Polymer as well as preparation method, composition and application thereof

Abstract

The invention relates to the field of preparation and application of a fracturing drag reducer for improving and increasing yield of a low-permeability oil and gas reservoir, and discloses a polymer as well as a preparation method, a composition and application thereof. The polymer comprises structural units as shown in formulas 1-4, wherein R1 is selected from substituted or unsubstituted C12-C20 alkyl groups; r2, R3 and R3'are respectively and independently selected from substituted or unsubstituted C1-C4 alkyl groups; x is a positive integer selected from 6-14; wherein the weight ratio of the structural unit as shown in the formula 1 to the structural unit as shown in the formula 2 to the structural unit as shown in the formula 3 to the structural unit as shown in the formula 4 is 1: (2.6-74): (0.5-17): (1.6-42), and the viscosity average molecular weight of the polymer is 4,000,000-10,000,000 Daltons. The drag reducer containing the polymer has the characteristics of high drag reduction rate, good temperature resistance and salt resistance and high dissolution speed; # imgabs0 #

Description

Technical Field

[0001] The invention relates to the preparation and application field of a fracturing drag reducer for low permeability oil and gas reservoir reservoir transformation and production increase, and in particular to a polymer and a preparation method and composition thereof and application thereof. Background Art

[0002] In recent years, some achievements have been made in the research of emulsion-type fracturing drag reducers at home and abroad. CN113684016A discloses a super salt-resistant suspended slick water drag reducer and its preparation method, which solves the problems of on-site rapid liquid preparation and real-time viscosity change required by the slick water system, and realizes the direct liquid preparation using high-mineralization formation water or return fluid to achieve the purpose of saving fresh water resources and environmental protection, while reducing the amount of polymer drag reducers and additives.

[0003] The drag reducer (microemulsion polymer) of slippery water fracturing fluid disclosed in CN103013488B has the characteristics of good stability, fast dissolution rate, convenient use, and significant drag reduction effect. It is suitable for slippery water fracturing technology and has been applied to field fracturing operations, achieving good production increase effects. The patent confirms the feasibility and significant effect of reverse microemulsion polymer as a drag reducer for fracturing fluid, but does not further propose its possibility as a high-viscosity sand-carrying fracturing fluid. Patent application CN202011058758.2 discloses a polymer suspension emulsion for fracturing fluid and a preparation method. The thickener powder is suspended in mineral oil by a certain method to obtain a suspension emulsion, and the solubility, stability, sand-carrying and drag reduction performance of the liquid are tested. Although it shows good performance at room temperature and low mineralization (33,000 ppm), its temperature resistance, high-temperature sand suspension performance, field implementation method and field application are not disclosed, showing that the main performance is not outstanding, the function is single, and the field operability needs to be solved.

[0004] In summary, the existing emulsion thickeners have advantages in terms of effective content, liquid cost, long-term stability, comprehensive performance, damage to formations, and on-site construction control, but also have many disadvantages. For example, the viscosity of high molecular weight emulsion fracturing thickeners is slow to release. Although there are many reports on on-site construction, most of them are completed in the form of integrated fracturing, and the performance of the fracturing fluid is greatly reduced, which needs further improvement and optimization. Therefore, a polymer and its preparation method, composition and application are needed. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of slow dissolution rate and low drag reduction rate of high molecular weight fracturing drag reducer materials in the prior art and weak salt resistance of low molecular weight polymers, and to provide a polymer and its preparation method, composition and application.

[0006] To achieve the above object, on the one hand, the present invention provides a polymer, characterized in that the polymer comprises structural units represented by Formula 1-4:

[0007]

[0008] Wherein, R1 is selected from substituted or unsubstituted C 12 -C 20 alkyl;

[0009] R2, R3 and R3’ are each independently selected from substituted or unsubstituted C1-C4 alkyl;

[0010] X is selected from positive integers of 6-14;

[0011] Wherein, the weight ratio of the structural unit represented by Formula 1, the structural unit represented by Formula 2, the structural unit represented by Formula 3 and the structural unit represented by Formula 4 is 1: 2.6-74: 0.5-17: 1.6-42, and the viscosity-average molecular weight of the polymer is 4 million - 10 million Daltons.

