A temperature-resistant and salt-tolerant wall stabilizer for a water-based drilling fluid for a ten-thousand-meter deep well and a preparation method and application thereof

Abstract

The application provides a temperature-resistant and salt-resistant wall stabilizer for a ten-thousand-meter deep well water-based drilling fluid and a preparation method and application thereof, and belongs to the technical field of drilling. The preparation method of the wall stabilizer comprises the following steps: acrylic acid is added into deionized water, the pH of the system is adjusted to 7.0, then N-hydroxymethyl acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, an emulsifier, octadecyl vinyl ether and a complexing agent are sequentially added into the system, shearing is performed, a monomer solution is obtained, an initiator is added into the monomer solution, and reaction is performed; after the reaction is completed, washing, drying and crushing are performed, and the wall stabilizer is obtained. The wall stabilizer has a temperature resistance of 200 DEG C and a salt resistance of saturation, has strong adsorption and high cohesion, can effectively adsorb, plug and cement micro-pores and micro-cracks of rocks, thereby consolidating the rocks, effectively enhancing the well wall stability, preventing drilling fluid leakage and providing technical support for safe and efficient drilling of deep wells.

Description

Technical Field

[0001] The invention relates to a temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well, a preparation method and application thereof, and belongs to the technical field of drilling. Background Art

[0002] Drilling fluid is the lifeblood of drilling operations, lubricating the drill bit, cleaning the bottomhole, balancing formation pressure, and maintaining wellbore stability. Safe and efficient drilling requires the support of high-performance drilling fluid. Deep and ultra-deep formations experience the complex and harsh conditions of high temperature, high pressure, and high salinity. Especially when drilling into highly permeable sandstone, conglomerate, naturally fractured carbonate formations, and weakly cemented, brittle shale formations, water-based drilling fluid can easily penetrate the formation through rock pores and fractures, causing formation hydration and wellbore instability, leading to complex downhole accidents such as well collapse, stuck drill bit, and borehole reduction.

[0003] Currently, chemical cementing agents have become a key treatment agent for stabilizing wellbore walls. Chinese patent document CN117986520A discloses an environmentally friendly lignin-based strong cementing agent, prepared from 4,4′-diphenylmethane diisocyanate and lignin. The agent contains hydrophilic and hydrophobic groups such as hydroxyl groups and benzene rings, which can effectively repel water molecules between the agent and the rock, and form a three-dimensional network structure through hydrogen bonds, van der Waals forces, and hydrophobic interactions, thereby improving the bonding strength between the agent and the rock. However, because lignin contains easily hydrolyzed ether bonds, the agent has a temperature resistance of only 150°C. Chinese patent document CN116589632A discloses a high-temperature-resistant, low-viscosity hyperbranched agent prepared from dipentaerythritol hexaacrylate, polyethylene glycol diacrylate, glycine, 3-aminopropane sulfonic acid, and tannic acid. The hydrophobic skeleton formed by the ester bonds and benzene rings in the wall-fixing agent quickly aggregates and forms agglomerates, which repel water molecules between the wall-fixing agent and the rock particles. This reduces the destructive effect of free water molecules on the rock's cementation and effectively bonds the rock. Because the ester group is easily hydrolyzed at high temperatures, this wall-fixing agent is only resistant to temperatures of 180°C.

[0004] Chinese patent document CN115093837A discloses a wall-fixing agent, which is compounded from redispersible latex powder, rubber, thermosetting resin, epoxy resin, chloroprene latex, and nano-silica, and has a temperature resistance of only 120°C. Chinese patent document CN115057967A discloses a microgel chemical wall-fixing agent, which is prepared by reverse emulsion polymerization of cellulose, polyacrylamide, and xanthan gum macromolecules with vinyl monomers such as acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and acrylates. Cellulose, polyacrylamide, xanthan gum, and acrylates have poor heat resistance, and the wall-fixing agent has a temperature resistance of only 180°C. Chinese patent document CN116063991A discloses an adhesive cementing wall-fixing agent for shale formations, which is composed of an adhesive wall-protecting agent, a cementing wall-fixing agent, and a accelerator. The adhesive cementing agent is a polymer of styrene, butyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid, a cationic structuring agent, and a crosslinking agent. The cementing agent is alginate, at least one of modified alginate, propylene glycol alginate, acrylic acid, polyacrylic acid, and methacrylic acid. The accelerator is at least one of calcium chloride, magnesium chloride, calcium sulfate, and magnesium sulfate. The main component of the cementing agent is alginate, a polysaccharide compound that decomposes violently above 100°C. Therefore, the adhesive cementing agent has a temperature resistance of only 120°C. Chinese patent document CN111748330A discloses a water-based drilling fluid cementing agent prepared by free radical polymerization of acrylamide, a binder, dimethyldiallylammonium chloride, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. The binder is at least one of vinyl alcohols, vinyl esters, polyvinyl alcohol, vinyl alcohol, vinyl acetate, and diethyl acetate. This wall solidifying agent can effectively increase viscosity, improve shear strength, and reduce filtration loss, but its temperature resistance is only 150°C.

