A water-based drilling fluid and its preparation method

Abstract

The present invention discloses an aqueous drilling fluid and a preparation method thereof, belonging to the technical field of drilling fluids. The aqueous drilling fluid comprises the following raw materials in parts by weight: deionized water: 100 parts, bentonite: 4 - 8 parts, inhibitor: 1 - 3 parts, lubricant: 1 - 5 parts; filtration reducer: 0.5 - 5 parts, barite powder: 5 - 40 parts, plugging agent: 1 - 5 parts, sodium hydroxide: 0.5 - 1 part; the lubricant is first prepared by reacting 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid with tris(3-aminopropyl)amine to generate a hyperbranched intermediate, and then reacting with 1-octadecene. The drilling fluid prepared by the present invention has excellent lubricating performance, reduces the wear of drill pipes and other drilling tools, and at the same time has good plugging performance.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and particularly to an aqueous drilling fluid and a preparation method thereof. Background Art

[0002] In recent years, with the decreasing of oil reserves in shallow underground layers, the drilling proportion of complex process wells such as extended reach long horizontal wells, directional wells, cluster wells and ultra-deep wells has been increasing continuously. The lubricating performance of lubricants in ordinary aqueous drilling fluid systems is difficult to meet the requirements. Compared with oil-based drilling fluids, aqueous drilling fluids have the advantages of environmental protection and low cost, and are the main drilling fluid systems used currently and in the future. However, their lubricating performance is poor, which severely restricts their popularization and use in complex structure wells such as extended reach wells and horizontal wells. By adding lubricants to aqueous drilling fluids, the lubricating performance of the system can be significantly improved. Lubricant molecules can adsorb between the drill string and the wellbore wall, and between the drill string and the casing, greatly reducing friction, torque and drag.

[0003] Developing new high-performance lubricants for aqueous drilling fluids that can meet the requirements of wellbore stability and friction and drag reduction in the directional section, and replacing traditional lubricants such as emulsified paraffin, asphalt, diesel oil and white oil, has become a key technical requirement for promoting efficient resource development.

[0004] Chinese Patent Application No. CN119161275A discloses a lubricant additive and its preparation method, a lubricant, an aqueous drilling fluid and its preparation method. The lubricant additive uses sulfonamide groups as active adsorption groups and can be stably adsorbed on the drill string, casing and filter cake. At the same time, it has two C16 flexible chains and can form a dense lubricating film to efficiently reduce friction resistance, but its lubricating performance is poor. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an aqueous drilling fluid and a preparation method thereof.

[0006] An aqueous drilling fluid comprises the following raw materials in parts by weight:

[0007] Deionized water: 100 parts,

[0008] Bentonite: 4 - 8 parts,

[0009] Inhibitor: 1 - 3 parts,

[0010] Lubricant: 1 - 5 parts,

[0011] Filtrate reducer: 0.5 - 5 parts,

[0012] Barite powder: 5 - 40 parts,

[0013] Plugging agent: 1 - 5 parts,

[0014] Sodium hydroxide: 0.5 - 1 part;

[0015] The lubricant is first prepared by reacting 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid with tris(3-aminopropyl)amine to form a hyperbranched intermediate, and then reacting with 1-octadecene.

[0016] The lubricant is prepared by the following method:

[0017] M1: Under nitrogen protection, N-methylpyrrolidone, pyridine, triphenyl phosphite, 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and tris(3-aminopropyl)amine are mixed evenly, heated to 100 - 150 °C, and reacted for 10 - 15 h. After treatment, a hyperbranched intermediate is obtained. The reaction equation is shown as follows:

[0018] It should be noted that the reaction equation for generating the hyperbranched intermediate below is only used to represent the reaction between the functional groups in this step.

[0019]

[0020] M2: Under nitrogen protection, N-methylpyrrolidone, triethylamine, the hyperbranched intermediate and 1-octadecene are mixed evenly, heated to 80 - 90 °C, and reacted for 6 - 10 h. After treatment, a lubricant is obtained. Among them, the amino group of the hyperbranched intermediate and the carbon-carbon double bond of 1-octadecene undergo a Michael addition reaction under the catalysis of triethylamine to form a lubricant.

