A method for sealing and unsealing oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels

Abstract

This invention relates to a method for sealing and unsealing oil and gas pipelines using stimulus-responsive hydrogels in thermal operations, specifically within the field of temporary sealing technology for oil and gas pipeline thermal operations. The method includes the following steps: obtaining a stimulus-responsive hydrogel; injecting the stimulus-responsive hydrogel into the pipeline as a sealing material to achieve sealing; performing thermal cutting and welding on the pipeline after sealing to replace it; and injecting unsealing material into the replaced pipeline to complete unsealing. The sealing technology provided by this invention ensures the safety of oil and gas pipeline thermal operations and improves the efficiency of thermal construction. After construction, applying external environmental stimuli to the residual hydrogel in the pipeline causes it to transform into a liquid, thereby achieving complete unsealing of the pipeline and ensuring the safety and stability of subsequent pipeline operations.

Description

Technical Field

[0001] This invention relates to the field of temporary plugging technology for thermal operations in oil and gas pipelines, and in particular to a method for plugging and unplugging oil and gas pipelines based on stimulus-responsive hydrogels for thermal operations. Background Technology

[0002] With continuous innovation in oil and gas exploration and development technologies, especially in unconventional oil and gas fields such as deep-water and ultra-deep-water offshore areas, significant breakthroughs have been achieved, leading to new heights in oil and gas production. To meet the demands of offshore oil and gas enhancement processes, and due to corrosion or process modifications, it is necessary to replace existing pipelines, joints, or valves. Current construction methods primarily involve cold cutting, which not only requires high standards for pipeline flushing, purging, and inerting processes but also involves cumbersome procedures, low cutting efficiency, and results in prolonged downtime.

[0003] Thermal cutting methods can effectively improve cutting efficiency and reduce economic losses caused by production stoppages. To ensure the safety of thermal operations, oil and gas isolation is necessary during the process. Existing technology provides a hydrogel for temporarily sealing oil pipelines and its preparation method, which can seal pipelines and ensure the safety of thermal operations. However, this hydrogel is difficult to completely break down and unblock. When only increasing pressure to clear the pipeline, the residual hydrogel can easily clog precision instruments or valves, posing a significant threat to subsequent pipeline operations. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels. This method ensures the safety of thermal operations in oil and gas pipelines and improves the efficiency of thermal construction. After construction, applying external environmental stimuli to the residual hydrogel in the pipeline causes it to transform into a liquid, thereby completely unblocking the pipeline and ensuring the safety and stability of subsequent pipeline operations.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] This invention provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels, the method comprising the following steps:

[0007] A stimulus-responsive hydrogel was obtained;

[0008] The stimulus-responsive hydrogel is injected into the pipe as a sealing material to achieve sealing;

[0009] After the pipeline is sealed, thermal cutting and thermal welding are performed to complete the pipeline replacement.

[0010] Inject unblocking material into the replaced pipe to complete the unblocking process;

[0011] The amount of sealing material used in the thermal cutting section is based on Formula 1: Sure;

[0012] In Formula 1: Q represents the amount of sealing material used at the thermal cutting location, in liters; D represents the outer diameter of the pipe, in millimeters; h represents the pipe wall thickness, in millimeters; and L represents the sealing distance, in millimeters.

[0013] The total amount of the sealing material injected is 3 to 5 times the amount of sealing material used in the thermal cutting section.

[0014] Furthermore, the stimulus-responsive hydrogel may exhibit at least one of temperature-induced stimulus response, redox-induced stimulus response, and acid-base-induced stimulus response.

[0015] Furthermore, the gelation driving force of the stimulus-responsive hydrogel includes at least one of Schiff base bonds, borate ester bonds, disulfide bonds, thiol-thioester exchange interactions, hydrogen bonds, π-π conjugation interactions, hydrophobic interactions, ionic interactions, electrostatic interactions, and host-guest interactions.

[0016] Furthermore, an imine-crosslinked acid-base responsive hydrogel is used as the sealing material. The preparation method of the imine-crosslinked acid-base responsive hydrogel includes the following steps:

[0017] The polyamine compound solution and the first crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base responsive hydrogel crosslinked with imine bonds.

[0018] Wherein, the weight percentage concentration of the polyamine compound solution is 1wt% to 5wt%, the weight percentage concentration of the first crosslinking agent solution is 8wt% to 12wt%, and the weight ratio of the polyamine compound solution to the first crosslinking agent solution is (5 to 10):(1 to 5).

