Conjugated crosslinking monomer, tackifier for solid-free drilling fluid and preparation method and application of tackifier

Abstract

The invention discloses a conjugated cross-linking monomer, a tackifier for solid-free drilling fluid and a preparation method and application of the tackifier, and the conjugated cross-linking monomer has a three-dimensional alkyl structure and a conjugated diene structure and is shown in the following formula. In the presence of a catalyst, an alkenyl compound and an adamantane compound are subjected to a synthetic reaction, and the conjugated crosslinking monomer is prepared. And reacting the conjugated crosslinking monomer with alkenyl amide and alkenyl sulfonic acid to obtain the tackifier for the solid-free drilling fluid. The tackifier is used in a solid-free drilling fluid, is good in temperature resistance and salt tolerance, and can improve the suspension and rock-carrying properties of a clay-free drilling fluid system of a medium-deep well. # imgabs0 #

Description

Technical Field

[0001] The invention relates to a conjugated crosslinking monomer, a tackifier for solid-free drilling fluid, a preparation method of the tackifier for solid-free drilling fluid, and an application of the tackifier for solid-free drilling fluid, belonging to the technical field of petroleum additives. Background Art

[0002] Solid-free drilling fluid, also known as clay-free drilling fluid, is a drilling fluid system developed on the basis of low-solid drilling fluid to minimize the contamination of reservoirs by foreign solid components. This type of drilling fluid system mainly uses salt (such as NaCl, KCl, KCOOH, etc.) as a weighting material, and polymers as thickeners. Among them, polymers play a very important role in the solid-free drilling fluid system and are the key to maintaining the suspension and rock-carrying performance of the entire system. In the solid-free drilling fluid system, polymers spread and entangle with each other in the aqueous solution to form a spatial network structure, which plays an important role in maintaining the rock-carrying capacity of the drilling fluid. At present, the commonly used thickeners in the solid-free drilling fluid system mainly include biopolymers and their modified products, such as xanthan gum (XC), high viscosity carboxymethyl cellulose (HV-CMC), high viscosity polyanionic cellulose sodium salt (PAC-HV), etc.) and synthetic polymer products (such as polyacrylic acid polymers, polyacrylamide polymers, polyurethane polymers, etc.).

[0003] In recent years, in order to improve the applicability of solid-free drilling fluid in deep formations, solid-free drilling fluid systems with good temperature resistance have emerged continuously. The basis for constructing solid-free drilling fluid with excellent temperature resistance depends to a large extent on temperature-resistant thickeners. For example, in 2015, a master's thesis of Southwest Petroleum University, "Preparation of Thickeners for Formate Solid-Free Drilling Fluids and Research on Their Systems", reported a ternary polymer PADA obtained by free radical polymerization using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and methacryloyloxyethyl trimethylammonium chloride (DMC) as monomers as a thickener for solid-free drilling fluid. For a 0.6% PADA solution, when the temperature rises from 20°C to 80°C, the viscosity of the solution only decreases by 17%. The temperature resistance of the formate solid-free drilling fluid system constructed using it only reaches 120°C.

[0004] In addition, in a Chinese invention patent with publication number CN106349114B, a hydrophobic monomer and a thickener for solid-free drilling fluid based on the monomer are disclosed. A hydrophobic associating polymer obtained by polymerizing an olefin monomer containing a biphenyl structure and N-vinyl pyrrolidone is used as a thickener for solid-free drilling fluid, and its temperature resistance is only up to 150°C.

[0005] As can be seen from the above, hydrophobic associating polymers, especially hydrophobic associating polymers with rigid structural units, are more commonly used as thickeners for temperature-resistant and salt-resistant solid-free drilling fluids. At present, benzene rings and cyclohexane are generally used for the selection of rigid structural units. Summary of the invention

[0006] The first object of the present invention is to overcome the problems existing in the prior art and provide a conjugated cross-linking monomer, which can be used to prepare a hydrophobic associating polymer, which can be used as a viscosity enhancer in a solid-free drilling fluid and has good temperature and salt resistance.

[0007] In order to solve the above technical problems, a conjugated cross-linking monomer of the present invention has a stereoscopic alkyl structure and a conjugated diene structure, and the molecular formula is Formula I-1 or Formula I-2:

[0008]

[0009]

[0010] Preferably, R, R0, R1, R2, and R3 are each -H, C1-C6 alkyl, or phenyl.

[0011] Preferably, R1, R2, R3 are -H, -CH3 or phenyl, R is -H, -CH3 or phenyl, and R0 is -H, -CH3 or -CH2CH3.

[0012] The second object of the present invention is to overcome the problems existing in the prior art and provide a method for preparing a conjugated cross-linked monomer. The prepared conjugated cross-linked monomer can be used to prepare a hydrophobic associating polymer, which can be used as a thickener in a solid-free drilling fluid and has good temperature and salt resistance.

[0013] In order to solve the above technical problems, the present invention provides a method for preparing a conjugated cross-linking monomer, wherein an alkenyl compound represented by formula II-1 and an adamantane compound represented by formula II-2 or formula II-3 are subjected to a synthesis reaction in the presence of a catalyst.

[0014]

[0015]

[0016]

[0017] The molar ratio of the alkenyl compound to the adamantane compound is 1:(1.3-1.6), and the reaction yields a conjugated cross-linking monomer represented by Formula I-1 or Formula I-2.

[0018] Preferably, R, R0, R1, R2, and R3 are each -H, C1-C6 alkyl, or phenyl.

[0019] Preferably, R1, R2, R3 are -H, -CH3 or phenyl, R is -H, -CH3 or phenyl, and R0 is -H, -CH3 or -CH2CH3.

