A water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters, its preparation method and application

Abstract

This invention provides a water-based drilling fluid for lubrication and drag reduction in deep-sea oil and gas wells (10,000 meters deep), its preparation method, and its application, belonging to the field of drilling fluid technology. This water-based drilling fluid for lubrication and drag reduction in deep-sea oil and gas wells (10,000 meters deep) comprises the following raw materials in parts by weight: 100 parts water, 5-10 parts light diesel oil, 1-4 parts high-temperature resistant clay, 3-6 parts dendritic macromolecular filtration reducer, 2-4 parts temperature-responsive micelle shearing agent, 2-4 parts high-temperature resistant strong adsorption plugging agent, 3-5 parts nanocomposite polymer brush lubricant, and 1-3 parts high-temperature resistant system stabilizer. In this invention, the filtration reducer, shearing agent, plugging agent, and lubricant work synergistically to enable the drilling fluid to maintain low viscosity, good lubrication performance, and settling stability under conditions of 240℃, saturated salt, and high density. This can increase mechanical drilling speed, reduce drill bit wear, reduce drilling accidents such as differential pressure stuck pipe, and lower drilling time and overall cost in deep-sea oil and gas wells (10,000 meters deep).

Description

Technical Field

[0001] This invention relates to a water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters, its preparation method and application, belonging to the field of drilling fluid technology. Background Technology

[0002] Ultra-deep geological conditions are complex, generally characterized by ultra-high temperatures (>220℃), ultra-high salinity (>15%), and ultra-high pressure (>140MPa). The complex formation fluids, lithology, and pressure systems easily lead to downhole accidents such as wellbore collapse, stuck pipe, overflows, and leakage, posing significant challenges to safe and efficient drilling. Drilling fluid, the working fluid required for drilling operations, is often referred to as the "blood" of drilling. It functions to stabilize the wellbore, carry cuttings, balance formation pressure, and transmit water power, making it an indispensable core engineering technology for oil and gas exploration and development. However, existing drilling fluids in ultra-deep, high-temperature, high-salt, and high-pressure environments generally suffer from poor stability and difficulty in performance control. Furthermore, to balance formation pressure, deep-layer, high-temperature, high-salt-water-based drilling fluids typically have high density. Ultra-high-density drilling fluids, due to their high solid content, suffer from excessive viscosity, increased filtration loss, and poor lubrication, making drilling operations difficult and failing to meet the needs of oil and gas drilling at depths of tens of thousands of meters.

[0003] Existing research on drilling fluids for ultra-deep and even 10,000-meter deep formations largely focuses on the temperature and salt resistance of the drilling fluids. For example, Chinese patent documents CN117736707A and CN115466603A disclose a 230℃-resistant, high-salt, high-density water-based drilling fluid and its preparation method and application, and a 240℃-resistant, salt-resistant, plugging-type water-based drilling fluid and its preparation method and application, respectively. These drilling fluids exhibit good rheological and filtration properties under 230℃ and higher temperatures and high-salt conditions. However, in practical applications, due to the need to balance formation pressure, the drilling fluid needs to be increased to a higher density. Excessively high drilling fluid viscosity can lead to slower drilling speeds, increased friction, drilling fluid sedimentation and stratification, and frequent sticking, severely increasing the drilling costs and risks of 10,000-meter deep oil and gas wells.

[0004] Therefore, there is an urgent need to develop a water-based drilling fluid that can maintain low viscosity, good lubrication performance, and sedimentation stability under conditions of 240℃, saturated salt, and high density. This fluid would increase mechanical drilling speed, reduce drill bit wear, and decrease drilling accidents such as differential pressure stuck pipe. To this end, this invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, particularly the problems of excessive viscosity, difficulty in controlling rheological properties, excessive friction, severe drill bit wear and high costs, easy settling, and unstable drilling fluid density under high-density conditions in deep formation water-based drilling fluids, this invention provides a water-based drilling fluid for lubrication and drag reduction in deep-ground oil and gas wells at depths of 10,000 meters, along with its preparation method and applications. This invention constructs a water-based drilling fluid for lubrication and drag reduction in deep-ground oil and gas wells at 10,000 meters, using high-temperature resistant clay, dendritic macromolecular filtration reducers, temperature-responsive micelle shearing agents, high-temperature resistant strong adsorption plugging agents, nanocomposite polymer brush lubricants, and high-temperature system stabilizers as core components. This drilling fluid exhibits low viscosity, good lubrication performance, and settling stability under conditions of 240℃, saturated salt, and high density. It can increase mechanical drilling speed, reduce drill bit wear, reduce drilling accidents such as differential pressure stuck pipe, and lower drilling time and overall costs for deep-ground oil and gas wells at 10,000 meters.

[0006] This invention is achieved through the following technical solution:

[0007] A water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 5-10 parts light diesel oil, 1-4 parts high-temperature resistant clay, 3-6 parts dendritic macromolecular filtration reducer, 2-4 parts temperature-responsive micelle shearing agent, 2-4 parts high-temperature resistant strong adsorption plugging agent, 3-5 parts nanocomposite polymer brush lubricant, and 1-3 parts high-temperature resistant system stabilizer.

[0008] According to a preferred embodiment of the present invention, the light diesel oil is one or a combination of two or more of 0#, -10#, -20# and -35# diesel oil, which are commercially available products.

[0009] According to a preferred embodiment of the present invention, the high-temperature resistant clay is obtained using the raw materials and preparation method described in Chinese patent document CN118374267A.

[0010] According to a preferred embodiment of the present invention, the dendritic macromolecular filtration loss reducing agent is prepared by the following method:

[0011] (1) Place the methanol solution of ethylenediamine in an ice-water bath and cool it to 0-2℃ under nitrogen protection;

[0012] (2) Add a methanol solution of methyl methacrylate to a methanol solution of ethylenediamine, let stand, and then react. After the reaction is complete, remove methanol and excess methyl methacrylate to obtain dendritic monomers.

[0013] (3) Add N,N-diethylacrylamide, methacryloylethyl sulfobetaine, lauryl hydroxy sulfobetaine and sodium p-styrene sulfonate to deionized water, and then add dendritic monomers under ultrasonic conditions to obtain monomer solution;

[0014] (4) The monomer solution was heated to the first reaction temperature under nitrogen protection, and cerium ammonium nitrate was added to carry out the first reaction; then the temperature was raised to the second reaction temperature, and 2,2'-azobisisobutylamidine dihydrochloride was added to carry out the second reaction; after the reaction was completed, the dendritic macromolecular filtration loss reducer was obtained by dialysis and freeze drying.

