Drilling fluid anti-sloughing lubricant and preparation method thereof

Abstract

This invention belongs to the field of oil and gas drilling engineering technology, specifically relating to a drilling fluid anti-collapse lubricant and its preparation method. The method includes: firstly, heating deionized water, adding polyanionic cellulose, modified starch, and sulfonated asphalt, and stirring to form a gel; then sequentially adding octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets and ethylmethylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composites, and shearing and dispersing; next, adding lubricant and surfactant for emulsification; finally, adding defoamer and preservative, and cooling to obtain the final product. The anti-collapse lubricant obtained by this invention exhibits excellent temperature and salt resistance, effectively inhibiting the hydration and expansion of shale and reducing drill string friction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas drilling engineering, and particularly relates to a drilling fluid anti-sloughing lubricant and a preparation method thereof. BACKGROUND

[0002] In oil and gas drilling operations, wellbore instability and increased drilling tool friction are two core problems that have long plagued drilling engineering. Wellbore instability is mainly manifested in the hydration expansion and dispersion peeling of shale formations, and the root cause is the invasion of drilling fluid filtrate into formation micro-pores and micro-cracks, which triggers clay mineral hydration expansion, reduces rock mechanical strength, and ultimately leads to downhole complex accidents such as collapse and sticking. At the same time, the frictional resistance between the drill string and the wellbore directly affects the mechanical drilling speed and the wellbore extension capacity. In particular, in extended reach wells, horizontal wells and deep wells, excessive friction can cause the drill string to be unable to be lowered or stuck, which seriously restricts the efficiency of oil and gas resource exploration and development. Therefore, developing a high-performance drilling fluid additive with both anti-sloughing and lubricating functions has important engineering application value.

[0003] Traditional anti-sloughing agents mainly include asphalt, silicate and polymer compounds. Although silicate anti-sloughing agents can plug formation pores through sedimentation, their high alkalinity and adverse effects on drilling fluid rheology limit their widespread application. Although asphalt anti-sloughing agents can effectively plug micro-cracks, they have the problems of fluorescence interference with geological logging and environmental pollution. Traditional drilling fluid lubricants are mainly mineral oil, vegetable oil and surfactants. Although these lubricants can reduce friction, they often lack anti-sloughing function and have limited temperature resistance, and are easily decomposed and inactivated under high temperature and deep well conditions. With the increasing exploration and development of deep, ultra-deep and unconventional oil and gas resources, drilling fluids are facing higher temperature and pressure and more complex formation conditions, and single-function additives have been difficult to meet engineering needs. Therefore, it is an urgent need in the industry to develop multifunctional additives with both anti-sloughing and lubricating properties.

[0004] In recent years, the application of inorganic nanomaterials in drilling fluids has attracted widespread attention. Layered zirconium phosphate, a two-dimensional inorganic nanomaterial, can form a physical isolation layer at the friction interface due to its layered structure, significantly reducing the friction coefficient. Its tribological properties can be further regulated through surface and interlayer modification. Polyoxometalates are a class of transition metal-oxygen anion clusters with cage-like structures. Their unique Keggin structure endows the compounds with excellent thermal and chemical stability, showing good potential for tribological modification. Furthermore, nanomaterials such as nano-titanium dioxide and graphene oxide, after surface modification, can simultaneously perform multiple functions in drilling fluids, including plugging, reducing filtration loss, and lubrication. However, there are currently no reports of using these materials in drilling fluid anti-collapse and lubrication applications through multi-step inorganic modification and composite processes. Therefore, developing a novel drilling fluid additive that combines layered zirconium phosphate, titanium dioxide, polyoxometalates, and graphene oxide into a composite material with excellent anti-collapse and lubrication properties, as well as good temperature and salt resistance, is of great practical significance and has broad application prospects for solving the drilling fluid technical challenges of deep wells, ultra-deep wells, and wells with complex structures. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a drilling fluid anti-collapse lubricant and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a drilling fluid anti-collapse lubricant, comprising the steps of:

[0007] S1. By weight, add 70-90 parts of deionized water to a reactor and heat to 50-60℃; add 1-3 parts of polyanionic cellulose, 2-5 parts of modified starch and 3-8 parts of sulfonated asphalt, and stir to obtain a gel; while stirring, add 0.5-2 parts of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets to the gel, and after ultrasonic stirring, add 0.3-1.5 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, and shear disperse to obtain a mixture.

[0008] S2. Add 5-15 parts of lubricant and 1-3 parts of surfactant to the mixture and stir at 55-65℃; finally, add 0.1-0.5 parts of defoamer and 0.1-0.3 parts of preservative in sequence and continue stirring; let it cool naturally to room temperature.

[0009] In this invention, the construction of the drilling fluid anti-collapse lubricant deeply integrates the steric stabilization theory of polymers with the multi-level lubrication mechanism of nanofluids. In a basic aqueous environment, the polymer and modified starch derivatives added first undergo strong hydrogen-bonding hydration with water molecules under specific temperature and continuous shear stress. The long-chain polymers fully expand and entangle in the solution, which not only significantly increases the apparent viscosity of the liquid phase and constructs a gel matrix with a dense three-dimensional network structure, but also forms an extremely thick hydration protective film on the surface of solid particles through physical adsorption, providing an irreplaceable steric hindrance effect. Subsequently, the two composite nanomaterials with opposite surface charges are introduced stepwise. High-frequency ultrasound and mechanical shear flow fields instantly tear apart the fragile soft aggregates between nanoparticles. The strong steric hindrance effect of the polymer gel network cleverly isolates the direct collision between positive and negative charged nanoparticles, fundamentally avoiding destructive electrostatic flocculation and sedimentation, and forming a uniform and highly stable interpenetrating network suspension in the system. Based on this, a large amount of basic lubricant and surfactant undergo a dramatic emulsification phase transition. The surfactant oriented at the oil-water interface greatly reduces interfacial tension, tearing the pure oil phase into stable emulsified oil droplets at the micro-nano scale. The resulting anti-collapse lubrication system exhibits a remarkable multi-effect synergistic mechanism under extreme downhole conditions: the rigid two-dimensional zirconium phosphate composite plate and the flexible graphene oxide act like bricks and mud, forming a dense and seamless physical sealing layer in the micro-fractures and pores of the wellbore rock, completely blocking the hydration and infiltration path of free water into the formation, and inhibiting mudstone expansion and collapse at the microscopic level; at the same time, the hybrid nanomaterials containing ionic liquid lubricating film and the emulsified oil droplets exert interlayer polarization slip and hydrodynamic pressure bearing effects respectively at the high-pressure extreme pressure friction interface between the drill string and the rock, perfectly transforming the highly destructive solid dry friction into extremely low-resistance fluid elasticity and nano-bearing friction, achieving ultimate friction reduction and anti-sticking performance.

