Multi-component copolymer and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of petroleum drilling. Specifically disclosed are a multi-component copolymer and a preparation method therefor and a use thereof. The multi-component copolymer comprises a structural unit A, a structural unit B, a structural unit C, and a structural unit D, wherein the structural unit A has a structure as represented by formula (1), the structural unit B has a structure as represented by formula (2), and the structural unit C has a structure as represented by formula (3). The multi-component copolymer of the present invention can be used as a well wall stabilizer, in particular as a borehole strengthening type well wall stabilizer, can inhibit the hydration and swelling of stratum clay minerals, effectively plugs rocks with developed fractures and bedding, effectively strengthens a borehole, maintains well wall stability, has a certain filtrate loss reducing effect, and improves the efficiency of oil and gas resource development and utilization and the economic benefits of oilfield companies.

Description

Multi-component copolymer and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202310702169.0 filed on June 13, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of oil drilling, and in particular to a multi-component copolymer and a preparation method and application thereof. Background Art

[0004] Wellbore instability is one of the complex underground situations commonly encountered in drilling projects, which seriously affects the acquisition of geological data, drilling speed, drilling quality and cost. In some newly explored areas, wellbore instability may prevent drilling into the target layer, which in turn leads to delays in exploration and development speed, affecting economic benefits. The essence of wellbore instability is mechanical instability. When the stress on the wellbore rock exceeds its own strength, wellbore instability will occur. The causes of wellbore instability are complex and can be mainly summarized into three aspects: mechanical factors, physical and chemical factors and engineering and technical measures. Wellbore instability may occur in the formations encountered during the drilling process, such as shale, sandy or silty mudstone, flow rock, sandstone, muddy sandstone or siltstone, igneous rock, etc.

[0005] Wellbore instability is a universal problem in the oil and gas industry, present in almost all oil and gas field developments, affecting safe drilling and causing significant economic losses. Therefore, improving wellbore stability technology is of great significance for achieving safe, efficient, and low-cost drilling goals. Based on the wellbore instability phenomena encountered in practice, various technical measures for wellbore stabilization have been summarized. Among them, optimizing the type and formulation of drilling fluid is one of the key measures to improve wellbore instability. This includes improving the inhibitory properties of drilling fluids; using physical and chemical methods to seal formation bedding and cracks to prevent drilling fluid filtrate from entering the formation; and improving the membrane efficiency of drilling fluids on the formation to minimize the amount of drilling fluid filtrate entering the formation. Commonly used anti-collapse drilling fluid treatment agents at home and abroad include inorganic salts, asphalts, silicates, and polymers. Inorganic salts such as KCl and NH4Cl primarily act by inhibiting clay hydration and expansion, but their effectiveness is limited. Asphalt treatment agents are solid when the operating temperature is below their softening point and become soft when the temperature approaches their softening point. Under the action of pressure differentials, asphalt treatment agents are easily squeezed into the bedding cracks and pore throats of the formation, forming a sealing zone on the wellbore wall, which can effectively prevent drilling fluid filtrate from entering the formation and prevent wellbore collapse. However, asphalt products are usually fluorescent, which affects geological logging, and therefore their use is limited. Polymer treatment agents mainly inhibit clay hydration and dispersion and prevent shale collapse through adsorption and coating, but polymer treatment agents generally have poor temperature resistance and are relatively expensive. Although the above-mentioned treatment agents each have their advantages, they also have obvious shortcomings. Therefore, how to improve the effectiveness of wellbore stabilizers has always been a major technical difficulty in the field of drilling fluids.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the problem of wellbore instability in drilling operations in the prior art, and to provide a multi-polymer and its preparation method and application. The multi-polymer can be used as a wellbore strengthening wellbore stabilizer to inhibit the hydration expansion of clay minerals in the formation, effectively seal cracks and rocks with developed bedding, and effectively strengthen the wellbore.

[0008] In order to achieve the above-mentioned object, the first aspect of the present invention provides a multi-component copolymer, wherein the multi-component copolymer comprises a structural unit A, a structural unit B, a structural unit C and a structural unit D; wherein the structural unit A has a structure represented by formula (1); the structural unit B has a structure represented by formula (2); the structural unit C has a structure represented by formula (3); and the structural unit D has a structure represented by formula (4);

[0009] In formula (1), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M is selected from hydrogen or an alkali metal;

[0010] In formula (2), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0011] In formula (3), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0012] In formula (4), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and X is selected from halogen.

[0013] A second aspect of the present invention provides a method for preparing a multi-component copolymer, the method comprising:

[0014] In the presence of an initiator, the polymerization monomers are subjected to solution polymerization to obtain a multi-component copolymer; wherein the polymerization monomers include: a monomer represented by formula (I), a monomer represented by formula (II), a monomer represented by formula (III) and a monomer represented by formula (IV);

[0015] In formula (I), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M1 is selected from hydrogen or an alkali metal;

[0016] In formula (II), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0017] In formula (III), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0018] In formula (IV), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and M2 is selected from halogen.

[0019] The third aspect of the present invention provides a multi-component copolymer prepared by the aforementioned preparation method.

[0020] A fourth aspect of the present invention provides the use of the aforementioned multi-polymer as a wellbore stabilizer in drilling; preferably, the multi-polymer is used as a wellbore stabilizer in a wellbore reinforcement type wellbore.

[0021] A fifth aspect of the present invention provides a water-based drilling fluid using the aforementioned multi-polymer as a wellbore stabilizer; preferably, the content of the multi-polymer is 1-6 wt % based on the total weight of the water-based drilling fluid.

[0022] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0023] The multi-component copolymer provided by the present invention has strong linear expansion ability, and can form multiple adsorption points on the well wall, thereby preventing clay from dispersing and stabilizing the well wall, thereby reducing the occurrence of underground accidents.

