Gel polymer, preparation method and application thereof, and water-based drilling fluid

Abstract

The invention relates to the field of drilling in the petroleum industry, and discloses a gel polymer, a preparation method and application thereof, and a water-based drilling fluid. The polymer contains a structural unit A, a structural unit B, a structural unit C and a structural unit D, the structural unit A is a structural unit with a structure as shown in a formula (1); the structural unit B is a structural unit with a structure as shown in a formula (2); the structural unit C is a structural unit with a structure as shown in a formula (3); the structural unit D is a structural unit with a structure as shown in a formula (4). The gel polymer provided by the invention can realize temperature-responsive expansion, and after the gel polymer is applied to the drilling fluid, the plugging effect and aging performance of the drilling fluid on macropores can be effectively improved. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the field of oil industry drilling, and in particular to a gel polymer and a preparation method and application thereof, and a water-based drilling fluid. Background Art

[0002] In modern oil drilling projects, high-temperature resistant water-based drilling fluids are used more and more widely. This type of drilling fluid has good rheology and lubricity, and can effectively cool the drill bit and carry cuttings. However, under high temperature and high pressure environments, the drilling process often faces leakage problems, resulting in reduced drilling efficiency and increased costs. With the increasing number of deep wells and high temperature and high pressure environments, the use of traditional drilling fluids faces many challenges. In order to solve the plugging problem in extreme high temperature environments, researchers have begun to pay attention to the application of temperature-responsive materials. Among them, expanded polymer gel plugging materials have become an important research direction due to their excellent temperature adaptability and good rheological properties.

[0003] Therefore, it is particularly important to develop an efficient plugging material. Swelling polymer gel plugging material is an ideal choice for solving this problem due to its excellent physical and chemical properties. This type of material can expand rapidly after contacting water-based drilling fluid to form a stable gel plugging layer, thereby effectively plugging cracks and pores to prevent liquid loss. Its superior high temperature resistance ensures that it can maintain a good plugging effect under extreme conditions.

[0004] In addition, expanded polymer gel-type materials generally have lower environmental impact, meet the requirements of sustainable development, and provide strong support for the safety and environmental protection of the oil and gas extraction industry.

[0005] The plugging materials commonly used at present have poor deformability and cannot form a dense plugging layer for complex cracks of varying sizes.

[0006] Compared with conventional plugging agents, the expansion polymer gel type material is not restricted by the leakage channel, and can enter the cracks and holes through extrusion deformation, and expand to plug the leakage channel, which has significant advantages. However, due to the excessive expansion rate and uncontrollable expansion multiple of common expansion gel plugging materials, they expand before reaching the leaking layer, which seriously reduces the migration and plugging capacity of the plugging materials; the existing expansion gel plugging technology has a low one-time plugging success rate, cannot effectively plug the formation pore throats and cracks, and has a poor effect.

[0007] In summary, there is an urgent need to develop responsive expanding polymer plugging materials that can expand responsively with changes in formation temperature and form a solid plugging layer under extreme operating conditions (200°C), effectively reducing the amount of leakage. This can not only improve the efficiency of drilling operations, but also effectively reduce costs and risks, which is of great significance for promoting the advancement of oil drilling technology. Summary of the invention

[0008] The purpose of the present invention is to solve the problems of poor plugging effect of macropores, poor aging performance and lack of temperature responsive expansion in the polymer gel plugging material of the prior art.

[0009] In order to achieve the above object, the first aspect of the present invention provides a gel polymer, which contains structural unit A, structural unit B, structural unit C and structural unit D; the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 1:0.5-2:0.1-1:0.05-0.5;

[0010] The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4);

[0011]

[0012]

[0013] in,

[0014] In formula (1), R 1 Selected from C 1-6 Alkylene, -R 10 -O-;R 10 Selected from C 0-6 alkylene; each R 2 Each independently selected from H, C 1-6 An alkyl group; X is a halogen element;

[0015] In formula (2), each R 3 Each independently selected from H, C 1-6 An alkyl group; M is selected from H or an alkali metal element;

[0016] In formula (3), each R 4 Each independently selected from H, C 1-6 Alkyl; R 5 Selected from C 0-6 Alkylene; R 6 Selected from H, C 1-6 The alkyl group;

[0017] In formula (4), each R 7 Each independently selected from C 0-6 alkylene; each R 8 Each independently selected from H, C 1-6 The alkyl group of each R 9Each independently selected from H, amino or C 1-6 of alkyl.

[0018] A second aspect of the present invention provides a method for preparing a gel polymer, the method comprising:

[0019] (1) Mixing monomer B' and monomer A' in a solvent and a protective atmosphere to obtain a mixture I;

[0020] (2) in the presence of a surfactant and an initiator, polymerizing the monomer C', the monomer D' and the mixture I to obtain the plugging polymer;

[0021] The monomer A' is selected from monomers having a structure shown in formula (I); the monomer B' is selected from monomers having a structure shown in formula (I I); the monomer C' is selected from monomers having a structure shown in formula (I I I); the monomer D' is selected from monomers having a structure shown in formula (IV);

[0022] The monomer A', the monomer B', the monomer C' and the monomer D' are respectively such that the prepared polymer contains the structural unit A, the structural unit B, the structural unit C and the structural unit D, and the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D in the prepared polymer is 1:0.5-2:0.1-1:0.05-0.5;

[0023] The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4);

[0024]

[0025]

[0026] Among them, the definitions of R1, R2, R3, R4, R5, R6, R7, R8, R9, M, and X are the same as those described in the first aspect.

[0027] The third aspect of the present invention provides a gel polymer prepared by the method described in the second aspect.

[0028] The fourth aspect of the present invention provides the use of the gel polymer described in the first aspect and the third aspect as a plugging agent in drilling fluid.

