A repair material for leakage of injection-production wells of hydrogen storage reservoir and a preparation method thereof

Abstract

This invention discloses a repair material for leakage in hydrogen storage reservoir injection and production wells and its preparation method. Belonging to the technical field of repair materials for hydrogen storage reservoir injection and production wells, this invention introduces fluorine-containing long chains and chemical anchoring groups into the graphene oxide aerogel framework through molecular structure design, constructing a dual defense system of "hydrogen-repellent barrier - interface anchoring." Utilizing the low surface energy of the fluorine-containing groups, a gas slip boundary is constructed on the microporous wall, and the directional layered structure of the aerogel extends the gas diffusion path, significantly blocking hydrogen permeation from a physical perspective. Through the in-situ volcanic ash reaction between the anchoring component and the hydration products of old cement in the wellbore, a high-strength C-S-H gel is generated at the repair interface, achieving chemical bonding and mechanical interlocking between the material and the crack wall. This solves the shortcomings of traditional materials, such as easy peeling and poor resistance to high-pressure erosion, providing a low-cost and highly reliable repair material for long-term sealing of hydrogen storage reservoir wellbores.

Description

Technical Field

[0001] This invention belongs to the technical field of repair materials for hydrogen storage reservoir injection and production wells, specifically relating to a repair material for leakage in hydrogen storage reservoir injection and production wells and its preparation method. Background Technology

[0002] The renovation of old wellbore in salt cavern gas storage facilities is an important development direction for large-scale underground hydrogen storage projects. As the crucial link between surface facilities and underground storage chambers, the sealing integrity of injection and production wells directly affects the operational safety of the storage area. Unlike newly constructed wells, renovation projects face extremely unique operational challenges: after long-term service with natural gas injection and production, the cement sheath of the original wellbore often suffers damage such as microcracks or interface peeling due to ground stress and alternating loads, posing a safety hazard for subsequent high-pressure hydrogen storage. The mechanism of hydrogen leakage in injection and production wells is far more complex than that of natural gas. On the one hand, hydrogen molecules have extremely small diameters and high diffusion coefficients, making them highly susceptible to penetrating micron-sized cracks in aged cement sheaths or flowing along the cement-formation interface. Conventional airtightness standards are insufficient to meet the high permeability of hydrogen. On the other hand, hydrogen-rock reactions in the downhole environment are often overlooked. Once escaped hydrogen comes into contact with caprock mudstone, it can easily reduce iron minerals in the rock skeleton, inducing increased rock porosity and strength degradation, thereby forming new secondary leakage channels in the surrounding rock of the wellbore and causing the sealing system to fail.

[0003] Current technologies for treating microcracks in wellbore primarily utilize Grade G cement slurry or epoxy resin materials, but both exhibit significant limitations in adaptability to high-pressure hydrogen storage scenarios. While ordinary organic resin materials offer acceptable initial sealing, they are highly susceptible to polymer chain swelling or hydrogen embrittlement under prolonged immersion in high-pressure hydrogen environments, leading to irreversible degradation of material performance. Traditional cement-based materials, due to their high curing shrinkage, struggle to achieve dense filling of microcracks, and their weak interfacial bonding with the aged well wall makes them prone to peeling and failure under repeated high-pressure displacement by hydrogen gas flow. Therefore, there is an urgent need to develop a novel repair material that balances efficient gas barrier properties with interfacial structural integrity to address the severe sealing challenges faced in converting old wellbore structures into hydrogen storage facilities. Summary of the Invention

[0004] The purpose of this invention is to provide a repair material and its preparation method for leakage in hydrogen storage reservoir injection and production wells. Through molecular structure design, fluorine-containing long chains and chemical anchoring groups are introduced into the graphene oxide aerogel framework to construct a dual defense system of "hydrogen-repellent barrier - interface anchoring". The low surface energy of the fluorine-containing groups is used to construct gas slip boundaries on the micropore walls, and the directional layered structure of the aerogel significantly extends the gas diffusion path, thereby greatly blocking hydrogen permeation from a physical level. In addition, by means of the in-situ volcanic ash reaction between the anchoring components and the hydration products of old cement in the wellbore, a high-strength CSH gel is generated at the repair interface, realizing chemical bonding and mechanical interlocking between the material and the fracture wall, effectively solving the shortcomings of traditional materials such as easy peeling and poor resistance to high-pressure erosion. The excellent shear thinning properties of this slurry take into account both deep injection and fixed-point sealing, providing a low-cost and highly reliable repair material for long-term sealing of hydrogen storage reservoir wellbores.

