High-water-resistance and high-adhesion drilling tool thread compound and preparation method thereof

Abstract

The invention belongs to the technical field of lubricating grease, and relates to high-water-resistance and high-adhesion drilling tool thread grease and a preparation method thereof. The thread compound is prepared from base oil, a composite thickening agent, a water-resistant reinforcing agent, an adhesion promoter, a self-repairing active particle anti-wear agent and the like through a specific process. The self-repairing function of response-filling-crosslinking can be achieved through the self-repairing active particle anti-wear agent, a compact colloid structure is constructed through synergistic crosslinking of the composite thickening agent and the base oil, a hydrophobic protective film is formed through combination of the composite thickening agent and the water-resistant reinforcing agent, and the interface adsorption capacity is improved through combination of the adhesion accelerant; the product can still keep excellent water separation resistance and adhesion stability in saturated saline water and high-temperature and high-pressure water invasion environments, thread grease loss and thread joint corrosion and drill jamming are prevented, and the high requirements of severe operation environments with high humidity and strong water invasion characteristics such as deep wells, ultra-deep wells and offshore drilling are met.

Description

Technical Field

[0001] This invention belongs to the field of lubricating grease technology, and in particular relates to a high water-resistant and high-adhesion drill thread grease and its preparation method. Background Technology In oil and gas drilling, threaded joints are critical components connecting various drill string parts, directly bearing the torque, tension, pressure, and impact loads during drilling operations. Thread adhesive wear occurs under sliding friction conditions when the relative sliding between the threaded pairs is minimal. As adhesive wear progresses, material transfer from the thread friction surfaces intensifies, increasing surface roughness between the threads. Due to adhesive wear, this can eventually lead to thread seizure. Simultaneously, drill strings face corrosion from complex downhole media such as high temperatures, high pressures, water vapor, and drilling fluids (containing large amounts of water, salts, and chemicals). Drill string grease, as a complementary protective material for threaded joints, primarily functions to lubricate, seal, prevent corrosion, and prevent jamming. Its performance directly impacts the service life of the drill string and the safety and economy of drilling operations.

[0002] As drilling technology expands into deep wells, ultra-deep wells, and offshore applications, the operating environment is becoming increasingly harsh: downhole temperatures can reach over 200°C, pressures exceed 100 MPa, and drilling fluids have high water content. Under some conditions, drill string threads need to be in direct contact with saturated brine or be continuously submerged in water. Traditional drill string thread greases generally suffer from insufficient water resistance and poor adhesion: in a water-submerged environment, thread grease is prone to emulsification, oil separation, and loss, resulting in the loss of effective protection on the thread surface, which can lead to corrosion, stuck drill string, or even drill string breakage. Simultaneously, due to insufficient adhesion between the thread grease and the metal thread surface, it is prone to peeling and detachment during high-torque tightening and repeated loading and unloading, failing to form a continuous and stable lubricating sealing film. This severely affects drilling efficiency and can even lead to safety accidents.

[0003] In existing technologies, the petroleum industry both domestically and internationally has made numerous attempts to improve the water resistance and adhesion of threadlocker grease. Chinese Patent Publication No. CN112175700B discloses an improved drill thread sealing grease and its preparation method. It is prepared from base oil, benzotriazole, sodium sebate, polyisobutylene, polymethyl methacrylate, activated bentonite powder, methanol solution, columnar graphite, flake graphite, zinc powder, ultrafine stone powder, and flake copper powder. The sealing grease prepared using this method exhibits high and low temperature resistance, water resistance, chemical stability, and shear resistance, while also reducing contamination of drilling mud. However, its water resistance is only sufficient for general humid environments; it easily fails under saturated brine immersion, and its adhesion is not significantly improved.

[0004] Chinese patent CN116925834B discloses a self-healing, high-oxygen-concentration, corrosion-resistant thread sealant and its preparation method. The disclosed thread sealant comprises: 50-60% composite base grease, 10-15% water-absorbing and expanding resin, 1-2% polyisobutylene, 1-2% polymethyl methacrylate, 1-2% magnetic fluid, 3-6% dispersant, 2-3% acrylated phosphate ester, 2-4% expanded graphite powder, and 6-30% oxygen generator. While the addition of water-absorbing and expanding resin improves sealing, this technology affects the product's water resistance and increases the grease's cone penetration, reducing its fluidity and affecting application. Furthermore, the expanded graphite powder reduces the compatibility of the grease with the metal surface, weakening its adhesion.

[0005] Therefore, developing a drill thread grease that combines excellent high water resistance (resisting saturated salt water, high temperature and high pressure water intrusion, non-emulsification, non-oil separation, and non-loss) and high adhesion (firmly adsorbed on the surface of metal threads, resistant to torque and erosion), while meeting comprehensive performance requirements such as lubrication, sealing, and corrosion prevention, has become the key to solving the problem of drill thread protection under harsh working conditions such as deep wells and offshore drilling. It is especially suitable for harsh operating environments with high humidity and strong water intrusion, such as deep wells, ultra-deep wells, and offshore drilling. Summary of the Invention

[0006] To address the problems of insufficient water resistance and poor adhesion of existing drill thread greases, which make them unsuitable for harsh working conditions such as deep wells and offshore drilling with high water intrusion, the primary objective of this invention is to provide a drill thread grease with high water resistance and high adhesion. This drill thread grease has significantly improved overall performance through a rational setting of the weight composition of each raw material. It can overcome the stability problems caused by high and low temperature changes, meeting the high requirements for load resistance and anti-sticking properties of thread greases, while also possessing high water resistance and high adhesion properties. It is especially suitable for harsh operating environments with high humidity and strong water intrusion, such as deep wells, ultra-deep wells, and offshore drilling.

[0007] One of the objectives of this invention is to provide a self-healing active microparticle anti-wear agent that simultaneously possesses superior lubrication extreme pressure properties and a self-repairing effect on worn surfaces. The self-healing active microparticle anti-wear agent of this invention has good stability, is easy to disperse, and can effectively improve lubrication extreme pressure. When the threaded joint of the drill bit experiences slight wear due to high load, it can repair cavities and gaps through its self-healing function.

[0008] The second objective of this invention is to provide a method for preparing an adhesion enhancer, wherein the polar groups can form chemical adsorption with the hydroxyl groups and oxide film on the metal surface, and the non-polar groups are compatible with the base oil to form a strong adsorption film; the polymer has excellent adhesion and high temperature stability, which can enhance the cohesive force of thread grease and its physical adsorption to the metal surface. After compounding, through the synergistic effect of chemical adsorption and physical adsorption, the adhesion strength of thread grease on the metal surface is significantly improved. Even under high torque tightening, repeated loading and unloading, and drilling fluid flushing, it can still be firmly adsorbed on the thread surface without peeling or falling off.

[0009] This invention is achieved through the following technical solution: A high water-resistant and high-adhesion drill thread grease is prepared from the following raw materials in parts by weight: 25-35 parts base oil, 5-8 parts composite thickener, 5-8 parts water-resistant enhancer; 20-25 parts self-healing active microparticle anti-wear agent, 10-15 parts adhesion improver, 0.5-2.0 parts antioxidant, and 0.1-2.5 parts corrosion inhibitor.

[0010] The base oil is a linear polyethylene fully synthetic base oil and a synthetic ester oil, with a mass ratio of 7-8:1. The synthetic ester oil selected is pentaerythritol oleate, which has good biodegradability, high-temperature stability, and affinity for metals. The combination of the two ensures the fluidity of the thread-lock grease at low temperatures (for easy application) and maintains sufficient viscosity at high temperatures (to prevent runoff), while also providing a stable carrier for the dispersion of subsequent functional components.

[0011] The composite thickener is obtained by compounding activated bentonite and hydrogenated castor oil at a mass ratio of 2-3:1. Activated bentonite is an inorganic thickener with a layered structure. After dispersion in base oil, it can form a three-dimensional network colloid, improving the system's stability and anti-leakage ability. Hydrogenated castor oil is an organic thickener with good thickening effect and high-temperature stability. When compounded with activated bentonite, it can construct a denser and more stable colloidal structure through synergistic cross-linking, effectively blocking moisture intrusion, while enhancing the structural strength of the thread-locking grease and improving its adhesion durability.

