A soluble bridge plug sealing ring and its preparation method

Abstract

This invention provides a soluble bridge plug sealing ring and its preparation method, belonging to the field of sealing material technology. The preparation steps include: S1. Dispersing hollow mesoporous silica in anhydrous ethanol, adding ZnCl2, heating, ultrasonicating, and vacuum drying to obtain ZnCl2-loaded HMSN; S2. Adding 3-carboxyphenylboronic acid and dextran to PBS buffer solution for reaction to obtain a PBA-Dex composite solution, then adding ZnCl2-loaded HMSN, stirring, centrifuging, washing, and drying to obtain an HMSN-ZnCl2 composite material; S3. Mixing and kneading polyglycolic acid, silane-modified glass fiber, bisoxazoline, and tributyl acetylacetic acid, then adding the HMSN-ZnCl2 composite material for further mixing, injection molding, annealing, and curing to obtain the finished product. The soluble bridge plug sealing ring prepared by this invention can significantly improve strength while slowing down the initial dissolution rate, allowing it to maintain high tensile strength for a longer period after being installed in the well, while also dissolving rapidly in the later stages.

Description

Technical Field

[0001] This invention relates to the field of sealing materials technology, specifically to a soluble bridge plug sealing ring and its preparation method. Background Technology

[0002] With the development and advancement of soluble bridge plugs, there are more and more materials available for manufacturing soluble bridge plugs. Among the important components of soluble bridge plugs, the sealing ring, which plays a pressure-bearing and sealing role, is of great importance. Therefore, the selection and preparation of the sealing ring material are crucial.

[0003] Currently, the main materials used to manufacture soluble bridge plug seals are polymers and magnesium-aluminum alloys. While magnesium-aluminum alloys are favored for their high strength, solubility, and certain plasticity, especially in the widespread use of soluble bridge plugs in staged fracturing, their dissolution is generally incomplete, leaving behind hard residues. Furthermore, since staged fracturing requires a large number of bridge plugs, residual pressure buildup can clog pipelines, reducing oil and gas production and impacting secondary extraction. Polymer materials, such as polyglycolic acid (PGA), have excellent degradation properties and their hydrolysis products are environmentally friendly, making them a viable alternative to magnesium-aluminum alloys in addressing the incomplete dissolution issue. However, when facing the high pressure resistance requirements of deep water wells, the strength of PGA materials is insufficient. Additionally, PGA's excellent degradation properties and rapid dissolution can lead to short pressure-bearing times and premature dissolution, making it unsuitable for prolonged pressure sealing.

[0004] For example, patent application publication number CN118667311A discloses a polyglycolic acid composite material and its molded articles and soluble bridge plugs, including: a blend formed of 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 through the compatibilizer, thereby enhancing the toughness of the material without affecting the degradation rate of the polyglycolic acid composite material, the strength of the composite material obtained by this solution is not high enough and still cannot meet the requirements of high-pressure downhole. Moreover, the dissolution rate throughout the process is relatively fast, resulting in a short period of maintaining high pressure resistance in the early stage, and it is even prone to premature dissolution in complex environments, making it difficult to meet the current requirement of long pressure resistance and sealing time for staged fracturing.

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

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

[0007] To achieve the above objectives, the specific solution of the present invention is as follows: a method for preparing a soluble bridge plug sealing ring, comprising the following preparation steps:

[0008] S1. Hollow mesoporous silica was dispersed in anhydrous ethanol, ZnCl2 was added, heated, sonicated, and vacuum dried to obtain ZnCl2-loaded HMSN;

[0009] S2. Add 3-carboxyphenylboronic acid and dextran to PBS buffer solution and react to obtain PBA-Dex complex solution. Then add HMSN loaded with ZnCl2, stir, centrifuge, wash, and dry to obtain HMSN-ZnCl2 composite material.

[0010] S3. The pre-treated polyglycolic acid, silane-modified glass fiber, bisoxazoline and tributyl acetyl citrate are mixed and kneaded, and then HMSN-ZnCl2 composite material is added and kneaded. The mixture is then injection molded, annealed and cured to obtain the finished product.