[0005] This invention is achieved through the following technical solution:

[0006] A repair material for leakage in injection and production wells of a hydrogen storage reservoir, comprising, by weight: 0.2-0.5 parts of component A, 1.4-3.1 parts of component B, 98-106 parts of component C, and 50-62 parts of water;

[0007] Component A is a modified graphene oxide aerogel;

[0008] Component B is a regulator, and the substances in the regulator are respectively calculated by mass percentage as follows: dispersant 65%-70%, defoamer 5%-10%, and salt-resistant water-loss reducing agent 25%-30%;

[0009] The C component is ultrafine cement.

[0010] Preferably, the dispersant is either a polycarboxylate superplasticizer or a sulfonated melamine-formaldehyde condensate.

[0011] Preferably, the defoamer is either an organosilicon defoamer or tributyl phosphate.

[0012] Preferably, the anti-salt water loss agent is either an AMPS copolymer or a polyanionic cellulose.

[0013] Preferably, the ultrafine cement has a particle size of 0.8-1μm.

[0014] A method for preparing a repair material for leakage in hydrogen storage reservoir injection and production wells includes the following steps:

[0015] S1: Preparation of modified graphene oxide aerogel;

[0016] S2: Add water and regulator to the mixing container, stir at 300-500 r / min for 2-4 min, then add modified graphene oxide aerogel and stir for 1-2 min;

[0017] S3: Add ultrafine cement evenly while stirring. After all the cement has been added, increase the speed to 1000-1500 r / min and stir for 15-20 minutes to obtain the repair material.

[0018] Preferably, in step S1, the modified graphene oxide aerogel is a hydrogen-modified graphene oxide aerogel, and the preparation of the hydrogen-modified graphene oxide aerogel includes the following steps:

[0019] D1: Mix 1.5-2.5 g of perfluorodecyltriethoxysilane, 0.8-1.5 g of nano-silica dispersion and 50 mL of anhydrous ethanol to prepare mixed solution A;

[0020] D2: Add mixed solution A dropwise into 500 mL of graphene oxide dispersion and stir at 60 °C for 12 h. After the reaction is complete, centrifuge and discard the supernatant to obtain mixed solution B.

[0021] D3: Wash the mixed solution B with a mixture of anhydrous ethanol and deionized water to obtain a precipitate. Redisperse the precipitate in anhydrous ethanol to obtain a PFDS-GO dispersion.

[0022] D4: At 500 r / min, 18-22 mL of tetraethyl orthosilicate and 8-12 mL of ammonia were rapidly added to the PFDS-GO dispersion. The mixture was allowed to stand at 40℃ for 5-7 h to obtain a wet gel. The wet gel was then injected into a mold and transferred to a directional freeze dryer for 12 h, followed by drying for 48 h to obtain a blocky hydrogen-modified graphene oxide aerogel with a directional pore structure.

[0023] Preferably, in step D2, before adding the mixed solution A to the graphene oxide dispersion, the graphene oxide dispersion needs to be pretreated. The specific steps of the pretreatment are as follows: place the graphene oxide dispersion in a flask and stir it at 300 r / min for 30-40 min in a 40℃ water bath to make it uniformly dispersed.

[0024] Preferably, in step S1, the modified graphene oxide aerogel is an aminosilane-functionalized / reduced graphene oxide aerogel. The preparation of the aminosilane-functionalized / reduced graphene oxide aerogel includes the following steps:

[0025] R1: Mix 48 mL of anhydrous ethanol and 12 mL of deionized water, add 2.5-3 g of 3-aminopropyltriethoxysilane and 1-2 g of perfluorooctyltriethoxysilane to the mixed solvent and stir until homogeneous to obtain mixture C;

[0026] R2: Add mixture C to the graphene oxide dispersion, transfer it to a hydrothermal reactor with a polytetrafluoroethylene liner, seal the reactor lid, place the reactor in a forced-air drying oven, heat to 90-100℃, and react at a constant temperature for 5-7 hours to obtain a hydrogel.

