Resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid and preparation method and application thereof

Abstract

The application provides a resin-coated inorganic fiber / aerogel composite thermal insulation material for a water-based drilling fluid and a preparation method and application thereof. The preparation method of the thermal insulation material comprises the following steps: preparing a cationic polyamine complex crosslinking agent by using triethylenetetramine, 2-hydroxyethylamine and 3-chloro-2-hydroxypropyl-trimethylammonium chloride as raw materials; adding melamine formaldehyde resin and phenolic resin into ethanol, adding the crosslinking agent, stirring uniformly to obtain a mixed solution A; adding aerogel into ethylene glycol, stirring uniformly, then adding inorganic fibers, stirring uniformly to obtain a mixed solution B; and obtaining by vacuum impregnation, resin coating and surface modification in sequence. The thermal insulation material can participate in the formation of mud cake, form a thermal insulation barrier on the surface of the well wall rock, weaken the heat exchange between the drilling fluid and the formation, and reduce the occurrence of well wall instability caused by thermal strain. In addition, the thermal insulation material containing the inorganic fiber framework can act as a bridging agent to reduce the filtration loss of the drilling fluid.

Description

Technical Field

[0001] This invention relates to a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids, its preparation method and application, belonging to the field of drilling fluid chemistry in the petroleum industry. Background Technology

[0002] As the development of oil and gas resources in my country's eastern continental basins enters its middle and late stages, the proven oil and gas exploration rates in the Songliao, Bohai Bay, and Ordos basins have reached 70%, 53%, and 50%, respectively, making the opportunities to discover rich oil and gas fields in shallow and medium-depth formations increasingly rare. In the past decade, over 60% of the world's newly proven oil and gas reserves have come from deep strata exceeding 4500 meters. my country's total deep and ultra-deep oil and gas resources amount to 67.1 billion tons of oil equivalent, accounting for 34% of my country's total oil and gas resources. Distributed across six major basins, with a proven exploration rate of only 17%, these basins are the main battleground for increasing oil and gas reserves and production.

[0003] Deep and ultra-deep formations present complex geological conditions, with multiple harsh conditions such as ultra-high temperature, ultra-high pressure, ultra-high salinity, and well-developed fractures, posing unprecedented challenges to drilling operations. Drilling fluid is crucial for ensuring safe and efficient drilling of deep and ultra-deep oil and gas formations. Controlling drilling fluid in harsh formations is extremely difficult; improper control can easily lead to well collapse, lost circulation, blowouts, and even catastrophic accidents resulting in well destruction and loss of life. During deep and ultra-deep drilling operations, the formation temperature is usually higher than the drilling fluid temperature. This temperature difference between the drilling fluid and the formation causes changes in the near-wellbore formation temperature. This non-isothermal characteristic inevitably affects the stability of the wellbore. The cooling effect of the drilling fluid on the wellbore rock generates additional tensile thermal stress, inducing the formation of microcracks and the propagation of existing fractures. On the one hand, this leads to drilling fluid intrusion along the pore fractures, increasing pore pressure and reducing the drilling fluid's support for the wellbore; on the other hand, it reduces rock strength, thus increasing the risk of wellbore instability. In addition, the rapid rise in drilling fluid temperature due to the heat absorption of drilling fluid makes other drilling fluid additives prone to high-temperature failure, thereby affecting wellbore stability.

[0004] Chinese patent document CN116063996A discloses a phase change thermal storage microcapsule material suitable for drilling fluid cooling, its preparation method, and its application. The phase change thermal storage microcapsule material of this invention consists of a polymer wall material encapsulating the outer layer, a phase change thermal storage material as the core material, and nano-graphite doped within it. The overall size of the microcapsules is in the range of 20-80 μm. When the drilling fluid reaches its phase change temperature, the internal phase change thermal storage material undergoes a phase change and absorbs heat, reducing the temperature rise of the drilling fluid. The addition of nano-graphite improves the overall thermal conductivity and enhances the latent heat of phase change. Chinese patent document CN109652028A introduces a drilling fluid temperature control method based on phase change materials, including the following steps: (1) selecting a phase change material for the drilling fluid; (2) using the phase change material as a drilling fluid treatment agent; (3) after drilling is completed, the phase change material can be recycled and reused. The beneficial effects are: during drilling fluid circulation, phase change materials can continuously absorb and release appropriate amounts of heat energy; phase change materials can be used simultaneously with other drilling fluid treatment agents; maintenance-free; no power consumption, environmentally friendly; and competitive in economic benefits. In the two patents mentioned above, the phase change materials can indeed absorb heat from the formation, lower the drilling fluid temperature, and mitigate the failure of drilling fluid treatment agents at high temperatures. However, the main cooling principle of phase change materials is "latent heat of phase change," which cannot effectively reduce heat transfer between the drilling fluid and the formation, i.e., it cannot effectively provide insulation.

