Sealing ring for soluble bridge plug and preparation method of sealing ring

Abstract

The invention provides a sealing ring for a soluble bridge plug and a preparation method thereof, and belongs to the technical field of sealing materials, the preparation method comprises the following preparation steps: S1, dispersing hollow mesoporous silica in absolute ethyl alcohol, adding ZnCl2, heating, performing ultrasonic treatment, and performing vacuum drying to obtain ZnCl2-loaded HMSN; s2, adding 3-carboxyphenylboronic acid and glucan into a PBS (Phosphate Buffer Solution), reacting to obtain a PBA-Dex compound solution, then adding HMSN loaded with ZnCl2, stirring, centrifuging, washing and drying to obtain an HMSN-ZnCl2 composite material; s3, polyglycolic acid, silane modified glass fibers, bisoxazoline and acetyl tributyl citrate are mixed and internally mixed, then the HMSN-ZnCl2 composite material is added for mixing, injection molding, annealing and curing, and a finished product is obtained. According to the prepared sealing ring for the soluble bridge plug, the strength can be remarkably improved, meanwhile, the dissolving speed of the sealing ring in the early stage is delayed, the sealing ring can keep high tensile strength for a long time after descending into a well, and the sealing ring can be rapidly dissolved in the later stage.

Description

Technical Field

[0001] The present invention relates to the technical field of sealing materials, and in particular to a sealing ring for a soluble bridge plug and a preparation method thereof. Background Art

[0002] With the development of soluble bridge plugs and the improvement of technology, more and more materials are used to manufacture soluble bridge plugs. The important component of soluble bridge plugs is the sealing ring that plays the pressure-bearing sealing function. Therefore, the material selection and preparation of the sealing ring are very critical.

[0003] At present, the materials used to manufacture soluble bridge plug sealing rings are mainly polymers and magnesium-aluminum alloys. Among them, although magnesium-aluminum alloys are highly favored due to their high strength, solubility and certain plasticity, and are widely used in staged fracturing soluble bridge plugs, the dissolution of magnesium-aluminum alloys is generally not thorough, and some hard residues are easily left. Since staged fracturing requires the use of more bridge plugs, residual pressure accumulation is likely to block the pipeline, reduce oil and gas production, and affect secondary mining. Polymer materials, such as polyglycolic acid (PGA), have excellent degradation performance, and their hydrolysis products are environmentally friendly. They can replace magnesium-aluminum alloys to solve the problem of incomplete dissolution. However, when faced with the requirement of high compressive strength for high-depth water wells, the strength of polyglycolic acid materials cannot meet the requirements of high-pressure water wells. In addition, polyglycolic acid (PGA) has excellent degradation performance and dissolves relatively quickly, which can easily lead to short pressure-bearing time and premature dissolution, making it unable to adapt to the requirements of long-term pressure-bearing sealing.

[0004] For example, patent application publication number CN118667311A discloses a polyglycolic acid composite material, its molded product, and a soluble bridge plug, comprising: a blend formed by polyglycolic acid and polylactic acid, wherein the weight ratio of polyglycolic acid to polylactic acid is 99 / 1-50 / 50; and a compatibilizer, wherein the compatibilizer is a polylactic acid-polyglycolic acid copolymer, and the weight ratio of the compatibilizer to the blend is 0.5 / 100-5 / 100. Although this solution can improve the interfacial bonding between polyglycolic acid and polylactic acid by the compatibilizer, thereby enhancing the toughness of the material without affecting the degradation rate of the polyglycolic acid composite material. However, the strength of the composite material obtained by this solution is not high enough, and it still cannot meet the requirements of high-pressure wells. In addition, the dissolution rate of the entire process is relatively fast, which makes the time for maintaining the high pressure-bearing effect in the early stage relatively short, and it is even easy to dissolve prematurely in complex environments, making it difficult to meet the current requirements of staged fracturing that require a long pressure-bearing sealing time.

[0005] Therefore, there is an urgent need to provide a sealing ring for a soluble bridge plug and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides a sealing ring for a soluble bridge plug and a preparation method thereof, which can significantly improve the strength of the sealing ring while delaying the early dissolution rate of the sealing ring, so that it can maintain a high tensile strength performance for a long time after being lowered into the well, and can dissolve quickly in the later stage.

[0007] To achieve the above object, the specific solution of the present invention is as follows: a method for preparing a sealing ring for a soluble bridge plug, comprising the following preparation steps: S1. The hollow mesoporous silica was dispersed in anhydrous ethanol, ZnCl2 was added, heated, ultrasonicated, and vacuum dried to obtain ZnCl2-loaded HMSN; S2. 3-carboxyphenylboronic acid and dextran were added to a PBS buffer solution to react to obtain a PBA-Dex complex solution, and then HMSN loaded with ZnCl2 was added, stirred, centrifuged, washed, and dried to obtain an HMSN-ZnCl2 composite material; S3. The dried pretreated polyglycolic acid, silane-modified glass fiber, bisoxazoline and acetyl tributyl citrate are mixed and kneaded, and then the HMSN-ZnCl2 composite material is added and mixed, injection molded, annealed, and aged to obtain a finished product.