[0027] R3: After the reactor cools down naturally, remove the hydrogel and immerse it in deionized water. Change the water every 4 hours and repeat the washing process several times. Then immerse the hydrogel in tert-butanol. Remove it after 8 hours of immersion and replace the tert-butanol for immersion again. Repeat this process several times. Then transfer the hydrogel to a directional freeze dryer and freeze it for 12 hours. Then dry it for 48 hours to obtain aminosilane-functionalized / reduced graphene oxide aerogel.

[0028] Preferably, in step R2, when adding the mixture C to the graphene oxide dispersion, the pH value is adjusted to 10.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1) In this invention, through molecular structure design, fluorine-containing long chains and chemical anchoring groups are introduced into the graphene oxide aerogel framework to construct a dual defense system of "hydrogen-repellent barrier - interface anchoring". The low surface energy of the fluorine-containing groups is used to construct gas slip boundaries on the micropore walls. Combined with the directional layered structure of the aerogel, the gas diffusion path is significantly extended, which greatly blocks hydrogen permeation from a physical level. In addition, by means of the in-situ volcanic ash reaction between the anchoring components and the hydration products of old cement in the wellbore, a high-strength CSH gel is generated at the repair interface, realizing the chemical bonding and mechanical interlocking between the material and the crack wall, effectively solving the shortcomings of traditional materials such as easy peeling and poor resistance to high-pressure erosion. The excellent shear thinning properties of this slurry take into account both deep injection and fixed-point sealing, providing a low-cost and highly reliable repair material for long-term sealing of hydrogen storage wellbores.

[0031] 2) In this invention, modified graphene oxide aerogel is mixed with ultrafine cement, water, dispersant, salt-resistant water-loss reducing agent, and defoamer to prepare a composite repair slurry. The modified aerogel has significant water and gas repellency properties. During the slurry mixing process, water molecules have difficulty entering the nanopores of the modified graphene oxide aerogel, thus ensuring the integrity of its internal air pocket structure. The unique "shear-thinning" rheological properties of aerogel are used to solve the transportation problem. Under the high shear rate of pumping, the viscosity of the repair material decreases, and it becomes fluid, making it easy to transport to the deep part of the well and penetrate into micron-level fractures. When the slurry enters the fracture and stops, the aerogel skeleton quickly recovers and the viscosity increases dramatically, achieving fixed-point retention without leakage, ensuring the sealing effect of small gaps in the injection and production wells.

[0032] 3) In this invention, regulators optimize slurry performance through synergistic control. Dispersants (polycarboxylate superplasticizers or sulfonated melamine-formaldehyde condensates) improve the wettability of hydrophobic aerogels through surface activity, overcoming the problem of agglomeration and floating in the aqueous phase; anti-salt water loss agents control filtration loss through molecular chain adsorption, ensuring the hydration stability of the slurry in salt rock formations; defoamers effectively eliminate agitation bubbles, avoiding internal defects in the solidified body. The combination of these three ensures that the repair material maintains excellent pumpability and suspension stability even at low water-cement ratios.

[0033] 4) In this invention, during the preparation of hydrogen-modified graphene oxide aerogel, perfluorodecyltriethoxysilane is used to introduce fluorine-containing long chains onto the surface of graphene oxide, reducing the surface energy of the material and effectively blocking hydrogen adsorption. Simultaneously loaded nano-silica provides active sites, which can subsequently react chemically with cement hydration products, enhancing interfacial adhesion. A directional freezing process is employed, controlling the solvent crystallization direction to form a directional pore structure perpendicular to the gas permeation direction within the aerogel. This structure significantly extends the hydrogen penetration path within the material, thereby greatly improving the physical barrier properties.

[0034] 5) In this invention, a "one-pot hydrothermal reduction" strategy is adopted in the preparation of aminosilane-functionalized / reduced graphene oxide aerogel, simultaneously completing framework repair and chemical grafting. The high-temperature, high-pressure environment promotes the reduction of graphene oxide, restoring the structural stability of the graphene layers; the active amino groups grafted with 3-aminopropyltriethoxysilane (APTES) can form strong covalent bonds with the cement matrix. Furthermore, a tert-butanol solvent replacement process is introduced, utilizing its low surface tension to effectively suppress capillary shrinkage during drying, preventing the aerogel framework from collapsing, thereby ensuring the structural integrity and stability of the modified aerogel after molding. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The images show a comparison of the microstructure and mechanical properties of the repair material prepared in the embodiments of this invention with the control group cement stone, as well as a comparison of the mechanical property improvements. Detailed Implementation

[0037] 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 some embodiments of the present invention, but not all embodiments.

