Degradable occlusive material and method of making and use thereof

Abstract

The application provides a degradable plugging material and a preparation method and application thereof, and belongs to the technical field of oil field chemicals; the plugging material takes lactide, aliphatic diol, epichlorohydrin, acid anhydride compound, aromatic diglycidyl ester and aliphatic monoamine as main raw materials, first prepares double-end hydroxyl-terminated polylactic acid, then modifies the double-end hydroxyl-terminated polylactic acid by epichlorohydrin to obtain double-end epoxy-terminated polylactic acid, then reacts with the acid anhydride compound to generate aromatic polyester compound containing a polylactic acid segment, and finally obtains degradable plugging material particles through low-temperature freezing, ball milling and surface modification treatment. The obtained material can effectively fill mud cake pores and micro cracks, and improve the plugging and filtration reduction performance of drilling fluid; meanwhile, the material contains a hydrolysable polyester structure, has temperature response degradation characteristics in a high-temperature clean water environment, can meet the requirements of early plugging stability and late degradation and plugging removal, and is suitable for downhole operation fields such as oil and gas field drilling, temporary plugging and reservoir protection.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, particularly to the field of oil and gas field drilling technology, specifically to a biodegradable plugging material, its preparation method, and its application. Background Technology

[0002] Unconventional reservoirs such as shale and tight sandstone typically exhibit numerous micron-, submicron-, and nano-scale pores and fractures, with small pore throats and complex fracture distribution. During drilling, drilling fluid filtrate easily intrudes into the formation along micro-fractures, bedding planes, and micro / nanopore throats, causing clay mineral hydration and swelling, reduced rock cementation strength, and fracture propagation. This can lead to complex downhole problems such as wellbore instability, wellbore enlargement, stuck pipe, and lost circulation. Therefore, in drilling low- to ultra-low-permeability reservoirs, it is usually necessary to use plugging materials to effectively seal formation pores and fractures to reduce drilling fluid loss and minimize filtrate intrusion into deeper formations, thereby ensuring wellbore stability and reducing reservoir damage. Currently, plugging materials used for drilling, plugging, and temporary plugging operations mainly include fibrous materials, granular materials, fiber-granular composite materials, polymer materials, and water-absorbing and swelling materials. Fiber-based materials primarily rely on fiber overlap to form a network structure for plugging. However, they are prone to dispersion and drift in drilling fluids, resulting in a relatively loose plugging layer structure with limited plugging strength, making it difficult to meet the stable plugging requirements under high pressure differentials or large fractures. Particulate materials mainly rely on particle size matching, particle bridging, and pore filling for plugging. While they possess some plugging capability, some particles are difficult to degrade naturally and tend to remain in formation pore throats or fractures, affecting reservoir permeability recovery. Fiber-particle composite materials can improve plugging effectiveness through the synergistic effect of fiber overlap and particle filling, but their formulation systems are complex, requiring high control during construction and preparation. Polymer materials typically achieve plugging through film formation, bonding, crosslinking, or elastic deformation, but some systems suffer from uncontrollable crosslinking reactions, excessive degradation residues, or insufficient environmental adaptability. Water-absorbing and swelling materials can fill pores and fractures through water absorption and expansion, but they are prone to structural damage in high-temperature, high-pressure, and high-shear downhole environments, exhibiting insufficient pressure-bearing stability.

[0003] In recent years, biodegradable plugging materials have attracted attention due to their advantages in later-stage unblocking and reducing reservoir residue. Some biodegradable temporary plugging materials have been disclosed in existing technologies. For example, Chinese patent CN119979145B discloses a self-degradable particulate temporary plugging agent for fracturing, its preparation method, and its application. This agent can improve the initial plugging tightness, but the plugging layer is prone to cracking over time due to water absorption, expansion, and particle disintegration, leading to increased leakage in the later stages. It is also difficult to maintain stable plugging for extended periods under high-temperature conditions. Chinese patent CN116376525A discloses a temporary plugging agent, a temporary plugging agent composition, and its preparation method. Its unblocking process is highly dependent on hydrochloric acid or a hydrochloric acid / hydrofluoric acid mixed acid system, resulting in problems such as acid corrosion, high construction costs, and potential secondary damage to the reservoir. In addition, some existing biodegradable polyester plugging materials improve the material's temperature resistance and mechanical stability by introducing aromatic structures into aliphatic polyesters. While such methods can improve the structural strength of materials to some extent, simply introducing aromatic anhydrides or aromatic monomers often increases molecular chain rigidity and steric hindrance, reducing the hydrolysis rate in aqueous environments. This makes it difficult for the material to simultaneously achieve both early-stage plugging stability and later-stage controllable degradation performance. Furthermore, the dispersion stability, mud cake micropore filling capacity, and high-temperature, high-pressure filtration loss reduction effects of ordinary polylactic acid particles or ordinary aromatic polyester particles in water-based drilling fluids remain limited, making it difficult to meet the comprehensive requirements of compatibility, plugging properties, and degradability in complex downhole environments.