[0019] The polyamino compound includes at least one of chitosan, polyethyleneimine, and gelatin; the structural formula of the first crosslinking agent is shown in formula (I);

[0020] Equation (I): The preparation method for a product with n ranging from 45 to 230 includes the following steps:

[0021] Polyethylene glycol (with a repeating unit number n of 45–230) is completely dissolved in anhydrous acetonitrile, and then 4-dimethylaminopyridine and N,N'-succinimide carbonate are added to it. The weight percentage concentration of the polyethylene glycol is 5 wt%–20 wt%, and the molar ratio of polyethylene glycol, 4-dimethylaminopyridine, and N,N'-succinimide carbonate is always 1:2:2. The reaction is carried out at room temperature for 10–20 h. Diethyl ether is added to the above acetonitrile solution, wherein the volume ratio of acetonitrile solution to diethyl ether is (1–3):(3–5). The white product that precipitates is the first crosslinking agent.

[0022] Furthermore, an acid-base responsive hydrogel crosslinked with borate ester bonds is used as the sealing material. The preparation method of the acid-base responsive hydrogel crosslinked with borate ester bonds includes the following steps:

[0023] The polyhydroxy compound solution and the second crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base stimuli-responsive hydrogel crosslinked by borate ester bonds.

[0024] Wherein, the weight percentage concentration of the polyhydroxy compound solution is 2wt% to 10wt%, the weight percentage concentration of the second crosslinking agent solution is 0.5wt% to 5wt%, and the weight ratio of the polyhydroxy compound solution to the second crosslinking agent solution is (1 to 5):(1 to 5);

[0025] The polyhydroxy compound includes at least one of guar gum, polyvinyl alcohol, and tannic acid; the second crosslinking agent is a compound containing a boric acid structure, and the compound containing a boric acid structure includes at least one of borax, 3-carboxyphenylboronic acid, and 4-carboxyphenylboronic acid.

[0026] Furthermore, a hydrogen-bonded cross-linked temperature-stimulated responsive hydrogel is used as the sealing material. The preparation method of the hydrogen-bonded cross-linked temperature-stimulated responsive hydrogel includes the following steps:

[0027] The functional monomer, acrylamide and photoinitiator were formulated into a solution with a weight fraction of 0.5% to 5%, and then photoinitiated polymerization was carried out under a UV lamp to obtain the temperature-stimulated hydrogel with hydrogen bonding crosslinking.

[0028] The photoinitiator has a weight fraction of 2% of the total mass of the functional monomer and acrylamide.

[0029] The weight ratio of the functional monomer to the acrylamide is (5-10):(1-5);

[0030] The structural formula of the functional unit is shown in formula (II);

[0031] Equation (II): Its preparation method includes the following process:

[0032] Anhydrous potassium carbonate is dissolved in water, and glycine hydrochloride is added until completely dissolved. Acryloyl chloride is dissolved in acetonitrile and added dropwise to the above aqueous solution. The reaction is carried out at 5-10°C for 2-6 hours. After the reaction is complete, water and acetonitrile are removed by rotary evaporation. The resulting solid is added to anhydrous ethanol, stirred, and filtered. The filtrate is then rotary evaporated to obtain a white solid, which is the functional monomer mentioned above. The weight percentage concentration of the anhydrous potassium carbonate is 5wt%-30wt%, the molar ratio of anhydrous potassium carbonate to glycine hydrochloride is (2-4):(1-2), the weight percentage concentration of the acryloyl chloride is 5wt%-20wt%, the molar ratio of glycine hydrochloride to acryloyl chloride is always 1:1.2, and the amount of anhydrous ethanol added is approximately 10-50 times the mass of the anhydrous potassium carbonate.

[0033] Furthermore, a coordination-crosslinked redox-responsive hydrogel is used as the sealing material. The preparation method of the coordination-crosslinked redox-responsive hydrogel includes the following steps:

[0034] The polycarboxylated polymer solution and ferric chloride solution were stirred and mixed, and then allowed to stand to obtain the redox-stimulated hydrogel with coordination crosslinking.

[0035] Wherein, the weight percentage concentration of the polycarboxylated polymer solution is 3wt% to 10wt%, the weight percentage concentration of the ferric chloride solution is 1wt% to 5wt%, and the weight ratio of the polycarboxylated polymer solution to the ferric chloride solution is (50 to 100):(1 to 5);

[0036] The polycarboxylated polymer includes at least one of gelatin, carboxymethyl cellulose, and polyacrylic acid.

[0037] Furthermore, the unblocking material includes at least one of acidic or alkaline solutions, redox solutions, solutions at 60–90°C, and solutions with high salt concentrations.

[0038] Furthermore, before injecting the sealing material into the pipeline, construction preparation work is carried out on the pipeline in the sealing area; the construction preparation work includes depressurizing and cleaning the pipeline in the sealing area.

[0039] Furthermore, after the pipeline is unblocked by injecting unblocking material, the pipeline welds are inspected and diagnosed using an ultrasonic diagnostic instrument or an XRD instrument to determine the effectiveness of the pipeline repair.