[0008] By mixing and kneading silane-modified glass fibers with polyglycolic acid to form a polyglycolic acid-glass fiber composite material, the use of silane-modified glass fibers can not only enhance the interaction between the glass fibers, making the composite material more difficult to break and improving the tensile properties, but also facilitate the formation of a three-dimensional network reinforcement structure by mixing with polyglycolic acid. The thermal conductivity and nucleation effect of the glass fibers promote the crystallization of the polyglycolic acid matrix, thereby significantly enhancing the strength of the composite material, improving the tensile strength and bending strength, and meeting the high-pressure sealing requirements of the sealing ring. Although the introduction of glass fibers can improve the strength of the material, the glass fibers are difficult to degrade and always remain in the polyglycolic acid matrix, mixing with the polyglycolic acid to form a three-dimensional network, which is highly entangled and has a certain inhibitory effect on the degradation of the composite material, that is, the breakage of the molecular chain. This significantly reduces the dissolution rate of PGA, takes too long to dissolve, and dissolves unevenly, easily forming insoluble lumps, causing blockage and affecting secondary mining. By introducing ZnCl2 as a hydrolysis catalyst, the rapid dissolution of polyglycolic acid can be promoted. Zinc chloride is used to complex with the carbonyl group in polyglycolic acid, weakening the ester bond and accelerating the chain breaking process. The dissolution is also made more uniform, and the three-dimensional network gradually dissolves. The binding force between the large number of low molecular weight sub-chains and the glass fiber is weakened, causing the glass fiber to gradually fall off, thereby achieving rapid dissolution.

[0009] However, the addition of zinc chloride will cause rapid dissolution of the whole composite, which will result in a short time to maintain high-pressure sealing and may even cause premature dissolution. In addition, since zinc chloride is sensitive to water, the zinc chloride dispersed on the surface absorbs water during storage, promoting the hydrolysis of the polyglycolic acid in direct contact with it, making it not resistant to storage. At the same time, zinc chloride is directly mixed and kneaded with polyglycolic acid. At high temperatures, zinc chloride can easily reduce the hydrolysis activation energy of the polyglycolic acid ester bonds in contact with it, accelerate the degradation reaction, affect the mechanical properties of the composite material, and lead to a decrease in overall strength.

[0010] The present invention adopts hollow mesoporous silica to load ZnCl2, thereby providing a larger loading space, which can effectively prevent ZnCl2 from directly contacting with polyglycolic acid, slow down the release, avoid rapid dissolution in the early stage and premature failure, and reduce the influence of zinc chloride on polyglycolic acid during mixing. During storage, it can also prevent ZnCl2 from being dispersed on the surface of the sealing ring and being directly exposed to moisture in the air, thereby promoting the hydrolysis of polyglycolic acid. By using a PBA-Dex complex to block the mesopores of the ZnCl2-loaded HMSN and encapsulate it, the ZnCl2 in the hollow mesoporous silica can be better protected from moisture during storage. The encapsulation of the hollow mesoporous silica by the PBA-Dex complex can also improve its compatibility and bonding with the polyglycolic acid-glass fiber composite material. More importantly, the reversible borate ester bond formed by the reaction of 3-carboxyphenylboronic acid and dextran can remain stable at conventional natural temperatures. At high temperatures underground, generally above 45°C, or even if the temperature is not high enough, a slight adjustment of the pH around the sealing ring to acidic or alkaline can cause the borate ester bond to break, the encapsulating material to gradually dissolve, and the ZnCl2 loaded in the hollow mesoporous silica to gradually begin to be released. Due to the wrapping of PBA-Dex composite and the large loading space provided by hollow mesoporous silica, the release of ZnCl2 is delayed, so that zinc chloride cannot be directly exposed in the early stage, and the catalytic efficiency is low. At the same time, the high entanglement of glass fiber and polyglycolic acid and the strong binding force make the dissolution of the sealing ring relatively slow in the early stage. The combination significantly delays the hydrolysis process of the sealing ring in the early stage, so that the sealing ring can still maintain high tensile strength performance for a long time after being put into the well, and prolongs the high pressure sealing time. In the later stage, with the Zn 2+ The release of Zn gradually increases, the catalytic hydrolysis efficiency improves, and as the polyglycolic acid hydrolyzes, the surrounding acidity increases, further accelerating the 2+ The release and reaction interact with each other, making the later hydrolysis faster and faster, the sealing ring material fully and quickly hydrolyzes, and the hydrolysis products are environmentally friendly.