[0004] Therefore, existing technologies still struggle to simultaneously meet the comprehensive requirements of capping layer stability, good drilling fluid compatibility, and low residual unblocking under high temperature and high pressure conditions. To reduce wellbore instability and reservoir damage caused by drilling fluid filtrate intrusion, there is an urgent need for a biodegradable capping material for water-based drilling fluids that offers good capping size matching, strong adaptability to downhole environments, stable initial capping, and controllable degradation under high temperature conditions in the later stages. Summary of the Invention

[0005] To address the problems of conventional plugging agents being difficult to degrade naturally and easily leaving residues in microfractures and micro / nanopore throats of low-to-low-permeability reservoirs, causing reservoir damage, this invention provides a biodegradable plugging material, its preparation method, and its applications. The plugging material of this invention is prepared primarily from lactide, aliphatic diols, epichlorohydrin, acid anhydrides, aromatic diglycidyl esters, and aliphatic monoamines. Through polylactic acid segment construction, introduction of aromatic polyester structures, low-temperature ball milling granulation, and surface modification, the material exhibits excellent compatibility with water-based drilling fluids, plugging and filtration loss reduction performance, and temperature-responsive degradation properties.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing a biodegradable sealing material includes the following steps: S1. Prepare double-hydroxyl-terminated polylactic acid using lactide and aliphatic diols as raw materials; S2. Using the aforementioned hydroxyl-terminated polylactic acid and epichlorohydrin as raw materials, prepare hydroxyl-terminated polylactic acid. S3. Using the aforementioned double-epoxy-terminated polylactic acid and anhydride compounds as raw materials, prepare aromatic polyester compounds containing polylactic acid segments; S4. The aromatic polyester compound containing polylactic acid segments is frozen and embrittled, then pulverized to obtain aromatic polyester compound particles containing polylactic acid segments. S5. The aromatic polyester compound particles containing polylactic acid segments are subjected to surface reaction modification treatment with aromatic diglycidyl ester and aliphatic monoamine, and then separated and purified to obtain biodegradable sealing material particles.

[0007] In one specific embodiment of the present invention, in step S1, the mass ratio of lactide to aliphatic diol is 16:1 to 232:1; the reaction is carried out under inert gas protection, with stannous octoate as the catalyst, the amount of which is 0.05% to 0.20% of the mass of lactide, and anhydrous toluene as the solvent, and the reaction is stirred at 110°C to 120°C for 18 to 24 hours.

[0008] In one specific embodiment of the present invention, in step S2, the mass ratio of epichlorohydrin to dihydroxyl-terminated polylactic acid is 0.5:1 to 0.8:1; the reaction is carried out under inert gas protection, using tetrabutylammonium bromide as a catalyst, the amount of which is 1% to 10% of the mass of the dihydroxyl-terminated polylactic acid, and the reaction is first stirred at 40°C to 60°C for 2 to 4 hours, and then the reaction is continued under alkaline conditions for 4 to 10 hours. The type and amount of alkali can be added as needed, for example, potassium carbonate can be added in an amount of 10% to 40% of the mass of the dihydroxyl-terminated polylactic acid, so as to maintain alkaline conditions at the end of the reaction.