[0021] In step M1, the molar ratio of the fed pyridine, triphenyl phosphite, 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and tris(3-aminopropyl)amine is (4 - 6):(2 - 3):1:(1 - 1.3).

[0022] In step M2, the mass ratio of the evenly mixed fed triethylamine, hyperbranched intermediate and 1-octadecene is (2 - 3):10:(5 - 10).

[0023] The plugging agent is prepared by the following method:

[0024] N1: Under nitrogen protection, N-methyl-2-pyrrolidone, 10-undecenoic acid and N,N'-carbonyldiimidazole are stirred and mixed evenly for activation, and then the activated 10-undecenoic acid reacts with 2,2'-bis-sulfonic acid benzidine to obtain an amide monomer. The reaction equation is shown as follows:

[0025]

[0026] N2: Stir and mix deionized water, amide monomer, and 2-acrylamido-2-methylpropanesulfonic acid evenly. Adjust the pH to neutral with sodium hydroxide solution. Add acrylamide and heat up to 60 °C. Add ammonium persulfate and react (radical polymerization of monomers with 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and amide monomer) to obtain a plugging agent.

[0027] The inhibitor is one of white asphalt and polyethylene glycol.

[0028] The filtration reducer is one of sodium carboxymethyl cellulose and sulfomethylated phenolic resin.

[0029] A preparation method of an aqueous drilling fluid includes the following steps:

[0030] S1: Weigh by parts by weight: deionized water: 100 parts; bentonite: 4 - 8 parts; inhibitor: 1 - 3 parts; lubricant: 1 - 5 parts; filtration reducer: 0.5 - 5 parts; barite powder: 5 - 40 parts; plugging agent: 1 - 5 parts; sodium hydroxide: 0.5 - 1 part;

[0031] S2: Mix and stir deionized water and bentonite to form a uniform base slurry. Sequentially add the inhibitor, lubricant, filtration reducer, plugging agent, and sodium hydroxide under stirring, stir fully for 0.5 - 1 h, add barite powder and stir for 20 - 30 min to obtain the aqueous drilling fluid.

[0032] Due to the above technical solutions, the beneficial effects of the present invention include:

[0033] (1) In the present invention, a lubricant is prepared by reacting 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid with tris(3-aminopropyl)amine to generate a hyperbranched intermediate, and then reacting with 1-octadecene. The hyperbranched structure of the lubricant adsorbs at multiple points to isolate the drill string from the wellbore wall, improving the lubrication effect. In addition, long carbon chain molecules are densely distributed and vertically extended on the friction surface to form a "molecular brush", further improving the boundary lubrication ability.

[0034] (2) In the present invention, a plugging agent is prepared by reacting 2,2'-bis(sulfonic acid)benzidine with 10-undecenoic acid to generate an amide monomer, and then reacting with acrylamide and 2-acrylamido-2-methylpropanesulfonic acid. The plugging agent utilizes the rigid structure of the benzene ring and the hydration effect of sulfonic acid groups to improve the high-temperature resistance and plugging ability of the plugging agent. Detailed Embodiments

[0035] The following is further described in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0036] Example 1 Preparation of Lubricant

[0037] M1: Under nitrogen protection, 1000 ml of N-methylpyrrolidone, 4 mol of pyridine, 2 mol of triphenyl phosphite, 1 mol of 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and 1 mol of tris(3-aminopropyl)amine were successively added into a reaction flask, stirred and mixed evenly, heated to 100 °C, reacted for 15 h, cooled to room temperature, 500 ml of deionized water was added to precipitate a solid, filtered, washed with 300 ml of deionized water, and vacuum dried at 50 °C for 24 h to obtain a hyperbranched intermediate;

[0038] M2: Under nitrogen protection, 800 ml of N-methylpyrrolidone, 20 g of triethylamine, 100 g of hyperbranched intermediate and 50 g of 1-octadecene were successively added into a reaction flask, stirred and mixed evenly, heated to 80 °C, reacted for 10 h, cooled to room temperature, the reaction solution was distilled under reduced pressure at 70 °C for 3 h, 300 ml of deionized water was added to precipitate a solid, stirred for 30 min, filtered, washed with 300 ml of deionized water, and vacuum dried at 60 °C for 24 h to obtain a lubricant.