[0005] Although the aforementioned wall-fixing agents can achieve a cementing effect, their temperature resistance is insufficient and cannot meet the drilling requirements under high-temperature conditions of 200°C. Therefore, it is urgent to develop a cementing wall-fixing agent with a temperature resistance of up to 200°C to support the smooth drilling of deep and ultra-deep wells. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, especially the technical problem that the existing wall fixing agents have insufficient temperature resistance and cannot effectively maintain the stability of the well wall in high-temperature (200°C) formations, the present invention provides a temperature-resistant and salt-resistant wall fixing agent for water-based drilling fluids in 10,000-meter deep wells, and a preparation method and application thereof, and in particular provides a temperature-resistant and salt-resistant, strong adsorption, and high cohesion cementing wall fixing agent for water-based drilling fluids in 10,000-meter deep wells, and a preparation method and application thereof.

[0007] The technical solutions of the present invention are as follows:

[0008] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0009] (1) Acrylic acid is added to deionized water, and the pH of the system is adjusted to 7.0. Then, N-hydroxymethyl acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, an emulsifier, octadecyl vinyl ether, and a complexing agent are sequentially added to the system, and shearing is performed to uniformly disperse the monomers to obtain a monomer solution;

[0010] (2) Adding an initiator to the monomer solution to carry out a reaction; after the reaction is completed, washing, drying, and crushing are performed to obtain a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid.

[0011] According to the preferred embodiment of the present invention, the mass ratio of deionized water to acrylic acid in step (1) is 60-120:5-10.

[0012] According to the preferred embodiment of the present invention, in step (1), sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 7.

[0013] According to the preferred embodiment of the present invention, the mass ratio of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, N-hydroxymethylacrylamide, acrylic acid and octadecyl vinyl ether in step (1) is 5-10:10-20:5-10:1-5.

[0014] Preferably, according to the present invention, the emulsifier in step (1) is any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, Tween 80, and Span 80; and the mass ratio of the emulsifier to octadecyl vinyl ether is 0.01-0.03:1-5.

[0015] According to the preferred embodiment of the present invention, the complexing agent in step (1) is ferric chloride hexahydrate, zinc chloride, magnesium chloride or calcium chloride; and the mass ratio of the complexing agent to N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is 0.3-0.8:5-10.

[0016] According to the preferred embodiment of the present invention, the shearing rate in step (1) is 1500-2500 rpm, and the shearing time is 10-30 min.

[0017] According to a preferred embodiment of the present invention, the N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide in step (1) is prepared according to the following method:

[0018] 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is added to methanol and stirred until the solid is dissolved to obtain solution 1; acryloyl chloride is added to tetrahydrofuran and stirred to dissolve to obtain solution 2; triethylamine is added to methanol and stirred evenly to obtain solution 3; solution 2 and solution 3 are dropwise added to solution 1, and after the dropwise addition is complete, the mixture is reacted to obtain N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide.

[0019] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the mass ratio of methanol to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride in solution 1 is 70-130:8-15.

[0020] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the mass ratio of acryloyl chloride to tetrahydrofuran in solution 2 is 4.5-6.5:4.2-5.5.

[0021] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the mass ratio of triethylamine to methanol in solution 3 is 13-18:20-35.

[0022] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the mass ratio of acryloyl chloride to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is 4-6:10-15; the mass ratio of triethylamine to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is 1-2:1.

[0023] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, solution 2 and solution 3 are simultaneously added dropwise to solution 1 at 0-5° C. for 15-20 minutes.

[0024] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the reaction temperature is 20-30° C., the reaction time is 5-7 h, and the reaction is carried out under a nitrogen atmosphere.

[0025] Preferably, in the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, after the reaction is completed, a post-treatment step is further included, specifically as follows: removing the solvent from the obtained reaction solution, adding ethyl acetate, washing the organic phase with a mixed solution containing HCl and NaCl, drying over anhydrous sodium sulfate, filtering, and removing the solvent, and vacuum drying the obtained product at 100-110°C to constant weight to obtain N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide; the mass ratio of HCl to NaCl in the mixed solution is 7-9:10-12, and the concentration of HCl in the mixed solution is 0.5-1.5 mol / L.