[0009] In one specific embodiment of the present invention, in step S3, the mass ratio of the acid anhydride compound to the di-epoxy-terminated polylactic acid is 0.02:1 to 0.08:1; a trivalent chromium porphyrin chloride complex and bis(triphenylphosphine)imine onium chloride are used as catalysts, wherein the amount of the trivalent chromium porphyrin chloride complex is 0.1% to 0.5% of the mass of the di-epoxy-terminated polylactic acid, and the mass ratio of bis(triphenylphosphine)imine onium chloride to the trivalent chromium porphyrin chloride complex is 0.44:1 to 0.82:1; under inert gas protection, anhydrous toluene is used as solvent, and the reaction is stirred at 75 to 85°C for 12 to 18 h.

[0010] In one specific embodiment of the present invention, in step S5, the mass ratio of the aromatic diglycidyl ester to the aliphatic monoamine is 1:0.21 to 1:0.56, and the mass ratio of the aromatic polyester compound particles containing polylactic acid segments to the aromatic diglycidyl ester is 1:0.03 to 1:0.12. Under inert gas protection, using anhydrous N,N-dimethylformamide as a solvent, the reaction is first stirred at 40°C to 60°C for 2 h to 4 h, and then stirred at 70°C to 90°C for 6 h to 12 h.

[0011] In one specific embodiment of the present invention, the aliphatic diol is one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

[0012] In one specific embodiment of the present invention, the acid anhydride compound is selected from one of phthalic anhydride, 4-methylphthalic anhydride, and 3-methylphthalic anhydride.

[0013] In one specific embodiment of the present invention, the aromatic diglycidyl ester is one of diglycidyl isophthalate, diglycidyl terephthalate, and diglycidyl phthalate, and the aliphatic monoamine is one of n-hexylamine, n-octylamine, and n-butylamine.

[0014] A biodegradable sealing material is prepared using the above method.

[0015] An application of a biodegradable plugging material involves using the aforementioned biodegradable plugging material as a plugging agent to prepare a water-based drilling fluid. This water-based drilling fluid is then used in high-temperature wells at 120℃ to 150℃ to improve the density and stability of the plugging layer, reduce high-temperature and high-pressure filtration loss, and achieve degradation and unblocking in the subsequent high-temperature environment.

[0016] Beneficial effects: This invention improves the interfacial compatibility between particles and water-based drilling fluid systems by introducing modified structures containing polar groups, aromatic structures, and aliphatic segments onto the particle surface, reducing agglomeration tendency and enhancing drilling fluid compatibility and plugging stability. The resulting plugging material can fill mud cake pores, improve the density of the plugging layer, reduce high-temperature and high-pressure filtration loss, and degrade and unblock in subsequent high-temperature environments. Attached Figure Description

[0017] Figure 1 The degradation of Example 1 at different temperatures; Figure 2 The degradation of Example 2 at different temperatures; Figure 3 The degradation results of Example 3 at different temperatures; Figure 4This is a comparison of the degradation of Example 1 at different temperatures. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 The preparation of biodegradable sealing materials includes the following steps: S1. Place lactide in a vacuum drying oven and dry at 40℃~50℃ for 12h to obtain dried lactide. Add 14.41 g of dried lactide to a dry four-necked flask, add 40 mL of anhydrous toluene to the flask, purge with argon gas and bubble to remove oxygen for 30 minutes. Then, under argon protection, add 1.0 mL of anhydrous toluene solution of stannous octoate (stannous octoate content is 7.2 mg / mL) using a dry syringe. Place the reaction system in an oil bath and heat to 110℃. Under argon protection, add 0.155 g of dry ethylene glycol and stir for 18 hours. After the reaction is completed, cool the reaction system to room temperature and expose it to air to terminate the reaction. Then add 20 mL of dichloromethane. Slowly add the resulting reaction solution dropwise to 120 mL of cold isopropanol for precipitation. Filter and collect the precipitate, and repeat the dissolution-precipitation process three times. Each time, 20 mL of dichloromethane is used for dissolution, and each time 120 mL of cold isopropanol is used for precipitation. mL was used to remove unreacted monomers, catalysts and low molecular weight impurities; finally, the obtained precipitate was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain double-hydroxyl-terminated polylactic acid.

