An anti-260-degree ultra-high temperature modified fatty acid oleyl drilling fluid wetting agent, a preparation method and application thereof

Abstract

The application provides an anti-260 DEG C ultra-high temperature modified fatty acid oil base drilling fluid wetting agent and a preparation method and application thereof, and belongs to the oil field chemical field of the petroleum industry. The preparation method of the wetting agent comprises the following steps: castor oil acid and base material fatty acid are mixed, after dehydration treatment, solid super strong acid catalyst I is added, and polyhydric alcohol is added for reaction; after the reaction is completed, filtration is carried out, and modified fatty acid is obtained; the obtained modified fatty acid is subjected to dehydration treatment, then solid super strong acid catalyst II is added, then a grafting reagent containing an epoxy group is added, and ring-opening grafting reaction is carried out; then a polyhydroxy compound is added, and esterification crosslinking reaction is carried out; high-temperature stabilizing additives are added to the obtained reaction solution, and aging treatment is carried out; then hot filtration is carried out, the obtained filtrate is cooled, an oil phase dispersion medium is added, stirring is uniformly carried out, and the wetting agent is obtained. The wetting agent can reduce the oil-solid interfacial tension and improve the wettability of the oil base drilling fluid to drill cuttings, well wall rocks and weighting materials.

Description

Technical Field

[0001] This invention relates to a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃, its preparation method and application, belonging to the field of oilfield chemistry in the petroleum industry. Background Technology

[0002] As oil and gas exploration continues to develop into deeper, ultra-deep, and complex formations, downhole temperatures are constantly rising. Deep wells, ultra-deep wells, and high-temperature, high-pressure wells are increasingly common, with well sections exceeding 200°C being quite prevalent. Some ultra-deep wells can reach temperatures above 240°C, and under extreme conditions, these temperatures approach or exceed 260°C. In such high-temperature environments, the thermal stability and overall performance of the drilling fluid system directly affect the safety and economy of drilling operations. Oil-based drilling fluids, with their excellent inhibition, lubrication, and wellbore stabilization capabilities, are widely used in high-temperature, high-pressure, and complex formation drilling. However, this system relies on the synergistic effect of various functional processing agents. Among them, wetting agents, as key materials for regulating the surface wetting state of solid particles, maintaining emulsion stability, and improving rheological properties, are particularly important for high-temperature stability. Under ultra-high temperature conditions above 260°C, conventional wetting agents are prone to thermal degradation and interfacial activity decline, leading to the destruction of the oil-based drilling fluid emulsion system, uneven solid wetting, severe performance deterioration, and even potential downhole accidents. Therefore, developing oil-based drilling fluid wetting agents that can maintain efficient wetting and interfacial stability in ultra-high temperature environments of 260℃ for a long time has become a key technical challenge that urgently needs to be overcome in the field of oilfield chemistry.

[0003] The main functions of wetting agents in oil-based drilling fluids include: first, altering the surface wettability of solid particles, allowing drill cuttings, weighting materials, and other solid particles in the drilling fluid to be preferentially wetted by the oil phase, thereby maintaining the water-in-oil structure; second, reducing the interfacial tension between oil and water, and between oil and solids, increasing the strength of the emulsion film, and enhancing the stability of the system; and third, improving the rheological and lubricating properties of the drilling fluid. Currently, research on improving the temperature resistance of wetting agents both domestically and internationally mainly focuses on modifying the surface molecular structure. For example, patent document CN117229766A modifies oxidized plant polyphenols with organic amines to obtain an organic amine-modified plant polyphenol drilling fluid wetting agent. This additive can effectively improve the high-temperature and high-pressure rheological stability and sedimentation stability of drilling fluids. Patent document CN116496767A describes a wetting agent prepared using alkyl dimethyl carboxylate betaine, 3-sulfopropyl alkyl dimethyl betaine, dioctyl sulfonated succinate, and water. This agent exhibits good solid-phase wetting at high temperatures and good compatibility with anionic, cationic, or nonionic oil-based emulsifiers. However, some wetting agents have low wetting reversal efficiency and insufficient adaptability or specificity to different types or surface properties of solid phases, making it difficult to achieve ideal and stable wetting effects. Furthermore, at ultra-high temperatures of 260°C, these wetting agents struggle to maintain long-term effective suspension stability in oil-based drilling fluid systems. While commercially available products (such as the HYPERWET® series) improve performance through compounding processes, their mechanism of action remains based on physical adsorption and interfacial coating, which carries a risk of desorption under long-term high-temperature dynamic environments and lacks sufficient synergistic stability with complex formulations. Patent document WO2021097662A1 employs the direct condensation of fatty acid esters with polyhydroxy organic amines (such as triethanolamine). The principle behind this is the introduction of multiple hydroxyl groups, ether bonds, and even aromatic ring structures to enhance the thermodynamic stability and interfacial adsorption strength of the molecule. These molecules attempt to maintain a more stable adsorption conformation at high temperatures by increasing hydrogen bonding sites and steric hindrance. However, the synthesis of multifunctional structures is more complex, and some functional groups (such as hydroxyl groups) may undergo dehydration or oxidation reactions at high temperatures. Furthermore, excessively enhanced polarity may lead to poor dispersibility in the oil phase or disrupt emulsion equilibrium due to competition with emulsifiers for the interface, posing a significant challenge to the overall formulation compatibility.

[0004] In summary, existing technologies have failed to address the challenges of thermal degradation of chemical bonds, reversible physical adsorption, and interfacial competition among multiple components at ultra-high temperatures of 260°C. Therefore, there is an urgent need to develop an oil-based drilling fluid wetting agent capable of maintaining high-efficiency wetting and interfacial stability over extended periods in ultra-high temperature environments of 260°C. Summary of the Invention

[0005] To address the shortcomings of existing technologies, particularly the problems of molecular structure breakage, interfacial adsorption layer instability, decreased wetting capacity, and deteriorated rheological properties of existing oil-based drilling fluid wetting agents under ultra-high temperature conditions above 260℃, this invention provides a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃, its preparation method, and its application. Based on the principle of high-temperature resistant molecular structure design, this invention uses a fatty acid with high thermal stability as the core framework, and prepares a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃ through grafting and modification of specific functional groups. This wetting agent, through the introduction of temperature-resistant groups and spatial structure, not only maintains molecular structural stability at extreme temperatures of 260℃ and above, preventing decomposition and performance degradation, but also effectively reduces oil / solid interfacial tension, significantly improves the wettability of oil-based drilling fluids on drill cuttings, wellbore rock, and weighting materials, and ensures emulsification stability and rheological controllability of the drilling fluid system at high temperatures. The wetting agent of this invention fundamentally overcomes the limitations of existing alcohol ether and ordinary surfactant wetting agents in ultra-high temperature conditions, providing key support for safe and efficient drilling in deep wells, ultra-deep wells, and high-difficulty high-temperature formations, and has important engineering practical value and promotion prospects.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃ includes the following steps:

[0008] (1) Mix ricinoleic acid and base fatty acid, heat and dehydrate, add solid superacid catalyst I, continue to heat to the reaction temperature, add polyol to react; after the reaction is completed, cool down and filter to obtain modified fatty acid;

[0009] (2) After dehydrating the modified fatty acid obtained in step (1), add solid superacid catalyst II, stir evenly, add grafting reagent containing epoxy group, and carry out ring-opening grafting reaction; then add polyhydroxy compound and carry out esterification crosslinking reaction.

