Composite ultrahigh-temperature-resistant lubricant as well as preparation method and application thereof

Abstract

The invention discloses a composite ultrahigh-temperature-resistant lubricant which comprises dimethyl silicone oil, a phosphate-based extreme pressure anti-wear agent, a long-chain silicon-based polyether surfactant, an antioxidant and graphite powder in a mass ratio of (80-90): (3-5): (5-8): (2-3): (5-10). Wherein the long-chain silyl polyether surfactant is synthesized from polymethylhydrosiloxane, long-chain alpha-olefin and an allyl polyether monomer according to a mass ratio of (20-30): (2-5): (6-10). The invention also provides a method for preparing the composite ultrahigh-temperature-resistant lubricant. The composite ultrahigh-temperature-resistant lubricant provided by the invention has the temperature resistance of 220 DEG C, has the advantages of high stability, small corrosivity, strong dispersity and the like, and has a wide application prospect in high-temperature-resistant and high-salt-resistant water-based drilling fluids.

Description

Technical Field

[0001] The invention relates to a composite ultra-high temperature resistant lubricant and a preparation method and application thereof. Background Art

[0002] As global oil and gas development continues to expand into deep sea, ultra-deep and unconventional areas, the number of complex wells such as ultra-long horizontal wells and ultra-deep wells has gradually increased, and the difficulty of drilling has continued to increase. Complex conditions such as high friction torque in long horizontal sections and high temperatures in deep wells have put forward higher technical requirements for lubricants for drilling fluids. Most existing drilling fluid lubricants are difficult to take into account good lubricity, high temperature resistance and environmental protection performance at the same time, and cannot meet the drilling needs of special wells. The liquid lubricants commonly used in water-based drilling fluids mainly play a lubricating role by adsorbing on the surface of drill tools and well walls to form a dense lubricating film, but they are easy to desorb or degrade at high temperatures, and the lubrication effect is reduced. In addition, when encountering complex formations in deep wells, the drilling fluid is easily contaminated by salt invasion and calcium invasion, which affects the lubrication and other properties of the drilling fluid. The raw materials used to prepare lubricants are mostly mineral oil, vegetable oil, etc. Although conventional vegetable oil has environmental protection and low fluorescence properties, its temperature resistance is generally poor; although mineral oil has good temperature resistance, its fluorescence level is high and cannot meet environmental protection requirements, which limits its promotion and use.

[0003] At present, most lubricants are based on vegetable oil, white oil, synthetic ester, etc., such as LUBE, SMJH-1 and other extreme pressure lubricants. However, the high temperature resistance of such lubricants is not ideal, generally not exceeding 150°C, and the drilling fluid lubricant needs to be continuously replenished during the drilling process to maintain good drilling fluid lubrication performance. The lubricant consumption is large and the application cost is high. Therefore, it is urgent to develop a high-performance drilling fluid lubricant suitable for high friction torque and high temperature environment.

[0004] At present, a breakthrough has been made in the high temperature resistant lubricant for water-based drilling fluid. There are reports in the prior art on improving the temperature and salt resistance of lubricants. For example, Chinese patent ZL202311572108.3 discloses a high temperature resistant lubricant for water-based drilling fluid, which is prepared with vegetable oil, surfactant, polyol, high temperature resistant stabilizer, etc. as raw materials, and has the advantages of multiple hydroxyl adsorption points, strong temperature resistance, good lubricity, etc., but the temperature resistance is only 150°C, and the temperature resistance is insufficient; Chinese patent ZL202410536000.7 discloses a high temperature resistant and salt resistant hyperbranched lubricant for water-based drilling fluid, which is prepared with acrylamide monomers, anionic monomers, polar ester monomers and hyperbranched polysiloxane as raw materials, and the temperature resistance reaches 220°C, and has a good lubricating effect in 4% salt water slurry and saturated salt water slurry. There are disadvantages such as complex post-reaction treatment and complex preparation process. Existing liquid lubricants are mostly made of vegetable oil, mineral oil and other base oils, and are prepared by adding surfactants, anti-wear agents and other additives. Since vegetable oil has limited temperature resistance, mineral oil often has a high pour point and weak antioxidant capacity, it cannot adapt to ultra-high temperature environments. Therefore, in response to the technical needs of deep ultra-deep wells, ultra-long horizontal wells and other complex structure wells with large friction and insufficient temperature and salt resistance, it is urgent to develop a new type of lubricant that is resistant to high temperature and salt. Summary of the invention