[0026] According to the present invention, preferably, the initiator in step (2) is a composition of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride, wherein the mass ratio of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride is 5-8:2-4:8-12, and the mass ratio of the initiator to N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is 0.15-0.25:5-10.

[0027] According to the preferred embodiment of the present invention, the reaction temperature in step (2) is 70-80°C, and the reaction time is 5-7h; the washing is performed 2-3 times using methanol, and the drying is performed at 70-80°C to constant weight.

[0028] The present invention also provides a temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well, which is prepared by the above-mentioned preparation method.

[0029] According to the present invention, the application of the above-mentioned heat-resistant and salt-resistant wall-solidifying agent for 10,000-meter deep well water-based drilling fluid in water-based drilling fluid is used to stabilize the well wall and prevent leakage; the mass concentration of the heat-resistant and salt-resistant wall-solidifying agent for 10,000-meter deep well water-based drilling fluid in the water-based drilling fluid is 1-3wt%.

[0030] The technical features and beneficial effects of the present invention are as follows:

[0031] 1. The heat-resistant and salt-resistant wall-fixing agent of the present invention is a strong adsorption and high cohesion cementing wall-fixing agent, which is prepared by free radical copolymerization of acrylamide special monomer modified by catechol group and N-hydroxymethyl acrylamide, acrylic acid, and octadecyl vinyl ether, and contains highly polar hydroxyl, amide, catechol group and highly hydrophobic long alkyl chain. Hydroxyl, carboxyl and catechol groups can strongly adhere to the rock surface through adsorption effects such as hydrogen bonds, π-π interactions, coordination bonds, and covalent bonds. The highly hydrophobic long alkyl chain can repel water molecules between the wall-fixing agent and the rock surface, thereby enhancing the adhesion of the wall-fixing agent to the rock. At the same time, the catechol group, carboxyl and hydroxyl groups of the wall-fixing agent can form a stable coordination complex with a chelating agent, and the wall-fixing agent molecular chain is appropriately cross-linked, giving the cementing wall-fixing agent a strong cohesive force, thereby effectively exerting an excellent cementing and wall-fixing effect in a water environment.

[0032] 2. Under the synergistic effect of hydroxyl, carboxyl, catechol groups and long alkyl chains, the wall-solidifying agent of the present invention has a temperature resistance of up to 200°C and a salt resistance of up to saturation. Under high temperature and high salt conditions, it can adsorb, seal and cement the micropores and microcracks inside the rock, consolidate the rock, maintain the stability of the well wall, prevent the loss of drilling fluid, and ensure safe and efficient drilling in deep formations.

[0033] 3. The wall-fixing agent of the present invention is simple to prepare, green and environmentally friendly, and low in price, and is suitable for drilling projects in deep wells, ultra-deep wells, and environmentally sensitive areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the infrared spectrum of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide prepared in Preparation Example 1.

[0035] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide prepared in Preparation Example 1.

[0036] Figure 3 This is the infrared spectrum of the temperature-resistant and salt-resistant wall-solidifying agent for 10,000-meter deep well water-based drilling fluid prepared in Example 1. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below by way of examples, but the present invention is not limited thereby. In the following preparation examples, examples and comparative examples, unless otherwise specified, all materials used are commercially available and all methods used are conventional methods in the art.

[0038] Preparation Example 1

[0039] Preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide:

[0040] Add 12.5 g of 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride and 75.0 g of methanol to a clean beaker, stir until the solid dissolves to obtain solution 1, and cool to 0°C in an ice bath; dissolve 5.80 g of acryloyl chloride in 5.5 g of tetrahydrofuran and stir evenly to obtain solution 2; dissolve 15.8 g of triethylamine in 25.0 g of methanol and stir evenly to obtain solution 3; at 0°C, simultaneously add solution 2 and solution 3 dropwise to solution 1 for 20 min; after the addition is complete, continue the reaction at 25°C, stirring at 400 rpm, and under a nitrogen atmosphere for 6 h. After the reaction, the resulting reaction solution was rotary evaporated to remove the solvent at 70° C., 100 mL of ethyl acetate was added to the resulting crude product, and the product was washed twice with a mixed solution containing HCl and NaCl (the mass ratio of HCl to NaCl in the mixed solution was 3:4, and the concentration of HCl in the mixed solution was 1 mol / L); the washed organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was rotary evaporated; the resulting product was then vacuum dried at 105° C. to constant weight, and the resulting white solid powder was N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide.