[0010] (3) After the esterification and crosslinking reaction is completed, a high-temperature stabilizing agent is added to the resulting reaction solution for aging treatment; then hot filtration is performed, and after the resulting filtrate is cooled, an oil phase dispersion medium is added and stirred evenly to obtain a modified fatty acid oil-based drilling fluid wetting agent resistant to 260℃ ultra-high temperature.

[0011] According to a preferred embodiment of the present invention, the base fatty acid in step (1) is one or more of oleic acid, linoleic acid, stearic acid, and palmitic acid, and the mass ratio of ricinoleic acid to base fatty acid is 1-3:1.

[0012] According to a preferred embodiment of the present invention, the temperature of the heating and dehydration treatment in step (1) is 110-130°C, and the time of the heating and dehydration treatment is 0.5-2h; the heating and dehydration treatment is carried out under a nitrogen atmosphere.

[0013] According to a preferred embodiment of the present invention, the solid superacid catalyst I in step (1) is SO4. 2- / ZrO2、SO4 2- / TiO2、WO3 / ZrO2、SO4 2- One or more of Fe3O4, wherein the mass of the solid superacid catalyst I is 1-5% of the total mass of ricinoleic acid and the base fatty acid; wherein the solid superacid catalyst I is a commercially available product or prepared according to existing methods.

[0014] According to a preferred embodiment of the present invention, the polyol in step (1) is one of glycerol, pentaerythritol, and trimethylolpropane, and the mass ratio of the polyol to ricinoleic acid is 0.1-0.4:1.

[0015] According to a preferred embodiment of the present invention, the reaction temperature in step (1) is 160-180°C, the reaction time is 2-4 hours, and the reaction is carried out under a nitrogen atmosphere.

[0016] According to a preferred embodiment of the present invention, the cooling in step (1) is to cool down to 90-100°C and perform thermal filtration.

[0017] According to a preferred embodiment of the present invention, the temperature of the dehydration treatment in step (2) is 110-130°C, and the time of the dehydration treatment is 1-3 hours.

[0018] According to a preferred embodiment of the present invention, the solid superacid catalyst II in step (2) is the same as the solid superacid catalyst I in step (1); the mass of the solid superacid catalyst II is 1-4% of the mass of the modified fatty acid, and more preferably 2-3%.

[0019] According to a preferred embodiment of the present invention, in step (2), the temperature at which the solid superacid catalyst II is added and the stirring is carried out is 145-155°C, the stirring time is 20-40 min, and the stirring speed is 200-500 r / min.

[0020] According to a preferred embodiment of the present invention, the grafting agent containing epoxy groups in step (2) is one or more of epoxidized soybean oil, phenyl glycidyl ether, glycidyl methacrylate, and glycidyl trimethylammonium chloride, and the mass ratio of the grafting agent containing epoxy groups to the modified fatty acid is 0.15-0.25:1; the grafting agent containing epoxy groups is added dropwise to the system at a dropping rate of 1-2 mL / min and a dropping temperature of 145-155℃.

[0021] According to a preferred embodiment of the present invention, the temperature of the ring-opening grafting reaction in step (2) is 160-175°C, and the time of the ring-opening grafting reaction is 2-4 hours.

[0022] According to a preferred embodiment of the present invention, the polyhydroxy compound in step (2) is one or more of pentaerythritol, trimethylolpropane, xylitol, and sorbitol, and the mass ratio of the polyhydroxy compound to the modified fatty acid is 0.05-0.15:1.

[0023] According to a preferred embodiment of the present invention, the temperature of the esterification crosslinking reaction in step (2) is 180-200°C, and the time of the esterification crosslinking reaction is 3-5 hours.

[0024] According to a preferred embodiment of the present invention, all operations in step (2) are carried out under a nitrogen atmosphere.

[0025] According to a preferred embodiment of the present invention, the high-temperature stabilizing agent in step (3) is one or more of biphenyl, 1-phenylnaphthalene, 2-phenylnaphthalene, diphenyl ether, dibenzyltoluene, and monobenzyltoluene, and the mass ratio of the high-temperature stabilizing agent to the modified fatty acid is 0.05-0.15:1.

[0026] According to a preferred embodiment of the present invention, the temperature of the aging process in step (3) is 210-230°C, and the aging process time is 1-3 hours; the aging process is carried out under nitrogen protection.

[0027] According to a preferred embodiment of the present invention, the hot filtration step in step (3) is as follows: the reaction solution after aging is cooled to 110-120°C and filtered to recover the solid superacid catalyst.

[0028] According to a preferred embodiment of the present invention, in step (3), the obtained filtrate is cooled to 70-80°C; the oil phase dispersion medium is one or more of mineral oil, synthetic oil, and white oil, and the white oil is No. 5 white oil, No. 7 white oil, or No. 10 white oil; the mass ratio of the oil phase dispersion medium to the modified fatty acid is 0.4-0.5:1; the stirring speed is 300-500 r / min, and the stirring time is 50-70 min.

[0029] According to a preferred embodiment of the present invention, in step (3), after stirring is completed, a filtration step is further included, specifically as follows: the mixture obtained by stirring is naturally cooled to room temperature and then filtered, wherein the pore size of the filter membrane used for filtration is ≤0.5μm.

[0030] This invention provides a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃, which is prepared using the above-described preparation method.

[0031] According to the present invention, the above-mentioned modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperature of 260°C is used in oil-based drilling fluids.

[0032] The technical features and beneficial effects of this invention are as follows:

[0033] 1. This invention uses ricinoleic acid-modified fatty acids as the lipophilic backbone to construct the molecular body, enabling the product to exhibit good solubility and dispersibility in oil-based drilling fluids. Through epoxy ring-opening grafting and multi-hydroxyl crosslinking, a multi-functional three-dimensional network structure is formed, enhancing the adsorption strength and coverage density of the molecules on solid surfaces such as barite and rock cuttings. This ensures stable adsorption even under ultra-high temperature conditions, inhibiting desorption and wetting reversal, and guaranteeing system stability. This invention improves molecular thermal stability and interfacial anchoring ability by strengthening the fatty acid backbone, constructing stable chemical bonds through epoxy grafting, forming a three-dimensional network structure through multi-hydroxyl crosslinking, and embedding high-temperature stabilizing agents into the molecular system, achieving a simultaneous improvement in wetting performance and system stability.

[0034] 2. The lubricant molecules of the present invention have stable structures such as ester bonds and ether bonds, and aromatic high-temperature resistant components are introduced into the main chain to improve the rigidity of the molecular chain and thermal-oxidative stability, enhance the thermal decomposition temperature and anti-aging ability, so that the wetting agent can maintain structural integrity and functional activity at 260°C.

[0035] 3. This invention uses a solid superacid (sulfate-promoting oxide or composite oxide) as a heterogeneous catalyst to promote transesterification, epoxy ring-opening and cross-linking reactions. After the reaction, the catalyst is recovered and reused through hot filtration, reducing waste acid emissions and equipment corrosion.