[0039] Example 2 Preparation of Lubricant

[0040] M1: Under nitrogen protection, 1000 ml of N-methylpyrrolidone, 5 mol of pyridine, 2.6 mol of triphenyl phosphite, 1 mol of 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and 1.2 mol of tris(3-aminopropyl)amine were successively added into a reaction flask, stirred and mixed evenly, heated to 120 °C, reacted for 13 h, cooled to room temperature, 500 ml of deionized water was added to precipitate a solid, filtered, washed with 300 ml of deionized water, and vacuum dried at 50 °C for 24 h to obtain a hyperbranched intermediate;

[0041] M2: Under nitrogen protection, 800 ml of N-methylpyrrolidone, 25 g of triethylamine, 100 g of hyperbranched intermediate and 80 g of 1-octadecene were successively added into a reaction flask, stirred and mixed evenly, heated to 85 °C, reacted for 8 h, cooled to room temperature, the reaction solution was distilled under reduced pressure at 70 °C for 3 h, 300 ml of deionized water was added to precipitate a solid, stirred for 30 min, filtered, washed with 300 ml of deionized water, and vacuum dried at 60 °C for 24 h to obtain a lubricant.

[0042] Example 3 Preparation of Lubricant

[0043] M1: Under nitrogen protection, 1000 ml of N-methylpyrrolidone, 6 mol of pyridine, 3 mol of triphenyl phosphite, 1 mol of 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid, and 1.3 mol of tris(3-aminopropyl)amine were successively added to a reaction flask, stirred and mixed evenly, heated to 150 °C, reacted for 10 h, cooled to room temperature, 500 ml of deionized water was added to precipitate a solid, filtered, washed with 300 ml of deionized water, and vacuum dried at 50 °C for 24 h to obtain a hyperbranched intermediate;

[0044] M2: Under nitrogen protection, 800 ml of N-methylpyrrolidone, 30 g of triethylamine, 100 g of hyperbranched intermediate, and 100 g of 1-octadecene were successively added to a reaction flask, stirred and mixed evenly, heated to 90 °C, reacted for 6 h, cooled to room temperature, the reaction solution was distilled under reduced pressure at 70 °C for 3 h, 300 ml of deionized water was added to precipitate a solid, stirred for 30 min, filtered, washed with 300 ml of deionized water, and vacuum dried at 60 °C for 24 h to obtain a lubricant.

[0045] Example 4 Preparation of Plugging Agent

[0046] N1: Under nitrogen protection, 1000 ml of N-methyl-2-pyrrolidone, 2 mol of 10-undecenoic acid, and 2.5 mol of N,N-carbonyldiimidazole were mixed evenly, stirred and activated for 1.5 h, heated to 50 °C, 1 mol of 2,2'-bis-sulfonic acid benzidine was added and reacted for 6 h, cooled to room temperature, 400 ml of deionized water was added to precipitate a solid, filtered, washed with deionized water twice (300 ml each time), and vacuum dried at 60 °C for 24 h to obtain an amide monomer; the data of its nuclear magnetic resonance hydrogen spectrum are as follows: 1 H NMR (500 MHz,Chloroform-d) δ 10.47 (s, 2H), 9.32 (s, 2H), 8.09 (d, J=2.1 Hz, 2H), 7.93 (d,J=8.2 Hz, 2H), 7.53 (dd, J=8.2, 2.1 Hz, 2H), 5.77 (ddt, J=17.1, 10.3, 6.8 Hz,2H), 5.17-5.10 (m, 2H), 4.99-4.91 (m, 2H), 2.33 (t, J=8.3 Hz, 4H), 2.03 (tdt,J=8.0, 6.8, 1.4 Hz, 4H), 1.74-1.64 (m, 4H), 1.40-1.30 (m, 8H), 1.28 (qt, J=4.0, 2.1 Hz, 12H).