[0029] The fifth aspect of the present invention provides a water-based drilling fluid, wherein the water-based drilling fluid contains an effective plugging amount of the gel polymer described in the first aspect and the third aspect.

[0030] The gel polymer provided by the present invention can achieve temperature-responsive expansion, has a small volume at low temperatures, and significantly increases in volume when the temperature rises to a certain temperature, i.e., the temperature response threshold.

[0031] In particular, the gel polymer provided by the present invention can achieve slow expansion within 24 hours; the expansion effect below 150°C is maintained within 2.5 times, the expansion effect at 150°C is more than 19 times, and the expansion effect at 200°C is at least 25 times; it can responsively expand with changes in formation temperature, and can still achieve effective expansion in extreme operating environments (200°C), forming a solid plugging layer, effectively reducing the amount of leakage, greatly improving the success rate of plugging, and can also achieve precise operations in specific environments underground, reducing the difficulty of plugging caused by leakage channels such as complex cracks.

[0032] The gel polymer provided by the present invention can effectively improve the plugging effect and aging performance of the drilling fluid on large pores after being applied to the drilling fluid; it can effectively improve the plugging ability and compatibility of the drilling fluid, and can effectively plug the 2-4mm large-size seams; at the same time, it has the function of maintaining the rheological properties of the drilling fluid system. The gel polymer provided by the present invention is simple, safe and low-cost to use, and is expected to be promoted and used. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a product property diagram of the gel polymer S1 obtained in Example 1 provided by the present invention before drying (A) and after drying (B);

[0034] Figure 2 is a graph showing the relationship between time and expansion multiple under different temperature conditions for the gel polymer obtained in Example 1 provided by the present invention;

[0035] Figure 3 This is a graph showing the relationship between temperature and expansion multiple at different times for the gel polymer obtained in Example 1 provided by the present invention. DETAILED DESCRIPTION

[0036] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0037] The following provides some exemplary explanations for some groups of the present invention. Unless otherwise specified, the unlisted parts are explained with reference to the following exemplary explanations.

[0038] The "halogen element" refers to fluorine, chlorine, bromine and iodine.

[0039] “C 1-6 The term "alkyl" refers to a straight chain alkyl or branched chain alkyl having a total of 1, 2, 3, 4, 5 or 6 carbon atoms. For example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.

[0040] “C 0-6 "C0 alkylene" means a straight chain alkyl or branched alkyl group having a total of 0, 1, 2, 3, 4, 5 or 6 carbon atoms; for example, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -CH2-(CH2)2-CH2-, -C(CH3)2-CH2-, -CH2-C(CH3)2-, etc., wherein the total number of carbon atoms is 0, i.e., "C0 alkylene" means that it does not exist, and the groups at both ends of the group are directly connected; "C 1-6 The "alkylene group" has a similar definition thereto.

[0041] As mentioned above, the first aspect of the present invention provides a gel polymer, which contains structural unit A, structural unit B, structural unit C and structural unit D; the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 1:0.5-2:0.1-1:0.05-0.5;

[0042] The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4);

[0043]

[0044] In formula (1), R 1 Selected from C 1-6 Alkylene, -R 10 -O-;R 10 Selected from C 0-6 alkylene; each R 2 Each independently selected from H, C 1-6 An alkyl group; X is a halogen element;

[0045] In formula (2), each R 3 Each independently selected from H, C 1-6 An alkyl group; M is selected from H or an alkali metal element;

[0046] In formula (3), each R 4 Each independently selected from H, C1-6 Alkyl; R 5 Selected from C 0-6 Alkylene; R 6 Selected from H, C 1-6 The alkyl group;

[0047] In formula (4), each R 7 Each independently selected from C 0-6 alkylene; each R 8 Each independently selected from H, C 1-6 The alkyl group of each R 9 Each independently selected from H, amino or C 1-6 of alkyl.

[0048] Preferably, in formula (1), R 1 Selected from -CH2-, -R 10 -O-;R 10 is selected from -CH2-, -CH2-CH2-, -CH2-CH2-CH2-; each R 2 Each is independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3; X is selected from Cl, Br, I, F;

[0049] In formula (2), each R 3 Each is independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3; M is selected from H, K, Na;

[0050] In formula (3), each R 4 Each is independently selected from H, -CH2CH3, -CH2CH2CH3; R 5 Alkylene selected from C0, -CH2-, -CH2-CH2-; R 6 Selected from H, -CH3;

[0051] In formula (4), each R 7 Each R is independently selected from C0 alkylene, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-; each R 8 Each independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3, each R 9 Each is independently selected from H, -NH2, -CH3, -CH2CH3.

[0052] More preferably, the structural unit A is selected from at least one of the structural units of 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), the structure represented by formula (1-15), the structure represented by formula (1-16), the structure represented by formula (1-17), and the structure represented by formula (18);

[0053] The structural unit B is selected from at least one of the structures represented by formula (2-1), formula (2-2), formula (2-3), formula (2-4), formula (2-5), formula (2-6), formula (2-7), formula (2-8), formula (2-9), formula (2-10), formula (2-11), and formula (2-12);

[0054] The structural unit C is selected from at least one of the structural units of the structure represented by formula (3-1), the structure represented by formula (3-2), the structure represented by formula (3-3), the structure represented by formula (3-4), the structure represented by formula (3-5), the structure represented by formula (3-6), the structure represented by formula (3-7), the structure represented by formula (3-8), the structure represented by formula (3-9), the structure represented by formula (3-10), the structure represented by formula (3-11), and the structure represented by formula (3-12);

