Oil and gas field drilling fluid efficient lubricant and preparation method thereof

Abstract

The invention relates to the technical field of petroleum drilling engineering chemical agents, and discloses an efficient lubricant for oil and gas field drilling fluid and a preparation method of the efficient lubricant. The efficient lubricant for the drilling fluid of the oil and gas field comprises the following components: 40-60% of a plant oil base, 15-25% of synthetic ester, 5-10% of modified nano SiO2, 8-12% of a nano ZnO / Al2O3 compound, 3-5% of sulfurized fatty acid ester, 2-4% of an organic molybdenum compound, 3-5% of a dispersing agent and 0.1-0.5% of an antioxidant. The percentages are weight percentages, and the contents are adjusted according to actual application requirements, so that the oil and gas field drilling fluid efficient lubricant with the total weight percentage being 100% is formed. The efficient drilling fluid lubricant with the nanocomposite as the core is prepared through nanoparticle surface modification and a multi-element synergistic lubrication mechanism, is suitable for complex well conditions such as deep wells and horizontal wells, and has the characteristics of excellent wear resistance, resistance reduction, high-temperature stability and environmental protection. The problems that a traditional lubricant loses efficacy at high temperature and is poor in dispersity are solved, and the lubricant has the advantages of efficient lubrication, environmental protection and economical efficiency and is suitable for drilling of complex wells such as shale gas.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical agents for oil drilling engineering, and particularly relates to a high-efficiency lubricant for oil and gas field drilling fluid and a preparation method thereof. Background Art

[0002] With the continuous deepening of oil and gas field exploration and development at home and abroad, the number of deep wells and ultra-deep wells for drilling is increasing continuously. Deep wells and ultra-deep wells not only have deep oil layers and complex drilled formations, but also have high downhole temperatures and pressures, long operation cycles, and are prone to complex situations such as blowouts, well collapses, and well leaks. In order to ensure safe and smooth drilling and exploitation, deep wells and ultra-deep wells generally use mud with high density and high solid content, and such high-density mud will have a negative impact on the regulation and maintenance of the rheology of drilling fluid, greatly increasing the rheological resistance of drilling fluid and resulting in a substantial increase in the rotational resistance and hoisting and lowering resistance of the drill string.

[0003] Since the main controllable factor affecting the torque and resistance of the drill string and the wear of drilling tools during the drilling process is the lubricating performance of the drilling fluid, the lubricating performance of the drilling fluid plays a crucial role in reducing downhole complex situations such as sticking and ensuring safe and rapid drilling. A drilling fluid with good lubricating performance can reduce the torque, wear and fatigue of the drill string, extend the service life of the drill bit bearing, prevent adhesive sticking, reduce bit balling, and is easy to handle downhole accidents.

[0004] However, traditional drilling fluid lubricants have the following technical bottlenecks:

[0005] 1. Poor lubricating durability: Conventional liquid lubricants (such as mineral oil and fatty acid esters) are easily decomposed under high temperature and high pressure, and the strength of the adsorption film is low.

[0006] 2. Fluorescence interference and environmental protection problems: Mineral oil-based lubricants have a high fluorescence level, which affects geological logging and has poor biodegradability.

[0007] 3. Insufficient dispersion of nanomaterials: Existing nano-lubricants have unstable performance due to particle agglomeration and it is difficult to achieve long-term lubrication.

[0008] In recent years, nanomaterials have been introduced into the lubricant field due to their small size effect and surface activity, such as nano-SiO2, metal oxides, etc., but their modification process is complex and the compatibility with the drilling fluid system still needs to be improved. Summary of the Invention

[0009] The present invention provides a high-efficiency lubricant for oil and gas field drilling fluid and a preparation method thereof. Through surface modification of nanoparticles and a multi-component synergistic lubrication mechanism, a high-efficiency drilling fluid lubricant with a nanocomposite material as the core is prepared, which is suitable for complex well conditions such as deep wells and horizontal wells, and has excellent anti-wear and friction reduction, high-temperature stability and environmental protection characteristics. It solves the problems of high-temperature failure and poor dispersibility of traditional lubricants, and has the advantages of high-efficiency lubrication, environmental protection and economy, and is suitable for drilling of complex wells such as shale gas.