[0015] Preferably, the mass ratio of ethylenediamine to methanol in the methanol solution of ethylenediamine in step (1) is 1:4-6.

[0016] Preferably, in step (2), the mass ratio of methyl methacrylate to methanol in the methanol solution of methyl methacrylate is 1:4-6; and the molar ratio of methyl methacrylate to ethylenediamine is 5-10:1.

[0017] Preferably, in step (2), the methanol solution of methyl methacrylate is added dropwise to the methanol solution of ethylenediamine at a rate of 0.1-0.3 mL / s, and the temperature of the reaction system is controlled at 0-2℃ during the dropwise addition.

[0018] Preferably, the settling time in step (2) is 20-40 min and the settling temperature is 0-2℃.

[0019] Preferably, the reaction temperature in step (2) is 35-45℃ and the reaction time is 20-30h.

[0020] Preferably, in step (2), methanol and excess methyl methacrylate are removed by rotary evaporation at a temperature of 50-55°C.

[0021] Preferably, in step (3), the mass ratio of N,N-diethylacrylamide, methacryloylethyl sulfobetaine, lauryl hydroxy sulfobetaine, and sodium p-styrene sulfonate is 10:3-5:2-3:1-2; and the mass ratio of deionized water to N,N-diethylacrylamide is 3-8:1.

[0022] Preferably, the mass ratio of the dendritic monomer to N,N-diethylacrylamide in step (3) is 0.1-0.3:20.

[0023] Preferably, the mass ratio of cerium ammonium nitrate to N,N-diethylacrylamide in step (4) is 0.005-0.05:20; the first reaction temperature is 40-50℃, and the first reaction time is 3-5h.

[0024] Preferably, the mass ratio of 2,2'-azobisisobutylammonium dihydrochloride to N,N-diethylacrylamide in step (4) is 0.1-0.5:20; the second reaction temperature is 65-75℃, and the second reaction time is 2-4h.

[0025] Preferably, the dialysis step in step (4) is as follows: the reaction solution obtained from the reaction is naturally cooled to room temperature, and then transferred to a dialysis bag for dialysis purification in deionized water. The molecular weight cutoff of the dialysis bag is 3000-5000 Da, and the dialysis time is 12-36 h. The freeze-drying temperature is -30~-20℃, and the freeze-drying time is 20-40 h.

[0026] According to a preferred embodiment of the present invention, the temperature-responsive micelle shearing agent is prepared by the following method:

[0027] (i) Isobutyl acrylate, Span-20 and Tween-60 are added to white oil and stirred until completely dissolved to obtain an oil phase solution;

[0028] (ii) N-isopropylacrylamide, N-vinylcaprolactam and dimethyldiallylammonium chloride were added to deionized water and stirred until homogeneous to obtain an aqueous solution; under stirring conditions, the aqueous solution was added to the oil solution and stirred to obtain a reverse emulsion;

[0029] (iii) The reverse emulsion is heated to the reaction temperature under stirring and nitrogen protection, and an initiator is added to initiate the reaction; after the reaction is completed, it is cooled to obtain a temperature-responsive micelle slicing agent.

[0030] Preferably, in step (i), the mass ratio of isobutyl acrylate, Span-20 and Tween-60 is 10:3-5:0.5-2; the white oil is 3#, 5#, 7#, 10#, 15# or 20# white oil, and the mass ratio of the white oil to isobutyl acrylate is 4-8:1.

[0031] Preferably, in step (ii), the mass ratio of N-isopropylacrylamide, N-vinylcaprolactam, and dimethyldiallylammonium chloride is 10:4-6:2-4; the mass ratio of deionized water to N-isopropylacrylamide is 3-5:1; and the mass ratio of N-isopropylacrylamide in the aqueous solution to isobutyl acrylate in the oil solution is 1:1.

[0032] Preferably, in step (ii), after the aqueous solution is added to the oil solution, the stirring time is 20-40 min and the stirring speed is 400-600 r / min.

[0033] Preferably, the initiator in step (iii) is a combination of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is 2:1; and the mass ratio of the initiator to N-isopropylacrylamide is 0.1-0.5:10.

[0034] Preferably, the reaction temperature in step (iii) is 70-80°C and the reaction time is 5-7 h.

[0035] According to a preferred embodiment of the present invention, the high-temperature resistant strong adsorption blocking agent is obtained according to the raw materials and preparation method in Chinese patent document CN115651615A.

[0036] According to a preferred embodiment of the present invention, the nanocomposite polymer brush lubricant is prepared by the following method:

[0037] (I) Citric acid monohydrate, urea and nano-graphite were added to deionized water and sonicated to obtain a mixture. The mixture was then subjected to a hydrothermal reaction. After the reaction was completed, the mixture was cooled, centrifuged and freeze-dried to obtain composite nanoparticles.

[0038] (II) Lauryl methacrylate, hydroxyethyl acrylate, 2-methacryloyloxyethyl phosphocholine and pentamethyldiethylenetriamine were added to N,N-dimethylformamide and stirred until completely dissolved. Then, composite nanoparticles were added and ultrasonically dispersed evenly. Under nitrogen protection, the temperature was raised to the reaction temperature and azobisisobutyronitrile was added to carry out the reaction. After the reaction was completed, the nanocomposite polymer brush lubricant was obtained by cooling.

[0039] Preferably, the particle size of the nanographite in step (I) is 50-200 nm; the mass ratio of the citric acid monohydrate, urea and nanographite is 4:2-4:0.1-0.3; and the mass ratio of the deionized water to the citric acid monohydrate is 5-15:1.

[0040] Preferably, the temperature of the hydrothermal reaction in step (I) is 150-200℃, and the time of the hydrothermal reaction is 4-6h.

[0041] Preferably, the cooling in step (I) is natural cooling to room temperature, the freeze-drying temperature is -30~-20℃, and the freeze-drying time is 20-40h.

[0042] Preferably, in step (II), the mass ratio of lauryl methacrylate, hydroxyethyl acrylate, 2-methacryloyloxyethyl phosphocholine, and pentamethyldiethylenetriamine is 10:4-6:2-4:0.1-1; the mass ratio of N,N-dimethylformamide to lauryl methacrylate is 3-10:1; and the mass ratio of the composite nanoparticles to lauryl methacrylate is 0.5-1.5:10.

[0043] Preferably, the mass ratio of azobisisobutyronitrile to lauryl methacrylate in step (II) is 0.05-0.5:10.