[0055] The structural unit D is selected from at least one of the structural units of the structure shown in formula (4-1), the structure shown in formula (4-2), the structure shown in formula (4-3), the structure shown in formula (4-4), the structure shown in formula (4-5), the structure shown in formula (4-6), the structure shown in formula (4-7), the structure shown in formula (4-8), the structure shown in formula (4-9), the structure shown in formula (4-10), the structure shown in formula (4-11), the structure shown in formula (4-12), the structure shown in formula (4-13), the structure shown in formula (4-14), the structure shown in formula (4-15), and the structure shown in formula (4-16);

[0056] Formula (1-1): R 1 -CH2-, R 2 All are H, X is Cl;

[0057] Formula (1-2): R 1 -CH2-, R 2 All are H, X is Br;

[0058] Formula (1-3): R 1 -CH2-, R 2 All are H, X is I;

[0059] Formula (1-4): R 1 -CH2-, R 2 All are H, X is F;

[0060] Formula (1-5): R 1 -CH2-, R 2 All are -CH3, X is Cl;

[0061] Formula (1-5): R 1 -CH2-, R 2 All are -CH3, X is Br;

[0062] Formula (1-7): R 1 -CH2-, R 2 All are -CH3, X is I;

[0063] Formula (1-8): R 1 -CH2-, R 2 All are -CH3, X is F;

[0064] Formula (1-9): R 1 -CH2-, R 2 All are -CH2CH3, X is Cl;

[0065] Formula (1-10): R 1 -CH2-, R 2 All are -CH2CH3, X is Br;

[0066] Formula (1-11): R 1 -CH2-, R 2 All are -CH2CH3, X is I;

[0067] Formula (1-12): R 1 -CH2-, R 2 All are -CH2CH3, X is F;

[0068] Formula (1-13): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is Cl;

[0069] Formula (1-14): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is Br; Formula (1-15): R 1 -CH2-, R 2All are -CH2CH2CH3, X is I; Formula (1-16): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is F; formula (1-17): Formula (1-18): Formula (2-1): R 3 All are H; M is H;

[0070] Formula (2-2): R 3 All are H; M is K;

[0071] Formula (2-3): R 3 All are H; M is Na;

[0072] Formula (2-4): R 3 All are -CH3; M is H;

[0073] Formula (2-5): R 3 All are -CH3; M is K;

[0074] Formula (2-6): R 3 All are -CH3; M is Na;

[0075] Formula (2-7): R 3 All are -CH2CH3; M is H;

[0076] Formula (2-8): R 3 All are -CH2CH3; M is K;

[0077] Formula (2-9): R 3 All are -CH2CH3; M is Na;

[0078] Formula (2-10): R 3 All are -CH2CH2CH3; M is H;

[0079] Formula (2-11): R 3 All are -CH2CH2CH3; M is K;

[0080] Formula (2-12): R 3 All are -CH2CH2CH3; M is Na;

[0081] Formula (3-1): R 4 Both H, R 5 is a C0 alkylene group, R 6 is H;

[0082] Formula (3-2): R 4 Both H, R 5 -CH2-, R 6 is H;

[0083] Formula (3-3): R 4 Both H, R 5 is -CH2-CH2-, R 6 is H;

[0084] Formula (3-4): R 4 Both H, R 5 is a C0 alkylene group, R 6 is -CH3; Formula (3-5): R 4 Both H, R 5 -CH2-, R 6 is -CH3;

[0085] Formula (3-6): R 4 Both H, R 5 is -CH2-CH2-, R 6 is -CH3;

[0086] Formula (3-7): R 4 All are -CH2CH3, R 5 is a C0 alkylene group, R 6 is H;

[0087] Formula (3-8): R 4 All are -CH2CH3, R 5 -CH2-, R 6 is H;

[0088] Formula (3-9): R 4 All are -CH2CH3, R 5 is -CH2-CH2-, R 6 is H;

[0089] Formula (3-10): R 4 All are -CH2CH2CH3, R 5 is a C0 alkylene group, R 6 is H;

[0090] Formula (3-11): R 4 All are -CH2CH2CH3, R 5 -CH2-, R 6 is H;

[0091] Formula (3-12): R 4 All are -CH2CH2CH3, R 5 is -CH2-CH2-, R 6 is H;

[0092] Formula (4-1): R 7 All are C0 alkylene, R8 Both H, R 9 All are H;

[0093] Formula (4-2): R 7 All are -CH2-, R 8 Both H, R 9 All are H;

[0094] Formula (4-3): R 7 All are -CH2-CH2-, R 8 Both H, R 9 All are H;

[0095] Formula (4-4): R 7 All are -CH2-CH2-CH2-, R 8 Both H, R 9 All are H;

[0096] Formula (4-5): R 7 are all C0 alkylene groups, R 8 All are -CH3, R 9 All are H;

[0097] Formula (4-6): R 7 All are -CH2-, R 8 All are -CH3, R 9 All are H;

[0098] Formula (4-7): R 7 All are -CH2-CH2-, R 8 All are -CH3, R 9 All are H;

[0099] Formula (4-8): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH3, R 9 All are H;

[0100] Formula (4-9): R 7 are all C0 alkylene groups, R 8 All are -CH2CH3, R 9 All are H;

[0101] Formula (4-10): R 7 All are -CH2-, R 8 All are -CH2CH3, R 9 All are H;

[0102] Formula (4-11): R 7 All are -CH2-CH2-, R 8 All are -CH2CH3, R 9All are H;

[0103] Formula (4-12): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH2CH3, R 9 All are H;

[0104] Formula (4-13): R 7 are all C0 alkylene groups, R 8 All are -CH2CH2CH3, R 9 All are H;

[0105] Formula (4-14): R 7 All are -CH2-, R 8 All are -CH2CH2CH3, R 9 All are H;

[0106] Formula (4-15): R 7 All are -CH2-CH2-, R 8 All are -CH2CH2CH3, R 9 All are H;

[0107] Formula (4-16): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH2CH2CH3, R 9 Both are H.