[0011] By mixing silane-modified glass fibers with polyglycolic acid (PGA) in a intensive kneading process, a PGA-glass fiber composite material is formed. The silane-modified glass fibers enhance the interaction between the glass fibers, making the composite material less prone to breakage and improving tensile strength. They also facilitate the formation of a three-dimensional network reinforcement structure with PGA. Furthermore, the thermal conductivity and nucleation properties of the glass fibers promote the crystallization of the PGA matrix, significantly enhancing the composite material's strength, tensile and flexural strength, and meeting the high-pressure sealing requirements of the sealing ring. While the introduction of glass fibers improves the material's strength, the glass fibers are difficult to degrade and remain within the PGA matrix, forming a highly entangled three-dimensional network. This network hinders the degradation of the composite material, i.e., the breakage of the molecular chains. This significantly reduces the dissolution rate of PGA, resulting in prolonged and uneven dissolution, easily leading to the formation of insoluble lumps, causing blockages, and affecting secondary mining. By introducing ZnCl2 as a hydrolysis catalyst, the rapid dissolution of polyglycolic acid can be promoted. Zinc chloride complexes with the carbonyl group in polyglycolic acid, weakening the ester bond and accelerating the chain breaking process. This also makes the dissolution more uniform, and the three-dimensional network gradually disintegrates. 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.

[0012] However, the addition of zinc chloride leads to rapid overall dissolution, which also results in a very short time to maintain a high-pressure seal. Premature dissolution may also occur. Furthermore, because zinc chloride is sensitive to water, the zinc chloride dispersed on the surface absorbs water during storage, promoting the hydrolysis of polyglycolic acid in direct contact with it, making it less resistant to storage. At the same time, when zinc chloride is directly mixed and kneaded with polyglycolic acid, zinc chloride can easily reduce the hydrolysis activation energy of the polyglycolic acid bonds in contact with it at high temperatures, accelerating the degradation reaction, affecting the mechanical properties of the composite material, and leading to a decrease in overall strength.

[0013] This invention utilizes hollow mesoporous silica to support ZnCl2, providing a larger loading space. This effectively prevents ZnCl2 from directly contacting polyglycolic acid, slowing down its release and avoiding rapid dissolution and premature failure in the early stages. It also reduces the impact of zinc chloride on polyglycolic acid during mixing and prevents ZnCl2 from dispersing on the surface of the sealing ring during storage, thus avoiding direct exposure to air and moisture, which would promote the hydrolysis of polyglycolic acid. Furthermore, by using a PBA-Dex composite to seal and encapsulate the mesopores of the ZnCl2-loaded HMSN, the ZnCl2 inside the hollow mesoporous silica is better prevented from coming into contact with moisture during storage. At the same time, the encapsulation of the hollow mesoporous silica by the PBA-Dex composite also improves its compatibility and bonding strength with polyglycolic acid-glass fiber composites. More importantly, the reversible borate ester bond formed by the reaction of 3-carboxyphenylboronic acid and dextran can remain stable at normal ambient temperatures. However, at high downhole temperatures, generally above 45°C, or even if the temperature is not high enough, simply adjusting 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. The encapsulation of the PBA-Dex composite and the large loading space provided by the hollow mesoporous silica delay the release of ZnCl2, preventing zinc chloride from being fully exposed in the early stages, resulting in lower catalytic efficiency. Simultaneously, the high degree of entanglement between the glass fiber and polyglycolic acid creates strong bonding, slowing the initial dissolution of the sealing ring. Overall, this significantly delays the initial hydrolysis process of the sealing ring, allowing it to maintain high tensile strength for a longer period after installation, thus extending the duration of high-pressure sealing. Later, as ZnCl2 releases further, the hydrolysis of the sealing ring continues. 2+ The release of Zn gradually increases, the catalytic hydrolysis efficiency improves, and with the hydrolysis of polyglycolic acid, the surrounding acidity increases, further accelerating the process. 2+ The release and reaction of the substances interact with each other, making the hydrolysis process faster and faster in the later stages. The sealing ring material is fully and quickly hydrolyzed, and the hydrolysis products are environmentally friendly.

[0014] In addition, the addition of bisoxazoline chain extender can improve the molecular chain of polyglycolic acid, enhance its strength and cross-linking effect, and the addition of tributyl acetylacetate can improve processing fluidity, reduce the mixing temperature of polyglycolic acid, protect polyglycolic acid, and prevent side reactions from occurring at excessively high mixing temperatures that could affect material properties.