[0005] In view of the problems of large friction, insufficient resistance to temperature and salt, and the inability to balance the temperature resistance and environmental protection performance of lubricant base oil in deep ultra-deep wells, ultra-long horizontal wells and other complex structure wells, the present invention uses dimethyl silicone oil as the base oil to develop a new type of long-chain silicon-based polyether surfactant, which has the characteristics of resistance to ultra-high temperature and excellent dispersion performance, and can form a good dispersion of dimethyl silicone oil in water. A composite ultra-high temperature resistant lubricant is synthesized using dimethyl silicone oil, extreme pressure anti-wear agent, surfactant, antioxidant, graphite powder and the like as raw materials, which overcomes the problems of insufficient resistance to high temperature and salt and complex preparation process of existing lubricants. The present invention provides a composite ultra-high temperature resistant lubricant for water-based drilling fluid and a preparation method thereof.

[0006] As one aspect of the present invention, it relates to a composite ultra-high temperature resistant lubricant, comprising dimethyl silicone oil, a phosphate-based extreme pressure anti-wear agent, a long-chain silicon-based polyether surfactant, an antioxidant and graphite powder in a mass ratio of (80-90): (3-5): (5-8): (2-3): (5-10), wherein the long-chain silicon-based polyether surfactant is synthesized from polymethyl hydrogen siloxane, a long-chain α-olefin and an allyl polyether monomer in a mass ratio of (20-30): (2-5): (6-10).

[0007] In a specific embodiment, the long-chain α-olefin is one of 1-decene, 1-dodecene, 1-tetradecene or any combination thereof;

[0008] In a specific embodiment, the allyl polyether monomer is one of allyl polyoxyethylene ether (APEG1200), methyl allyl polyoxyethylene ether (TPEG2400) or any combination thereof;

[0009] In a specific embodiment, the antioxidant is one of di-tert-butyl-p-cresol and tri-tert-butyl-p-cresol or any combination thereof;

[0010] In a specific embodiment, the phosphate-based extreme pressure anti-wear agent is one of diphenyl dithiophosphate (DPDP) and triphenyl phosphate (TPP) or any combination thereof;

[0011] As another aspect of the present invention, it relates to a method for preparing the above-mentioned composite ultrahigh temperature resistant lubricant, comprising:

[0012] (1) Synthesis of long-chain silicon-based polyether surfactants:

[0013] Adding polymethyl hydrogen siloxane, long-chain α-olefin and allyl polyether monomer in a mass ratio of (20-30): (2-5): (6-10) to a solvent, wherein the solvent is isopropanol, and mixing; adding a catalyst, wherein the catalyst is chloroplatinic acid; heating to 70-85° C. and maintaining for 6-8 hours; then removing the solvent by reduced pressure distillation to obtain a light yellow transparent liquid, which is a long-chain silicon-based polyether surfactant;

[0014] (2) Preparation of composite ultra-high temperature resistant lubricant:

[0015] Mix 80-90 parts by mass of dimethyl silicone oil with 5-8 parts by mass of the above-mentioned long-chain silicon-based polyether surfactant, raise the temperature to 40-45°C while stirring, add 3-5 parts by mass of phosphate-based extreme pressure anti-wear agent and 2-3 parts by mass of antioxidant, stir, add 5-10 parts by mass of graphite powder, stir, and cool to obtain a composite ultra-high temperature resistant lubricant.

[0016] In a specific embodiment, the long-chain α-olefin is one of 1-decene, 1-dodecene, 1-tetradecene or any combination thereof; the allyl polyether monomer is one of allyl polyoxyethylene ether (APEG1200) and methyl allyl polyoxyethylene ether (TPEG2400) or any combination thereof;

[0017] In a specific embodiment, the antioxidant is one of di-tert-butyl-p-cresol and tri-tert-butyl-p-cresol or any combination thereof; the phosphate-based extreme pressure anti-wear agent is one of diphenyl dithiophosphate (DPDP) and triphenyl phosphate (TPP) or any combination thereof.

[0018] As another aspect of the present invention, it relates to a water-based drilling fluid, comprising the above-mentioned composite ultra-high temperature resistant lubricant.

[0019] As another aspect of the present invention, it relates to the application of the above-mentioned water-based drilling fluid in oil and gas development.