[0108] Preferably, the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 1:0.5-1:0.5-1:0.05-0.1. The inventors found that under this preferred specific embodiment, the gel polymer obtained by the present invention has enhanced toughness and thermal stability, and can adapt to the requirements of higher temperature environments; it can achieve a more precise water absorption and expansion effect, and adapt to the on-site requirements of different processes in oil field operations; it can improve production efficiency, reduce raw material consumption, and achieve better cost control. After being applied to drilling fluid, it has better plugging performance and aging resistance.

[0109] Preferably, the number average molecular weight of the gel polymer is 5,000-500,000.

[0110] As mentioned above, the second aspect of the present invention provides a method for preparing a gel polymer, the method comprising:

[0111] (1) Mixing monomer B' and monomer A' in a solvent and a protective atmosphere to obtain a mixture I;

[0112] (2) in the presence of a surfactant and an initiator, polymerizing the monomer C', the monomer D' and the mixture I to obtain the gel polymer;

[0113] The monomer A' is selected from monomers having a structure shown in formula (I); the monomer B' is selected from monomers having a structure shown in formula (I I); the monomer C' is selected from monomers having a structure shown in formula (I I I); the monomer D' is selected from monomers having a structure shown in formula (IV);

[0114] The monomer A', the monomer B', the monomer C' and the monomer D' are respectively such that the prepared polymer contains the structural unit A, the structural unit B, the structural unit C and the structural unit D, and the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D in the prepared polymer is 1:0.5-2:0.1-1:0.05-0.5;

[0115] The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4);

[0116]

[0117]

[0118] Among them, the definitions of R1, R2, R3, R4, R5, R6, R7, R8, R9, M, and X are the same as those described in the first aspect.

[0119] Preferably, the protective atmosphere is selected from at least one of nitrogen and argon.

[0120] Preferably, in step (1), the first mixing conditions include: temperature of 25°C-45°C, time of 0.5-2h, and stirring speed of 300-500rpm.

[0121] Preferably, the polymerization reaction is carried out under stirring conditions, and the polymerization reaction conditions include: stirring speed of 400-7000 rpm, temperature of 60-100° C., pH value of 7-9, and time of 6-24 h.

[0122] It should be noted that the pH value of 7-9 refers to the pH value of 7-9 in the initial system for the polymerization reaction. The pH value can be adjusted by conventional acid-base adjustment methods in the art. The present invention will not be elaborated here, and those skilled in the art should not understand it as a limitation of the present invention.

[0123] Preferably, the double bonds of the monomer D' all participate in the polymerization reaction, and during the polymerization process, the linear molecules can be linked together to form a cross-linked network structure, thereby increasing the strength, adjusting the physical properties of the gel polymer, and improving the chemical stability.

[0124] In the method described in the second aspect of the present invention, the relevant definitions and substance types of the substituents of the monomer of the structure represented by formula (I), the monomer of the structure represented by formula (II), the monomer of the structure represented by formula (III), and the monomer of the structure represented by formula (IV) are the same as the relevant definitions and substance types of the substituents described above in the present invention, and the present invention will not be elaborated here, and those skilled in the art should not understand it as a limitation on the technical solution of the present invention.

[0125] In the present invention, the monomer A', the monomer B', the monomer C' and the monomer D' can be purchased commercially, or synthesized according to the structural formula provided by the present invention in combination with known methods in the field of organic synthesis.

[0126] In the present invention, it should be noted that the monomer is almost completely converted into the corresponding structural unit contained in the polymer, and the amount of the monomer used can be consistent with the content of the corresponding structural unit contained in the polymer.

[0127] Preferably, the initiator is selected from at least one of an azo initiator, a peroxide initiator and a redox initiator.

[0128] More preferably, the azo initiator is selected from at least one of azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, azobiscyanovaleric acid, and azobisisopropylimidazoline; the peroxide initiator is selected from at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; and the redox initiator is selected from at least one of persulfate-sulfite, persulfate-thiourea, and persulfate-organic salt.

[0129] More preferably, based on the total mole of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the initiator is 0.02-3 mol%.

[0130] Preferably, the solvent is water.

[0131] More preferably, the amount of the solvent used is 500-1000 mL relative to 1 mol of the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D'.

[0132] Preferably, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and octadecyltrimethylammonium chloride.

[0133] More preferably, based on the total weight of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the surfactant is 0.1-1.5 wt%.

[0134] It should be noted that the method for preparing the gel polymer of the present invention also includes conventional post-processing methods, such as drying and crushing to a particle size required for application, which will not be described in detail herein and should not be construed as a limitation to the present invention by those skilled in the art.

[0135] As mentioned above, the third aspect of the present invention provides a gel polymer prepared by the method described in the second aspect.

[0136] As mentioned above, the fourth aspect of the present invention provides the use of the gel polymer described in the first aspect and the third aspect as a plugging agent in drilling fluid.

[0137] As mentioned above, the fifth aspect of the present invention provides a water-based drilling fluid, wherein the water-based drilling fluid contains an effective plugging amount of the gel polymer described in the first aspect and the third aspect.

[0138] Preferably, the water-based drilling fluid contains water, gel polymer, organic soil, pH regulator, viscosity enhancer, fluid loss reducer, lubricant, inhibitor, and rigid bridging particles;

[0139] Wherein, relative to 100 parts by weight of water, the content of the gel polymer is 1-3 parts by weight, the content of the organic soil is 1-6 parts by weight, the content of the pH adjuster is 0.1-1 parts by weight, the content of the viscosity enhancer is 1-2 parts by weight, the content of the fluid loss reducer is 2-6 parts by weight, the content of the lubricant is 1-3 parts by weight, the content of the inhibitor is 0.5-2 parts by weight, and the content of the rigid bridging particles is 1-4 parts by weight; the gel polymer is the gel polymer described in the first aspect and the third aspect.