[0040] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art:

[0041] 1) This invention provides a method for sealing and unsealing oil and gas pipelines in thermal operations based on stimulus-responsive hydrogel. This sealing technology can ensure the safety of oil and gas pipeline thermal operations and improve the efficiency of thermal construction. After construction, external environmental stimuli are applied to the hydrogel remaining in the pipeline, causing the hydrogel to transform into a liquid, thereby completely unblocking the pipeline and ensuring the safety and stability of subsequent pipeline operations.

[0042] 2) The method for sealing and unblocking oil and gas pipelines based on stimulus-responsive hydrogels provided by this invention replaces traditional physical sealing equipment and non-degradable sealing materials with a rapidly breaking down stimulus-responsive hydrogel. It uses thermal cutting instead of traditional cold cutting, simplifying the oil and gas pipeline replacement process, reducing equipment and personnel requirements, eliminating operational space limitations, and making it suitable for pipelines and networks of any size. Compared to traditional physical sealing processes, the entire construction cycle is shortened by more than 60%. The chemical materials used in this method have excellent water solubility and stimulus responsiveness. Unblocking only requires injecting formation water from the production platform into the pipeline or adding an appropriate amount of unblocking material to the formation water before injecting it into the pipeline. The unblocking fluid leaves no residue, has good compatibility with crude oil, and will not affect subsequent crude oil processing. Attached Figure Description

[0043] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic flowchart illustrating a method for sealing and unblocking oil and gas pipelines using a stimulus-responsive hydrogel in thermal operations, as provided in an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram showing the pipe dimensions and pipe cutting locations in an embodiment of the present invention.

[0047] Figure 3 This is a schematic diagram of the pipeline sealing and thermal operation process in an embodiment of the present invention.

[0048] Figure 4 This is a schematic diagram of the pipeline unblocking process in an embodiment of the present invention. Detailed Implementation

[0049] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] This invention provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels, such as... Figure 1 As shown, the method includes the following steps:

[0052] A stimulus-responsive hydrogel was obtained;

[0053] The stimulus-responsive hydrogel is injected into the pipe as a sealing material to achieve sealing;

[0054] After the pipeline is sealed, thermal cutting and thermal welding are performed to complete the pipeline replacement.

[0055] Inject unblocking material into the replaced pipe to complete the unblocking process;

[0056] The amount of sealing material used in the thermal cutting section is based on Formula 1: Sure;

[0057] In Formula 1: Q represents the amount of sealing material used at the thermal cutting location, in liters; D represents the outer diameter of the pipe, in millimeters; h represents the pipe wall thickness, in millimeters; and L represents the sealing distance, in millimeters.

[0058] The total amount of the sealing material injected is 3 to 5 times the amount of sealing material used in the thermal cutting section.

[0059] The technical solutions provided in the embodiments of the present invention have at least the following advantages compared with the prior art:

[0060] 1) This invention provides a method for sealing and unsealing oil and gas pipelines in thermal operations based on stimulus-responsive hydrogel. This sealing technology can ensure the safety of oil and gas pipeline thermal operations and improve the efficiency of thermal construction. After construction, external environmental stimuli are applied to the hydrogel remaining in the pipeline, causing the hydrogel to transform into a liquid, thereby completely unblocking the pipeline and ensuring the safety and stability of subsequent pipeline operations.

[0061] 2) The method for sealing and unblocking oil and gas pipelines based on stimulus-responsive hydrogels provided by this invention replaces traditional physical sealing equipment and non-degradable sealing materials with a rapidly breaking down stimulus-responsive hydrogel. It uses thermal cutting instead of traditional cold cutting, simplifying the oil and gas pipeline replacement process, reducing equipment and personnel requirements, eliminating operational space limitations, and making it suitable for pipelines and networks of any size. Compared to traditional physical sealing processes, the entire construction cycle is shortened by more than 60%. The chemical materials used in this method have excellent water solubility and stimulus responsiveness. Unblocking only requires injecting formation water from the production platform into the pipeline or adding an appropriate amount of unblocking material to the formation water before injecting it into the pipeline. The unblocking fluid leaves no residue, has good compatibility with crude oil, and will not affect subsequent crude oil processing.

[0062] like Figure 2 As shown, the present invention controls the amount of sealing material used in the thermal cutting part through Formula 1. On the one hand, it helps to clarify the specific amount of sealing material used, avoiding insufficient or excessive waste of sealing material during actual sealing; on the other hand, it improves the sealing effect.

[0063] As one embodiment of this application, the stimulus-responsive hydrogel's stimulus response mode includes at least one of temperature stimulus response, redox stimulus response, and acid-base stimulus response; the gelation driving force of the stimulus-responsive hydrogel includes at least one of Schiff base bond, borate ester bond, disulfide bond, thiol-thioester exchange interaction, hydrogen bond, π-π conjugation interaction, hydrophobic interaction, ionic interaction, electrostatic interaction, and host-guest interaction.