[0010] According to a preferred embodiment of the present invention, in step S1, the modified starch is carboxymethyl starch.

[0011] According to a preferred embodiment of the present invention, in step S2, the lubricant is white oil; the surfactant is Tween-80 or Tween-60; the defoamer is an organosilicone defoamer; and the preservative is sodium benzoate.

[0012] According to a preferred embodiment of the present invention, the method for preparing the octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets includes:

[0013] A1. By weight, add 100-150 parts of phosphoric acid aqueous solution to a reaction vessel to obtain a phosphoric acid solution; dissolve 5-10 parts of zirconium oxychloride octahydrate in 20-30 parts of deionized water, add to the phosphoric acid solution, and stir continuously to obtain mixture A; transfer mixture A to a reaction vessel, seal it, and place it in a forced-air drying oven at 178-182℃; after the reaction is completed, allow it to cool naturally to room temperature, centrifuge to obtain precipitate A; wash precipitate A with deionized water and anhydrous ethanol, dry it in a vacuum drying oven at 78-82℃, grind it, and obtain α- Zirconium phosphate powder; 2-5 parts of α-zirconium phosphate powder are dispersed in 80-120 parts of anhydrous ethanol and ultrasonically dispersed to obtain a suspension; 0.5-1 parts of glacial acetic acid and 4-8 parts of tetraisopropyl titanate are premixed in an ice-water bath to obtain mixture B; mixture B is added dropwise to the suspension and stirred continuously, then 2-5 parts of deionized water are added, and the mixture is heated and stirred at 58-62℃. After the reaction is completed, the mixture is centrifuged to obtain precipitate B; precipitate B is washed with anhydrous ethanol and vacuum dried at 78-82℃ to obtain α-zirconium phosphate-titanium dioxide composite nanosheets.

[0014] A2. Disperse 1.5-4 parts of α-zirconium phosphate-titanium dioxide composite nanosheets in 80-100 parts of deionized water, ultrasonically disperse, add 0.8-2 parts of octadecyltrimethylammonium bromide, stir and react in a water bath at 58-62℃, after the reaction is complete, centrifuge to obtain precipitate C; wash precipitate C with deionized water, dry in a vacuum drying oven at 58-62℃, and grind.

[0015] In this invention, the preparation of the octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets begins with the self-assembly of inorganic two-dimensional crystalline layers. Zirconium oxychloride undergoes hydrolysis and complexation reactions in a strongly acidic phosphoric acid aqueous solution. The extremely high concentration of phosphoric acid not only provides sufficient phosphate ions as a reaction substrate but also acts as a core mineralizing agent, guiding the crystals to grow oriented along specific thermodynamically dominant crystal planes. Under specific high-temperature and high-pressure closed thermodynamic environments, zirconium oxide ions slow down the disordered hydrolysis rate and undergo ordered alternating coordination with phosphate ions, forming a layered zirconium phosphate substrate with high crystallinity and extremely high cation exchange capacity through a condensation process. Subsequently, titanium dioxide is uniformly coated in situ using a controlled multiphase nucleation mechanism of the sol-gel method. In this stage, titanate precursors readily undergo homogeneous rapid hydrolysis in polar solvents. By introducing glacial acetic acid as a nucleophilic substitution ligand, a stable coordination complex is formed with titanium atoms, effectively suppressing its hydrolysis rate kinetically. Because the surface of crystalline layered zirconium phosphate is rich in active hydroxyl groups, these hydroxyl groups act as inducing sites for multiphase nucleation, promoting the slow hydrolysis and condensation of the titanium precursor on its surface, thereby firmly growing titanium dioxide nanoparticles. Finally, long-chain organic quaternary ammonium salt intercalation modification is performed. After ultrasonic deagglomeration, octadecyltrimethylammonium bromide ionizes in a heated water bath to release a large, positively charged cation. Driven by concentration gradient and strong electrostatic attraction, this cation gradually replaces the protons between the layers of layered zirconium phosphate. With the deepening of ion exchange, the extremely long carbon chains generate a huge steric hindrance effect, forcibly opening the inorganic layers and significantly increasing the interlayer spacing. This modification completely reverses the hydrophilic properties of the inorganic layer surface, endowing it with extremely strong oleophilicity and low surface energy. This not only greatly eliminates the tendency of nanoparticles to aggregate but also enables them to achieve highly stable dispersion in complex oil phases or emulsion drilling fluid systems.

[0016] According to a preferred embodiment of the present invention, in step A1, the reaction time at 178-182°C is 48-50 h.

[0017] According to a preferred embodiment of the present invention, in step A2, the stirring reaction in a water bath at 58-62°C is carried out for 24-30 hours.

[0018] According to a preferred embodiment of the present invention, the preparation method of the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite includes:

[0019] B1. By weight, dissolve 15-20 parts of sodium tungstate dihydrate and 1.5-2.5 parts of sodium silicate nonahydrate in 50-70 parts of deionized water and stir to obtain a mixed solution. While stirring, add hydrochloric acid solution dropwise to the mixed solution to adjust the pH to 1.0-2.0. Reflux the reaction at 88-92℃. After the reaction is complete, cool naturally and filter to obtain a filtrate. Allow the filtrate to crystallize at room temperature to obtain crystals. Wash the crystals with ice water and vacuum dry at room temperature to obtain silicotungstic acid. Adjust the pH of the graphene oxide dispersion to 2.0-3.0 with dilute hydrochloric acid to obtain an acidified graphene oxide dispersion. Add 50-80 parts of the acidified graphene oxide dispersion to 0.5-1.2 parts of silicotungstic acid, disperse ultrasonically, stir, and centrifuge to obtain precipitate D. Wash precipitate D with deionized water and vacuum dry at 35-40℃ to obtain the complex.