[0041] The infrared spectrum of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide obtained in this preparation example is shown in FIG. Figure 1 As shown by Figure 1 It can be seen that at 3449cm -1The characteristic peak at 3279cm comes from the stretching vibration of phenolic hydroxyl groups; -1 The characteristic peak at 1669 cm comes from the stretching vibration of the NH bond in the amide group; -1 The characteristic peak at 1620 cm comes from the stretching vibration of C=O in the amide group; -1 The characteristic peaks at 1595, 1512, and 1469 cm-1 are derived from the stretching vibration of the carbon-carbon double bond. -1 The characteristic peaks at 1277 and 1256 cm-1 come from the skeleton vibration of the benzene ring. -1 The characteristic peak at 1095 cm-1 is derived from the stretching vibration of CN in amide and the bending vibration of phenolic hydroxyl group. -1 The characteristic peak at 918 cm comes from the stretching vibration of the CO bond in the phenolic hydroxyl group; -1 The characteristic peak at 744 cm comes from the out-of-plane deformation vibration of the carbon-carbon double bond; -1 The characteristic peak at [Number missing] comes from the bending vibration of the C-H bond in the benzene ring. Infrared spectroscopy analysis revealed that the synthesized product contained characteristic functional groups such as hydroxyl, amide, carbonyl, and carbon-carbon double bonds, indicating the successful synthesis of N-(2-[3,4-dihydroxyphenyl]ethyl)acrylamide.

[0042] The H NMR spectrum of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide obtained in this preparation example is shown in FIG. Figure 2 As shown by Figure 2 The characteristic peak at 2.71 ppm is derived from the chemical shift of a hydrogen atom on the methylene group attached to the benzene ring; the characteristic peak at 3.73 ppm is derived from the chemical shift of a hydrogen atom on the methylene group in -NH-CH2-; the characteristic peaks at 5.78 ppm and 6.22 ppm are derived from the chemical shifts of hydrogen atoms on the carbon-carbon double bond; and the characteristic peaks at 6.82 ppm and 6.92 ppm are derived from the chemical shifts of hydrogen atoms on the benzene ring. Proton NMR and infrared spectroscopy analysis revealed that the synthesized product contained characteristic functional groups, including a carbon-carbon double bond, a hydroxyl group, an amide group, and a benzene ring, indicating the successful synthesis of N-(2-[3,4-dihydroxyphenyl]ethyl)acrylamide. (The characteristic peak of the phenolic hydroxyl group was absent in the proton NMR spectrum due to ion exchange with the solvent D2O.)

[0043] Preparation Example 2

[0044] Preparation of N-(2-phenylethyl)acrylamide:

[0045] 10.0 g of phenylethylamine was fully dissolved in 70.0 g of methanol to obtain solution 1, which was then cooled to 0°C in an ice bath; 6.8 g of acryloyl chloride was dissolved in 6.0 g of tetrahydrofuran and stirred to obtain solution 2; 17.2 g of triethylamine was dissolved in 30.0 g of methanol and stirred to obtain solution 3; at 0°C, solution 2 and solution 3 were simultaneously added dropwise to solution 1 for 20 minutes; after the addition was complete, the reaction mixture was reacted at 25°C, a stirring rate of 400 rpm, and a nitrogen atmosphere for 6 hours. After the reaction, the reaction solution was evaporated at 70°C to remove the solvent, and the crude product was transferred to 100 mL of ethyl acetate and washed twice with a mixed solution of HCl and NaCl (the mass ratio of HCl and NaCl in the mixed solution was 3:4, and the concentration of HCl in the mixed solution was 1 mol / L); the organic layer obtained by washing was dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated; the product was then vacuum dried at 105°C to constant weight to obtain a white solid powder, which is N-(phenylethyl)acrylamide.

[0046] Example 1

[0047] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0048] 5 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 10 g of N-hydroxymethyl acrylamide, 5 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 2 g of octadecyl vinyl ether, and 0.3 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product. The reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-fixing agent A1 for water-based drilling fluids in 10,000-meter deep wells.