[0038] In the development of repair materials for leaking injection and production wells in hydrogen storage facilities, graphene oxide aerogel was modified through molecular structure design. Fluorine-containing long chains and chemical anchoring groups were introduced into the graphene oxide aerogel framework, constructing a dual defense system of "hydrogen-repellent barrier - interface anchoring." First, the low surface energy of the fluorine-containing groups is used to construct gas slip boundaries on the micropore walls. Combined with the directional layered structure of the aerogel, this significantly extends the gas diffusion path, substantially blocking hydrogen permeation at the physical level. Then, through the in-situ volcanic ash reaction between the anchoring components and the hydration products of old cement in the wellbore, a high-strength CSH gel is generated at the repair interface. This achieves chemical bonding and mechanical interlocking between the material and the fracture wall, effectively solving the shortcomings of traditional materials such as easy peeling and poor resistance to high-pressure erosion. Furthermore, the excellent shear-thinning properties of the repair material balance deep injection and targeted sealing, ensuring the reliability of long-term sealing of the hydrogen storage wellbore.

[0039] The modification principle of graphene oxide aerogel, substrate selection and preparation: Graphene oxide (GO), rich in multiple modification sites, is selected as the substrate. The abundant oxygen-containing functional groups (hydroxyl, epoxy, carboxyl groups) on the GO surface are not only easy to modify, but also provide extremely strong adsorption active sites.

[0040] Hydrogen-repellent modification: Graphene oxide (GO), rich in multiple modification sites, is selected as the substrate and subjected to dual chemical modification using its abundant oxygen-containing functional groups. First, a fluorinated long-chain silane coupling agent (such as perfluorodecyltriethoxysilane) is introduced. The fluorinated long chain possesses extremely low surface energy, constructing a "low surface energy gas slip boundary" on the microporous surface of the material. This modified layer utilizes the steric hindrance effect of the fluorine chain to significantly reduce the van der Waals adsorption force of hydrogen molecules on the material surface, preventing hydrogen penetration and diffusion. Second, the silanol groups generated from silane hydrolysis can chemically bond with hydration products (such as CSH gel) in the wellbore cement sheath, forming "Si-O-Si" covalent bonds, ensuring that the repair material is tightly adsorbed onto the cement crack wall and does not detach.

[0041] Interface anchoring and intercalation reinforcement: Addressing the issue of weak interfacial bonding between traditional organic materials and inorganic cement matrices, and their susceptibility to detachment under high-pressure hydrogen displacement, an interface anchoring agent (such as nano-silica or 3-aminopropyltriethoxysilane) is introduced into the GO layers. This anchoring agent is rich in active silanol or amino groups, playing a functional bridging role: on the one hand, this component enters the GO interlayer, maintaining the interlayer spacing through spatial support and inhibiting the aggregation and stacking of graphene oxide sheets during the drying process, thereby maintaining the structural integrity of the microporous channels; on the other hand, after the material enters the wellbore fracture, the anchoring agent can react with the hydration products (Ca(OH)2) on the cement fracture surface to form a pozzolanic reaction, generating in-situ anchoring calcium silicate (CSH) gel at the interface. Through this in-situ mineralization effect, the repair material and the cement microcrack surface form a composite structure of chemical bonding and physical-mechanical interlocking, significantly improving the shear strength of the interface and ensuring that the repair layer does not delaminate under high-pressure hydrogen flow.

[0042] Aerogelation treatment: Modified GO hydrogel is freeze-dried to remove the solvent, yielding modified graphene oxide aerogel with a directional microporous structure. Aerogelation treatment results in extremely low material density, facilitating transport.

[0043] Preparation and transportation of repair materials: The prepared modified graphene oxide aerogel is mixed with ultrafine cement, water, and dispersant to form a composite repair slurry. Due to the significant water and gas repellency of the modified graphene oxide aerogel, water molecules have difficulty entering the nanopores of the aerogel during the slurry mixing process, thus ensuring the integrity of its internal air pocket structure. The unique "shear-thinning" rheological properties of aerogel are utilized to solve the transportation problem: Under the high shear rate of pumping, the viscosity of the slurry decreases, becoming fluid, making it easy to transport to deep underground parts and penetrate into micron-sized fractures; when the slurry enters the fracture and stagnates (low shear rate), the aerogel skeleton rapidly recovers, and the viscosity increases dramatically, achieving fixed-point retention without leakage.