[0011] In addition, the addition of bisoxazoline chain extender can increase the molecular chain of polyglycolic acid, enhance the strength and cross-linking effect, and the addition of acetyl tributyl citrate can improve processing fluidity, reduce the mixing temperature of polyglycolic acid, protect polyglycolic acid, and avoid side reactions caused by excessively high mixing temperature that affect material properties.

[0012] Preferably, the hollow mesoporous silica is prepared by the following method: adding tetraethyl orthosilicate and hexadecyltrimethylammonium bromide into ammonia water, mixing, stirring, centrifuging and washing, and then calcining to remove the template.

[0013] Preferably, during the preparation of the hollow mesoporous silica, zirconium oxide is added to ammonia water, mixed, stirred for 24 hours, centrifuged and washed, and then calcined at 500° C. for 5 hours to obtain the hollow mesoporous silica; the concentration of the ammonia water is 5 wt %.

[0014] Hollow mesoporous silica is prepared by this method, and by adding zirconium oxide, it can provide more and more stable Zn 2+ The binding sites can also enhance the mechanical strength of the mesoporous material to resist external pressure, and improve the thermal stability to help maintain the material properties in high temperature environments and protect the load in the mesopores.

[0015] Preferably, in the step S1, after adding ZnCl2, heating to 55°C, ultrasonication at 300W power for 4 hours, and vacuum drying at 80°C for 6 hours to obtain HMSN loaded with ZnCl2.

[0016] Preferably, in step S2, 3-carboxyphenylboronic acid and dextran are added to a 0.1 M PBS buffer solution in a molar ratio of 1:2, the pH of the solution is maintained at 7.4, and the reaction is carried out for 12 hours to obtain a PBA-Dex complex solution, and then HMSN loaded with ZnCl2 is added, stirred at room temperature, centrifuged, washed, and freeze-dried to obtain an HMSN-ZnCl2 composite material.

[0017] By using PBS buffer solution and maintaining the pH of the solution environment, the reaction is conducive to the formation of reversible borate ester bonds, and the phosphate ions in the PBS buffer solution can stabilize the Zn 2+ , which is conducive to the rapid dynamic encapsulation of the PBA-Dex complex, and the preparation method is simple and efficient.

[0018] Preferably, the molecular weight of the dextran is MW=10kDa.

[0019] Preferably, in step S2, when adding HMSN loaded with ZnCl2, glycine is also added, and the pH of the solution is adjusted to 7.4, stirred at room temperature for 2 hours, centrifuged, washed with PBS buffer solution with a pH of 7.4, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0020] By adding glycine to the solution, it can act as a zinc ion stabilizer, further assisting in stabilizing zinc ions, avoiding hydrolysis, and maintaining subsequent catalytic activity; at the same time, glycine, as an amphoteric substance, is more conducive to stabilizing the pH environment.

[0021] Preferably, the polyglycolic acid is subjected to the following drying pretreatment: the polyglycolic acid granules are placed in a vacuum drying oven at a temperature of 75-85° C. for 6-8 hours, until the moisture content is less than 0.1%.

[0022] After sufficient drying, the subsequent introduction of moisture is avoided, which may cause partial hydrolysis of polyglycolic acid during the mixing process and affect the material properties.

[0023] Preferably, the silane-modified glass fiber is prepared by the following steps: placing the glass fiber in a 1wt% KH550 silane coupling agent aqueous solution, stirring and soaking it for 30 minutes, filtering it, placing it in a vacuum drying oven at a temperature of 125°C, and drying it for 40 minutes; the glass fiber is a mixture of chopped glass fiber and glass fiber powder, and the length of the chopped glass fiber is 0.5 mm.

[0024] By using silane coupling agent for modification, the compatibility and bonding degree of glass fiber with the material are made higher, and a mixture of chopped glass fiber and glass fiber powder is used. The chopped glass fiber is used to improve the tensile strength, while the glass fiber powder is more conducive to dispersion and mutual bonding, so that the bonding effect of the material is better. The 0.5mm chopped glass fiber is more conducive to backflow after dissolution and will not block the pipeline.

[0025] Preferably, in step S3, the polyglycolic acid, silane-modified glass fiber, bisoxazoline and acetyl tributyl citrate after drying pretreatment are added to an internal mixer, mixed and kneaded at 170°C and 120rpm for 10-15min, and then the HMSN-ZnCl2 composite material is added and mixed at 80rpm for 1-2min, injection molding is performed, and the barrel temperature is controlled at 170°C-180°C, the mold temperature is 40°C, the holding pressure is 60MPa, the cooling time is 30s, and then annealing is performed at 80°C for 2h and aging is performed at 35°C for 24h to obtain the finished product.

[0026] The internal stress is eliminated by annealing the material, and the crystallinity is regulated by aging to ensure the strength and stable performance of the sealing ring.