[0010] The present invention provides a high-efficiency lubricant for oil and gas field drilling fluid, comprising the following components:

[0011]

[0012] The above percentages are weight percentages, and the above contents are adjusted according to actual application requirements to form a high-efficiency lubricant for oil and gas field drilling fluid with a total weight percentage of 100%.

[0013] Further, the vegetable oil base is castor oil or soybean oil to provide basic lubricity, and the biodegradation rate > 80%;

[0014] The synthetic ester is trimethylolpropane oleate, and the synthetic ester combines with the vegetable oil base to make the anti-temperature ≥ 200 °C.

[0015] Further, the modified nano-SiO2, as a composite nano-metal oxide, is grafted on its surface with a silane coupling agent KH570, and the particle size is 20 - 50 nm.

[0016] Further, the particle size of the nano-ZnO / Al2O3 composite is 30 - 80 nm, and the torque is reduced by ≥ 40% through the synergistic action of physical rolling and chemical adsorption.

[0017] Further, the sulfurized fatty acid ester contains a sulfur extreme pressure agent, and an FeS lubricating film is formed at a set high temperature;

[0018] The organic molybdenum compound forms a MoS2 layer, and the sulfurized fatty acid ester and the organic molybdenum compound are used as extreme pressure and anti-wear additives to form a high-strength chemical adsorption film.

[0019] The present invention also provides a preparation method of a high-efficiency lubricant for oil and gas field drilling fluid. Based on the high-efficiency lubricant for oil and gas field drilling fluid described in any one of claims 1 - 5, the preparation method specifically includes:

[0020] S1. Heat the vegetable oil base and the synthetic ester to 50 °C, and sequentially add the sulfurized fatty acid ester and the organic molybdenum compound, and stir and mix;

[0021] S2. Add the modified nano-SiO2 and the nano-ZnO / Al2O3 composite, and disperse for 30 min at a rotation speed of 500 rpm;

[0022] S3. Add dispersant Tween80 and antioxidant BHT, perform ultrasonic treatment at 60°C for 1 h, and obtain a high-efficiency lubricant for oil and gas field drilling fluids after filtration.

[0023] Further, the specific steps of step S1 include:

[0024] S101. Determine the weight percentages of each component and accurately weigh each component. Add the vegetable oil-based and synthetic esters into the reaction kettle, set the heating temperature at 50°C, and stir at a speed of 100 - 200 rpm to uniformly heat the vegetable oil-based and synthetic esters.

[0025] S102. When the temperature of the reaction kettle reaches 50°C and stabilizes, slowly add sulfurized fatty acid ester and stir for 5 - 10 min to fully disperse the sulfurized fatty acid ester in the mixed system of the vegetable oil-based and synthetic esters.

[0026] S103. After the sulfurized fatty acid ester is completely dispersed, slowly add the organomolybdenum compound. After the addition is completed, increase the speed to 300 - 400 rpm and continue stirring for 30 - 60 min to ensure that all raw materials are fully and uniformly mixed.

[0027] Further, the specific steps of step S2 include:

[0028] Slowly add the modified nano-SiO2 and nano-ZnO / Al2O3 composite into the reaction kettle, stir while adding, insert the stirring head of the high-speed disperser into the reaction kettle, turn on the high-speed disperser and adjust the speed to 500 rpm, and set the dispersion time at 30 min to ensure that the nano materials are uniformly dispersed in the system.

[0029] Further, in step S2, the preparation method of the modified nano-SiO2 is:

[0030] Vacuum-dry nano-SiO2 at 120°C for 24 h, disperse it in absolute ethanol, add silane coupling agent KH570, perform ultrasonic treatment for 1 h, react at 80°C for 6 h, and obtain the modified nano-SiO2 by centrifugation and drying; among them, when adding the silane coupling agent KH570, the mass ratio is 1:0.3.