[0064] In this application, the sealing material is a hydrogel that responds to temperature, redox, and acid-base stimuli. Its gelation driving forces include, but are not limited to, Schiff base bonds, borate ester bonds, disulfide bonds, thiol-thioester exchange interactions, hydrogen bonds, π-π conjugation interactions, hydrophobic interactions, ionic interactions, electrostatic interactions, and host-guest interactions. It can replace traditional physical sealing devices and non-degradable sealing materials, effectively avoiding the defects of traditional sealing materials such as difficult-to-break gel and easy residue.

[0065] In some specific embodiments, an imine-crosslinked acid-base responsive hydrogel is used as the sealing material. The preparation method of the imine-crosslinked acid-base responsive hydrogel includes the following steps:

[0066] The polyamine compound solution and the first crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base responsive hydrogel crosslinked with imine bonds.

[0067] Wherein, the weight percentage concentration of the polyamine compound solution is 1wt% to 5wt%, the weight percentage concentration of the first crosslinking agent solution is 8wt% to 12wt%, and the weight ratio of the polyamine compound solution to the first crosslinking agent solution is (5 to 10):(1 to 5).

[0068] The polyamino compound includes at least one of chitosan, polyethyleneimine, and gelatin; the structural formula of the first crosslinking agent is shown in formula (I);

[0069] Equation (I): n is 45–230; its preparation method includes the following process:

[0070] Polyethylene glycol (with a repeating unit number n of 45–230) is completely dissolved in anhydrous acetonitrile, and then 4-dimethylaminopyridine and N,N'-succinimide carbonate are added to it. The weight percentage concentration of the polyethylene glycol is 5 wt%–20 wt%, and the molar ratio of polyethylene glycol, 4-dimethylaminopyridine, and N,N'-succinimide carbonate is always 1:2:2. The reaction is carried out at room temperature for 10–20 h. Diethyl ether is added to the above acetonitrile solution, wherein the volume ratio of acetonitrile solution to diethyl ether is (1–3):(3–5). The white product that precipitates is the first crosslinking agent.

[0071] In some specific embodiments, a borate ester cross-linked acid-base responsive hydrogel is used as the sealing material. The preparation method of the borate ester cross-linked acid-base responsive hydrogel includes the following steps:

[0072] The polyhydroxy compound solution and the second crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base stimuli-responsive hydrogel crosslinked by borate ester bonds.

[0073] Wherein, the weight percentage concentration of the polyhydroxy compound solution is 2wt% to 10wt%, the weight percentage concentration of the second crosslinking agent solution is 0.5wt% to 5wt%, and the weight ratio of the polyhydroxy compound solution to the second crosslinking agent solution is (1 to 5):(1 to 5);

[0074] The polyhydroxy compound includes at least one of guar gum, polyvinyl alcohol, and tannic acid; the second crosslinking agent is a compound containing a boric acid structure, and the compound containing a boric acid structure includes at least one of borax, 3-carboxyphenylboronic acid, and 4-carboxyphenylboronic acid.

[0075] In some specific embodiments, hydrogen-bonded cross-linked temperature-stimulated responsive hydrogels are used as sealing materials. The preparation method of the hydrogen-bonded cross-linked temperature-stimulated responsive hydrogels includes the following steps:

[0076] The functional monomer, acrylamide and photoinitiator were formulated into a solution with a weight fraction of 0.5% to 5%, and then photoinitiated polymerization was carried out under a UV lamp to obtain the temperature-stimulated hydrogel with hydrogen bonding crosslinking.

[0077] The photoinitiator has a weight fraction of 2% of the total mass of the functional monomer and acrylamide.

[0078] The weight ratio of the functional monomer to the acrylamide is (5-10):(1-5);

[0079] The structural formula of the functional unit is shown in formula (II);

[0080] Equation (II): Its preparation method includes the following process:

[0081] Anhydrous potassium carbonate is dissolved in water, and glycine hydrochloride is added until completely dissolved. Acryloyl chloride is dissolved in acetonitrile and added dropwise to the above aqueous solution. The reaction is carried out at 5-10°C for 2-6 hours. After the reaction is complete, water and acetonitrile are removed by rotary evaporation. The resulting solid is added to anhydrous ethanol, stirred, and filtered. The filtrate is then rotary evaporated to obtain a white solid, which is the functional monomer mentioned above. The weight percentage concentration of the anhydrous potassium carbonate is 5wt%-30wt%, the molar ratio of anhydrous potassium carbonate to glycine hydrochloride is (2-4):(1-2), the weight percentage concentration of the acryloyl chloride is 5wt%-20wt%, the molar ratio of glycine hydrochloride to acryloyl chloride is always 1:1.2, and the amount of anhydrous ethanol added is approximately 10-50 times the mass of the anhydrous potassium carbonate.