[0049] The infrared spectrum of the heat-resistant and salt-resistant wall-fixing agent for water-based drilling fluid in a 10,000-meter deep well obtained in this embodiment is as follows: Figure 3 As shown by Figure 3 It can be seen that at 3450 cm -1 The characteristic peak at 3327cm comes from the stretching vibration of phenolic hydroxyl groups; -1 The characteristic peak at 2935 cm comes from the stretching vibration of the NH bond in the amide group; -1The characteristic peak at 2860 cm-1 comes from the asymmetric stretching vibration of -CH2 in the long alkyl chain; -1 The characteristic peak at 1670 cm comes from the symmetrical stretching vibration of -CH3; -1 The characteristic peaks at 1595, 1512, and 1469 cm-1 are from the stretching vibration of C=O (from amide and carboxyl groups); -1 The characteristic peaks at 1277 and 1256 cm-1 come from the skeleton vibration of the benzene ring. -1 The characteristic peak at 1035cm comes from the stretching vibration of CN in amide and the bending vibration of phenolic hydroxyl group; -1 The characteristic peak at 744 cm comes from the stretching vibration of the C–O bond in the hydroxyl group and the stretching vibration of the COC in the ether bond; -1 The characteristic peak at 647cm comes from the bending vibration of the CH bond in the benzene ring. -1 The characteristic peak at comes from the stretching vibration of Fe-O bond. The infrared spectrum results show that the wall solidifier contains characteristic peaks of four monomer raw materials, indicating that the wall solidifier is successfully polymerized.

[0050] Example 2

[0051] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0052] 10 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 10 g of N-hydroxymethyl acrylamide, 5 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 2 g of octadecyl vinyl ether, and 0.3 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product; the reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-solidifying agent A2 for water-based drilling fluid in 10,000-meter deep wells.

[0053] Example 3

[0054] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0055] 10 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 20 g of N-hydroxymethyl acrylamide, 5 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 2 g of octadecyl vinyl ether, and 0.3 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product; the reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-fixing agent A3 for water-based drilling fluids in 10,000-meter deep wells.

[0056] Example 4

[0057] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0058] 10 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 20 g of N-hydroxymethyl acrylamide, 10 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 2 g of octadecyl vinyl ether, and 0.3 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product. The reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-fixing agent A4 for water-based drilling fluids in 10,000-meter deep wells.

[0059] Example 5

[0060] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0061] 10 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 20 g of N-hydroxymethyl acrylamide, 10 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 5 g of octadecyl vinyl ether, and 0.3 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product; the reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-fixing agent A5 for water-based drilling fluid in 10,000-meter deep wells.

[0062] Example 6

[0063] A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for a 10,000-meter deep well water-based drilling fluid comprises the following steps:

[0064] 10 g of acrylic acid and 60 g of deionized water were added to a clean beaker, and sodium hydroxide pellets were added to adjust the pH of the system to 7.0. Then, 20 g of N-hydroxymethyl acrylamide, 10 g of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, 0.02 g of sodium lauryl sulfate, 5 g of octadecyl vinyl ether, and 0.6 g of ferric chloride hexahydrate were added to the system in sequence. The mixture was sheared at a stirring rate of 2000 rpm for 20 min to uniformly disperse the monomers to obtain a monomer solution. The monomer solution was transferred to a three-necked flask, and 0.20 g of initiator was added (the initiator was a mixture of ammonium persulfate, sodium bisulfite, and 2,2'-azobisisobutylamidine dihydrochloride in a mass ratio of 2:1:2). The reaction was continued at 75°C, a stirring rate of 200 rpm, and a nitrogen atmosphere for 6 hours to obtain a light yellow viscous reaction product; the reaction product was washed twice with methanol, dried to constant weight at 75°C, and crushed to obtain a temperature-resistant and salt-resistant wall-fixing agent A6 for water-based drilling fluids in 10,000-meter deep wells.

[0065] Comparative Example 1

[0066] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that acrylic acid is replaced with acrylamide of equal mass to obtain a water-based wall-fixing agent D1 for drilling fluid.

[0067] Comparative Example 2

[0068] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that N-hydroxymethyl acrylamide is replaced with N,N-dimethyl acrylamide of equal mass to obtain a water-based wall-fixing agent D2 for drilling fluid.

[0069] Comparative Example 3

[0070] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that octadecyl vinyl ether is replaced with ethyl vinyl ether of equal mass to obtain a water-based wall-fixing agent D3 for drilling fluid.

[0071] Comparative Example 4

[0072] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is replaced with N-(2-phenylethyl)acrylamide of equal mass to obtain a water-based wall-fixing agent D4 for drilling fluid.

[0073] Comparative Example 5

[0074] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that acrylic acid is not added to prepare the wall-fixing agent, thereby obtaining a water-based wall-fixing agent D5 for drilling fluid.