[0140] More preferably, the organic soil is sodium-based bentonite and / or calcium-based bentonite; the pH regulator is NaOH; the fluid loss reducer is selected from at least one of carboxymethyl cellulose, potassium humate, sulfonated phenolic resin, and carboxymethyl starch; the lubricant is selected from at least one of polyols and bonding lubricants; the viscosity enhancer is selected from at least one of polyanionic cellulose, potassium polyacrylamide, and acrylamide-sodium acrylate copolymer; the inhibitor is selected from at least one of potassium chloride, sodium humate, and inorganic positive electrode glue; the rigid bridging particles are selected from at least one of fiber, fruit shell, mica, or vermiculite.

[0141] In the present invention, there is no particular limitation on the preparation method of the drilling fluid, and a preparation method known to those skilled in the art may be used, which will not be described in detail herein. In addition, the present invention lists a specific operation hereinafter, which should not be construed as a limitation on the present invention by those skilled in the art.

[0142] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials and reagents used are commercially available.

[0143] Example 1

[0144] Monomer A': (3-acrylamide propyl) trimethylammonium chloride, having a structure shown in formula (I), and having the structural formula:

[0145] Monomer B': sodium p-styrene sulfonate, having a structure shown in formula (II), and R 3 All are H, M is Na; the structural formula is:

[0146] Monomer C': N-vinyl caprolactam, having a structure shown in formula (III), and R 4 Both H, R 5 is a C0 alkylene group, R 6 is H; the structural formula is:

[0147] Monomer D': divinylbenzene, having a structure shown in formula (IV), and R 7 All are C0 alkylene, R 8 Both H, R 9 All are H; the structural formula is:

[0148] (1) In the presence of nitrogen, monomer B' and 0.5 mol of monomer A' were dissolved in water, and a first mixing was performed to obtain a mixture I; the conditions of the first mixing were: temperature of 25° C., time of 1 h, and stirring speed of 500 rpm;

[0149] (2) polymerizing the mixture I with monomer C', monomer D', an initiator (potassium persulfate), and a surfactant (sodium dodecylbenzene sulfonate), and drying the resulting product to obtain a gel polymer S1; the polymerization reaction conditions are: a stirring speed of 500 rpm, a temperature of 70° C., a pH value of 7, and a time of 12 h;

[0150] Based on the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the initiator is 1 mol%; based on the total weight of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the surfactant is 1 weight%;

[0151] Based on the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D' being 1 mol, the amount of the solvent used is 500 mL.

[0152] The molar ratio of the monomer A', the monomer B', the monomer C' and the monomer D' is 1:0.5:0.5:0.05;

[0153] The number average molecular weight of gel polymer S1 is 140,000;

[0154] The product properties of gel polymer S1 before and after drying are shown in the figure. Figure 1 (A is before drying, B is after drying).

[0155] Example 2

[0156] Monomer A': acryloyloxyethyl trimethyl ammonium bromide; having a structure shown in formula (I), the structural formula is:

[0157] Monomer B': potassium p-styrene sulfonate; having a structure shown in formula (II), and R 3 All are H, M is K; the structural formula is:

[0158] Monomer C': N-vinyl caprolactam; having a structure shown in formula (III), and R 4 Both H, R 5 is a C0 alkylene group, R 6 is H; the structural formula is:

[0159] Monomer D': divinylbenzene; having a structure represented by formula (IV), and R 7 are all C0 alkylene groups, R 8 Both H, R 9 All are H; the structural formula is:

[0160] (1) In the presence of nitrogen, monomer B' and 1 mol of monomer A' are dissolved in water, and a first mixing is performed to obtain a mixture I; the conditions of the first mixing are: temperature of 25° C., time of 1 h, and stirring speed of 500 rpm;

[0161] (2) polymerizing the mixture I with monomer C', monomer D', an initiator (potassium persulfate), and a surfactant (sodium dodecylbenzene sulfonate), and drying the resulting product to obtain a gel polymer S2; the polymerization reaction conditions are: a stirring speed of 500 rpm, a temperature of 70° C., a pH value of 7, and a time of 12 h;

[0162] Based on the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the initiator is 0.5 mol%; based on the total weight amount of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the surfactant is 0.5 weight%;

[0163] Based on the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D' being 1 mol, the amount of the solvent used is 500 mL.

[0164] The molar ratio of the monomer A', the monomer B', the monomer C' and the monomer D' is 1:1:1:0.1;

[0165] The number average molecular weight of the gel polymer S2 was 350,000.

[0166] Example 3

[0167] This example is carried out using a process similar to that of Example 1, except that in this example, the molar ratio of the monomer A', the monomer B', the monomer C' and the monomer D' is 1:2:0.5:0.05.

[0168] The rest are the same as in Example 1.

[0169] The prepared gel polymer S3 had a number average molecular weight of 220,000.

[0170] Example 4

[0171] This example is carried out using a process similar to that of Example 1, except that in this example, the molar ratio of the monomer A', the monomer B', the monomer C' and the monomer D' is 1:0.5:0.5:0.5.

[0172] The rest are the same as in Example 1.

[0173] The prepared gel polymer S4 had a number average molecular weight of 170,000.

[0174] Example 5

[0175] This example is carried out using a process similar to that of Example 1, except that in this example, the types of monomers used are different, specifically:

[0176] Monomer A': methacryloyloxyethyl trimethylammonium chloride; having a structure shown in formula (I), the structural formula is:

[0177] Monomer B': potassium p-styrene sulfonate; having a structure shown in formula (II), and R 3 All are H, M is K; the structural formula is:

[0178] Monomer C': N-vinyl caprolactam; having a structure shown in formula (III), and R 4 Both H, R 5 is a C0 alkylene group, R 6 is H; the structural formula is:

[0179] Monomer D': 1,4-diamino-2,5-divinylbenzene; having a structure shown in formula (IV), and R 7 are all C0 alkylene groups, R 8 Both H, R 9 All are -NH2; the structural formula is:

[0180] The rest are the same as in Example 1.