[0082] In some specific embodiments, a coordination-crosslinked redox-responsive hydrogel is used as the sealing material. The preparation method of the coordination-crosslinked redox-responsive hydrogel includes the following steps:

[0083] The polycarboxylated polymer solution and ferric chloride solution were stirred and mixed, and then allowed to stand to obtain the redox-stimulated hydrogel with coordination crosslinking.

[0084] Wherein, the weight percentage concentration of the polycarboxylated polymer solution is 3wt% to 10wt%, the weight percentage concentration of the ferric chloride solution is 1wt% to 5wt%, and the weight ratio of the polycarboxylated polymer solution to the ferric chloride solution is (50 to 100):(1 to 5);

[0085] The polycarboxylated polymer includes at least one of gelatin, carboxymethyl cellulose, and polyacrylic acid.

[0086] In some specific embodiments, the unblocking material includes at least one of acidic or alkaline solutions, redox solutions, solutions at 60–90°C, and solutions with high salt concentrations.

[0087] In some specific embodiments, before injecting the sealing material into the pipeline, preparatory work is carried out on the pipeline in the sealing area; this preparatory work includes depressurizing and cleaning the pipeline in the sealing area. Before construction, it is ensured that the pipeline has ceased operation and that the pipeline in the sealing area has been depressurized to ensure pressure safety in the sealing area. Simple filling and cleaning of the sealing area reduces the residual oil and gas content and prevents combustion during thermal cutting.

[0088] In some specific embodiments, after the pipeline is unblocked by injecting unblocking material, the pipeline weld is inspected and diagnosed by an ultrasonic diagnostic instrument or an XRD instrument to determine the pipeline repair effect.

[0089] In some specific embodiments, when injecting sealing material to seal a pipeline, the process includes: opening a 2cm diameter hole in the sealing area, connecting a feeding assembly and a valve, and using a screw pump to inject the sealing material into the pipeline to achieve pipeline sealing. Alternatively, the sealing material can be injected directly by a screw pump or a rotary pump; alternatively, an aqueous solution of a functional compound can be directly injected, which, after cooling by a cooling device, forms a gel to seal the pipeline.

[0090] In some specific embodiments, the process of injecting unblocking material to achieve unblocking includes: drilling a hole in the replaced pipe, connecting an injection assembly and valve, and injecting the unblocking material into the pipe using a centrifugal pump. Under the action of the unblocking material, the sealing material undergoes a gel-sol transformation, completing the pipe unblocking. Alternatively, the unblocking material can be injected from a tee fitting, a pipe port, or an intermediate valve. To accelerate unblocking, gas can be introduced for aeration, or thermal unblocking material or 80-90°C hot water can be continuously added to the pipeline. After the unblocking process is completed, the pipeline is flushed with produced water or hot water, and the unblocking fluid is discharged and recovered from a downstream valve, completing the unblocking process and facilitating the pipe replacement.

[0091] In some specific embodiments, thermal cutting is used instead of traditional cold cutting. On-site cutting can be performed using hot cutting methods such as acetylene flame or plasma flame. The sealing material has excellent cooling performance and will not cause additional impact on the pipeline.

[0092] It should be noted that, unless otherwise specified, the raw material compounds involved in this invention, such as the method for sealing and unblocking oil and gas pipelines based on stimulus-responsive hydrogels for thermal operations, can be directly adopted from commercially available products or prepared in-house according to existing preparation processes. Furthermore, unless otherwise specified, the steps of the method for sealing and unblocking oil and gas pipelines based on stimulus-responsive hydrogels for thermal operations can be performed according to existing technologies, and will not be described in detail in this application.

[0093] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0094] Example 1

[0095] This example provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels (specifically, a sealing and unblocking technique for oil and gas pipelines in thermal operations based on acid-base stimuli-responsive hydrogels). Figure 3 and Figure 4 As shown, the process includes the following:

[0096] 1) Construction preparation

[0097] Before construction, ensure that the pipeline has stopped transporting goods and depressurize the pipeline in the sealing area so that the pressure value in the pipeline in the sealing area is <1kPa to ensure the pressure safety of the sealing area; use nitrogen to fill and clean the sealing area to reduce the residual oil and gas content in the sealing area and prevent combustion during thermal cutting.