[0024] The multi-component copolymer of the present invention can be used as a wellbore stabilizer, especially a wellbore strengthening wellbore stabilizer, which can inhibit the hydration expansion of clay minerals in the formation, effectively seal rocks with developed cracks and bedding, effectively strengthen the wellbore, maintain the stability of the wellbore, and at the same time has a certain filtration loss reduction effect, thereby improving the efficiency of oil and gas resource development and utilization and the economic benefits of oilfield companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is an infrared spectrum of polymer W1 obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] The first aspect of the present invention provides a multi-component copolymer, comprising a structural unit A, a structural unit B, a structural unit C, and a structural unit D; wherein the structural unit A has a structure represented by formula (1); the structural unit B has a structure represented by formula (2); the structural unit C has a structure represented by formula (3); and the structural unit D has a structure represented by formula (4);

[0028] In formula (1), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M is selected from hydrogen or an alkali metal;

[0029] In formula (2), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0030] In formula (3), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0031] In formula (4), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and X is selected from halogen.

[0032] The alkyl group or alkylene group in the present invention includes a linear or branched substituted or unsubstituted alkyl group or alkylene group.

[0033] The multi-component copolymer of the present invention contains aromatic groups, which can enhance the electrostatic interaction of cationic groups so that the copolymer has better adhesion performance.

[0034] In some embodiments of the present invention, in formula (1), R1 and R2 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl or ethyl; R3 is selected from a C1-C3 alkylene group, preferably methylene or 1,2-ethylene; and M is selected from hydrogen, sodium or potassium.

[0035] In some embodiments of the present invention, in formula (2), R4 and R5 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl.

[0036] In some embodiments of the present invention, in formula (3), R6 and R7 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl.

[0037] In some embodiments of the present invention, in formula (4), R8 and R9 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl; and X is selected from Cl, Br or I.

[0038] The structural unit A can be selected from the structure represented by formula (1-1), the structure represented by formula (1-2), the structure represented by formula (1-3), the structure represented by formula (1-4), the structure represented by formula (1-5), the structure represented by formula (1-6), the structure represented by formula (1-7), the structure represented by formula (1-8), the structure represented by formula (1-9), the structure represented by formula (1-10), the structure represented by formula (1-11), the structure represented by formula (1-12), the structure represented by formula (1-13), the structure represented by formula (1-14), , at least one of the structural units represented by the structure represented by formula (1-15), the structure represented by formula (1-16), the structure represented by formula (1-17), the structure represented by formula (1-18), the structure represented by formula (1-19), the structure represented by formula (1-20), the structure represented by formula (1-21), the structure represented by formula (1-22), the structure represented by formula (1-23), the structure represented by formula (1-24), the structure represented by formula (1-25), the structure represented by formula (1-26) and the structure represented by formula (1-27); wherein,

[0039] Formula (1-1): R1 is H; R2 is H; M is H; R3 is -CH2-;

[0040] Formula (1-2): R1 is H; R2 is H; M is K; R3 is -CH2-;

[0041] Formula (1-3): R1 is H; R2 is H; M is Na; R3 is -CH2-;

[0042] Formula (1-4): R1 is H; R2 is -CH3; M is H; R3 is -CH2-;

[0043] Formula (1-5): R1 is H; R2 is -CH3; M is K; R3 is -CH2-;

[0044] Formula (1-6): R1 is H; R2 is -CH3; M is Na; R3 is -CH2-;

[0045] Formula (1-7): R1 is H; R2 is -CH2CH3; M is H; R3 is -CH2-;

[0046] Formula (1-8): R1 is H; R2 is -CH2CH3; M is K; R3 is -CH2-;

[0047] Formula (1-9): R1 is H; R2 is -CH2CH3; M is Na; R3 is -CH2-;

[0048] Formula (1-10): R1 is -CH3; R2 is H; M is H; R3 is -CH2-;

[0049] Formula (1-11): R1 is -CH3; R2 is H; M is K; R3 is -CH2-;

[0050] Formula (1-12): R1 is -CH3; R2 is H; M is Na; R3 is -CH2-;

[0051] Formula (1-13): R1 is -CH3; R2 is -CH3; M is H; R3 is -CH2-;

[0052] Formula (1-14): R1 is -CH3; R2 is -CH3; M is K; R3 is -CH2-;

[0053] Formula (1-15): R1 is -CH3; R2 is -CH3; M is Na; R3 is -CH2-;

[0054] Formula (1-16): R1 is -CH3; R2 is -CH2CH3; M is H; R3 is -CH2-;

[0055] Formula (1-17): R1 is -CH3; R2 is -CH2CH3; M is K; R3 is -CH2-;

[0056] Formula (1-18): R1 is -CH3; R2 is -CH2CH3; M is Na; R3 is -CH2-;

[0057] Formula (1-19): R1 is -CH2CH3; R2 is H; M is H; R3 is -CH2-;

[0058] Formula (1-20): R1 is -CH2CH3; R2 is H; M is K; R3 is -CH2-;

[0059] Formula (1-21): R1 is -CH2CH3; R2 is H; M is Na; R3 is -CH2-;

[0060] Formula (1-22): R1 is -CH2CH3; R2 is -CH3; M is H; R3 is -CH2-;

[0061] Formula (1-23): R1 is -CH2CH3; R2 is -CH3; M is K; R3 is -CH2-;

[0062] Formula (1-24): R1 is -CH2CH3; R2 is -CH3; M is Na; R3 is -CH2-;

[0063] Formula (1-25): R1 is -CH2CH3; R2 is -CH2CH3; M is H; R3 is -CH2-;

[0064] Formula (1-26): R1 is -CH2CH3; R2 is -CH2CH3; M is K; R3 is -CH2-;

[0065] Formula (1-27): R1 is -CH2CH3; R2 is -CH2CH3; M is Na; R3 is -CH2-.

