Method for controlling depleted gas reservoir hydrogen storage loss based on special material PdO (at) rGO

Abstract

The invention provides a bacteriostatic proppant technology based on a palladium oxide-reduced graphene oxide composite material, aiming at the problem of hydrogen loss caused by microbial activity in a hydrogen storage bank of an exhausted gas reservoir. A PdO (at) rGO composite material functionally modified by lead ions (Pb < 2 + >) is loaded on the surface of a porous ceramsite carrier to form an adsorption-inactivation-blocking synergistic antibacterial network; precise laying of the proppant in a crack network is achieved through the end sand removal technology, hydrogen consumption is reduced, and an efficient, economical and environment-compatible innovative solution is provided for biological pollution control of the underground hydrogen storage library.

Description

Technical Field

[0001] This patent relates to the field of hydrogen storage technology and is a method for controlling hydrogen loss in depleted gas reservoirs by causing bacteria to lose activity through a multi-stage action mechanism of special metal ion composite materials. Background Art

[0002] my country's total hydrogen production continues to grow rapidly, with annual production projected to reach 53 million tons by 2030. Safely and efficiently storing excess hydrogen is becoming a major challenge. Underground hydrogen storage utilizes underground structures to achieve large-scale, high-pressure gaseous storage of hydrogen. It offers advantages such as high safety, low cost, large scale, and long lifespan. Underground hydrogen storage facilities include salt caverns and depleted gas reservoirs. Salt caverns maintain a periodic temperature of 35°C to 45°C, which is the optimal temperature range for the growth of hydrogen-consuming bacteria. Depleted gas reservoirs offer advantages such as suitable geological conditions, readily available storage space, reusable infrastructure, high safety, and significantly reduced costs, making them ideal locations for large-scale hydrogen storage. Depleted gas reservoirs have high biomass and activity. The presence of gases such as methane, nitrogen, and carbon dioxide mixed with hydrogen in the reservoirs increases the complexity of microbial reactions. At the Lobodice hydrogen-rich underground gas storage facility in the Czech Republic, methanogens caused up to 17% hydrogen loss over a seven-month storage period. For established storage facilities, it is necessary to promptly understand the impact of microbial reactions on hydrogen loss and take corresponding measures. Summary of the Invention

[0003] In response to the problem of hydrogen loss caused by microbial reactions, this patent proposes a method for controlling hydrogen loss in hydrogen storage reservoirs, which can avoid chemical reactions between hydrogen and microorganisms in the storage reservoir. The technical solution is as follows:

[0004] S1: Preparation of pre-oxidized expanded graphite;

[0005] S2: Preparation of PdO@rGO composites;

[0006] S3: Preparation of porous ceramsite proppant;

[0007] S4: injecting the prepared proppant into the formation through the end screenout technique;

[0008] S5: Fluorescent labeling for proppant distribution uniformity assessment;

[0009] S6: Preparation of culture medium to detect bacterial content in the formation.

[0010] Furthermore, in step S1, the pre-oxidized expanded graphene has high adsorption and active surface. The pre-oxidation treatment significantly increases the specific surface area of ​​graphene to be higher than that of ordinary graphene or activated carbon, and enhances the adsorption capacity of heavy metal ions and organic pollutants (such as benzene series). In addition, the pre-oxidized expanded graphene is rich in oxygen-containing functional groups, and functional groups such as carboxyl and hydroxyl groups selectively adsorb specific ions through chemical bonding, which is very effective for Pb 2+ The adsorption efficiency of metal ions is significantly improved. PdO nanoparticles serve as a loading substrate. Their high conductivity and chemical activity promote the uniform anchoring of PdO, laying the foundation for the synergistic effect of subsequent composite materials.

[0011] Furthermore, in step S2, the PdO@rGO composite material is regenerable and can desorb pollutants through acid washing or high-temperature treatment. After being recycled five times, the adsorption efficiency still remains above 85%. The high conductivity of rGO (10S / m) can eliminate static electricity on the surface of the proppant and reduce particle agglomeration. At the same time, the composite material is resistant to high temperatures and salt, and is suitable for highly mineralized formations.