[0036] 4. This invention employs a stepwise structural control approach for synthesis. First, using ricinoleic acid-modified fatty acids as the lipophilic backbone, polyhydroxyl active sites are introduced through transesterification, enhancing molecular reactivity and oil-phase compatibility, forming a basic structure that can be further modified. Epoxy-containing compounds undergo ring-opening reactions with hydroxyl groups, forming stable ether bonds in the main chain and increasing molecular weight and chain rigidity, thus enhancing the strength and heat resistance of the interfacial adsorption film. Polyhydroxyl compounds construct spatial network structures between molecules through esterification crosslinking, improving the structural strength and high-temperature shear resistance, preventing molecular migration and desorption under ultra-high temperature conditions. High-temperature stabilizing agents containing aromatic or fused ring structures participate in the maturation process, embedding heat-resistant structural units into the molecular system, improving the molecular chain's resistance to thermo-oxidative degradation, and maintaining the stability of the main chain structure and functional groups at temperatures above 260°C. The synthesis process of this invention implements segmented temperature control, nitrogen protection, constant-rate dripping, and dehydration control to reduce side reactions, improve structural controllability and batch stability. The product, after homogenization and filtration, exhibits stable performance and meets the requirements for ultra-high temperature oil-based drilling fluid applications.

[0037] In summary, this invention uses ricinoleic acid-modified fatty acids as the base material, combined with epoxy group-containing compounds and polyhydroxy compounds as core reagents, and a solid superacid as a recyclable heterogeneous catalyst. Through transesterification modification, epoxy ring-opening grafting, polyhydroxy cross-linking condensation, and the introduction of high-temperature stabilizing agents, a three-dimensional network structure composite wetting agent molecule is constructed. Specifically, the ricinoleic acid-modified fatty acid forms a lipophilic skeleton to ensure dispersion and wettability, while epoxy grafting and polyhydroxy cross-linking form stable chemical bonds to prevent desorption at ultra-high temperatures. The high-temperature stabilizing agent is embedded in the main chain to enhance molecular thermal stability, preventing chain breakage and functional group failure, thus adapting to ultra-high temperature deep well drilling fluid conditions. Through the above structural design, the wetting agent prepared by this invention can maintain good wetting reversal ability, interfacial adsorption stability, and rheological and filtration control performance even at an ultra-high temperature of 260℃, meeting the application requirements of deep and ultra-deep well drilling fluid systems for ultra-high temperature stability. Attached Figure Description

[0038] Figure 1 The infrared spectrum of the modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperature of 260℃ prepared in Example 1. Detailed Implementation

[0039] The present invention will be described in detail below with reference to specific embodiments, but is not limited thereto.

[0040] The epoxy value of the epoxidized soybean oil used in the examples is 6, which is the mass of 6 grams of oxygen / 100 grams of epoxidized soybean oil.

[0041] The solid superacid catalyst SO4 used in the examples 2- ZrO2 was prepared according to the following method:

[0042] Zirconium oxychloride octahydrate was added to deionized water and stirred until the solution became clear, yielding a 0.4 mol / L aqueous solution of zirconium oxychloride. Concentrated ammonia (25 wt%) was added dropwise (2 drops / s) with stirring until a thick suspension was formed. The addition of concentrated ammonia was stopped when pH=9, and stirring continued for 15 min. After standing for 24 h, the solution was filtered. The precipitate was washed with deionized water until the filtrate was neutral and dried at 120 °C for 12 h to obtain a zirconium hydroxide precursor. The obtained zirconium hydroxide precursor was ground into powder and impregnated with a 1 mol / L sulfuric acid solution (mass ratio of zirconium hydroxide precursor to sulfuric acid solution: 1:5) for 2 h. Excess sulfuric acid was filtered off, and the resulting solid was dried at 120 °C for 12 h. It was then calcined in a muffle furnace at 650 °C for 3 h with a heating rate of 5 °C / min. The calcined powder was a solid superacid catalyst, SO42-. 2- / ZrO2.

[0043] Example 1

[0044] A method for preparing a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃ includes the following steps:

[0045] (1) Add 70g of ricinoleic acid and 30g of oleic acid to a four-necked flask that has been dried, start stirring at 350r / min, and purge the air with nitrogen for 10min; then raise the temperature to 120℃ and dehydrate under nitrogen atmosphere for 1h until no water is discharged from the separator; while maintaining nitrogen and stirring, add 3g of solid superacid catalyst SO4. 2- / ZrO2, continue heating to 170℃, slowly add 15g of glycerol to the system, control the addition time to 20min, after the addition is complete, under nitrogen protection, carry out the transesterification modification reaction at 170℃ for 3h, the water generated in the reaction is continuously discharged through a water separator; after the reaction is completed, cool down to 100℃, filter while hot to recover the catalyst, and obtain ricinoleic acid modified fatty acid with multiple hydroxyl active sites, which is the basic raw material modified fatty acid used for subsequent synthesis of wetting agent.

[0046] (2) Add 100g of modified fatty acid to a dried four-necked reaction flask, turn on the stirrer, adjust the speed to 350r / min, and simultaneously purge nitrogen for 10min to purge the air; turn on the heating device and gradually raise the temperature to 120℃, and dehydrate at a constant temperature under a nitrogen atmosphere for 2h until no obvious water is separated from the water separator, ensuring that the system is in an anhydrous environment; after dehydration is completed, continue to purge nitrogen and maintain a stirring rate of 350r / min, and add 2g of solid superacid catalyst SO4 to the system. 2- / ZrO2, continue heating to 150℃, stir at constant temperature for 30 min to ensure the catalyst is uniformly dispersed in the raw materials; keep the system temperature stable at 150℃, slowly add 20g of epoxidized soybean oil through a constant pressure dropping funnel, control the dropping rate to 1mL / min to avoid excessive local concentration leading to side reactions; after the addition is complete, heat to 165℃, and carry out the ring-opening grafting reaction at constant temperature of 165℃ for 3 h under nitrogen atmosphere;

[0047] (3) After the grafting reaction is completed, the system temperature is gradually raised to 190℃ at a rate of 5℃ / min. 10g pentaerythritol is added to the system and the esterification crosslinking reaction is carried out at a constant temperature of 190℃ for 4h under a nitrogen atmosphere. The trace amount of water generated during the reaction is discharged in time through a water separator to promote the forward reaction.

[0048] (4) After the cross-linking reaction is completed, the system is heated to 220°C, 8g of biphenyl is added to the system, and the mixture is stirred and kept at a constant temperature for 2 hours under a nitrogen atmosphere. After the maturation is completed, the heating is stopped, nitrogen protection is maintained and the rotation speed is reduced to 120r / min, and the system is allowed to cool slowly. When the system temperature drops to 120°C, the solid superacid catalyst is filtered while hot and recovered.

[0049] (5) After filtering and recovering the catalyst, the filtrate was cooled to 80°C. 40g of No. 5 white oil was added to the system, the stirring speed was adjusted to 400r / min, and the mixture was stirred and homogenized at 80°C for 60min to form a uniform and stable dispersion system. After homogenization, the system was allowed to cool naturally to room temperature and filtered using a filter membrane with a pore size of 0.45μm to obtain a uniform-looking and stable modified fatty acid oil-based drilling fluid wetting agent resistant to 260°C ultra-high temperature.