[0098] 2) Preparation of sealing and unblocking materials

[0099] The sealing material is an acid-base responsive hydrogel, and its cross-linking is driven by imine bonds. Specifically, a 2.5% (w / w) aqueous solution of a polyamine compound and a 10% (w / w) aqueous solution of a synthetic cross-linking agent are prepared. These two solutions are mixed at a weight ratio of 5:2 and allowed to stand for 30 minutes to obtain the sealing material. An appropriate amount of a breaker (specifically oxalic acid) is prepared to form a 20% (w / w) solution to obtain the unblocking material. The polyamine compound is chitosan (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.), and the cross-linking agent has the following structural formula:

[0100] n is 45; its preparation method includes the following process:

[0101] 10 g of polyethylene glycol (with a repeating unit number n of 45) was completely dissolved in anhydrous acetonitrile. Then, 1.2 g of 4-dimethylaminopyridine and 2.6 g of N,N'-succinimidyl carbonate were added. The weight percentage concentration of the polyethylene glycol was 10 wt%, and the molar ratio of polyethylene glycol, 4-dimethylaminopyridine, and N,N'-succinimidyl carbonate was maintained at 1:2:2. The reaction was carried out at room temperature for 12 h. Diethyl ether was then added to the acetonitrile solution, with a volume ratio of acetonitrile solution to ether of 1:3. The resulting white precipitate was the first crosslinking agent.

[0102] 3) Injecting chemical sealing materials to achieve pipeline sealing.

[0103] Determine the amount of sealing material needed: Based on the specific circumstances, such as the length of the pipe fitting being replaced, determine the cutting location and the distance of the cutting area, denoted as L. The amount of sealing material injected should be 3 to 5 times the amount injected into the cutting area; this can be further determined on-site based on the actual strength of the hydrogel and the sealing condition. The amount Q injected into the cutting area is: The total amount of sealing material used is increased four times based on the amount used in the cutting section. Specifically, in this example: D is 112mm, h is 4mm, L is 2000mm, and Q is 17L.

[0104] Determine the injection hole: Depending on the specific circumstances of the pipe fitting to be replaced, injection can be made from the tee or the damaged part of the pipe fitting to be replaced, or injection can be made directly from a hole drilled in the pipe to be replaced.

[0105] Injecting the sealing material: Select an appropriate injection rate based on the actual power of the injection pump and the actual gel strength of the hydrogel sealing material. Inject the hydrogel into the pipe through the injection hole. For the actual working conditions of vertical pipes, the injection rate can be increased. The entire sealing time is 30 minutes.

[0106] 4) Hot work is used to complete the cutting and welding of the pipes to be replaced:

[0107] Thermal cutting operation: After the pipe sealing area is completely filled with hydrogel sealing material, connect the injection port to a gas valve and introduce a small amount of gas. Observe the pressure gauge changes. If the pressure gauge pointer is stable, it indicates that the pipe sealing is good. Large amounts of gas should not be introduced during this process to prevent reaching the pressure limit. After the pipe sealing area is completely filled with hydrogel and the seal is guaranteed, hot work can be performed. On-site hot work methods such as acetylene flame or plasma flame can be used for cutting, which should be completed within 3 minutes.

[0108] Thermal welding operation: After cutting, remove the pipe fitting to be replaced and recover any residual hydrogel sealing material inside. Remove a certain amount of sealing material from each end of the pipeline on one side of the cut, ensuring that any remaining sealing material is 2.5 meters away from the weld joint to prevent it from affecting the welding process. After clearing welding space at both ends of the pipeline, connect the new pipe fitting according to its condition. Strictly adhere to the welding procedures. After welding, inspect the weld. Once the inspection is passed, the welding process is complete.

[0109] 5) Injecting chemical unblocking materials to achieve unblocking.

[0110] The chemical unblocking material is an acidic solution (specifically oxalic acid), which is injected into the pipe fitting tee, pipeline port, or intermediate valve. To accelerate the unblocking process, gas is introduced for aeration after injection. Alternatively, thermal unblocking material or 80-90°C hot water can be continuously added to the pipeline. After the unblocking process is complete, the pipeline is flushed with produced water or hot water, and the unblocking solution is discharged and recovered from the downstream valve, completing the unblocking process and facilitating pipe fitting replacement.

[0111] The method for sealing and unsealing oil and gas pipelines using thermal methods provided in this example enables thermal cutting of the pipeline in just 3 minutes, leaving no residue after the adhesive is broken. In contrast, traditional physical sealing processes require cold cutting, which typically takes up to 1 hour, significantly shortening the construction cycle.

[0112] Example 2

[0113] This example provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels (specifically, a sealing and unblocking technique for oil and gas pipelines in thermal operations based on borate ester crosslinking acid-base stimulus-responsive hydrogels). The difference from Example 1 is that the sealing material is a borate ester crosslinking acid-base stimulus-responsive hydrogel. Specifically, a 6% (w / w) aqueous solution of a polyhydroxy compound is prepared, and a 3% (w / w) aqueous solution of a crosslinking agent is prepared. The two solutions are mixed in a specific ratio (the specific weight ratio of the polyhydroxy compound aqueous solution and the crosslinking agent solution is 1:1), and the sealing material is obtained within 30 minutes after rapid stirring. The polyhydroxy compound is tannic acid, and the crosslinking agent is 3-carboxyphenylboronic acid. The unblocking material is a weakly acidic solution (specifically sodium carbonate), and the unblocking time is 60 minutes.