[0015] Preferably, the hollow mesoporous silica is prepared by the following method: tetraethyl orthosilicate and hexadecyltrimethylammonium bromide are added to ammonia water, mixed, stirred, centrifuged and washed, and then calcined to remove the template agent to obtain the silica.

[0016] Preferably, in the preparation process of the hollow mesoporous silica, zirconium oxide is added to ammonia water for mixing, stirring for 24 hours, centrifuging and washing, and then calcining at 500°C for 5 hours to obtain the product; the concentration of the ammonia water is 5 wt%.

[0017] Hollow mesoporous silica was prepared using this method, and by adding zirconium oxide, more and more stable Zn could be provided. 2+ Binding sites can also enhance the mechanical strength of mesoporous materials to resist external pressure and improve thermal stability, so as to maintain material properties in high-temperature environments and protect the loads inside the mesopores.

[0018] Preferably, in step S1, after adding ZnCl2, the mixture is heated to 55°C, ultrasonicated at 300W for 4 hours, and vacuum dried at 80°C for 6 hours to obtain ZnCl2-loaded HMSN.

[0019] Preferably, in step S2, 3-carboxyphenylboronic acid and dextran are added to 0.1M PBS buffer solution at 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. Then, HMSN loaded with ZnCl2 is added, stirred at room temperature, centrifuged, washed, and freeze-dried to obtain the HMSN-ZnCl2 composite material.

[0020] By using a PBS buffer solution and maintaining the pH of the solution environment, the formation of reversible borate ester bonds in the reaction is facilitated, and the phosphate ions in the PBS buffer solution can stabilize Zn. 2+ This facilitates rapid dynamic encapsulation of the PBA-Dex complex, and the preparation method is simple and efficient.

[0021] Preferably, the molecular weight of the dextran is MW=10kDa.

[0022] 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. The mixture is stirred at room temperature for 2 hours, centrifuged, washed with PBS buffer solution at pH 7.4, and freeze-dried below 0°C to obtain the HMSN-ZnCl2 composite material.

[0023] By adding glycine to the solution, it can act as a zinc ion stabilizer, further assisting in stabilizing zinc ions, preventing hydrolysis, and maintaining subsequent catalytic activity; at the same time, as an amphoteric substance, glycine is more conducive to stabilizing the pH environment.

[0024] Preferably, the polyglycolic acid undergoes the following drying pretreatment: the polyglycolic acid granules are placed in a vacuum drying oven at a temperature of 75-85°C and dried for 6-8 hours until the moisture content is <0.1%.

[0025] Thorough drying is essential to prevent the introduction of moisture later, which could cause partial hydrolysis of polyglycolic acid during the mixing process and affect the material's properties.

[0026] Preferably, the silane-modified glass fiber is prepared by the following steps: glass fiber is placed in a 1wt% KH550 silane coupling agent aqueous solution and stirred and soaked for 30 min, filtered, placed in a vacuum drying oven at 125℃ and dried for 40 min; 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.

[0027] By using silane coupling agents for modification, the compatibility and bonding between glass fiber and the material are improved. A mixture of chopped glass fiber and glass fiber powder is used. Chopped glass fiber helps to improve tensile strength, while glass fiber powder is easier to disperse and bond together, resulting in better material bonding. In addition, 0.5mm chopped glass fiber is easier to dissolve and return to the source, without clogging the pipe.

[0028] Preferably, in step S3, the pre-treated polyglycolic acid, silane-modified glass fiber, bisoxazoline, and tributyl acetyl citrate are added to a mixer and mixed at 170°C and 120 rpm for 10-15 minutes. Then, the HMSN-ZnCl2 composite material is added and mixed at 80 rpm for 1-2 minutes. The mixture is then injection molded, with the barrel temperature controlled at 170°C-180°C, the mold temperature at 40°C, the holding pressure at 60 MPa, and the cooling time at 30 seconds. Finally, the mixture is annealed at 80°C for 2 hours and cured at 35°C for 24 hours to obtain the finished product.

[0029] By annealing the material to eliminate internal stress and by ripening to control the crystallinity, the strength and performance stability of the sealing ring can be guaranteed.