[0050] The infrared spectrum of the modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperature (260℃) prepared in this embodiment is shown below. Figure 1 As shown, by Figure 1 It can be known that 1734cm -1 The strong absorption peak is attributed to the stretching vibration of the ester group (C=O), at 1710 cm⁻¹. -1 There are no characteristic absorptions of carboxyl groups nearby, indicating that the carboxyl groups in the raw materials, castor oil acid and oleic acid, have been completely esterified. 1240cm -1 and 1093cm -1 The absorption bands correspond to the asymmetric stretching of the ester bond (COC) and the CO stretching vibration of the ether bond / secondary alcohol, respectively. 3365 cm⁻¹ -1 The broad and strong absorption peak at 910 cm⁻¹ belongs to hydrogen-bonded hydroxyl groups (OH), which originate from the original hydroxyl groups in castor oil and the newly generated hydroxyl groups from the ring-opening reaction of epoxidized soybean oil. -1 There is no absorption at this site; the epoxy groups are completely open, and all epoxidized soybean oil participates in the grafting reaction. 1600cm -1 and 800cm -1 The weak to moderately strong absorption peaks are attributed to aromatic ring skeletal vibrations (C=C) and out-of-plane bending vibrations (CH), indicating that the biphenyl structure has been introduced into the product. (2925 cm⁻¹) -1 and 2855cm -1 The strong peak is due to the symmetric and asymmetric stretching vibrations of the methylene group (-CH2-), at 1456 cm⁻¹. -1 The product retains a long-chain alkyl skeleton due to methylene bending vibration. Infrared spectroscopy results confirmed that each step of the reaction, including transesterification modification, epoxidized soybean oil ring-opening grafting, pentaerythritol esterification crosslinking, and biphenyl modification, proceeded as expected, successfully preparing a high-temperature resistant modified fatty acid oil-based drilling fluid wetting agent containing ester groups, hydroxyl groups, ether bonds, and aromatic ring structures.

[0051] Example 2

[0052] A method for preparing a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃ includes the following steps:

[0053] (1) Add 60g of ricinoleic acid and 40g of linoleic acid to a dried four-necked flask, start stirring at 350r / min, and purge with nitrogen for 10min to purge the air; then raise the temperature to 120℃ and dehydrate under nitrogen atmosphere for 1h until no water is discharged from the water separator; while maintaining nitrogen and stirring, add 3g of solid superacid catalyst SO4. 2- / ZrO2, continue heating to 170℃, slowly add 15g of trimethylolpropane to the system, control the addition time to 20min, after the addition is complete, under nitrogen protection, carry out the transesterification modification reaction at 170℃ for 3h, the water generated in the reaction is continuously discharged through a water separator; after the reaction is completed, cool down to 100℃, filter while hot to recover the catalyst, and obtain ricinoleic acid modified fatty acid with multiple hydroxyl active sites, which is the basic raw material modified fatty acid used for subsequent synthesis of wetting agent.

[0054] (2) Add 100g of modified fatty acid to a dried four-necked reaction flask, turn on the stirrer, adjust the speed to 350r / min, and simultaneously purge nitrogen for 10min to purge the air; turn on the heating device and gradually raise the temperature to 120℃, and dehydrate at a constant temperature under a nitrogen atmosphere for 2h until no obvious water is separated from the water separator, ensuring that the system is in an anhydrous environment; after dehydration is completed, continue to purge nitrogen and maintain a stirring rate of 350r / min, and add 2.5g of solid superacid catalyst SO4 to the system. 2- / ZrO2, continue heating to 150℃, stir at constant temperature for 30 min to ensure the catalyst is uniformly dispersed in the raw materials; keep the system temperature stable at 150℃, slowly add 18g of phenyl glycidyl ether through a constant pressure dropping funnel, control the dropping rate to 1mL / min to avoid excessive local concentration leading to side reactions; after the addition is complete, heat to 165℃, and carry out the ring-opening grafting reaction at constant temperature of 165℃ for 3 h under nitrogen atmosphere;

[0055] (3) After the grafting reaction is completed, the system temperature is gradually raised to 190℃ at a rate of 5℃ / min. 12g of sorbitol is added to the system and the esterification crosslinking reaction is carried out at a constant temperature of 190℃ for 4h under a nitrogen atmosphere. The trace amount of water generated during the reaction is discharged in time through a water separator to promote the forward reaction.

[0056] (4) After the crosslinking reaction is completed, the system is heated to 220°C, and 5g of diphenyl ether and 5g of 1-phenylnaphthalene are added to the system. The system is stirred and aged at a constant temperature for 2 hours under a nitrogen atmosphere. After the aging reaction is completed, the heating is stopped, nitrogen protection is maintained and the rotation speed is reduced to 120r / min, and the system is allowed to cool slowly. When the system temperature drops to 120°C, the solid superacid catalyst is filtered while hot and recovered.

[0057] (5) After filtering and recovering the catalyst, the filtrate was cooled to 80°C. 50g of No. 5 white oil was added to the system, the stirring speed was adjusted to 400r / min, and the mixture was stirred and homogenized at 80°C for 60min to form a uniform and stable dispersion system. After homogenization, the system was allowed to cool naturally to room temperature and filtered using a filter membrane with a pore size of 0.45μm to obtain a uniform-looking and stable modified fatty acid oil-based drilling fluid wetting agent resistant to 260°C ultra-high temperature.

[0058] Example 3

[0059] A method for preparing a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃ includes the following steps:

[0060] (1) Add 50g of ricinoleic acid, 30g of stearic acid and 20g of palmitic acid to a dried four-necked flask, turn on the stirring speed to 350r / min, and purge the air with nitrogen for 10min; then raise the temperature to 120℃ and dehydrate under nitrogen atmosphere for 1h until no water is discharged from the water separator; while maintaining nitrogen and stirring, add 3g of solid superacid catalyst SO4. 2- / ZrO2, continue heating to 170℃, slowly add 15g pentaerythritol to the system, control the addition time to 20min, after the addition is complete, under nitrogen protection, carry out the transesterification modification reaction at 170℃ for 3h, the water generated in the reaction is continuously discharged through a water separator; after the reaction is completed, cool down to 100℃, filter while hot to recover the catalyst, and obtain ricinoleic acid modified fatty acid with multiple hydroxyl active sites, which is the basic raw material modified fatty acid used for subsequent synthesis of wetting agent.