[0044] Example 1:

[0045] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. The modified graphene oxide aerogel was hydrogen-repellent modified graphene oxide aerogel, consisting of 0.2g of modified graphene oxide aerogel; 1.4g of regulator, which was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% silicone defoamer, and 25% AMPS copolymer; 98g of ultrafine cement, with a particle size of 1μm; and 50g of water.

[0046] Water and a regulator were added to a mixing container and stirred at 300 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added uniformly while stirring. After all the cement was added, the speed was increased to 1000 r / min and stirred for 15 min to obtain 149.6 g of repair material.

[0047] Example 2:

[0048] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. Modified graphene oxide aerogel was prepared by using aminosilane functionalized / reduced graphene oxide aerogel. 0.2g of modified graphene oxide aerogel was used; 1.4g of regulator was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% organosilicon defoamer, and 25% AMPS copolymer; 98g of ultrafine cement with a particle size of 1μm was also used; and 50g of water was added.

[0049] Water and a regulator were added to a mixing container and stirred at 300 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added uniformly while stirring. After all the cement was added, the speed was increased to 1000 r / min and stirred for 15 min to obtain 149.6 g of repair material.

[0050] Example 3:

[0051] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. The modified graphene oxide aerogel was hydrogen-repellent modified graphene oxide aerogel, consisting of 0.5g of modified graphene oxide aerogel; 1.4g of regulator, which was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% silicone defoamer, and 25% AMPS copolymer; 98g of ultrafine cement, with a particle size of 1μm; and 50g of water.

[0052] Water and a modifier were added to a mixing container and stirred at 300 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added uniformly while stirring. After all the cement was added, the speed was increased to 1000 r / min and stirred for 15 min to obtain 149.9 g of repair material.

[0053] Example 4:

[0054] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. Modified graphene oxide aerogel was prepared by using aminosilane functionalized / reduced graphene oxide aerogel. 0.5g of modified graphene oxide aerogel was used; 1.4g of regulator was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% organosilicon defoamer, and 25% AMPS copolymer; 98g of ultrafine cement with a particle size of 1μm was also used; and 50g of water was used.

[0055] Water and a modifier were added to a mixing container and stirred at 300 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added uniformly while stirring. After all the cement was added, the speed was increased to 1000 r / min and stirred for 15 min to obtain 149.9 g of repair material.

[0056] Example 5:

[0057] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. The modified graphene oxide aerogel was hydrogen-repellent modified graphene oxide aerogel, consisting of 0.2g of modified graphene oxide aerogel; 3.1g of regulator, which was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% silicone defoamer, and 25% AMPS copolymer; 106g of ultrafine cement, with a particle size of 1μm; and 62g of water.

[0058] Water and a regulator were added to a mixing container and stirred at 500 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added evenly while stirring. After all the cement was added, the speed was increased to 1500 r / min and stirred for 15 min to obtain 171.3 g of repair material.

[0059] Example 6:

[0060] Repair materials for leakage in hydrogen storage reservoir injection and production wells were prepared. Modified graphene oxide aerogel was prepared by using aminosilane functionalized / reduced graphene oxide aerogel. 0.2g of modified graphene oxide aerogel was used; 3.1g of regulator was prepared by mixing the components in the following mass percentages: 68% polycarboxylate superplasticizer, 7% organosilicon defoamer, and 25% AMPS copolymer; 106g of ultrafine cement with a particle size of 1μm was also used; and 62g of water was used.

[0061] Water and a regulator were added to a mixing container and stirred at 500 r / min for 4 min. Then, modified graphene oxide aerogel was added and stirred for 2 min. Ultrafine cement was added evenly while stirring. After all the cement was added, the speed was increased to 1500 r / min and stirred for 15 min to obtain 171.3 g of repair material.

[0062]

[0063] Table 1: Comparison of Hydrogen Permeability Performance of Different Remediation Materials

[0064] Table 1 shows that the hydrogen permeability of ordinary cement slurry decreased by orders of magnitude after the addition of graphene oxide aerogel, with a reduction of over 99.5% compared to ordinary Grade G cement slurry (1.250 mD). This indicates that the barrier network constructed by the modified aerogel in the cement matrix effectively cut off the microscopic seepage channels of gas. 100g of the repair material prepared in each example was used to conduct pressure tests on the wellbore wall after repair in simulated injection-production wells. The gas sealing pressure of the wellbore wall increased from 14.8 MPa / m before repair to 19.5 MPa / m. High-pressure scouring experiments further confirmed that the interface anchoring effect significantly improved the bonding stability of the repair layer, and no peeling failure occurred under high pressure differential. Furthermore, thanks to the dense physical sealing and hydrogen-repellent barrier properties of the repair material, the contact path between hydrogen and formation rock was effectively cut off, thus effectively inhibiting the hydrogen-rock reaction and achieving long-term sealing of the wellbore.