[0030] Another objective of this application is to provide a sealing ring for a soluble bridge plug, comprising the following parts by weight of raw materials: 70-80 parts of polyglycolic acid, 30-40 parts of silane-modified glass fiber, 0.5-1 part of bisoxazoline, 6-10 parts of tributyl acetylacetate, and 8-12 parts of HMSN-ZnCl2 composite material.

[0031] The HMSN-ZnCl2 composite material comprises the following raw materials in parts by weight: 1.4 parts 3-carboxyphenylboronic acid, 200 parts dextran, 10-15 parts ZnCl2-loaded HMSN, and 500-600 parts by volume of 0.1M PBS buffer solution; the ZnCl2-loaded HMSN comprises the following raw materials in parts by weight: 10-15 parts hollow mesoporous silica and 0.4-0.8 parts ZnCl2.

[0032] By using the above-mentioned components and controlling the proportions of each component, it is more conducive to enhancing the overall material strength, while enabling the sealing ring to dissolve slowly in the early stage after being lowered into the well, and to dissolve quickly and thoroughly in the later stage. The dissolved product is environmentally friendly and environmentally friendly.

[0033] The above-described technical solution of the present invention has at least the following beneficial effects:

[0034] 1. This invention uses silane-modified glass fiber to composite with polyglycolic acid, which can enhance the interaction between glass fibers and facilitate the formation of a three-dimensional network reinforcement structure with polyglycolic acid. The thermal conductivity and nucleation effect of glass fiber promote the crystallization of polyglycolic acid matrix, thereby improving tensile strength and flexural strength, and meeting the high pressure sealing requirements of the sealing ring.

[0035] 2. This invention promotes the rapid dissolution of polyglycolic acid by introducing ZnCl2. Zinc chloride complexes with the carbonyl groups in polyglycolic acid, weakening the ester bonds and accelerating the chain-breaking process, resulting in more uniform dissolution. Furthermore, by using hollow mesoporous silica to support ZnCl2, direct contact between ZnCl2 and polyglycolic acid is avoided, slowing down the release and preventing rapid dissolution and premature failure in the early stages. Simultaneously, the impact of ZnCl2 on polyglycolic acid is reduced during mixing, and during storage, direct exposure of ZnCl2 to air and moisture is prevented, as this promotes hydrolysis of polyglycolic acid and reduces its shelf life.

[0036] 3. This invention utilizes the reaction of 3-carboxyphenylboronic acid and dextran to form reversible borate ester bonds, which remain stable under normal ambient temperatures. However, at high downhole temperatures or with pH adjustments, these bonds break, causing the encapsulating material to gradually dissolve and ZnCl2 to be released. The initial encapsulation by the PBA-Dex composite and the large loading space provided by the hollow mesoporous silica delay the release of ZnCl2. Simultaneously, the high degree of entanglement between the glass fiber and polyglycolic acid results in strong bonding, leading to slow initial dissolution and allowing the sealing ring to maintain high tensile strength for an extended period. Later, as ZnCl2 releases... 2+ The release of Zn gradually increases, the catalytic hydrolysis efficiency improves, and with the hydrolysis of polyglycolic acid, the surrounding acidity increases, further accelerating the hydrolysis. 2+The release and reaction of the material, as well as the shedding of glass fibers, accelerate the hydrolysis process, allowing the sealing ring material to be rapidly and completely hydrolyzed in the later stages.

[0037] 4. This invention uses PBA-Dex composite to block and encapsulate the mesopores of ZnCl2-loaded HMSN, preventing ZnCl2 from coming into contact with moisture and catalytically hydrolyzing during storage. It also improves the compatibility and bonding strength between hollow mesoporous silica and polyglycolic acid-glass fiber composite material. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0039] Example 1

[0040] 222 mL of tetraethyl orthosilicate (TEOS), 109 g of cetyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia, and 0.6 g of zirconium oxide were mixed and stirred for 24 h. After centrifugation and washing, the mixture was calcined at 500 °C for 5 h to remove the template agent (CTAB), yielding 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, and 0.5 g of ZnCl2 was added. The mixture was heated to 55 °C, sonicated at 300 W for 4 h, and then vacuum dried at 80 °C for 6 h to obtain ZnCl2-loaded HMSN.