[0005] Therefore, the preparation of heat-insulating materials for high-temperature drilling fluids is crucial. This invention is proposed for this purpose. Summary of the Invention

[0006] To address the shortcomings of existing technologies, particularly the problem of wellbore instability caused by drilling fluid circulation cooling the wellbore rock during deep and ultra-deep formation drilling, this invention provides a water-based drilling fluid resin-coated inorganic fiber / aerogel composite thermal insulation material, its preparation method, and its application. This invention uses a self-made cationic polyamine as a composite crosslinking agent and prepares a water-based drilling fluid resin-coated inorganic fiber and aerogel composite thermal insulation material through vacuum impregnation and resin coating methods. This thermal insulation material can participate in mud cake formation, forming a thermal barrier on the wellbore rock surface, thereby reducing heat exchange between the drilling fluid and the formation and decreasing wellbore instability caused by thermal strain. Furthermore, the thermal insulation material containing the inorganic fiber skeleton can act as a bridging agent, reducing drilling fluid filtration loss.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids includes the following steps:

[0009] (1) Triethylenetetramine and 2-hydroxyethylamine were added to a solvent, followed by the addition of 3-chloro-2-hydroxypropyl-trimethylammonium chloride. The pH of the system was adjusted to 8-9, and the mixture was heated to the reaction temperature. After purging with nitrogen to remove oxygen, the reaction was carried out. After the reaction was completed, the solvent was removed to obtain a cationic polyamine composite crosslinking agent.

[0010] (2) Add melamine-formaldehyde resin and phenolic resin to ethanol, stir evenly, add the cationic polyamine composite crosslinking agent obtained in step (1), stir evenly, and obtain mixture A.

[0011] (3) Add the aerogel to ethylene glycol, stir evenly, then add inorganic fiber, stir evenly to obtain mixture B;

[0012] (4) Add the mixture A obtained in step (2) to the mixture B obtained in step (3) and perform vacuum impregnation to obtain mixture C; then evaporate the ethanol in the mixture C to remove it and heat it to solidify; then centrifuge, wash, dry and grind to obtain intermediate product; place the obtained intermediate product in an aqueous solution of cationic surfactant, mix it evenly and dry it to obtain water-based drilling fluid resin-coated inorganic fiber / aerogel composite thermal insulation material.

[0013] According to a preferred embodiment of the present invention, the solvent in step (1) is a mixed solvent of water and ethanol, wherein the mass ratio of water to ethanol in the mixed solvent is 1:2-4; and the mass ratio of the solvent to 3-chloro-2-hydroxypropyl-trimethylammonium chloride is 5-15:1.

[0014] According to a preferred embodiment of the present invention, the mass ratio of triethylenetetramine to 3-chloro-2-hydroxypropyl-trimethylammonium chloride in step (1) is 1-2:1; and the mass ratio of 2-hydroxyethylamine to 3-chloro-2-hydroxypropyl-trimethylammonium chloride is 0.5-1:1.

[0015] According to a preferred embodiment of the present invention, in step (1), the pH of the system is adjusted using a NaOH aqueous solution with a mass fraction of 10-30%; the time for nitrogen deoxygenation is 20-30 min.

[0016] According to a preferred embodiment of the present invention, the reaction temperature in step (1) is 45-55°C and the reaction time is 3-5 hours.

[0017] According to the present invention, there are no restrictions on the types of melamine-formaldehyde resin and phenolic resin mentioned in step (2), and ordinary commercially available products are acceptable.

[0018] According to a preferred embodiment of the present invention, the mass ratio of melamine-formaldehyde resin to phenolic resin in step (2) is 0.1-0.3:1, and more preferably 0.2:1.