[0061] (2) Add 100g of modified fatty acid to a dried four-necked reaction flask, turn on the stirrer, adjust the speed to 350r / min, and simultaneously purge nitrogen for 10min to purge the air; turn on the heating device and gradually raise the temperature to 120℃, and dehydrate at a constant temperature under a nitrogen atmosphere for 2h until no obvious water is separated from the water separator, ensuring that the system is in an anhydrous environment; after dehydration is completed, continue to purge nitrogen and maintain a stirring rate of 350r / min, and add 3g of solid superacid catalyst SO4 to the system. 2- / ZrO2, continue heating to 150℃, stir at constant temperature for 30 min to ensure the catalyst is uniformly dispersed in the raw materials; keep the system temperature stable at 150℃, slowly add 11g glycidyl methacrylate and 11g epoxidized soybean oil through a constant pressure dropping funnel, controlling the dropping rate to 1mL / min to avoid excessive local concentration leading to side reactions; after the addition is complete, heat to 165℃, and carry out the ring-opening grafting reaction at constant temperature of 165℃ for 3 h under nitrogen atmosphere;

[0062] (3) After the grafting reaction is completed, the system temperature is gradually raised to 190℃ at a rate of 5℃ / min. 8g of trimethylolpropane is added to the system and the esterification crosslinking reaction is carried out at a constant temperature of 190℃ for 4h under a nitrogen atmosphere. The trace amount of water generated during the reaction is discharged in time through a water separator to promote the forward reaction.

[0063] (4) After the crosslinking reaction is completed, the system is heated to 220°C, 10g of dibenzyltoluene is added to the system, and the mixture is stirred and aged at a constant temperature for 2 hours under a nitrogen atmosphere. After the aging reaction is completed, the heating is stopped, nitrogen protection is maintained and the rotation speed is reduced to 120r / min, and the system is allowed to cool slowly. When the system temperature drops to 120°C, the solid superacid catalyst is filtered while hot and recovered.

[0064] (5) After filtering and recovering the catalyst, the filtrate was cooled to 80°C. 45g of No. 5 white oil was added to the system, the stirring speed was adjusted to 400r / min, and the mixture was stirred and homogenized at 80°C for 60min to form a uniform and stable dispersion system. After homogenization, the system was allowed to cool naturally to room temperature and filtered using a filter membrane with a pore size of 0.45μm to obtain a uniform-looking and stable modified fatty acid oil-based drilling fluid wetting agent resistant to 260°C ultra-high temperature.

[0065] Comparative Example 1

[0066] A method for preparing an oil-based drilling fluid wetting agent includes the following steps:

[0067] (1) The preparation of modified fatty acids is the same as step (1) in Example 1;

[0068] (2) Add 100g of modified fatty acid to a dried four-necked reaction flask, turn on the stirrer, adjust the speed to 350r / min, and simultaneously purge nitrogen for 10min to purge the air; turn on the heating device and gradually raise the temperature to 120℃, and dehydrate at a constant temperature under a nitrogen atmosphere for 2h until no obvious water is separated from the water separator, ensuring that the system is in an anhydrous environment; after dehydration is completed, continue to purge nitrogen and maintain a stirring rate of 350r / min, and add 2g of solid superacid catalyst SO4 to the system. 2- / ZrO2, continue heating to 150℃, stir at constant temperature for 30 min to ensure the catalyst is uniformly dispersed in the raw materials; then gradually raise the system temperature to 190℃ at a rate of 5℃ / min, add 10g pentaerythritol to the system, and maintain the esterification and crosslinking reaction at 190℃ for 4 h under a nitrogen atmosphere. The trace amounts of water generated during the reaction are promptly discharged through a water separator to promote the forward reaction;

[0069] (3) After the cross-linking reaction is completed, the system is heated to 220°C, 8g of biphenyl is added to the system, and the mixture is stirred and kept at a constant temperature for 2 hours under a nitrogen atmosphere. After the maturation is completed, the heating is stopped, nitrogen protection is maintained and the rotation speed is reduced to 120r / min, and the system is allowed to cool slowly. When the system temperature drops to 120°C, the solid superacid catalyst is filtered while hot and recovered.

[0070] (4) After filtering and recovering the catalyst, the filtrate is cooled to 80°C. 40g of No. 5 white oil is added to the system, the stirring speed is adjusted to 400r / min, and the mixture is stirred and homogenized at 80°C for 60min to form a uniform and stable dispersion system. After homogenization, the system is allowed to cool naturally to room temperature and filtered using a filter membrane with a pore size of 0.45μm to obtain an oil-based drilling fluid wetting agent.

[0071] Comparative Example 2

[0072] A method for preparing an oil-based drilling fluid wetting agent is as described in Example 1, except that: no high-temperature stabilizing agent is added, that is: after the crosslinking reaction in step (4) is completed, heating is stopped, nitrogen protection is maintained and the rotation speed is reduced to 120 r / min, and the system is allowed to cool slowly. When the system temperature drops to 120°C, the system is filtered while hot and the catalyst is recovered. The remaining steps are the same as in Example 1.

[0073] Comparative Example 3

[0074] A method for preparing an oil-based drilling fluid wetting agent is as described in Example 1, except that: no polyhydroxy compound is added, that is: after the grafting reaction is completed, no cross-linking reaction is carried out, the system temperature is directly increased to 220°C, 8g of biphenyl is added to the system, and the remaining steps are the same as in Example 1.

[0075] Comparative Example 4

[0076] A method for preparing an oil-based drilling fluid wetting agent is as described in Example 1, except that in step (1), the solid superacid catalyst SO4 is used. 2- / ZrO2 was replaced with an equal mass of concentrated sulfuric acid (98wt%). Since the concentrated sulfuric acid is a liquid, it was added dropwise (at a rate of 2 drops / s) directly into the reaction system before the addition of the polyol. The remaining steps and amounts were the same as in Example 1.

[0077] Comparative Example 5

[0078] A method for preparing an oil-based drilling fluid wetting agent is described in Example 1, except that in step (2), epoxidized soybean oil is replaced with an equal mass of 1,2-epoxyhexane, and the remaining steps and dosages are the same as in Example 1.

[0079] Comparative Example 6

[0080] A method for preparing an oil-based drilling fluid wetting agent is described in Example 1, except that in step (3), pentaerythritol is replaced with an equal mass of ethylene glycol, and the remaining steps and dosages are the same as in Example 1.

[0081] Comparative Example 7

[0082] A method for preparing an oil-based drilling fluid wetting agent is as described in Example 1, except that the amount of epoxidized soybean oil used in step (2) is 5g, and the remaining steps and amounts are the same as in Example 1.

[0083] Comparative Example 8

[0084] A method for preparing an oil-based drilling fluid wetting agent is described in Example 1, except that the amount of pentaerythritol used in step (3) is 25g, and the remaining steps and amounts are the same as in Example 1.

[0085] Comparative Example 9

[0086] A method for preparing an oil-based drilling fluid wetting agent includes the following steps:

[0087] (1) Mix 70g of ricinoleic acid and 30g of oleic acid to obtain a mixture;

[0088] (2) Add 100g of the above mixture to a four-necked reaction flask that has been dried, and then proceed with the same steps (2) to (5) as in Example 1.

[0089] Experimental Example 1

[0090] The performance of the oil-based drilling fluid wetting agents prepared in the examples and comparative examples was evaluated as follows.

[0091] 1. Contact Angle Test

[0092] Standard barite powder (API standard drilling fluid barite, fineness above 200 mesh) was selected as the test substrate. The barite powder was dried in an oven at 105℃ for 4 hours to remove surface adsorbed moisture, and then cooled to room temperature before use.