[0012] The preparation method of activated bentonite is as follows: Bentonite is added to deionized water, ultrasonically dispersed for 3-5 minutes, heated to 40℃, octadecyltrimethylammonium chloride is added, stirred thoroughly, and reacted for 1-2 hours. The suspension is then removed and centrifuged at 3500 rpm, washed 2-3 times with deionized water, centrifuged again, and the solid mixture at the bottom is removed, dried and ground at 60℃ to obtain activated bentonite. The mass ratio of octadecyltrimethylammonium chloride to bentonite is 1:5. Natural bentonite is hydrophilic; only by making it lipophilic can it effectively gel in base oils and effectively prevent water intrusion.

[0013] The antioxidant is selected from one or more of diphenylamine, p-diisooctyldiphenylamine, or 2,6-tert-butyl-4-methylphenol; The preservative is selected from benzotriazoles; The water-resistant enhancing agent is modified nano-silica grafted with hydrophobic groups. Nano-silica itself has a high specific surface area and good filling properties; however, unmodified nano-silica has a hydrophilic surface and is prone to aggregation, which reduces water resistance and affects system stability. After grafting modification with trimethylchlorosilane, the surface hydroxyl groups are replaced by hydrophobic groups, significantly improving hydrophobicity, with the particle size controlled at 20–50 nm. After the addition of modified nano-silica, it can be uniformly dispersed in the colloidal system, forming a "hydrophobic barrier." On the one hand, the nanoparticles fill the gaps in the colloidal network, reducing water penetration channels; on the other hand, the hydrophobic groups synergistically work with the base oil, composite thickener, and self-healing active microparticle anti-wear agent to reduce the interfacial tension between the threadlocker grease and water, preventing emulsification and oil separation caused by water intrusion, ensuring a stable colloidal structure and preventing loss even under saturated salt water and high-temperature water immersion environments.

[0014] Nano-silica was added to anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. Trimethylchlorosilane was then added, and the mixture was refluxed at 70–80 °C for 4–6 hours. After the reaction, the mixture was filtered, washed 3–4 times with anhydrous ethanol, and dried at 100–110 °C for 2 hours to obtain modified nano-silica with surface-grafted hydrophobic groups. The mass ratio of trimethylchlorosilane to nano-silica was 0.2–0.3:1. The self-healing active microparticle anti-wear agent is prepared by using a responsive acrylic resin polymer as a carrier to encapsulate silica and expanded graphite in solid composite microspheres. S1, natural fine-flake graphite is mixed with 98% concentrated sulfuric acid, wherein the mass ratio of fine-flake graphite to concentrated sulfuric acid is 1:0.5-1.2, the reaction temperature is controlled at 25-30℃, and the reaction is carried out for 5-10 hours. The filter residue is separated from the first mixed solution by pressure filtration on a filter, washed with water until the pH value is 7, the obtained filter residue is dried at 105℃, expanded in an expansion furnace at 800-950℃, and ground to obtain nano-fine-flake high-expansion graphite.

[0015] S2, tetraethyl orthosilicate, ethanol, and deionized water are mixed at a molar ratio of 1:4:4 at 40–50°C. Dilute hydrochloric acid is added dropwise to adjust the pH to 4–5, and the mixture is stirred to form a transparent sol. Nanoscale high-expansion graphite is slowly added, and the mixture is stirred for 2–3 hours. The temperature is raised to 60°C, and the mixture is allowed to stand for 12 hours. Then, it is cooled to room temperature and allowed to stand for 24 hours. After centrifugation and filtration, gel microspheres are obtained. The microspheres are washed with water 2–3 times, dried at 60°C, and then heated to 400–500°C at a rate of 2°C / min. The temperature is maintained for 3 hours to obtain solid composite microspheres. The mass ratio of the transparent sol to the nanoscale high-expansion graphite is 2:1.

[0016] S3. In a reaction vessel equipped with a stirrer, thermometer, and condenser, methyl methacrylate, butyl acrylate, dimethylaminoethyl acrylate, hydroxypropyl acrylate, and n-dodecyl mercaptan are stirred evenly. Under nitrogen protection, the temperature is slowly raised to 100-120°C, and then the initiator tert-butyl peroxide is added dropwise. After reacting for 60-90 minutes, the temperature is lowered to 60-70°C, acrylic acid is added, and the reaction continues for 30-40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 5000-8000. By mass fraction, the amount of butyl acrylate is 30-40 parts, methyl methacrylate is 5-8 parts, acrylic acid is 5-8 parts, dimethylaminoethyl acrylate is 15-20 parts, hydroxypropyl acrylate is 10-15 parts, n-dodecyl mercaptan is 1.5-2.0 parts, and tert-butyl peroxide is 0.5-1.0 parts. Dimethylaminoethyl acrylate contains amino groups and cationic sites, while acrylic acid contains carboxyl groups and anionic sites, forming a dynamic cross-linking network of ionic bonds on the polymer molecular chain. Dodecyl mercaptan regulates the molecular weight of the polymer to obtain low molecular weight chain segments, making the chain segments more prone to peristalsis.

[0017] S4. Solid composite microspheres and responsive acrylic resin polymer were added to polyol. Under nitrogen protection, the mixture was heated to 60°C and kept in a high-speed dispersion state for 0.5 hours to form an organic phase. Under mechanical stirring at 1400 rpm, the organic phase was slowly added to a 5.0% aqueous solution of polyvinyl alcohol. After stirring for 15-20 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected, cooled to room temperature, and the polyol was removed by vacuum distillation at a low temperature of 70°C. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent. The polyol is a low molecular weight polyethylene glycol or a low molecular weight polypropylene glycol. The mass ratio of the solid composite microspheres to the responsive acrylic resin polymer is 2-3:5-6.

[0018] When the threaded joint of the drill bit is in operation, the friction causes damage to the anti-wear film. The adsorption film formed by traditional solid lubricants cannot achieve the required anti-wear effect. After tightening and loosening several times, wear and seizing cracks will occur. However, the addition of self-healing active microparticle anti-wear agent can automatically start the repair mode when wear occurs due to compression or ion release. It activates the ion-triggered responsive acrylic resin polymer, causing ionic bonds to break and reconstruct. At the same time, low molecular weight resin segments quickly diffuse to the wear site. The composite solid particles of graphite sheets and silicon-based microspheres fill the voids in the wear, and the ionic bonds re-crosslink to form a complete film, realizing the self-healing function of "response-filling-crosslinking".

[0019] Because the system also contains trimethylchlorosilane-grafted modified nano-silica and graphite sheets and silicon-based microspheres, which contain Si-OH, Si-CH3 and other groups, the Si-OH groups further react with -COOH and -NH4 groups in the responsive acrylic resin polymer. + Self-crosslinking significantly increases the crosslinking density of the system, forming a three-dimensional network structure with multiple crosslinks of ionic bonds, hydrogen bonds, and ester bonds, thereby improving the cohesion of the entire system and enhancing the erosion resistance of the repair membrane after crosslinking.

[0020] The adhesion improver is obtained by compounding hyperbranched polyamide-amine-grafted graphene oxide, polyisobutylene amine, C9 petroleum resin, polymethacrylate, and pentaerythritol oleate in a mass ratio of 0.4:1 to 1.5:1:1:2, specifically: S01, hyperbranched polyamide-amine is added to an aqueous solution of graphene oxide, and the solution is adjusted to alkalinity with a 0.05% NaOH solution. Then, 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is added. The mixture is stirred at 60-80°C for 20-24 hours. After centrifugation, washing with water, and drying, graphene oxide grafted with hyperbranched polyamide-amine is obtained. The mass ratio of graphene oxide, 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and hyperbranched polyamide-amine is 1:1:3-5; SO2, heat pentaerythritol oleate to 75-85°C, and slowly add C9 petroleum resin and polymethyl methacrylate while stirring, and continue stirring until homogeneous to form a transparent and uniform solution.

[0021] S03: Cool the transparent and uniform solution to 35-45°C, slowly add polyisobutylene amine while stirring, mix evenly, then add graphene oxide grafted with hyperbranched polyamide-amine, stir at high speed for 20-30 minutes to disperse it evenly, and obtain the adhesion improver.