[0041] 3-Carboxyphenylboronic acid and dextran were mixed at a molar ratio of 1:2, i.e., 1.4 g of 3-carboxyphenylboronic acid and 200 g of dextran (MW=10 kDa), and added to 500 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. Then, 10 g of ZnCl2-loaded HMSN and 0.2 g of glycine were added, and the pH of the solution was adjusted to 7.4. The mixture was stirred at room temperature for 2 h, centrifuged, washed three times with PBS buffer solution at pH 7.4, and freeze-dried below 0 °C to obtain the HMSN-ZnCl2 composite material.

[0042] Polyglycolic acid (PGA) granules were dried in a vacuum drying oven until the moisture content was <0.1% at 75°C for 8 hours, and then set aside for later use. 0.5mm chopped glass fibers and glass fiber powder were mixed at a mass ratio of 1:1 and then added to a 1wt% KH550 silane coupling agent aqueous solution for stirring and soaking for 30 minutes. After filtration, the mixture was placed in a vacuum drying oven at 125°C for 40 minutes to obtain silane-modified glass fibers. 70g of dried polyglycolic acid, 35g of silane-modified glass fiber, 0.5g of bis(oxazoline) (BOZ), and 6g of acetylacetic tributyl citrate (ATBC) were added to a mixer and mixed at 170℃ and 120rpm for 10min. Then, 8g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1min. The mixture was then injection molded, with the barrel temperature controlled at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. The mixture was then annealed at 80℃ for 2h and cured at 35℃ for 24h to obtain the finished sealing ring.

[0043] Example 2

[0044] 222 mL of tetraethyl orthosilicate (TEOS), 109 g of cetyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia, and 0.6 g of zirconium oxide were mixed and stirred for 24 h. After centrifugation and washing, the mixture was calcined at 500 °C for 5 h to remove the template agent (CTAB), yielding 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, and 0.8 g of ZnCl2 was added. The mixture was heated to 55 °C, sonicated at 300 W for 4 h, and then vacuum dried at 80 °C for 6 h to obtain ZnCl2-loaded HMSN.

[0045] 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, and the pH of the solution was maintained at 7.4. The reaction was carried out for 12 h to obtain the PBA-Dex complex solution. Then, 15 g of ZnCl2-loaded HMSN and 0.3 g of glycine were added, and the pH of the solution was adjusted to 7.4. The mixture was stirred at room temperature for 2 h, centrifuged, washed three times with PBS buffer solution at pH 7.4, and freeze-dried below 0 °C to obtain the HMSN-ZnCl2 composite material.

[0046] Polyglycolic acid (PGA) granules were dried in a vacuum drying oven until the moisture content was <0.1% at 85℃ for 6 hours, and then set aside for later use. 0.5mm chopped glass fibers and glass fiber powder were mixed at a mass ratio of 1:1 and then added to a 1wt% KH550 silane coupling agent aqueous solution for stirring and soaking for 30 minutes. After filtration, the mixture was placed in a vacuum drying oven at 125℃ for 40 minutes to obtain silane-modified glass fibers. 80g of dried polyglycolic acid, 40g of silane-modified glass fiber, 1g of bisoxazoline (BOZ) and 10g of acetylacetic tributyl citrate (ATBC) were added to a mixer and mixed at 170℃ and 120rpm for 15min. Then, 12g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 2min. Injection molding was then carried out, with the barrel temperature controlled at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. Then, the mixture was annealed at 80℃ for 2h and cured at 35℃ for 24h to obtain the finished sealing ring.

[0047] Example 3

[0048] 222 mL of tetraethyl orthosilicate (TEOS), 109 g of cetyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia, and 0.6 g of zirconium oxide were mixed and stirred for 24 h. After centrifugation and washing, the mixture was calcined at 500 °C for 5 h to remove the template agent (CTAB), yielding 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, and 0.4 g of ZnCl2 was added. The mixture was heated to 55 °C, sonicated at 300 W for 4 h, and then vacuum dried at 80 °C for 6 h to obtain ZnCl2-loaded HMSN.