[0047] N2: Add 800 ml of deionized water, 0.1 mol of amide monomer, and 0.4 mol of 2-acrylamido-2-methylpropanesulfonic acid into a reaction flask in sequence, stir and mix evenly, adjust the pH to 7 using 10 wt% sodium hydroxide solution, add 1 mol of acrylamide, heat up to 60 °C, stir for 1 h, add 0.05 mol of ammonium persulfate, react for 3 h, cool to room temperature, dropwise add 500 ml of absolute ethanol to precipitate crystals, filter, and dry in vacuum at 50 °C for 24 h to obtain the plugging agent.

[0048] Example 5 Preparation of water-based drilling fluid

[0049] S1: Weigh by weight parts: deionized water: 100 parts; bentonite: 4 parts; white asphalt: 1 part; lubricant (prepared in Example 1): 1 part; sodium carboxymethyl cellulose: 0.5 part; barite powder: 5 parts; plugging agent (prepared in Example 4): 1 part; sodium hydroxide: 0.5 part;

[0050] S2: Mix and stir deionized water and bentonite to form a uniform base slurry, and sequentially add white asphalt, lubricant, sodium carboxymethyl cellulose, plugging agent, and sodium hydroxide under stirring, stir fully for 0.5 h, add barite powder and stir for 20 min to obtain the improved anti-collapse drilling fluid.

[0051] Example 6 Preparation of water-based drilling fluid

[0052] S1: Weigh by weight parts: deionized water: 100 parts; bentonite: 6 parts; white asphalt: 2 parts; lubricant (prepared in Example 2): 3.6 parts; sulfomethylated phenolic resin: 4 parts; barite powder: 32 parts; plugging agent (prepared in Example 4): 4.2 parts; sodium hydroxide: 0.6 part;

[0053] S2: Mix and stir deionized water and bentonite to form a uniform base slurry, and sequentially add white asphalt, lubricant, sulfomethylated phenolic resin, plugging agent, and sodium hydroxide under stirring, stir fully for 1 h, add barite powder and stir for 30 min to obtain the improved anti-collapse drilling fluid.

[0054] Example 7 Preparation of water-based drilling fluid

[0055] S1: Weigh by weight parts: deionized water: 100 parts; bentonite: 8 parts; polyethylene glycol: 3 parts; lubricant (prepared in Example 3): 5 parts; sulfomethylated phenolic resin: 5 parts; barite powder: 40 parts; plugging agent (prepared in Example 4): 5 parts; sodium hydroxide: 1 part;

[0056] S2: Mix and stir deionized water and bentonite to form a uniform base slurry, and sequentially add polyethylene glycol, lubricant, sulfomethylated phenolic resin, plugging agent, and sodium hydroxide under stirring, stir fully for 1 h, add barite powder and stir for 30 min to obtain the improved anti-collapse drilling fluid.

[0057] Comparative Example 1

[0058] The preparation method of the water-based drilling fluid is basically the same as that of Example 6, except that the lubricant (prepared in Example 2) is replaced with an equal mass of hyperbranched intermediate (prepared in Example 2).

[0059] Comparative Example 2

[0060] The preparation method of the water-based drilling fluid is basically the same as that of Example 6, except that the lubricant (prepared in Example 2) is replaced with an equal mass of lubricant prepared by the following method:

[0061] M1: Under nitrogen protection, 1000 ml of N-methylpyrrolidone, 5 mol of pyridine, 2.6 mol of triphenyl phosphite, 1 mol of 4,5-dihydroxyoctanedioic acid and 1.2 mol of tris(3-aminopropyl)amine were successively added to the reaction flask, stirred and mixed evenly, heated to 120 °C, reacted for 13 h, cooled to room temperature, 500 ml of deionized water was added to precipitate solids, filtered, washed with 300 ml of deionized water, and vacuum dried at 50 °C for 24 h to obtain a hyperbranched intermediate;

[0062] M2: Under nitrogen protection, 800 ml of N-methylpyrrolidone, 25 g of triethylamine, 100 g of hyperbranched intermediate and 80 g of 1-octadecene were successively added to the reaction flask, stirred and mixed evenly, heated to 85 °C, reacted for 8 h, cooled to room temperature, the reaction solution was distilled under reduced pressure at 70 °C for 3 h, 300 ml of deionized water was added to precipitate solids, stirred for 30 min, filtered, washed with 300 ml of deionized water, and vacuum dried at 60 °C for 24 h to obtain a lubricant.