[0019] According to a preferred embodiment of the present invention, the mass ratio of ethanol to phenolic resin in step (2) is 2-4:1, and more preferably 3:1.

[0020] According to a preferred embodiment of the present invention, the ratio of the total mass of melamine-formaldehyde resin, phenolic resin and ethanol to the mass of cationic polyamine composite crosslinking agent in step (2) is 1:0.01-0.05.

[0021] According to a preferred embodiment of the present invention, the aerogel in step (3) is a hydrophobic SiO2 aerogel particle with a particle size of 20-50 nm, which is a commercially available product.

[0022] According to a preferred embodiment of the present invention, the mass ratio of ethylene glycol to aerogel in step (3) is 20-80:1, and more preferably 30-65:1.

[0023] According to a preferred embodiment of the present invention, the inorganic fiber in step (3) is two of the following: aluminum silicate fiber, sepiolite fiber, and ceramic fiber. The length of the inorganic fiber is 20-40 μm and the diameter is 1-5 μm. The mass ratio of the inorganic fiber to the aerogel is 3-12:1, and more preferably 4-6:1.

[0024] According to a preferred embodiment of the present invention, the ratio of the total mass of melamine-formaldehyde resin and phenolic resin in mixture A to the mass of aerogel in mixture B in step (4) is 1-4:1.

[0025] According to a preferred embodiment of the present invention, the vacuum degree of vacuum impregnation in step (4) is 0.05-0.07 MPa, and the vacuum impregnation time is 20-30 h.

[0026] According to a preferred embodiment of the present invention, the step of evaporating and removing ethanol in step (4) is as follows: heating the mixture C to 85-95°C and evaporating and removing ethanol.

[0027] According to a preferred embodiment of the present invention, the curing step in step (4) is as follows: the product obtained by removing ethanol is heated to 120°C and cured for 3 hours, and then the temperature is further increased to 150°C and cured for 1 hour.

[0028] According to a preferred embodiment of the present invention, the washing in step (4) is to use ethanol for centrifugal washing 3-5 times.

[0029] According to a preferred embodiment of the present invention, the cationic surfactant in step (4) is one of hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium chloride, and more preferably hexadecyltrimethylammonium chloride; the mass fraction of the cationic surfactant aqueous solution is 20%; and the mass ratio of the cationic surfactant aqueous solution to the intermediate product is 0.01-0.05:1.

[0030] According to a preferred embodiment of the present invention, in step (4), the intermediate product and the aqueous solution of the cationic surfactant are mixed evenly in a colloid mill.

[0031] According to a preferred embodiment of the present invention, the drying process in step (4) is carried out at 60-90°C until constant weight.

[0032] The present invention also provides a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid, which is prepared by the above-described preparation method.

[0033] According to the present invention, the application of the above-mentioned resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is used to reduce the temperature of water-based drilling fluid.

[0034] The technical features and beneficial effects of this invention are as follows:

[0035] 1. The resin-coated inorganic fiber / aerogel composite thermal insulation material of the present invention exhibits excellent temperature resistance, retaining good thermal insulation performance even after treatment at 220℃. The inorganic fibers and SiO2 aerogel in the thermal insulation material of the present invention possess good thermal stability; furthermore, the overall rigidity and temperature resistance of the cured resin are also enhanced.

[0036] 2. The resin-coated inorganic fiber / aerogel composite thermal insulation material of the present invention exhibits excellent thermal insulation performance, reducing the thermal conductivity of the mud cake by approximately 25%, demonstrating a significant effect. This is because the SiO2 aerogel in the thermal insulation material of the present invention itself has extremely low thermal conductivity; the inorganic fibers contain a large number of nano- and micro-sized pore structures, and the low water affinity of the pore surface can reduce water phase wetting and lower the overall thermal conductivity; in addition, the resin material also has good temperature resistance and thermal insulation properties, thus the overall thermal insulation performance of the material is excellent.

[0037] 3. The resin-coated inorganic fiber / aerogel composite thermal insulation material of the present invention is prepared by using inorganic fiber as a skeleton, aerogel filling, and resin coating. The fiber skeleton can act as a bridging agent to reduce the filtration loss of drilling fluid. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but is not limited thereto.

[0039] Furthermore, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods; and unless otherwise specified, the reagents, materials and equipment are all commercially available.