[0065] Example 3, based on Example 1, appropriately increased the dosage of modified graphene oxide aerogel (from 0.2g to 0.5g). The resulting repair material exhibited the lowest hydrogen permeability (reaching 0.002 mD), representing the optimal barrier effect within this material system. This indicates that, provided the dispersant and stirring process are well-coordinated, appropriately increasing the concentration of functional filler can significantly enhance the density of the hydrogen-repellent physical barrier within the matrix, effectively cutting off more microscopic leakage channels and maximizing the physical shielding effect against hydrogen molecules, thereby achieving ultimate sealing against ultra-high pressure hydrogen.

[0066] like Figure 1 As shown, Figure 1 The photograph after repair shows the microstructure of the wellbore wall after repair using the repair material prepared according to Example 1. The photograph of the control group shows the microstructure of ordinary Grade G cement paste. As can be seen from the figure, the surface of the control group is loose and there are obvious microcracks, while the structure of the repaired material is dense, the microcracks have been filled and healed, and the modified aerogel is tightly bonded to the matrix to form a complete sealing layer.

[0067] Example 7:

[0068] A method for preparing a repair material for leakage in hydrogen storage reservoir injection and production wells involves first preparing modified graphene oxide aerogel. In this embodiment, the modified graphene oxide aerogel is a hydrogen-repellent modified graphene oxide aerogel. To prepare the hydrogen-repellent modified graphene oxide aerogel, 2.1g of perfluorodecyltriethoxysilane (PFDS, >97%) and 1.3g of nano-silica dispersion (particle size 10-20nm, anchoring agent) are first mixed in 50mL of anhydrous ethanol to obtain mixed solution A.

[0069] Next, 500 mL of graphene oxide (GO) dispersion with a concentration of 5 mg / mL (sheet diameter 1-20 μm) was measured and placed in a 500 mL three-necked round-bottom flask. The mixture was stirred at 300 r / min for 30 min in a 40℃ water bath to ensure uniform dispersion.

[0070] The mixed solution A was slowly added dropwise to the GO dispersion, and the mixture was stirred and reacted for 12 hours in a 60°C water bath. During this process, PFDS was grafted onto the edges of the GO sheets to construct hydrogen-repellent sites, while nano-silica was uniformly attached to the surface and interlayer of the GO sheets through hydrogen bonding and electrostatic interactions, forming highly reactive "mineralized seed crystals" that provide an interface for subsequent chemical bonding with cement walls.

[0071] After the reaction was complete, the mixture was transferred to a centrifuge tube and centrifuged at 8000 r / min for 3 min. The supernatant was discarded to obtain mixed solution B.

[0072] Mixture B was repeatedly washed by centrifugation with a mixture of anhydrous ethanol and deionized water (volume ratio 1:1) three times until the washing solution was colorless and transparent to completely remove unreacted reagents. The washed precipitate was then redispersed in 400 mL of an ethanol-water (volume ratio 1:1) mixed solvent to obtain a homogeneous PFDS-GO dispersion.

[0073] The mixture was stirred at 500 r / min, and 20 mL of tetraethyl orthosilicate (TEOS, >98%) and 10 mL of ammonia (25-28%) were rapidly added to the PFDS-GO dispersion. The system was then maintained at 40 °C and allowed to stand for 6 h, forming a three-dimensional network structure wet gel through hydrolysis and condensation reactions. During this process, the SiO2 network generated by TEOS hydrolysis intertwined with the modified GO, greatly enhancing the mechanical strength of the gel.

[0074] The obtained wet gel was injected into a long strip mold and immediately transferred to a directional freezing device. The freezing direction was set perpendicular to the long axis of the mold to simulate the direction perpendicular to the crack propagation direction. The temperature was programmed to drop to -30℃ at a rate of 1℃ / min and held for 12 hours. The temperature gradient was used to drive the solvent to solidify directionally, thereby forming a directionally distributed pore structure inside the material. Finally, the frozen sample was transferred to a freeze dryer and dried at -50℃ and a vacuum degree ≤10 Pa for 48 hours to obtain a blocky hydrogen-phobic modified graphene oxide aerogel material with a directional pore structure.