[0049] 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, and the pH of the solution was maintained at 7.4. The reaction was carried out for 12 h to obtain the PBA-Dex complex solution. Then, 12 g of ZnCl2-loaded HMSN and 0.2 g of glycine were added, and the pH of the solution was adjusted to 7.4. The mixture was stirred at room temperature for 2 h, centrifuged, washed three times with PBS buffer solution at pH 7.4, and freeze-dried below 0 °C to obtain the HMSN-ZnCl2 composite material.

[0050] Polyglycolic acid (PGA) granules were dried in a vacuum drying oven until the moisture content was <0.1% at 80℃ for 7 hours, and then set aside. 0.5mm chopped glass fibers and glass fiber powder were mixed at a mass ratio of 1:1 and then added to a 1wt% KH550 silane coupling agent aqueous solution for stirring and soaking for 30 minutes. After filtration, the mixture was placed in a vacuum drying oven at 125℃ for 40 minutes to obtain silane-modified glass fibers. 75g of dried polyglycolic acid, 30g of silane-modified glass fiber, 0.6g of bisoxazoline (BOZ) and 8g of acetylated tributyl citrate (ATBC) were added to a mixer and mixed at 170℃ and 120rpm for 12min. Then, 10g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1min. Injection molding was then carried out, with the barrel temperature controlled at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. Then, the mixture was annealed at 80℃ for 2h and cured at 35℃ for 24h to obtain the finished sealing ring.

[0051] Example 4

[0052] 222 mL of tetraethyl orthosilicate (TEOS), 109 g of cetyltrimethylammonium bromide (CTAB), 300 mL of 5 wt% ammonia, and 0.6 g of zirconium oxide were mixed and stirred for 24 h. After centrifugation and washing, the mixture was calcined at 500 °C for 5 h to remove the template agent (CTAB), yielding 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, sonicated at 300 W for 4 h, and then vacuum dried at 80 °C for 6 h to obtain ZnCl2-loaded HMSN.

[0053] 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, and the pH of the solution was maintained at 7.4. The reaction was carried out for 12 h to obtain the PBA-Dex complex solution. Then, 13 g of ZnCl2-loaded HMSN and 0.2 g of glycine were added, and the pH of the solution was adjusted to 7.4. The mixture was stirred at room temperature for 2 h, centrifuged, washed three times with PBS buffer solution at pH 7.4, and freeze-dried below 0 °C to obtain the HMSN-ZnCl2 composite material.

[0054] Polyglycolic acid (PGA) granules were dried in a vacuum drying oven until the moisture content was <0.1% at 80℃ for 7 hours, and then set aside. 0.5mm chopped glass fibers and glass fiber powder were mixed at a mass ratio of 1:1 and then added to a 1wt% KH550 silane coupling agent aqueous solution for stirring and soaking for 30 minutes. After filtration, the mixture was placed in a vacuum drying oven at 125℃ for 40 minutes to obtain silane-modified glass fibers. 75g of dried polyglycolic acid, 35g of silane-modified glass fiber, 0.7g of bisoxazoline (BOZ) and 9g of acetylacetic tributyl citrate (ATBC) were added to a mixer and mixed at 170℃ and 120rpm for 12min. Then, 12g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1.5min. Injection molding was then carried out, with the barrel temperature controlled at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. Then, the mixture was annealed at 80℃ for 2h and cured at 35℃ for 24h to obtain the finished sealing ring.

[0055] Example 5

[0056] 222 mL of tetraethyl orthosilicate (TEOS), 109 g of cetyltrimethylammonium bromide (CTAB), and 300 mL of 5 wt% ammonia were mixed and stirred for 24 h. After centrifugation and washing, the mixture was calcined at 500 °C for 5 h to remove the template agent (CTAB), yielding 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, and 0.5 g of ZnCl2 was added. The mixture was heated to 55 °C, sonicated at 300 W for 4 h, and then vacuum dried at 80 °C for 6 h to obtain ZnCl2-loaded HMSN.

[0057] 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, and the pH of the solution was maintained at 7.4. The reaction was carried out for 12 h to obtain the PBA-Dex complex solution. Then, 12 g of ZnCl2-loaded HMSN was added, and the pH of the solution was adjusted to 7.4. The mixture was stirred at room temperature for 2 h, centrifuged, washed three times with PBS buffer solution at pH 7.4, and freeze-dried below 0 °C to obtain the HMSN-ZnCl2 composite material.