[0044] Preferably, the reaction temperature in step (II) is 70-80°C and the reaction time is 5-7 hours.

[0045] According to a preferred embodiment of the present invention, the high-temperature resistant system stabilizer is a mixture of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride, wherein the mass ratio of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride in the mixture is 1:0.4-0.6:0.1-0.3; the molecular formula of the perfluoroalkyl betaine is C2. 15 H 15 F 17 N₂O₄S has the following structural formula:

[0046] .

[0047] According to the present invention, the preparation method of the above-mentioned deep-earth oil and gas lubrication and drag reduction water-based drilling fluid includes the following steps:

[0048] Add high-temperature resistant clay to water and stir for more than 24 hours. Then add light diesel oil and high-temperature resistant system stabilizer and stir for 1 hour. Then add dendritic macromolecular filtration loss reducer, temperature-responsive micelle shearing agent, high-temperature resistant strong adsorption plugging agent and nanocomposite polymer brush lubricant in sequence and stir evenly to obtain a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters.

[0049] Preferably, the preparation method of the deep-ground oil and gas lubrication and drag-reducing water-based drilling fluid includes the following steps:

[0050] Water was added to a high-speed mixing cup, and high-temperature resistant clay was added under low-speed stirring for more than 24 hours. Light diesel oil and high-temperature resistant system stabilizer were added, and high-speed stirring was carried out for 1 hour. Dendritic macromolecular filtration reducer was added, and high-speed stirring was carried out for 20 minutes. Temperature-responsive micelle shearing agent was added, and high-speed stirring was carried out for 20 minutes. High-temperature resistant strong adsorption and plugging agent was added, and high-speed stirring was carried out for 20 minutes. Nanocomposite polymer brush lubricant was added, and high-speed stirring was carried out for 20 minutes to obtain a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters. The low-speed stirring speed was 1000-3000 r / min, and the high-speed stirring speed was 8000-10000 r / min.

[0051] According to the present invention, the application of the above-mentioned water-based drilling fluid for lubricating and reducing drag in deep oil and gas formations can increase the mechanical drilling speed, reduce drill bit wear, reduce drilling accidents such as differential pressure stuck drill bit, and reduce drilling time and overall cost of deep oil and gas wells in the tens of thousands of meters deep during the drilling process of deep and ultra-deep oil and gas formations; the deep and ultra-deep oil and gas formations include, but are not limited to, formations in the tens of thousands of meters deep.

[0052] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0053] The technical features and beneficial effects of this invention are as follows:

[0054] 1. The water-based drilling fluid of this invention incorporates a dendritic macromolecular filtration loss reducer. This filtration loss reducer is a macromolecular polymer with a multi-branched structure, exhibiting a lower viscosity effect compared to traditional linear macromolecules. This facilitates the control of rheological properties under high-density conditions. Furthermore, its small mean square radius of gyration, high molecular rigidity, and resistance to molecular chain entanglement contribute to its superior performance under high-temperature and high-salt conditions. Each branch of the polymer can connect to multiple clay particles or weighting material particles, forming a high-strength three-dimensional network structure in the drilling fluid. This facilitates the suspension and dispersion of particles in the drilling fluid, maintaining good rheological properties while making the drilling fluid cake more compact and effectively reducing filtration loss. The amphoteric betaine structure in the macromolecular branched chains possesses surface activity, providing a wetting effect and further promoting the dispersion of weighting materials. Additionally, it enhances the salt resistance of the drilling fluid through polyelectrolytes.

[0055] 2. The water-based drilling fluid of this invention incorporates a temperature-responsive micelle shearing agent. This shearing agent is a temperature-responsive polymer material, which at room temperature consists of irregularly shaped micron-sized polymer particles that can disperse between the drilling fluid clay and weighting agent, playing a certain role in sealing and synergistically reducing filtration loss. Under high-temperature conditions, the shearing agent can partially soften and coat the drilling fluid mesh, further enhancing the strength of the drilling fluid mesh structure. This effectively increases the drilling fluid shear force with low viscosity-enhancing effect, maintaining a good dynamic-to-plastic ratio, improving the drilling fluid's suspension capacity for weighting materials, and enhancing the settling stability of high-density drilling fluids.

[0056] 3. The water-based drilling fluid of this invention incorporates a nanocomposite polymer brush lubricant. This lubricant is an organic-inorganic composite material. On one hand, the large specific surface area of ​​the inorganic nanoparticles enables the lubricant to form a denser and more uniform lubricating film on the drill string surface. On the other hand, the mutual displacement between the highly extended polymer brush and the nanoparticles creates a rolling effect, further reducing friction. Simultaneously, the nanocomposite structure enhances the polymer brush's resistance to temperature and salt, allowing it to maintain good lubrication even at 240°C and under saturated salt conditions.

[0057] 4. The drilling fluid system of this invention is an oil-in-water microemulsion formed by water and light diesel oil under the action of a high-temperature resistant stabilizer. Compared with a pure water-based fluid, it has better high-temperature resistance and lubrication coefficient. The addition of high-temperature resistant clay enhances the colloidal properties of the base fluid, providing more action sites for the treatment agent. Dendritic macromolecular filtration reducers and temperature-responsive micelle shearing agents synergistically form a robust network structure in the drilling fluid that resists ultra-high temperatures and high mineralization. Under ultra-high temperature, high mineralization, and high density conditions, it effectively reduces filtration loss, maintains good rheology, and suspends and weights materials and drill cuttings for extended periods. A high-temperature resistant strong adsorption plugging agent further seals the pores and fractures in the mud cake and formation, reducing filtration loss. A nanocomposite polymer brush lubricant forms a lubricating film on the drill string and mud cake, improving the drilling fluid's lubrication capacity and reducing drilling friction. The synergistic effect of various treatment agents enables the drilling fluid to have low viscosity, good lubrication performance, sedimentation stability and good rheological properties under conditions of 240℃, saturated salt and high density. This can increase the mechanical drilling rate, reduce drill bit wear, reduce drilling accidents such as differential pressure stuck pipe, and reduce drilling time and overall cost of oil and gas wells at depths of 10,000 meters. Detailed Implementation

[0058] The specific embodiments of the present invention will be further described below. The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the examples are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims. Furthermore, unless otherwise specified, all materials used in the following examples and comparative examples are commercially available, and all methods used are conventional methods in the art.

[0059] Unless otherwise specified, all “parts” in the following preparation examples and embodiments refer to parts by weight.