[0040] The melamine-formaldehyde resin powder used in the examples is available from Shandong Baiqian Chemical Co., Ltd.; the phenolic resin is model phenolic resin 2402, which is available from Shenzhen Yoshida Chemical Co., Ltd.

[0041] The aerogel used is a hydrophobic SiO2 aerogel particle with a particle size of 20-50nm, which is available from Hejian Nalan Energy Saving Technology Co., Ltd.

[0042] Example 1

[0043] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids includes the following steps:

[0044] (1) Preparation of cationic polyamine composite crosslinking agent: 40g of a mixed solvent of water and ethanol (mass ratio of water to ethanol is 1:3), 6g of triethylenetetramine, and 3g of 2-hydroxyethylamine were added to a three-necked flask. The stirring speed was set to 150r / min to ensure that the drugs were fully dissolved. Then, 4g of 3-chloro-2-hydroxypropyl-trimethylammonium chloride was added to the three-necked flask. The pH of the system was adjusted to 9 using a 20% NaOH aqueous solution. The system was heated to 50℃ in a water bath, and nitrogen gas was purged for 20min to remove oxygen. The system was then sealed and reacted for 4h. After the reaction was completed, ethanol and water were removed from the system using a rotary evaporator to obtain the cationic polyamine composite crosslinking agent.

[0045] (2) Add ethanol, melamine-formaldehyde resin and phenolic resin in a mass ratio of 3:0.2:1 to a 100mL beaker. The total mass of ethanol, melamine-formaldehyde resin and phenolic resin is 20g. Stir magnetically for 20min. Then add 0.5g of the cationic polyamine composite crosslinking agent obtained in step (1) and stir for 10min to obtain mixture A. Add 130g of ethylene glycol to a 200mL beaker and add 4g of aerogel to it. Stir for 20min. Then add 20g of inorganic fiber (aluminum silicate fiber and sepiolite fiber mixed in a mass ratio of 0.2:1) to the beaker and stir for 20min to obtain mixture B.

[0046] (3) Stir the mixture B with magnetic force, add the mixture A to it, and then use a vacuum pump to increase the vacuum degree of the system to 0.06 MPa. Stir and vacuum impregnate at room temperature for 24 hours to obtain the mixture C. Transfer the mixture C to a three-necked flask, heat it in an oil bath to 90°C for 1 hour under stirring to evaporate the ethanol in the system. Increase the temperature to 120°C and solidify for 3 hours, and continue to increase the temperature to 150°C and solidify for 1 hour. Cool naturally to room temperature, centrifuge and wash 5 times with ethanol, and dry the solid phase at the bottom of the centrifuge tube at 70°C in a drying oven to constant weight. Grind it through a 200-mesh sieve to obtain the intermediate product.

[0047] (4) Prepare a 20% hexadecyltrimethylammonium chloride aqueous solution. Add the hexadecyltrimethylammonium chloride aqueous solution and the intermediate product to a colloid mill at a mass ratio of 0.03:1. Stir and mix evenly. Dry at 70°C to obtain the water-based drilling fluid resin-coated inorganic fiber / aerogel composite thermal insulation material.

[0048] Example 2

[0049] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is described in Example 1, except that 0.75g of cationic polyamine composite crosslinking agent is added in step (2).

[0050] Example 3

[0051] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is described in Example 1, except that 0.25g of cationic polyamine composite crosslinking agent is added in step (2).

[0052] Example 4

[0053] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is described in Example 1, except that 2g of aerogel is added in step (2).

[0054] Example 5

[0055] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is described in Example 1, except that 15g of inorganic fiber is added in step (2).

[0056] Example 6

[0057] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is described in Example 1, except that the mass ratio of hexadecyltrimethylammonium chloride aqueous solution to intermediate product in step (4) is 0.05:1.

[0058] Example 7

[0059] A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid is as described in Example 1, except that the total mass of ethanol, melamine-formaldehyde resin and phenolic resin in step (2) is 25g.

[0060] Comparative Example 1

[0061] A method for preparing a heat-insulating material for water-based drilling fluid is described in Example 1, except that a cationic composite polyamine crosslinking agent is not added in step (2).

[0062] Comparative Example 2

[0063] A method for preparing a heat-insulating material for water-based drilling fluid is described in Example 1, except that aerogel is not added in step (2).