[0020] The catalyst is low-valent titanium, and the preparation method of the low-valent titanium comprises: dissolving a titanium-containing reagent and a reducing agent in a solvent A for a reduction reaction; the solvent A is tetrahydrofuran THF, and the reduction reaction is carried out under a protective atmosphere, which is nitrogen and / or argon.

[0021] Preferably, the titanium-containing reagent is at least one of TiCl3, TiCl4 or commercial titanium powder; the reducing agent is at least one of K, Li, Na, Zn+CuCl, LiAlH4, Mg, Mg+Hg, Li+Hg and chlorosilane, and the valence state of the low-valent titanium varies with the reduction activity of the reducing agent and the ratio of the amount of the reducing agent to the titanium-containing reagent.

[0022] Preferably, the titanium-containing reagent is TiCl4, and its concentration in solvent A is 0.3-0.6 mmol / mL; the reducing agent is Zn and CuCl, the concentration of Zn in solvent A is 0.3-0.6 mmol / mL, the concentration of CuCl in solvent A is 0.05-0.10 mmol / mL, and the solvent A is tetrahydrofuran THF.

[0023] Preferably, activated Zn, CuCl and solvent A are added to the reactor, and then cooled and stirred, and then TiCl4 is added to carry out the reduction reaction in a reflux manner to obtain the low-valent titanium.

[0024] Preferably, the reflux temperature is 68°C to 76°C, and cooling is performed again after reflux, the cooling temperature is -10 to 0°C, and the reflux time is 4 to 6 hours; the particle size of the activated Zn is 600 to 1000 mesh.

[0025] Preferably, the alkenyl compound and the adamantane compound are first dissolved in solvent B, and then a low-valent titanium catalyst is mixed in, and the synthesis reaction is carried out in a reflux manner under stirring conditions; the solvent B has the same composition as the solvent A, the volume ratio of solvent B: solvent A is 1: (2 to 4), and the concentration of the alkenyl compound in the solvent B is 0.3 to 0.5 mmol / mL.

[0026] Preferably, the synthesis reaction temperature is 68-76° C. and the time is 2-10 h.

[0027] Preferably, after the synthetic reaction obtains the conjugated cross-linked monomer, a quencher is added to carry out a quenching reaction, and the quencher is one or more of alkali metal cyanide, amide, borane, K2CO3, LiAlH4 and NaBH.

[0028] Preferably, the quencher is K2CO3, the concentration of the K2CO3 solution is 5wt% to 10wt%, and the volume ratio of the K2CO3 solution to the solvent B is 1:(5 to 10).

[0029] Preferably, after the reaction is quenched, filtration is performed to remove the catalyst and the filtrate is collected; and diatomaceous earth filter aid, charcoal powder filter aid, activated carbon filter aid or perlite filter aid is added during the filtration process.

[0030] Preferably, the collected filtrate is rinsed with CH2Cl2 as the rinsing solvent, and the rinse liquid is mixed with the filtrate after rinsing to obtain a mixed liquid; the mixed liquid is dried with a desiccant, filtered, and then distilled under reduced pressure to remove the solvent to obtain a light yellow crude product.

[0031] Preferably, the desiccant is an inorganic neutral desiccant, and is one or more of MgSO4, anhydrous Na2SO4, CaSO4, and CaCl2.

[0032] Preferably, the light yellow crude product is recrystallized and purified using methanol or ethanol to obtain the conjugated cross-linking monomer in the form of a light yellow paste.

[0033] Preferably, the catalyst is at least one of low-valent tungsten, low-valent molybdenum, low-valent zirconium, low-valent vanadium or low-valent niobium that can promote the coupling of carbonyl groups to olefins.

[0034] The third object of the present invention is to overcome the problems existing in the prior art and provide a thickener for solid-free drilling fluid, which can be used in solid-free drilling fluid in high-temperature wells with high mineralization or salt-gypsum formations and has good temperature and salt resistance.

[0035] In order to solve the above technical problems, the present invention provides a thickener for solid-free drilling fluid, comprising alkenyl amide A shown in formula III, alkenyl sulfonic acid B shown in formula IV and conjugated crosslinking monomer C as described in claim 1;

[0036]

[0037] The molar ratio among the three is A:B:C=(30-60):(10-30):(1-5).

[0038] Preferably, in Formula III: R 1 is -H or a C1-C6 alkyl group;

[0039] R 2 for

[0040] Among them, R a and R bEach is independently selected from -H, a C1-C6 alkyl group, a C1-C6 alkyl alcohol, and a C1-C8 alkyl ketone;

[0041] R c Selected from -H or C1-C6 alkyl;

[0042] R d Selected from -CH3, -CH2CH3, One of them.

[0043] Preferably, in Formula IV: R 3 Selected from -H or C1-C6 alkyl;

[0044] R 4 Selected from

[0045] One of them.

[0046] Preferably, for R 4 , A is selected from at least one of H, Na, K, Rb or Cs; j, k, l are integers of 0 to 3 respectively; m, n are natural numbers of 4 to 14 respectively.

[0047] The fourth object of the present invention is to overcome the problems existing in the prior art and provide a method for preparing a thickener for solid-free drilling fluid. The prepared thickener can be used in solid-free drilling fluid in high-temperature wells with high mineralization or salt-gypsum formations, and has good temperature and salt resistance.

[0048] In order to solve the above technical problems, a method for preparing a thickener for solid-free drilling fluid of the present invention comprises the following steps:

[0049] S1, sequentially mixing the alkenyl amide A, alkenyl sulfonic acid B and conjugated crosslinking monomer C in solvent C and heating to a predetermined temperature;

[0050] S2, after nitrogen is passed for 30 minutes, an initiator is added to the mixed solution, and the reaction is continued for 8 to 16 hours to obtain a crude product of a tackifier;

[0051] S3. The crude thickener product is precipitated, washed, extracted and vacuum dried to obtain a finished thickener product for solid-free drilling fluid.