[0093] Preparation of the solution containing the wetting agent: First, add No. 5 white oil and the wetting agent sample to be tested to the stirring cup, turn on the high-speed stirrer, set the speed to 8000 r / min, and stir at high speed for 20 minutes to obtain the solution containing the wetting agent; the volume ratio of No. 5 white oil to the mass ratio of the wetting agent sample to be tested is 300 mL: 12 g.

[0094] 100g of dried barite powder was weighed and added to 300g of a solution containing a wetting agent. The mixture was stirred at 8000 rpm for 30 minutes using a high-speed stirrer to ensure the barite powder was fully wetted and dispersed. The wetted barite powder was then separated using a centrifuge, washed three times with anhydrous ethanol to remove residual white oil, and subsequently dried to constant weight in a 60℃ vacuum oven. Approximately 7.0g of the dried barite powder was pressed into smooth, flat discs with a diameter of 13mm under 10MPa pressure (pressing time 10min) to obtain barite substrate sheets for testing. The static contact angle of a water droplet on the barite surface was measured using a contact angle meter (titration method). Measurements were taken at at least five different locations on each sample, and the average value was recorded.

[0095] Similarly, 100g of dried barite powder was weighed and added to 300g of a solution containing a wetting agent. The mixture was stirred for 30 minutes at 8000 rpm using a high-speed stirrer to ensure the barite powder was fully wetted and dispersed. Afterward, it was rolled and aged at 260℃ for 16 hours. Following cooling, the mixture was centrifuged, tableted, and the contact angle was measured. The changes in the contact angle before and after aging were compared to evaluate the wetting retention ability of the wetting agent after high-temperature aging. The average contact angle (°) of water droplets on the barite tablet surface was recorded. A larger contact angle indicates a higher degree of wetting reversal from hydrophilic to lipophilic on the barite surface, and better wetting reversal performance of the wetting agent. The test results are shown in Table 1.

[0096] Table 1 Contact angle test before and after aging

[0097]

[0098] As shown in Table 1, the wetting agents prepared in Examples 1-3 of this invention had contact angles of 108.2°, 105.8°, and 106.5° before aging, exhibiting high oil-to-wet conversion ability. After aging at 260°C for 16 hours, the contact angles were 102.6°, 99.9°, and 100.2°, still remaining above 99°, indicating stable interfacial wetting performance under ultra-high temperature conditions. Ring-opening grafting of epoxy groups introduces stable ether bonds into the fatty acid backbone, increasing molecular weight and chain rigidity. Esterification crosslinking with polyhydroxy crosslinking agents constructs a three-dimensional network, enhancing molecular thermal stability. The addition of aromatic high-temperature stabilizing agents forms a stable configuration containing rigid aromatic rings, significantly enhancing resistance to thermo-oxidative degradation. Comparative Example 1 did not undergo epoxy ring-opening grafting modification, resulting in a lack of molecular weight enhancement and rigidity-enhancing structures, making it prone to molecular chain breakage under high-temperature conditions and significantly reducing interfacial adsorption capacity. Comparative Example 2 lacked a high-temperature stabilizing agent, resulting in a lack of aromatic rigid structures for enhanced thermal stability. During high-temperature aging, it was prone to thermal oxidative degradation, leading to a decrease in contact angle and significantly insufficient stability. Comparative Example 3 lacked a polyhydroxy crosslinking step, failing to form a stable three-dimensional network structure. At high temperatures, the structure was prone to rearrangement or decomposition, resulting in a decrease in contact angle. Comparative Example 4 used concentrated sulfuric acid instead of a solid superacid catalyst. The catalyst could not be recovered and easily triggered side reactions, resulting in poor molecular structure uniformity and insufficient thermal stability, leading to a decrease in contact angle after aging at 260℃. Comparative Example 5 used hexane oxide instead of epoxidized soybean oil for ring-opening grafting, failing to effectively improve molecular weight and steric hindrance effect. At high temperatures, the adsorbed layer was prone to desorption, leading to a decrease in contact angle. Comparative Example 6 used ethylene glycol instead of pentaerythritol for crosslinking. The low hydroxyl functionality prevented the construction of a stable three-dimensional network structure, resulting in insufficient interfacial adsorption film strength and a slight decrease in contact angle. In Comparative Example 7, the amount of epoxy grafting reagent was too low, resulting in insufficient molecular modification and limited chain growth. At high temperatures, the molecular structure was prone to relaxation and failure, leading to a significant decrease in contact angle. In Comparative Example 8, the excessive amount of polyhydroxy crosslinking agent led to over-crosslinking, resulting in decreased molecular dispersibility in the oil phase, affecting the orderly arrangement of the interface and adsorption efficiency, and causing a decrease in the contact angle. In Comparative Example 9, the transesterification modification step was omitted, and a mixture of fatty acids was used directly. The molecular skeleton lacked active sites and an ideal lipophilic structure, resulting in insufficient subsequent reaction, poor thermal stability, and a significant decrease in the contact angle.

[0099] 2. Settlement stability test

[0100] First, add 255 mL of No. 5 white oil to the mixing cup, turn on the high-speed mixer, and set the speed to 8000 r / min. Then, add 15 g of primary emulsifier (BSRH-2), 3 g of secondary emulsifier (SHALEMUL®S), and 12 g of the wetting agent sample to be tested, and continue high-speed mixing for 20 minutes. Next, add 45 mL of 20 wt% CaCl2 aqueous solution and mix at high speed for 20 minutes to form a homogeneous emulsion system. Subsequently, add 6 g of organic clay, 15 g of calcium oxide, and 12 g of oxidized asphalt, mixing for 10 minutes after each addition before adding the next. Finally, add barite to ensure the drilling fluid density is 2.0 g / cm³. 3 Continue high-speed stirring for 30 minutes to ensure complete dispersion of barite and homogeneity of the system, obtaining drilling fluid. Prepare multiple drilling fluid samples according to the above steps for room temperature settling observation and high-temperature aging test, respectively. For room temperature settling, pour the prepared drilling fluid into a 250mL stoppered graduated cylinder to full volume (250mL). Tighten the stopper and allow it to stand vertically at room temperature for 48 hours. After 48 hours, observe and record the volume (mL) of the upper precipitated liquid (or clear oil), whether there is sediment at the bottom, and measure the density difference between the upper and lower parts. For the high-temperature aging test, after loading the prepared drilling fluid into a high-temperature aging tank, place the aging tank into a drum heater and continuously roll and age it at 260℃ for 16 hours. After aging and cooling to room temperature, the aged drilling fluid was poured into a clean 250mL stoppered graduated cylinder to full volume (250mL). The stopper was tightened, and the graduated cylinder was placed vertically at room temperature for 48 hours. After 48 hours, the volume of the upper liquid precipitated, whether there was any sediment at the bottom, and the density difference between the upper and lower layers were carefully observed and recorded. The test results are shown in Table 2.

[0101] Table 2 Settlement stability test results

[0102]

[0103] As shown in Table 2, the volumes of the upper liquid precipitated in Examples 1-3 of this invention were 1.8 mL, 2.4 mL, and 3.1 mL, respectively, with all precipitates less than 3.5 mL. No precipitate appeared at the bottom during the test, and the density difference Δρ between the upper and lower layers was 0.02 g / cm³. 3 0.03g / cm 3 and 0.03g / cm 3 The density difference is very small, the system stratification is not obvious, no bottom sedimentation occurs after aging, and the density difference Δρ between the upper and lower parts after aging is less than 0.09 g / cm³.