[0058] Polyglycolic acid (PGA) granules were dried in a vacuum drying oven until the moisture content was <0.1% at 80℃ for 7 hours, and then set aside. 0.5mm chopped glass fibers and glass fiber powder were mixed at a mass ratio of 1:1 and then added to a 1wt% KH550 silane coupling agent aqueous solution for stirring and soaking for 30 minutes. After filtration, the mixture was placed in a vacuum drying oven at 125℃ for 40 minutes to obtain silane-modified glass fibers. 75g of dried polyglycolic acid, 35g of silane-modified glass fiber, 0.7g of bisoxazoline (BOZ) and 9g of acetylacetic tributyl citrate (ATBC) were added to a mixer and mixed at 170℃ and 120rpm for 12min. Then, 12g of HMSN-ZnCl2 composite material was added and mixed at 80rpm for 1.5min. Injection molding was then carried out, with the barrel temperature controlled at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. Then, the mixture was annealed at 80℃ for 2h and cured at 35℃ for 24h to obtain the finished sealing ring.

[0059] The present invention also includes the following comparative examples and related experiments.

[0060] Comparative Example 1

[0061] Compared with Example 4, the only difference is that the HMSN-ZnCl2 composite material was not prepared, but 0.6g of ZnCl2 was added directly for mixing instead. The other components and preparation steps were exactly the same, and the sealing ring was obtained.

[0062] Comparative Example 2

[0063] Compared with Example 4, the only difference is that the PBA-Dex composite solution was not prepared, and HMSN loaded with ZnCl2 was used instead of HMSN-ZnCl2 composite material. The other components and preparation steps are exactly the same, and the sealing ring is obtained.

[0064] Comparative Example 3

[0065] Compared with Example 4, the only difference is that ZnCl2 was not added; the other components and preparation steps are exactly the same, resulting in the finished sealing ring.

[0066] Performance testing

[0067] (I) Tensile strength and elongation at break test: The sealing rings obtained in Examples 1-5 and Comparative Examples 1-3 of this invention were tested for tensile strength and elongation at break in accordance with 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.

[0068] Bending strength test: The sealing rings obtained in Examples 1-5 and Comparative Examples 1-3 of this invention were tested for bending strength in accordance with the standard 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.

[0069]

[0070] As can be seen from the test results in Table 1 above, the sealing ring products obtained in Examples 1-5 of the present invention have excellent tensile strength and flexural strength, can meet high pressure requirements, and have high elongation at break and good toughness.

[0071] 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 overall tensile strength and flexural strength, as well as a significant decrease in elongation at break. This indicates that ZnCl2 directly contacts the composite material during the mixing process, which easily causes partial degradation of polyglycolic acid and a decrease in overall compatibility and bonding strength, thus significantly affecting the mechanical properties of the composite material. Comparative Example 2 was not encapsulated by the PBA-Dex composite, and its various mechanical properties also decreased. In contrast, Comparative Example 3 did not add ZnCl2 and exhibited excellent mechanical properties.

[0072] Solubility test: The same 0.3% wt KCl aqueous solution was added to the same test tank and the solution temperature was kept at 50℃. The sealing rings obtained in Examples 1-5 and Comparative Examples 1-3 of this invention were placed in the test tank for immersion. A portion was taken out after immersion for 12h, 24h and 36h respectively, and dried in a drying oven for 6h before tensile strength was tested. At the same time, the number of days required for the soaked sealing ring to completely dissolve into fine fragments and the presence of insoluble lumps were observed every day. The test results are summarized in Table 2 below.

[0073]

[0074] As can be seen from the test results in Table 2 above, the sealing ring products obtained in Examples 1-5 of this invention exhibit slow initial dissolution during immersion in a simulated downhole environment. They maintain a tensile strength exceeding 112.6 MPa within 36 hours, meeting the long-term high-pressure sealing strength requirements. Within 24 hours, the tensile strength exceeds 142.0 MPa, meeting the long-term ultra-high pressure sealing strength requirements. Furthermore, the dissolution time can be controlled within 8 days, indicating that the catalyst release becomes increasingly rapid in the later stages, allowing the overall material to dissolve quickly and fully without any insoluble lumps, thus preventing pipeline blockage and not affecting secondary mining. Example 4 is the optimal solution, maintaining a high tensile strength of 135.8 MPa even after immersion for 36 hours. In Example 5, the absence of zirconium oxide mixing during the preparation of hollow mesoporous silica and the lack of glycine addition during PBA-Dex composite encapsulation resulted in a lower zinc chloride loading effect compared to other examples, leading to a slight decrease in the overall strength of the sealing ring. The initial dissolution was also faster than in other examples, resulting in a more significant decrease in tensile strength.