[0052] Preferably, the molar ratio of the alkenyl amide, alkenyl sulfonic acid and the above-mentioned three structural conjugated cross-linking monomers is (30-60): (10-30): (1-5), the mass percentage concentration of the three structural conjugated cross-linking monomers in solvent C is 5.0%-15.0%, and the reaction temperature is 44-104°C.

[0053] Preferably, the solvent C is one or more of acetone, tetrahydrofuran, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0054] Preferably, the amount of the initiator added is 0.5% to 1.5% of the total weight of the three structural conjugated cross-linking monomers, and the initiator is one or more of an organic peroxide initiator, an inorganic peroxide initiator, and an oil-soluble redox initiator;

[0055] Alternatively, the initiator is an azo initiator, which is one or more of azobisisobutylimidazoline hydrochloride, azoisobutylcyanoformamide, azobisisobutyronitrile, azodimethyl N-2-hydroxybutylacrylamide, azobisisovaleronitrile, azobiscyanovaleric acid, azobisisobutylamidine hydrochloride, azobisisopropylimidazoline, azobisN,N'-cyclobutylisobutylamidine hydrate, azobisisobutyric acid dimethyl ester, and 2,2'-azobisN-cyclohexylisobutylamidine hydrochloride.

[0056] The fifth purpose of the present invention is to overcome the problems existing in the prior art and provide an application of a thickener for solid-free drilling fluid, which is used in solid-free drilling fluid and has good temperature and salt resistance. It can improve the suspension and rock carrying performance of the clay-free drilling fluid system in medium and deep wells and avoid contamination of the reservoir by foreign solid components.

[0057] In order to solve the above technical problems, the present invention provides an application of a thickener for solid-free drilling fluid, which comprises adding the thickener for solid-free drilling fluid as described in any one of claims 21 to 24 to the solid-free drilling fluid, or adding the thickener for solid-free drilling fluid prepared by the preparation method according to any one of claims 25 to 28; based on the total amount of the solid-free drilling fluid, the amount of the thickener added is 0.5wt% to 4.0wt%.

[0058] Compared with the prior art, the present invention has achieved the following beneficial effects: First, the conjugated cross-linking monomer of the present invention contains a diene structure, and the conjugation effect disperses the electron cloud on the double bond of the molecule, the bond length tends to be averaged, the molecular refractive index increases, the internal energy decreases, the double bond is easier to open, and the activity of the polymerization reaction increases.

[0059] Secondly, the conjugated cross-linking monomer of the present invention contains a more rigid stereoalkyl structure, which is beneficial to improving the rigidity of the target polymer, can increase the spatial volume and steric hindrance of the polymer molecular chain, reduce the degree of thermal motion of the polymer molecules under high temperature conditions, and is beneficial to improving the temperature resistance of the polymer molecules.

[0060] Third, there are excess reactants in the synthesis reaction. When the reaction proceeds to a certain extent and the target product has been obtained, if the excess reactants continue to exist, they will further react to form undesirable products. Through quenching, another compound that is more reactive with the excess compound is used to react with it, thereby removing it from the system and avoiding the appearance of impurities in the product.

[0061] Fourthly, viscosity enhancers with good temperature and salt resistance are conducive to the use of solid-free drilling fluids in high-temperature wells, high-mineralization or salt-gypsum formations, improving the suspension and rock-carrying properties of clay-free drilling fluid systems and avoiding contamination of reservoirs by foreign solid components. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0063] Figure 1 For Example 1 of the present invention 1 H NMR spectra;

[0064] Figure 2 For Example 2 of the present invention 1 H NMR spectra;

[0065] Figure 3 For Example 3 of the present invention 1 H NMR spectra;

[0066] Figure 4 For Example 4 of the present invention 1 H NMR spectra. DETAILED DESCRIPTION

[0067] In the following description of the present invention, the directions or positional relationships indicated by terms such as "up", "down", "front", "back", "left", "right", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific direction.

[0068] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0070] Example 1

[0071] Under nitrogen protection, 29.42 g, 450 mmol, 800 mesh activated Zn powder, 7.43 g, 75 mmol, CuCl and 1000 mL of THF were added to the reactor, cooled to -5 °C, stirred, 85.36 g, 450 mmol, TiCl4 was added, the temperature was raised to 72 °C and refluxed for 5 h, and then cooled to -5 °C again to obtain a low-valent titanium reducing agent.

[0072] 16.82g, 200mmol of 3-methyl-3-butene-2-one, wherein R1 and R2 are H, R and R3 are CH3, and 49.27g, 300mmol of 1-adamantane carboxaldehyde, wherein R0 is H, are dissolved in 500mL THF, then mixed into a low-valent titanium reducing agent, heated to 72°C under stirring conditions, and refluxed for 6.5h. After adding 60mL of 8.0wt% K2CO3 solution, the mixture is filtered through diatomaceous earth, the filtrate is collected, and then rinsed with CH2Cl2, and the rinse liquid is mixed with the filtrate to obtain a mixed solution.

[0073] Add sufficient amount of anhydrous Na2SO4 to the mixed solution, filter and distill under reduced pressure to remove THF to obtain a pale yellow crude product. The crude product is recrystallized from methanol to obtain a pale yellow paste, which is the target product, denoted as S1, with a yield of 59.37%.

[0074] The chemical reaction formula is as follows:

[0075]

[0076] The product obtained in Example 1 was characterized by NMR [(CD3)2SO, 25°C], and the NMR spectrum 1 H NMR Figure 1 .according to 1 The H NMR analysis results were consistent with the molecular structure of the target product.