[0020] B2. Disperse 1.0-2.5 parts of the complex in 50-70 parts of anhydrous ethanol. After ultrasonic dispersion, add 0.5-1.5 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate. Stir the reaction in a water bath at 48-52℃. After the reaction is complete, centrifuge to obtain precipitate E. Wash precipitate E with anhydrous ethanol, dry it in a vacuum drying oven at 30-35℃, and grind it.

[0021] In this invention, the preparation reaction of the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite begins with the condensation polymerization of classic Kägen-type polyoxometalates. After the tungstate and silicate are completely co-soluble in an aqueous solution, a strong acid is slowly added under thermodynamic driving forces of vigorous stirring and reflux, causing the pH of the solution system to drop rapidly to the strong acid limit. At this point, the tungstate anion rapidly undergoes protonation dehydration condensation. Under the template induction of the central silicate tetrahedron, the peripheral tungstate octahedra self-assemble through the sharing of corners and edges, ultimately forming a stable anion cluster of silicotungstic heteropolyacids with a Kägen structure possessing high spatial symmetry and strong electron-withdrawing ability. The purified heteropolyacid then enters the carbon-based support loading stage. Graphene oxide is obtained by deep exfoliation of natural graphite with a strong oxidant. Its two-dimensional, huge conjugated carbon skeleton is densely covered with oxygen-containing functional groups such as carboxyl and hydroxyl groups. In a precisely regulated acidic microenvironment, some oxygen-containing groups on the surface of graphene oxide undergo moderate protonation, reducing electrostatic repulsion to a minimum threshold. Highly dispersed polyoxometalate anion clusters are firmly anchored to the two-dimensional layer of graphene oxide through hydrogen bonding networks, van der Waals forces, and localized polar attraction, forming a hybrid primary structure with ultra-high specific surface area and densely packed active catalytic sites. Finally, functionalized imidazole-based room-temperature ionic liquids are introduced for deep interfacial modification. The imidazole ring cations in the ionic liquid not only neutralize the localized negative charges on the composite material surface through strong electrostatic attraction but also engage in strong delocalized electron cloud conjugation interactions with the large conjugated carbon skeleton of graphene oxide. This synergistic anchoring of multiple non-covalent bonds allows the ionic liquid to tightly and uniformly coat the surface of the hybrid support, forming a highly elastic and thermally stable ionic lubricating protective film.

[0022] According to a preferred embodiment of the present invention, the preparation steps of the graphene oxide dispersion include: by weight, placing 120-150 parts of concentrated sulfuric acid in a reaction vessel in an ice-water bath, stirring, then sequentially adding 5-8 parts of natural flake graphite and 2.5-4 parts of sodium nitrate, and adding 15-20 parts of potassium permanganate, reacting at a temperature below 10°C; raising the temperature to 34-36°C and continuing to stir the reaction, then adding 200-250 parts of deionized water, raising the temperature to 88-92°C, and continuing to stir; adding 10-15 parts of hydrogen peroxide solution; centrifuging to obtain a solid; washing the solid with hydrochloric acid solution, and then washing it with deionized water to obtain a washed solid; adding 50-200 parts of deionized water to the washed solid and ultrasonically exfoliating it.

[0023] According to a preferred embodiment of the present invention, in steps B1-B2, the reflux reaction at 88-92°C is carried out for 6-8 hours; the stirring reaction in a water bath at 48-52°C is carried out for 24-30 hours.

[0024] In a second aspect, the present invention provides a drilling fluid anti-collapse lubricant prepared according to the aforementioned method for preparing drilling fluid anti-collapse lubricant.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) This invention achieves an organic unity of anti-collapse performance and lubrication performance through the synergistic compounding of two novel inorganic modified compounds. Among them, the octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheet has a unique two-dimensional layered structure. The insertion of long-chain quaternary ammonium salt significantly increases the interlayer spacing, making it easy to peel off and disperse in water-based drilling fluids. This nanosheet can form a physical isolation layer at the friction interface between the drill string and the well wall, effectively reducing the direct contact between the metal and the rock, thereby significantly reducing frictional resistance. At the same time, the in-situ coating of titanium dioxide nanoparticles endows the composite nanosheet with excellent thermal stability and temperature resistance, maintaining structural integrity and lubrication function even under high temperature conditions. On the other hand, in the ethylmethylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, the Keggin cage structure of silicotungstic acid provides an extremely high thermal decomposition temperature. Its composite with graphene oxide is achieved through electrostatic attraction and hydrogen bonding. The large specific surface area and two-dimensional layered structure of graphene oxide further enhance the adsorption and film-forming ability of the composite on the surface of the drill string and the well wall. The introduction of ionic liquids not only improved the dispersion stability of the composite in water-based drilling fluids, but also formed a chemisorption film with extreme pressure and anti-wear functions at the friction interface. The two modified compounds, one positively charged and the other negatively charged, formed a uniform colloidal dispersion system in the drilling fluid, avoiding agglomeration and sedimentation, and fully utilizing their respective anti-collapse and lubrication functions.

[0027] (2) The anti-collapse lubricant of this invention exhibits excellent stability under high temperature and high salinity conditions. This lubricant can withstand high-temperature environments and maintains stable rheological properties and filtration control capabilities even after high-temperature aging. It also possesses good salt resistance and can be applied to drilling operations in high-salinity formations. This is attributed to the inherent thermal stability of the inorganic framework in the two inorganic modified compounds: the layered phosphate structure of α-zirconium phosphate, the ceramic properties of titanium dioxide, the Keggin structure of silicotungstic acid, and the carbon framework of graphene oxide, all of which have high thermal decomposition temperatures. Simultaneously, the compounding of polyanionic cellulose, carboxymethyl starch, and sulfonated asphalt further enhances the thermal stability and filtration reduction performance of the adhesive. Regarding anti-collapse performance, this lubricant can effectively seal the micropores and microcracks in shale formations, prevent drilling fluid filtrate from invading the formation, and inhibit the hydration swelling and dispersion of clay minerals. Laboratory evaluations show that after adding the lubricant of this invention, the linear expansion rate of bentonite cores is significantly reduced, the core recovery rate is greatly improved, and the anti-collapse effect is significantly better than that of traditional anti-collapse agents.