[0020] S2. Hydroxyl-terminated polylactic acid (PLA) was placed in a vacuum drying oven and dried at 50°C for 12 hours to obtain dried hydroxyl-terminated PLA. 10.00 g of the dried hydroxyl-terminated PLA was added to a dry three-necked flask, along with 6.35 g of epichlorohydrin and 0.30 g of tetrabutylammonium bromide. Argon gas was introduced for protection, and the mixture was heated to 45°C and stirred for 3 hours. Subsequently, 1.00 g of anhydrous potassium carbonate was added in portions, and the reaction continued for 6 hours. After the reaction was complete, the mixture was vacuum filtered, and the filtrate was extracted twice with 15 mL of toluene each time. The resulting organic phase was washed twice with 20 mL of deionized water each time. The organic layer was separated, allowed to stand overnight, dried with 2.0 g of anhydrous sodium sulfate, and then subjected to rotary evaporation to obtain epoxy-terminated PLA.

[0021] S3. Add 0.018 g of trivalent chromium porphyrin chloride complex and 0.013 g of bis(triphenylphosphine)imine onium chloride to a dry reaction vessel equipped with a magnetic stirrer. Then, under argon protection, add 0.458 g of phthalic anhydride, 37 mL of anhydrous toluene, and 10.19 g of polylactic acid with epoxy groups at the ends. Seal the reaction vessel. Heat the reaction system to 80°C and stir for 16 hours. After the reaction is completed, add 0.20 mL of ethanol / hydrochloric acid solution to terminate the reaction, and then add 20 mL of dichloromethane to dilute the reaction solution. Then, under vigorous stirring, add 100 mL of ethanol to precipitate the solution. Collect the crude polymer by filtration, place the crude polymer in a vacuum drying oven, and dry it at 80°C for 10 hours to obtain an aromatic polyester compound containing polylactic acid segments.

[0022] S4. The aromatic polyester compound containing polylactic acid segments was vacuum dried at 60°C for 4 hours; 5.00g of raw material was pre-cooled in a -80°C low-temperature chamber for 30 minutes, and then immersed in liquid nitrogen for deep freezing for 2 minutes; the aromatic polyester compound containing polylactic acid segments was obtained by ball milling in a planetary ball mill at a speed of 3000 rpm, using 10.00g of zirconia grinding balls, and for a ball milling time of 2 hours.

[0023] S5. Add 5.00 g of aromatic polyester compound particles containing polylactic acid segments to a dry three-necked flask. Add 25.00 g of anhydrous N,N-dimethylformamide to the flask, purge with argon gas and bubble for deoxygenation for 20 min, then disperse ultrasonically for 10 min and mechanically stir for 30 min under argon protection to ensure thorough dispersion of the particles. Then add 0.15 g of dry diglycidyl phthalate to the dispersion system and stir at room temperature for 30 min. Then raise the reaction system to 40°C and slowly add 0.04 g of n-butylamine dropwise using a dropping funnel. After the addition is complete, continue stirring at 40°C for 2 h. Then raise the reaction system to 70°C and continue stirring for 6 h. After the reaction is complete, slowly pour the resulting reaction solution into excess ethanol for precipitation, and collect the solid particles by filtration or centrifugation. Wash the obtained solid particles with ethanol using ultrasound, repeating the washing until the supernatant is clear and transparent. Finally, place the obtained particles in a vacuum drying oven at 40°C. The material is dried to constant weight and then sieved to obtain biodegradable sealing material particles.

[0024] Example 2 The preparation of biodegradable sealing materials includes the following steps: S1. Place lactide in a vacuum drying oven and dry at 40℃~50℃ for 12h to obtain dried lactide. Add 14.41 g of dried lactide to a dry four-necked flask, add 40 mL of anhydrous toluene to the flask, purge with argon gas and bubble to remove oxygen for 30 minutes. Then, under argon protection, add 1.0 mL of anhydrous toluene solution of stannous octoate (stannous octoate content is 14.4 mg / mL) using a dry syringe. Place the reaction system in an oil bath and heat to 115℃. Under argon protection, add 0.150 g of dry 1,4-butanediol and stir for 22 hours. After the reaction is completed, cool the reaction system to room temperature and expose it to air to terminate the reaction. Then add 20 mL of dichloromethane. Slowly add the resulting reaction solution dropwise to 120 mL of cold isopropanol for precipitation. Filter and collect the precipitate, and repeat the dissolution-precipitation process three times. Each time, 20 mL of dichloromethane is used for dissolution and 120 mL of cold isopropanol is used for precipitation. mL was used to remove unreacted monomers, catalysts and low molecular weight impurities; finally, the obtained precipitate was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain double-hydroxyl-terminated polylactic acid.