[0027] Another object of the present application is to provide a sealing ring for a soluble bridge plug, comprising the following raw materials in parts by mass: 70-80 parts of polyglycolic acid, 30-40 parts of silane-modified glass fiber, 0.5-1 part of bisoxazoline, 6-10 parts of acetyl tributyl citrate, and 8-12 parts of HMSN-ZnCl2 composite material; The HMSN-ZnCl2 composite material includes the following raw materials in parts by mass: 1.4 parts of 3-carboxyphenylboronic acid, 200 parts of dextran, 10-15 parts of HMSN loaded with ZnCl2, and 500-600 parts by volume of 0.1M PBS buffer solution; the HMSN loaded with ZnCl2 includes the following raw materials in parts by mass: 10-15 parts of hollow mesoporous silica and 0.4-0.8 parts of ZnCl2.

[0028] By adopting the above components and controlling the proportions of each component, it is more conducive to enhancing the overall material strength, while allowing the sealing ring to dissolve slowly in the early stage after being lowered into the well, but to dissolve quickly in the later stage, and the dissolution is more thorough and sufficient. The product after dissolution is environmentally friendly.

[0029] The above technical solution of the present invention includes at least the following beneficial effects: 1. The present invention utilizes silane-modified glass fibers and polyglycolic acid for compounding, which not only enhances the interaction between the glass fibers but also facilitates miscibility with polyglycolic acid to form a three-dimensional network reinforcement structure. The thermal conductivity and nucleation effect of the glass fibers are utilized to promote the crystallization of the polyglycolic acid matrix, thereby improving the tensile strength and flexural strength properties, thereby meeting the high-pressure sealing requirements of the sealing ring.

[0030] 2. The present invention promotes the rapid dissolution of polyglycolic acid by introducing ZnCl2, utilizes zinc chloride to complex with the carbonyl group in polyglycolic acid, weakens the ester bond, accelerates the chain scission process, and makes the dissolution more uniform. By using hollow mesoporous silica to load ZnCl2, direct contact between ZnCl2 and polyglycolic acid is avoided, the release is slowed down, and rapid dissolution in the early stage and premature failure are avoided. At the same time, the effect of ZnCl2 on polyglycolic acid is reduced during mixing. During storage, ZnCl2 is prevented from being directly exposed to air and moisture, which promotes the hydrolysis of polyglycolic acid and makes it less resistant to storage.

[0031] 3. The present invention forms a reversible borate bond through the reaction of 3-carboxyphenylboronic acid and dextran, which can remain stable at normal natural temperature. When the temperature is high underground or the pH environment is adjusted, the borate bond can be broken, the encapsulating material gradually dissolves, and ZnCl2 begins to be released. Due to the encapsulation of the PBA-Dex complex in the early stage and the large load space provided by the hollow mesoporous silica, the release of ZnCl2 is delayed. At the same time, the high degree of entanglement between the glass fiber and the polyglycolic acid has a strong bonding force. The early dissolution is relatively slow, so that the sealing ring can maintain a high tensile strength performance for a long time. In the later stage, as Zn 2+ The release of Zn gradually increases, the catalytic hydrolysis efficiency improves, and as the polyglycolic acid hydrolyzes, the surrounding acidity increases, further accelerating the 2+ The release and reaction of the glass fiber and the shedding of the glass fiber make the hydrolysis faster and faster, and the sealing ring material can be quickly and completely hydrolyzed in the later stage.

[0032] 4. The present invention uses a PBA-Dex complex to block the mesopores of HMSN loaded with ZnCl2 and wrap it, thereby preventing ZnCl2 from contacting moisture and catalytic hydrolysis during storage, and also improving the compatibility and bonding strength of hollow mesoporous silica and polyglycolic acid-glass fiber composite materials. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0034] Example 1 222 mL of tetraethyl orthosilicate (TEOS), 109 g of hexadecyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia water, and 0.6 g of zirconium oxide were mixed and stirred for 24 hours. The mixture was then centrifuged and washed, and then calcined at 500°C for 5 hours to remove the template (CTAB). This yielded hollow mesoporous silica (HMSN) with a diameter of approximately 50 nm. 10 g of the hollow mesoporous silica was dispersed in 500 mL of anhydrous ethanol, 0.5 g of ZnCl₂ was added, and the mixture was heated to 55°C, ultrasonicated at 300 W for 4 hours, and dried in a vacuum at 80°C for 6 hours to obtain ZnCl₂-loaded HMSN.