[0077] Example 2

[0078] Under nitrogen protection, 19.614 g, 300 mmol, 1000 mesh activated Zn powder, 7.92 g, 80 mmol, CuCl and 1000 mL of THF were added to the reactor, cooled to -2 °C, stirred, 56.90 g, 300 mmol, TiCl4 was added, the temperature was raised to 76 °C, refluxed for 6 h, and cooled to -2 °C again to obtain a low-valent titanium reducing agent.

[0079] 9.91 g, 75 mmol of 2-phenylpropenal, R1, R2 and R are H, R3 is phenyl, and 19.71 g, 120 mmol of 2-adamantanecarboxaldehyde, R0 is H, are dissolved in 250 mL of THF, mixed with a low-valent titanium reducing agent, heated to 76°C under stirring, and refluxed for 7.5 h. 25 mL of 5.0 wt% K2CO3 solution is added, filtered through diatomaceous earth, the filtrate is collected, and then rinsed with CH2Cl2, and the rinse liquid is mixed with the filtrate to obtain a mixed solution.

[0080] Add enough CaSO4 to the mixture, filter and distill under reduced pressure to remove THF to obtain a pale yellow crude product. The crude product is recrystallized from methanol to obtain a pale yellow paste, which is the target product, denoted as S2, with a yield of 53.94%.

[0081] The chemical reaction formula is as follows:

[0082]

[0083] The product obtained in Example 2 was characterized by NMR [(CD3)2SO, 25°C], and the NMR spectrum 1 H NMR Figure 2 .according to 1 The H NMR analysis results were consistent with the molecular structure of the target product.

[0084] Example 3

[0085] Under nitrogen protection, 39.23 g, 600 mmol, 600 mesh activated Zn powder, 9.9 g, 100 mmol CuCl and 1000 mL THF were added to the reactor, cooled to 0 ° C, stirred, 113.81 g, 600 mmol TiCl4 was added, the temperature was raised to 68 ° C and refluxed for 4 h, and then cooled to 0 ° C again to obtain a low-valent titanium reducing agent.

[0086] 11.21 g, 200 mmol of acrolein, R, R 1 , R 2 and R 3 All of them are H, 46.35g, 260mmol of 1-adamantanone, R0 is CH3, 400mL of THF, mixed into the low-valent titanium reducing agent, heated to 68°C under stirring, and refluxed for 5h. After adding 80mL of 10.0wt% K2CO3 solution, filter through diatomaceous earth, collect the filtrate, and then rinse with CH2Cl2, the rinse liquid and the filtrate are mixed to obtain a mixed solution.

[0087] Add enough MgSO4 to the mixture, filter and distill under reduced pressure to remove THF to obtain a pale yellow crude product. The crude product is recrystallized from ethanol to obtain a pale yellow paste, which is the target product, denoted as S3, with a yield of 61.72%.

[0088] The chemical reaction formula is as follows:

[0089]

[0090] The product obtained in Example 3 was characterized by NMR [(CD3)2SO, 25°C], and the NMR spectrum 1 H NMR Figure 3 .according to 1 The H NMR analysis results were consistent with the molecular structure of the target product.

[0091] Example 4

[0092] Under argon protection, 32.69 g, 500 mmol, 750 mesh activated Zn powder, 4.95 g, 50 mmol CuCl and 1000 mL THF were added to the reactor, cooled to -10 °C, stirred, 94.84 g, 500 mmol TiCl4 was added, the temperature was raised to 70 °C and refluxed for 6 h, and then cooled to -10 °C again to obtain a low-valent titanium reducing agent.

[0093] 21.93g, 150mmol of 1-phenyl-2-butene-1-one, R1 is H, R2 and R3 are CH3, R is phenyl, and 37.44g, 210mmol of 2-adamantanone, R0 is CH3, 360mL of THF, are mixed into a low-valent titanium reducing agent, heated to 70°C under stirring conditions, and refluxed for 8h. 48mL of 7.5wt% K2CO3 solution is added, filtered through diatomaceous earth, the filtrate is collected, and then rinsed with CH2Cl2, and the rinse liquid is mixed with the filtrate to obtain a mixed solution.

[0094] Add enough CaCl2 to the mixture, filter and distill under reduced pressure to remove THF to obtain a pale yellow crude product. The crude product is recrystallized from ethanol to obtain a pale yellow paste, which is the target product, denoted as S4, with a yield of 55.52%.

[0095] The chemical reaction formula is as follows:

[0096]

[0097] The product obtained in Example 4 was characterized by NMR [(CD3)2SO, 25°C], and the NMR spectrum 1 H NMR Figure 4 .according to 1 The H NMR analysis results were consistent with the molecular structure of the target product.

[0098] Example 5

[0099] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 2-methylacrolein. Other conditions were the same as those of Example 1. The target product was denoted as S5, and the yield was 56.15%.

[0100] Example 6

[0101] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 3,4-dimethyl-3-pentene-2-one. Other conditions were the same as those of Example 1. The target product was denoted as S6 with a yield of 58.28%.

[0102] Example 7

[0103] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 3-methyl-3-pentene-2-one. Other conditions were the same as those of Example 1. The target product was denoted as S7 with a yield of 60.00%.

[0104] Example 8

[0105] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 3,3-diphenylacrolein. Other conditions were the same as those of Example 1. The target product was denoted as S8 with a yield of 61.41%.

[0106] Example 9

[0107] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 3-methyl-2-butenal. Other conditions were the same as those of Example 1. The target product was denoted as S9 with a yield of 50.64%.

[0108] Example 10

[0109] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 2,3-dimethyl-2-butenal. Other conditions were the same as those of Example 1. The target product was denoted as S10, and the yield was 53.29%.

[0110] Embodiment 11

[0111] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 3-pentene-2-one. Other conditions were the same as those of Example 1. The target product was denoted as S11, and the yield was 57.35%.