[0064] Comparative Example 3

[0065] A method for preparing a heat-insulating material for water-based drilling fluid is described in Example 1, except that inorganic fibers are not added in step (2).

[0066] Comparative Example 4

[0067] A method for preparing a water-based drilling fluid insulation material is described in Example 1, except that the surfactant modification in step (4) is not performed, and the resulting intermediate product is the water-based drilling fluid insulation material.

[0068] Comparative Example 5

[0069] A method for preparing a heat-insulating material for water-based drilling fluid is as described in Example 1, except that: in step (3), vacuum impregnation is not performed, and the mixture is stirred at room temperature for 24 hours.

[0070] Test case

[0071] The thermal insulation materials prepared in the examples and comparative examples were evaluated as follows: their effects on drilling fluid rheology and filtration performance, sand bed plugging experiments, and mud cake thermal conductivity tests.

[0072] 1. Impact on drilling fluid rheology and filtration properties

[0073] Preparation of drilling fluid-based slurry: Measure 10,000 mL of clean water and place it in a mixing tank. Under stirring conditions, add 400 g of drilling-grade bentonite and 14 g of Na2CO3. Stir and age at room temperature for 24 hours to obtain 4% drilling fluid-based slurry.

[0074] Rheological and filtration performance evaluation: 400 mL portions of 4% drilling fluid-based slurry were measured, and 2% (8 g) of insulation material was added to each portion to obtain sample slurries. The original 4% base slurry served as a control group. The rheological properties and filtration properties of the base slurry and sample slurries before aging were measured using a six-speed viscometer and a medium-pressure filtration analyzer, respectively. Subsequently, the sample slurries and control groups were added to aging tanks and aged in an aging furnace at 220℃ for 16 h. After cooling to room temperature, the rheological properties and filtration properties of the base slurry and sample slurries before aging were measured using a six-speed viscometer, a medium-pressure filtration analyzer, and a high-temperature, high-pressure filtration analyzer, respectively. The experimental results are shown in Table 1.

[0075] Table 1. Compatibility test results of thermal insulation materials and drilling fluid-based slurries

[0076]

[0077]

[0078] The effects of thermal insulation materials on the rheology and filtration performance of drilling fluid-based slurries are shown in Table 1. Compared to the original slurry rheology and filtration performance before and after aging, the rheological properties of each sample slurry did not change significantly, but the filtration loss decreased to varying degrees, with Example 1 showing the best effect. Compared to Example 1, Example 2 increased the amount of cationic polyamine crosslinking agent, resulting in increased filtration loss before and after aging. This is because the cationic polyamine crosslinking agent affects the dispersion characteristics of clay in the slurry. Example 3 and Comparative Example 1 reduced and did not add cationic polyamine crosslinking agent, respectively, resulting in significantly increased filtration loss before and after aging. This is because reducing the amount of cationic polyamine crosslinking agent affects the crosslinking of the resin, thus affecting the filtration loss reduction effect of the thermal insulation material. Therefore, an appropriate amount of cationic polyamine crosslinking agent helps improve the overall performance of the thermal insulation material. Compared to Example 1, Example 4 and Comparative Example 2 reduced and omitted the addition of hydrophobic aerogel material, respectively. Comparative Example 5 did not undergo vacuum impregnation. The filtration loss before aging did not change significantly, but the filtration loss increased after aging. This is because vacuum impregnation allows the aerogel to enter the skeleton composed of inorganic fibers, and the resin coats the surface of the inorganic fibers, thereby improving the resin's encapsulation of the inorganic fibers and aerogel, enhancing the thermal insulation material's performance and reducing filtration loss. Compared to Example 1, Example 5 and Comparative Example 3 reduced and omitted the addition of inorganic fibers, respectively. The filtration loss of the drilling fluid-based slurry increased both before and after aging. This is because the inorganic fiber skeleton can act as a bridging agent, improving the compactness of the mud cake and enhancing the sealing performance of the drilling fluid. Compared to Example 1, Example 6 increased the amount of surfactant, resulting in certain changes in rheology and increased filtration loss before and after aging. This is because the increased amount of cationic surfactant affects the dispersibility of clay in the base slurry, leading to a certain deterioration in both the rheological and filtration loss characteristics of the base slurry. In contrast, Example 4 did not undergo hydrophilic modification, and the filtration loss before and after aging increased significantly. This is because the thermal insulation material without hydrophilic modification has poor affinity with clay particles in the base slurry, thus affecting the filtration loss reduction of the base slurry. Therefore, selecting an appropriate amount of cationic surfactant to hydrophilically modify the thermal insulation material helps to improve the performance of the thermal insulation material.