[0022] Polyisobutyleneamine and graphene oxide grafted with hyperbranched polyamide-amine exhibit excellent surface activity. Their polar groups can chemically adsorb onto hydroxyl groups and oxide films on metal surfaces, while their non-polar groups are compatible with base oils, forming a robust adsorption film. Together with C9 petroleum resin, they enhance the anchoring effect and solve the problem of excessive adhesion. C9 petroleum resin and pentaerythritol oleate can act as a high-viscosity framework, further constructing a three-dimensional, high-viscosity network structure on the primary adsorption film formed by polyisobutyleneamine, thus solving the problem of prolonged adhesion. The non-polar long chains of polyisobutyleneamine, C9 petroleum resin, and base oil all have good compatibility, ensuring the uniformity and stability of the entire adsorption film. Strong chemical adsorption and physical cohesion can resist enormous shear stress. Furthermore, the film is strong and tough, not easily peeled off under mechanical action. The dense and robust adsorption film effectively blocks the penetration and displacement of media such as water and highly saturated salt water.

[0023] After compounding, the adhesion strength of thread grease on the metal surface is significantly improved through the synergistic effect of chemical adsorption and physical adsorption. Graphene oxide grafted with hyperbranched polyamide-amine serves as a grid connection point, crosslinking with modified nano-silica in the water-resistant reinforcing agent, and then crosslinking with the responsive acrylic resin polymer matrix in the self-healing active microparticle anti-wear agent to form a dense and highly adhesive oil film. Even under high torque tightening, repeated loading and unloading, and drilling fluid flushing, it can still be firmly adsorbed on the thread surface without peeling or falling off.

[0024] Finally, a method for preparing a high water-resistant and high-adhesion drill thread grease is also provided, specifically as follows: S001, heat the base oil to 40°C, then add the composite thickener, adhesion improver and water-resistant enhancer to the base oil and stir thoroughly. While stirring, raise the temperature to 100-110°C and react for 2 hours. Then cool down to 50-60°C and add the self-healing active microparticle anti-wear agent. Stir rapidly for 3 hours to obtain a homogeneous mixture. The speed of the rapid stirring is 2000-4000 rpm. S002, antioxidants and preservatives are added to the mixture in sequence, stirred evenly, and then ground 2 to 3 times by a grinding mill and homogenized once by a high-pressure homogenizer to obtain a high water-resistant and high-adhesion drill thread grease; the grinding mill is specifically a three-roll mill.

[0025] The aforementioned high water-resistant and high-adhesion drill thread grease is a self-healing drill thread grease suitable for harsh operating environments characterized by high humidity and strong water intrusion, such as deep wells, ultra-deep wells, and offshore drilling. Compared with existing technologies, the beneficial effects of this invention are: 1) The high water-resistant and high-adhesion thread grease provided by this invention is a black paste that is directly applied to the threads of the drill string casing and then tightened to a certain torque. This thread grease has both lubrication and sealing functions. It contains no heavy metal powder, is environmentally friendly, will not pollute the work site, and will not harm the drilling personnel using it. It is an environmentally friendly thread grease. Through the synergistic cross-linking of a composite thickener and base oil to construct a dense colloidal structure, combined with a water-resistant enhancer to form a hydrophobic protective film, and with an adhesion promoter to improve interfacial adsorption capacity, the product maintains excellent water separation resistance and adhesion stability even under saturated salt water and high-temperature, high-pressure water immersion environments. It can meet the lubrication performance required under various extreme working conditions, and has high water erosion resistance and high adhesion. It can adhere to the thread surface for a long time, protecting the drill string.

[0026] 2) This invention also provides a self-healing active microparticle anti-wear agent that simultaneously possesses superior lubricating extreme pressure properties and a self-repairing effect on worn surfaces. The addition of this self-healing active microparticle anti-wear agent allows for automatic activation of the repair mode upon wear occurrence due to compression or ion release. This activates the ion-triggered responsive acrylic resin polymer, causing ionic bond breakage and reconstruction, achieving a "response-filling-crosslinking" self-repair function. During the repair process, the broken ionic bonds can interact with -COOH and -NH4 groups in the responsive acrylic resin polymer via Si-OH. + It self-crosslinks and crosslinks with the active groups in the adhesion modifier containing hyperbranched polyamide-amine-grafted graphene oxide, forming a three-dimensional network structure with multiple crosslinks of ionic bonds, hydrogen bonds, and ester bonds. This improves the cohesion of the entire system, and the increased crosslink density of the resulting repair film further enhances the extreme pressure wear resistance of the film.

[0027] 3) This invention also provides a method for preparing an adhesion modifier. Polyisobutylene amine and C9 petroleum resin jointly enhance the anchoring effect, solving the problem of strong adhesion. C9 petroleum resin and pentaerythritol oleate can act as a high-viscosity skeleton, continuing to build a three-dimensional high-viscosity network structure on the primary adsorption film formed by polyisobutylene amine, solving the problem of long-lasting adhesion and ensuring the uniformity and stability of the entire adsorption film. After being compounded with water-resistant reinforcing agents, self-healing active microparticle anti-wear agents, etc., the adhesion strength of thread grease on the metal surface is significantly improved through the synergistic effect of chemical adsorption and physical adsorption. Hyperbranched polyamide-amine-grafted graphene oxide serves as a grid connection point, crosslinking with modified nano-silica in the water-resistant reinforcing agent, and then crosslinking with the responsive acrylic resin polymer matrix in the self-healing active microparticle anti-wear agent to form a dense and highly adhesive oil film. Even under high torque tightening, repeated loading and unloading, and drilling fluid flushing, it can still be firmly adsorbed on the thread surface without peeling or falling off.

[0028] 4) The high water-resistant and high adhesion drill thread grease provided by this invention can form a firm and stable film on the thread surface. This mesh-like sliding film has a dynamic sealing characteristic, which can ensure that when the threaded connection string is subjected to heavy loads and the string undergoes slight deformation, it can effectively resist the damage of large torque to the drill thread and automatically start the repair mode, which significantly enhances the anti-sticking performance. It can effectively alleviate various loads and energy transmitted from the thread, so that the thread grease is not prone to local high temperature precipitation and agglomeration, which greatly improves the stability problem of thread grease caused by high and low temperature changes during use. Attached Figure Description

[0029] Figure 1 A comparison chart of the adhesion strength of the drill thread greases obtained in Examples 1-4 and Comparative Examples 1-5, measured by the SAICAS method. Figure 2 Static water-resistant columnar comparison diagram of the drill thread greases obtained in Examples 1-4 and Comparative Examples 1-5; Figure 3 Dynamic water-resistant columnar comparison diagram of the drill thread grease obtained in Examples 1-4 and Comparative Examples 1-5. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims. Example 1 To prepare a highly water-resistant and highly adhesive drill thread grease, a water-resistant reinforcing agent was first prepared. Specifically, 20 parts of nano-silica were added to 80 parts of anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. Then, 4 parts of trimethylchlorosilane were added and refluxed at 75°C for 6 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 100°C for 2 hours to obtain modified nano-silica with hydrophobic groups grafted on its surface.