[0025] S2. Place the hydroxyl-terminated polylactic acid (PLA) in a vacuum drying oven and dry it at 50°C for 12 hours to obtain dried hydroxyl-terminated PLA. Add 10.00 g of the dried hydroxyl-terminated PLA to a dry three-necked flask, add 6.36 g of epichlorohydrin and 0.50 g of tetrabutylammonium bromide, purge with argon gas, heat to 50°C and stir for 3 hours. Then add 2.50 g of anhydrous potassium carbonate in batches and continue the reaction for 8 hours. After the reaction is complete, filter under vacuum, extract the filtrate twice with 15 mL of toluene each time, and wash the resulting organic phase twice with 20 mL of deionized water each time. Separate the organic layer, let it stand overnight, dry it with 2.0 g of anhydrous sodium sulfate, and then perform rotary evaporation to obtain hydroxyl-terminated PLA.

[0026] S3. Add 0.024 g of trivalent chromium porphyrin chloride complex and 0.017 g of bis(triphenylphosphine)imine onium chloride to a dry reaction vessel equipped with a magnetic stirrer. Then, under argon protection, add 0.371 g of 4-methylphthalic anhydride, 28 mL of anhydrous toluene, and 10.13 g of polylactic acid with epoxy groups at the ends. Seal the reaction vessel. Heat the reaction system to 80°C and stir for 16 hours. After the reaction is completed, add 0.20 mL of ethanol / hydrochloric acid solution to terminate the reaction, and then add 20 mL of dichloromethane to dilute the reaction solution. Then, under vigorous stirring, add 100 mL of ethanol to precipitate the solution. Collect the crude polymer by filtration, place the crude polymer in a vacuum drying oven, and dry it at 80°C for 10 hours to obtain an aromatic polyester compound containing polylactic acid segments.

[0027] S4. The aromatic polyester compound containing polylactic acid segments was vacuum dried at 60°C for 4 hours; 5.00g of raw material was pre-cooled in a -80°C low-temperature chamber for 30 minutes, and then immersed in liquid nitrogen for deep freezing for 2 minutes; the aromatic polyester compound containing polylactic acid segments was obtained by ball milling in a planetary ball mill at a speed of 3000 rpm, using 10.00g of zirconia grinding balls, and for a ball milling time of 2 hours.

[0028] S5. Add 5.00 g of aromatic polyester compound particles containing polylactic acid segments to a dry three-necked flask. Add 40.00 g of anhydrous N,N-dimethylformamide to the flask, purge with argon gas and bubble for deoxygenation for 30 min, then disperse ultrasonically for 20 min and mechanically stir for 45 min under argon protection to ensure thorough dispersion. Add 0.40 g of dried diglycidyl isophthalate to the dispersion and stir at 30°C for 60 min. Then heat the reaction system to 50°C and slowly add 0.145 g of n-hexylamine dropwise using a dropping funnel. After the addition is complete, continue stirring at 50°C for 3 h. Then heat the reaction system to 80°C and continue stirring for 8 h. After the reaction is complete, slowly pour the resulting reaction solution into excess ethanol for precipitation, and collect the solid particles by filtration or centrifugation. Wash the obtained solid particles ultrasonically with ethanol, repeating the washing until the supernatant is clear and transparent. Finally, place the obtained particles in a vacuum drying oven at 50°C. The material is dried to constant weight and then sieved to obtain biodegradable sealing material particles.

[0029] Example 3 The preparation of biodegradable sealing materials includes the following steps: S1. Place lactide in a vacuum drying oven and dry at 40℃~50℃ for 12h to obtain dried lactide. Add 14.41 g of dried lactide to a dry four-necked flask, add 40 mL of anhydrous toluene to the flask, purge with argon gas and bubble to remove oxygen for 30 minutes. Then, under argon protection, add 1.0 mL of anhydrous toluene solution of stannous octoate (stannous octoate content is 28.8 mg / mL) using a dry syringe. Place the reaction system in an oil bath and heat to 120℃. Under argon protection, add 0.095 g of dry 1,3-propanediol and stir for 24 hours. After the reaction is completed, cool the reaction system to room temperature and expose it to air to terminate the reaction. Then add 20 mL of dichloromethane. Slowly add the resulting reaction solution dropwise to 120 mL of cold isopropanol for precipitation. Filter and collect the precipitate, and repeat the dissolution-precipitation process three times. Each time, 20 mL of dichloromethane is used for dissolution and 120 mL of cold isopropanol is used for precipitation. mL was used to remove unreacted monomers, catalysts and low molecular weight impurities; finally, the obtained precipitate was placed in a vacuum drying oven and dried at 60°C to constant weight to obtain double-hydroxyl-terminated polylactic acid.