[0012] On the second aspect, the present invention provides a method for preparing a polymer, characterized in that the method comprises: contacting monomers represented by Formula I-IV and carrying out a polymerization reaction to obtain the polymer, wherein the weight ratio of the monomer represented by Formula I, the monomer represented by Formula II, the monomer represented by Formula III and the monomer represented by Formula IV is 1: 2.6-74: 0.5-17: 1.6-42;

[0013]

[0014] Wherein, the definitions of R1, R2, R3, R3’ and X are the same as those defined in the first aspect of the present invention.

[0015] On the third aspect, the present invention provides a polymer prepared by the method described in the second aspect of the present invention.

[0016] On the fourth aspect, the present invention provides a composition, characterized in that the composition comprises a polymer and an auxiliary agent, wherein the definition of the polymer is the same as that defined in the first aspect and / or the third aspect of the present invention.

[0017] On the fifth aspect, the present invention provides the use of the polymer described in the first aspect and the third aspect of the present invention and / or the composition described in the fourth aspect of the present invention in a drag reducer.

[0018] Through the above technical solutions, the present invention prepares a medium molecular weight polymer that can be used as a drag reducer. The raw material uses a long hydrophobic chain-based polyoxyethylene ether methacrylate monomer, preferably n-octadecyl polyoxyethylene ether methacrylate. The drag reducer added with the polymer and / or composition of the present invention has the characteristic of high drag reduction rate. Detailed implementation manners

[0019] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0020] As described above, on the one hand, the present invention provides a polymer, characterized in that the polymer comprises structural units shown in Formula 1-4:

[0021]

[0022] Wherein, R1 is selected from substituted or unsubstituted C 12 -C 20 alkyl;

[0023] R2, R3 and R3' are each independently selected from substituted or unsubstituted C1-C4 alkyl;

[0024] X is selected from positive integers of 6-14;

[0025] Wherein, the weight ratio of the structural unit shown in Formula 1, the structural unit shown in Formula 2, the structural unit shown in Formula 3 and the structural unit shown in Formula 4 is 1:2.6-74:0.5-17:1.6-42, and the viscosity-average molecular weight of the polymer is 4 million - 10 million Daltons. In some embodiments of the present invention, preferably, R1 is selected from unsubstituted C 12 -C 20 alkyl.

[0026] In some embodiments of the present invention, preferably, R2, R3 and R3' are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl or isobutyl.

[0027] In some embodiments of the present invention, preferably, X is selected from positive integers of 7-13.

[0028] In some embodiments of the present invention, preferably, the weight ratio of the structural unit shown in Formula 1, the structural unit shown in Formula 2, the structural unit shown in Formula 3 and the structural unit shown in Formula 4 is 1:4.3-57:1.9-13.4:3.2-35.3. This weight ratio range can make the polymer achieve the effect of maximizing the drag reduction rate in the composition.

[0029] In some embodiments of the present invention, preferably, the viscosity-average molecular weight of the polymer is 5 million to 8 million Daltons. This viscosity-average molecular weight range can maximize the drag reduction rate of the polymer in the composition.

[0030] In some embodiments of the present invention, preferably, R1 is selected from unsubstituted C 16 -C 20 alkyl groups.

[0031] In some embodiments of the present invention, preferably, R2, R3 and R3’ are each independently selected from methyl or ethyl.

[0032] In some embodiments of the present invention, preferably, X is selected from positive integers from 8 to 12.

[0033] In some embodiments of the present invention, preferably, R1 is n-octadecyl. This group can maximize the drag reduction rate of the polymer in the composition.

[0034] In some embodiments of the present invention, preferably, R2, R3 and R3’ are all methyl.

[0035] In some embodiments of the present invention, preferably, X is selected from positive integers from 10 to 12.

[0036] The second aspect of the present invention provides a method for preparing a polymer, which is characterized in that the method includes: contacting the monomers shown in Formulas I-IV and carrying out a polymerization reaction to obtain the polymer, wherein the weight ratio of the monomer shown in Formula I, the monomer shown in Formula II, the monomer shown in Formula III and the monomer shown in Formula IV is 1:2.6-74:0.5-17:1.6-42;

[0037]

[0038] wherein, the definitions of R1, R2, R3, R3’ and X are the same as those defined in the first aspect of the present invention.

[0039] In some embodiments of the present invention, preferably, the weight ratio of the monomer shown in Formula I, the monomer shown in Formula II, the monomer shown in Formula III and the monomer shown in Formula IV is 1:8.2-47:2.3-13:6.7-35.