[0112] Example 12

[0113] The method of Example 1 was followed, except that 3-methyl-3-butene-2-one was replaced by 1,3-diphenyl-2-propenone. Other conditions were the same as those of Example 1. The target product was denoted as S12, and the yield was 56.84%.

[0114] Comparative Example 1

[0115] The method of Example 1 was followed, except that 1-adamantanecarboxaldehyde was replaced by lauryl aldehyde. Other conditions were the same as those of Example 1. The target product was denoted as D1, and the yield was 53.96%.

[0116] Comparative Example 2

[0117] The method of Example 1 was followed, except that 1-adamantanecarboxaldehyde was replaced by benzaldehyde. Other conditions were the same as those of Example 1. The target product was denoted as D2, and the yield was 52.11%.

[0118] Comparative Example 3

[0119] The method of Example 1 was followed, except that 1-adamantanecarboxaldehyde was replaced by cyclohexylcarboxaldehyde. Other conditions were the same as those of Example 1. The target product was denoted as D3 with a yield of 54.68%.

[0120] Embodiment 13

[0121] This example illustrates the preparation of a tackifier.

[0122] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 28.43 g, 0.4 mol of acrylamide, 41.45 g, 0.2 mol of 2-acrylamido-2-methylpropanesulfonic acid and 6.49 g, 0.03 mol of the conjugated crosslinking monomer S1 prepared in Example 1 were added to 660 mL of dimethyl sulfoxide, mixed and stirred, and the temperature was raised to 67° C.;

[0123] After nitrogen was passed through for 30 minutes, 0.76 g of azobis(N,N'-cyclobutylisobutylamidine) hydrate was added to the mixed solution, and the reaction was continued for 12 hours under stirring to obtain a crude product;

[0124] After adding 600 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor for 24 hours using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P1.

[0125] Embodiment 14

[0126] This example illustrates the preparation of a tackifier.

[0127] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 84.61 g, 0.5 mol of diacetone acrylamide, 51.55 g, 0.25 mol of sodium p-styrene sulfonate and 8.65 g, 0.04 mol of the conjugated crosslinking monomer S1 prepared in Example 1 were sequentially added to 1900 mL of N,N-dimethylacetamide, mixed and stirred, and the temperature was raised to 104°C;

[0128] After N2 was passed for 30 min, 1.6 g of azoisobutylcyanamide was added to the mixed solution and the reaction was continued for 8 h under stirring to obtain a crude product;

[0129] After adding 1200 mL of anhydrous ethanol for precipitation, filter it, wash the product with acetone three times, and then extract the product with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol with a volume ratio of 3:2 as the extractant for 24 hours. Dry it in a vacuum at 25°C to constant weight to obtain a viscosity enhancer recorded as P2.

[0130] Embodiment 15

[0131] This example illustrates the preparation of a tackifier.

[0132] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 33.95 g, 0.3 mol of N-isopropylacrylamide, 69.69 g, 0.3 mol of potassium 3-prop-2-enoyloxypropane-1-sulfonate and 10.82 g, 0.05 mol of the conjugated crosslinking monomer S1 prepared in Example 1 were added to 1000 mL of 1,4-dioxane, mixed and stirred, and the temperature was raised to 67° C.;

[0133] After nitrogen was passed through for 30 min, 0.57 g of azobisisovaleronitrile was added to the mixed solution, and the reaction was continued for 16 h under stirring to obtain a crude product;

[0134] After adding 600 mL of anhydrous ethanol for precipitation, filter it, wash the product with acetone three times, and then extract the product with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol with a volume ratio of 3:2 as the extractant for 24 hours. Dry it in a vacuum at 25°C to constant weight to obtain a viscosity enhancer recorded as P3.

[0135] Example 16

[0136] This example illustrates the preparation of a tackifier.

[0137] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 59.48 g, 0.3 mol of N-vinyl-N-methylacetamide, 115.6 g, 0.3 mol of sodium 2-acrylamidooctane sulfonate and 10.82 g, 0.01 mol of the conjugated crosslinking monomer S1 prepared in Example 1 were added to 1065 mL of N,N-dimethylformamide, mixed and stirred, and the temperature was raised to 66°C;

[0138] After nitrogen was passed through for 30 min, 2.66 g of dimethyl azobisisobutyrate was added to the mixed solution, and the reaction was continued for 12 h under stirring to obtain a crude product;

[0139] After adding 600 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant for 24 hours. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P4.

[0140] Embodiment 17

[0141] This example illustrates the preparation of a tackifier.

[0142] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 29.74 g, 0.3 mol of N-ethylacrylamide, 15.82 g, 0.1 mol of sodium methyl propylene sulfonate and 10.82 g, 0.05 mol of the conjugated crosslinking monomer S1 prepared in Example 1 were added to 1130 mL of N,N-dimethylformamide, mixed and stirred, and the temperature was raised to 86°C;

[0143] After nitrogen was passed through for 30 min, 0.45 g of azodimethyl N-2-hydroxybutyl acrylamide was added to the mixed solution, and the reaction was continued for 10.5 h under stirring to obtain a crude product;

[0144] After adding 500 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant for 24 hours. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P5.

[0145] Embodiment 18

[0146] This example illustrates the preparation of a tackifier.

[0147] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 103.93 g, 0.6 mol of N,N-bis(2-hydroxyethyl)methacrylamide, 39.85 g, 0.1 mol of sodium 2-acryloyloxyhexadecylsulfonate and 2.64 g, 0.01 mol of the conjugated crosslinking monomer S2 prepared in Example 2 were added to 3125 mL of tetrahydrofuran, mixed and stirred, and the temperature was raised to 44° C.;

[0148] After N2 was passed through for 30 min, 1.2 g of azobisisobutylimidazoline hydrochloride was added to the mixed solution, and the reaction was continued for 16 h under stirring to obtain a crude product;

[0149] After adding 1000 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for 3 times. The product was extracted with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant for 24 hours. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P6.