[0066] The structural unit B can be selected from at least one of the structural units represented by formula (2-1), formula (2-2), formula (2-3), formula (2-4), formula (2-5), formula (2-6), formula (2-7), and formula (2-8); wherein,

[0067] Formula (2-1): R4 is H; R5 is H;

[0068] Formula (2-2): R4 is H; R5 is -CH3;

[0069] Formula (2-3): R4 is H; R5 is -CH2CH3;

[0070] Formula (2-4): R4 is -CH3; R5 is -CH3;

[0071] Formula (2-5): R4 is -CH3; R5 is -CH2CH3;

[0072] Formula (2-6): R4 is -CH2CH3; R5 is -CH2CH3;

[0073] Formula (2-7): R4 is -CH2CH2CH3; R5 is -CH2CH3;

[0074] Formula (2-8): R4 is -CH2CH2CH3; R5 is -CH2CH2CH3.

[0075] The structural unit C can be selected from at least one of the structural units represented by formula (3-1), formula (3-2), formula (3-3), formula (3-4), formula (3-5), formula (3-6), formula (3-7), and formula (3-8); wherein,

[0076] Formula (3-1): R6 is H; R7 is H;

[0077] Formula (3-2): R6 is H; R7 is -CH3;

[0078] Formula (3-3): R6 is H; R7 is -CH2CH3;

[0079] Formula (3-4): R6 is -CH3; R7 is -CH3;

[0080] Formula (3-5): R6 is -CH3; R7 is -CH2CH3;

[0081] Formula (3-6): R6 is -CH2CH3; R7 is -CH2CH3;

[0082] Formula (3-7): R6 is -CH2CH2CH3; R8 is -CH2CH3;

[0083] Formula (3-8): R6 is -CH2CH2CH3; R7 is -CH2CH2CH3.

[0084] The structural unit D can be, for example, selected from at least one of the structural units represented by formula (4-1), formula (4-2), formula (4-3), formula (4-4), formula (4-5), formula (4-6), formula (4-7), formula (4-8), formula (4-9), formula (4-10), formula (4-11), formula (4-12), formula (4-13), formula (4-14), formula (4-15), formula (4-16), formula (4-17), and formula (4-18); wherein,

[0085] Formula (4-1): R8 is H; R9 is H; X is Br;

[0086] Formula (4-2): R8 is H; R9 is H; X is Cl;

[0087] Formula (4-3): R8 is H; R9 is H; X is I;

[0088] Formula (4-4): R8 is H; R9 is -CH3; X is Br;

[0089] Formula (4-5): R8 is H; R9 is -CH3; X is Cl;

[0090] Formula (4-6): R8 is H; R9 is -CH3; X is I;

[0091] Formula (4-7): R8 is -CH3; R9 is -CH3; X is Br;

[0092] Formula (4-8): R8 is -CH3; R9 is -CH3; X is Cl;

[0093] Formula (4-9): R8 is -CH3; R9 is -CH3; X is I;

[0094] Formula (4-10): R8 is -CH3; R9 is -CH2CH3; X is Br;

[0095] Formula (4-11): R8 is -CH3; R9 is -CH2CH3; X is Cl;

[0096] Formula (4-12): R8 is -CH3; R9 is -CH2CH3; X is I;

[0097] Formula (4-13): R8 is -CH3; R9 is -CH2CH2CH3; X is Br;

[0098] Formula (4-14): R8 is -CH3; R9 is -CH2CH2CH3; X is Cl;

[0099] Formula (4-15): R8 is -CH2CH3; R9 is -CH2CH2CH3; X is I;

[0100] Formula (4-16): R8 is -CH2CH3; R9 is -CH2CH3; X is Br;

[0101] Formula (4-17): R8 is -CH2CH3; R9 is -CH2CH3; X is Cl;

[0102] Formula (4-18): R8 is -CH3; R9 is -CH2CH3; X is I.

[0103] Preferably, the structural unit represented by formula (1) is provided by 2-acrylamide-2-methylpropanesulfonic acid; the structural unit represented by formula (2) is provided by acrylamide; the structure represented by formula (3) is provided by 2-phenoxyethyl acrylate; and the structural unit represented by formula (4) is provided by 2-aminoethyl methacrylate hydrochloride.

[0104] In the present invention, the structural units contained in the multi-component copolymer are formed by addition polymerization of carbon-carbon double bonds contained in monomers corresponding to the structural units.

[0105] In some embodiments of the present invention, the molar ratio of the structural unit A, structural unit B, structural unit C and structural unit D is 0.5-2:1.4-1.8:1.5-4.2:0.3-0.8, preferably 1-1.5:1.6-1.7:2-3:0.5-0.7.

[0106] In some embodiments of the present invention, the average molecular weight of the multi-polymer is 20,000-150,000 g / mol, preferably 30,000-100,000 g / mol, and more preferably 80,000-90,000 g / mol.

[0107] The intrinsic viscosity of the multi-polymer is 200-500 mL / g, preferably 240-460 mL / g.

[0108] In the present invention, the composition and structure of the multi-component copolymer can be obtained by infrared analysis or inferred through monomer feeding and reaction.

[0109] A second aspect of the present invention provides a method for preparing a multi-component copolymer, the method comprising:

[0110] In the presence of an initiator, the polymerization monomers are subjected to solution polymerization to obtain a multi-component copolymer; wherein the polymerization monomers include: a monomer represented by formula (I), a monomer represented by formula (II), a monomer represented by formula (III) and a monomer represented by formula (IV);

[0111] In formula (I), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M1 is selected from hydrogen or an alkali metal;

[0112] In formula (II), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0113] In formula (III), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group;

[0114] In formula (IV), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and M2 is selected from halogen.

[0115] The present invention prepares multi-component copolymers through free radical polymerization. Solution polymerization is employed, wherein monomers and an initiator (i.e., a free radical initiator) are dissolved in a suitable solvent, and the polymerization reaction is carried out in solution. Polymers of varying molecular weights can be prepared by controlling the choice of solvent and initiator, the order in which the monomers are added, and the amount of monomers added.