[0181] The prepared gel polymer S5 had a number average molecular weight of 200,000.

[0182] Comparative Example 1

[0183] This comparative example was carried out using a process similar to that of Example 1, except that monomer A' was not added in this comparative example.

[0184] The rest are the same as in Example 1.

[0185] The gel polymer DS1 was prepared.

[0186] Comparative Example 2

[0187] This comparative example was carried out using a process similar to that of Example 1, except that monomer B' was not added in this comparative example.

[0188] The rest are the same as in Example 1.

[0189] The gel polymer DS2 was prepared.

[0190] Comparative Example 3

[0191] This comparative example was carried out using a process similar to that of Example 1, except that monomer C' was not added in this comparative example.

[0192] The rest are the same as in Example 1.

[0193] The gel polymer DS3 was prepared.

[0194] Comparative Example 4

[0195] This comparative example was carried out using a process similar to that of Example 1, except that monomer D' was not added in this comparative example.

[0196] The rest are the same as in Example 1.

[0197] The gel polymer DS4 was prepared.

[0198] Comparative Example 5

[0199] This comparative example is carried out using a process similar to that of Example 1, except that in this example, the molar ratio of the monomer A', the monomer B', the monomer C' and the monomer D' is 1:3:2:0.5.

[0200] The rest are the same as in Example 1.

[0201] The gel polymer DS5 was prepared.

[0202] Test Example 1

[0203] This test example is used to illustrate the plugging performance of the gel polymer prepared in the above example.

[0204] The test method is as follows:

[0205] The gel polymer and the corresponding laboratory materials were used to prepare water-based drilling fluid plugging slurry. After hot rolling at 150°C and 180°C for 16 hours, plugging experiments were carried out at instrument temperatures of 150°C and 180°C. The specific operating steps are as follows:

[0206] Add the plugging slurry to the mud cup, raise the temperature to the set temperature, open the upper and lower valves in turn, and adjust the pressure by controlling the opening and closing of the upper valve. After the lower valve is opened, measure the instantaneous leakage volume V0, then start timing, gradually increase the pressure difference between the upper and lower valves to 6MPa at a rate of 2min / MPa, measure the initial cumulative leakage volume V1 during the first pressure increase process, and complete the conventional permeability leakage evaluation. Then close the upper and lower valves and reduce the pressure in the mud cup to 1MPa.

[0207] Under high temperature conditions of 150°C and 180°C, the gel polymer provided by the above example was added to the water-based drilling fluid (blank group), and the plugging effect of the gel polymer was tested by a 2-4mm seam plate experiment;

[0208] Among them, the blank group was: water + organic soil + pH adjuster (NaOH) + lubricant (polyethylene glycol) + thickener (polyacrylamide potassium salt) + filtration reducer (carboxymethyl cellulose) + inhibitor (potassium chloride) + rigid bridging particles (mica).

[0209] Among them, relative to 100 parts by weight of water, the content of the organic soil is 4 parts by weight, the content of the pH adjuster is 0.5 parts by weight, the content of the viscosity enhancer is 1.5 parts by weight, the content of the filtration reducer is 4 parts by weight, the content of the lubricant is 2 parts by weight, the content of the inhibitor is 1 part by weight, and the content of the rigid bridging particles is 2 parts by weight.

[0210] The test results are shown in Table 1.

[0211] Table 1

[0212]

[0213]

[0214]

[0215] It can be seen from the results in Table 1 that the gel polymer provided by the present invention is applied to water-based drilling fluid, which can better achieve the plugging effect of large-sized seam plates.

[0216] Test Example 2

[0217] This test example is used to test the expansion performance of gel polymer under different temperature aging conditions. The test method is as follows:

[0218] Weigh 5 g of gel polymer and 200 mL of deionized water into a beaker and place at room temperature (25°C) for 24 h. Record the mass change of the gel polymer before and after.

[0219] Weigh 5 g of gel polymer and 200 mL of deionized water, place them in a high-temperature reactor, and heat-roll them for 24 hours under high temperature conditions. Record the change in the mass of the gel polymer before and after.

[0220] The results are shown in Table 2.

[0221] Table 2

[0222]

[0223] From the results in Table 2, it can be seen that the gel polymer provided by the present invention can well achieve expansion performance under different temperature conditions.

[0224] The present invention also provides an exemplary relationship between the time and the expansion multiple of the gel polymer prepared in Example 1 under different temperature conditions, such as Figure 2As shown, it can be seen that the gel is suitable for the temperature range of 150-200°C. The expansion multiple is small below 150°C, less than 2.5 times in 24 hours. The expansion effect is not obvious within 4 hours, and the expansion multiple slowly increases thereafter, indicating that the particles have good delayed water absorption and expansion properties and have a slow expansion effect.

[0225] Furthermore, the present invention also provides an exemplary relationship between the temperature and the expansion multiple at different times of the gel polymer prepared in Example 1, such as Figure 3 As shown, it can be seen that the gel is suitable for the temperature range of 150-200℃, and the expansion multiple is small below 150℃. At 150℃-200℃, the polymer gel expands in a temperature-responsive manner, and the expansion multiple of 24h hot rolling is 19 times at 150℃ and 25 times at 200℃. It can meet the actual application needs and give enough time for feeding on site to achieve the purpose of entering the leaking layer.