[0031] Further, a self-healing active microparticle anti-wear agent was prepared, specifically as follows: 20 parts of natural fine-flake graphite were mixed with 10 parts of 98% concentrated sulfuric acid. After reacting for 8 hours at 25°C, the filter residue was separated from the first mixed solution by pressure filtration. The residue was washed with water until the pH value was 7. The obtained filter residue was dried at 105°C and expanded in an expansion furnace at 850°C. The residue was then ground to obtain nano-fine-flake high-expansion graphite. Tetraethyl orthosilicate, ethanol, and deionized water were mixed at 50°C in a molar ratio of 1:4:4. Dilute hydrochloric acid was added dropwise to adjust the pH to 4.2. The mixture was stirred to form a transparent sol. 40 parts of the transparent sol were slowly added to 20 parts of nano-fine-flake high-expansion graphite. The mixture was stirred for 3 hours, heated to 60°C, and allowed to stand for 12 hours. Then, it was cooled to room temperature and allowed to stand for 24 hours. After centrifugation and filtration, gel microspheres were obtained. The microspheres were washed with water 2-3 times, dried at 60°C, and then heated to 400°C at a rate of 2°C / min and kept at that temperature for 3 hours to obtain solid composite microspheres. In a reactor equipped with a stirrer, thermometer, and condenser, 5 parts of methyl methacrylate, 40 parts of butyl acrylate, 15 parts of dimethylaminoethyl acrylate, 10 parts of hydroxypropyl acrylate, and 1.5 parts of n-dodecyl mercaptan were stirred until homogeneous. Under nitrogen protection, the temperature was slowly raised to 110°C, and then 0.5 parts of tert-butyl peroxide initiator were added dropwise. After reacting for 90 minutes, the temperature was lowered to 60°C, 8 parts of acrylic acid were added, and the reaction was continued for 40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 5396. 30 parts of solid composite microspheres and 50 parts of responsive acrylic resin polymer were added to 50 parts of polyethylene glycol 400. Under nitrogen protection, the mixture was heated to 60°C and maintained at high speed for 0.5 hours to form an organic phase. The organic phase was slowly added to 100 parts of a 5.0% polyvinyl alcohol aqueous solution under mechanical stirring at 1400 rpm. After stirring for 15 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected and cooled to room temperature. Polyethylene glycol 400 was removed by vacuum distillation at a low temperature of 70°C. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent.

[0032] Further, an adhesion modifier was prepared, specifically by dispersing 10 parts of graphene oxide in 90 parts of deionized water to obtain a graphene oxide solution, then adding 50 parts of hyperbranched polyamide-amine, adjusting the solution to alkalinity with a 0.05% NaOH solution, and then adding 10 parts of 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. The mixture was stirred at 80°C for 20 hours, centrifuged, washed with water, and dried to obtain graphene oxide grafted with hyperbranched polyamide-amine.

[0033] 40 parts of pentaerythritol oleate were heated to 75°C. While stirring, 20 parts of C9 petroleum resin and 20 parts of polymethacrylate were slowly added. Stirring was continued until homogeneous, forming a transparent and homogeneous solution. The transparent and homogeneous solution was cooled to 40°C. While stirring, 20 parts of polyisobutyleneamine were slowly added. After mixing evenly, 8 parts of graphene oxide grafted with hyperbranched polyamide-amine were added. The mixture was stirred at high speed for 20 minutes to disperse it evenly, thus obtaining the adhesion modifier.

[0034] Add 50 parts of bentonite to 100 parts of deionized water, ultrasonically disperse for 4 minutes, heat to 40℃, add 10 parts of octadecyltrimethylammonium chloride, stir thoroughly, react for 2 hours, take out the suspension and centrifuge at 3500 rpm, wash with deionized water 2-3 times, centrifuge again, take out the solid mixture at the bottom, dry and grind at 60℃ to obtain activated bentonite; compound 20 parts of activated bentonite with 10 parts of hydrogenated castor oil to obtain a composite thickener.

[0035] The final method for preparing a high water-resistant and high-adhesion drill thread grease is as follows: 31.1 parts of linear polyethylene fully synthetic base oil and 3.9 parts of pentaerythritol oleate are stirred evenly and heated to 40°C. Then, 8 parts of composite thickener, 10 parts of adhesion modifier, and 8 parts of water-resistant enhancer are added and stirred evenly. While stirring, the temperature is raised to 110°C and reacted for 2 hours. After cooling to 50°C, 25 parts of self-healing active microparticle anti-wear agent are added and stirred at 4000 rpm for 3 hours to obtain a homogeneous mixture. Then, antioxidants and preservatives are added to the mixture in sequence and stirred evenly. The mixture is then ground three times with a three-roll mill at a gap of 25μm→12μm→6μm, and then homogenized once with a 25MPa high-pressure homogenizer to obtain a high water-resistant and high-adhesion drill thread grease.

[0036] Example 2 To prepare a highly water-resistant and highly adhesive drill thread grease, a water-resistant reinforcing agent was first prepared. Specifically, 20 parts of nano-silica were added to 80 parts of anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. Then, 5 parts of trimethylchlorosilane were added and refluxed at 75°C for 6 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 110°C for 2 hours to obtain modified nano-silica with hydrophobic groups grafted onto its surface.

[0037] Further, a self-healing active microparticle anti-wear agent was prepared, specifically as follows: 20 parts of natural fine-flake graphite were mixed with 20 parts of 98% concentrated sulfuric acid, the reaction temperature was controlled at 25℃, and the reaction was carried out for 8 hours. The filter residue was separated from the first mixed solution by pressure filtration on a filter, washed with water until the pH value was 7, dried at 105℃, expanded in an expansion furnace at 850℃, and ground to obtain nano-fine-flake high-expansion graphite; tetraethyl orthosilicate, ethanol and deionized water were mixed at 50℃ in a molar ratio of 1:4:4, and dilute hydrochloric acid was added dropwise to adjust the pH to 4.8. The reaction was stirred to form a transparent sol; 40 parts of the transparent sol were slowly added to 20 parts of nano-fine-flake high-expansion graphite, stirred for 3 hours, heated to 60℃, and allowed to stand for 12 hours, then cooled to room temperature and allowed to stand for 24 hours. After centrifugation and filtration, gel microspheres were obtained, washed with water 2-3 times, dried at 60℃, and then heated to 500℃ at 2℃ / min and kept at that temperature for 3 hours to obtain solid composite microspheres; In a reactor equipped with a stirrer, thermometer, and condenser, 8 parts of methyl methacrylate, 30 parts of butyl acrylate, 20 parts of dimethylaminoethyl acrylate, 15 parts of hydroxypropyl acrylate, and 2.0 parts of n-dodecyl mercaptan were stirred until homogeneous. Under nitrogen protection, the temperature was slowly raised to 110°C, and then 1.0 part of tert-butyl peroxide initiator was added dropwise. After reacting for 90 minutes, the temperature was lowered to 60°C, 5 parts of acrylic acid were added, and the reaction was continued for 40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 7825. 20 parts of solid composite microspheres and 60 parts of responsive acrylic resin polymer were added to 50 parts of polyethylene glycol 400. Under nitrogen protection, the mixture was heated to 60°C and maintained at high speed for 0.5 hours to form an organic phase. The organic phase was slowly added to 100 parts of a 5.0% polyvinyl alcohol aqueous solution under mechanical stirring at 1400 rpm. After stirring for 20 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected and cooled to room temperature. Polyethylene glycol was removed by vacuum distillation at a low temperature of 70°C. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent.

[0038] Further, an adhesion modifier was prepared, specifically as follows: 10 parts of graphene oxide were dispersed in 90 parts of deionized water to obtain a graphene oxide solution, and then 30 parts of hyperbranched polyamide-amine were added. After adjusting the solution to alkalinity with a 0.05% NaOH solution, 10 parts of 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added. The mixture was stirred and reacted at 80°C for 20 hours. After centrifugation, washing with water, and drying, graphene oxide grafted with hyperbranched polyamide-amine was obtained. 40 parts of pentaerythritol oleate were heated to 85°C. While stirring, 20 parts of C9 petroleum resin and 20 parts of polymethacrylate were slowly added. Stirring was continued until homogeneous, forming a transparent and homogeneous solution. The transparent and homogeneous solution was cooled to 45°C. While stirring, 30 parts of polyisobutyleneamine were slowly added. After mixing evenly, 8 parts of graphene oxide grafted with hyperbranched polyamide-amine were added. The mixture was stirred at high speed for 30 minutes to disperse it evenly, thus obtaining the adhesion modifier.

[0039] The preparation method of activated bentonite is as follows: 50 parts of bentonite are added to 100 parts of deionized water, ultrasonically dispersed for 4 minutes, heated to 40°C, 10 parts of octadecyltrimethylammonium chloride are added, stirred thoroughly, and reacted for 2 hours. The suspension is taken out and centrifuged at 3500 rpm, washed 2-3 times with deionized water, centrifuged again, and the solid mixture at the bottom is taken out, dried and ground at 60°C to obtain activated bentonite. Then, 30 parts of activated bentonite are compounded with 10 parts of hydrogenated castor oil to obtain a composite thickener.