[0104] Comparative Example 1, lacking epoxy ring-opening grafting modification, had short molecular chains, insufficient steric hindrance, poor adsorption layer stability, and easy particle aggregation upon standing, resulting in a significant density difference before and after aging. Comparative Example 2, without the addition of a high-temperature stabilizing agent, lacked an aromatic stabilizing structure, making the molecules prone to degradation at high temperatures and reducing dispersion stability. Comparative Example 3, lacking polyhydroxy crosslinking, failed to form a three-dimensional network, resulting in insufficient steric support, easy particle sedimentation, and significant differences in volume and density of the precipitate before and after aging. Comparative Example 4, using concentrated sulfuric acid instead of a solid superacid catalyst, increased side reactions, resulting in impure products, reduced effective components, and the potential for acid residue to trigger high-temperature side reactions, deteriorating wetting properties. Comparative Example 5, using small-molecule 1,2-epoxyhexane instead of epoxidized soybean oil ring-opening grafting, had excessively short lipophilic segments, insufficient steric hindrance, and weak adsorption capacity. Comparative Example 6, using difunctional ethylene glycol instead of tetrafunctional pentaerythritol crosslinking, only formed linear branches, failing to construct a three-dimensional network framework, resulting in insufficient adsorption strength and high-temperature stability. Comparative Example 7: Insufficient epoxidized soybean oil resulted in a lack of polar anchoring groups and lipophilic segments, preventing the formation of a dense adsorption layer. While exhibiting some stability before aging, defects in the adsorption layer were exposed after high-temperature aging, leading to a significant increase in the volume of the precipitated liquid. Comparative Example 8: Excessive pentaerythritol resulted in excessive cross-linking, with some products forming large networks or gels. This led to poor dispersibility in the oil phase, and during high-temperature aging, the excessively cross-linked components aggregated, causing system instability and an increase in the volume of the precipitated liquid. Comparative Example 9: Omitted the first step of fatty acid modification, directly using mixed fatty acids as raw materials. Lacking the polyhydroxy active sites introduced by the reaction of ricinoleic acid with polyols, subsequent ring-opening grafting and cross-linking could not proceed effectively, resulting in severe sedimentation before aging and performance failure after aging.

[0105] The above demonstrates that the wetting agent prepared in the embodiments of the present invention exhibits good dispersion stability and anti-settling ability in oil-based drilling fluid systems. This is because ring-opening grafting of epoxy groups increases the molecular weight and molecular chain flexibility, resulting in a stronger steric hindrance effect in the oil phase, inhibiting particle aggregation and reducing the sedimentation tendency. The polyhydroxy crosslinking reaction forms a certain degree of spatial network structure, improving the system's viscoelasticity and structural integrity, thereby enhancing its suspension support for weighting materials and solid particles, preventing rapid sedimentation of particles under static or high-temperature conditions. Adding an aromatic high-temperature stabilizing agent at 220°C and aging it further stabilizes the system's molecular configuration, enhances intermolecular forces, and improves the overall structural stability of the system. This step helps maintain the dispersion state of the wetting agent in the oil phase and reduces the system's density difference.

[0106] 3. Comprehensive performance evaluation test of drilling fluid system

[0107] Preparation of the drilling fluid system: First, add 255 mL of No. 5 white oil to the mixing cup, turn on the high-speed mixer, set the speed to 8000 r / min, and then add 15 g of primary emulsifier (BSRH-2), 3 g of secondary emulsifier (SHALEMUL®S), and 12 g of the wetting agent sample to be tested in sequence. Continue to stir at high speed for 20 minutes. Then add 45 mL of 20 wt% CaCl2 aqueous solution and stir at high speed for 20 minutes to form a homogeneous emulsion system. Subsequently, add 6 g of organic clay, 15 g of calcium oxide, and 12 g of oxidized asphalt in sequence, stirring for 10 minutes after each addition before adding the next. Finally, add barite to ensure that the drilling fluid density is 2.0 g / cm³. 3 Then, the rheological parameters of the system were tested at 65°C using a six-speed rotational viscometer. The drilling fluid was then placed in a high-temperature aging tank and aged at 260°C for 16 hours. After aging, the system was cooled to room temperature, and the rheological parameters of the aged drilling fluid were tested. The test results are shown in Table 3.

[0108] Table 3. Drilling fluid properties before and after aging at 260℃ for 16 hours

[0109]

[0110] As shown in Table 3, Examples 1-3 all exhibited good apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) before aging, and their rheological parameters remained stable. After aging at 260℃, AV remained at 48-49 mPa·s, PV remained at 43-45.5 mPa·s, YP remained at 2.88-5.27 Pa, and the high-temperature and high-pressure filtration loss (FL) was [not specified]. HTHP The concentration should be controlled between 5.8 and 7.2 mL. The epoxy ring-opening grafting reaction extends the molecular chain and introduces polar anchoring groups, increasing the molecular weight and enhancing the interfacial film strength, preventing the emulsion structure from being destroyed at high temperatures. The polyhydroxy crosslinking reaction constructs a three-dimensional network structure, improving the system's viscoelasticity and dynamic shear stability, and inhibiting the sedimentation of solid phases such as barite at high temperatures. Aromatic high-temperature stabilizing agents enhance the molecular skeleton's resistance to thermo-oxidative degradation, ensuring the molecular structure remains intact at 260°C, thereby maintaining the rheological stability of the drilling fluid system and reducing filtration loss.