[0040] In some embodiments of the present invention, preferably, at least one of a molecular weight regulator, an acid-base neutralizer, a stabilizer and an initiator is added in the polymerization reaction.

[0041] In some embodiments of the present invention, preferably, the molecular weight regulator is selected from at least one of dodecyl mercaptan, tetradecyl mercaptan and diisopropyl xanthogen disulfide.

[0042] In some embodiments of the present invention, preferably, the stabilizer is selected from at least one of sodium acetate, potassium acetate, and dipotassium hydrogen phosphate.

[0043] In some embodiments of the present invention, preferably, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite, and sodium formaldehyde sulfoxylate.

[0044] In some embodiments of the present invention, preferably, the acid-base neutralizer is selected from at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0045] In some embodiments of the present invention, preferably, the weight ratio of the total weight of the monomers represented by Formula I-IV, the molecular weight regulator, and the initiator is 488 - 1510:67 - 890:1:1.

[0046] In some embodiments of the present invention, preferably, the weight ratio of the total weight of the monomers represented by Formula I-IV, the stabilizer, and the acid-base neutralizer is 579 - 1327:83 - 460:1.

[0047] In some embodiments of the present invention, preferably, at least one of an emulsifier, an oil-phase dispersant, a chelating agent, and an inverse-phase agent is further added to the polymerization reaction.

[0048] In some embodiments of the present invention, preferably, the oil-phase dispersant is selected from at least one of No. 5 white oil, No. 7 white oil, No. 10 white oil, diesel oil, kerosene, and light crude oil.

[0049] In some embodiments of the present invention, preferably, the chelating agent is selected from at least one of ethylenediaminetetraacetic acid, nitrilotriacetic acid, and ethylenediamine.

[0050] In some embodiments of the present invention, preferably, the inverse-phase agent is selected from at least one of isomeric tridecyl alcohol polyoxyethylene ether and lauric acid polyoxyethylene ether.

[0051] In some embodiments of the present invention, preferably, the weight ratio of the polymer, the emulsifier, and the inverse-phase agent is 1:0.1 - 0.3:0.1 - 0.25.

[0052] In some embodiments of the present invention, preferably, the weight ratio of the polymer, the oil-phase dispersant, and the chelating agent is 1:0.12 - 0.24:0.001 - 0.005.

[0053] In some embodiments of the present invention, preferably, the process of contacting and carrying out the polymerization reaction is carried out according to the following steps:

[0054] In the first step, monomers shown in Formula I-IV, a stabilizer, a molecular weight regulator, an acid-base neutralizer, and an initiator are subjected to a first mixing and a first polymerization reaction to obtain a first mixed solution;

[0055] In the second step, an emulsifier, an oil-phase dispersant, and a chelating agent are mixed with a part of the first mixed solution and subjected to a second polymerization reaction to obtain a second mixed solution;

[0056] In the third step, a chelating agent is added to the second mixed solution for chelation to obtain a third mixed solution;

[0057] In the fourth step, the temperature of the third mixed solution is raised, and an initiator is added to the solution for a third polymerization reaction to obtain a fourth mixed solution;

[0058] In the fifth step, the remaining first mixed solution from the second step is added to the fourth mixed solution for a fourth polymerization reaction to obtain the polymer.

[0059] In some embodiments of the present invention, preferably, the pH value of the first mixed solution is between 6.5 and 7.0.

[0060] In some embodiments of the present invention, preferably, the first polymerization reaction is carried out under a water bath condition; the temperature of the water bath is 20-24°C.

[0061] In some embodiments of the present invention, preferably, the emulsifier is a mixture of fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether polypropylene ether in a mass ratio of 1:1-2.

[0062] In some embodiments of the present invention, preferably, the oil-phase dispersant is a mixture of equal mass ratios of No. 7 white oil and kerosene.

[0063] In some embodiments of the present invention, preferably, the chelating agent is ethylenediaminetetraacetic acid.

[0064] In some embodiments of the present invention, preferably, the part of the first mixed solution accounts for 65-100% of the total volume of the first mixed solution.

[0065] In some embodiments of the present invention, preferably, the second mixing is a homogeneous mixing; the viscosity of the emulsification system after the homogeneous mixing is 950-1050 cp.

[0066] In some embodiments of the present invention, preferably, in the third step, nitrogen is introduced into the second mixed solution, and the introduction time is 45-90 min.