[0040] The last method for preparing a high water-resistant and high-adhesion drill thread grease is as follows: 28 parts of linear polyethylene fully synthetic base oil and 4 parts of pentaerythritol oleate are stirred evenly and heated to 40°C. Then, 7 parts of composite thickener, 15 parts of adhesion modifier, and 5 parts of water-resistant enhancer are added and stirred evenly. The mixture is then heated to 100°C while stirring, and reacted for 2 hours. After cooling to 60°C, 20 parts of self-healing active microparticle anti-wear agent are added. The mixture is stirred at 4000 rpm for 3 hours to obtain a homogeneous mixture. Antioxidant and preservative are then added to the mixture in sequence and stirred evenly. The mixture is then ground three times with a three-roll mill at a gap of 25μm→12μm→6μm. Finally, it is homogenized once by a 25MPa high-pressure homogenizer to obtain the high water-resistant and high-adhesion drill thread grease.

[0041] Example 3 To prepare a highly water-resistant and highly adhesive drill thread grease, a water-resistant reinforcing agent was first prepared. Specifically, 20 parts of nano-silica were added to 80 parts of anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. 6 parts of trimethylchlorosilane were added and refluxed at 75°C for 6 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 100°C for 2 hours to obtain modified nano-silica with surface-grafted hydrophobic groups. Further, a self-healing active microparticle anti-wear agent was prepared, specifically as follows: 20 parts of natural fine-flake graphite were mixed with 10 parts of 98% concentrated sulfuric acid, the reaction temperature was controlled at 25℃, and the reaction was carried out for 8 hours. The filter residue was separated from the first mixed solution by pressure filtration on a filter, washed with water until the pH value was 7, dried at 105℃, expanded in an expansion furnace at 900℃, and ground to obtain nano-fine-flake high-expansion graphite; tetraethyl orthosilicate, ethanol and deionized water were mixed at 45℃ in a molar ratio of 1:4:4, and dilute hydrochloric acid was added dropwise to adjust the pH to 4.1, and the reaction was stirred to form a transparent sol; 40 parts of transparent sol were slowly added to 20 parts of nano-fine-flake high-expansion graphite, stirred for 3 hours, heated to 60℃, and allowed to stand for 12 hours, then cooled to room temperature and allowed to stand for 24 hours. After centrifugation and filtration, gel microspheres were obtained, washed with water 2-3 times, dried at 60℃, and then heated to 450℃ at 2℃ / min and kept at that temperature for 3 hours to obtain solid composite microspheres.

[0042] In a reactor equipped with a stirrer, thermometer, and condenser, 7 parts of methyl methacrylate, 35 parts of butyl acrylate, 18 parts of dimethylaminoethyl acrylate, 12 parts of hydroxypropyl acrylate, and 1.5 parts of n-dodecyl mercaptan were stirred until homogeneous. Under nitrogen protection, the temperature was slowly raised to 110°C, and then 1.0 part of tert-butyl peroxide initiator was added dropwise. After reacting for 90 minutes, the temperature was lowered to 60°C, 7 parts of acrylic acid were added, and the reaction was continued for 40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 6539. 25 parts of solid composite microspheres and 50 parts of responsive acrylic resin polymer were added to 50 parts of polyethylene glycol. Under nitrogen protection, the mixture was heated to 60°C and maintained at high speed for 0.5 hours to form an organic phase. The organic phase was then slowly added to 100 parts of a 5.0% polyvinyl alcohol aqueous solution under mechanical stirring at 1400 rpm. After stirring for 18 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected, cooled to room temperature, and subjected to vacuum distillation at a low temperature of 70°C to remove the polyethylene glycol. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent. The polyol is a low molecular weight polyethylene glycol or a low molecular weight polypropylene glycol. Further, an adhesion modifier was prepared, specifically as follows: 10 parts of graphene oxide were dispersed in 90 parts of deionized water to obtain a graphene oxide solution, and then 40 parts of hyperbranched polyamide-amine were added. After adjusting the solution to alkalinity with a 0.05% NaOH solution, 10 parts of 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added. The mixture was stirred and reacted at 80°C for 20 hours. After centrifugation, washing with water, and drying, graphene oxide grafted with hyperbranched polyamide-amine was obtained. 40 parts of pentaerythritol oleate were heated to 80°C. While stirring, 20 parts of C9 petroleum resin and 20 parts of polymethacrylate were slowly added, and stirring was continued until homogeneous to form a transparent and homogeneous solution. The transparent and homogeneous solution was cooled to 40°C. While stirring, 20 parts of polyisobutyleneamine were slowly added. After mixing evenly, 8 parts of graphene oxide grafted with hyperbranched polyamide-amine were added. The mixture was stirred rapidly for 30 minutes to disperse it evenly, thus obtaining the adhesion modifier.

[0043] The preparation method of activated bentonite is as follows: 50 parts of bentonite are added to 100 parts of deionized water, ultrasonically dispersed for 5 minutes, heated to 40°C, 10 parts of octadecyltrimethylammonium chloride are added, stirred thoroughly, and reacted for 2 hours. The suspension is taken out and centrifuged at 3500 rpm, washed 2-3 times with deionized water, centrifuged again, and the solid mixture at the bottom is taken out, dried and ground at 60°C to obtain activated bentonite. Then, 25 parts of activated bentonite are compounded with 10 parts of hydrogenated castor oil to obtain a composite thickener.

[0044] The final method for preparing a high water-resistant and high-adhesion drill thread grease is as follows: 21.9 parts of linear polyethylene fully synthetic base oil and 3.1 parts of pentaerythritol oleate are stirred evenly and heated to 40°C. Then, 5 parts of composite thickener, 12 parts of adhesion modifier, and 6 parts of water-resistant enhancer are added and stirred evenly. While stirring, the temperature is raised to 105°C and reacted for 2 hours. After cooling to 55°C, 22 parts of self-healing active microparticle anti-wear agent are added. The mixture is stirred at 4000 rpm for 3 hours to obtain a homogeneous mixture. Antioxidant and preservative are then added to the mixture in sequence and stirred evenly. The mixture is then ground three times with a three-roll mill at a gap of 25μm→12μm→6μm. Finally, it is homogenized once by a 25MPa high-pressure homogenizer to obtain a high water-resistant and high-adhesion drill thread grease.

[0045] Example 4 To prepare a highly water-resistant and highly adhesive drill thread grease, a water-resistant reinforcing agent was first prepared. Specifically, 20 parts of nano-silica were added to 80 parts of anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. Then, 5 parts of trimethylchlorosilane were added and refluxed at 75°C for 6 hours. After the reaction was completed, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 110°C for 2 hours to obtain modified nano-silica with hydrophobic groups grafted onto its surface.