[0030] S2. Hydroxyl-terminated polylactic acid (PLA) was placed in a vacuum drying oven and dried at 50°C for 12 hours to obtain dried hydroxyl-terminated PLA. 10.00 g of the dried hydroxyl-terminated PLA was added to a dry three-necked flask, along with 6.38 g of epichlorohydrin and 0.70 g of tetrabutylammonium bromide. Argon gas was introduced for protection, and the mixture was heated to 60°C and stirred for 4 hours. Subsequently, 4.00 g of anhydrous potassium carbonate was added in portions, and the reaction continued for 10 hours. After the reaction was complete, the mixture was vacuum filtered, and the filtrate was extracted twice with 15 mL of toluene each time. The resulting organic phase was washed twice with 20 mL of deionized water each time. The organic layer was separated, allowed to stand overnight, dried with 2.0 g of anhydrous sodium sulfate, and then subjected to rotary evaporation to obtain epoxy-terminated PLA.

[0031] S3. Add 0.027 g of trivalent chromium porphyrin chloride complex and 0.018 g of bis(triphenylphosphine)imine onium chloride to a dry reaction vessel equipped with a magnetic stirrer. Then, under argon protection, add 0.307 g of 3-methylphthalic anhydride, 22 mL of anhydrous toluene, and 10.10 g of polylactic acid with two epoxy groups. Seal the reaction vessel. Heat the reaction system to 80°C and stir for 16 hours. After the reaction is completed, add 0.20 mL of ethanol / hydrochloric acid solution to terminate the reaction, and then add 20 mL of dichloromethane to dilute the reaction solution. Then, under vigorous stirring, add 100 mL of ethanol to precipitate the solution. Collect the crude polymer by filtration, place the crude polymer in a vacuum drying oven, and dry it at 80°C for 10 hours to obtain an aromatic polyester compound containing polylactic acid segments.

[0032] S4. 5.00 g of aromatic polyester compound containing polylactic acid segments was vacuum dried at 60℃ for 4 hours; the raw material was pre-cooled in a -80℃ low temperature chamber for 30 minutes, and then immersed in liquid nitrogen for deep freezing for 2 minutes; the material was ball-milled using a planetary ball mill at a ball milling speed of 3000 rpm, 10.00 g of zirconia grinding balls, and a ball milling time of 2 hours to obtain particles of aromatic polyester compound containing polylactic acid segments.

[0033] S5. Add 5.00 g of dried aromatic polyester compound particles containing polylactic acid segments to a dry three-necked flask. Add 50.00 g of anhydrous N,N-dimethylformamide to the flask, purge with argon gas and bubble to deoxygenate for 40 min, then ultrasonically disperse for 30 min, followed by mechanical stirring under argon protection for 60 min to ensure thorough dispersion of the particles. Then add 0.60 g of dried diglycidyl terephthalate to the dispersion system and stir at 40 °C for 120 min. Subsequently, raise the reaction system to 60 °C and slowly add 0.31 g of n-octylamine dropwise using a dropping funnel. After the addition of g, the reaction mixture was stirred at 60°C for 4 hours. Then, the reaction system was heated to 90°C and stirred for another 12 hours. After the reaction was completed, the resulting reaction solution was slowly poured into excess ethanol for precipitation. The solid particles were collected by filtration or centrifugation. The obtained solid particles were ultrasonically washed with ethanol and washed repeatedly until the supernatant was clear and transparent. Finally, the obtained particles were placed in a vacuum drying oven and dried at 60°C to constant weight. After sieving, the biodegradable sealing material particles were obtained.