[0067] In some embodiments of the present invention, preferably, in the fourth step, the process of raising the temperature of the third mixed solution includes: raising the temperature by 0.05 - 0.2 °C in 15 - 30 seconds, controlling the heating rate to decrease to raising the temperature by 0.05 - 0.2 °C in 36 - 44 seconds, and after exceeding 44 °C, raising the temperature by 0.05 - 0.2 °C in 3 - 5 minutes, with the maximum temperature not exceeding 65 °C.

[0068] In some embodiments of the present invention, preferably, in the fourth step, the concentration of the initiator is 25 - 32% by weight.

[0069] In some embodiments of the present invention, preferably, in the fourth step, the temperature of the initiation is 17 - 19 °C.

[0070] In some embodiments of the present invention, preferably, the weight ratio of the initiator added in the first step to the initiator added in the fourth step is 2:1 - 1:2.

[0071] In some embodiments of the present invention, preferably, in the fifth step, the addition rate is to add 0.5 - 20% of the total volume of the remaining first mixed solution per minute until it is completely added.

[0072] The third aspect of the present invention provides a polymer prepared by the method described in the second aspect of the present invention.

[0073] The fourth aspect of the present invention provides a composition, characterized in that the composition includes a polymer and an auxiliary agent, wherein the definition of the polymer is the same as that described in the first aspect and / or the third aspect of the present invention.

[0074] In some embodiments of the present invention, preferably, the auxiliary agent includes at least one of an emulsifier, an oil - phase dispersant, a chelating agent, and an inverse agent.

[0075] In some embodiments of the present invention, preferably, the emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether polyoxypropylene ether, ammonium alkylphenol ethoxide sulfate, sorbitan fatty acid ester, and glycerol monooleate, and more preferably, the fatty alcohol polyoxyethylene ether is selected from AEO - 7 and / or AEO - 9.

[0076] In some embodiments of the present invention, preferably, the oil - phase dispersant is selected from at least one of 5# white oil, 7# white oil, 10# white oil, diesel oil, kerosene, and light crude oil.

[0077] In some embodiments of the present invention, preferably, the chelating agent is selected from at least one of ethylenediaminetetraacetic acid, nitrilotriacetic acid, and ethylenediamine.

[0078] In some embodiments of the present invention, preferably, the phase inversion agent is selected from at least one of isomeric tridecyl alcohol polyoxyethylene ether and lauryl acid polyoxyethylene ether.

[0079] In some embodiments of the present invention, preferably, the weight ratio of the polymer, emulsifier, and phase inversion agent is 1: 0.1 - 0.3: 0.1 - 0.25;

[0080] In some embodiments of the present invention, preferably, the weight ratio of the polymer, oil phase dispersant, and chelating agent is 1: 0.12 - 0.24: 0.001 - 0.005.

[0081] In some embodiments of the present invention, preferably, the fatty alcohol polyoxyethylene ether polyoxypropylene ether is CPE - 1500 with the brand name of Haishihua produced by Jiangsu Haian Petrochemical Factory.

[0082] In some embodiments of the present invention, preferably, the fatty alcohol polyoxyethylene ether polyoxypropylene ether is the low - foam penetrant SF produced by Sunda Chemical Industry (Nantong) Co., Ltd.

[0083] The fifth aspect of the present invention provides the application of the polymer described in the first aspect and the third aspect of the present invention and / or the composition described in the fourth aspect in a drag reducer.

[0084] In the present invention, conventional methods in the prior art can be used to test the content of each structural unit in the polymer, such as infrared spectroscopy, nuclear magnetic resonance, and the feeding amount of monomers during the polymerization process, etc. Preferably, the feeding amount of monomers is used to determine the content of each structural unit in the polymer. Specifically, the feeding ratio of each monomer actually participating in the polymerization is determined by testing the content of unreacted monomers, and then the content of each structural unit in the polymer is determined. Further, in the present invention, after testing, the content of each unreacted monomer in the polymer is below 0.02% by weight, indicating that all monomers basically participate in the polymerization reaction. Specifically, the content of the residual monomers is determined by liquid chromatography.