[0060] Preparation Example 1

[0061] The dendritic macromolecular filtration loss reducer was prepared according to the following method:

[0062] 1) Add 1.5g of ethylenediamine and 7.5g of methanol to a three-necked flask, stir thoroughly to obtain a methanol solution of ethylenediamine, place it in an ice-water bath, and cool it to 0℃ under nitrogen protection.

[0063] 2) Weigh 20g of methyl methacrylate and add it to 100g of methanol to obtain a methanol solution of methyl methacrylate. Add the obtained methanol solution of methyl methacrylate dropwise to the three-necked flask described in step 1) using a constant flow pump, controlling the dropping rate at 0.2mL / s. During the dropping process, control the temperature of the reaction system at 0-2℃. After the dropping is completed, let it stand at 0-2℃ for 30min, and then place the reaction system at 40℃ for 24h. After the reaction is completed, use a rotary evaporator at 50-55℃ to remove methanol and excess methyl methacrylate, and obtain a yellow viscous liquid as a dendritic monomer.

[0064] 3) Weigh 20g of N,N-diethylacrylamide, 8g of methacryloylethyl sulfobetaine, 5g of lauryl hydroxysulfobetaine and 2g of sodium p-styrene sulfonate and add them to 100g of deionized water. Then, under ultrasonic conditions, add 0.2g of the dendritic monomer obtained in step 2) to obtain a monomer solution.

[0065] 4) Transfer the obtained monomer solution to another three-necked flask, heat to 45°C under nitrogen protection, add 0.01 g of cerium ammonium nitrate, react at 45°C for 4 h, then heat to 70°C, add 0.2 g of 2,2'-azobisisobutylamidine dihydrochloride, and continue to react at 70°C for 3 h; then cool naturally to room temperature, transfer the obtained reaction solution to a dialysis bag (molecular weight cutoff of 3000 Da), dialyze to deionized water for 24 h, then freeze-dry (temperature -25°C, time 24 h), pulverize, and the resulting white powdery solid is the dendritic macromolecular filtration loss reducer.

[0066] Preparation Example 2

[0067] The temperature-responsive micelle slicing agent was prepared according to the following method:

[0068] 1) Add 10g of isobutyl acrylate, 4g of Span-20 and 1g of Tween-60 to 60g of 20# white oil and stir until completely dissolved to obtain an oil phase solution.

[0069] 2) Add 10g of N-isopropylacrylamide, 5g of N-vinylcaprolactam and 3g of dimethyldiallylammonium chloride to 40g of deionized water and stir until homogeneous to obtain an aqueous solution. Under stirring conditions of 500r / min, add the aqueous solution to the oil solution in step (1). After the addition is complete, continue stirring for 30min at a stirring speed of 500r / min to obtain a reverse emulsion.

[0070] 3) Transfer the reverse emulsion to a three-necked flask, maintain a rotation speed of 500 r / min, heat to 75°C with nitrogen gas, add 0.2 g potassium persulfate and 0.1 g sodium bisulfite to initiate the reaction, and react at 75°C for 6 h; after the reaction is complete, cool naturally to room temperature, and the resulting milky white semi-transparent liquid is the temperature-responsive micelle slicing agent.

[0071] Preparation Example 3

[0072] The nanocomposite polymer brush lubricant was prepared according to the following method:

[0073] 1) Add 4g of citric acid monohydrate, 3g of urea and 0.2g of nano-graphite (particle size of 100nm) to 40g of deionized water and sonicate to obtain a dark brown semi-transparent mixture. Transfer the mixture to a stainless steel hydrothermal reactor lined with PPL and react at 180℃ for 5h. After naturally cooling to room temperature, centrifuge the reaction solution and freeze-dry the precipitate at -25℃ for 24h to obtain composite nanoparticles.

[0074] 2) Add 10g lauryl methacrylate, 5g hydroxyethyl acrylate, 3g 2-methacryloyloxyethyl phosphocholine and 0.5g pentamethyldiethylenetriamine to 50g N,N-dimethylformamide, stir until completely dissolved, then add 1g of the composite nanoparticles obtained in step 1), and ultrasonically disperse for 10min to obtain a mixture; transfer the obtained mixture to a three-necked flask, heat to 75℃ under nitrogen protection, add 0.1g azobisisobutyronitrile, and react at 75℃ for 6h; after the reaction is complete, cool naturally to room temperature, and the resulting viscous liquid is the nanocomposite polymer brush lubricant.

[0075] Comparative Preparation Example 1

[0076] A method for preparing a linear macromolecular filtration loss reducing agent includes the following steps:

[0077] 1) Weigh 20g of N,N-diethylacrylamide, 8g of methacryloylethyl sulfobetaine, 5g of lauryl hydroxy sulfobetaine and 2g of sodium p-styrene sulfonate and add them to 100g of deionized water. Stir well to obtain a monomer solution.

[0078] 2) Transfer the monomer solution to a three-necked flask, heat to 45°C under nitrogen protection, add 0.01 g of cerium ammonium nitrate, react at 45°C for 4 h, then heat to 70°C, add 0.2 g of 2,2'-azobisisobutylamidine dihydrochloride, and continue reacting at 70°C for 3 h; then cool naturally to room temperature, transfer the resulting reaction solution to a dialysis bag (molecular weight cutoff of 3000 Da), dialyze to deionized water for 24 h, then freeze-dry (temperature -25°C, time 24 h), pulverize, and the resulting white powdery solid is the linear macromolecular filtration reducer.

[0079] Comparative Preparation Example 2

[0080] A method for preparing a micelle polymer is described in Preparation Example 2, except that the thermosensitive monomer N-isopropylacrylamide in the original formulation is replaced with an equal mass of acrylamide, and the thermosensitive monomer N-vinylcaprolactam is replaced with an equal mass of N-vinylpyrrolidone. The specific synthesis method is as follows:

[0081] 1) Add 10g of isobutyl acrylate, 4g of Span-20 and 1g of Tween-60 to 60g of 20# white oil and stir until completely dissolved to obtain an oil phase solution.

[0082] 2) Add 10g acrylamide, 5g N-vinylpyrrolidone and 3g dimethyl diallyl ammonium chloride to 40g deionized water and stir until homogeneous to obtain an aqueous solution; under stirring conditions of 500r / min, add the aqueous solution to the oil solution of step (1), and after the addition is complete, continue stirring for 30min under stirring conditions of 500r / min to obtain a reverse emulsion.

