxidizing agent and 19.25 wt% of solid content, and the acrylamide copolymer contains 71 wt% of acrylamide structural units and 29 wt% of structural monomer B.

Example 3

6g of carboxymethyl cellulose, 268g of deionized water, 24g of acrylamide, 16g of acrylic acid and 1g of sodium chlorate are added into a 500ml three-neck flask at room temperature, 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, 5g of 16 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 5.6: 1. the system gradually whitens within 10 hours to form a white emulsion resistance reducer A3, and tests show that the resistance reducer A3 contains 0.23 wt% of oxidant and 10 wt% of solid content, and the acrylamide copolymer contains 60 wt% of acrylamide structural units and 40 wt% of structural monomer B.

Example 4

At room temperature, in a 500ml three-neck flask, low-viscosity polyanionic cellulose PAC-LV5g, 208.9g of deionized water, 40g of acrylamide, 20g of methacrylic acid, 40g of acrylic acid, 0.6g of sodium chlorate and 0.5g of potassium chlorate are added, 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 wt% sodium sulfite 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 reducing agent is 4.6: 1. the system gradually whitens within 10 hours to form a white emulsion resistance reducer A4, and tests show that the resistance reducer A4 contains 0.25 wt% of oxidant and 25 wt% of solid content, and the acrylamide copolymer contains 40 wt% of acrylamide structural units and 60 wt% of structural monomer B.

Example 5

2g of carboxymethyl hydroxypropyl guar gum, 229.2g of deionized water, 60g of acrylamide, 18g of sodium acrylate and 0.8g of sodium chlorate are added into a 500ml three-neck flask at room temperature, and after uniform dissolution, 45g of ammonium sulfate and 35g 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, under the condition of 30 ℃, uniformly adding 10g of 16 percent sodium hydrosulfite solution in 12 hours, wherein the molar ratio of electrons obtained by an oxidant to electron loss of a reducer is 2.5: 1. the system gradually whitens within 10 hours to form a white emulsion resistance reducer A5, and tests show that the resistance reducer A5 contains 0.16 wt% of an oxidizing agent and 19.5 wt% of solid content, and that the acrylamide copolymer contains 77 wt% of acrylamide structural units and 23 wt% of structural monomer B.

Example 6

Drag reducer a6 was prepared with reference to example 1, except that 1.5g of potassium chlorate was added and the molar ratio of electrons lost from the oxidizer to the reducer was 4.8: 1. the test shows that the resistance reducer A6 contains 0.34 wt% of oxidant and 18.5 wt% of solid content, and in the acrylamide copolymer, 68 wt% of acrylamide structural unit and 32 wt% of structural monomer B.

Comparative example 1

Reference is made to example 1 for the preparation of friction reducer D1, except that the oxidizing agent was potassium persulfate in an amount of 0.4g and the molar ratio of electrons obtained by the oxidizing agent to lost electrons of the reducing agent was less than 1. Through tests, the resistance reducer D1 has an oxidant content of 0 wt% and a solid content of 18.5 wt%, and in the acrylamide copolymer, the acrylamide structural unit content is 68 wt% and the structural monomer B content is 32 wt%.

Comparative example 2

A conventional water-in-oil friction reducer D3 sold on the market, a monomer mass ratio, acrylamide: acrylic acid is 3:1, solid content is 25%, and molecular weight is 800 ten thousand.

Test example 1

The slickwater was prepared with tap water in an amount of 0.1% by volume. 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	64.9
A2	66.7
		A3	57.6
A4	69.0
		A5	61.7
A6	64.5
		D1	65.9
D2	72.5

Test example 2

The rheological viscosity properties of the example and comparative drag reducing agents were tested using tap water formulated into high viscosity slickwater at 1.5 volume percent addition and the results are shown in table 2.

TABLE 2

The rheological test data for example 1 and comparative example 1 are shown in the graph of FIG. [email protected] ℃.

As can be seen from Table 1, the prepared drag reduction rate exceeds 50% under the conventional discharge capacity test, and the excessive addition of the oxidant has no obvious influence on the performance of the drag reduction agent. As can be seen from fig. 1 and table 2, the conventional slickwater system cannot break gel without adding a gel breaker; the slickwater prepared by the method can automatically break gel within 120 minutes at 120 ℃ without adding a gel breaker, and the gel is thoroughly broken.

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.