[0150] Embodiment 19

[0151] This example illustrates the preparation of a tackifier.

[0152] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 29.79 g, 0.35 mol of N-vinyl acetamide, 39.54 g, 0.25 mol of sodium methyl propylene sulfonate and 5.29 g, 0.02 mol of the conjugated crosslinking monomer S2 prepared in Example 2 were added to 800 mL of dimethyl sulfoxide, mixed and stirred, and the temperature was raised to 52° C.;

[0153] After nitrogen was passed through for 30 minutes, 0.8 g of 2,2'-azobis(N-cyclohexylisobutylamidine) hydrochloride was added to the mixed solution, and the reaction was continued for 15 hours under stirring to obtain a crude product;

[0154] After adding 500 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant for 24 hours. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P7.

[0155] Embodiment 20

[0156] This example illustrates the preparation of a tackifier.

[0157] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 58.12 g, 0.35 mol of N-(2-hydroxypropyl)acrylamide, 44.16 g, 0.18 mol of potassium 2-acrylamido-2-methylpropanesulfonate and 7.93 g, 0.03 mol of the conjugated crosslinking monomer S2 prepared in Example 2 were added to 1200 mL of dimethyl sulfoxide, mixed and stirred, and the temperature was raised to 69° C.;

[0158] After nitrogen was passed through for 30 min, 0.82 g of azobiscyanovaleric acid was added to the mixed solution, and the reaction was continued for 10 h under stirring to obtain a crude product;

[0159] After adding 500 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor for 24 hours using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P8.

[0160] Embodiment 21

[0161] This example illustrates the preparation of a tackifier.

[0162] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 60.66 g, 0.6 mol of N-hydroxymethyl acrylamide, 43.24 g, 0.3 mol of sodium allyl sulfonate and 2.02 g, 0.01 mol of the conjugated crosslinking monomer S3 prepared in Example 3 were added to 860 mL of dimethyl sulfoxide, mixed and stirred, and the temperature was raised to 56° C.;

[0163] After nitrogen was passed through for 30 min, 0.53 g of azobisisobutylamidine hydrochloride was added to the mixed solution, and the reaction was continued for 8 h under stirring to obtain a crude product;

[0164] After adding 800 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor for 24 hours using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P9.

[0165] Embodiment 22

[0166] This example illustrates the preparation of a tackifier.

[0167] In a reactor equipped with a temperature control device, a reflux condenser and a constant pressure feeding device, 56.49 g, 0.4 mol of N,N-diethylmethacrylamide, 57.83 g, 0.25 mol of potassium 3-prop-2-enamidopropane-1-sulfonate and 5.57 g, 0.02 mol of the conjugated crosslinking monomer S4 prepared in Example 4 were added to 1200 mL of N,N-dimethylacetamide, mixed and stirred, and the temperature was raised to 61°C;

[0168] After nitrogen was passed through for 30 min, 0.72 g of azodiisopropylimidazoline was added to the mixed solution, and the reaction was continued for 12 h under stirring to obtain a crude product;

[0169] After adding 850 mL of anhydrous ethanol for precipitation, the product was filtered and washed with acetone for three times. The product was extracted with a Soxhlet extractor using a mixed solvent of glacial acetic acid and ethylene glycol in a volume ratio of 3:2 as an extractant for 24 hours. The product was vacuum dried at 25°C to constant weight to obtain a viscosity enhancer, which was recorded as P10.

[0170] Embodiment 23

[0171] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S5. Other conditions are the same as those of Example 13, and the target product is recorded as P11.

[0172] Embodiment 24

[0173] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S6. Other conditions are the same as those of Example 13, and the target product is recorded as P12.

[0174] Embodiment 25

[0175] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S7. Other conditions are the same as those of Example 13, and the target product is recorded as P13.

[0176] Embodiment 26

[0177] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S8. Other conditions are the same as those of Example 13, and the target product is recorded as P14.

[0178] Embodiment 27

[0179] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S9. Other conditions are the same as those of Example 13, and the target product is recorded as P15.

[0180] Embodiment 28

[0181] The method of Example 13 was followed, except that the conjugated cross-linking monomer S1 was replaced by a conjugated cross-linking monomer S10. Other conditions were the same as those of Example 13, and the target product was recorded as P16.

[0182] Embodiment 29

[0183] The method of Example 13 was followed, except that the conjugated cross-linking monomer S1 was replaced by a conjugated cross-linking monomer S11. Other conditions were the same as those of Example 13, and the target product was recorded as P17.

[0184] Embodiment 30

[0185] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer S12. Other conditions are the same as those of Example 13, and the target product is recorded as P18.

[0186] Comparative Example 4

[0187] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer D1. Other conditions are the same as those of Example 13, and the target product is recorded as K1.

[0188] Comparative Example 5

[0189] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer D2. Other conditions are the same as those of Example 13, and the target product is recorded as K2.

[0190] Comparative Example 6

[0191] The method of Example 13 is followed, except that the conjugated cross-linking monomer S1 is replaced by the conjugated cross-linking monomer D3. Other conditions are the same as those of Example 13, and the target product is recorded as K3.

[0192] Test Example 1

[0193] Temperature resistance test

[0194] Dissolve P1-P18 and K1-K3 in water to prepare a viscosity enhancer solution with a mass percentage concentration of 0.6%. Place it in a roller heating furnace and age it at different temperatures for 16 hours. After taking it out, cool it to room temperature and stir it at a speed of 2000r / min for 5 minutes. According to the test steps specified in GB / T 16783.1-2014 "Drilling Fluid Field Test Part 1: Water-based Drilling Fluid", a six-speed rotary viscometer is used to measure the apparent viscosity AV of different experimental slurries. The test results are shown in Table 1.