[0031] Further, in step S2, the preparation method of the nano-ZnO / Al2O3 composite is:

[0032] Mix ZnO and Al2O3 nanoparticles with polyethylene glycol PEG600, perform ball milling for 4 h to form a uniform composite, namely the nano-ZnO / Al2O3 composite; among them, the ratio of ZnO to Al2O3 nanoparticles is 1:1.

[0033] The beneficial effects of the present invention are as follows:

[0034] The high-efficiency lubricant for oil and gas field drilling fluid prepared by the present invention comprises modified nano-SiO2 (5-10%), nano-ZnO / Al2O3 composite (8-12%), vegetable oil base (40-60%), sulfurized fatty acid ester (3-5%) and organic molybdenum compound (2-4%), and also comprises a dispersant (3-5%) and an antioxidant (0.1-0.5%). The achieved functional effects are as follows:

[0035] 1. Lubrication performance: The reduction rate of friction coefficient is ≥90% (ASTM D4172), the extreme pressure film strength is >5000N, and it is suitable for a density ≥2.5g / cm 3 ; The temperature resistance is ≥200°C, it is resistant to salt up to saturated brine, and resistant to calcium and magnesium pollution (≤8000mg / L).

[0036] 2. Environmental protection: There is no fluorescence interference (fluorescence level ≤2), and the biodegradation rate is >85% (OECD 301B standard).

[0037] 3. Economy: The dosage only needs to be 0.5-1.5% (the traditional lubricant needs 2-3%), and the cost is reduced by about 30%. Brief Description of the Drawings

[0038] Figure 1 It is a schematic flow chart of the preparation method of the high-efficiency lubricant for oil and gas field drilling fluid of the present invention.

[0039] The realization of the purpose, functional characteristics and advantages of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0042] In addition, the descriptions involving "first", "second", etc. in the present invention are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0043] It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not used to limit the present invention.

[0044] The present invention provides a high-efficiency drilling fluid lubricant with a nanocomposite material as the core and its preparation method, which is applicable to complex well conditions such as deep wells and horizontal wells, and has excellent anti-wear and friction reduction, high-temperature stability, and environmental protection characteristics. Among them, a high-efficiency lubricant for oil and gas field drilling fluid provided by the present invention includes the following components:

[0045]

[0046] The above percentages are weight percentages, and the above contents are adjusted according to actual application requirements to form a high-efficiency lubricant for oil and gas field drilling fluid with a total weight percentage of 100%.

[0047] Specifically:

[0048] (1) Environmentally friendly base oil phase

[0049] Using castor oil or soybean oil as the base fluid and combining with synthetic esters (such as trimethylolpropane oleate) to improve high-temperature stability, specifically including:

[0050] Vegetable oil base: Using castor oil or soybean oil, which is an environmentally friendly base fluid, provides basic lubricity, and the biodegradation rate > 80%.

[0051] Synthetic ester: Trimethylolpropane oleate, improves high-temperature stability (temperature resistance ≥ 200 °C) and reduces viscosity sensitivity.

[0052] (2) Modified nano-SiO2

[0053] The surface of nano-SiO2 is grafted with a silane coupling agent (KH570), with a particle size of 20 - 50 nm, enhancing its dispersibility and adsorption ability on the friction surface.

[0054] (3) Composite nano-metal oxide

[0055] Zinc oxide (ZnO) and aluminum oxide (Al2O3) nanoparticles are introduced to form a nano-ZnO / Al2O3 composite with a particle size of 30 - 80 nm, which synergistically reduces the friction coefficient through physical rolling and chemical adsorption, and reduces the torque by ≥40%.

[0056] (4) Extreme pressure and anti-wear additive

[0057] Sulfurized fatty acid esters and organic molybdenum compounds are used to form a high-strength chemical adsorption film to enhance the extreme pressure lubrication performance, specifically including:

[0058] Sulfurized fatty acid esters: Sulfur-containing extreme pressure agents that generate FeS lubricating films at a set high temperature.

[0059] Organic molybdenum compounds: Form MoS2 layers to enhance anti-wear properties.