[0046] Further, a self-healing active microparticle anti-wear agent was prepared, specifically as follows: 20 parts of natural fine-flake graphite were mixed with 10 parts of 98% concentrated sulfuric acid, the reaction temperature was controlled at 25℃, and the reaction was carried out for 8 hours. The filter residue was separated from the first mixed solution by pressure filtration on a filter, washed with water until the pH value was 7, dried at 105℃, expanded in an expansion furnace at 800℃, and ground to obtain nano-fine-flake high-expansion graphite; tetraethyl orthosilicate, ethanol, and deionized water were mixed in a molar ratio of 1:4:4... Mix at 50℃, add dilute hydrochloric acid dropwise to adjust pH to 4.9, and stir to form a transparent sol. Take 40 parts of the transparent sol and slowly add 20 parts of nano-fine flake high-expansion graphite, stir for 3 hours, raise the temperature to 60℃, let stand for 12 hours, then lower to room temperature and let stand for 24 hours. After centrifugation and filtration, obtain gel microspheres, wash with water 2-3 times, dry at 60℃, raise the temperature to 500℃ at 2℃ / min, and keep at that temperature for 3 hours to obtain solid composite microspheres. The mass ratio of transparent sol to nano-fine flake high-expansion graphite is 2:1. In a reaction vessel equipped with a stirrer, thermometer, and condenser, 8 parts of methyl methacrylate, 32 parts of butyl acrylate, 20 parts of dimethylaminoethyl acrylate, 10 parts of hydroxypropyl acrylate, and 1.5 parts of n-dodecyl mercaptan were stirred until homogeneous. Under nitrogen protection, the temperature was slowly raised to 110°C, and then 0.6 parts of tert-butyl peroxide initiator were added dropwise. After reacting for 90 minutes, the temperature was lowered to 60°C, 6 parts of acrylic acid were added, and the reaction was continued for 40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 6804. 20 parts of solid composite microspheres and 50 parts of responsive acrylic resin polymer were added to 50 parts of polyethylene glycol. Under nitrogen protection, the mixture was heated to 60°C and maintained at high speed for 0.5 hours to form an organic phase. The organic phase was then slowly added to 100 parts of a 5.0% polyvinyl alcohol aqueous solution under mechanical stirring at 1400 rpm. After stirring for 18 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected, cooled to room temperature, and subjected to vacuum distillation at a low temperature of 70°C to remove the polyethylene glycol. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent. The polyol is a low molecular weight polyethylene glycol or a low molecular weight polypropylene glycol. Further, an adhesion modifier was prepared, specifically as follows: 10 parts of graphene oxide were dispersed in 90 parts of deionized water to obtain a graphene oxide solution, and then 50 parts of hyperbranched polyamide-amine were added. After adjusting the solution to alkalinity with a 0.05% NaOH solution, 10 parts of 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride were added. The mixture was stirred and reacted at 80°C for 20 hours. After centrifugation, washing with water, and drying, graphene oxide grafted with hyperbranched polyamide-amine was obtained. 40 parts of pentaerythritol oleate were heated to 85°C. While stirring, 20 parts of C9 petroleum resin and 20 parts of polymethacrylate were slowly added. Stirring was continued until homogeneous, forming a transparent and homogeneous solution. The transparent and homogeneous solution was cooled to 35°C. While stirring, 30 parts of polyisobutyleneamine were slowly added. After mixing evenly, 8 parts of graphene oxide grafted with hyperbranched polyamide-amine were added. Stirring was continued to obtain the adhesion modifier.

[0047] The preparation method of activated bentonite is as follows: 50 parts of bentonite are added to 100 parts of deionized water, ultrasonically dispersed for 5 minutes, heated to 40°C, 10 parts of octadecyltrimethylammonium chloride are added, stirred thoroughly, and reacted for 1 hour. The suspension is taken out and centrifuged at 3500 rpm, washed 2-3 times with deionized water, centrifuged again, and the solid mixture at the bottom is taken out, dried and ground at 60°C to obtain activated bentonite. Then, 20 parts of activated bentonite are compounded with 10 parts of hydrogenated castor oil to obtain a composite thickener.

[0048] The last method for preparing a high water-resistant and high-adhesion drill thread grease is as follows: 24 parts of linear polyethylene fully synthetic base oil and 3 parts of pentaerythritol oleate are stirred evenly and heated to 40°C. Then, 6 parts of composite thickener, 11 parts of adhesion modifier, and 5 parts of water-resistant enhancer are added and stirred evenly. While stirring, the temperature is raised to 110°C and reacted for 2 hours. After cooling to 60°C, 20 parts of self-healing active microparticle anti-wear agent are added and stirred at 3000 rpm for 3 hours to obtain a homogeneous mixture. Then, antioxidants and preservatives are added to the mixture in sequence and stirred evenly. The mixture is then ground three times with a three-roll mill at a gap of 25μm→12μm→6μm, and then homogenized once with a 25MPa high-pressure homogenizer to obtain the high water-resistant and high-adhesion drill thread grease.

[0049] Comparative Example 1: The self-healing active microparticle anti-wear agent was directly added to the base oil by mixing equal amounts of nano molybdenum disulfide powder, metal powder, nano mica flakes and nano fine flake high expansion graphite, and the rest was the same as the drill thread grease prepared in Example 1. Comparative Example 2: Solid composite microspheres were used to replace the self-healing active microparticle anti-wear agent in equal amounts, while the rest was the same as the drill thread grease prepared in Example 1; Comparative Example 3: No water-resistant reinforcing agent was added; instead of the adhesion modifier, an equal amount of a mixture of polyisobutylene and polymethyl methacrylate was used; otherwise, the same thread grease was prepared as in Example 1. Comparative Example 4, the drill thread sealing grease product involved in Example 3 of an improved drill thread sealing grease disclosed in Chinese Patent Publication No. CN112175700B; Comparative Example 5: A commercially available high-performance drill thread grease product.

[0050] Experimental data and results analysis 1. Comprehensive performance of drill thread grease The thread greases from Examples 1-2 and Comparative Examples 1-5 were tested according to the SY / T5198-2020 standard for working cone penetration, dropping point, evaporation rate, oil separation rate, corrosion rate, coating performance, and water leaching. The results of their physicochemical performance tests are shown in Table 1. As can be seen from Table 1, the physicochemical performance test results of the thread greases from Examples 1-2 and Comparative Examples 3-5 basically meet the basic requirements of the SY / T5198-2020 standard. However, the performance of Examples 1-2 is better, and its low-temperature performance is significantly improved compared with the comparative examples. Therefore, other more stringent testing methods are needed to evaluate its performance in harsh environments, especially its resistance to saturated salt water and high-temperature and high-pressure water intrusion, its strong adhesion to the surface of metal threads, and its torque and erosion resistance, making it suitable for harsh operating environments with high humidity and strong water intrusion, such as deep wells, ultra-deep wells, and offshore drilling.

[0051] Table 1. Test results of the physical and chemical properties of drill thread grease

[0052] 2. Adhesion test results Adhesion test method: The test method in Appendix A of SY / T 0513-2016 "Technical Conditions for Drill Thread Grease" can only qualitatively determine the adhesion performance. Therefore, we treated the 45# steel sheet using the method in Appendix A of SY / T 0513-2016 "Technical Conditions for Drill Thread Grease". The thread grease of each embodiment and comparative example was evenly applied to a 45# steel sheet, and another sheet was pressed on top to form a "sandwich" structure. A fixed tensile force was applied to squeeze out excess grease and form a uniform grease film. Then, a tensile testing machine was used to determine the peel strength between the thread grease and the 45# steel sheet. The test temperature was 23-25℃, the loading rate was 50mm / min, a 0-5kN sensor was selected, and a 180° peel mode was used. Each sample was tested three times and the average value was taken, as shown in Table 2.

[0053] Table 2 Adhesion Test Results Record Sheet

[0054] As shown in Table 2, the adhesion of Examples 1-5 and Comparative Examples 1-5 is similar when tested using conventional methods, which can meet the minimum requirements of ordinary drill thread grease.

[0055] Therefore, we immersed the coated sandwich 45# steel sheets in saturated brine for 24 hours according to the above operation for each embodiment and comparative example, and tested the adhesion of each drill thread grease in harsh environment at a test temperature of 90-100℃ using the above method, as shown in Table 3. Table 3. Record of Adhesion Test Results under Harsh Conditions

[0056] Table 3 shows that after 24 hours of soaking in saturated brine, the adhesion strength tested at high temperature showed a significant advantage for Examples 1-4. This is because the threadlocker grease in these examples constructs a dense colloidal structure through the synergistic crosslinking of the composite thickener and base oil, forming a hydrophobic protective film in combination with a water-resistant enhancer. Furthermore, the adhesion promoter enhances the interfacial adsorption capacity, enabling the product to maintain excellent water separation resistance and adhesion stability even under saturated brine and high-temperature, high-pressure water immersion environments. This system constructs a three-dimensional, high-viscosity network structure, solving the problem of prolonged adhesion and ensuring the uniformity and stability of the entire adsorption film. The adhesion promoter, combined with the water-resistant enhancer and self-healing active microparticle anti-wear agent, significantly improves the adhesion strength of the threadlocker grease on the metal surface through the synergistic effect of chemical and physical adsorption.

[0057] We further determined the adhesion strength of the material using the SAICAS method, the specific content and requirements of which are as follows: using the high-precision blades equipped with the system, the substrate coated with the test material (drill thread grease) was subjected to controlled cutting.