[0075] Preparation of repair material: When preparing the repair material, the amount of each component can be increased proportionally according to the content of each component in Example 3; add an appropriate amount of water and regulator to the stirring container, stir at 300 r / min for 2 min, then add the above-mentioned hydrogen-modified graphene oxide aerogel, stir for 2 min, and uniformly add ultrafine cement while stirring. After all the cement has been added, increase the speed to 1000 r / min and stir for 15 min to obtain the repair material.

[0076] The repair material prepared by using hydrogen-modified graphene oxide aerogel through the above method integrates directional physical shielding, low surface energy chemical hydrogen repellency, and active interface anchoring. Physically, it significantly extends the gas diffusion path, and chemically, it effectively repels hydrogen adsorption. At the same time, the material has excellent interfacial reactivity and can form a high-strength chemical anchor with the wellbore wall, achieving a balance between the density, adhesion, and durability of the repair layer.

[0077] Example 8:

[0078] A method for preparing a repair material for leakage in hydrogen storage reservoir injection and production wells involves first preparing modified graphene oxide aerogel. In this embodiment, the modified graphene oxide aerogel is an aminosilane-functionalized / reduced graphene oxide aerogel. To prepare the aminosilane-functionalized / reduced graphene oxide aerogel, 48 mL of anhydrous ethanol and 12 mL of deionized water are first added to a beaker and mixed thoroughly. Then, 2.6 g of 3-aminopropyltriethoxysilane (APTES) and 1 g of perfluorooctyltriethoxysilane (PFOTS) are added to the mixed solvent as a chemical anchoring agent. The solution is stirred at room temperature for 1 hour to allow the two silanes to fully dissolve and pre-hydrolyze, thus preparing a functionalized mixed solution C.

[0079] Next, 500 mL of an aqueous dispersion of graphene oxide (GO) with a concentration of 4 mg / mL was measured and prepared for use.

[0080] A one-pot hydrothermal reduction and modification reaction was then carried out. Under stirring, the above mixed solution C was slowly added to the graphene oxide dispersion. Since APTES is alkaline after hydrolysis, the pH of the system will automatically increase, and the pH can be finely adjusted to 10.

[0081] The above mixture was transferred to a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner, with the filling degree controlled at approximately 70%, and the reactor lid was sealed. The reactor was then placed in a forced-air drying oven, heated to 100°C, and reacted at this temperature for 5 hours.

[0082] Under high temperature, high pressure, and alkaline conditions, the primary amine groups at the ends of the APTES molecular chains launch nucleophilic attacks on the epoxy groups on the surface of graphene oxide, resulting in a ring-opening reaction to form CN covalent bonds. Simultaneously, the high temperature environment induces a deoxygenation reduction reaction in graphene oxide, restoring its conjugated structure, which macroscopically manifests as the dispersion assembling into a black cylindrical hydrogel.

[0083] After the reaction was complete, the gel was allowed to cool naturally to room temperature, and the black hydrogel was removed. To remove unreacted residual monomers and free impurities, the hydrogel was dialyzed in deionized water, with the water changed every 4 hours for a total of 3 times. After cleaning, a solvent replacement step was performed. The hydrogel was immersed in tert-butanol, with the tert-butanol changed every 8 hours for a total of 3 times, until the water in the gel pores was completely replaced by tert-butanol. The purpose of using tert-butanol replacement was to reduce the surface tension of the solvent and, taking advantage of its low crystallization expansion rate, prevent the aerogel framework from collapsing during subsequent drying.

[0084] The displaced gel was transferred to a directional freezing device, with the freezing direction set perpendicular to the long axis of the mold to simulate the direction perpendicular to crack propagation. The temperature was programmed to decrease to -30°C at a rate of 1°C / min and held for 12 hours. This temperature gradient drove the solvent to solidify directionally, forming a directionally distributed porous structure within the material. Finally, the frozen sample was transferred to a freeze dryer and dried at -50°C and a vacuum degree ≤10 Pa for 48 hours to obtain aminosilane-functionalized / reduced graphene oxide aerogel.