[0116] In the present invention, the monomers can be added together to carry out solution polymerization in a one-step process. Alternatively, they can be added in two steps to carry out solution polymerization in a two-step process. That is, the monomer represented by formula (III), the monomer represented by formula (IV), and an initiator are first reacted in a solvent in a first step, and then the product of the first step reaction is reacted with the monomer represented by formula (I), the monomer represented by formula (II), and an initiator in a solvent in a second step.

[0117] The solution polymerization method of the present invention has the advantages of easy diffusion of polymerization heat, easy control of reaction temperature, low system viscosity, less chain transfer to polymers to generate branched or cross-linked products, easy control of product molecular weight, narrow molecular weight distribution, and direct production of the finished product in solution. It can be used to prepare polymers that can be used as wellbore strengthening well wall stabilizers and has broad application prospects in wellbore strengthening technology.

[0118] In some embodiments of the present invention, in formula (I), R1 and R2 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl or ethyl; R3 is selected from a C1-C3 alkylene group, preferably methylene or 1,2-ethylene; M1 is selected from hydrogen, sodium or potassium.

[0119] In some embodiments of the present invention, in formula (II), R4 and R5 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl.

[0120] In some embodiments of the present invention, in formula (III), R6 and R7 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl.

[0121] In some embodiments of the present invention, in formula (IV), R8 and R9 are each independently selected from hydrogen or a C1-C3 alkyl group, preferably hydrogen, methyl, ethyl or propyl; and M2 is selected from Cl, Br or I.

[0122] The polymerizable monomers in the present invention correspond one-to-one to the structural units in the first aspect, and the substituents are also the same as those in the first aspect. For specific selection, please refer to the description of the first aspect and will not be repeated here.

[0123] Preferably, the monomer represented by formula (I) can be selected from 2-acrylamide-2-methylpropanesulfonic acid; the monomer represented by formula (II) can be selected from acrylamide; the monomer represented by formula (III) can be selected from 2-phenoxyethyl acrylate; and the monomer represented by formula (IV) can be selected from 2-aminoethyl methacrylate hydrochloride.

[0124] In some embodiments of the present invention, the molar 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 0.5-2:1.4-1.8:1.5-4.2:0.3-0.8, preferably 1-1.5:1.6-1.7:2-3:0.5-0.7.

[0125] In some embodiments of the present invention, the conditions for the solution polymerization include: a temperature of 30-100° C., preferably 40-70° C.; and a time of 4-8 hours, preferably 6-7 hours.

[0126] The reaction time in the present invention refers to the total time required for the reaction of the four monomers. When a two-step solution polymerization method is used, the total reaction time of the first and second steps is 4-8 hours, preferably 6-7 hours; the reaction time of the first and second steps is independently selected from 2-6 hours, preferably 3-3.5 hours.

[0127] In order to allow the initiation reaction to proceed smoothly, the air in the reaction system may be replaced by ventilation, and the introduced gas may be selected from nitrogen, helium, neon and other basically reaction-inert gases.

[0128] In some embodiments of the present invention, the initiator is selected from one of alkyl halides, azobisisobutyronitrile (AIBN), 2-ketoglutaric acid, potassium persulfate, ceric ammonium nitrate and azobisisobutyramidine hydrochloride (V50); preferably potassium persulfate.

[0129] Based on the total weight of the polymerized monomers, the amount of the initiator used (by mass) is preferably 0.5-5 wt %, more preferably 1-2 wt %, of the total weight of the polymerized monomers.

[0130] In the present invention, whether the four monomers are solution polymerized using a one-step or two-step method, the amount of initiator used is based on the total weight of the polymerized monomers. When using a two-step method, the amount of initiator used in each reaction step is 0.25-2.5 wt %, preferably 0.5-1 wt %, based on the total weight of the polymerized monomers.

[0131] In some embodiments of the present invention, the solution polymerization is performed in a solvent.

[0132] In some embodiments of the present invention, the solvent is selected from one of deionized water, ethanol, methanol and dimethyl sulfoxide; preferably deionized water.

[0133] In some embodiments of the present invention, the amount of the solvent used is such that the total concentration of the polymerizable monomers in the solvent is 0.01-5 mol / L, preferably 0.1-1 mol / L.

[0134] Wherein, in the present invention, when adopting the one-step method, four monomers are added to the solvent together. When adopting the two-step method, the present invention does not specifically limit the concentration of the monomer represented by formula (III) and the monomer represented by formula (IV) in the solvent in the first step reaction, and can be carried out according to the conventional operation in the field. The total concentration of the polymerized monomers in the solvent refers to the total concentration 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) in the second step solvent in the second step reaction, based on the amount of feed, of 0.01-5 mol / L, preferably 0.1-1 mol / L.

[0135] Specifically, the synthesis steps of the multi-polymer using a two-step solution polymerization method are as follows:

[0136] ① Dissolve the monomer represented by formula (III) and the monomer represented by formula (IV) in a solvent and pour into a three-necked flask, stir at 300-400 rpm, and pass nitrogen for 10-20 minutes to eliminate oxygen in the container, add the initiator at a uniform rate, raise the temperature to 40-70° C., for example, 70° C., and react for 2-6 hours, for example, 3 hours; wherein the molar ratio of the monomer represented by formula (III) to the monomer represented by formula (IV) is 1.5-4.2:0.3-0.8, preferably 2-3:0.5-0.7; based on the total mass of the polymerized monomers (i.e., the total weight 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)), the amount of the initiator used in step ② (by mass) is 0.25-2.5wt% of the total mass of the polymerized monomers, preferably 0.5-1wt%;

[0137] ② Pour the product and solution into a rotary evaporator to remove the solvent, and place the remaining product in an oven to dry;