[0114] The method for sealing and unblocking oil and gas pipelines using thermal cutting provided in this example enables thermal cutting operations on pipelines. Similar to Example 1, this method significantly reduces the construction period compared to traditional cold cutting operations. Furthermore, the weakly alkaline unblocking material exhibits less temporary corrosiveness to the pipeline compared to acidic unblocking materials.

[0115] Example 3

[0116] This example provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels (specifically, a sealing and unblocking technique for oil and gas pipelines in thermal operations based on hydrogen-bonded cross-linked temperature-stimulated hydrogels). The difference from Example 1 is that the sealing material is a hydrogen-bonded cross-linked temperature-stimulated hydrogel. Specifically, a 3% (w / w) solution is prepared from a functional monomer capable of forming multiple hydrogen bonds, acrylamide, and a photoinitiator (specifically, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone). The photoinitiator mass fraction is 2% of the total mass of the functional monomer and acrylamide. Photoinitiated polymerization is performed using a UV lamp, and the sealing material is obtained after 40 minutes of reaction. The unblocking material is a 5% hot urea solution (70°C) or high-temperature produced water from the production platform (80°C), and the unblocking time is 60 minutes. The weight ratio of the functional monomer to acrylamide is 5:1. The structural formula of the functional monomer capable of forming a multi-hydrogen-bonded cross-linked hydrogel is:

[0117] Its preparation method includes the following process:

[0118] 27.6 g of anhydrous potassium carbonate was dissolved in water, and then 11.1 g of glycine hydrochloride was added to it until completely dissolved. 10.9 g of acryloyl chloride was dissolved in acetonitrile and added dropwise to the above aqueous solution. The reaction was carried out at 5 °C for 4 h. After the reaction was completed, the water and acetonitrile were removed by rotary evaporation. The resulting solid was added to 500 mL of anhydrous ethanol, stirred, and filtered. The filtrate was then rotary evaporated to obtain a white solid, which is the functional monomer mentioned above. The weight percentage concentration of the anhydrous potassium carbonate was 15 wt%, and the molar ratio of anhydrous potassium carbonate to glycine hydrochloride was 2:1. The weight percentage concentration of the acryloyl chloride was 15 wt%, and the molar ratio of glycine hydrochloride to acryloyl chloride was always 1:1.2.

[0119] The method for sealing and unblocking oil and gas pipelines using thermal cutting provided in this example enables thermal cutting operations. Similar to Example 1, this method significantly reduces the construction period compared to traditional cold cutting operations. Furthermore, using high-temperature hot water facilitates more thorough pipeline unblocking compared to acidic or alkaline unblocking materials.

[0120] Example 4

[0121] This example provides a method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels (specifically, a sealing and unblocking technique for oil and gas pipelines in thermal operations based on coordination cross-linked redox-stimulated hydrogels). The difference from Example 1 is that the sealing material is a coordination cross-linked redox-stimulated hydrogel. Specifically, a 7% (w / w) aqueous solution of a polycarboxylic acid polymer and a 2% (w / w) aqueous solution of ferric chloride are prepared. The two solutions are mixed uniformly in a certain ratio (the weight ratio of the polycarboxylic acid polymer solution to the ferric chloride solution is 50:1). Iron ions then cross-link with the polycarboxylic acid polymer to form a redox-stimulated hydrogel sealing material. The unblocking material is a reducing solution (specifically, a concentration of 30%), and the unblocking time is 50 minutes. The polycarboxylic acid polymer is gelatin, and the unblocking material is sodium bisulfite.

[0122] Comparative Example 1

[0123] This example provides a foamed sealing material, prepared as follows: 10g of polyether F127 (molecular weight 12000, purchased from Shanghai Maclean Biochemical Technology Co., Ltd., hereinafter the same), 1.5g of triethanolamine, 1g of sodium dibutylnaphthalenesulfonate, and 10g of water are mixed evenly to form component one. 10g of hexamethylene diisocyanate and 8g of silicone oil are mixed to form component two. Component one and component two are then mixed and foamed to form the sealing material.

[0124] The sealing material obtained in this example can effectively seal the pipeline; however, it contains a large amount of organic components, making it difficult to achieve a flame-retardant effect and hindering the pipeline's thermal operation. Furthermore, the sealing material lacks responsiveness after formation, making it difficult to completely unblock the pipeline after sealing.

[0125] In summary, this invention provides a method for sealing and unsealing oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels. This sealing technique ensures the safety of oil and gas pipeline thermal operations and improves the efficiency of thermal construction. After construction, applying external environmental stimuli to the residual hydrogel in the pipeline causes it to transform into a liquid, thereby completely unsealing the pipeline and ensuring the safety and stability of subsequent pipeline operations.