[0063] Comparative Example 3

[0064] The preparation method of the water-based drilling fluid is basically the same as that of Example 6, except that the lubricant (prepared in Example 2) is replaced with an equal mass of lubricant prepared by the following method:

[0065] M1: Under nitrogen protection, 1000 ml of N-methylpyrrolidone, 5 mol of pyridine, 2.6 mol of triphenyl phosphite, 1 mol of 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and 1.2 mol of tris(3-aminopropyl)amine were successively added to the reaction flask, stirred and mixed evenly, heated to 120 °C, reacted for 13 h, cooled to room temperature, 500 ml of deionized water was added to precipitate solids, filtered, washed with 300 ml of deionized water, and vacuum dried at 50 °C for 24 h to obtain a hyperbranched intermediate;

[0066] M2: Under nitrogen protection, 800 ml of N-methylpyrrolidone, 25 g of triethylamine, 100 g of hyperbranched intermediate, and 80 g of octadecyl acrylate were successively added to a reaction flask, stirred and mixed evenly, heated to 85 °C, reacted for 8 h, cooled to room temperature, the reaction solution was distilled under reduced pressure at 70 °C for 3 h, 300 ml of deionized water was added to precipitate solids, stirred for 30 min, filtered, washed with 300 ml of deionized water, and vacuum dried at 60 °C for 24 h to obtain a lubricant.

[0067] Comparative Example 4

[0068] The preparation method of the water-based drilling fluid was basically the same as that of Example 6, except that the plugging agent (prepared in Example 4) was replaced with a plugging agent prepared by the following method in an equal mass:

[0069] 800 ml of deionized water, 0.1 mol of N,N-methylenebisacrylamide, and 0.4 mol of 2-acrylamido-2-methylpropanesulfonic acid were successively added to a reaction flask, stirred and mixed evenly, the pH was adjusted to 7 using a 10 wt% sodium hydroxide solution, 1 mol of acrylamide was added, heated to 60 °C, stirred for 1 h, 0.05 mol of ammonium persulfate was added, reacted for 3 h, cooled to room temperature, 500 ml of absolute ethanol was added dropwise to precipitate crystals, filtered, and vacuum dried at 50 °C for 24 h to obtain a plugging agent.

[0070] Comparative Example 5

[0071] The preparation method of the water-based drilling fluid was basically the same as that of Example 6, except that the plugging agent (prepared in Example 4) was replaced with a plugging agent prepared by the following method in an equal mass:

[0072] The preparation method of the plugging agent was basically the same as that of Example 4, except that 10-undecenoic acid in step N1 was replaced with an equimolar amount of acrylic acid.

[0073] Comparative Example 6

[0074] The preparation method of the water-based drilling fluid was basically the same as that of Example 6, except that the plugging agent (prepared in Example 4) was replaced with a plugging agent prepared by the following method in an equal mass:

[0075] The preparation method of the plugging agent was basically the same as that of Example 4, except that 2,2'-bis-sulfonic acid benzidine in step N1 was replaced with an equimolar amount of 4,4'-diaminobiphenyl.