[0226] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A gel polymer, characterized in that The polymer contains structural unit A, structural unit B, structural unit C and structural unit D; the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 1:0.5-2:0.1-1:0.05-0.5; The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4); in, In formula (1), R 1 Selected from C 1-6 Alkylene, -R 10 -O-;R 10 Selected from C 0-6 alkylene; each R 2 Each independently selected from H, C 1-6 An alkyl group; X is a halogen element; In formula (2), each R 3 Each independently selected from H, C 1-6 An alkyl group; M is selected from H or an alkali metal element; In formula (3), each R 4 Each independently selected from H, C 1-6 Alkyl; R 5 Selected from C 0-6 Alkylene; R 6 Selected from H, C 1-6 The alkyl group; In formula (4), each R 7 Each independently selected from C 0-6 alkylene; each R 8 Each independently selected from H, C 1-6 The alkyl group of each R 9 Each independently selected from H, amino or C 1-6 of alkyl.

2. The gel polymer according to claim 1, characterized in that In formula (1), R 1 Selected from -CH2-, -R 10 -O-;R 10 is selected from -CH2-, -CH2-CH2-, -CH2-CH2-CH2-; each R 2 Each is independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3; X is selected from Cl, Br, I, F; In formula (2), each R 3 Each is independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3; M is selected from H, K, Na; In formula (3), each R 4 Each is independently selected from H, -CH2CH3, -CH2CH2CH3; R 5 Alkylene selected from C0, -CH2-, -CH2-CH2-; R 6 Selected from H, -CH3; In formula (4), each R 7 Each R is independently selected from C0 alkylene, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-; each R 8 Each independently selected from H, -CH3, -CH2CH3, -CH2CH2CH3, each R 9 Each is independently selected from H, -NH2, -CH3, -CH2CH3.

3. The gel polymer according to claim 1 or 2, characterized in that The structural unit A is selected from at least one of the structural units having 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), the structure represented by formula (1-15), the structure represented by formula (1-16), the structure represented by formula (1-17), and the structure represented by formula (18); The structural unit B is selected from at least one of the structures represented by formula (2-1), formula (2-2), formula (2-3), formula (2-4), formula (2-5), formula (2-6), formula (2-7), formula (2-8), formula (2-9), formula (2-10), formula (2-11), and formula (2-12); The structural unit C is selected from at least one of the structural units of the structure represented by formula (3-1), the structure represented by formula (3-2), the structure represented by formula (3-3), the structure represented by formula (3-4), the structure represented by formula (3-5), the structure represented by formula (3-6), the structure represented by formula (3-7), the structure represented by formula (3-8), the structure represented by formula (3-9), the structure represented by formula (3-10), the structure represented by formula (3-11), and the structure represented by formula (3-12); The structural unit D is selected from at least one of the structural units of the structure shown in formula (4-1), the structure shown in formula (4-2), the structure shown in formula (4-3), the structure shown in formula (4-4), the structure shown in formula (4-5), the structure shown in formula (4-6), the structure shown in formula (4-7), the structure shown in formula (4-8), the structure shown in formula (4-9), the structure shown in formula (4-10), the structure shown in formula (4-11), the structure shown in formula (4-12), the structure shown in formula (4-13), the structure shown in formula (4-14), the structure shown in formula (4-15), and the structure shown in formula (4-16); Formula (1-1): R 1 -CH2-, R 2 All are H, X is Cl; Formula (1-2): R 1 -CH2-, R 2 All are H, X is Br; Formula (1-3): R 1 -CH2-, R 2 All are H, X is I; Formula (1-4): R 1 -CH2-, R 2 All are H, X is F; Formula (1-5): R 1 -CH2-, R 2 All are -CH3, X is Cl; Formula (1-5): R 1 -CH2-, R 2 All are -CH3, X is Br; Formula (1-7): R 1 -CH2-, R 2 All are -CH3, X is I; Formula (1-8): R 1 -CH2-, R 2 All are -CH3, X is F; Formula (1-9): R 1 -CH2-, R 2 All are -CH2CH3, X is Cl; Formula (1-10): R 1 -CH2-, R 2 All are -CH2CH3, X is Br; Formula (1-11): R 1 -CH2-, R 2 All are -CH2CH3, X is I; Formula (1-12): R 1 -CH2-, R 2 All are -CH2CH3, X is F; Formula (1-13): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is Cl; Formula (1-14): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is Br; Formula (1-15): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is I; Formula (1-16): R 1 -CH2-, R 2 All are -CH2CH2CH3, X is F; formula (1-17): Formula (1-18): Formula (2-1): R 3 All are H; M is H; Formula (2-2): R 3 All are H; M is K; Formula (2-3): R 3 All are H; M is Na; Formula (2-4): R 3 All are -CH3; M is H; Formula (2-5): R 3 All are -CH3; M is K; Formula (2-6): R 3 All are -CH3; M is Na; Formula (2-7): R 3 All are -CH2CH3; M is H; Formula (2-8): R 3 All are -CH2CH3; M is K; Formula (2-9): R 3 All are -CH2CH3; M is Na; Formula (2-10): R 3 All are -CH2CH2CH3; M is H; Formula (2-11): R 3 All are -CH2CH2CH3; M is K; Formula (2-12): R 3 All are -CH2CH2CH3; M is Na; Formula (3-1): R 4 Both H, R 5 is a C0 alkylene group, R 6 is H; Formula (3-2): R 4 Both H, R 5 -CH2-, R 6 is H; Formula (3-3): R 4 Both H, R 5 is -CH2-CH2-, R 6 is H; Formula (3-4): R 4 Both H, R 5 is a C0 alkylene group, R 6 is -CH3; Formula (3-5): R 4 Both H, R 5 -CH2-, R 6 is -CH3; Formula (3-6): R 4 Both H, R 5 is -CH2-CH2-, R 6 is -CH3; Formula (3-7): R 4 All are -CH2CH3, R 5 is a C0 alkylene group, R 6 is H; Formula (3-8): R 4 All are -CH2CH3, R 5 -CH2-, R 6 is H; Formula (3-9): R 4 All are -CH2CH3, R 5 is -CH2-CH2-, R 6 is H; Formula (3-10): R 4 All are -CH2CH2CH3, R 5 is a C0 alkylene group, R 6 is H; Formula (3-11): R 4 All are -CH2CH2CH3, R 5 -CH2-, R 6 is H; Formula (3-12): R 4 All are -CH2CH2CH3, R 5 is -CH2-CH2-, R 6 is H; Formula (4-1): R 7 are all C0 alkylene groups, R 8 Both H, R 9 All are H; Formula (4-2): R 7 All are -CH2-, R 8 Both H, R 9 All are H; Formula (4-3): R 7 All are -CH2-CH2-, R 8 Both H, R 9 All are H; Formula (4-4): R 7 All are -CH2-CH2-CH2-, R 8 Both H, R 9 All are H; Formula (4-5): R 7 are all C0 alkylene groups, R 8 All are -CH3, R 9 All are H; Formula (4-6): R 7 All are -CH2-, R 8 All are -CH3, R 9 All are H; Formula (4-7): R 7 All are -CH2-CH2-, R 8 All are -CH3, R 9 All are H; Formula (4-8): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH3, R 9 All are H; Formula (4-9): R 7 are all C0 alkylene groups, R 8 All are -CH2CH3, R 9 All are H; Formula (4-10): R 7 All are -CH2-, R 8 All are -CH2CH3, R 9 All are H; Formula (4-11): R 7 All are -CH2-CH2-, R 8 All are -CH2CH3, R 9 All are H; Formula (4-12): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH2CH3, R 9 All are H; Formula (4-13): R 7 are all C0 alkylene groups, R 8 All are -CH2CH2CH3, R 9 All are H; Formula (4-14): R 7 All are -CH2-, R 8 All are -CH2CH2CH3, R 9 All are H; Formula (4-15): R 7 All are -CH2-CH2-, R 8 All are -CH2CH2CH3, R 9 All are H; Formula (4-16): R 7 All are -CH2-CH2-CH2-, R 8 All are -CH2CH2CH3, R 9 Both are H.