[0035] 3-Carboxyphenylboronic acid and dextran were added to 500 mL of 0.1 M PBS buffer solution in a molar ratio of 1:2, that is, 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW = 10 kDa), and the pH of the solution was maintained at 7.4. The reaction was carried out for 12 hours to obtain a PBA-Dex complex solution. 10 g of ZnCl2-loaded HMSN and 0.2 g of glycine were then added to adjust the pH of the solution to 7.4. The solution was stirred at room temperature for 2 hours, centrifuged, washed three times with a PBS buffer solution with a pH of 7.4, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0036] Polyglycolic acid (PGA) pellets were dried in a vacuum drying oven to a moisture content of <0.1% at 75°C for 8 hours before use. A mixture of 0.5 mm chopped glass fiber and glass fiber powder in a 1:1 mass ratio was added to a 1 wt% KH550 silane coupling agent aqueous solution, stirred, and soaked for 30 minutes. The mixture was filtered and dried in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fiber. The dried 70g polyglycolic acid, 35g silane-modified glass fiber, 0.5 bisoxazoline (BOZ) and 6g acetyl tributyl citrate (ATBC) were added into an internal mixer and mixed at 170°C and 120rpm for 10min. Then 8g HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1min. Injection molding was performed with the barrel temperature at 170°C-180°C, the mold temperature at 40°C, the holding pressure at 60MPa, the cooling time at 30s, and then annealing at 80°C for 2h and aging at 35°C for 24h to obtain a finished sealing ring.

[0037] Example 2 222 mL of tetraethyl orthosilicate (TEOS), 109 g of hexadecyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia water, and 0.6 g of zirconium oxide were mixed and stirred for 24 hours. The mixture was then centrifuged and washed, and then calcined at 500°C for 5 hours to remove the template (CTAB). This yielded hollow mesoporous silica (HMSN) with a diameter of approximately 50 nm. 15 g of the hollow mesoporous silica was dispersed in 500 mL of anhydrous ethanol, 0.8 g of ZnCl₂ was added, and the mixture was heated to 55°C, ultrasonicated at 300 W for 4 hours, and dried in a vacuum at 80°C for 6 hours to obtain ZnCl₂-loaded HMSN.

[0038] 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW = 10 kDa) were added to 600 mL of 0.1 M PBS buffer solution, the pH of the solution was maintained at 7.4, and the reaction was carried out for 12 h to obtain a PBA-Dex complex solution. 15 g of ZnCl2-loaded HMSN and 0.3 g of glycine were then added to adjust the pH of the solution to 7.4. The solution was stirred at room temperature for 2 h, centrifuged, washed three times with a pH 7.4 PBS buffer solution, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0039] Polyglycolic acid (PGA) pellets were dried in a vacuum drying oven to a moisture content of <0.1% at 85°C for 6 hours before use. 0.5 mm chopped glass fiber and glass fiber powder were mixed in a 1:1 mass ratio and placed in a 1 wt% KH550 silane coupling agent aqueous solution. The mixture was stirred and soaked for 30 minutes, filtered, and dried in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fiber. Add 80g of dried polyglycolic acid, 40g of silane-modified glass fiber, 1g of bisoxazoline (BOZ) and 10g of acetyl tributyl citrate (ATBC) into an internal mixer and mix at 170°C and 120rpm for 15min. Then add 12g of HMSN-ZnCl2 composite material and mix at 80rpm for 2min. Injection molding is carried out, and the barrel temperature is controlled at 170°C-180°C, the mold temperature is 40°C, the holding pressure is 60MPa, the cooling time is 30s, and then annealing is carried out at 80°C for 2h and aging is carried out at 35°C for 24h to obtain a finished sealing ring.

[0040] Example 3 222 mL of tetraethyl orthosilicate (TEOS), 109 g of hexadecyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia water, and 0.6 g of zirconium oxide were mixed and stirred for 24 hours. The mixture was then centrifuged and washed, and then calcined at 500°C for 5 hours to remove the template (CTAB). This yielded hollow mesoporous silica (HMSN) with a diameter of approximately 50 nm. 10 g of the hollow mesoporous silica was dispersed in 500 mL of anhydrous ethanol, 0.4 g of ZnCl₂ was added, and the mixture was heated to 55°C, ultrasonicated at 300 W for 4 hours, and dried in a vacuum at 80°C for 6 hours to obtain ZnCl₂-loaded HMSN.

[0041] 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW = 10 kDa) were added to 550 mL of 0.1 M PBS buffer solution, the pH of the solution was maintained at 7.4, and the reaction was carried out for 12 h to obtain a PBA-Dex complex solution. 12 g of ZnCl2-loaded HMSN and 0.2 g of glycine were then added to adjust the pH of the solution to 7.4. The solution was stirred at room temperature for 2 h, centrifuged, washed three times with a pH 7.4 PBS buffer solution, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0042] Polyglycolic acid (PGA) pellets were dried in a vacuum drying oven to a moisture content of <0.1% at 80°C for 7 hours before use. A mixture of 0.5 mm chopped glass fiber and glass fiber powder in a 1:1 mass ratio was added to a 1 wt% KH550 silane coupling agent aqueous solution, stirred, and soaked for 30 minutes. The mixture was filtered and dried in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fiber. 75g of dried polyglycolic acid, 30g of silane-modified glass fiber, 0.6g of bisoxazoline (BOZ) and 8g of acetyl tributyl citrate (ATBC) were added into an internal mixer and mixed at 170°C and 120rpm for 12min. Then 10g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1min. Injection molding was performed with the barrel temperature at 170°C-180°C, the mold temperature at 40°C, the holding pressure at 60MPa, the cooling time at 30s, and then annealing at 80°C for 2h and aging at 35°C for 24h to obtain a finished sealing ring.