[0111] Comparative Example 1 did not undergo epoxy ring-opening grafting, resulting in ineffective molecular chain elongation. The rigid structure was dominant with insufficient steric hindrance, leading to low interfacial film strength. After aging at 260℃, the molecular chains were prone to thermal breakage, reducing barite coating capacity and damaging the system structure. After aging, AV decreased from 65 mPa·s to 38.5 mPa·s, PV from 62 mPa·s to 37 mPa·s, YP to 1.44 Pa, and HTHP filtration loss reached 13.6 mL. Comparative Example 2 did not include high-temperature stabilizing agents, lacking aromatic stabilizing structures such as biphenyl. The molecules had insufficient thermal stability at 260℃, making them susceptible to thermo-oxidative degradation. After aging, the molecular conformation changed, and the density of the adsorption layer decreased. AV decreased from 63.5 mPa·s to 36 mPa·s, PV from 61 mPa·s to 34 mPa·s, YP was only 1.92 Pa, and HTHP filtration loss increased to 15.2 mL. Comparative Example 3 did not undergo a polyhydroxy crosslinking reaction, thus failing to form a three-dimensional network framework and exhibiting insufficient spatial support. During high-temperature aging, linear molecules easily desorbed from the particle surface, resulting in a significant decrease in the structural strength of the particle structure. After aging, the AV was only 42.5 mPa·s, YP was 1.44 Pa, and the HTHP filtration loss reached 16.0 mL. Comparative Example 4 used concentrated sulfuric acid instead of the solid superacid catalyst SO4. 2- / ZrO2, increased side reactions, impure product structure, reduced effective components, residual acid may catalyze reverse reactions or trigger degradation at high temperatures, and the system structure is severely damaged after aging. AV decreases from 64 mPa·s to 33 mPa·s, PV from 61 mPa·s to 32 mPa·s, YP is only 0.96 Pa, and HTHP filtration loss reaches 17.4 mL. Comparative Example 5, using 1,2-epoxyhexane instead of epoxidized soybean oil for ring-opening grafting, cannot provide sufficient steric stabilization, the molecular anchoring and adsorption capacity on the barite surface is insufficient, and the defects in the adsorption layer are amplified after high-temperature aging, with HTHP filtration loss of 11.2 mL. Comparative Example 6, using difunctional ethylene glycol instead of tetrafunctional pentaerythritol for crosslinking, could only form linear or slightly branched structures, failing to construct an effective three-dimensional network framework. After aging, the adsorption strength of molecules on the particle surface was insufficient, resulting in weak structural support. After aging, AV decreased from 63.5 mPa·s to 45 mPa·s, YP was only 1.92 Pa, and HTHP filtration loss reached 14.0 mL. Comparative Example 7 used too little epoxidized soybean oil, resulting in insufficient polar anchoring groups and lipophilic segments, failing to form a dense and complete adsorption layer on the barite surface. After aging, defects in the adsorption layer were exposed, the structural strength of the system decreased, YP decreased to 1.92 Pa, and HTHP filtration loss was 10.4 mL. Comparative Example 8 used too much pentaerythritol, resulting in excessively high crosslinking. Some products formed ultra-large network structures or even microgels, leading to poor solubility and dispersibility in the oil phase, affecting the uniform distribution of the wetting agent in the drilling fluid. After aging, YP was only 1.44 Pa, and HTHP filtration loss was 14.8 mL. Comparative Example 9 completely omitted the first step of fatty acid modification and directly used mixed fatty acids as raw materials for subsequent reactions. Lacking the polyhydroxy active sites introduced by the transesterification of ricinoleic acid and polyol, the subsequent ring-opening grafting and cross-linking reactions could not be carried out effectively. After aging, the system structure failed, AV decreased from 60 mPa·s to 30 mPa·s, PV decreased from 57 mPa·s to 29 mPa·s, YP was only 0.96 Pa, and the HTHP filtration loss reached 19.2 mL.

Claims

1. A method for preparing a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃, characterized in that, The steps include the following: (1) Castor oil acid and base fatty acid are mixed, heated and dehydrated, then solid superacid catalyst I is added, and the temperature is raised to the reaction temperature. Polyol is added to carry out the reaction. After the reaction is completed, the temperature is lowered and filtered to obtain modified fatty acid. The base fatty acid is one or more of oleic acid, linoleic acid, stearic acid, and palmitic acid. The mass ratio of castor oil acid to base fatty acid is 1-3:

1. The solid superacid catalyst I is SO4. 2- / ZrO2、SO4 2- / TiO2、WO3 / ZrO2、SO4 2- One or more of Fe3O4; the polyol is one of glycerol, pentaerythritol, and trimethylolpropane, and the mass ratio of the polyol to ricinoleic acid is 0.1-0.4:1; (2) After dehydrating the modified fatty acid obtained in step (1), add solid superacid catalyst II, stir evenly, and then add a grafting reagent containing epoxy groups to carry out a ring-opening grafting reaction; then add a polyhydroxy compound to carry out an esterification crosslinking reaction; the solid superacid catalyst II is the same as the solid superacid catalyst I in step (1); the grafting reagent containing epoxy groups is one or more of epoxidized soybean oil, phenyl glycidyl ether, glycidyl methacrylate, and glycidyl trimethylammonium chloride, and the mass ratio of the grafting reagent containing epoxy groups to the modified fatty acid is 0.15-0.25:1; the polyhydroxy compound is one or more of pentaerythritol, trimethylolpropane, xylitol, and sorbitol, and the mass ratio of the polyhydroxy compound to the modified fatty acid is 0.05-0.15:1; (3) After the esterification and crosslinking reaction is completed, a high-temperature stabilizing agent is added to the resulting reaction solution for aging treatment; then hot filtration is performed, and after the resulting filtrate is cooled, an oil phase dispersion medium is added and stirred evenly to obtain a modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperature of 260℃; the high-temperature stabilizing agent is one or more of biphenyl, 1-phenylnaphthalene, 2-phenylnaphthalene, diphenyl ether, dibenzyltoluene, and monobenzyltoluene, and the mass ratio of the high-temperature stabilizing agent to the modified fatty acid is 0.05-0.15:1; the oil phase dispersion medium is one or more of mineral oil, synthetic oil, and white oil, and the mass ratio of the oil phase dispersion medium to the modified fatty acid is 0.4-0.5:

1.

2. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The temperature of the heating and dehydration treatment in step (1) is 110-130℃, and the time of the heating and dehydration treatment is 0.5-2h; the heating and dehydration treatment is carried out under a nitrogen atmosphere.

3. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The mass of the solid superacid catalyst I mentioned in step (1) is 1-5% of the total mass of ricinoleic acid and the base fatty acid; The reaction temperature is 160-180℃, the reaction time is 2-4 hours, the reaction is carried out under a nitrogen atmosphere, and the cooling is performed to 90-100℃ followed by thermal filtration.

4. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The temperature of the dehydration treatment in step (2) is 110-130℃, and the time of the dehydration treatment is 1-3h; The mass of the solid superacid catalyst II is 1-4% of the mass of the modified fatty acid; After adding solid superacid catalyst II, the stirring temperature is 145-155℃, the stirring time is 20-40 min, and the stirring speed is 200-500 r / min.

5. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The grafting reagent containing epoxy groups described in step (2) is added dropwise to the system at a rate of 1-2 mL / min and a temperature of 145-155 °C. The ring-opening grafting reaction is carried out at a temperature of 160-175℃ for 2-4 hours.

6. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The temperature of the esterification crosslinking reaction in step (2) is 180-200℃, and the time of the esterification crosslinking reaction is 3-5h; the operation process in step (2) is carried out under a nitrogen atmosphere.

7. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The aging process in step (3) is carried out at a temperature of 210-230℃ and for a time of 1-3 hours. The aging process is conducted under nitrogen protection.

8. The preparation method of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 1, characterized in that, The hot filtration step in step (3) is as follows: the reaction solution after aging is cooled to 110-120℃ and then filtered; In step (3), the obtained filtrate is cooled to 70-80℃; the white oil is No. 5 white oil, No. 7 white oil or No. 10 white oil; the stirring speed is 300-500 r / min and the stirring time is 50-70 min; In step (3), after stirring is completed, a filtration step is also included, as follows: the mixture obtained by stirring is naturally cooled to room temperature and then filtered. The pore size of the filter membrane used for filtration is ≤0.5μm.

9. A modified fatty acid oil-based drilling fluid wetting agent resistant to ultra-high temperatures of 260℃, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The application of the 260℃ ultra-high temperature resistant modified fatty acid oil-based drilling fluid wetting agent according to claim 9 in oil-based drilling fluids.

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