[0075] Compared to Example 4, Comparative Example 1, due to the direct addition of ZnCl2 during the mixing process, has ZnCl2 directly exposed on the material surface, resulting in high catalytic efficiency and the lowest overall dissolution time of only 6 days. However, because the catalyst is unprotected, it begins to dissolve rapidly upon being placed in water, leading to a significant decrease in tensile strength after only 12 hours of soaking, which cannot meet the requirements for long-term high-pressure sealing. Although Comparative Example 2 did not use PBA-Dex composite encapsulation, it used hollow mesoporous silica-supported zinc chloride, which can delay catalyst release to some extent. Therefore, the rate of decrease in tensile strength after soaking is significantly slower than that of Comparative Example 1, but it is still significantly different from Example 4. While Comparative Example 3 can maintain ultra-high tensile strength and meet the requirements for long-term high-pressure sealing, it lacks a catalyst, dissolves slowly (more than 15 days), and contains insoluble lumps that can easily clog pipes later, affecting secondary development.

[0076] The above are preferred embodiments of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within 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 preparation steps include the following: S1. Hollow mesoporous silica was dispersed in anhydrous ethanol, ZnCl2 was added, heated, sonicated, and vacuum dried to obtain ZnCl2-loaded HMSN; S2. 3-Carboxyphenylboronic acid and dextran were added to 0.1M PBS buffer solution at a molar ratio of 1:2, and the pH of the solution was kept at 7.

4. The reaction was carried out for 12 hours to obtain PBA-Dex complex solution. Then HMSN loaded with ZnCl2 was added, stirred at room temperature, centrifuged, washed, and freeze-dried to obtain HMSN-ZnCl2 composite material. S3. Add the pre-dried polyglycolic acid, silane-modified glass fiber, bisoxazoline and tributyl acetyl citrate to a mixer and mix them at 170℃ and 120rpm for 10-15min. Then add the HMSN-ZnCl2 composite material and mix it at 80rpm for 1-2min. Inject the mixture into a mold, controlling the barrel temperature at 170℃-180℃, the mold temperature at 40℃, the holding pressure at 60MPa, and the cooling time at 30s. Then anneal at 80℃ for 2h and cure at 35℃ for 24h to obtain the finished product. The molecular weight of the dextran is MW=10kDa; in step S2, when adding HMSN loaded with ZnCl2, glycine is also added, and the pH of the solution is adjusted to 7.

4. The mixture is stirred at room temperature for 2 hours, centrifuged, washed with PBS buffer solution at pH 7.4, and freeze-dried below 0°C to obtain the HMSN-ZnCl2 composite material.

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: tetraethyl orthosilicate and hexadecyltrimethylammonium bromide are added to ammonia water, mixed, stirred, centrifuged and washed, and then calcined 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: In the preparation of the hollow mesoporous silica, zirconium oxide is added to ammonia water and mixed, stirred for 24 hours, centrifuged and washed, and then calcined at 500°C for 5 hours to obtain the product; 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 step S1, after adding ZnCl2, the mixture is heated to 55°C, ultrasonicated at 300W for 4 hours, and then vacuum dried at 80°C for 6 hours to obtain ZnCl2-loaded HMSN.

5. The method for preparing a sealing ring for a soluble bridge plug according to claim 1, characterized in that: The polyglycolic acid undergoes the following drying pretreatment: polyglycolic acid granules are placed in a vacuum drying oven at a temperature of 75-85℃ and dried for 6-8 hours until the moisture content is <0.1%.

6. 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: glass fiber is placed in a 1wt% KH550 silane coupling agent aqueous solution and stirred and soaked for 30 min, filtered, placed in a vacuum drying oven at 125℃ and dried for 40 min; 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.

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

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