[0138] ③ Dissolve all the dried product with deionized water, increase the temperature to accelerate the dissolution, then add the monomer represented by formula (I) and the monomer represented by formula (II), pour the above solution into a three-necked flask, stir at 300-400 rpm, pass nitrogen for 10-20 min to remove oxygen in the container, add the initiator at a uniform rate, raise the temperature to 40-70 ° C, for example, 70 ° C, and react for 2-6 hours, for example, 3 hours; wherein the molar ratio of the monomer represented by formula (I) to the monomer represented by formula (II) is 0.5-2:1.4-1.8, preferably The ratio of the initiator to the monomer is selected as 1-1.5:1.6-1.7; based on the total weight of the polymerized monomers (i.e., the total weight 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)), the amount of the initiator used in step ③ (by mass) is 0.25-2.5 wt% of the total mass of the polymerized monomers, preferably 0.5-1 wt%; the amount of the solvent used in step ③ is such that the total concentration of the polymerized monomers in the solvent in step ③ is 0.01-5 mol / L, preferably 0.1-1 mol / L;

[0139] ④ The entire reaction process was carried out in a constant temperature water bath to ensure a stable nitrogen environment and temperature to obtain a multi-polymer.

[0140] The third aspect of the present invention provides a multi-component copolymer prepared by the aforementioned preparation method.

[0141] A fourth aspect of the present invention provides the use of the aforementioned multi-polymer as a wellbore stabilizer in drilling.

[0142] In some embodiments of the present invention, the multi-polymer is used as a wellbore stabilizer in a wellbore reinforcement type wellbore.

[0143] According to the present invention, the multi-polymer can achieve excellent well wall stability at a relatively low dosage.

[0144] The fifth aspect of the present invention provides a water-based drilling fluid using the aforementioned multi-polymer as a wellbore stabilizer.

[0145] In some embodiments of the present invention, the content of the multi-polymer is 1-6 wt % based on the total weight of the water-based drilling fluid.

[0146] The multi-component copolymer of the present invention can be used as a well wall stabilizer for drilling fluid, and can be used to prepare a water-based drilling fluid containing the multi-component copolymer as a well wall stabilizer. The water-based drilling fluid can be used in oil and gas drilling.

[0147] According to the present invention, the water-based drilling fluid may also contain other additives conventionally used in the art, such as bentonite, thickeners, anti-collapse agents, lubricants, weighting agents, alkaline regulators, etc. The types and contents of these additives can be the types and contents conventionally used in the art, and the present invention has no special limitation on this.

[0148] The multi-component copolymer of the present invention can be used as a wellbore stabilizer for drilling fluid, can inhibit the hydration expansion of formation clay minerals, effectively seal cracks and rocks with developed bedding, effectively strengthen the wellbore, maintain the stability of the wellbore wall, and at the same time has a certain filtration loss reduction effect, thereby improving the efficiency of oil and gas resource development and utilization and the economic benefits of oilfield companies.

[0149] The present invention will be described in detail below through examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0150] In the present invention, the drilling fluid is a water-based drilling fluid, and the synthesis of the polymer in the drilling fluid is studied and evaluated from multiple perspectives such as different additives, polymer structure, and polymer action mechanism.

[0151] In the present invention, the aforementioned additives may be commercially available products, or may be prepared according to methods known in the art, which will not be described in detail in the present invention.

[0152] In the present invention, the preparation method of the drilling fluid polymer adopts a free radical solution polymerization preparation method well known to those skilled in the art, which will not be described in detail herein. In addition, the present invention lists specific operations in the following text, which should not be understood by those skilled in the art as limiting the present invention.

[0153] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0154] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0155] 1. Experimental materials:

[0156] Monomer represented by formula (I) (2-acrylamide-2-methylpropanesulfonic acid): Anaiji Chemical Technology (Shanghai) Co., Ltd.

[0157] Monomer represented by formula (II) (acrylamide): Anaiji Chemical Technology (Shanghai) Co., Ltd.

[0158] Monomer represented by formula (III) (2-phenoxyethyl acrylate): Anaiji Chemical Technology (Shanghai) Co., Ltd.;

[0159] Monomer represented by formula (IV) (2-aminoethyl methacrylate hydrochloride): Anaiji Chemical Technology (Shanghai) Co., Ltd.

[0160] 2. Experimental instruments:

[0161] Electronic balance (ME104 / 02), constant temperature magnetic stirrer (T09-1S), digital constant temperature water bath (XMTD203), electric stirrer (HD2004W), variable frequency high-speed stirrer (GJSS-B12K), 1103 six-speed rotational viscometer (MK-03), and variable frequency high-temperature roller heating furnace (GW300) were all purchased from Qingdao Tongchun Petroleum Instrument Co., Ltd.

[0162] In the following examples, the performance testing methods involved are as follows:

[0163] 1. Performance test of polymer:

[0164] (1) Average molecular weight:

[0165] Polymer molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC, Wyatt, USA) using tetrahydrofuran as the mobile phase at a flow rate of 1.0 mL / min, narrow-distribution polystyrene as the standard, and a differential refractive index detector as the primary detector. The column and detection temperatures were 35°C. Purified samples were prepared with an appropriate amount of tetrahydrofuran to a desired concentration. Insoluble impurities were removed using a filter prior to analysis.

[0166] (2) Intrinsic viscosity:

[0167] The intrinsic viscosity of the polymers was measured using an Ubbelohde viscometer (1836-A, Tianjin Hongyang Machinery Equipment Co., Ltd.). A 2 g / mL polymer solution was prepared using anhydrous methanol as the solvent and then diluted to 2 / 3, 1 / 2, 1 / 3, and 1 / 4 of the original concentration. The test temperature was 35°C. The elution time of the methanol solvent and the polymer solutions at different concentrations was measured. The intrinsic viscosity of the polymers was extrapolated from the elution time plotted against concentration.