[0058] Operating Procedure: Step 1: Sampling and Pretreatment. Test samples of drill thread blocks coated with thread-locking grease are immersed in saturated salt water for 24 hours. After removal, ensure the test surface is flat and remove surface oil and impurities to avoid affecting cutting accuracy. Step 2: Equipment Debugging. Install and calibrate the appropriate inserts, and set the cutting parameters. Step 3: Cutting Test. Start the system and allow the inserts to cut the sample along a preset path and depth, simultaneously recording the changes in cutting force with cutting distance or depth. Step 4: Data Processing. Calculate the average force per unit insert width (F / W value), and analyze the adhesion strength data in conjunction with parameters such as cutting depth.

[0059] Environmental and parameter requirements: The testing environment must be kept at room temperature (100±2℃) and dry to avoid the influence of temperature and humidity on the adhesion layer state; the cutting parameters must be adapted to the sample, the cutting speed is usually set to 0.1-1mm / s, and the cutting depth gradually increases from the surface of the adhesion layer to the substrate, and multiple tests are required to obtain the average value. The average value of at least 3 different locations should be tested for the same batch of samples. The test results are shown in Table 4 and... Figure 1 .

[0060] Table 4. Record of Adhesion Test Results by SAICAS Method

[0061] From Table 4 and Figure 1 It can be seen that the adhesion strength measured by the SAICAS method, like the traditional peel test, can also reflect the adhesion strength of the drill thread grease. Figure 3It can be seen that the adhesion strength of Examples 1-4 is significantly higher than that of the comparative examples of drill thread grease. This data can also capture local adhesion differences at different depths, and therefore is more valuable than the previous two test methods, providing data support for optimizing drill thread grease formulations.

[0062] 3. Water resistance test results ① Static water resistance: Immerse steel sheets coated with thread grease in a 10% NaCl solution (60℃, 72h), observe for emulsification, oil separation, and loss, and calculate the mass loss rate; test results are shown in Table 5 and Figure 2 ; ② Dynamic water resistance: The threaded joint of the drill string coated with threadlocker grease was placed in a high-temperature and high-pressure autoclave to simulate downhole conditions (150℃, 100MPa, saturated brine circulation flushing for 24 hours), and the retention of threadlocker grease was observed; the test results are shown in Table 5 and Figure 3 ; Table 5 Water Resistance Test Results Record Sheet

[0063] As shown in Table 5, the threadlocker grease prepared in this embodiment exhibits a static water resistance mass loss rate of no more than 0.2%, a dynamic water resistance retention rate of over 93%, and excellent high-temperature stability. The entire system ensures the uniformity and stability of the adsorption membrane, and the dense and robust adsorption membrane effectively blocks the penetration and replacement of media such as water and highly saturated salt water. Figure 2 and Figure 3 It can be seen that the differences between the various embodiments and comparative examples in the static water resistance test are not very obvious. However, there are obvious differences in the dynamic water resistance test at high temperature. This is because after the raw materials are compounded, the adhesion improver and the water resistance enhancer significantly improve the adhesion strength of the thread grease on the metal surface through the synergistic effect of chemical adsorption and physical adsorption. In addition, the hyperbranched polyamide-amine graphene oxide grafted in the self-healing active microparticle anti-wear agent serves as a grid connection point, crosslinking with the modified nano-silica in the water resistance enhancer, and then crosslinking with the responsive acrylic resin polymer matrix in the self-healing active microparticle anti-wear agent to form a dense and highly adhesive oil film. Even under high torque tightening, repeated loading and unloading, and repeated rinsing with saturated salt water, it can still be firmly adsorbed on the thread surface without peeling or falling off, which can meet the needs of various harsh water-invaded drilling conditions.

[0064] 4. Torque Anti-hooking Performance Test One drill string external thread connector with steel grade G105 and thread type APL NC50 and one drill string internal thread connector with steel grade G105 and thread type APL NC50 were selected for the turn-on / turn-off test. According to API RP 7G "Recommended Implementation Procedures for Drill Pipe Design and Operating Limits", drill string thread grease from Examples 1-2 and Comparative Examples 1 and 4 were applied to the internal and external thread surfaces of the drill string connectors, respectively. Twenty turn-on / turn-off tests were performed at standard torque. The test results are shown in Table 6. Table 6 shows that the condition of the internal and external thread surfaces of Examples 1-2, Comparative Examples 1 and 4 was observed after 20 turn-on / turn-off tests at standard torque. The adsorption film formed by traditional solid lubricants cannot achieve the required anti-wear effect. After tightening and loosening several times, wear and cracks will occur. However, the addition of self-healing active microparticle anti-wear agent can automatically start the repair mode when wear occurs due to compression or ion release. It activates ion-triggered responsive acrylic resin polymer, causing ionic bonds to break and reconstruct. At the same time, low molecular weight resin segments rapidly diffuse to the wear site. The composite solid particles of graphite sheets and silicon-based microspheres fill the voids in the wear, and the ionic bonds are re-crosslinked to form a complete film layer, realizing the self-healing function of "response-filling-crosslinking".

[0065] Therefore, the black, viscous, paste-like threadlocker provided in this embodiment appears the same as ordinary threadlocker. When applied to the thread surface and threaded, the threadlocker fills the gaps in the threaded connection. During threading, solid particles are filled between the thread surfaces, and the polymer absorbs heat, solidifying into a resilient and sealing polymer film with a network cross-linked structure. This polymer film withstands significant torsional loads, preventing adhesion damage between the external and internal threads of the drill bit. This dense polymer film with solid particles as its framework effectively blocks direct contact between the external and internal thread surfaces, preventing mechanical damage. When wear occurs, the pressure or release of ions automatically activates a repair mode, activating the ion-triggered responsive acrylic resin polymer, causing ionic bond breakage and reconstruction. Simultaneously, low-molecular-weight resin segments rapidly diffuse to the worn area to repair the wear. It can adapt to bending and stress changes in the threaded connection, making it particularly suitable for harsh working conditions where several special operating conditions overlap.

[0066] Table 6. Results of the buckling test when the buckling torque is 41680 N·m

[0067] Final uncoupling test followed by sealing test The drill thread grease prepared in Examples 1-2 and Comparative Examples 1 and 4 were subjected to 9 unraveling tests according to GB / T21267. Then, a 10th unraveling test was performed, and an airtightness test was conducted on the casing joint. An internal pressure of 25.0 MPa was applied and the pressure was maintained for 15 minutes. Leakage was observed, and the results are shown in Table 7.

[0068] Table 7 Sealing Test Data Recording Sheet

[0069] 5. Extreme pressure anti-wear performance The MS-10A four-ball anti-wear testing machine manufactured by Xiamen Tianji Automation Co., Ltd. was used. The experimental conditions were: room temperature. The maximum non-seize load P of each thread grease was determined according to the SH / T 0202 method. B , Sintering P D Long-term wear D, and corresponding data processing, are shown in Table 8; it can be seen from Table 8 that the sintering P of Examples 1-2 D The significant increase indicates that the anti-torque performance of the thread grease corresponding to Examples 1-2 is significantly improved. This is because after the thread grease is applied to the surface of the steel ball, it is rapidly adsorbed onto the surface. Furthermore, the friction-formed film is a continuous, dense network structure, with solid microparticles connecting the entire network. This polymer film with a network cross-linked structure significantly improves load-bearing capacity and anti-sintering ability. Looking at the long-term wear data (D), Examples 1-2 also show a significant improvement compared to Comparative Examples 1-2 and 4-5. This is because the self-healing active microparticle anti-wear agent improves the wear resistance of the steel ball, resulting in a smaller wear scar area and a significant decrease in the coefficient of friction of at least 20%.

[0070] Therefore, from the non-seizure load P B , Sintering P D A comparison of parameters such as long-term wear (D) and friction coefficient shows that the thread grease provided by this invention can significantly improve the thread grease's resistance to high torque and wear, and can adapt to the torsion caused by bending and stress changes in the threaded connection. It is particularly suitable for harsh working conditions where several special working conditions are superimposed.