[0028] (3) The preparation process of the lubricant of this invention is simple, the raw materials are readily available, and the cost is controllable. The synthesis of the two inorganic modified compounds both adopt multi-step reactions, and the raw materials for each step are commercially available chemicals, requiring no special or expensive reagents, making them suitable for industrial production. The preparation process of the drilling fluid anti-collapse lubricant only requires conventional stirring, heating, ultrasonic dispersion, and emulsification operations, without involving complex equipment or harsh reaction conditions. This lubricant has good compatibility with water-based drilling fluids and can be directly added to existing drilling fluid systems in any proportion without significant adjustments to the drilling fluid formulation. Field application tests show that after using the lubricant of this invention in horizontal wells and extended reach wells, the mechanical drilling rate is significantly improved, the tripping friction is significantly reduced, the wellbore enlargement rate is effectively reduced, the drill bit life is extended, and the incidence of complex downhole accidents is significantly reduced, demonstrating significant economic benefits and broad prospects for promotion and application. Detailed Implementation

[0029] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing a drilling fluid anti-collapse lubricant, the steps of which include:

[0032] S1: Add 80g of deionized water to a reactor and heat to 55℃; add 2g of polyanionic cellulose, 3.5g of carboxymethyl starch and 5.5g of sulfonated asphalt, and stir for 40min to obtain a gel. While stirring, add 1.25g of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets to the gel, and sonicate for 15min. Then add 0.9g of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, and shear disperse for 18min to obtain a mixture.

[0033] S2: Add 10g of white oil and 2g of Tween-80 to the mixture and stir at 60℃ for 50min; finally, add 0.3g of organosilicon defoamer and 0.2g of sodium benzoate in sequence and continue stirring for 18min; let it cool naturally to room temperature to obtain the drilling fluid anti-collapse lubricant.

[0034] Preparation of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets:

[0035] A1: 125g of 11mol / L phosphoric acid aqueous solution was added to a reaction vessel to obtain a phosphoric acid solution. 7.5g of zirconium oxychloride octahydrate was dissolved in 25g of deionized water to form a clear solution. Under stirring, the clear solution was slowly added dropwise to the phosphoric acid solution at a rate of 8 drops / min for 30 minutes to obtain mixture A. Mixture A was transferred to a polytetrafluoroethylene-lined high-pressure reaction vessel, sealed, and placed in a forced-air drying oven for 49 hours at 180℃. After the reaction, the mixture was allowed to cool naturally to room temperature and centrifuged (8000rpm, 10min) to obtain precipitate A. Precipitate A was washed three times each by alternating centrifugation with deionized water and anhydrous ethanol, dried in a vacuum drying oven at 80℃ for 24 hours, and ground to obtain α-zirconium phosphate powder. 3.5g of α-zirconium phosphate powder was dispersed in 100g of anhydrous ethanol and ultrasonically dispersed for 30 minutes to obtain a suspension. In an ice-water bath, 0.75 g of glacial acetic acid and 6 g of tetraisopropyl titanate were premixed for 22 min to form a stable complex, yielding mixture B. Mixture B was added dropwise to the above suspension, and stirring was continued for 1 h. Then, 3.5 g of deionized water was added, and the mixture was heated and stirred at 60 °C for 6 h. After the reaction was complete, centrifugation (8000 rpm, 10 min) was performed to obtain precipitate B. Precipitate B was washed three times with anhydrous ethanol and dried under vacuum at 80 °C for 12 h to obtain α-zirconium phosphate-titanium dioxide composite nanosheets.

[0036] A2: 2.75 g of α-zirconium phosphate-titanium dioxide composite nanosheets were dispersed in 90 g of deionized water and ultrasonically dispersed for 30 min. 1.4 g of octadecyltrimethylammonium bromide was added, and the mixture was stirred in a 60 °C water bath for 27 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate C. Precipitate C was washed three times with deionized water, dried in a 60 °C vacuum drying oven for 12 h, and ground to obtain octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets.

[0037] Preparation of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite:

[0038] B1: Dissolve 17.5 g of sodium tungstate dihydrate and 2.0 g of sodium silicate nonahydrate in 60 g of deionized water and stir until completely dissolved to obtain a mixed solution. Under vigorous stirring, slowly add 4 mol / L hydrochloric acid solution to the mixed solution to adjust the pH to 1.5, and reflux at 90 °C for 7 h. After the reaction is complete, allow to cool naturally, filter to remove insoluble matter, and obtain a filtrate. Allow the filtrate to crystallize at room temperature for 24 h to obtain crystals. Wash the crystals twice with a small amount of ice water and dry under vacuum at room temperature to obtain silicotungstic acid. A modified Hummers method was used to prepare a graphene oxide dispersion: 135 g of 98% concentrated sulfuric acid was measured and placed in a reaction vessel in an ice-water bath. 6.5 g of natural flake graphite and 3.2 g of sodium nitrate were added sequentially with stirring, followed by the slow addition of 17.5 g of potassium permanganate. The reaction was carried out at a temperature below 10 °C for 2 hours. The temperature was then raised to 35 °C and stirring continued for 2 hours. 225 g of deionized water was then slowly added dropwise, and the temperature was raised to 90 °C with stirring for 15 minutes. 12.5 g of 30% hydrogen peroxide solution was then added to reduce the residual oxidant, turning the solution a bright yellow. After centrifugation, the solution was washed three times with 5% hydrochloric acid solution, followed by washing with deionized water until neutral, yielding a washed solid. The washed solid was added to 125 g of deionized water and ultrasonically exfoliated for 1 hour to obtain a graphene oxide dispersion. The pH of the graphene oxide dispersion was adjusted to 2.5 with dilute hydrochloric acid to obtain an acidified graphene oxide dispersion. Take 65g of acidified graphene oxide dispersion with a concentration of 2mg / mL, add 0.85g of the silicotungstic acid prepared above, sonicate for 1h and then stir for 12h, centrifuge (8000rpm, 10min) to obtain precipitate D. Wash precipitate D three times with deionized water and vacuum dry at 37.5℃ for 24h to obtain silicotungstic acid-graphene oxide composite.

[0039] B2: 1.75 g of silicotungstic acid-graphene oxide composite was dispersed in 60 g of anhydrous ethanol and ultrasonically dispersed for 30 min. 1.0 g of 1-ethyl-3-methylimidazolium tetrafluoroborate was added, and the mixture was stirred in a 50 °C water bath for 27 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate E. Precipitate E was washed three times with anhydrous ethanol, dried in a vacuum drying oven at 32.5 °C for 18 h, and ground to obtain the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite.