[0168] 2. Evaluation of the filtration performance of water-based drilling fluid: A medium-pressure filtration instrument is used to measure the filtration volume of the water-based drilling fluid containing a polymer wellbore stabilizer prepared by the solution method. The specific process is as follows:

[0169] Pour 150 mL of prepared drilling fluid into the medium-pressure filter loss meter, put the gasket and special filter paper in place, cover the lid and tighten the seal. Record the filtrate volume within 30 minutes at an output pressure of 0.7 MPa, which is the medium-pressure API filter loss of the drilling fluid in mL.

[0170] 3. Evaluation of the rheological properties of water-based drilling fluids: Reference data for the rheological properties of drilling fluids include apparent viscosity, plastic viscosity, and dynamic shear force. After stirring the water-based drilling fluid at a high-frequency speed of 12,000 rpm for 20 minutes, the values ​​at Φ600 and Φ300 were measured using a six-speed rotary viscometer in accordance with standard GB / T 16782-1997. The apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) of the water-based drilling fluid were calculated using the following formulas.

[0171] (1) Apparent viscosity AV (unit: mPa·s) = 1 / 2*Φ600;

[0172] (2) Plastic viscosity PV (unit: mPa·s) = Φ600-Φ300;

[0173] (3) Dynamic shear force (unit: Pa) YP = AV - PV.

[0174] 4. Evaluation of the inhibition performance of water-based drilling fluid:

[0175] The inhibitory performance of the treatment agent is evaluated through a linear expansion test. Using a dual-channel shale dilatometer, the differences in the swelling height of bentonite in different treatment agent solutions and deionized water are measured. This allows for a direct measurement of the treatment solution's ability to inhibit clay hydration expansion. The specific process is as follows:

[0176] (1) Cut a circular filter paper of appropriate size and place it at the bottom of the pressure tank. Weigh 5g of bentonite and pour it into the pressure tank. Place another circular filter paper and press it with a hydraulic press at a pressure of 10MPa for 5 minutes to form a rock block. (The purpose of placing the second filter paper is to prevent uneven expansion of the compressed bentonite after adding the solution).

[0177] (2) Start the linear expansion measurement software in the computer, install the pressure tank containing the compressed bentonite rock block on the measurement channel of the dual-channel shale dilatometer, and lock the edge of the pressure tank into the groove to reset the initial value of the dilatometer to zero.

[0178] (3) Use a dropper to slowly add the test solution along the inner wall of the pressure tank until a convex liquid surface appears above the pressure tank. Click the start button to start recording the change in the expansion height of the bentonite block over time.

[0179] (4) Record the swelling height after 16 h and export all the data measured by the software to a table for storage and processing.

[0180] The inhibitory performance of the treatment agent was evaluated through core immersion experiments. The appearance and morphological integrity of the cores were obtained after being immersed in different wellbore stabilizer solutions for 24 hours.

[0181] The following examples are used to illustrate the multi-component copolymers and their preparation methods of the present invention.

[0182] Example 1

[0183] A method for preparing a multi-component copolymer comprises the following steps:

[0184] Step ①: 2-phenoxyethyl acrylate and 2-aminoethyl methacrylate hydrochloride were dissolved in deionized water at a molar ratio of 2:0.5, the solution was poured into a three-necked flask, stirred at 300-400 rpm, and nitrogen was passed through for 10-20 minutes to remove oxygen from the container. 1 wt% (i.e., 1% of the total weight of the polymerizable monomers) of potassium persulfate initiator was added at a uniform rate, the temperature was raised to 70°C, and the reaction was carried out for 3 hours;

[0185] Step ②: Pour the product and solution into a rotary evaporator to remove the solvent, and place the remaining product in an oven to dry;

[0186] Step ③: Heat and dissolve the dried product with deionized water, then add 2-acrylamide-2-methylpropanesulfonic acid and acrylamide in a molar ratio of 1:1.6, pour the solution into a three-necked flask, stir at 300-400 rpm, pass nitrogen for 10-20 minutes to eliminate oxygen in the container, uniformly add 1 wt% potassium persulfate initiator (i.e., 1% of the total mass of the polymerized monomers), heat to 70°C, and react for 3 hours;

[0187] Step 4: The entire reaction process was performed in a constant-temperature water bath, ensuring a nitrogen atmosphere and stable temperature. In step 3, the total monomer concentration in the three-necked flask was 0.1 mol / L. The resulting product was polymer W1. The test results are shown in Table 1.

[0188] The obtained polymer W1 was subjected to rotary evaporation drying treatment, and the polymer W1 was detected by infrared spectroscopy analysis method, and an infrared spectrum as shown in Figure 1 was obtained. As can be seen from Figure 1, a block copolymer containing NH, C=O, and sulfonic acid structural units was obtained.

[0189] Example 2

[0190] Step ①: 2-phenoxyethyl acrylate and 2-aminoethyl methacrylate hydrochloride were dissolved in deionized water at a molar ratio of 2:0.5, the solution was poured into a three-necked flask, stirred at 300-400 rpm, and nitrogen was passed through for 10-20 minutes to remove oxygen from the container. 1 wt% (i.e., 1% of the total weight of the polymerizable monomers) of potassium persulfate initiator was added at a uniform rate, the temperature was raised to 70°C, and the reaction was carried out for 3 hours;

[0191] Step ②: Pour the product and solution into a rotary evaporator to remove the solvent, and place the remaining product in an oven to dry;

[0192] Step ③: Heat and dissolve the dried product with deionized water, then add 2-acrylamide-2-methylpropanesulfonic acid and acrylamide in a molar ratio of 1:1.6, pour the solution into a three-necked flask, stir at 300-400 rpm, pass nitrogen for 10-20 minutes to eliminate oxygen in the container, uniformly add 1 wt% potassium persulfate initiator (i.e., 1% of the total mass of the polymerized monomers), heat to 70°C, and react for 3 hours;

[0193] Step 4: The entire reaction process was carried out in a constant-temperature water bath, ensuring a nitrogen atmosphere and stable temperature. In step 3, the total monomer concentration in the three-necked flask was 0.5 mol / L. The resulting product was polymer W2. The test results are shown in Table 1.