[0060] (5) Dispersant (Tween80): A non-ionic surfactant that prevents nanoparticle aggregation.

[0061] (6) Antioxidant (BHT): Delays oxidation and extends the storage period.

[0062] As Figure 1 shown, the present invention also provides a preparation method for an efficient lubricant for oil and gas field drilling fluids. Based on the above-mentioned efficient lubricant for oil and gas field drilling fluids, the preparation method specifically includes:

[0063] S1. Heat the vegetable oil-based and synthetic esters to 50 °C, and sequentially add sulfurized fatty acid esters and organic molybdenum compounds, and stir and mix.

[0064] The step S1 specifically includes:

[0065] S101. Raw material preparation and heating operation

[0066] Raw material preparation: Determine the weight percentages of each component as follows: castor oil 50%, trimethylolpropane oleate 20%, modified nano-SiO2 8%, ZnO / Al2O3 composite 10%, sulfurized fatty acid esters 4%, organic molybdenum compounds 3%, dispersant Tween80 4%, antioxidant BHT 0.2%. Use a high-precision electronic balance to accurately weigh each component to ensure the accurate dosage of each raw material. Conduct a purity inspection on the raw materials to ensure they meet the production requirements. If the raw materials contain impurities or do not meet the purity standards, pretreatment or replacement with qualified raw materials is required.

[0067] Heating operation: Add the accurately weighed vegetable oil base and synthetic ester into the cleaned reaction kettle. Turn on the heating device of the reaction kettle and set the heating temperature to 50°C. During the heating process, use a thermometer to monitor the temperature inside the reaction kettle in real time to ensure that the temperature steadily rises to 50°C. At the same time, turn on the stirring device of the reaction kettle and stir at a relatively low speed (such as 100 - 200 rpm) to make the vegetable oil base and synthetic ester evenly heated.

[0068] S102. Addition of sulfurized fatty acid

[0069] When the temperature inside the reaction kettle reaches 50°C and stabilizes, when starting to add sulfurized fatty acid ester, it should be added slowly to avoid excessive local concentration caused by adding too much at one time. After adding a certain amount of sulfurized fatty acid ester, stir for a period of time (such as 5 - 10 min) to make the sulfurized fatty acid ester fully dispersed in the mixed system of the vegetable oil base and synthetic ester.

[0070] S103. Addition of organic molybdenum compound

[0071] After the sulfurized fatty acid ester is completely dispersed, add the organic molybdenum compound in the same way. After the addition is completed, increase the rotation speed of the stirring device to 300 - 400 rpm and continue stirring for 30 - 60 min to ensure that all raw materials are fully mixed and uniform.

[0072] S2. Add modified nano - SiO2 and nano - ZnO / Al2O3 composite, and disperse at a rotation speed of 500 rpm for 30 min.

[0073] The specific steps of step S2 include:

[0074] (1) Addition of nanomaterials

[0075] Slowly add the modified nano - SiO2 and nano - ZnO / Al2O3 composite into the reaction kettle. During the addition process, stir while adding to prevent agglomeration of nanomaterials. After the addition is completed, insert the stirring head of the high - speed disperser into the reaction kettle to ensure that the stirring head is completely immersed in the mixed system.

[0076] (2) Dispersion operation

[0077] Turn on the high - speed disperser, adjust the rotation speed to 500 rpm, and start the dispersion operation. The dispersion time is set to 30 min. During the dispersion process, closely observe the state of the mixed system to ensure that the nanomaterials are evenly dispersed in the system. It is possible to regularly sample and use a microscope to observe the dispersion of the nanomaterials.

[0078] Among them, the preparation method of the modified nano - SiO2 and nano - ZnO / Al2O3 composite specifically includes:

[0079] 1> The preparation method of modified nano-SiO2 is as follows:

[0080] Disperse nano-SiO2 in vacuum at 120 °C for 24 h, then disperse it in absolute ethanol, add KH570 silane coupling agent (mass ratio 1:0.3), perform ultrasonic treatment for 1 h, react at 80 °C for 6 h, and obtain modified nano-SiO2 by centrifugation and drying.