[0012] Furthermore, in step S3, after the porous ceramsite proppant ceramsite surface micropores are loaded with the composite material, Pb can be slowly released in the fracturing fluid environment. 2+ , continuously inhibiting the growth of SRB for more than 6 months, avoiding the problem of short-term failure of conventional fungicides.

[0013] Furthermore, in step S4, the end desanding ensures that the proppant is concentrated in the main channel of the fracture, avoiding ineffective settlement of the distal fracture and improving the fracture conductivity. In addition, the end desanding technology can optimize the rheological properties of the sand-carrying fluid and avoid particle breakage based on the porous structure of PdO@rGO.

[0014] Furthermore, in step S5, the fluorescent labeling method is used to evaluate the uniformity of proppant distribution. The combination of laser ablation and ICP-MS achieves micron-level resolution and accurately locates proppant accumulation or blank areas, which is superior to traditional CT scanning. In addition, this method does not require core sampling or destruction of fracture structure and is a non-destructive evaluation.

[0015] Furthermore, in step S6, the bacterial content is monitored by using a culture medium preparation method, which can fully simulate the formation conditions, has a strong anti-interference ability, and avoids interference from other ions.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] (1) Pb 2+ The modified proppant technology achieves a triple mechanism of long-term antibacterial, physical barrier and environmental adaptation.

[0018] (2) Through carrier immobilization design, lead ions are confined to the proppant-formation interface, effectively preventing heavy metal ions from migrating to the aquifer, thereby achieving efficient antibacterial effects while minimizing environmental risks.

[0019] (3) The high charge density of lead ions can enhance the zeta potential of the proppant surface, improve its suspension stability in the fracture, and thus optimize the uniformity of proppant placement, forming a physical-chemical synergistic antibacterial mechanism.

[0020] (4) It provides a basic framework for the composite modification of multiple metal ions. In the future, dynamic optimization of antibacterial performance and environmental adaptability can be achieved by regulating the type of ions and the loading ratio.

[0021] (5) PdO@rGO leverages the high specific surface area and porous structure of rGO to achieve efficient physical adsorption of bacteria. PdO nanoparticles enhance the density of active sites on the material surface, precisely disrupting the microbial membrane structure through charge interactions. The porous nature of the ceramsite carrier ensures uniform dispersion of the material, preventing localized agglomeration and improving antibacterial contact efficiency and formation permeability.

[0022] (6) The ceramic skeleton provides mechanical support and chemical inertness for the composite material, resisting erosion by formation water ions and high-pressure shearing, and maintaining the long-term stability of the PdO@rGO active component. Its three-dimensional pore structure simultaneously optimizes the material's sustained-release properties and prolongs the antibacterial cycle.

[0023] (7) Compared with traditional chemical agents, this technology reduces the dosage of toxic substances through the physical adsorption-chemical inactivation coupling mechanism; the ceramsite carrier can be reused after elution and regeneration, which significantly reduces the risk of secondary pollution and waste disposal costs, and meets the development needs of green hydrogen storage technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a synthetic modified proppant;

[0026] Figure 2 This is a diagram of the fracturing process parameters and steps;

[0027] Figure 3 This is a structural diagram of end sand removal;

[0028] Figure 4 Schematic diagram of the overall structure of the underground hydrogen storage after injection of sand body; Figure 5 Flowchart of a method for preventing hydrogen loss in underground hydrogen storage. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0030] 150 mL of concentrated H2SO4, 50 mL of concentrated HNO3 and 5 g of 800-mesh vermicular graphite powder were added to a 500 mL round-bottom flask in sequence. After stirring at room temperature for 24 h, 1 L of ultrapure water was slowly added to dilute the mixture. The reaction product was filtered and washed, and then dried to obtain vermicular graphite powder.

[0031] The obtained worm graphite powder, 300 ml concentrated H2SO4, 4.2 g K2S2O4 and 6.2 g P2O5 were added to a round-bottom flask in sequence, stirred at 80°C for 5 h, and then slowly added with ultrapure water for dilution. The mixture was filtered, washed and dried to obtain pre-oxidized expanded graphite.