[0195] Table 1 AV (mPa·s) of experimental pulp at different aging temperatures

[0196]

[0197] It can be seen from Table 1 that under room temperature conditions, the AV of each experimental pulp is not much different; with the increase of aging temperature, the AV of the experimental pulp gradually decreases; after high-temperature aging, under the same aging temperature conditions, compared with the AV of the experimental pulp containing K1~K3, the AV of the experimental pulp containing P1~P18 is higher, indicating that P1~P18 has good temperature resistance.

[0198] Test Example 2

[0199] Salt resistance test

[0200] Dissolve P1~P18 and K1~K3 in water or NaCl solution of a certain concentration to prepare a viscosity enhancer solution with a mass percentage concentration of 0.6%. Refer to the test steps specified in GB 12005.1-89 "Determination of intrinsic viscosity of polyacrylamide", use the one-point method to measure the intrinsic viscosity of different experimental pulps at 30°C, the intrinsic viscosity of the experimental pulp in water is recorded as η0, and the intrinsic viscosity of the experimental pulp in NaCl solution is recorded as η1. Calculate the retention rate of the intrinsic viscosity Δ according to the following formula:

[0201]

[0202] The test results are shown in Table 2.

[0203] Table 2 Δ(%) of viscosity enhancers in NaCl solutions of different concentrations

[0204]

[0205] It can be seen from Table 2 that as the NaCl concentration increases, the Δ of the experimental pulp decreases continuously. Under the same NaCl concentration condition, compared with the Δ of the experimental pulp containing K1 to K3, the Δ of the experimental pulp containing P1 to P18 is higher, indicating that P1 to P18 has good salt resistance.

[0206] There is no particular limitation on the preparation methods not mentioned in the present invention, and the preparation methods known to those skilled in the art may be used, which will not be described in detail in the present invention. The present invention lists specific operations in the text, which should not be construed by those skilled in the art as limitations of the present invention.

[0207] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A conjugated cross-linking monomer, characterized in that: It has a stereoscopic alkyl structure and a conjugated diene structure, and the molecular formula is Formula I-1 or Formula I-2:

2. The conjugated cross-linking monomer according to claim 1, characterized in that: R, R0, R1, R2, and R3 are each independently -H, C1-C6 alkyl, or phenyl.

3. The conjugated cross-linking monomer according to claim 2, characterized in that: R1, R2, R3 are -H, -CH3 or phenyl, R is -H, -CH3 or phenyl, and R0 is -H, -CH3 or -CH2CH3.

4. A method for preparing a conjugated cross-linking monomer, characterized in that: In the presence of a catalyst, the alkenyl compound represented by formula II-1 and the adamantane compound represented by formula II-2 or formula II-3 are subjected to a synthesis reaction. The molar ratio of the alkenyl compound to the adamantane compound is 1:(1.3-1.6), and the reaction yields a conjugated cross-linking monomer represented by Formula I-1 or Formula I-2.

5. The method for preparing a conjugated cross-linking monomer according to claim 4, characterized in that: R, R0, R1, R2, and R3 are each independently -H, C1-C6 alkyl, or phenyl.

6. The method for preparing a conjugated cross-linking monomer according to claim 5, characterized in that: R1, R2, R3 are -H, -CH3 or phenyl, R is -H, -CH3 or phenyl, and R0 is -H, -CH3 or -CH2CH3.

7. The method for preparing a conjugated cross-linking monomer according to claim 4, characterized in that: The catalyst is low-valent titanium, and the preparation method of the low-valent titanium comprises: dissolving a titanium-containing reagent and a reducing agent in a solvent A for a reduction reaction; the solvent A is tetrahydrofuran THF, and the reduction reaction is carried out under a protective atmosphere, which is nitrogen and / or argon.

8. The method for preparing a conjugated cross-linking monomer according to claim 7, characterized in that: The titanium-containing reagent is at least one of TiCl3, TiCl4 or commercial titanium powder; the reducing agent is at least one of K, Li, Na, Zn+CuCl, LiAlH4, Mg, Mg+Hg, Li+Hg and chlorosilane, and the valence state of the low-valent titanium varies with the reduction activity of the reducing agent and the ratio of the amount of the reducing agent to the titanium-containing reagent.

9. The method for preparing a conjugated cross-linking monomer according to claim 8, characterized in that: The titanium-containing reagent is TiCl4, and its concentration in solvent A is 0.3-0.6 mmol / mL; the reducing agent is Zn and CuCl, and the concentration of Zn in solvent A is 0.3-0.6 mmol / mL, and the concentration of CuCl in solvent A is 0.05-0.10 mmol / mL, and the solvent A is tetrahydrofuran THF.

10. The method for preparing a conjugated cross-linking monomer according to claim 9, characterized in that: Activated Zn, CuCl and solvent A are added into the reactor, and then after cooling and stirring, TiCl4 is added to carry out the reduction reaction in a reflux manner to obtain the low-valent titanium.

11. The method for preparing a conjugated cross-linking monomer according to claim 10, characterized in that: The reflux temperature is 68° C. to 76° C., and cooling is performed again after reflux, the cooling temperature is -10 to 0° C., and the reflux time is 4 to 6 hours; the particle size of the activated Zn is 600 to 1000 meshes.

12. The method for preparing a conjugated cross-linking monomer according to claim 7, characterized in that: The alkenyl compound and the adamantane compound are first dissolved in solvent B, and then a low-valent titanium catalyst is mixed in, and the synthesis reaction is carried out in a reflux manner under stirring conditions; the solvent B has the same composition as the solvent A, the volume ratio of solvent B: solvent A is 1: (2-4), and the concentration of the alkenyl compound in the solvent B is 0.3-0.5 mmol / mL.