[0085] The present invention will be described in detail below through examples. In the following examples, the mass of the polymer is obtained by adding up the masses of the polymer monomers put in; the monomers shown in Formulas I - IV, wherein the monomer of Formula I is the BEM series products of Yancheng Zhongbang Technology New Materials Co., Ltd.; the monomer of Formula II is AMPS of Shandong Jinshi Environmental Protection Technology Co., Ltd., the monomer of Formula III is the ice crystal - grade acrylic acid of Taixing Shenke Chemical Co., Ltd.; the monomer of Formula IV is the commercially available acrylamide of Shandong Ruihai New Materials Technology Co., Ltd.

[0086] Example 1

[0087] First step: Dissolve 5.3 g of the monomer shown in Formula I, 49.2 g of the monomer shown in Formula II, 65.5 g of the monomer shown in Formula III, and 175.2 g of the monomer shown in Formula IV in deionized water. Among them, in the monomer shown in Formula I, R1 is n-octadecyl, x is 10, and R2 is methyl; in the monomer shown in Formula II, both R3 and R3' are methyl; add sodium acetate (stabilizer), dodecyl mercaptan (molecular weight regulator), and 0.5 g of ammonium persulfate (initiator), and adjust the pH value of the obtained liquid to 6.8 with 25 wt% ammonia water (acid-base neutralizer), and keep the temperature at 24 °C with a water bath to obtain the first mixed solution;

[0088] Second step: Homogeneously mix 15 g of AEO-9 and 20 g of CPE-1500 (emulsifiers), 36.9 g of No. 7 white oil (oil phase dispersant), and 1.11 g of ethylenediaminetetraacetic acid (chelating agent) with a part of the first mixed solution (accounting for 75% of the total volume of the first mixed solution). After homogenization, the viscosity of the emulsion system is maintained at 1000 cp to obtain the second mixed solution;

[0089] Third step: After introducing nitrogen into the second mixed solution for 68 minutes, add 1 g of ethylenediaminetetraacetic acid (chelating agent), and control the initiation temperature at 18 °C to obtain the third mixed solution;

[0090] Fourth step: After initiation, control the heating rate to increase by 0.1 °C in 22.5 seconds, and at 38 °C, control the heating rate to decrease to increase by 0.1 °C in 45 seconds. After 45 °C, the heating rate is increased by 0.1 °C in 5 minutes, and the maximum temperature is 47 °C. Add 0.5 g of ammonium persulfate (initiator) to the third mixed solution for the third polymerization reaction to obtain the fourth mixed solution;

[0091] Fifth step: Add 12% of the remaining first mixed solution in the second step to the fourth mixed solution per minute until it is completely added, and carry out the fourth polymerization reaction. Add 36.33 g of isomeric tridecyl alcohol polyoxyethylene ether (inverting agent) to the polymer and stir for 20 minutes to obtain the composition. According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of this polymer is 6.5 million Daltons.

[0092] Determine the composition of the composition according to the feeding situation.

[0093] Example 2

[0094] Prepare the polymer and formulate the composition according to the method of Example 1, except that in the first step, in the monomer shown in Formula I, R1 is n-hexadecyl and x is 10;

[0095] In the first step, the emulsifiers are 16 g of AEO-7 and 18 g of CPE-1500; the oil phase dispersant is 42.8 g of No. 9 white oil; the initiator is 0.55 g of ammonium persulfate; the chelating agent is 1.2 g of ethylenediaminetetraacetic acid;

[0096] In the fourth step, the initiator is 0.55 g of ammonium persulfate;

[0097] In the sixth step, the phase inversion agent is 51 g of polyoxyethylene laurate;

[0098] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this example is 6.8 million Daltons.

[0099] Example 3

[0100] Prepare the polymer and formulate the composition according to the method of Example 1, except that in the first step, in the monomer shown in Formula I, R1 is n-tetradecyl and x is 10;

[0101] In the second step, the emulsifier is 21 g of AEO-7 and 25 g of low-foaming penetrant SF (Jiangsu Sanda Chemical Industry); the oil-phase dispersant is 47.2 g of 10# white oil; the initiator is 0.65 g of sodium bisulfite; the chelating agent is 1.4 g of nitrilotriacetic acid;

[0102] In the fourth step, the initiator is 0.65 g of sodium bisulfite;

[0103] In the sixth step, the phase inversion agent is 61 g of polyoxyethylene laurate;

[0104] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this example is 7.1 million Daltons.