[0043] Example 4 222 mL of tetraethyl orthosilicate (TEOS), 109 g of hexadecyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia water, and 0.6 g of zirconium oxide were mixed and stirred for 24 hours. The mixture was then centrifuged and washed, and then calcined at 500°C for 5 hours to remove the template (CTAB). This yielded hollow mesoporous silica (HMSN) with a diameter of approximately 50 nm. 12 g of the hollow mesoporous silica was dispersed in 500 mL of anhydrous ethanol, and 0.6 g of ZnCl2 was added. The mixture was heated to 55°C, ultrasonicated at 300 W for 4 hours, and dried in a vacuum at 80°C for 6 hours to obtain ZnCl2-loaded HMSN.

[0044] 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW = 10 kDa) were added to 550 mL of 0.1 M PBS buffer solution, the pH of the solution was maintained at 7.4, and the reaction was carried out for 12 hours to obtain a PBA-Dex complex solution. 13 g of ZnCl2-loaded HMSN and 0.2 g of glycine were then added to adjust the pH of the solution to 7.4. The solution was stirred at room temperature for 2 hours, centrifuged, washed three times with a pH 7.4 PBS buffer solution, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0045] Polyglycolic acid (PGA) pellets were dried in a vacuum drying oven to a moisture content of <0.1% at 80°C for 7 hours before use. A mixture of 0.5 mm chopped glass fiber and glass fiber powder in a 1:1 mass ratio was added to a 1 wt% KH550 silane coupling agent aqueous solution, stirred, and soaked for 30 minutes. The mixture was filtered and dried in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fiber. Add 75g of dried polyglycolic acid, 35g of silane-modified glass fiber, 0.7g of bisoxazoline (BOZ) and 9g of acetyl tributyl citrate (ATBC) into an internal mixer and mix at 170°C and 120rpm for 12min. Then add 12g of HMSN-ZnCl2 composite material and mix at 80rpm for 1.5min. Injection molding is carried out, and the barrel temperature is controlled at 170°C-180°C, the mold temperature is 40°C, the holding pressure is 60MPa, the cooling time is 30s, and then annealing is carried out at 80°C for 2h and aging is carried out at 35°C for 24h to obtain a finished sealing ring.

[0046] Example 5 222 mL of tetraethyl orthosilicate (TEOS), 109 g of hexadecyltrimethylammonium bromide (CTAB), and 300 mL of 5 wt% ammonia water were mixed and stirred for 24 hours. The mixture was then centrifuged and washed, and then calcined at 500°C for 5 hours to remove the template (CTAB), resulting in hollow mesoporous silica (HMSN) with a diameter of approximately 50 nm. 10 g of the hollow mesoporous silica was dispersed in 500 mL of anhydrous ethanol, 0.5 g of ZnCl₂ was added, and the mixture was heated to 55°C, ultrasonicated at 300 W for 4 hours, and dried in a vacuum at 80°C for 6 hours to obtain ZnCl₂-loaded HMSN.

[0047] 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW = 10 kDa) were added to 550 mL of 0.1 M PBS buffer solution, the pH of the solution was maintained at 7.4, and the reaction was carried out for 12 h to obtain a PBA-Dex complex solution. 12 g of ZnCl2-loaded HMSN was then added, the pH of the solution was adjusted to 7.4, stirred at room temperature for 2 h, centrifuged, washed three times with a pH 7.4 PBS buffer solution, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

[0048] Polyglycolic acid (PGA) pellets were dried in a vacuum drying oven to a moisture content of <0.1% at 80°C for 7 hours before use. A mixture of 0.5 mm chopped glass fiber and glass fiber powder in a 1:1 mass ratio was added to a 1 wt% KH550 silane coupling agent aqueous solution, stirred, and soaked for 30 minutes. The mixture was filtered and dried in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fiber. Add 75g of dried polyglycolic acid, 35g of silane-modified glass fiber, 0.7g of bisoxazoline (BOZ) and 9g of acetyl tributyl citrate (ATBC) into an internal mixer and mix at 170°C and 120rpm for 12min. Then add 12g of HMSN-ZnCl2 composite material and mix at 80rpm for 1.5min. Injection molding is carried out, and the barrel temperature is controlled at 170°C-180°C, the mold temperature is 40°C, the holding pressure is 60MPa, the cooling time is 30s, and then annealing is carried out at 80°C for 2h and aging is carried out at 35°C for 24h to obtain a finished sealing ring.

[0049] The present invention also sets the following comparative examples and conducts relevant tests Comparative Example 1 Compared with Example 4, the only difference is that the HMSN-ZnCl2 composite material is not prepared, but 0.6g ZnCl2 is directly added for mixing. The other components and preparation steps are exactly the same to obtain a finished sealing ring.