[0075] Comparative Example 6

[0076] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that N-hydroxymethyl acrylamide is not added to obtain a water-based wall-fixing agent D6 for drilling fluid.

[0077] Comparative Example 7

[0078] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is not added to obtain a water-based wall-fixing agent D7 for drilling fluid.

[0079] Comparative Example 8

[0080] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that octadecyl vinyl ether is not added to obtain a water-based wall-fixing agent D8 for drilling fluid.

[0081] Comparative Example 9

[0082] A method for preparing a water-based wall-fixing agent for drilling fluid is as described in Example 1, except that no complexing agent is added to obtain a water-based wall-fixing agent D9 for drilling fluid.

[0083] Application Test Example 1: Evaluation of Drilling Fluid Rheological Loss Performance

[0084] Preparation of bentonite-based slurry: At room temperature, 400 g of bentonite and 14.0 g of Na2CO3 were added to 10000 mL of deionized water, stirred at 3000 rpm for 2 h, and then statically cured for 24 h to obtain the bentonite-based slurry.

[0085] Preparation of saturated salt bentonite slurry: At room temperature, 144 g of NaCl was added to 400 mL of bentonite slurry and stirred at 3000 rpm for 20 min to obtain saturated salt bentonite slurry.

[0086] 8 g of the wall-fixing agents A1-A6 in the examples and 8 g of the wall-fixing agents D1-D9 in the comparative examples were added to 400 g of saturated salt bentonite-based slurry, and stirred at 6000 rpm for 20 min to obtain drilling fluids F1-F6 and DF1-DF9.

[0087] The drilling fluid was placed in a stainless steel aging tank and tumbled at a constant temperature of 200°C for 16 hours. After aging, the fluid was cooled to room temperature and stirred at 10,000 rpm for 20 minutes. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API fluid loss (FL) of the drilling fluid before and after high-temperature aging were measured according to the petroleum and natural gas industry standard GB / T 29170-2012, "Petroleum and Natural Gas Industry - Laboratory Testing of Drilling Fluids." API , the results are shown in Table 1-2.

[0088] Table 1 Performance test of drilling fluid with added wall solidifying agent

[0089]

[0090] Table 2 Performance test of drilling fluid with comparative example wall solidifying agent

[0091]

[0092] From the experimental results, it can be seen that when the wall-fixing agent of the present invention is added in an amount of 2% in the saturated salt-based slurry, the apparent viscosity, plastic viscosity and shear force of the saturated salt-based slurry before and after aging at 200°C are all improved to a certain extent, and the filtration loss is greatly reduced. This shows that the strong adsorption and high cohesion cementing wall-fixing agent of the present invention has good viscosity-increasing and shear-enhancing effects in saturated salt-based slurry, and can effectively reduce the filtration loss. The wall-fixing agent of the present invention contains highly adsorbable hydroxyl, amino and carboxyl groups, which enable the wall-fixing agent to be tightly adsorbed on the surface of the clay, and the hydrophobic groups form an associative structure to jointly construct the internal grid structure of the drilling fluid with the clay, thereby maintaining the stability of the internal grid structure under the high temperature and high salt conditions of the drilling fluid. At the same time, the strong adsorption and high cohesion cementing wall-fixing agent can participate in the formation of the mud cake and cement the water-loss pores and cracks inside the mud cake, thereby effectively reducing filtration loss. From the comparative examples, it can be seen that the wall-fixing agents lacking key monomers such as acrylic acid, N-hydroxymethyl acrylamide, N-(2-[3,4-dihydroxyphenyl]ethyl) acrylamide, octadecyl vinyl ether and complexing agents, or the wall-fixing agents prepared by reducing the amount of key monomers, all failed to achieve effective viscosity increase, shear strength improvement and filtration loss reduction effects.

[0093] Application Test Example 2: Evaluation of Drilling Fluid Plugging Performance

[0094] Sand bed plugging experiment: Drilling fluids F1-F6 of the examples and drilling fluids DF1-DF9 of comparative examples 1-9 were prepared according to the method in application test example 1, aged at 200°C for 16 hours, cooled to room temperature and taken out. 300 cm3 of the liquid was placed in the clean transparent glass filling tube of the FA.BX medium pressure sand bed plugging instrument. 3 80 mesh quartz sand, flatten and compact, then add 150cm 3 The depth of penetration of the aged drilling fluid into the sand bed was tested at room temperature and 0.69±0.03MPa for 30min.