[0076] In the examples and comparative examples of this application, the bentonite model used is SUPBENT-LD, purchased from Hangzhou Xihe Chemical Co., Ltd.; the white asphalt model is LATISEAL®, purchased from Shaker (Tianjin) Petroleum Technology Service Co., Ltd.; the molecular weight of polyethylene glycol is 20,000; the model of sodium carboxymethyl cellulose is PAC-HV, purchased from Shandong Weifang Lite Composite Materials Co., Ltd.; the model of sulfonated methyl phenolic resin is SMP-II, purchased from Henan Jinma Petroleum Technology Co., Ltd.; the barite powder model is BARITE4.3, purchased from Shaker (Tianjin) Petroleum Technology Service Co., Ltd.; the English name of 4,5-dihydroxy-octanedioic acid is 4,5-dihydroxy-octanedioic acid, CAS: 102812-69-1.

[0077] An aging test was carried out on the water-based drilling fluids prepared in Examples 5-7 and Comparative Examples 1-6 of this application: the drilling fluids were placed in a roller heating furnace and aged at 180 °C for 16 h, and then taken out and cooled to room temperature.

[0078] The water-based drilling fluids prepared in Examples 5-7 and Comparative Examples 1-6 of this application and the aged water-based drilling fluids were tested for lubrication coefficient according to the method of SY / T 6094-1994 Evaluation Procedure for Lubricants for Drilling Fluids (applying a pressure of 150 psi on the torque arm and maintaining a rotational speed of 60 r / min). The experimental results were compared with the lubrication coefficient of the drilling fluid without adding lubricant to obtain the lubrication coefficient reduction rate. The test results are shown in Table 1.

[0079] The improved anti-collapse drilling fluids prepared in Examples 5-7 and Comparative Examples 1-6 of this application were tested for fluid loss (FL API / ml) and high-temperature and high-pressure fluid loss (FL HTHP / ml, 200 °C × 16 h) according to GB / T 16783.1-2006. The test results are shown in Table 1.

[0080] Table 1 Performance test data table

[0081]

[0082] It can be seen from the data of Examples 5, 6, and 7 in Table 1 that the water-based drilling fluid prepared by the present invention has excellent lubrication performance and plugging performance.

[0083] The lubricant prepared in this application is a hyperbranched lubricant with long-chain alkyl groups. The molecular chains of the long-chain alkyl groups are relatively long, and the intermolecular van der Waals forces are relatively strong, making it easy to form a closely arranged lubricating film. It adsorbs on the friction surface through polar end groups, thereby reducing the friction coefficient. Under the action of shear force, the long-chain molecules of the lubricant tend to be arranged in parallel to form a layered structure, and the molecular layers slide through weak intermolecular forces, significantly reducing the friction coefficient. The entanglement effect between long-chain alkyl molecules can enhance the viscosity of the lubricant, and a thicker oil film can be formed under high pressure (hydrodynamic lubrication effect), avoiding metal contact under boundary lubrication conditions. Moreover, the long-chain structure has high thermal stability and is not easily broken or oxidized and decomposed at high temperatures, which can maintain the continuity of the lubricating film. However, the lubricant in Comparative Example 1 does not introduce long-chain alkyl groups, so its lubrication performance is relatively low.

[0084] The lubricant used in Comparative Example 2 is a lubricant synthesized by replacing 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid with 4,5-dihydroxyoctanedioic acid, and its lubrication performance and lubrication performance after high-temperature aging are relatively poor. The benzene ring in the lubricant used in this application has a conjugation effect, which can enhance the acidity of the hydroxyl group, making it easy to dissociate H + to form negatively charged active sites and enhance the adsorption ability. Moreover, the benzene ring structure endows high thermal stability and still maintains the adsorption performance at high temperatures. However, the hydroxyl groups in 4,5-dihydroxyoctanedioic acid used in Comparative Example 2 are easily decomposed by heat, and the adsorption ability decreases significantly with increasing temperature, thus affecting its lubrication performance.

[0085] The lubricant used in Comparative Example 3 is a lubricant synthesized by replacing 1-octadecene with octadecyl acrylate. The ester group in octadecyl acrylate is prone to hydrolysis or oxidation reactions under high-temperature conditions, destroying the integrity of the lubricating film and affecting the lubrication effect.