[0081] 2> The preparation method of nano-ZnO / Al2O3 composite is as follows:

[0082] Mix ZnO and Al2O3 nanoparticles (ratio 1:1) with polyethylene glycol (PEG600), and ball mill for 4 h to form a uniform composite, namely nano-ZnO / Al2O3 composite.

[0083] S3. Add dispersant Tween 80 and antioxidant BHT, perform ultrasonic treatment (power 200 W) at 60 °C for 1 h, and obtain a high-efficiency lubricant for oil and gas field drilling fluid after filtration.

[0084] (1) Additives addition

[0085] After the dispersion operation is completed, add dispersant Tween 80 and antioxidant BHT to the reaction kettle. When adding, it should be added slowly and continue to stir to make the additives evenly dispersed in the mixing system.

[0086] (2) Ultrasonic treatment

[0087] Transfer the reaction kettle to an ultrasonic processor, set the ultrasonic treatment temperature to 60 °C, and the ultrasonic treatment time to 1 h. During the ultrasonic treatment process, use a thermometer to monitor the temperature in the reaction kettle in real time to ensure that the temperature is stable at 60 °C. Ultrasonic treatment can further promote the uniform mixing and dispersion of each raw material, and improve the stability and performance of the product.

[0088] (3) Filtration operation

[0089] After the ultrasonic treatment is completed, filter the mixing system in the reaction kettle through a filtration device. During the filtration process, the filtration speed should be controlled to avoid incomplete filtration or filter paper blockage caused by being too fast. After filtration is completed, collect the filtrate, which is the prepared high-efficiency lubricant for oil and gas field drilling fluid.

[0090] Performance tests were carried out on the present invention: Add 1% to the drilling fluid with a density of 2.3 g / cm 3 , the friction coefficient is reduced from 0.28 to 0.05, the drill string torque drops by 45%, and the temperature resistance reaches 220 °C.

[0091] The high-efficiency lubricant for oil and gas field drilling fluid prepared by the present invention comprises modified nano-SiO2 (5-10%), nano-ZnO / Al2O3 composite (8-12%), vegetable oil base (40-60%), sulfurized fatty acid ester (3-5%) and organic molybdenum compound (2-4%), and dispersant (3-5%) and antioxidant (0.1-0.5%) are added. The functional effects achieved are as follows:

[0092] 1. Lubrication performance: The reduction rate of friction coefficient ≥ 90% (ASTM D4172), extreme pressure film strength > 5000N, adapted density ≥ 2.5g / cm 3 ; Temperature resistance ≥ 200°C, salt resistance to saturated brine, resistance to calcium and magnesium pollution (≤ 8000mg / L).

[0093] 2. Environmental protection: No fluorescence interference (fluorescence level ≤ 2), biodegradation rate > 85% (OECD 301B standard).

[0094] 3. Economy: The dosage only needs to be 0.5-1.5% (the traditional lubricant needs 2-3%), and the cost is reduced by about 30%.

[0095] The present invention solves the problems of high-temperature failure and poor dispersibility of traditional lubricants through the surface modification technology of nanoparticles and the multi-component synergistic lubrication mechanism, and has the advantages of high-efficiency lubrication, environmental protection and economy, and is applicable to the drilling of complex wells such as shale gas.

[0096] It should be noted that in this text, the term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, device, article or method comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, device, article or method. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of another identical element in the process, device, article or method comprising that element.

[0097] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. An efficient lubricant for oil and gas field drilling fluid, characterized in that, It includes the following components: The above percentages are weight percentages, and the above contents are adjusted according to actual application requirements to form an efficient lubricant for oil and gas field drilling fluids with a total weight percentage of 100%.

2. The high-efficiency lubricant for oil and gas field drilling fluid according to claim 1, wherein The vegetable oil base is castor oil or soybean oil to provide basic lubricity, and the biodegradation rate > 80%; The synthetic ester is trimethylolpropane oleate, and the synthetic ester combines with the vegetable oil base to make the anti-temperature ≥ 200 °C.