[0095] Microporous filter membrane blocking experiment: Wall-fixing agents A1-A6 from the examples and wall-fixing agents D1-D9 from comparative examples 1-9 were added to 400 mL of deionized water. Then, 144 g of NaCl was added to prepare saturated salt solutions containing the wall-fixing agents, FL1-FL6 and DFL1-DFL9. FL1-FL6 and DFL1-DFL9 were placed in a stainless steel aging tank and aged at 200°C for 16 hours. After cooling to room temperature, the samples were removed and the API filtration loss of FL1-FL6 and DFL1-DFL9 was measured at 25°C and 100 psi. The filter paper used was a polytetrafluoroethylene microporous filter membrane with a pore size of 1 μm. The results are shown in Table 3.

[0096] Table 3 Drilling fluid plugging performance test

[0097]

[0098] The experimental results show that when the wall-fixing agent of the present invention is not added, the drilling fluid filtrate completely penetrates the sand bed. After adding the wall-fixing agent of the present invention, the penetration depth of the sand bed of the drilling fluid is reduced. The microporous filter membrane blocking experiment also shows the same result. This shows that the wall-fixing agent of the present invention has an excellent blocking effect and can effectively prevent the loss of drilling fluid to the high permeability layer. If the wall-fixing agent of the present invention lacks key monomers or key materials, the blocking effect will be deteriorated.

[0099] Application Test Example 3: Drilling Fluid Wall Reinforcement Performance Test

[0100] Compressive strength testing: Shale columns (25 cm x 30 cm) were immersed in drilling fluids F1-F6 and DF1-DF9 (prepared according to the method in Application Test Example 1) and aged at 200°C for 16 hours. After aging, the columns were cooled to room temperature and vacuum-dried at 90°C for 12 hours. Their compressive strength was then measured. The results are shown in Table 4.

[0101] Point load strength test: Shale slices (25 mm x 3 mm) were immersed in drilling fluids F1-F6 from the examples and DF1-DF9 from the comparative examples (prepared according to the method in Application Test Example 1) and aged at 200°C for 16 hours. After aging, the slices were cooled to room temperature and vacuum-dried at 90°C for 12 hours. The point load strength of the shale slices was measured using the nanoindentation module of a multifunctional surface tester. A triangular pyramid diamond indenter was used at 60°C, with a load increment rate of 100 N / min and a maximum load of 200 N. The experimental results are shown in Table 4.

[0102] Overlap shear strength test: The drilling fluids F1-F6 of the embodiments and the drilling fluids DF1-DF9 of the comparative examples (prepared according to the method in Application Test Example 1) were evenly spread on the single overlapping surface of the artificial overlapped specimens (shale slices) in accordance with the "Determination of tensile shear strength of adhesives" (GB7124-2008) and the "Determination of chemical resistance of adhesives" (GB / T13353-92). The overlapped specimens were pressed at 10±0.5 MPa for 2 h, and then vacuum dried at 90°C for 12 h. A tensile force was applied parallel to the overlapped surface and in the direction of the principal axis of the specimen to test the overlap shear strength of the specimens. The experimental results are shown in Table 4.

[0103] Table 4. Drilling fluid wall solidification performance test

[0104]

[0105] As can be known from the experimental results, the wall-fixing agent of the present invention is all conducive to improving the intensity of rock core and has excellent wall-fixing performance.The wall-fixing agent of the present invention contains strong adsorption groups such as hydroxyl, amino, and carboxyl, and has stronger adhesion to rock surface.After the wall-fixing agent is adsorbed on the rock surface and inside the pores, on the one hand, the wall-fixing agent can block the rock pores, consolidate the rock core by strong cohesion, and maintain rock strength. On the other hand, the hydrophobic group of the wall-fixing agent can form a hydrophobic layer on the rock surface, produce an isolation effect to water molecules, and maintain the bonding force between the wall-fixing agent and the rock. During drilling, the wall-fixing agent of the present invention can adsorb and block the micropores inside the rock, and then cement the rock, maintain the compressive strength of the rock, prevent the drilling fluid from invading the stratum interior, and effectively prevent the well wall from collapsing.

[0106] In summary, the strong adsorption and high cohesion cementitious wall fixing agent of the present invention is temperature-resistant up to 200°C and salt-resistant up to saturation. It has good viscosity-increasing, shear-enhancing and filtration-loss reduction effects under high-temperature and high-salt conditions. It can effectively adsorb, seal and cement the micropores and microcracks inside the rock, maintain the stability of the well wall, prevent drilling fluid leakage, and provide strong technical support for safe and efficient deep well drilling.

[0107] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0108] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0109] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well, characterized in that: The steps are as follows: (1) Acrylic acid is added to deionized water, and the pH of the system is adjusted to 7.