[0085] Preparation of repair material: When preparing the repair material, the amount of each component can be increased proportionally according to the content of each component in Example 4; add an appropriate amount of water and regulator to the stirring container, stir at 300 r / min for 2 min, then add the above-mentioned hydrogen-modified graphene oxide aerogel, stir for 2 min, and uniformly add ultrafine cement while stirring. After all the cement has been added, increase the speed to 1000 r / min and stir for 15 min to obtain the repair material.

[0086] The repair material prepared by using aminosilane-functionalized / reduced graphene oxide aerogel in the above manner benefits from the graphene skeleton restored by hydrothermal reduction, which has excellent resistance to hydrogen aging. The grafted active amino groups and fluorine-containing long chains work together to achieve both hydrophobic repulsion of hydrogen molecules and covalent bonding with the cement interface, thereby ensuring long-term sealing performance under complex downhole conditions.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a repair material for leakage in hydrogen storage reservoir injection and production wells, characterized in that, Includes the following steps: S1: Preparation of modified graphene oxide aerogel; S2: Add water and regulator to the mixing container, stir at 300-500 r / min for 2-4 min, then add modified graphene oxide aerogel and stir for 1-2 min; S3: Add ultrafine cement evenly while stirring. After all the cement has been added, increase the rotation speed to 1000-1500 r / min and stir for 15-20 minutes to obtain the repair material. In step S1, the modified graphene oxide aerogel is a hydrogen-modified graphene oxide aerogel. The preparation of the hydrogen-modified graphene oxide aerogel includes the following steps: D1: Mix 1.5-2.5 g of perfluorodecyltriethoxysilane, 0.8-1.5 g of nano-silica dispersion and 50 mL of anhydrous ethanol to prepare mixed solution A; D2: Add mixed solution A dropwise into 500 mL of graphene oxide dispersion and stir at 60 °C for 12 h. After the reaction is complete, centrifuge and remove the supernatant to obtain mixed solution B. D3: Wash the mixed solution B with a mixture of anhydrous ethanol and deionized water to obtain a precipitate. Redisperse the precipitate in anhydrous ethanol to obtain a PFDS-GO dispersion. D4: At 500 r / min, 18-22 mL of tetraethyl orthosilicate and 8-12 mL of ammonia were rapidly added to the PFDS-GO dispersion. The mixture was allowed to stand at 40℃ for 5-7 h to obtain a wet gel. The wet gel was then injected into a mold and transferred to a directional freeze dryer for 12 h, followed by drying for 48 h to obtain a blocky hydrogen-modified graphene oxide aerogel with a directional pore structure.

2. The method for preparing the repair material for leakage in hydrogen storage reservoir injection and production wells as described in claim 1, characterized in that, In step D2, before adding the mixed solution A to the graphene oxide dispersion, the graphene oxide dispersion needs to be pretreated. The specific steps of the pretreatment are as follows: place the graphene oxide dispersion in a flask and stir it at 300 r / min for 30-40 min in a 40℃ water bath to make it uniformly dispersed.

3. A repair material for leakage in hydrogen storage reservoir injection and production wells, characterized in that, The repair material prepared by the method of preparing the repair material according to any one of claims 1 or 2; by mass parts: 0.2-0.5 parts of component A, 1.4-3.1 parts of component B, 98-106 parts of component C, and 50-62 parts of water; Component A is a modified graphene oxide aerogel; the modified graphene oxide aerogel is a hydrogen-repellent modified graphene oxide aerogel. Component B is a regulator, and the substances in the regulator are respectively calculated by mass percentage as follows: dispersant 65%-70%, defoamer 5%-10%, and salt-resistant water-loss reducing agent 25%-30%; The C component is ultrafine cement.

4. The repair material for leakage in hydrogen storage reservoir injection and production wells as described in claim 3, characterized in that, The dispersant is either a polycarboxylate superplasticizer or a sulfonated melamine-formaldehyde condensate.

5. The repair material for leakage in hydrogen storage reservoir injection and production wells as described in claim 3, characterized in that, The defoamer is either an organosilicon defoamer or tributyl phosphate.

6. The repair material for leakage in hydrogen storage reservoir injection and production wells as described in claim 3, characterized in that, The salt-resistant dehydration agent is either an AMPS copolymer or a polyanionic cellulose.

7. The repair material for leakage in hydrogen storage reservoir injection and production wells as described in claim 3, characterized in that, The particle size of the ultrafine cement is 0.8-1μm.

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