[0050] Comparative Example 2 Compared with Example 4, the only difference is that the PBA-Dex complex solution is not prepared, and HMSN loaded with ZnCl2 is used instead of the HMSN-ZnCl2 composite material. The other components and preparation steps are exactly the same to obtain a finished sealing ring.

[0051] Comparative Example 3 Compared with Example 4, the only difference is that the ZnCl2 component is not added, and the other components and preparation steps are exactly the same to obtain a finished sealing ring.

[0052] Performance testing (I) Tensile strength and elongation at break test: The sealing rings obtained in Examples 1-5 of the present invention and Comparative Examples 1-3 were subjected to tensile strength and elongation at break tests in accordance with the standard GB / T 1040.2-2022. Each group of samples was tested three times, and the average value was calculated. The test results are summarized in Table 1 below.

[0053] Bending strength test: The sealing rings obtained in Examples 1-5 and Comparative Examples 1-3 of the present invention were subjected to bending strength test in accordance with GB / T 9341-2008. Each group of samples was tested three times, and the average value was calculated. The test results are summarized in Table 1 below.

[0054] It can be seen from the test results in Table 1 above that the sealing ring products obtained in Examples 1-5 of the present invention have excellent tensile strength and bending strength, can meet high pressure requirements, and have high elongation at break and good toughness.

[0055] Compared with Example 4, Comparative Example 1 did not use the HMSN-ZnCl2 composite material, but directly added ZnCl2 during the mixing process, resulting in a significant decrease in the overall tensile strength and flexural strength, and a significant decrease in the elongation at break. This indicates that during the mixing process, ZnCl2 directly contacts the composite material, which easily causes partial degradation of the polyglycolic acid and a decrease in the overall compatibility and bonding strength, significantly affecting the mechanical properties of the composite material. Comparative Example 2 was not wrapped with the PBA-Dex composite, and various mechanical properties also decreased. Comparative Example 3 did not add the ZnCl2 component and had excellent mechanical properties.

[0056] Solubility test: The same 0.3% wt KCl aqueous solution was added to the same test tank and the solution temperature was maintained at 50°C. The sealing rings obtained in Examples 1-5 of the present invention and Comparative Examples 1-3 were respectively placed in the test tank for soaking. A portion was taken out after soaking for 12 hours, 24 hours, and 36 hours, respectively, and placed in a drying oven for drying for 6 hours before the tensile strength was tested. At the same time, the time required for the soaked sealing ring to be completely dissolved into fine fragments was observed every day, as well as whether there were insoluble lumps. The test results are summarized as shown in Table 2 below.

[0057] As can be seen from the test results of Table 2 above, the sealing ring products obtained by the embodiments of the present invention 1-5 are in the immersion process of simulating downhole environment, and early stage dissolution is slow, and it is possible to maintain a tensile strength of more than 112.6MPa within 36h, meet the high pressure-bearing sealing strength requirement for a long time, and the tensile strength in 24h exceeds 142.0MPa, meet the ultra-high pressure-bearing sealing strength requirement of 24h for a long time, and the dissolution days can be controlled within 8 days, illustrating that the release of catalysts in the later stage is faster and faster, so that the overall material can be quickly dissolved and fully, there is no insoluble block, it will not cause pipeline blockage, and secondary mining is not affected. Wherein, embodiment 4 is optimal solution, and after soaking for 36h, the high tensile strength of 135.8MPa can still be maintained, and in embodiment 5, zirconium oxide mixing is not added during the preparation of hollow mesoporous silica, glycine is not added in the solution when carrying out PBA-Dex compound wrapping, causing the load effect of zinc chloride not to be as good as other embodiments, so that the sealing ring overall strength is slightly reduced, and early stage dissolution is also faster than other embodiments, and tensile strength declines more.

[0058] Compared with Example 4, in Comparative Example 1, ZnCl2 is directly added during the mixing process, and ZnCl2 is directly exposed on the surface of the material, resulting in high catalytic efficiency and the lowest overall dissolution days of only 6 days. However, since the catalyst has no protection, it begins to dissolve rapidly when placed in water, resulting in a significant decrease in tensile strength after only 12 hours of immersion, which cannot meet the high pressure sealing requirements for a long time. Although Comparative Example 2 does not use PBA-Dex composite wrapping, it uses hollow mesoporous silica to load zinc chloride, which can delay the release of the catalyst to a certain extent. Therefore, the rate of decrease in tensile strength after immersion is significantly slower than that of Comparative Example 1, but there is still a lot of gap compared with Example 4. Although Comparative Example 3 can maintain ultra-high tensile strength and meet the long-term high pressure sealing effect, it lacks a catalyst, dissolves slowly, and dissolves for more than 15 days. In addition, there are insoluble lumps, which are easy to clog the pipeline in the later stage, affecting secondary development.