[0020] The beneficial effects of the present invention include at least:

[0021] (1) The composite anti-ultrahigh temperature lubricant base oil provided by the present invention is dimethyl silicone oil. Due to the Si-O and SC bond chemistry of dimethyl silicone oil, it has high thermal stability and no fluorescence, meets environmental protection requirements, and avoids the shortcomings of using base oils such as vegetable oil, mineral oil, and synthetic ester. However, as a lubricant base oil, dimethyl silicone oil has poor dispersibility in water compared to vegetable oil and mineral oil, conventional surfactants have insufficient ultra-high temperature resistance, and dimethyl silicone oil cannot be effectively dispersed in aqueous solution. The long-chain silicon-based polyether surfactant prepared in the present invention has multiple ether bond groups, which can form multi-point adsorption with drill tools, and at the same time has long-chain alkyl groups, which can form a hydrophobic film on the surface of the drill tools to reduce the friction of the drill tools. The long-chain silicon-based polyether surfactant has the advantages of high thermal stability and strong dispersibility, and can evenly disperse dimethyl silicone oil in water to form a stable emulsion;

[0022] (2) The composite anti-ultrahigh temperature lubricant provided by the present invention has multiple functions such as extreme pressure, anti-wear, friction reduction and anti-oxidation, good thermal stability, low corrosiveness, and extreme pressure and anti-wear effects, which can achieve the purpose of reducing friction;

[0023] (3) The present invention provides a composite ultra-high temperature resistant lubricant with a temperature resistance of up to 220°C and a NaCl resistance of up to 15%. The salt water drilling fluid system has excellent lubrication properties after high temperature aging, and has broad application prospects in the field of high temperature resistant and high salt water-based drilling fluids. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0025] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents, materials and equipment described are all commercially available unless otherwise specified.

[0026] Unless otherwise specified, parts referred to in this application are parts by mass and percentages are percentages by mass.

[0027] Embodiment 1:

[0028] (1) Synthesis of long-chain silicon-based polyether surfactants

[0029] 20 g of polymethyl hydrogen siloxane (molecular weight 1700-3200), 2 g of 1-decene and 6 g of allyl polyoxyethylene ether (APEG1200) were added to 30 mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 80°C and maintained for 6 hours for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0030] (2) Preparation of composite ultra-high temperature resistant lubricant

[0031] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0032] Embodiment 2:

[0033] (1) Synthesis of long-chain silicon-based polyether surfactants

[0034] 20g of polymethylhydrogensiloxane (molecular weight 1700-3200), 2g of 1-decene, and 6g of allyl polyoxyethylene ether (APEG1200) were added to 30mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 80°C and maintained for 8h for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0035] (2) Preparation of composite ultra-high temperature resistant lubricant

[0036] Mix 90g of dimethyl silicone oil and 8g of long-chain silicon-based polyether surfactant, heat to 45°C while stirring, continue stirring at 500rpm for 30min, then add 5g of diphenyl dithiophosphate (DPDP) and 3g of di-tert-butyl-p-cresol, stir for 45min, finally add 10g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0037] Embodiment 3:

[0038] (1) Synthesis of long-chain silicon-based polyether surfactants

[0039] 20g of polymethylhydrogensiloxane (molecular weight 1700-3200), 2g of 1-dodecene and 6g of allyl polyoxyethylene ether (APEG1200) were added to 30mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 70°C and maintained for 6h for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0040] (2) Preparation of composite ultra-high temperature resistant lubricant

[0041] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0042] Embodiment 4:

[0043] (1) Synthesis of long-chain silicon-based polyether surfactants

[0044] 20g of polymethylhydrogensiloxane (molecular weight 1700-3200), 2g of 1-tetradecene and 6g of allyl polyoxyethylene ether (APEG1200) were added to 30mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 85°C and maintained for 6h for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0045] (2) Preparation of composite ultra-high temperature resistant lubricant

[0046] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0047] Embodiment 5:

[0048] (1) Synthesis of long-chain silicon-based polyether surfactants

[0049] 20g of polymethylhydrogensiloxane (molecular weight 1700-3200), 2g of 1-decene and 6g of methyl allyl polyoxyethylene ether (TPEG2400) were added to 30mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 80°C and maintained for 6h for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0050] (2) Preparation of composite ultra-high temperature resistant lubricant

[0051] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0052] Embodiment 6:

[0053] (1) Synthesis of long-chain silicon-based polyether surfactants

[0054] 30 g of polymethyl hydrogen siloxane (molecular weight 1700-3200), 5 g of 1-decene and 10 g of allyl polyoxyethylene ether (APEG1200) were added to 30 mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 80°C and maintained for 6 hours for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0055] (2) Preparation of composite ultra-high temperature resistant lubricant

[0056] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of triphenyl phosphate (TPP) and 2g of tri-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0057] Comparative Example 1:

[0058] Preparation of composite ultra-high temperature resistant lubricant:

[0059] Mix 80g of dimethyl silicone oil and 5g of sorbitan monooleate (Span 80), heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0060] Comparative Example 2:

[0061] (1) Synthesis of long-chain silicon-based polyether surfactants

[0062] 20 g of polymethyl hydrogen siloxane (molecular weight 1700-3200), 2 g of 1-decene and 6 g of allyl polyoxyethylene ether (APEG1200) were added to 30 mL of isopropanol (solvent), stirred evenly, and then chloroplatinic acid (catalyst) was added. The temperature was raised to 80°C and maintained for 6 hours for addition reaction. The solvent in the system was then removed by reduced pressure distillation to finally obtain a light yellow transparent liquid, which was a long-chain silicon-based polyether surfactant.

[0063] (2) Preparation of composite ultra-high temperature resistant lubricant

[0064] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 2g of di-tert-butyl-p-cresol, stir for 45min, finally add 5g of graphite powder, stir for 30min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0065] Comparative Example 3:

[0066] (1) Synthesis of long-chain silicon-based polyether surfactants

[0067] Add 20g of polymethylhydrogensiloxane (molecular weight 1700-3200), 2g of 1-decene and 6g of allyl polyoxyethylene ether (APEG1200) to 30mL of isopropanol (solvent), stir evenly, add chloroplatinic acid (catalyst), heat to 80°C and maintain for 6h for addition reaction, remove the solvent in the system by reduced pressure distillation, and finally obtain a light yellow transparent liquid, which is a long-chain silicon-based polyether surfactant.

[0068] (2) Preparation of composite ultra-high temperature resistant lubricant

[0069] Mix 80g of dimethyl silicone oil and 5g of the above-mentioned long-chain silicon-based polyether surfactant, heat to 40°C while stirring, continue stirring at 500rpm for 30min, then add 3g of diphenyl dithiophosphate (DPDP) and 2g of di-tert-butyl-p-cresol, stir for 45min, and cool to room temperature to obtain a composite ultra-high temperature resistant lubricant.

[0070] Application performance testing and results

[0071] The performance evaluation of composite anti-ultra-high temperature lubricants is mainly characterized by the following two aspects: one is to test the dispersibility of the lubricant in the brine slurry; the other is to test the lubricating performance of the brine slurry containing the lubricant after hot rolling at 220°C.

[0072] 1. Evaluation of the dispersibility of lubricants in salt water slurry

[0073] (1) Preparation of 4% bentonite-based slurry: Add 16 g bentonite and 0.56 g anhydrous sodium carbonate to 400 mL water, stir at 8000 r / min for 20 min, and seal and stand at room temperature for 24 h;

[0074] (2) Preparation of brine drilling fluid sample: Take 400 mL of the above 4% bentonite-based slurry, add 12 g (the mass of the lubricant added at this time is 3% of the mass of the above 4% bentonite-based slurry) of the lubricant prepared in the embodiment and the comparative example, and stir at a speed of 8000 r / min for 20 min; add 60 g (the mass of the sodium chloride added at this time is 15% of the mass of the above 4% bentonite-based slurry) of sodium chloride, and stir at a speed of 8000 r / min for 20 min;

[0075] (3) The salt water slurry containing the lubricant was left to stand at room temperature for 24 h, and the state of the salt water slurry solution was recorded. The results are shown in Table 1.

[0076] Table 1: Dispersibility of test samples in salt water slurry

[0077]

[0078]

[0079] From the test results in Table 1, it can be seen that the samples with the addition of long-chain silicon-based polyether surfactants did not show oil-water stratification phenomenon, and dimethyl silicone oil can be well dispersed in the salt water slurry. In Comparative Example 1, the surfactant selected was sorbitan monooleate (Span 80), which could not effectively disperse dimethyl silicone oil and showed stratification phenomenon. This shows that the synthesized long-chain silicon-based polyether surfactant has good dispersibility.