[0083] 3) Transfer the reverse emulsion to a three-necked flask, maintain a rotation speed of 500 r / min, heat to 75°C with nitrogen gas, add 0.2 g potassium persulfate and 0.1 g sodium bisulfite to initiate the reaction, and react at 75°C for 6 h; after the reaction is complete, cool naturally to room temperature to obtain micelle polymer.

[0084] Comparative preparation example 3

[0085] A method for preparing a polymer brush lubricant is described in Preparation Example 3, except that the preparation and addition of composite nanoparticles are omitted. The specific synthesis method is as follows:

[0086] 1) Add 10g lauryl methacrylate, 5g hydroxyethyl acrylate, 3g 2-methacryloyloxyethyl phosphocholine and 0.5g pentamethyldiethylenetriamine to 50g N,N-dimethylformamide and stir until completely dissolved to obtain a mixture. Transfer the resulting mixture to a three-necked flask, heat to 75°C under nitrogen protection, add 0.1g azobisisobutyronitrile, and react at 75°C for 6 hours. After the reaction is complete, allow it to cool naturally to room temperature. The resulting viscous liquid is the polymer brush lubricant.

[0087] The dendritic macromolecular filtration loss reducer, temperature-responsive micelle slicing agent, and nanocomposite polymer brush lubricant used in the examples and comparative examples were prepared according to the methods described in Preparation Examples 1-3.

[0088] Example 1

[0089] A water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 8 parts light diesel oil, 2 parts high-temperature resistant clay, 4 parts dendritic macromolecular filtration loss reducer, 3 parts temperature-responsive micelle shearing agent, 3 parts high-temperature resistant strong adsorption plugging agent, 4 parts nanocomposite polymer brush lubricant, and 2 parts high-temperature resistant system stabilizer.

[0090] The light diesel oil is commercially available No. 0 diesel oil;

[0091] The high-temperature resistant clay was prepared according to the method described in Example 1 of Chinese patent document CN118374267A;

[0092] The high-temperature resistant, strong adsorption blocking agent was prepared according to the method described in Example 1 of Chinese patent document CN115651615A;

[0093] The high-temperature stabilizer is a mixture of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride, wherein the mass ratio of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride in the mixture is 1:0.5:0.2; the molecular formula of the perfluoroalkyl betaine is C2. 15 H 15 F 17 N2O4S, the structural formula is shown below:

[0094] .

[0095] The preparation method of the above-mentioned deep-earth oil and gas lubrication and drag reduction water-based drilling fluid includes the following steps:

[0096] Water was added to a high-speed mixing cup, and high-temperature resistant clay was added under low-speed stirring for 30 hours. Light diesel oil and high-temperature resistant system stabilizer were added, and high-speed stirring was carried out for 1 hour. Dendritic macromolecular filtration reducer was added, and high-speed stirring was carried out for 20 minutes. Temperature-responsive micelle shearing agent was added, and high-speed stirring was carried out for 20 minutes. High-temperature resistant strong adsorption and plugging agent was added, and high-speed stirring was carried out for 20 minutes. Nanocomposite polymer brush lubricant was added, and high-speed stirring was carried out for 20 minutes to prepare water-based drilling fluid F1 for oil and gas lubrication and drag reduction at a depth of 10,000 meters. The low-speed stirring speed was 2000 r / min, and the high-speed stirring speed was 10000 r / min.

[0097] Example 2

[0098] A water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 5 parts light diesel oil, 1 part high-temperature resistant clay, 6 parts dendritic macromolecular filtration loss reducer, 4 parts temperature-responsive micelle shearing agent, 4 parts high-temperature resistant strong adsorption plugging agent, 3 parts nanocomposite polymer brush lubricant, and 1 part high-temperature resistant system stabilizer.

[0099] Other raw materials and drilling fluid preparation methods are the same as in Example 1, and F2, a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters, is obtained.

[0100] Example 3

[0101] A water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters comprises the following raw materials in parts by weight: 100 parts water, 10 parts light diesel oil, 4 parts high-temperature resistant clay, 3 parts dendritic macromolecular filtration loss reducer, 2 parts temperature-responsive micelle shearing agent, 2 parts high-temperature resistant strong adsorption plugging agent, 5 parts nanocomposite polymer brush lubricant, and 3 parts high-temperature resistant system stabilizer.

[0102] Other raw materials and drilling fluid preparation methods are the same as in Example 1, and F3, a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters, is obtained.

[0103] Comparative Example 1

[0104] A water-based drilling fluid is described in Example 1, except that it does not contain light diesel oil, and the composition of other raw materials is the same as in Example 1.

[0105] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of light diesel oil is omitted to obtain water-based drilling fluid DF1.

[0106] Comparative Example 2

[0107] A water-based drilling fluid is described in Example 1, except that no dendritic macromolecular filtration loss reducer is added, and the other raw material composition is the same as in Example 1.

[0108] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of dendritic macromolecular filtration reducer is omitted, and water-based drilling fluid DF2 is obtained.

[0109] Comparative Example 3

[0110] A water-based drilling fluid is described in Example 1, except that no temperature-responsive micelle shearing agent is added, and the other raw material composition is the same as in Example 1.

[0111] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of temperature-responsive micelle shearing agent is omitted, and water-based drilling fluid DF3 is obtained.

[0112] Comparative Example 4

[0113] A water-based drilling fluid is described in Example 1, except that it does not contain a high-temperature resistant, strong adsorption and plugging agent, and the other raw materials are the same as in Example 1.

[0114] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of a high-temperature resistant strong adsorption plugging agent is omitted, and water-based drilling fluid DF4 is obtained.

[0115] Comparative Example 5

[0116] A water-based drilling fluid is described in Example 1, except that it does not contain nanocomposite polymer brush lubricant, and the other raw material composition is the same as in Example 1.

[0117] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of nano-composite polymer brush lubricant is omitted, and water-based drilling fluid DF5 is obtained.

[0118] Comparative Example 6

[0119] A water-based drilling fluid is described in Example 1, except that no high-temperature system stabilizer is added, and the other raw material composition is the same as in Example 1.

[0120] The preparation method of the above-mentioned water-based drilling fluid is as described in Example 1, except that the addition of a high-temperature resistant system stabilizer is omitted, and water-based drilling fluid DF6 is obtained.

[0121] Comparative Example 7

[0122] A water-based drilling fluid is prepared as described in Example 1, except that the dendritic macromolecular filtration reducer is replaced with the linear macromolecular filtration reducer prepared in Comparative Preparation Example 1, resulting in water-based drilling fluid DF7.