[0059] The above are preferred embodiments of the present invention. For ordinary technicians in this technical field, several improvements and modifications made without departing from the principles of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing a sealing ring for a soluble bridge plug, characterized in that: The method comprises the following preparation steps: S1. The hollow mesoporous silica was dispersed in anhydrous ethanol, ZnCl2 was added, heated, ultrasonicated, and vacuum dried to obtain ZnCl2-loaded HMSN; S2. 3-carboxyphenylboronic acid and dextran were added to a PBS buffer solution to react to obtain a PBA-Dex complex solution, and then HMSN loaded with ZnCl2 was added, stirred, centrifuged, washed, and dried to obtain an HMSN-ZnCl2 composite material; S3. The dried pretreated polyglycolic acid, silane-modified glass fiber, bisoxazoline and acetyl tributyl citrate are mixed and kneaded, and then the HMSN-ZnCl2 composite material is added and mixed, injection molded, annealed, and aged to obtain a finished product.

2. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: The hollow mesoporous silica is prepared by the following method: adding tetraethyl orthosilicate and hexadecyltrimethylammonium bromide into ammonia water, mixing, stirring, centrifuging and washing, and then calcining to remove the template agent.

3. The method for preparing a sealing ring for a soluble bridge plug according to claim 2, characterized in that: During the preparation of the hollow mesoporous silica, zirconium oxide is added to ammonia water, mixed, stirred for 24 hours, centrifuged and washed, and then calcined at 500° C. for 5 hours to obtain the hollow mesoporous silica; the concentration of the ammonia water is 5 wt %.

4. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: In the step S1, after adding ZnCl2, heating to 55°C, ultrasonication at 300W power for 4 hours, and vacuum drying at 80°C for 6 hours to obtain HMSN loaded with ZnCl2.

5. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: In step S2, 3-carboxyphenylboronic acid and dextran are added to a 0.1M PBS buffer solution in a molar ratio of 1:2, the pH of the solution is maintained at 7.4, and the reaction is carried out for 12 hours to obtain a PBA-Dex complex solution, and then HMSN loaded with ZnCl2 is added, stirred at room temperature, centrifuged, washed, and freeze-dried to obtain an HMSN-ZnCl2 composite material.

6. The method for preparing a sealing ring for a soluble bridge plug according to claim 5, characterized in that: The molecular weight of the dextran is MW=10 kDa; in the step S2, when the ZnCl2-loaded HMSN is added, glycine is also added, and the pH of the solution is adjusted to 7.4, stirred at room temperature for 2 hours, centrifuged, washed with a PBS buffer solution with a pH of 7.4, and freeze-dried below 0°C to obtain an HMSN-ZnCl2 composite material.

7. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: The polyglycolic acid is subjected to the following drying pretreatment: the polyglycolic acid granules are placed in a vacuum drying oven at a temperature of 75-85° C. for 6-8 hours, until the moisture content is less than 0.1%.

8. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: The silane-modified glass fiber is prepared by the following steps: placing the glass fiber in a 1wt% KH550 silane coupling agent aqueous solution, stirring and soaking it for 30 minutes, filtering it, placing it in a vacuum drying oven at a temperature of 125°C, and drying it for 40 minutes; the glass fiber is a mixture of chopped glass fiber and glass fiber powder, and the length of the chopped glass fiber is 0.5 mm.

9. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: In the step S3, the polyglycolic acid, silane-modified glass fiber, bisoxazoline and acetyl tributyl citrate that have undergone drying pretreatment are added to an internal mixer, mixed and kneaded at 170°C and 120 rpm for 10-15 minutes, and then the HMSN-ZnCl2 composite material is added and kneaded at 80 rpm for 1-2 minutes, and injection molding is performed. The barrel temperature is controlled at 170°C-180°C, the mold temperature is 40°C, the holding pressure is 60 MPa, the cooling time is 30 seconds, and then annealing is performed at 80°C for 2 hours and aging is performed at 35°C for 24 hours to obtain a finished product.

10. A sealing ring for a soluble bridge plug, characterized by: The soluble bridge plug sealing ring is prepared by the preparation method according to any one of claims 1 to 9, comprising the following raw materials in parts by weight: 70-80 parts of polyglycolic acid, 30-40 parts of silane-modified glass fiber, 0.5-1 part of bisoxazoline, 6-10 parts of acetyl tributyl citrate, and 8-12 parts of HMSN-ZnCl2 composite material; The HMSN-ZnCl2 composite material includes the following raw materials in parts by mass: 1.4 parts of 3-carboxyphenylboronic acid, 200 parts of dextran, 10-15 parts of HMSN loaded with ZnCl2, and 500-600 parts by volume of 0.1M PBS buffer solution; the HMSN loaded with ZnCl2 includes the following raw materials in parts by mass: 10-15 parts of hollow mesoporous silica and 0.4-0.8 parts of ZnCl2.

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