[0080] 2. Evaluation of lubricant lubrication performance in high temperature salt water slurry

[0081] (1) Preparation of 4% bentonite-based slurry: Add 16 g bentonite and 0.56 g anhydrous sodium carbonate to 400 mL water, stir at 8000 r / min for 20 min, and seal and stand at room temperature for 24 h;

[0082] (2) Preparation of brine drilling fluid sample: Take 400 mL of the above 4% bentonite-based slurry, add 12 g (the mass of the lubricant added at this time is 3% of the mass of the above 4% bentonite-based slurry) of the lubricant prepared in the embodiment and the comparative example, and stir at a speed of 8000 r / min for 20 min; add 60 g (the mass of the sodium chloride added at this time is 15% of the mass of the above 4% bentonite-based slurry) of sodium chloride, and stir at a speed of 8000 r / min for 20 min;

[0083] (3) Aging treatment of drilling fluid test samples: The above-mentioned brine drilling fluid samples were placed in an aging tank and placed in a roller heating furnace. The aging temperature was set to 220°C and the aging time was 16 hours.

[0084] (4) The apparent viscosity (AV), plastic viscosity (PV) and dynamic shear force (YP) of the prepared drilling fluid were tested in accordance with the national standard GB / T 29170-2012 Laboratory Test of Drilling Fluids in the Petroleum and Natural Gas Industry. The lubrication coefficient was measured using an extreme pressure lubrication instrument. The reduction rate of the drilling fluid lubrication coefficient was calculated according to formula (1). The specific evaluation data are shown in Table 1.

[0085] Ri=(K0-K1) / K0×100% (1)

[0086] Where, Ri is the lubrication coefficient reduction rate of the drilling fluid sample, %;

[0087] K0 is the lubrication coefficient of the base slurry;

[0088] K1 is the lubricity coefficient of the drilling fluid sample.

[0089] Table 2: Rheological and lubrication properties of the test samples at 220°C

[0090]

[0091] From the test results in Table 2, it can be seen that when the composite anti-ultrahigh temperature lubricant for drilling fluid prepared in Examples 1 to 6 is added in an amount of 3wt%, after curing at 220℃ for 16h in a salt water slurry with 4wt% bentonite, the rheological properties of the drilling fluid base slurry are less affected. The lubrication coefficient reduction rate of the test sample prepared in the embodiment after aging is ≥80%, and it has a good high-temperature lubrication effect. As the carbon chain length of the long-chain silicon-based polyether surfactant increases, the surfactant can be adsorbed on the surface of the drill bit to form a denser hydrophobic layer, and the lubrication effect is better. In Comparative Example 1, sorbitan monooleate (Span 80) is used, and the ester group in the molecular structure is easily hydrated and decomposed at high temperature, and dimethyl silane cannot be effectively dispersed in the aqueous phase, and the lubrication effect is significantly lower than that of the embodiment in which a long-chain silicon-based polyether surfactant is added. In Comparative Example 2, no phosphate-based extreme pressure anti-wear agent is added, and an inorganic iron phosphate reaction film cannot be formed under extreme pressure conditions, and the anti-wear and drag reduction ability is significantly reduced. In comparative example 3, no graphite powder was added, and the reduction rate of lubrication coefficient was significantly lower than that of examples 1 to 6, indicating that solid graphite powder and liquid extreme pressure anti-wear agent, surfactant, dimethyl silicone oil and other components have synergistic effect, and the friction resistance is significantly reduced by rolling friction. From the performance evaluation of the examples, it can be seen that the synthesized composite anti-ultrahigh temperature lubricant can resist temperatures up to 220°C and 15% NaCl.

[0092] Examples 1-6 can be summarized as follows:

[0093] (1) Synthesis of long-chain silicon-based polyether surfactants:

[0094] Add polymethyl hydrogen siloxane, long-chain α-olefin and allyl polyether monomer in a mass ratio of (20-30): (2-5): (6-10) to isopropanol (solvent) and mix; add chloroplatinic acid (catalyst), raise the temperature to 70-85°C and keep for 6-8h; remove the solvent to finally obtain a light yellow transparent liquid, which is a long-chain silicon-based polyether surfactant;

[0095] (2) Preparation of composite ultra-high temperature resistant lubricant:

[0096] Mix 80-90 parts by mass of dimethyl silicone oil with 5-8 parts by mass of the above-mentioned long-chain silicon-based polyether surfactant, raise the temperature to 40-45°C while stirring, add 3-5 parts by mass of phosphate-based extreme pressure anti-wear agent and 2-3 parts by mass of antioxidant, stir, add 5-10 parts by mass of graphite powder, stir, and cool to obtain a composite ultra-high temperature resistant lubricant.