[0079] 2. Sand bed sealing experiment

[0080] This experiment uses a visual sand bed sealing device. First, a 350cm diameter was measured. 3 140-160 mesh quartz sand was loaded into a test glass tube, compacted, and leveled. 2% of the insulation material from the examples and comparative examples (i.e., 2g per 100mL of base slurry) was added to a 4% base slurry, and the mixture was placed in an aging tank and aged at 220℃ for 16 hours. The original 4% base slurry served as the control group. The slurry before and after aging, along with the base slurry, were respectively loaded into the test glass tube of the sand bed sealing device. Under 0.7MPa conditions, the penetration depth of the base slurry and the slurry into the sand bed was tested for 15 minutes. The experimental results are shown in Table 2.

[0081] Table 2 Results of Sand Bed Plugging Experiment

[0082] Sample Name Pre-aging sand bed immersion depth / cm Sand bed immersion depth after aging (220℃) / cm base slurry Almost all leaked Almost all leaked 4% base slurry + 2% Example 1 2.4 3.3 4% base slurry + 2% Example 2 2.8 3.8 4% base slurry + 2% Example 3 2.6 3.5 4% base slurry + 2% Example 4 2.5 3.4 4% base slurry + 2% Example 5 2.9 3.9 4% base slurry + 2% Example 6 3.0 4.1 4% base slurry + 2% Example 7 2.6 3.6 4% base slurry + 2% comparative example 1 6.9 9.3 4% base slurry + 2% comparative example 2 5.2 7.7 4% base slurry + 2% comparative example 3 7.7 9.7 4% base slurry + 2% comparative example 4 8.3 9.2 4% base slurry + 2% comparative example 5 4.6 7.1

[0083] The results of the sand bed sealing experiment are shown in Table 2. Compared with the original base slurry before and after aging, the sealing results of all the added slurries decreased, with Example 1 showing the best effect. Compared with Example 1, Example 2 increased the amount of cationic composite polyamine crosslinking agent, and the sand bed sealing results before and after aging increased. This is because increasing the amount of crosslinking agent leads to intensified resin crosslinking. Example 3 and Comparative Example 1 reduced and did not add cationic composite polyamine crosslinking agent, respectively, and the sand bed sealing results before and after aging both increased. This is because reducing the amount of cationic polyamine crosslinking agent affects the crosslinking of the resin, thus affecting the sealing effect of the thermal insulation material. Therefore, an appropriate amount of cationic polyamine crosslinking agent has a significant impact on improving the overall performance of the thermal insulation material. Compared to Example 1, Example 4 and Comparative Example 2, with reduced and no addition of hydrophobic aerogel material respectively, showed a certain increase in sand bed plugging results before and after aging. This indicates that an appropriate amount of aerogel can improve the plugging performance of the thermal insulation material. Comparative Example 5, which did not undergo vacuum impregnation testing, showed an increase in sand bed plugging results before and after aging. This is because vacuum impregnation allows the aerogel to penetrate into the inorganic fiber skeleton, and the resin will coat the surface of the inorganic fibers, thereby increasing the plugging performance of the thermal insulation material. Compared to Example 1, Example 5 and Comparative Example 3, with reduced and no addition of inorganic fibers respectively, showed a certain increase in sand bed plugging results before and after aging. This is because the inorganic fiber skeleton can act as a bridging agent, improving the compactness of the mud cake and enhancing the plugging performance of the drilling fluid. Compared to Example 1, Example 6 increased the amount of surfactant, resulting in greater sand bed sealing performance before and after aging. This is because the increased amount of cationic surfactant affects the dispersibility of clay in the base slurry, thus reducing sealing performance. In Comparative Example 4, no hydrophilic modification was performed, resulting in greater sand bed sealing performance before and after aging. This is because the insulation material without hydrophilic modification has poor affinity with clay particles in the base slurry, thus affecting the sealing performance of the base slurry. Therefore, using an appropriate amount of cationic surfactant to hydrophilically modify the insulation material helps improve the performance of the insulation material.