[0105] Example 4

[0106] Prepare the polymer and formulate the composition according to the method of Example 1, except that in the first step, in the monomer shown in Formula I, R1 is n-dodecyl and x is 12;

[0107] In the second step, the emulsifier is 20 g of AEO-7 and 25 g of CPE-1500; the oil-phase dispersant is 46.9 g of 7# white oil; the initiator is 0.5 g of sodium formaldehyde sulfoxylate; the chelating agent is 0.6 g of ethylenediaminetetraacetic acid and 0.7 g of ethylenediamine;

[0108] In the fourth step, the initiator is 0.5 g of sodium formaldehyde sulfoxylate;

[0109] In the sixth step, the phase inversion agent is 54 g of isomeric tridecanol polyoxyethylene ether;

[0110] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this example is 7.2 million Daltons.

[0111] Comparative Example 1

[0112] The polymer was prepared and the composition was formulated according to the method of Example 1, except that in the first step, R1 in the monomer represented by Formula I was n-docosyl;

[0113] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this comparative example was 5 million Daltons.

[0114] Comparative Example 2

[0115] The polymer was prepared and the composition was formulated according to the method of Example 1, except that in the first step, the feeding amount was adjusted so that the weight ratio of the structural unit represented by Formula 1, the structural unit represented by Formula 2, the structural unit represented by Formula 3, and the structural unit represented by Formula 4 in the polymer was 1:80:18:52;

[0116] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this comparative example was 9.2 million Daltons.

[0117] Comparative Example 3

[0118] The polymer was prepared and the composition was formulated according to the method of Example 1, except that in the first step, no molecular weight regulator was added;

[0119] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this comparative example was 13 million Daltons.

[0120] Comparative Example 4

[0121] The polymer was prepared and the composition was formulated according to the method of Example 1, except that in the first step, the monomer represented by Formula I was not added;

[0122] According to the test method of the Brookfield viscometer, the viscosity-average molecular weight of the polymer prepared in this comparative example was 6.5 million Daltons.

[0123] Test Example 1

[0124] The composition obtained according to the method of the example was a milky white or light yellow homogeneous emulsion, with a pH value between 6.5 and 7.5. The compositions prepared in Example 1 and Example 2 were respectively made into 0.1 wt% aqueous fracturing fluids with water. After rapid dissolution, the solution viscosities both reached about 3.0 mPa·s. The detection method was in accordance with the Energy Industry Standard of the People's Republic of China (NB / T14003.1-2015, Performance Index and Evaluation Method of Slickwater). Within 15 minutes, at different times, pressures, pressure differences, and flow rates, the average drag reduction rates of the aqueous fracturing fluids prepared with the compositions prepared in Example 1 and Example 2 could both reach over 80% (the results of Example 1 are shown in Table 1, and the results of Example 2 are shown in Table 2), meeting the requirements of the industry standard NBT 14003.1-2015, being able to meet the on-site application standard, and having significant advantages.

[0125] Table 1

[0126]

[0127]

[0128] Table 2

[0129]

[0130]

[0131] Test Example 2

[0132] The composition obtained by the method of the embodiment is a milky white or light yellow homogeneous emulsion, with a pH value between 6.5 and 7.5. It is formulated into a 0.1 wt% water-based fracturing fluid with water. After rapid dissolution, the solution viscosity reaches about 3.0 mPa·s. The detection method is in accordance with the industry standard (NB / T 14003.1-2015, Performance Index and Evaluation Method of Slickwater). The drag reduction rates of the water-based fracturing fluids prepared with the compositions obtained in Examples 1-4 are all above 73% (specific results are shown in Table 3), meeting the requirements of the industry standard NBT 14003.1-2015, being able to meet the on-site application standard, and having significant advantages.

[0133] Table 3

[0134]

[0135] It can be seen from the results in Table 3 that the drag reducers prepared with the polymers and compositions described in Examples 1-4 of the technical solution of the present invention have significantly better effects in terms of improving the drag reduction rate.

[0136] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A polymer, characterized in that, The polymer comprises structural units represented by Formula 1-4: Among them, R1 is selected from substituted or unsubstituted C 12 -C 20 alkyl; R2, R3 and R3’ are each independently selected from substituted or unsubstituted C1-C4 alkyl groups; X is selected from positive integers from 6 to 14; Wherein, the weight ratio of the structural unit represented by Formula 1, the structural unit represented by Formula 2, the structural unit represented by Formula 3 and the structural unit represented by Formula 4 is 1: 2.6-74: 0.5-17: 1.6-42, and the viscosity-average molecular weight of the polymer is 4 million to 10 million Daltons.