[0097] Wherein, the long-chain α-olefin is one of 1-decene, 1-dodecene, 1-tetradecene or any combination thereof;

[0098] The allyl polyether monomer is one of allyl polyoxyethylene ether (APEG1200), methyl allyl polyoxyethylene ether (TPEG2400) or any combination thereof;

[0099] Wherein, the phosphate-based extreme pressure anti-wear agent is one of diphenyl dithiophosphate (DPDP) and triphenyl phosphate (TPP) or any combination thereof;

[0100] The antioxidant is one of di-tert-butyl-p-cresol and tri-tert-butyl-p-cresol or any combination thereof.

Claims

1. Composite ultra-high temperature resistant lubricant, characterized in that: The invention comprises dimethyl silicone oil, a phosphate-based extreme pressure anti-wear agent, a long-chain silicon-based polyether surfactant, an antioxidant and graphite powder in a mass ratio of (80-90):(3-5):(5-8):(2-3):(5-10), wherein the long-chain silicon-based polyether surfactant is synthesized from polymethyl hydrogen siloxane, a long-chain α-olefin and an allyl polyether monomer in a mass ratio of (20-30):(2-5):(6-10).

2. The composite ultra-high temperature resistant lubricant according to claim 1, characterized in that: The long-chain α-olefin is one of 1-decene, 1-dodecene, 1-tetradecene or any combination thereof.

3. The composite ultra-high temperature resistant lubricant according to claim 1, characterized in that: The allyl polyether monomer is one of allyl polyoxyethylene ether and methyl allyl polyoxyethylene ether or any combination thereof.

4. The composite ultra-high temperature resistant lubricant according to claim 1, characterized in that: The antioxidant is one of di-tert-butyl-p-cresol and tri-tert-butyl-p-cresol or any combination thereof.

5. The composite ultra-high temperature resistant lubricant according to claim 1, characterized in that: The phosphate-based extreme pressure anti-wear agent is one of diphenyl dithiophosphate and triphenyl phosphate or any combination thereof.

6. A method for preparing a composite ultra-high temperature resistant lubricant, characterized in that: include: (1) Synthesis of long-chain silicon-based polyether surfactants: Add polymethyl hydrogen siloxane, long-chain α-olefin and allyl polyether monomer in a mass ratio of (20-30): (2-5): (6-10) to a solvent, wherein the solvent is isopropanol, and mix; add a catalyst, wherein the catalyst is chloroplatinic acid; raise the temperature to 70-85° C. and maintain for 6-8 hours; then remove the solvent by reduced pressure distillation to obtain a light yellow transparent liquid, which is a long-chain silicon-based polyether surfactant; (2) Preparation of composite ultra-high temperature resistant lubricant: Mix 80-90 parts by mass of dimethyl silicone oil with 5-8 parts by mass of the above-mentioned long-chain silicon-based polyether surfactant, raise the temperature to 40-45°C while stirring, add 3-5 parts by mass of phosphate-based extreme pressure anti-wear agent and 2-3 parts by mass of antioxidant, stir, add 5-10 parts by mass of graphite powder, stir, and cool to obtain a composite ultra-high temperature resistant lubricant.

7. The method according to claim 6, characterized in that The long-chain α-olefin is one of 1-decene, 1-dodecene, 1-tetradecene or any combination thereof; the allyl polyether monomer is one of allyl polyoxyethylene ether and methyl allyl polyoxyethylene ether or any combination thereof.

8. The method of claim 6, characterized in that The antioxidant is one of di-tert-butyl-p-cresol and tri-tert-butyl-p-cresol or any combination thereof; the phosphate-based extreme pressure anti-wear agent is one of diphenyl dithiophosphate and triphenyl phosphate or any combination thereof.

9. A water-based drilling fluid, characterized in that: It comprises the composite anti-ultrahigh temperature lubricant according to any one of claims 1-5 or the composite anti-ultrahigh temperature lubricant prepared by the method according to any one of claims 6-8.

10. Use of the water-based drilling fluid according to claim 9 in oil and gas development.

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