[0084] 3. Thermal conductivity test of mud cake

[0085] 2% of the thermal insulation material from the examples and comparative examples (i.e., 2g per 100mL of base slurry) was added to a 4% drilling fluid base slurry, and then placed in an aging tank and aged at 220℃ for 16 hours. The original 4% base slurry served as the control group. The sample slurry and base slurry before aging were centrifuged at 8000r / min for 5 minutes. After centrifugation, the lower solid phase was dried to constant weight in a vacuum drying oven and then pulverized through a 200-mesh sieve. The solid powder was pressed into square mud cakes with dimensions of 9.9mm*9.9mm and a thickness of 2mm using a mold, forming the drilling fluid mud cake. Following the above method, square mud cakes of aged sample slurry and base slurry were prepared, and their thermal conductivity was tested, as shown in Table 3.

[0086] Table 3. Experimental results of thermal conductivity

[0087] Sample Name Thermal conductivity of the mud cake before aging / (W / (m*K)) Thermal conductivity of aged mud cake / (W / (m*K)) base slurry 0.986 0.991 4% base slurry + 2% Example 1 0.478 0.482 4% base slurry + 2% Example 2 0.491 0.506 4% base slurry + 2% Example 3 0.486 0.498 4% base slurry + 2% Example 4 0.504 0.513 4% base slurry + 2% Example 5 0.491 0.502 4% base slurry + 2% Example 6 0.483 0.492 4% base slurry + 2% Example 7 0.480 0.487 4% base slurry + 2% comparative example 1 0.701 0.724 4% base slurry + 2% comparative example 2 0.731 0.751 4% base slurry + 2% comparative example 3 0.715 0.734 4% base slurry + 2% comparative example 4 0.674 0.698 4% base slurry + 2% comparative example 5 0.657 0.678

[0088] The thermal conductivity test results are shown in Table 3. Compared with the thermal conductivity of the mud cake prepared from the original base slurry, the thermal conductivity of each added slurry decreased, with Example 1 showing the best results. Compared with Example 1, Example 2 increased the amount of cationic composite polyamine crosslinking agent, but the thermal conductivity of the mud cake did not change significantly. Example 3 and Comparative Example 1 reduced and did not add cationic composite polyamine crosslinking agent, respectively, and the thermal conductivity of the mud cakes prepared before and after aging increased significantly. This is because reducing the amount of cationic composite polyamine leads to a weakening of the crosslinking and curing effect of melamine-formaldehyde resin and phenolic resin, making it more difficult to prepare the thermal insulation material. Compared with Example 1, Example 4 and Comparative Example 2 reduced and did not add hydrophobic aerogel material, respectively, and the thermal conductivity of the mud cakes before and after aging increased. This is because aerogel is a porous material, and the air in the pores reduces the overall thermal conductivity of the material. Compared to Example 1, Example 5 and Comparative Example 3 reduced and omitted the addition of inorganic fibers, respectively, and the thermal conductivity of the mud cake increased before and after aging. This is because inorganic fibers themselves are good heat-resistant and insulating materials, improving the overall insulation performance. Compared to Example 1, Example 6 increased the amount of surfactant, but the effect on the thermal conductivity of the mud cake before and after aging was limited. Comparative Example 4 did not undergo hydrophilic modification, and the thermal conductivity of the mud cake increased before and after aging. This is because the insulation material without hydrophilic modification has poor affinity with the clay particles in the base slurry, thus affecting the thermal conductivity of the mud cake. Compared to Example 1, Example 7 increased the amount of both resins, but the thermal conductivity of the mud cake before and after aging did not change significantly, indicating that increasing the amount of resin did not enhance the insulation performance of the material. Therefore, the amount of resin added needs to be moderate. Compared to Example 1, Comparative Example 5 did not undergo a vacuum impregnation experiment, and the thermal conductivity of the mud cake before and after aging increased. This is because vacuum impregnation allows the aerogel to enter the skeleton composed of inorganic fibers, and the resin will coat the surface of the inorganic fibers, thereby increasing the insulation performance of the insulation material.