13. The method for preparing a conjugated cross-linking monomer according to claim 12, characterized in that: The temperature of the synthesis reaction is 68-76° C. and the time is 2-10 hours.

14. The method for preparing a conjugated cross-linking monomer according to claim 4, characterized in that: After the synthetic reaction obtains the conjugated cross-linked monomer, a quencher is added to carry out a quenching reaction. The quencher is one or more of alkali metal cyanide, amide, borane, K2CO3, LiAlH4 and NaBH.

15. The method for preparing a conjugated cross-linking monomer according to claim 14, characterized in that: The quencher is K2CO3, the concentration of the K2CO3 solution is 5wt% to 10wt%, and the volume ratio of the K2CO3 solution to the solvent B is 1:(5 to 10).

16. The method for preparing a conjugated cross-linking monomer according to claim 15, characterized in that: After the reaction is quenched, filtration is performed to remove the catalyst and the filtrate is collected; during the filtration process, diatomaceous earth filter aid, charcoal powder filter aid, activated carbon filter aid or perlite filter aid is added.

17. The method for preparing a conjugated cross-linking monomer according to claim 16, characterized in that: The collected filtrate is rinsed with CH2Cl2 as the rinsing solvent, and the rinse liquid is mixed with the filtrate to obtain a mixed liquid; the mixed liquid is dried with a desiccant, filtered, and then distilled under reduced pressure to remove the solvent to obtain a light yellow crude product.

18. The method for preparing a conjugated cross-linking monomer according to claim 17, characterized in that: The desiccant is an inorganic neutral desiccant, and is one or more of MgSO4, anhydrous Na2SO4, CaSO4, and CaCl2.

19. The method for preparing a conjugated cross-linking monomer according to claim 17, characterized in that: The light yellow crude product is recrystallized and purified using methanol or ethanol to obtain the conjugated cross-linking monomer in the form of a light yellow paste.

20. The method for preparing a conjugated cross-linking monomer according to claim 4, characterized in that: The catalyst is at least one of low-valent tungsten, low-valent molybdenum, low-valent zirconium, low-valent vanadium or low-valent niobium that can promote the coupling of carbonyl groups to olefins.

21. A thickener for solid-free drilling fluid, characterized in that: Containing alkenyl amide A represented by formula III, alkenyl sulfonic acid B represented by formula IV and conjugated crosslinking monomer C as described in claim 1; The molar ratio among the three is A:B:C=(30-60):(10-30):(1-5).

22. The thickener for solid-free drilling fluid according to claim 21, characterized in that: In formula III: R 1 is -H or a C1-C6 alkyl group; R 2 for Among them, R a and R b Each is independently selected from -H, a C1-C6 alkyl group, a C1-C6 alkyl alcohol, and a C1-C8 alkyl ketone; R c Selected from -H or C1-C6 alkyl; R d Selected from -CH3, -CH2CH3, One of them.

23. The thickener for solid-free drilling fluid according to claim 21, characterized in that: In Formula IV: R 3 Selected from -H or C1-C6 alkyl; R 4 Selected from One of them.

24. The solid-free drilling fluid viscosity enhancer according to claim 23, characterized in that: For R 4 , A is selected from at least one of H, Na, K, Rb or Cs; j, k, l are integers of 0 to 3 respectively; m, n are natural numbers of 4 to 14 respectively.

25. A method for preparing a thickener for solid-free drilling fluid, characterized in that: The steps are as follows: S1, sequentially mixing the alkenyl amide A, alkenyl sulfonic acid B and conjugated crosslinking monomer C in solvent C and heating to a predetermined temperature; S2, after nitrogen is passed for 30 minutes, an initiator is added to the mixed solution, and the reaction is continued for 8 to 16 hours to obtain a crude product of a tackifier; S3. The crude thickener product is precipitated, washed, extracted and vacuum dried to obtain a finished thickener product for solid-free drilling fluid.

26. The method for preparing a thickener for solid-free drilling fluid according to claim 25, characterized in that: The molar ratio of the alkenyl amide, alkenyl sulfonic acid and the above-mentioned three structural conjugated cross-linking monomers is (30-60): (10-30): (1-5), the mass percentage concentration of the three structural conjugated cross-linking monomers in solvent C is 5.0%-15.0%, and the reaction temperature is 44-104°C.

27. The method for preparing a thickener for solid-free drilling fluid according to claim 25, characterized in that: The solvent C is one or more of acetone, tetrahydrofuran, 1,4-dioxane, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

28. The method for preparing a thickener for solid-free drilling fluid according to claim 25, characterized in that: The amount of the initiator added is 0.5% to 1.5% of the total weight of the three structural conjugated cross-linking monomers, and the initiator is one or more of an organic peroxide initiator, an inorganic peroxide initiator, and an oil-soluble redox initiator; Alternatively, the initiator is an azo initiator, which is one or more of azobisisobutylimidazoline hydrochloride, azoisobutylcyanoformamide, azobisisobutyronitrile, azodimethyl N-2-hydroxybutylacrylamide, azobisisovaleronitrile, azobiscyanovaleric acid, azobisisobutylamidine hydrochloride, azobisisopropylimidazoline, azobisN,N'-cyclobutylisobutylamidine hydrate, azobisisobutyric acid dimethyl ester, and 2,2'-azobisN-cyclohexylisobutylamidine hydrochloride.

29. An application of a thickener for solid-free drilling fluid, characterized in that: Add the solid-free drilling fluid thickener as described in any one of claims 21 to 24, or add the solid-free drilling fluid thickener prepared by the preparation method according to any one of claims 25 to 28; based on the total amount of the solid-free drilling fluid, the added amount of the thickener is 0.5wt% to 4.0wt%.

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