[0040] Example 2

[0041] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a drilling fluid anti-collapse lubricant, the steps of which include:

[0042] S1: Add 70g of deionized water to a reactor and heat to 50℃; add 1g of polyanionic cellulose, 2g of carboxymethyl starch and 3g of sulfonated asphalt, and stir for 30min to obtain a gel. While stirring, add 0.5g of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets to the gel, and sonicate for 10min. Then add 0.3g of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, and shear disperse for 15min to obtain a mixture.

[0043] S2: Add 5g of white oil and 1g of Tween-60 to the mixture and stir at 55℃ for 40min; finally, add 0.1g of organosilicon defoamer and 0.1g of sodium benzoate in sequence and continue stirring for 15min; let it cool naturally to room temperature to obtain the drilling fluid anti-collapse lubricant.

[0044] Preparation of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets:

[0045] A1: 100g of a 10mol / L phosphoric acid aqueous solution was added to a reaction vessel to obtain a phosphoric acid solution. 5g of zirconium oxychloride octahydrate was dissolved in 20g of deionized water to form a clear solution. Under stirring, this clear solution was slowly added dropwise to the phosphoric acid solution at a rate of 5 drops / min for 30 minutes to obtain mixture A. Mixture A was transferred to a polytetrafluoroethylene-lined high-pressure reaction vessel, sealed, and placed in a forced-air drying oven for a constant temperature reaction at 178℃ for 48 hours. After the reaction, the mixture was allowed to cool naturally to room temperature and centrifuged (8000rpm, 10min) to obtain precipitate A. Precipitate A was washed three times each with deionized water and anhydrous ethanol by alternating centrifugation, dried in a vacuum drying oven at 78℃ for 24 hours, and ground to obtain α-zirconium phosphate powder. 2g of α-zirconium phosphate powder was dispersed in 80g of anhydrous ethanol and ultrasonically dispersed for 30 minutes to obtain a suspension. In an ice-water bath, 0.5 g of glacial acetic acid and 4 g of tetraisopropyl titanate were premixed for 15 min to form a stable complex, yielding mixture B. Mixture B was added dropwise to the above suspension, and stirring was continued for 1 h. Then, 2 g of deionized water was added, and the mixture was heated and stirred at 58 °C for 6 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate B. Precipitate B was washed three times with anhydrous ethanol and dried under vacuum at 78 °C for 12 h to obtain α-zirconium phosphate-titanium dioxide composite nanosheets.

[0046] A2: 1.5 g of α-zirconium phosphate-titanium dioxide composite nanosheets were dispersed in 80 g of deionized water and ultrasonically dispersed for 30 min. 0.8 g of octadecyltrimethylammonium bromide was added, and the mixture was stirred in a 58 °C water bath for 24 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate C. Precipitate C was washed three times with deionized water, dried in a 58 °C vacuum drying oven for 12 h, and ground to obtain octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets.

[0047] Preparation of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite:

[0048] B1: Dissolve 15g of sodium tungstate dihydrate and 1.5g of sodium silicate nonahydrate in 50g of deionized water and stir until completely dissolved to obtain a mixed solution. Under vigorous stirring, slowly add 4mol / L hydrochloric acid solution to the mixed solution to adjust the pH to 1.0, and reflux at 88℃ for 6 hours. After the reaction is complete, allow to cool naturally, filter to remove insoluble matter, and obtain a filtrate. Allow the filtrate to crystallize at room temperature for 24 hours to obtain crystals. Wash the crystals twice with a small amount of ice water and dry under vacuum at room temperature to obtain silicotungstic acid. A modified Hummers method was used to prepare a graphene oxide dispersion: 120 g of concentrated sulfuric acid was measured and placed in a reaction vessel in an ice-water bath. 5 g of natural flake graphite and 2.5 g of sodium nitrate were added sequentially with stirring, followed by the slow addition of 15 g of potassium permanganate. The reaction was carried out at a temperature below 10 °C for 2 hours. The temperature was then raised to 35 °C and stirring continued for 2 hours. 200 g of deionized water was then slowly added dropwise, and the temperature was raised to 88 °C. Stirring continued for 15 minutes. 10 g of 30% hydrogen peroxide solution was then added to reduce the residual oxidant, turning the solution a bright yellow. After centrifugation, the solution was washed three times with 5% hydrochloric acid solution, and then washed with deionized water until neutral, yielding a washed solid. The washed solid was added to 50 g of deionized water and ultrasonically exfoliated for 1 hour to obtain a graphene oxide dispersion. The pH of the graphene oxide dispersion was adjusted to 2.0 with dilute hydrochloric acid to obtain an acidified graphene oxide dispersion. Take 50g of acidified graphene oxide dispersion with a concentration of 2mg / mL, add 0.5g of the silicotungstic acid prepared above, sonicate for 1h and then stir for 12h, centrifuge (8000rpm, 10min) to obtain precipitate D. Wash precipitate D three times with deionized water and vacuum dry at 35℃ for 24h to obtain silicotungstic acid-graphene oxide composite.

[0049] B2: 1.0 g of silicotungstic acid-graphene oxide composite was dispersed in 50 g of anhydrous ethanol and ultrasonically dispersed for 30 min. 0.5 g of 1-ethyl-3-methylimidazolium tetrafluoroborate was added, and the mixture was stirred in a water bath at 48 °C for 24 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate E. Precipitate E was washed three times with anhydrous ethanol, dried in a vacuum drying oven at 30 °C for 12 h, and ground to obtain the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite.

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing a drilling fluid anti-collapse lubricant, the steps of which include:

[0052] S1: Add 90g of deionized water to a reactor and heat to 60℃; add 3g of polyanionic cellulose, 5g of carboxymethyl starch and 8g of sulfonated asphalt, and stir for 45min to obtain a gel. While stirring, add 2g of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets to the gel, and sonicate for 20min. Then add 1.5g of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, and shear disperse for 20min to obtain a mixture.

[0053] S2: Add 15g of white oil and 3g of Tween-80 to the mixture and stir at 65℃ for 60min; finally, add 0.5g of organosilicon defoamer and 0.3g of sodium benzoate in sequence and continue stirring for 20min; let it cool naturally to room temperature to obtain the drilling fluid anti-collapse lubricant.