[0123] Comparative Example 8

[0124] A water-based drilling fluid, as described in Example 1, is prepared by replacing the temperature-responsive micelle shearing agent with the micelle polymer prepared in Comparative Preparation Example 2, thereby obtaining water-based drilling fluid DF8.

[0125] Comparative Example 9

[0126] A water-based drilling fluid is prepared as described in Example 1, except that the nanocomposite polymer brush lubricant is replaced with the polymer brush lubricant prepared in Comparative Preparation Example 3, and the water-based drilling fluid DF9 is obtained.

[0127] Experimental Example 1

[0128] Take 400 mL of each of the above drilling fluids F1-F3 and DF1-DF9, and weigh them with barite to a density of 1.8 g / cm³. 3After adding saturated salt (36wt% NaCl) and stirring at 5000 rpm for 20 min, the mixture was transferred to an aging tank and placed in a roller furnace. It was then rolled at 240℃ for 16 hours. After cooling to room temperature, it was stirred at 5000 rpm for another 20 min. The apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API filtration loss (FL) of the drilling fluid were determined according to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids". API High temperature and high pressure filtration loss FL HTHP (240℃), the results are shown in Table 1.

[0129] Table 1 Drilling Fluid Rheological Filtration Performance Test

[0130]

[0131] The data above demonstrates that, under the synergistic effect of the filtration loss reducer, shear lifter, and plugging agent, the deep-ground oil and gas lubrication and drag reduction water-based drilling fluid of this invention exhibits good rheological and filtration loss properties at 240℃ high temperature, saturated salt, and 1.8 g / cm³. 3 Under these conditions, the dynamic shear force reaches 15 mPa, the dynamic-to-plastic ratio is maintained at around 0.4, and the high-temperature, high-pressure filtration loss is only 11.8 mL. The lack of key components or incorrect preparation methods for key materials can lead to a significant decline in drilling fluid performance, proving that only drilling fluid prepared according to the raw materials, proportions, and preparation methods disclosed in this invention can exhibit excellent performance.

[0132] Experimental Example 2

[0133] The lubrication performance of drilling fluids F1-F3 and DF1-DF9 was tested.

[0134] Take 400 mL of drilling fluids F1-F3 and DF1-DF9 respectively, and weigh them with barite to a density of 1.8 g / cm³. 3 Add 36wt% NaCl, stir at 5000rpm for 20min, then put into an aging tank, place in a roller furnace, and roll at 240℃ for 16h. After cooling to room temperature, stir at 5000rpm for 20min to obtain the drilling fluid to be tested.

[0135] The extreme pressure lubrication coefficients of different test slurries were tested using an extreme pressure lubrication instrument. The formula for calculating the extreme pressure lubrication coefficient is as follows:

[0136]

[0137] In the formula, K is the correction coefficient, dimensionless; M0 is the friction of water, dimensionless; M1 is the friction of the test slurry, dimensionless; and X is the extreme pressure lubrication coefficient, dimensionless.

[0138] The rotation and friction of the drill string under drilling fluid immersion during the drilling process were simulated. The lubrication ability of the drilling fluid on the metal was tested using a four-ball friction tester. The test conditions were a rotation speed of 1200 r / min, a load of 196 N, and a test temperature of 75 ± 2 ℃. The friction coefficients of different test slurries were also tested.

[0139] The test results are shown in Table 2.

[0140] Table 2 Drilling Fluid Lubricating Capacity Test

[0141]

[0142] As can be seen from the data in Table 2, under the action of microemulsion and lubricant, the drilling fluid system of the present invention has good lubrication ability, with an extreme pressure lubrication coefficient as low as 0.1301 and a four-ball friction coefficient as low as 0.038. The filtration loss reducer and shearing agent can enhance the overall temperature and salt resistance of the drilling fluid, make the weighting material well dispersed, and synergistically improve the lubrication ability of the drilling fluid under high temperature, high salt and high density conditions.

[0143] Experimental Example 3

[0144] The drilling fluids F1-F3 were tested for their weight-adding capacity.

[0145] Take 400 mL of drilling fluid F1-F3 respectively, and weigh them with barite until the density is 2.0 g / cm³. 3 2.2g / cm 3 and 2.4g / cm 3 Add 36wt% NaCl, stir at 5000rpm for 20min, then transfer to an aging tank, place in a roller furnace, and maintain a constant temperature of 240℃ for 16h. Remove and cool to room temperature, then stir at 5000rpm for another 20min to obtain the drilling fluid to be tested. Then, according to the petroleum and natural gas industry standard GB / T 16783.1-2014 "Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids", the apparent viscosity (AV, mPa·s), plastic viscosity (PV, mPa·s), dynamic shear force (YP, Pa), and API filtration loss (FL) of the above-mentioned drilling fluid were determined. API High temperature and high pressure filtration loss FL HTHP (240℃), the results are shown in Table 3.

[0146] Table 3 Drilling Fluid Weightability Test

[0147]

[0148] Table 3 shows that at a density of 2.0 g / cm³... 3 2.2g / cm 3 and 2.4g / cm 3 Under these conditions, the drilling fluid maintained good rheological and filtration properties, indicating that the drilling fluid has good weight-adding capacity and can support its use in high-density conditions.

[0149] Test Example 4

[0150] Settling stability tests were conducted on drilling fluids F1-F3.

[0151] Take 400 mL of drilling fluid F1-F3 respectively, and add barite to make the weight up to 2.4 g / cm³. 3 Add 36wt% NaCl, stir at 5000rpm for 20min, then transfer to an aging tank and place in a roller furnace. After vertical static aging at 240℃ for 16h, 48h, and 72h, record the density at the top of the drilling fluid column (lower free fluid layer). r t and the density at the bottom r b The static settling factor of the drilling fluid system is calculated using the following formula. Generally, a static settling factor greater than 0.50 and less than 0.52 indicates that the drilling fluid system has good settling stability.

[0152]

[0153] In the formula SF The static settling factor is dimensionless. r t Density at the top of the drilling fluid, g / cm³ 3 ; r b Density at the bottom of the drilling fluid, g / cm³ 3

[0154] The test results are shown in Table 4.

[0155] Table 4 Drilling Fluid Settling Stability Test

[0156]

[0157] As can be seen from Table 4, the static settling factor of the drilling fluid system remains between 0.50 and 0.52 as the aging time increases, indicating that the drilling fluid system can maintain good settling stability for a relatively long time.

[0158] In summary, the water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters of the present invention enables the drilling fluid to have low viscosity, good lubrication performance, sedimentation stability, and good rheological properties under conditions of 240°C, saturated salt, and high density, thus meeting the needs of oil and gas drilling at depths of 10,000 meters.