4. The gel polymer according to any one of claims 1 to 3, characterized in that The molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D is 1:0.5-1:0.5-1:0.05-0.

1.

5. A method for preparing a gel polymer, characterized in that: The method includes: (1) Mixing monomer B' and monomer A' in a solvent and a protective atmosphere to obtain a mixture I; (2) in the presence of a surfactant and an initiator, polymerizing the monomer C', the monomer D' and the mixture I to obtain the gel polymer; The monomer A' is selected from monomers having a structure shown in formula (I); the monomer B' is selected from monomers having a structure shown in formula (I I); the monomer C' is selected from monomers having a structure shown in formula (I I I); the monomer D' is selected from monomers having a structure shown in formula (IV); The monomer A', the monomer B', the monomer C' and the monomer D' are respectively such that the prepared polymer contains the structural unit A, the structural unit B, the structural unit C and the structural unit D, and the molar ratio of the structural unit A, the structural unit B, the structural unit C and the structural unit D in the prepared polymer is 1:0.5-2:0.1-1:0.05-0.5; The structural unit A is a structural unit having a structure shown in formula (1); the structural unit B is a structural unit having a structure shown in formula (2); the structural unit C is a structural unit having a structure shown in formula (3); and the structural unit D is a structural unit having a structure shown in formula (4); Wherein, the definitions of R1, R2, R3, R4, R5, R6, R7, R8, R9, M, and X are the same as those in any one of claims 1 to 4.

6. The method according to claim 5, characterized in that The polymerization reaction is carried out under stirring conditions, wherein the polymerization reaction conditions include: a stirring speed of 400-7000 rpm, a temperature of 60-100° C., a pH value of 7-9, and a time of 6-24 hours; And / or, the initiator is selected from at least one of an azo initiator, a peroxide initiator and a redox initiator; Preferably, the azo initiator is selected from at least one of azobisisobutylamidine hydrochloride, azobisisopropylimidazoline hydrochloride, azobiscyanovaleric acid, and azobisisopropylimidazoline; The peroxide initiator is selected from at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate; The redox initiator is selected from at least one of persulfate-sulfite, persulfate-thiourea, and persulfate-organic salt; Preferably, based on the total molar amount of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the initiator is 0.02-3 mol%; And / or, the solvent is water.

7. The method according to claim 5 or 6, characterized in that: The surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and octadecyltrimethylammonium chloride; Preferably, based on the total weight of the monomer A', the monomer B', the monomer C' and the monomer D', the amount of the surfactant is 0.1-1.5 wt%.

8. A gel polymer prepared by the method according to any one of claims 5 to 7.

9. Use of the gel polymer according to any one of claims 1 to 4 and 8 as a plugging agent in drilling fluid.

10. A water-based drilling fluid, characterized in that: The water-based drilling fluid contains an effective plugging amount of the gel polymer according to any one of claims 1 to 4 and 8; Preferably, the water-based drilling fluid contains water, gel polymer, organic soil, pH regulator, viscosity enhancer, fluid loss reducer, lubricant, inhibitor, and rigid bridging particles; Wherein, relative to 100 parts by weight of water, the content of the gel polymer is 1-3 parts by weight, the content of the organic soil is 1-6 parts by weight, the content of the pH regulator is 0.1-1 parts by weight, the content of the viscosity enhancer is 1-2 parts by weight, the content of the fluid loss reducer is 2-6 parts by weight, the content of the lubricant is 1-3 parts by weight, the content of the inhibitor is 0.5-2 parts by weight, and the content of the rigid bridging particles is 1-4 parts by weight; the gel polymer is the gel polymer described in any one of claims 1-4 and 8.

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