[0054] Preparation of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets:

[0055] A1: 150g of a 12mol / L phosphoric acid aqueous solution was added to a reaction vessel to obtain a phosphoric acid solution. 10g of zirconium oxychloride octahydrate was dissolved in 30g of deionized water to form a clear solution. Under stirring, the clear solution was slowly added dropwise to the phosphoric acid solution at a rate of 10 drops / min for 30 minutes to obtain mixture A. Mixture A was transferred to a polytetrafluoroethylene-lined high-pressure reaction vessel, sealed, and placed in a forced-air drying oven for 50 hours at 182℃. After the reaction, the mixture was allowed to cool naturally to room temperature and centrifuged (8000rpm, 10min) to obtain precipitate A. Precipitate A was washed three times each with deionized water and anhydrous ethanol by alternating centrifugation, dried in a vacuum drying oven at 82℃ for 24 hours, and ground to obtain α-zirconium phosphate powder. 5g of α-zirconium phosphate powder was dispersed in 120g of anhydrous ethanol and ultrasonically dispersed for 30 minutes to obtain a suspension. In an ice-water bath, 1 g of glacial acetic acid and 8 g of tetraisopropyl titanate were premixed for 30 min to form a stable complex, yielding mixture B. Mixture B was added dropwise to the above suspension, and stirring was continued for 1 h. Then, 5 g of deionized water was added, and the mixture was heated and stirred at 62 °C for 6 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate B. Precipitate B was washed three times with anhydrous ethanol and dried under vacuum at 82 °C for 12 h to obtain α-zirconium phosphate-titanium dioxide composite nanosheets.

[0056] A2: 4g of α-zirconium phosphate-titanium dioxide composite nanosheets were dispersed in 100g of deionized water and ultrasonically dispersed for 30min. 2g of octadecyltrimethylammonium bromide was added, and the mixture was stirred in a 62℃ water bath for 30h. After the reaction was complete, the mixture was centrifuged (8000rpm, 10min) to obtain precipitate C. Precipitate C was washed three times with deionized water, dried in a 62℃ vacuum drying oven for 12h, and then ground to obtain octadecyltrimethylammonium bromide-intercalated α-zirconium phosphate-titanium dioxide composite nanosheets.

[0057] Preparation of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite:

[0058] B1: Dissolve 20g of sodium tungstate dihydrate and 2.5g of sodium silicate nonahydrate in 70g of deionized water, stirring until completely dissolved to obtain a mixed solution. Under vigorous stirring, slowly add 4mol / L hydrochloric acid solution dropwise to the mixed solution to adjust the pH to 2.0, and reflux at 92℃ for 8 hours. After the reaction is complete, allow to cool naturally, filter to remove insoluble matter, and obtain a filtrate. Allow the filtrate to crystallize at room temperature for 24 hours to obtain crystals. Wash the crystals twice with a small amount of ice water, and dry under vacuum at room temperature to obtain silicotungstic acid. A modified Hummers method was used to prepare a graphene oxide dispersion: 150g of concentrated sulfuric acid was placed in a reaction vessel in an ice-water bath. 8g of natural flake graphite and 4g of sodium nitrate were added sequentially with stirring, followed by the slow addition of 20g of potassium permanganate. The reaction was carried out at a temperature below 10℃ for 2 hours. The temperature was then raised to 35℃ and stirring continued for 2 hours. 250g of deionized water was then slowly added dropwise, and the temperature was raised to 92℃ with stirring continued for 15 minutes. 15g of 30% hydrogen peroxide solution was then added to reduce the residual oxidant, turning the solution a bright yellow. After centrifugation, the solution was washed three times with 5% hydrochloric acid solution, and then washed with deionized water until neutral, yielding a washed solid. The washed solid was added to 200g of deionized water and ultrasonically exfoliated for 1 hour to obtain a graphene oxide dispersion. The pH of the graphene oxide dispersion was adjusted to 3.0 with dilute hydrochloric acid to obtain an acidified graphene oxide dispersion. Take 80g of acidified graphene oxide dispersion with a concentration of 2mg / mL, add 1.2g of the silicotungstic acid prepared above, sonicate for 1h and then stir for 12h, centrifuge (8000rpm, 10min) to obtain precipitate D. Wash precipitate D three times with deionized water and dry under vacuum at 40℃ for 24h to obtain silicotungstic acid-graphene oxide composite.

[0059] B2: 2.5 g of silicotungstic acid-graphene oxide composite was dispersed in 70 g of anhydrous ethanol and ultrasonically dispersed for 30 min. 1.5 g of 1-ethyl-3-methylimidazolium tetrafluoroborate was added, and the mixture was stirred in a water bath at 52 °C for 30 h. After the reaction was complete, the mixture was centrifuged (8000 rpm, 10 min) to obtain precipitate E. Precipitate E was washed three times with anhydrous ethanol, dried in a vacuum drying oven at 35 °C for 24 h, and ground to obtain the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 2 is that, in step S1, octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets are not added, but only 0.9g of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite is added.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 2 is that, in step S1, 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite is not added, but only 1.25g of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets are added.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 2 is that octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets are not added in step S1, nor are 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composites.

[0066] The performance of the drilling fluid anti-collapse lubricants obtained in Examples 1-3 and Comparative Examples 1-3 were tested in accordance with national and industry standard testing specifications.

[0067] Linear expansion rate test: An NP-01 shale expansion tester was used. 10.0 g of calcium-based bentonite passing through a 100-mesh sieve (0.150 mm aperture) was weighed and pressed at 10.0 MPa for 10.0 min to prepare a core sample with a diameter of 25.0 mm and a height of 10.0 mm. The core sample was placed in a test tube, and 350 mL of the drilling fluid system to be tested was added. The expansion height increment (mm) of the core was recorded after 24.0 h. The linear expansion rate was calculated using the formula: Linear expansion rate (%) = (Expansion height increment / Initial core height 10.0 mm) × 100%. Each sample was tested three times, and the arithmetic mean was taken.

[0068] 120℃ Rolling Recovery Test: Take 50.0g of shale cuttings that passed through a 6-mesh sieve (3.35mm aperture) but remained on a 10-mesh sieve (1.70mm aperture), add it to 350mL of the drilling fluid system to be tested, place it in an aging tank, and roll it at 120.0℃ for 16.0h. After aging, cool to room temperature, and pass the aged drilling fluid and cuttings together through a 40-mesh sieve (0.42mm aperture). Collect the remaining cuttings, dry them at 105.0℃ for 4.0h, and weigh them (accurate to 0.01g). Calculate the rolling recovery rate using the formula: Rolling recovery rate (%) = (mass of dried cuttings remaining on the sieve / 50.0g) × 100%. Test each sample 3 times and take the arithmetic mean.