[0194] Example 3

[0195] Step ①: 2-phenoxyethyl acrylate and 2-aminoethyl methacrylate hydrochloride were dissolved in deionized water at a molar ratio of 2:0.5, and the solution was poured into a three-necked flask. The flask was stirred at 300-400 rpm and nitrogen was passed through for 10-20 minutes to remove oxygen from the container. 1 wt% (i.e., 1% of the total weight of the polymerizable monomers) of potassium persulfate as an initiator was added at a uniform rate, and the temperature was raised to 70°C and the reaction was carried out for 3 hours.

[0196] Step ②: Pour the product and solution into a rotary evaporator to remove the solvent, and place the remaining product in an oven to dry;

[0197] Step ③: Heat and dissolve the dried product with deionized water, then add 2-acrylamide-2-methylpropanesulfonic acid and acrylamide in a molar ratio of 1:1.6, pour the solution into a three-necked flask, stir at 300-400 rpm, pass nitrogen for 10-20 minutes to eliminate oxygen in the container, uniformly add 1 wt% potassium persulfate initiator (i.e., 1% of the total mass of the polymerized monomers), heat to 70°C, and react for 3 hours;

[0198] Step 4: The entire reaction process was performed in a constant-temperature water bath, ensuring a nitrogen atmosphere and stable temperature. In step 3, the total monomer concentration in the three-necked flask was 1.0 mol / L. The resulting product was polymer W3. The test results are shown in Table 1.

[0199] Example 4

[0200] The method described in Example 1 was followed, except that the four monomers were used in a molar ratio of 2-acrylamide-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.5:1.7:3:0.7, and the total monomer concentration was maintained constant. Polymer W4 was ultimately obtained through the entire process. The test results are shown in Table 1.

[0201] Example 5

[0202] The method described in Example 2 was followed, except that the four monomers were used in a molar ratio of 2-acrylamide-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.5:1.7:3:0.7, and the total monomer concentration was maintained constant. Polymer W5 was ultimately obtained through the entire process. The test results are shown in Table 1.

[0203] Example 6

[0204] The method described in Example 3 was followed, except that the four monomers were used in a molar ratio of 2-acrylamide-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.5:1.7:3:0.7, and the total monomer concentration was maintained constant. Polymer W6 was obtained through the entire process. The test results are shown in Table 1.

[0205] Example 7

[0206] The method described in Example 1 was followed, except that the four monomers were used in a molar ratio of 2-acrylamide-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.2:1.65:2.5:0.6, and the total monomer concentration was maintained constant. Polymer W7 was obtained through the entire process. The test results are shown in Table 1.

[0207] Example 8

[0208] The method described in Example 2 was followed, except that the four monomers were used in a molar ratio of 2-acrylamido-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.2:1.65:2.5:0.6, and the total monomer concentration was maintained constant. Polymer W8 was obtained through the entire process. The test results are shown in Table 1.

[0209] Example 9

[0210] The method described in Example 3 was followed, except that the four monomers were used in a molar ratio of 2-acrylamido-2-methylpropanesulfonic acid: acrylamide: 2-phenoxyethyl acrylate: 2-aminoethyl methacrylate hydrochloride = 1.2:1.65:2.5:0.6, and the total monomer concentration was maintained constant. Polymer W9 was obtained through the entire process. The test results are shown in Table 1.

[0211] Example 10

[0212] According to the method described in Example 1, the difference is that an equal amount (ie, equal volume) of ethanol is used instead of deionized water as the solvent. After the whole process, the polymer W is finally obtained. 10 The test results are shown in Table 1.

[0213] Example 11

[0214] According to the method described in Example 1, except that an equal amount of ammonium cerium nitrate was used instead of potassium persulfate as the initiator, the polymer W was finally obtained through the whole process. 11 The test results are shown in Table 1.

[0215] Comparative Example 1

[0216] The method described in Example 1 was followed, except that an equimolar amount of sodium styrene sulfonate was used instead of 2-acrylamide-2-methylpropanesulfonic acid. Polymer D1 was finally obtained through the entire process. The test results are shown in Table 1.

[0217] Comparative Example 2

[0218] The method described in Example 1 was followed, except that ammonium persulfate was used as the initiator. The polymer D2 was obtained through the entire process. The test results are shown in Table 1.

[0219] Table 1 Properties of polymers

[0220] Test Case

[0221] Performance Testing

[0222] According to the above method, the prepared well wall stabilizer polymers W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W23, W24, W5, W6, W7, W8, W9, W10, W11, W12 10 、W 11 , D1, and D2 were prepared into an aqueous solution with a mass fraction concentration of 1%, and the single-agent performance test of the well wall stabilizer was carried out.

[0223] The bentonite rock block was pressed into a linear dilatometer, and deionized water and the polymer well wall stabilizer prepared in Examples 1-6 were added respectively. After soaking for 16 hours, the final expansion height on the linear dilatometer was read. The linear expansion test results are shown in Table 2.

[0224] Table 2 Linear expansion of polymer on bentonite block

[0225] By comparing the linear expansion height results of Examples 1-11 with deionized water in Table 2, it can be seen that the wellbore strengthening wellbore stabilizer polymer provided by the present invention has a certain inhibitory effect on the hydration expansion of bentonite. The prepared polymer can significantly reduce the expansion height of the bentonite block and effectively enhance the wellbore stability of the formation.

[0226] The cores were placed in 1% concentration of well wall stabilizer polymers W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W23, W24, W5, W6, W7, W8, W9, W11, W12 10 、W 11 The cores were immersed in solutions D1 and D2 for 24 hours, and the integrity of the cores was observed. The test results are shown in Table 3.

[0227] Table 3 State of cores after immersion in different wellbore stabilizer polymers for 24 h

[0228] It can be seen from the results in Table 3 that the wellbore strengthening wellbore stabilizer provided by the present invention has a certain degree of effect of cementing clay particles, thereby playing a role in stabilizing the wellbore wall and strengthening the wellbore.