0. Then, N-hydroxymethyl acrylamide, N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, an emulsifier, octadecyl vinyl ether, and a complexing agent are sequentially added to the system, and shearing is performed to uniformly disperse the monomers to obtain a monomer solution; the mass ratio of the N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, N-hydroxymethyl acrylamide, acrylic acid, and octadecyl vinyl ether is 5-10:10-20:5-10:1-5; the emulsifier is any one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, Tween 80, and Span 80; the mass ratio of the emulsifier to octadecyl vinyl ether is 0.01-0.03:1-5; the complexing agent is ferric chloride hexahydrate, zinc chloride, magnesium chloride, or calcium chloride; the mass ratio of the complexing agent to N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is 0.3-0.8:5-10; (2) adding an initiator to the monomer solution to carry out a reaction; after the reaction is completed, washing, drying and crushing are performed to obtain a temperature-resistant and salt-resistant wall-fixing agent for a 10,000-meter deep well water-based drilling fluid; the initiator is a composition of ammonium persulfate, sodium bisulfite and 2,2'-azobisisobutylamidine dihydrochloride, wherein the mass ratio of ammonium persulfate, sodium bisulfite and 2,2'-azobisisobutylamidine dihydrochloride is 5-8:2-4:8-12, and the mass ratio of the initiator to N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide is 0.15-0.25:5-10.

2. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid of 10,000-meter deep well according to claim 1, characterized in that: The mass ratio of deionized water to acrylic acid in step (1) is 60-120:5-10; sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 7.

3. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid of 10,000-meter deep well according to claim 1, characterized in that: The shearing rate in step (1) is 1500-2500 rpm, and the shearing time is 10-30 min.

4. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid of 10,000-meter deep well according to claim 1, characterized in that: The N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide described in step (1) is prepared according to the following method: 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is added to methanol and stirred until the solid is dissolved to obtain solution 1; acryloyl chloride is added to tetrahydrofuran and stirred to dissolve to obtain solution 2; triethylamine is added to methanol and stirred evenly to obtain solution 3; solution 2 and solution 3 are dropwise added to solution 1, and after the dropwise addition is complete, the mixture is reacted to obtain N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide.

5. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid of 10,000-meter deep well according to claim 4, characterized in that: In the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, the mass ratio of methanol to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride in solution 1 is 70-130:8-15; the mass ratio of acryloyl chloride to tetrahydrofuran in solution 2 is 4.5-6.5:4.2-5.5; the mass ratio of triethylamine to methanol in solution 3 is 13-18:20-35; the mass ratio of acryloyl chloride to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is 4-6:10-15; and the mass ratio of triethylamine to 2-(3,4-dihydroxyphenyl)ethylamine hydrochloride is 1-2:

1.

6. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well according to claim 4, characterized in that: In the preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide, solution 2 and solution 3 are simultaneously added dropwise to solution 1 at 0-5°C for 15-20 minutes; the reaction temperature is 20-30°C, and the reaction time is 5-7 hours; the reaction is carried out under a nitrogen atmosphere.

7. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well according to claim 4, characterized in that: The preparation of N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide further includes a post-processing step after the reaction is completed, specifically as follows: removing the solvent from the obtained reaction solution, adding ethyl acetate, washing the organic phase with a mixed solution containing HCl and NaCl, drying over anhydrous sodium sulfate, filtering, and removing the solvent; and vacuum drying the obtained product at 100-110° C. to constant weight to obtain N-[2-(3,4-dihydroxyphenyl)ethyl]-2-acrylamide; the mass ratio of HCl to NaCl in the mixed solution is 7-9:10-12, and the concentration of HCl in the mixed solution is 0.5-1.5 mol / L.

8. The method for preparing the temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid of 10,000-meter deep wells according to claim 1, characterized in that: The reaction temperature in step (2) is 70-80°C, and the reaction time is 5-7h; the washing is performed 2-3 times with methanol, and the drying is performed at 70-80°C to constant weight.

9. A temperature-resistant and salt-resistant wall-solidifying agent for water-based drilling fluid in a 10,000-meter deep well, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. The use of the heat-resistant and salt-resistant wall-fixing agent for water-based drilling fluid for 10,000-meter deep wells according to claim 9 in water-based drilling fluid for stabilizing the well wall and preventing leakage, characterized in that: The mass concentration of the heat-resistant and salt-resistant wall-solidifying agent for 10,000-meter deep well water-based drilling fluid in the water-based drilling fluid is 1-3 wt %.

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