[0069] Lubrication coefficient reduction rate test: A GNF-1 high-temperature, high-pressure extreme-pressure lubrication instrument was used. At room temperature (25.0±1.0℃), 50.0 mL of the drilling fluid system to be tested was placed in a test cup, rotated at 150 rpm, and a torque of 150 in-lb (1 in-lb = 0.113 N·m) was applied to determine the lubrication coefficient. A bentonite-based slurry (prepared in the same way as the drilling fluid system to be tested) without any anti-collapse lubricant was used as a blank control, and the blank lubrication coefficient was determined. The lubrication coefficient reduction rate was calculated according to the formula: Lubrication coefficient reduction rate (%) = (Blank lubrication coefficient - Sample lubrication coefficient) / Blank lubrication coefficient × 100%. Each sample was tested 3 times, and the arithmetic mean was taken.

[0070] Lubrication coefficient reduction rate test after aging at 180℃: The drilling fluid system to be tested was placed in an aging tank and aged at 180.0℃ for 16.0h. After cooling to room temperature, the lubrication coefficient of the aged drilling fluid was determined according to the above-mentioned lubrication coefficient reduction rate test method, and the lubrication coefficient reduction rate after aging was calculated. Each sample was tested 3 times, and the arithmetic mean was taken.

[0071] Lubrication coefficient reduction rate retention rate test at 180℃: The lubrication coefficient reduction rate retention rate at 180℃ is calculated using the formula: Retention rate (%) = (Lubrication coefficient reduction rate after aging at 180℃ / Lubrication coefficient reduction rate before aging) × 100%. The lubrication coefficient reduction rate before aging is the lubrication coefficient reduction rate measured before aging. Calculation is performed once for each sample.

[0072] Lubrication coefficient reduction rate test after 15% NaCl salt resistance: 15.0 g / 100 mL of sodium chloride (i.e., the mass of NaCl added is 15% of the drilling fluid volume, i.e., 52.5 g NaCl is added for 350 mL of drilling fluid) was added. After stirring and dissolving, the fluid was rolled and aged at 150.0℃ for 16.0 h. After cooling to room temperature, the lubrication coefficient of the drilling fluid after salt resistance aging was determined according to the above-mentioned lubrication coefficient reduction rate test method, and the lubrication coefficient reduction rate was calculated. Each sample was tested 3 times, and the arithmetic mean was taken.

[0073] 15% NaCl Salt Resistance Retention Rate Test: The retention rate after 15% NaCl salt resistance is calculated using the formula: Retention Rate (%) = (Reduction Rate of Lubricating Coefficient after 15% NaCl Salt Resistance / Reduction Rate of Lubricating Coefficient without Salt and Aging) × 100%. The reduction rate of lubricating coefficient without salt and aging is the reduction rate of lubricating coefficient measured without aging or salt addition. Calculation is performed once for each sample.

[0074] The performance test data above are shown in Table 1.

[0075] Table 1: Performance Test Results

[0076] The test results in Table 1 above clearly show that Examples 1-3 significantly solve the technical problems of existing drilling fluid additives having single function, difficulty in achieving both anti-collapse and lubrication performance, and insufficient temperature and salt resistance compared to Comparative Examples 1-3.

[0077] Specifically, the 24-hour linear expansion rates of Examples 1-3 were all below 26%, while those of Comparative Example 1 were as high as 42.6%, Comparative Example 2 was 38.4%, and Comparative Example 3 was as high as 68.7%. This indicates that the present invention, through the synergistic combination of two inorganic modified compounds (octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets and 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite), can effectively inhibit the hydration expansion of clay and solve the problem of poor anti-collapse effect of traditional anti-collapse agents.

[0078] The rolling recovery rates at 120°C in Examples 1-3 were all above 88%, while those in Comparative Example 1 were only 71.5%, Comparative Example 2 was 75.2%, and Comparative Example 3 was as low as 45.8%. This indicates that the two components can form a dense sealing film when they work together, which significantly improves wellbore stability.

[0079] In terms of lubrication performance, the lubrication coefficient reduction rate of Examples 1-3 all exceeded 62%, while that of Comparative Example 1 was only 32.6%, Comparative Example 2 was 48.9%, and Comparative Example 3 was only 12.4%. This proves that the two modified compounds (octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets and 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite) are positively and negatively charged, respectively. They form a uniformly dispersed system in drilling fluid and synergistically form a physical isolation layer and a chemical adsorption film, thereby significantly reducing friction.

[0080] In terms of temperature resistance, the lubrication coefficient reduction rate of Examples 1-3 after aging at 180℃ was all higher than 88%, while that of Comparative Example 1 was only 75.2%, Comparative Example 2 was 82.2%, and Comparative Example 3 was only 69.4%, which demonstrates the high thermal stability of the inorganic modified compounds (zirconium α-phosphate, titanium dioxide, silicotungstic acid, and graphene oxide).

[0081] Regarding salt resistance, Examples 1-3 maintained a retention rate of over 80% after salt treatment with 15% NaCl, while Comparative Example 1 only maintained 65.3%, Comparative Example 2 74.6%, and Comparative Example 3 only 58.1%, demonstrating that both modified compounds maintained structural integrity and functional stability under salt immersion conditions. Comparative Example 1 lacked octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets, resulting in a significant decrease in anti-collapse and temperature / salt resistance properties. Comparative Example 2 lacked the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, significantly reducing lubrication and salt resistance properties. Comparative Example 3 lacked both components, resulting in the worst performance in all aspects.

[0082] Therefore, it can be seen that there is a significant synergistic effect between the octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets and the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite in this invention. Only by using the two together can excellent anti-collapse performance, lubrication performance, temperature resistance and salt resistance be achieved simultaneously, thus comprehensively solving the problem that single additives or simple mixing of multiple components in the prior art cannot achieve multiple functions.