[0034] Comparative Example 1 The preparation of biodegradable sealing materials includes the following steps: Aromatic polyester compound particles containing polylactic acid segments were prepared according to the preparation methods of S1 to S4 in Example 2. The surface modification treatment of aromatic diglycidyl ester and aliphatic monoamine in S5 was not performed. The aromatic polyester compound particles containing polylactic acid segments obtained by low temperature freezing and ball milling were directly used as sealing materials.

[0035] To further illustrate the effectiveness of the biodegradable temporary plugging material of the present invention, performance tests were conducted on the biodegradable plugging materials in Examples 1, 2, 3 and Comparative Example 1.

[0036] Test Example 1 (Degradation Performance Test) The degradation performance of the biodegradable sealing agents from Examples 1-3 and Comparative Example 1 was tested in a water environment. The degradation at 60℃, 90℃, 120℃, and 150℃ was observed. The degradation under different temperature conditions is shown below. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown.

[0037] Depend on Figures 1-4 It can be seen that Examples 1-3 and Comparative Example 1 all exhibit temperature-responsive degradation characteristics. As the temperature increases from 60℃ to 150℃, the mass loss rate of each sample gradually increases, indicating that heating can promote the hydrolysis of polyester segments. At 60℃ and 90℃, the degradation rate of each sample is generally slow, and the difference between Examples 1-3 and Comparative Example 1 is not significant, indicating that the materials all have a certain degree of early-stage stability at lower temperatures. When the temperature rises to 120℃ and above, Examples 1-3 exhibit a smoother and more controllable early-stage degradation process compared to Comparative Example 1, indicating that the surface modification of aromatic diglycidyl ester and aliphatic monoamine can regulate the penetration rate of water molecules into the particles in a clean water environment, allowing the material to maintain a low mass loss rate in the early stages of plugging, which is beneficial for maintaining particle integrity and forming a more stable plugging layer. As the high-temperature treatment time increases, the degradation of Examples 1-3 gradually accelerates, meeting the requirements for later degradation and unblocking. This demonstrates that Examples 1-3, compared to Comparative Example 1, are better able to balance early-stage sealing stability and later-stage high-temperature degradation performance.

[0038] Test Example 2 (Compatibility of Water-Based Drilling Fluids) Preparation of water-based drilling fluid slurry: By weight, add 400 parts water, 8 parts bentonite and 0.8 parts anhydrous sodium carbonate to a high-speed stirring cup and stir at high speed for 10 min; while stirring at high speed, add 20 parts sulfonated methyl phenolic resin SMP-3 and continue stirring at high speed for 10 min; then add 10 parts sulfonated lignite SMC, 1 part high-temperature filtration loss reducer HF-1, 12 parts anti-sticking lubricant FK-10, 1 part xanthan gum and 12 parts potassium chloride in sequence, stirring at high speed for 10 min after each addition of a treatment agent; finally, add 88 parts barite and continue stirring at high speed for 30 min to obtain water-based drilling fluid slurry.

[0039] Different amounts of the biodegradable plugging material synthesized in Example 1, Example 2, Example 3 and Comparative Example 1 were added to the prepared water-based drilling fluid slurry to form corresponding water-based drilling fluids. The fluids were aged at 120°C for 16 hours, and the performance parameters of each water-based drilling fluid were measured. The results are shown in Table 1.