[0159] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. In addition, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be considered as the content disclosed by the present invention.

Claims

1. A water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters, characterized in that, The raw materials contain the following parts by weight: 100 parts water, 5-10 parts light diesel oil, 1-4 parts high-temperature resistant clay, 3-6 parts dendritic macromolecular filtration loss reducer, 2-4 parts temperature-responsive micelle shearing agent, 2-4 parts high-temperature resistant strong adsorption and blocking agent, 3-5 parts nanocomposite polymer brush lubricant, and 1-3 parts high-temperature resistant system stabilizer. The dendritic macromolecular filtration loss reducer was prepared according to the following method: (1) Place the methanol solution of ethylenediamine in an ice-water bath and cool it to 0-2℃ under nitrogen protection; (2) Add a methanol solution of methyl methacrylate to a methanol solution of ethylenediamine, let stand, and then react. After the reaction is complete, remove methanol and excess methyl methacrylate to obtain dendritic monomers. The molar ratio of methyl methacrylate to ethylenediamine is 5-10:

1. (3) N,N-diethylacrylamide, methacrylylethyl sulfobetaine, lauryl hydroxysulfobetaine and sodium p-styrene sulfonate were added to deionized water, and then dendritic monomers were added under ultrasonic conditions to obtain a monomer solution; the mass ratio of N,N-diethylacrylamide, methacrylylethyl sulfobetaine, lauryl hydroxysulfobetaine and sodium p-styrene sulfonate was 10:3-5:2-3:1-2; the mass ratio of dendritic monomers to N,N-diethylacrylamide was 0.1-0.3:20; (4) The monomer solution is heated to the first reaction temperature under nitrogen protection, and cerium ammonium nitrate is added to carry out the first reaction; then the temperature is raised to the second reaction temperature, and 2,2'-azobisisobutylamidine dihydrochloride is added to carry out the second reaction; after the reaction is completed, the solution is dialyzed and freeze-dried to obtain a dendritic macromolecular filtration reducer; the mass ratio of cerium ammonium nitrate to N,N-diethylacrylamide is 0.005-0.05:20; the first reaction temperature is 40-50℃, and the first reaction time is 3-5h; the mass ratio of 2,2'-azobisisobutylamidine dihydrochloride to N,N-diethylacrylamide is 0.1-0.5:20; the second reaction temperature is 65-75℃, and the second reaction time is 2-4h; The temperature-responsive micelle slicing agent was prepared according to the following method: (i) Isobutyl acrylate, Span-20 and Tween-60 are added to white oil and stirred until completely dissolved to obtain an oil phase solution; the mass ratio of isobutyl acrylate, Span-20 and Tween-60 is 10:3-5:0.5-2. (ii) N-isopropylacrylamide, N-vinylcaprolactam and dimethyldiallylammonium chloride are added to deionized water and stirred until homogeneous to obtain an aqueous phase solution; under stirring conditions, the aqueous phase solution is added to the oil phase solution and stirred to obtain a reverse emulsion; the mass ratio of N-isopropylacrylamide, N-vinylcaprolactam and dimethyldiallylammonium chloride is 10:4-6:2-4; the mass ratio of N-isopropylacrylamide in the aqueous phase solution to isobutyl acrylate in the oil phase solution is 1:1; (iii) The reverse emulsion was heated to the reaction temperature under stirring and nitrogen protection, and an initiator was added to initiate the reaction; after the reaction was completed, it was cooled to obtain a temperature-responsive micelle slicing agent. The nanocomposite polymer brush lubricant was prepared according to the following method: (I) Citric acid monohydrate, urea and nano-graphite are added to deionized water and ultrasonically mixed to obtain a mixture. The mixture is then subjected to a hydrothermal reaction. After the reaction is completed, the mixture is cooled, centrifuged and freeze-dried to obtain composite nanoparticles. The mass ratio of citric acid monohydrate, urea and nano-graphite is 4:2-4:0.1-0.

3. The hydrothermal reaction temperature is 150-200℃ and the hydrothermal reaction time is 4-6h. (II) Lauryl methacrylate, hydroxyethyl acrylate, 2-methacryloyloxyethyl phosphocholine and pentamethyldiethylenetriamine were added to N,N-dimethylformamide and stirred until completely dissolved. Then, composite nanoparticles were added and ultrasonically dispersed evenly. Under nitrogen protection, the temperature was raised to the reaction temperature, and azobisisobutyronitrile was added to carry out the reaction. After the reaction was completed, the mixture was cooled to obtain a nanocomposite polymer brush lubricant. The mass ratio of lauryl methacrylate, hydroxyethyl acrylate, 2-methacryloyloxyethyl phosphocholine and pentamethyldiethylenetriamine was 10:4-6:2-4:0.1-1. The mass ratio of the composite nanoparticles to lauryl methacrylate is 0.5-1.5:10; The light diesel oil is one or a combination of two or more of 0#, -10#, -20# and -35# diesel oil; The high-temperature resistant clay was prepared according to the following method: Bentonite and rettore were mixed at a mass ratio of 1:4, and then added to deionized water under stirring at 500 rpm to prepare a clay suspension with a total mass concentration of 10 wt% (bentonite and rettore). An inorganic aluminum treatment solution was prepared by adding an equal volume of 0.2 mol / L sodium hydroxide solution to a 0.3 mol / L aluminum chloride solution at 70°C under stirring at 500 rpm. The inorganic aluminum treatment solution was then added dropwise to the clay suspension at a rate of 2 drops / s, with the mass of the inorganic aluminum treatment solution being 10% of the total mass of the bentonite and rettore. The mixture was then stirred at room temperature at 600 rpm. The mixture was treated for 3 hours; then filtered, and the solid obtained by filtration was washed with deionized water at a ratio of 5 times the total mass of bentonite and retinoic acid. This washing and filtration process was repeated three times. The solid obtained was dried at 75°C for 24 hours to obtain inorganic aluminum-treated clay. 50g of the obtained inorganic aluminum-treated clay was dispersed in 500g of an ethanol-water solution, which was prepared by mixing ethanol and deionized water at a volume ratio of 4:

1. 1.5g of triethoxysilane was added under stirring at 500r / min, and after stirring for 30min, 0.15g of formic acid was added. The reaction was continued at room temperature for 5 hours. After filtration, the solid obtained by filtration was washed with 250g of deionized water. This washing and filtration process was repeated three times. The solid obtained was dried at 75°C for 24 hours to obtain high-temperature resistant clay. The high-temperature resistant, strong adsorption and blocking agent comprises the following raw materials in parts by weight: 100 parts water, 12 parts modified silica, 2 parts cationic monomer, 1 part pyrrole ring-containing monomer, 4 parts benzenesulfonate-containing monomer, 0.05 parts pH adjuster, and 0.05 parts initiator; the cationic monomer is methacryloyloxyethyltrimethylammonium chloride; the pyrrole ring-containing monomer is N-vinylpyrrolidone; the benzenesulfonate-containing monomer is sodium styrenesulfonate; the pH adjuster is triethylamine; and the initiator is ammonium persulfate. The modified silica is prepared by the following method: 4 parts vinyltriethoxysilane are added dropwise to 100 parts mixed solvent, which is obtained by mixing water and anhydrous ethanol in a volume ratio of 10:90, for 5 minutes, followed by stirring for 2 hours to obtain a silane coupling agent solution; 20 parts of silica were dispersed in 100 parts of anhydrous ethanol to obtain a suspension; the obtained silane coupling agent solution was heated to 60°C, and the obtained suspension was added, followed by stirring at 60°C for 5 hours; after the reaction was completed, the obtained reaction solution was added to acetone for precipitation for 24 hours, with a volume ratio of reaction solution to acetone of 1:2, then filtered, and the obtained precipitate was vacuum dried at 60°C to constant weight to obtain modified silica; the preparation method of the high-temperature resistant strong adsorption blocking agent includes the following steps: adding modified silica to a flask containing water, and sonicating for 30 minutes under mechanical stirring at 25°C. After sonication, cationic monomers, pyrrole-containing monomers, and benzenesulfonate-containing monomers were added sequentially. After stirring until fully dispersed, pH adjuster was added and stirred evenly. The flask was then heated to 60°C in a water bath while stirring and heating. Nitrogen gas was purged for 30 minutes to remove oxygen. Initiator was then added to the flask, and the reaction was maintained at 60°C for 6 hours. After the reaction was completed, the reaction product was removed, washed three times with acetone, and dried at 80°C to constant weight to obtain the final product. The high-temperature resistant system stabilizer is a mixture of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride, wherein the mass ratio of perfluoroalkyl betaine, Span-85, and dioctadecyl dimethyl ammonium chloride in the mixture is 1:0.4-0.6:0.1-0.3; the molecular formula of the perfluoroalkyl betaine is C0.

05. 15 H 15 F 17 N₂O₄S has the following structural formula: 。 2. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, In step (1), the mass ratio of ethylenediamine to methanol in the methanol solution of ethylenediamine is 1:4-6; In step (2), the mass ratio of methyl methacrylate to methanol in the methanol solution of methyl methacrylate is 1:4-6; the methanol solution of methyl methacrylate is added dropwise to the methanol solution of ethylenediamine at a rate of 0.1-0.3 mL / s, and the temperature of the reaction system is controlled at 0-2℃ during the addition process; the standing time is 20-40 min, and the standing temperature is 0-2℃; the reaction temperature is 35-45℃, and the reaction time is 20-30 h; in step (2), methanol and excess methyl methacrylate are removed by rotary evaporation at a temperature of 50-55℃.

3. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, The mass ratio of deionized water to N,N-diethylacrylamide in step (3) is 3-8:1; The dialysis step in step (4) is as follows: the reaction solution obtained from the reaction is naturally cooled to room temperature, and then transferred to a dialysis bag for dialysis purification in deionized water. The molecular weight cutoff of the dialysis bag is 3000-5000 Da, and the dialysis time is 12-36 h. The freeze-drying temperature is -30~-20℃, and the freeze-drying time is 20-40 h.

4. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, The white oil mentioned in step (i) is 3#, 5#, 7#, 10#, 15# or 20# white oil, and the mass ratio of the white oil to isobutyl acrylate is 4-8:1; the mass ratio of deionized water to N-isopropylacrylamide mentioned in step (ii) is 3-5:1; in step (ii), after the aqueous phase solution is added to the oil phase solution, the stirring time is 20-40 min and the stirring speed is 400-600 r / min.

5. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, The initiator in step (iii) is a combination of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is 2:1; the mass ratio of the initiator to N-isopropylacrylamide is 0.1-0.5:10; the reaction temperature is 70-80℃, and the reaction time is 5-7h.

6. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, The nano-graphite in step (I) has a particle size of 50-200 nm; the mass ratio of deionized water to citric acid monohydrate is 5-15:1; the cooling is natural cooling to room temperature; the freeze-drying temperature is -30~-20℃; and the freeze-drying time is 20-40 h.

7. The water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, In step (II), the mass ratio of N,N-dimethylformamide to lauryl methacrylate is 3-10:1; the mass ratio of azobisisobutyronitrile to lauryl methacrylate is 0.05-0.5:10; the reaction temperature is 70-80℃; and the reaction time is 5-7h.

8. The preparation method of the water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, The steps include: adding high-temperature resistant clay to water and stirring for more than 24 hours, then adding light diesel oil and high-temperature resistant system stabilizer and stirring for 1 hour, then sequentially adding dendritic macromolecular filtration loss reducer, temperature-responsive micelle shearing agent, high-temperature resistant strong adsorption plugging agent and nanocomposite polymer brush lubricant and stirring evenly to obtain a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters.

9. The preparation method of the water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters according to claim 8, characterized in that, The steps include: adding water to a high-speed mixing cup, adding high-temperature resistant clay while stirring at low speed, and stirring at low speed for more than 24 hours; adding light diesel oil and high-temperature resistant system stabilizer, and stirring at high speed for 1 hour; adding dendritic macromolecular filtration loss reducer, and stirring at high speed for 20 minutes. Temperature-responsive micelle shearing agent was added and stirred at high speed for 20 minutes; high-temperature resistant strong adsorption and plugging agent was added and stirred at high speed for 20 minutes; nano-composite polymer brush lubricant was added and stirred at high speed for 20 minutes to prepare a water-based drilling fluid for oil and gas lubrication and drag reduction at a depth of 10,000 meters; the low-speed stirring speed was 1000-3000 r / min and the high-speed stirring speed was 8000-10000 r / min.

10. The application of the water-based drilling fluid for oil and gas lubrication and drag reduction at depths of 10,000 meters as described in claim 1, characterized in that, In the drilling process for deep and ultra-deep oil and gas formations, the deep and ultra-deep oil and gas formations are formations tens of thousands of meters deep.

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