[0229] The wellbore stabilizer prepared in this invention was formulated into a water-based drilling fluid system, with the polymer dosage at 1%. Basic properties such as fluid loss and rheological properties of each water-based drilling fluid containing the synthesized wellbore stabilizer were tested. The results of the drilling fluids' apparent viscosity (AV / mPa·s), plastic viscosity (PV / mPa·s), dynamic shear force (YP / Pa), dynamic-plastic ratio (YP / PV (Pa / mPa·s)), and medium pressure fluid loss (API / mL) are shown in Table 4.

[0230] Table 4 Effect of polymer on drilling fluid properties

[0231] As can be seen from the data in Table 4, the test results show that the water-based drilling fluid wellbore stabilizer provided by the present invention has a certain influence on the basic properties of the drilling fluid and can regulate the rheological properties of the drilling fluid. The prepared polymers with different structures have different degrees of influence on the drilling fluid.

[0232] From the data results in Tables 2-4, it can be concluded that the wellbore strengthening wellbore stabilizer provided by the present invention can improve the viscosity of the drilling fluid, effectively reduce the filtration loss, reduce the leakage of the drilling fluid during drilling work, and play a role in stabilizing the wellbore wall.

[0233] In summary, the polymer synthesized by the solution polymerization method provided by the present invention is applied to water-based drilling fluid, and the preparation of wellbore strengthening wellbore stabilizers has a very obvious effect, which can greatly improve the rheological properties and filtration loss of the drilling fluid. In addition, the preparation method is simple and the cost is low. Therefore, the present invention has a very broad application prospect, can effectively solve the problem of wellbore instability in drilling work, improve the drilling fluid's ability to inhibit the hydration and expansion of formation clay, reduce the occurrence of complex accidents underground, and bring about improved economic benefits.

[0234] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A multi-component copolymer, characterized in that: The multi-component copolymer contains structural unit A, structural unit B, structural unit C and structural unit D; wherein the structural unit A has a structure shown in formula (1); the structural unit B has a structure shown in formula (2); the structural unit C has a structure shown in formula (3); and the structural unit D has a structure shown in formula (4); In formula (1), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M is selected from hydrogen or an alkali metal; In formula (2), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group; In formula (3), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group; In formula (4), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and X is selected from halogen.

2. The multi-component copolymer according to claim 1, wherein In formula (1), R1 and R2 are each independently selected from hydrogen or a C1-C3 alkyl group; R3 is selected from a C1-C3 alkylene group; M is selected from hydrogen, sodium or potassium; and / or, in formula (2), R4 and R5 are each independently selected from hydrogen or a C1-C3 alkyl group; and / or, in formula (3), R6 and R7 are each independently selected from hydrogen or a C1-C3 alkyl group; And / or, in formula (4), R8 and R9 are each independently selected from hydrogen or a C1-C3 alkyl group.

3. The multi-component copolymer according to claim 2, wherein: In formula (1), R1 and R2 are each independently hydrogen, methyl or ethyl; R3 is methylene or 1,2-ethylene; and / or, in formula (2), R4 and R5 are each independently hydrogen, methyl, ethyl or propyl; and / or, in formula (3), R6 and R7 are each independently hydrogen, methyl, ethyl or propyl; And / or, in formula (4), R8 and R9 are each independently hydrogen, methyl, ethyl or propyl.

4. The multi-component copolymer according to claim 1 or 2, wherein The molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 0.5-2:1.4-1.8:1.5-4.2:0.3-0.

8.

5. The multi-component copolymer according to claim 1, wherein The average molecular weight of the multi-polymer is 20,000-150,000 g / mol.

6. A method for preparing a multi-component copolymer, characterized in that: The preparation method comprises: In the presence of an initiator, the polymerizable monomers are subjected to solution polymerization to obtain a multi-polymer; wherein the polymerizable monomers include: a monomer represented by formula (I), a monomer represented by formula (II), a monomer represented by formula (III) and a monomer represented by formula (IV); In formula (I), R1 and R2 are each independently selected from hydrogen or a C1-C6 alkyl group; R3 is selected from a C1-C6 alkylene group; M1 is selected from hydrogen or an alkali metal; In formula (II), R4 and R5 are each independently selected from hydrogen or a C1-C6 alkyl group; In formula (III), R6 and R7 are each independently selected from hydrogen or a C1-C6 alkyl group; In formula (IV), R8 and R9 are each independently selected from hydrogen or C1-C6 alkyl; and M2 is selected from halogen.

7. The preparation method according to claim 6, wherein: The molar 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 0.5-2:1.4-1.8:1.5-4.2:0.3-0.

8.

8. The preparation method according to claim 6 or 7, wherein: The conditions for the solution polymerization include: temperature of 30-100° C.; time of 4-8 hours.

9. The preparation method according to claim 6, wherein: The initiator is selected from one of alkyl halides, azobisisobutyronitrile, 2-ketoglutaric acid, potassium persulfate, cerium ammonium nitrate and azobisisobutyramidine hydrochloride.

10. The preparation method according to claim 5, wherein: The solution polymerization is carried out in a solvent; Wherein, the solvent is selected from one of deionized water, ethanol, methanol and dimethyl sulfoxide.

11. A multipolymer obtained by the preparation method according to any one of claims 6 to 10.

12. Use of the multi-polymer according to any one of claims 1 to 5 and 11 as a wellbore stabilizer in drilling.

13. The use according to claim 12, wherein: The multi-polymer is used as a well wall stabilizer in a wellbore reinforcement well wall.

14. A water-based drilling fluid containing the multi-polymer according to any one of claims 1 to 5 and 11 as a wellbore stabilizer.

15. The water-based drilling fluid according to claim 14, wherein: Based on the total weight of the water-based drilling fluid, the content of the multi-polymer is 1-6wt%.

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