[0040] Table 1 Performance parameters of water-based drilling fluids containing different biodegradable sealing materials Note: HTHP has a temperature of 120℃ and a pressure of 4MPa; As shown in Table 1, after adding water-based drilling fluid to Examples 1-3 and Comparative Example 1, the apparent viscosity, plastic viscosity, and dynamic shear force of the drilling fluid changed only slightly, indicating that the above-mentioned plugging material has good compatibility with water-based drilling fluid and has little impact on the rheological properties of the drilling fluid. As the amount of plugging material increased from 0.5% to 2.0%, the overall HTHP filtration loss of each system gradually decreased, indicating that the plugging material has a plugging and filtration loss reduction effect. Under the same dosage conditions, the HTHP filtration loss of Examples 1-3 was lower than that of Comparative Example 1, indicating that the high-temperature and high-pressure plugging and filtration loss reduction performance of the material was improved after surface reaction modification treatment. Taking Example 2 as an example, the HTHP filtration loss at additions of 0.5%, 1.0%, 1.5%, and 2.0% were 7.2 mL, 5.6 mL, 4.2 mL, and 3.8 mL, respectively, all lower than the 8.2 mL, 6.8 mL, 5.9 mL, and 5.2 mL of Comparative Example 1 at the same addition. This indicates that the modification treatment is beneficial to improving the sealing and filtration loss reduction performance of the material at different additions.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a biodegradable sealing material, characterized in that, It is prepared using the following steps: S1. Prepare double-hydroxyl-terminated polylactic acid using lactide and aliphatic diols as raw materials; S2. Using the aforementioned hydroxyl-terminated polylactic acid and epichlorohydrin as raw materials, prepare hydroxyl-terminated polylactic acid. S3. Using an anhydride compound and di-epoxy-terminated polylactic acid (PLA) in a mass ratio of 0.02:1 to 0.08:1 as raw materials, and trivalent chromium porphyrin chloride complex and bis(triphenylphosphine)imine onium chloride as catalysts, under inert gas protection and with anhydrous toluene as solvent, the mixture is stirred at 75–85°C for 12–18 h to prepare an aromatic polyester compound containing PLA segments. The amount of the trivalent chromium porphyrin chloride complex is 0.1%–0.5% of the mass of the di-epoxy-terminated PLA, and the mass ratio of bis(triphenylphosphine)imine onium chloride to the trivalent chromium porphyrin chloride complex is 0.44:1 to 0.82:

1. The anhydride compound is selected from phthalic anhydride, 4-methylphthalic anhydride, and 3-methylphthalic anhydride. S4. The aromatic polyester compound containing polylactic acid segments is frozen and embrittled, then pulverized to obtain aromatic polyester compound particles containing polylactic acid segments. S5. The aromatic polyester compound particles containing polylactic acid segments are subjected to surface reaction modification treatment with aromatic diglycidyl ester and aliphatic monoamine, and then separated and purified to obtain biodegradable sealing material particles.

2. The method for preparing the biodegradable sealing material according to claim 1, characterized in that, In step S1, the mass ratio of lactide to aliphatic diol is 16:1 to 232:1; the reaction is carried out under inert gas protection, with stannous octoate as the catalyst, the amount of which is 0.05% to 0.20% of the mass of lactide, and anhydrous toluene as the solvent, and the reaction is stirred at 110℃ to 120℃ for 18h to 24h.

3. The method for preparing the biodegradable sealing material according to claim 1, characterized in that, In step S2, the mass ratio of epichlorohydrin to hydroxyl-terminated polylactic acid is 0.5:1 to 0.8:1; the reaction is carried out under inert gas protection, with tetrabutylammonium bromide as the catalyst, the amount of which is 1% to 10% of the mass of the hydroxyl-terminated polylactic acid, and the reaction is first stirred at 40℃ to 60℃ for 2 h to 4 h, and then the reaction is continued under alkaline conditions for 4 h to 10 h.

4. The method for preparing the biodegradable sealing material according to claim 1, characterized in that, In step S5, the mass ratio of the aromatic diglycidyl ester to the aliphatic monoamine is 1:0.21 to 1:0.56, and the mass ratio of the aromatic polyester compound particles containing polylactic acid segments to the aromatic diglycidyl ester is 1:0.03 to 1:0.

12. Under inert gas protection, using anhydrous N,N-dimethylformamide as a solvent, the reaction is first stirred at 40℃ to 60℃ for 2 h to 4 h, and then stirred at 70℃ to 90℃ for 6 h to 12 h.

5. The method for preparing the biodegradable sealing material according to claim 1, characterized in that, The aliphatic diol is one of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

6. The method for preparing the biodegradable sealing material according to claim 1, characterized in that, The aromatic diglycidyl ester is one of diglycidyl isophthalate, diglycidyl terephthalate, and diglycidyl phthalate, and the aliphatic monoamine is one of n-hexylamine, n-octylamine, and n-butylamine.

7. A biodegradable sealing material, characterized in that, It is prepared using the preparation method of the biodegradable sealing material according to any one of claims 1-6.

8. An application of a biodegradable sealing material, characterized in that, The biodegradable plugging material described in claim 7 is used as a plugging agent to prepare a water-based drilling fluid, and the water-based drilling fluid is used in high-temperature wells at 120℃~150℃.

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