Claims

1. A method for preparing a drilling fluid anti-collapse lubricant, characterized in that the steps include... include: S1. Add 70-90 parts by weight of deionized water to the reactor and heat to 50-60℃. Add 1-3 parts of polyanionic cellulose, 2-5 parts of modified starch and 3-8 parts of sulfonated asphalt, stir to obtain a glue solution; while stirring, add 0.5-2 parts of octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets to the glue solution, after ultrasonic stirring, add 0.3-1.5 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite, shear dispersion to obtain a mixture; S2. Add 5-15 parts of lubricant and 1-3 parts of surfactant to the mixture and stir at 55-65℃; finally, add 0.1-0.5 parts of defoamer and 0.1-0.3 parts of preservative in sequence and continue stirring; let it cool naturally to room temperature.

2. The method for preparing the drilling fluid anti-collapse lubricant according to claim 1, characterized in that, In step S1, the modified starch is carboxymethyl starch.

3. The method for preparing the drilling fluid anti-collapse lubricant according to claim 1, characterized in that, In step S2, the lubricant is white oil; the surfactant is Tween-80 or Tween-60; the defoamer is an organosilicone defoamer; and the preservative is sodium benzoate.

4. The method for preparing the drilling fluid anti-collapse lubricant according to claim 1, characterized in that, The preparation method of the octadecyltrimethylammonium bromide intercalated α-zirconium phosphate-titanium dioxide composite nanosheets includes: A1. By weight, add 100-150 parts of phosphoric acid aqueous solution to a reaction vessel to obtain a phosphoric acid solution; dissolve 5-10 parts of zirconium oxychloride octahydrate in 20-30 parts of deionized water, add to the phosphoric acid solution, and stir continuously to obtain mixture A; transfer mixture A to a reaction vessel, seal it, and place it in a forced-air drying oven at 178-182℃; after the reaction is completed, allow it to cool naturally to room temperature, centrifuge to obtain precipitate A; wash precipitate A with deionized water and anhydrous ethanol, dry it in a vacuum drying oven at 78-82℃, grind it, and obtain α- Zirconium phosphate powder; 2-5 parts of α-zirconium phosphate powder were dispersed in 80-120 parts of anhydrous ethanol and ultrasonically dispersed to obtain a suspension; 0.5-1 parts of glacial acetic acid and 4-8 parts of tetraisopropyl titanate were premixed in an ice-water bath to obtain mixture B; mixture B was added dropwise to the suspension and stirred continuously, 2-5 parts of deionized water were added, and the mixture was heated and stirred at 58-62℃. After the reaction was completed, the mixture was centrifuged to obtain precipitate B; precipitate B was washed with anhydrous ethanol and vacuum dried at 78-82℃ to obtain α-zirconium phosphate-titanium dioxide composite nanosheets; A2. Disperse 1.5-4 parts of α-zirconium phosphate-titanium dioxide composite nanosheets in 80-100 parts of deionized water, ultrasonically disperse, add 0.8-2 parts of octadecyltrimethylammonium bromide, stir and react in a water bath at 58-62℃, after the reaction is complete, centrifuge to obtain precipitate C; wash precipitate C with deionized water, dry in a vacuum drying oven at 58-62℃, and grind.

5. The method for preparing the drilling fluid anti-collapse lubricant according to claim 4, characterized in that, In step A1, the reaction time is 48-50 h at 178-182℃.

6. The method for preparing the drilling fluid anti-collapse lubricant according to claim 4, characterized in that, In step A2, the reaction is stirred in a water bath at 58-62℃ for 24-30 hours.

7. The method for preparing the drilling fluid anti-collapse lubricant according to claim 1, characterized in that, The preparation method of the 1-ethyl-3-methylimidazolium tetrafluoroborate hybrid silicotungstic acid-graphene oxide composite includes: B1. By weight, dissolve 15-20 parts of sodium tungstate dihydrate and 1.5-2.5 parts of sodium silicate nonahydrate in 50-70 parts of deionized water, stir, and obtain a mixed solution; while stirring, add hydrochloric acid solution dropwise to the mixed solution to adjust the pH to 1.0-2.0, reflux at 88-92℃, and after the reaction is complete, cool naturally, filter, and obtain filtrate; let the filtrate stand at room temperature to crystallize, and obtain crystals; wash the crystals with ice water, and vacuum dry at room temperature to obtain silicotungstic acid; adjust the pH of the graphene oxide dispersion to 2.0-3.0 with dilute hydrochloric acid to obtain an acidified graphene oxide dispersion; add 50-80 parts of the acidified graphene oxide dispersion to 0.5-1.2 parts of silicotungstic acid, disperse ultrasonically, stir, and centrifuge to obtain precipitate D; wash precipitate D with deionized water, and vacuum dry at 35-40℃ to obtain the complex; B2. Disperse 1.0-2.5 parts of the complex in 50-70 parts of anhydrous ethanol. After ultrasonic dispersion, add 0.5-1.5 parts of 1-ethyl-3-methylimidazolium tetrafluoroborate. Stir the reaction in a water bath at 48-52℃. After the reaction is complete, centrifuge to obtain precipitate E. Wash precipitate E with anhydrous ethanol, dry it in a vacuum drying oven at 30-35℃, and grind it.

8. The method for preparing the drilling fluid anti-collapse lubricant according to claim 7, characterized in that, The preparation steps of the graphene oxide dispersion include: by weight, placing 120-150 parts of concentrated sulfuric acid in a reaction vessel in an ice-water bath, stirring, then adding 5-8 parts of natural flake graphite and 2.5-4 parts of sodium nitrate, followed by 15-20 parts of potassium permanganate, and reacting at below 10°C; raising the temperature to 34-36°C and continuing stirring, then adding 200-250 parts of deionized water, raising the temperature to 88-92°C, and continuing stirring; adding 10-15 parts of hydrogen peroxide solution; centrifuging to obtain a solid; washing the solid with hydrochloric acid solution, then washing it with deionized water to obtain a washed solid; adding 50-200 parts of deionized water to the washed solid and ultrasonically exfoliating it.

9. The method for preparing the drilling fluid anti-collapse lubricant according to claim 7, characterized in that, In step B1, the reflux reaction at 88-92℃ takes 6-8 hours; in step B2, the stirring reaction in a water bath at 48-52℃ takes 24-30 hours.

10. A drilling fluid anti-collapse lubricant, characterized in that, The drilling fluid anti-collapse lubricant is prepared by the method according to any one of claims 1-9.

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