2. The polymer according to claim 1, wherein R1 is selected from unsubstituted C 12 -C 20 alkyl; And / or, R2, R3 and R3’ are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl or isobutyl; And / or, X is selected from positive integers from 7 to 13; And / or, the weight ratio of the structural unit represented by Formula 1, the structural unit represented by Formula 2, the structural unit represented by Formula 3 and the structural unit represented by Formula 4 is 1: 4.3-57: 1.9-13.4: 3.2-35.3; And / or, the viscosity-average molecular weight of the polymer is 5 million to 8 million Daltons.

3. The polymer according to claim 1 or 2, wherein R1 is selected from unsubstituted C 16 -C 20 alkyl; And / or, R2, R3 and R3’ are each independently selected from methyl or ethyl; And / or, X is selected from positive integers from 8 to 12.

4. The polymer according to any one of claims 1-3, wherein, R1 is n-octadecyl; And / or, R2, R3 and R3’ are all methyl; And / or, X is selected from positive integers from 10 to 12.

5. A method for preparing a polymer, characterized in that, The method includes: contacting the monomers represented by Formula I-IV and carrying out a polymerization reaction to obtain the polymer, wherein the weight ratio of the monomer represented by Formula I, the monomer represented by Formula II, the monomer represented by Formula III and the monomer represented by Formula IV is 1: 2.6-74: 0.5-17: 1.6-42; Wherein, the definitions of R1, R2, R3, R3’ and X are the same as those defined in any one of Claims 1-4.

6. The method according to claim 5, wherein The weight ratio of the monomer represented by Formula I, the monomer represented by Formula II, the monomer represented by Formula III and the monomer represented by Formula IV is 1: 4.3-57: 1.9-13.4: 3.2-35.

3.

7. The method according to claim 5 or 6, wherein At least one of a molecular weight regulator, an acid-base neutralizer, a stabilizer and an initiator is further added to the polymerization reaction system; Preferably, the molecular weight regulator is selected from at least one of dodecyl mercaptan, tetradecyl mercaptan and diisopropylxanthogen disulfide; Preferably, the stabilizer is selected from at least one of sodium acetate, potassium acetate and dipotassium hydrogen phosphate; Preferably, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite and sodium formaldehyde sulfoxylate; Preferably, the acid-base neutralizer is selected from at least one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

8. The method according to any one of claims 5-7, wherein The weight ratio of the total weight of the monomers represented by Formula I-IV, the molecular weight regulator and the initiator is 488-1510: 67-890: 1; Preferably, the weight ratio of the total weight of the monomers represented by Formula I-IV, the stabilizer and the acid-base neutralizer is 579-1327: 83-460:

1.

9. A polymer prepared by the method according to any one of Claims 5-8.

10. A composition, characterized in that, The composition comprises a polymer and an auxiliary agent, wherein the definition of the polymer is the same as that defined in any one of Claims 1-4 and 9.

11. The composition according to claim 10, wherein, The auxiliary agent includes at least one of an emulsifier, an oil-phase dispersant, a chelating agent, and an inverse-phase agent; Preferably, the emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ether polyoxypropylene ether, ammonium alkylphenol ethoxide sulfate, sorbitan fatty acid ester, and glycerol monooleate. More preferably, the fatty alcohol polyoxyethylene ether is selected from AEO-7 and / or AEO-9; Preferably, the oil-phase dispersant is selected from at least one of No. 5 white oil, No. 7 white oil, and No. 10 white oil; Preferably, the chelating agent is selected from at least one of ethylenediaminetetraacetic acid, nitrilotriacetic acid, and ethylenediamine; Preferably, the inverse-phase agent is selected from at least one of isomeric tridecyl alcohol polyoxyethylene ether and lauric acid polyoxyethylene ether.

12. The composition according to claim 11, wherein, The weight ratio of the polymer, the emulsifier, and the inverse-phase agent is 1: 0.1-0.3: 0.1-0.25; Preferably, the weight ratio of the polymer, the oil-phase dispersant, and the chelating agent is 1: 0.12-0.24: 0.001-0.

005.

13. Use of the polymer according to any one of claims 1-4 and 9 and / or the composition according to any one of claims 10-12 in a drag reducer.

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