Claims

1. A method for preparing a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid, comprising the following steps: (1) adding triethylenetetramine and 2-hydroxyethylamine into a solvent, then adding 3-chloro-2-hydroxypropyl-trimethylammonium chloride, adjusting the pH of the system to 8-9, heating to the reaction temperature, removing oxygen by nitrogen blowing, and then performing the reaction; after the reaction is completed, removing the solvent to obtain a cationic polyamine composite crosslinking agent; (2) adding melamine formaldehyde resin and phenolic resin into ethanol, stirring until uniform, then adding the cationic polyamine composite crosslinking agent obtained in step (1) and stirring until uniform to obtain a mixed solution A; (3) adding aerogel into ethylene glycol, stirring until uniform, then adding inorganic fiber and stirring until uniform to obtain a mixed solution B; (4) adding the mixed solution A obtained in step (2) into the mixed solution B obtained in step (3) to perform vacuum impregnation, obtaining a mixed solution C; then evaporating and removing ethanol in the mixed solution C, and performing temperature curing; then performing centrifugal washing, drying, and grinding to obtain an intermediate product; placing the intermediate product into a cationic surfactant aqueous solution, mixing until uniform, and then drying to obtain a resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluid. In step (1), the solvent is a mixed solvent of water and ethanol, and the mass ratio of water to ethanol in the mixed solvent is 1:2-4; the mass ratio of the solvent to 3-chloro-2-hydroxypropyl-trimethylammonium chloride is 5-15:1; the mass ratio of triethylenetetramine to 3-chloro-2-hydroxypropyl-trimethylammonium chloride is 1-2:1; and the mass ratio of 2-hydroxyethylamine to 3-chloro-2-hydroxypropyl-trimethylammonium chloride is 0.5-1:

1. In step (1), the pH of the system is adjusted using a NaOH aqueous solution with a mass fraction of 10-30%; the time for removing oxygen by nitrogen blowing is 20-30 min; the reaction temperature is 45-55℃; and the reaction time is 3-5 h. In step (2), the mass ratio of melamine formaldehyde resin to phenolic resin is 0.1-0.3:1; and the mass ratio of ethanol to phenolic resin is 2-4:1; the total mass of melamine formaldehyde resin, phenolic resin, and ethanol to the mass of the cationic polyamine composite crosslinking agent is 1:0.01-0.

05. In step (3), the aerogel is hydrophobic SiO2 aerogel particles with a particle size of 20-50 nm; and the mass ratio of ethylene glycol to aerogel is 20-80:1; the inorganic fiber is two kinds of aluminum silicate fiber, sepiolite fiber, and ceramic fiber; the length of the inorganic fiber is 20-40 μm; the diameter of the inorganic fiber is 1-5 μm; and the mass ratio of the inorganic fiber to aerogel is 3-12:

1. In step (4), the mass ratio of the total mass of melamine formaldehyde resin and phenolic resin in the mixed solution A to the mass of aerogel in the mixed solution B is 1-4:

1. In step (4), the vacuum degree of vacuum impregnation is 0.05-0.07 MPa, and the vacuum impregnation time is 20-30 h; the step of evaporating and removing ethanol is heating the mixed solution C to 85-95℃ to evaporate and remove ethanol; and the temperature curing is performed at 80-100℃. ​ ​ ​ ​ 2. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ ​ 3. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ 4. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ ​ 5. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ ​ 6. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ 7. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, ​ ​ The solidification step in step (4) is: raising the temperature of the product obtained by removing ethanol to 120℃ and solidifying for 3h, and then continuously raising the temperature to 150℃ and solidifying for 1h; The washing is centrifugal washing for 3-5 times using ethanol.

8. The method of claim 1, wherein the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids is characterized by, The cationic surfactant in step (4) is one of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and octadecyltrimethylammonium chloride; the mass fraction of the cationic surfactant aqueous solution is 20%; the mass ratio of the cationic surfactant aqueous solution to the intermediate product is 0.01-0.05:1; the intermediate product and the cationic surfactant aqueous solution are uniformly mixed in a colloid mill; and the drying is all drying at 60-90℃ until constant weight.

9. A resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids, characterized by, The preparation method is prepared by the preparation method in claim 1.

10. Use of the resin-coated inorganic fiber / aerogel composite thermal insulation material for water-based drilling fluids according to claim 9, characterized in that, For reducing the temperature of water-based drilling fluid. For reducing the temperature of water-based drilling fluid.

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