[0071] Table 8. Extreme Pressure Anti-wear Data Recording Table for Drill Thread Grease

[0072] This invention addresses the core pain points of existing drill bit thread greases, namely insufficient water resistance and poor adhesion. It achieves simultaneous breakthroughs in both water resistance and adhesion, while ensuring a balanced improvement in comprehensive performance such as extreme pressure anti-wear, corrosion resistance, and high-temperature stability. The product effectively solves the problem of drill bit thread protection under high water intrusion conditions such as deep wells and offshore operations, reduces drilling operation risks, extends drill bit service life, and its manufacturing process is suitable for mass production.

[0073] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A highly water-resistant and highly adhesive drill thread grease, characterized in that, The aforementioned high water-resistant and high-adhesion drill thread grease is prepared from the following raw materials in parts by weight: 25-35 parts base oil, 5-8 parts composite thickener, 5-8 parts water-resistant enhancer; 20-25 parts self-healing active microparticle anti-wear agent, 10-15 parts adhesion improver, 0.5-2.0 parts antioxidant, and 0.1-2.5 parts corrosion inhibitor; The water-resistant reinforcing agent is modified nano-silica grafted with hydrophobic groups; The self-healing active microparticle anti-wear agent is prepared by using a responsive acrylic resin polymer as a carrier to encapsulate silica and expanded graphite in solid composite microspheres. The adhesion improver is obtained by compounding graphene oxide grafted with hyperbranched polyamide-amine, polyisobutyleneamine, C9 petroleum resin, polymethyl methacrylate and pentaerythritol oleate in a mass ratio of 0.4:1 to 1.5:1:1:

2.

2. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The composite thickener is obtained by compounding activated bentonite and hydrogenated castor oil at a mass ratio of 2 to 3:

1.

3. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The method for preparing the water-resistant reinforcing agent is as follows: nano-silica is added to anhydrous ethanol and ultrasonically dispersed for 30 min to form a uniform suspension. Trimethylchlorosilane is added and refluxed at 70-80℃ for 4-6 hours. After the reaction is completed, the mixture is filtered, washed 3-4 times with anhydrous ethanol, and dried at 100-110℃ for 2 hours to obtain modified nano-silica with surface-grafted hydrophobic groups. The mass ratio of trimethylchlorosilane to nano-silica is 0.2-0.3:

1.

4. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The preparation method of the self-healing active microparticle anti-wear agent is as follows: S1, natural fine-flake graphite is mixed with 98% concentrated sulfuric acid, wherein the mass ratio of fine-flake graphite to concentrated sulfuric acid is 1:0.5-1.2, the reaction temperature is controlled at 25-30℃, and the reaction is carried out for 5-10 hours. The filter residue is separated from the first mixed solution by pressure filtration on a filter, washed with water until the pH value is 7, the obtained filter residue is dried at 105℃, expanded in an expansion furnace at 800-950℃, and ground to obtain nano-fine-flake high-expansion graphite; S2, tetraethyl orthosilicate, ethanol, and deionized water are mixed at a molar ratio of 1:4:4 at 40–50°C. Dilute hydrochloric acid is added dropwise to adjust the pH to 4–5, and the mixture is stirred to form a transparent sol. Nanoscale fine-flake high-expansion graphite is slowly added, and the mixture is stirred for 2–3 hours. The temperature is raised to 60°C, and the mixture is allowed to stand for 12 hours. Then, it is cooled to room temperature and allowed to stand for 24 hours. After centrifugation and filtration, gel microspheres are obtained. The microspheres are washed with water 2–3 times, dried at 60°C, and then heated to 400–500°C at a rate of 2°C / min and kept at that temperature for 3 hours to obtain solid composite microspheres. The mass ratio of the transparent sol to the nanoscale fine-flake high-expansion graphite is 2:

1. S3. In a reaction vessel equipped with a stirrer, thermometer, and condenser, methyl methacrylate, butyl acrylate, dimethylaminoethyl acrylate, hydroxypropyl acrylate, and n-dodecyl mercaptan are stirred evenly. Under nitrogen protection, the temperature is slowly raised to 100-120°C, and then the initiator tert-butyl peroxide is added dropwise. After reacting for 60-90 minutes, the temperature is lowered to 60-70°C, acrylic acid is added, and the reaction continues for 30-40 minutes to obtain a responsive acrylic resin polymer with an average molecular weight of 5000-8000. S4. Solid composite microspheres and responsive acrylic resin polymer were added to a polyol. Under nitrogen protection, the mixture was heated to 60°C and maintained at high speed for 0.5 hours to form an organic phase. The organic phase was slowly added to a 5.0% aqueous solution of polyvinyl alcohol under mechanical stirring at 1400 rpm. After stirring for 15-20 hours, the mixture was centrifuged at 3000 rpm for 10 minutes. The bottom solid phase was collected, cooled to room temperature, and the polyol was removed by vacuum distillation at a low temperature of 70°C. The mixture was then dried at room temperature for 72 hours to obtain a self-healing active microparticle anti-wear agent.

5. The high water-resistant and high-adhesion drill thread grease according to claim 4, characterized in that, The polyol is a low molecular weight polyethylene glycol or a low molecular weight polypropylene glycol. By mass fraction, the amount of butyl acrylate is 30-40 parts, methyl methacrylate is 5-8 parts, acrylic acid is 5-8 parts, dimethylaminoethyl acrylate is 15-20 parts, hydroxypropyl acrylate is 10-15 parts, n-dodecyl mercaptan is 1.5-2.0 parts, and tert-butyl peroxide is 0.5-1.0 parts. The mass ratio of the solid composite microspheres to the responsive acrylic resin polymer is 2-3:5-6.

6. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The adhesion improver is prepared by the following method: S01, hyperbranched polyamide-amine is added to an aqueous solution of graphene oxide, and the solution is adjusted to alkalinity with a 0.05% NaOH solution. Then, 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is added. The mixture is stirred at 60-80°C for 20-24 hours. After centrifugation, washing with water, and drying, graphene oxide grafted with hyperbranched polyamide-amine is obtained. The mass ratio of graphene oxide, 1-ethyl-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and hyperbranched polyamide-amine is 1:1:3-5; S02, heat pentaerythritol oleate to 75-85°C, and slowly add C9 petroleum resin and polymethyl methacrylate while stirring, and keep stirring until uniform to form a transparent and uniform solution; S03: Cool the transparent and uniform solution to 35-45°C, slowly add polyisobutylene amine while stirring, mix evenly, then add graphene oxide grafted with hyperbranched polyamide-amine, stir at high speed for 20-30 minutes to disperse it evenly, and obtain the adhesion improver.

7. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The base oil is a linear polyethylene fully synthetic base oil and a synthetic ester oil, with a mass ratio of 7-8:1; the synthetic ester oil is selected from pentaerythritol oleate; the antioxidant is selected from one or more of diphenylamine, p-diisooctyl diphenylamine or 2,6-tert-butyl-4-methylphenol; the preservative is selected from benzotriazoles.

8. The high water-resistant and high-adhesion drill thread grease according to any one of claims 1-7, characterized in that, A method for preparing a highly water-resistant and highly adhesive drill thread grease, specifically comprising: S001, heat the base oil to 40°C, then add the composite thickener, adhesion improver and water-resistant enhancer to the base oil and stir thoroughly. While stirring, raise the temperature to 100-110°C and react for 2 hours. Then cool down to 50-60°C and add the self-healing active microparticle anti-wear agent. Stir rapidly for 3 hours to obtain a homogeneous mixture. The speed of the rapid stirring is 2000-4000 rpm. S002, antioxidants and preservatives are added to the mixture in sequence, stirred evenly, and then ground 2 to 3 times by a grinding mill and homogenized once by a high-pressure homogenizer to obtain a high water-resistant and high-adhesion drill thread grease; the grinding mill is a three-roll mill.

9. The high water-resistant and high-adhesion drill thread grease according to claim 1, characterized in that, The aforementioned high water-resistant and high-adhesion drill thread grease is a self-healing drill thread grease suitable for harsh operating environments with high humidity and strong water intrusion, such as deep wells, ultra-deep wells, and offshore drilling.

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