3. The high-efficiency lubricant for oil and gas field drilling fluid according to claim 1, characterized in that, The modified nano-SiO2 is used as a composite nano-metal oxide, and its surface is grafted with silane coupling agent KH570, with a particle size of 20 - 50 nm.

4. The high-efficiency lubricant for oil and gas field drilling fluid according to claim 1, wherein The particle size of the nano-ZnO / Al2O3 composite is 30 - 80 nm, and it reduces the torque by ≥ 40% through the synergistic effect of physical rolling and chemical adsorption.

5. The high-efficiency lubricant for oil and gas field drilling fluid according to claim 1, characterized in that, The sulfurized fatty acid ester contains a sulfur extreme pressure agent and generates an FeS lubricating film at a set high temperature; The organic molybdenum compound forms a MoS2 layer, and the sulfurized fatty acid ester and the organic molybdenum compound are used as extreme pressure and anti-wear additives to form a high-strength chemical adsorption film.

6. A preparation method of an efficient lubricant for oil and gas field drilling fluid, characterized in that, Based on the efficient lubricant for oil and gas field drilling fluids according to any one of claims 1 - 5, the preparation method specifically includes: S1. Heat the vegetable oil base and the synthetic ester to 50 °C, and sequentially add the sulfurized fatty acid ester and the organic molybdenum compound, and stir and mix them; S2. Add the modified nano-SiO2 and the nano-ZnO / Al2O3 composite, and disperse them at a rotation speed of 500 rpm for 30 min; S3. Add the dispersant Tween 80 and the antioxidant BHT, perform ultrasonic treatment at 60 °C for 1 h, and filter to obtain the efficient lubricant for oil and gas field drilling fluids.

7. The preparation method of the high-efficiency lubricant for oil and gas field drilling fluid according to claim 6, characterized in that, The step S1 specifically includes: S101. Determine the weight percentages of each component and accurately weigh each component. Add the vegetable oil base and the synthetic ester to the reaction kettle, set the heating temperature to 50 °C, and stir at a rotation speed of 100 - 200 rpm to make the vegetable oil base and the synthetic ester evenly heated; S102. When the temperature of the reaction kettle reaches 50 °C and stabilizes, slowly add the sulfurized fatty acid ester and stir for 5 - 10 min to make the sulfurized fatty acid ester fully dispersed in the mixed system of the vegetable oil base and the synthetic ester; S103. After the sulfurized fatty acid ester is completely dispersed, slowly add the organic molybdenum compound. After the addition is completed, increase the rotation speed to 300 - 400 rpm and continue to stir for 30 - 60 min to ensure that all raw materials are fully mixed and uniform.

8. The method for preparing a high-efficiency lubricant for oil and gas field drilling fluid according to claim 7, characterized in that: The step S2 specifically includes: Slowly add the modified nano-SiO2 and the nano-ZnO / Al2O3 composite to the reaction kettle, stir while adding, insert the stirring head of the high-speed disperser into the reaction kettle, turn on the high-speed disperser and adjust the rotation speed to 500 rpm, and set the dispersion time to 30 min to ensure that the nano materials are evenly dispersed in the system.

9. The preparation method of the high-efficiency lubricant for oil and gas field drilling fluid according to claim 8, wherein In the step S2, the preparation method of the modified nano-SiO2 is: The nano-SiO2 was vacuum dried at 120 °C for 24 h, dispersed in absolute ethanol, silane coupling agent KH570 was added, ultrasonic treatment was carried out for 1 h, reacted at 80 °C for 6 h, and centrifuged and dried to obtain modified nano-SiO2; wherein, when adding the silane coupling agent KH570, the mass ratio was 1:0.

3.

10. The preparation method of the high-efficiency lubricant for oil and gas field drilling fluid according to claim 8, characterized in that, In the step S2, the preparation method of the nano-ZnO / Al2O3 composite is as follows: ZnO and Al2O3 nanoparticles were mixed with polyethylene glycol PEG600 and ball milled for 4 h to form a uniform composite, namely nano-ZnO / Al2O3 composite; wherein, the ratio of ZnO to Al2O3 nanoparticles was 1:1.

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