[0126] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0127] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for sealing and unblocking oil and gas pipelines in thermal operations based on stimulus-responsive hydrogels, characterized in that, The method includes the following steps: A stimulus-responsive hydrogel was obtained; The stimulus-responsive hydrogel is injected into the pipe as a sealing material to achieve sealing; After the pipeline is sealed, thermal cutting and thermal welding are performed to complete the pipeline replacement. Inject unblocking material into the replaced pipe to complete the unblocking process; The amount of sealing material used in the thermal cutting section is based on Formula 1: Sure; In Formula 1: Q represents the amount of sealing material used at the thermal cutting section, in liters; D represents the outer diameter of the pipe, in millimeters; h represents the pipe wall thickness, in millimeters; and L represents the sealing distance, in millimeters. The total amount of the sealing material injected is 3 to 5 times the amount of sealing material used in the thermal cutting section; The stimulus-responsive hydrogel's stimulus-response mode includes at least one of temperature stimulus response, redox stimulus response, and acid-base stimulus response; The gelation driving forces of the stimulus-responsive hydrogel include at least one of Schiff base bonds, borate ester bonds, disulfide bonds, thiol-thioester exchange interactions, hydrogen bonds, π-π conjugation interactions, hydrophobic interactions, ionic interactions, electrostatic interactions, and host-guest interactions. Among them, an acid-base responsive hydrogel cross-linked with imine bonds is used as the sealing material. The preparation method of the acid-base responsive hydrogel cross-linked with imine bonds includes the following process: The polyamine compound solution and the first crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base responsive hydrogel crosslinked with imine bonds. The polyamine compound solution has a weight percentage concentration of 1wt% to 5wt%, the first crosslinking agent solution has a weight percentage concentration of 8wt% to 12wt%, and the weight ratio of the polyamine compound solution to the first crosslinking agent solution is (5 to 10):(1 to 5). The polyamino compound includes at least one of chitosan, polyethyleneimine, and gelatin; the structural formula of the first crosslinking agent is shown in formula (I); Equation (I): n is 45~230; Alternatively, an acid-base responsive hydrogel crosslinked with borate ester bonds can be used as a sealing material. The preparation method of the acid-base responsive hydrogel crosslinked with borate ester bonds includes the following steps: The polyhydroxy compound solution and the second crosslinking agent solution were stirred and mixed, and then allowed to stand to obtain the acid-base stimuli-responsive hydrogel crosslinked by borate ester bonds. The polyhydroxy compound solution has a weight percentage concentration of 2wt% to 10wt%, the second crosslinking agent solution has a weight percentage concentration of 0.5wt% to 5wt%, and the weight ratio of the polyhydroxy compound solution to the second crosslinking agent solution is (1~5):(1~5). The polyhydroxy compound includes at least one of guar gum, polyvinyl alcohol, and tannic acid; the second crosslinking agent is a compound containing a boric acid structure, and the compound containing a boric acid structure includes at least one of borax, 3-carboxyphenylboronic acid, and 4-carboxyphenylboronic acid. Alternatively, a hydrogen-bonded cross-linked temperature-stimulated hydrogel can be used as the sealing material. The preparation method of the hydrogen-bonded cross-linked temperature-stimulated hydrogel includes the following steps: The functional monomer, acrylamide, and photoinitiator were formulated into a solution with a weight fraction of 0.5% to 5%, and photoinitiated polymerization was carried out using a UV lamp to obtain the temperature-stimulated hydrogel with hydrogen bonding crosslinking. The photoinitiator is 2% by weight of the total mass of the functional monomer and acrylamide; The weight ratio of the functional monomer to the acrylamide is (5~10):(1~5). The structural formula of the functional unit is shown in formula (II); Equation (II): .

2. The method for sealing and unblocking oil and gas pipelines using stimulus-responsive hydrogels for thermal operations according to claim 1, characterized in that, The unblocking material includes at least one of the following: acidic or alkaline solutions, redox solutions, solutions at 60-90°C, and solutions with high salt concentrations.

3. The method for sealing and unblocking oil and gas pipelines using stimulus-responsive hydrogels for thermal operations according to claim 1, characterized in that, Before injecting the sealing material into the pipeline, construction preparation work is carried out on the pipeline in the sealing area; the construction preparation work includes depressurizing and cleaning the pipeline in the sealing area.

4. The method for sealing and unblocking oil and gas pipelines using stimulus-responsive hydrogels for thermal operations according to claim 1, characterized in that, After the pipeline is unblocked by injecting unblocking material, the pipeline welds are inspected and diagnosed using an ultrasonic diagnostic instrument or XRD instrument to determine the effectiveness of the pipeline repair.

Images