[0086] In the plugging agent prepared in this application, the benzene ring, as a rigid structure, can enhance the pressure-bearing strength of the plugging agent and improve its high-temperature resistance. The sulfonic acid group on the benzene ring can absorb water and swell, and can adapt to the size and shape of the formation through deformation, enhancing the plugging ability; introducing long-chain alkyl groups increases the flexibility of the plugging agent and plugs leakage channels of different shapes, thereby reducing leakage; the amide monomer has two double bonds, and the plugging agent obtained after its polymerization can form a network structure rather than a linear structure. The network structure can provide certain elasticity, enabling it to adapt to the deformation and pressure changes of the formation, dynamically adjust the integrity of the plugging layer, and thus maintain high-efficiency plugging performance in complex formations; introducing acrylamide enhances its adsorption ability and improves the binding force with clay particles; introducing 2-acrylamido-2-methylpropanesulfonic acid further enhances its hydration effect and improves its plugging effect on pore fractures.

[0087] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. However, for those of ordinary skill in the art, without departing from the scope of the technical solution of the present invention, any equivalent changes such as slight modifications, evolutions made by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A water-based drilling fluid, characterized in that, It includes raw materials in the following parts by weight: Deionized water: 100 parts, Bentonite: 4 - 8 parts, Inhibitor: 1 - 3 parts, Lubricant: 1 - 5 parts, Filtrate reducer: 0.5 - 5 parts, Barite powder: 5 - 40 parts, Plugging agent: 1 - 5 parts, Sodium hydroxide: 0.5 - 1 part; The lubricant is prepared by the following method: M1: Under nitrogen protection, N-methylpyrrolidone, pyridine, triphenyl phosphite, 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and tris(3-aminopropyl)amine are mixed evenly, heated to 100 - 150 °C, reacted for 10 - 15 h, and post-treated to obtain a hyperbranched intermediate; M2: Under nitrogen protection, N-methylpyrrolidone, triethylamine, the hyperbranched intermediate and 1-octadecene are mixed evenly, heated to 80 - 90 °C, reacted for 6 - 10 h, and post-treated to obtain the lubricant; In step M1, the molar ratio of the fed pyridine, triphenyl phosphite, 4,4'-dihydroxy-3,3'-biphenyldicarboxylic acid and tris(3-aminopropyl)amine is (4 - 6):(2 - 3):1:(1 - 1.3); In step M2, the mass ratio of the fed triethylamine, the hyperbranched intermediate and 1-octadecene is (2 - 3):10:(5 - 10); The plugging agent is prepared by the following method: N1: Under nitrogen protection, N-methyl-2-pyrrolidone, 10-undecenoic acid, and N,N'-carbonyldiimidazole are stirred and mixed evenly for activation, and then the activated 10-undecenoic acid reacts with 2,2'-bis-sulfonic acid benzidine to obtain an amide monomer; N2: Deionized water, the amide monomer, and 2-acrylamido-2-methylpropanesulfonic acid are stirred and mixed evenly, the pH is adjusted to neutral with a sodium hydroxide solution, acrylamide is added, heated to 60 °C, and ammonium persulfate is added for reaction to obtain the plugging agent.

2. The water-based drilling fluid according to claim 1, wherein, The inhibitor is one of white asphalt and polyethylene glycol.

3. A water-based drilling fluid according to claim 1, characterized in that, The filtrate reducer is one of sodium carboxymethyl cellulose and sulfomethylated phenolic resin.

4. A method for preparing the water-based drilling fluid according to any one of claims 1-3, characterized in that, It includes the following steps: S1: Weigh by parts by weight: deionized water: 100 parts, bentonite: 4 - 8 parts, inhibitor: 1 - 3 parts, lubricant: 1 - 5 parts, filtrate reducer: 0.5 - 5 parts, barite powder: 5 - 40 parts, plugging agent: 1 - 5 parts, sodium hydroxide: 0.5 - 1 part; S2: Mix and stir deionized water and bentonite to form a uniform base slurry, and successively add the inhibitor, lubricant, filtrate reducer, plugging agent and sodium hydroxide under stirring, stir well for 0.5 - 1 h, add barite powder and stir for 20 - 30 min to obtain an aqueous drilling fluid.

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