[0032] After mixing the above product with 200ml concentrated H2SO4, 15gK2MnO4 was slowly added at below 15°C and the temperature was raised to 35°C. Stirring was continued for 6 hours. 2L ultrapure water and 10mL 30% H2O2 were added until the solution turned bright yellow. Dilute HCl was added for washing, and then the solution was repeatedly washed with ultrapure water and centrifuged until the pH of GO was close to neutral. After standardization of the product, a GO solution was prepared.

[0033] The GO solution was mixed with a saturated Pb(NO3)2 solution. Ultrasonication was applied to the mixture at room temperature for 3 hours and continuous stirring for 12 hours. The mixture was then filtered and the filter cake was immersed in a 22% (mass) ammonium hydroxide solution and stirred for 3 hours. The solid was filtered and washed several times before being calcined in a vacuum furnace at 500°C for 3 hours to obtain PdO@rGO.

[0034] 4 kg of 200-mesh (particle size <0.075 mm) bauxite and potassium feldspar powders were weighed in a ratio of 79% and 21%, respectively, and doped with approximately 100 g of the PdO@rGO product. The mixture was then pelletized in a high-pressure mixer with a water content of 10% to 12% of the powder weight. The pellets were air-dried, sieved through a 40-70 mesh (0.212 mm <0.425 mm) sieve, and sintered in a high-temperature furnace at 1260°C for 2 hours at a heating rate of 5°C / min to produce the PdO@rGO proppant.

[0035] After preparing the composite PdO@rGO material proppant, rhodamine B or rare earth doped fluorescent nanoparticles (such as Eu3+ / Tb 3+ The complex) is embedded into the surface coating of the ceramsite as a tracer to prepare for the subsequent verification of the uniformity of the proppant distribution.

[0036] First, according to the transformation needs of the underground hydrogen storage, the pre-set fracture length L f , seam width W f , calculate the filtration loss of fracturing fluid. The calculation formula for filtration loss is:

[0037]

[0038] Δp=(g f H)-p0 (2)

[0039]

[0040] The comprehensive filtration coefficient C is:

[0041]

[0042] Where: C v ——Fracturing fluid loss coefficient controlled by viscosity, m / min 0.5 ;

[0043] C C ——Fracturing fluid loss coefficient at the point controlled by reservoir fluid compressibility, m / min 0.5 ;

[0044] C W ——Fracturing fluid loss coefficient at the control point of the wall performance, m / min 0.5 ;

[0045] K – reservoir permeability, D;

[0046] φ——reservoir porosity, %;

[0047] μ——Viscosity of fracturing fluid under reservoir conditions, mPa·s;

[0048] g f ——Fracturing pressure gradient, MPa / m;

[0049] H - reservoir depth, m;

[0050] p0——reservoir pressure, MPa;

[0051] Δp——pressure difference across the crack surface, MPa;

[0052] C f ——compressibility coefficient of reservoir fluid, MPa-1;

[0053] μ′——reservoir fluid viscosity, mPa·S;

[0054] Calculate the desanding time (time required to reach the fracture length) and the efficiency of the fracturing fluid at that moment, and reach the desanding time t ∞ for:

[0055]

[0056] Where: H f ——crack height, m.

[0057] Fracturing fluid efficiency at the time of screenout so for:

[0058]

[0059] Where: V sp ——Fracturing fluid initial filtration loss, m 3 / m 2 .

[0060] Calculate the initial time t to start pumping low sand ratio sand-carrying fluid LS .

[0061] t LS =[(1-e SO )+S F ] (7)

[0062] Where: S F ——Additional amount to ensure the safety of fracturing fluid, such as small amount of fracturing pre-fluid, S F It can be taken as 0.03~0.05.

[0063] The construction completion time is specified as t EOJ , and estimate the fracturing fluid efficiency e at this time EOJ (Refer to e SO The time t for the initially pumped low sand ratio sand-carrying fluid to reach the end of the fracture MS , which is the time t when construction is completed EOJ .

[0064] t MS =[(1-e EOJ ) 2 +S F ] (8)

[0065] t MS With t LS The difference is the total time t required to pump the low sand ratio sand-carrying fluid, that is:

[0066] t=t MS -t LS (9)

[0067] This moment is the starting point for the high sand ratio sand-carrying fluid to be pumped into the fracture, and then the total sand volume M required for the high sand ratio sand-carrying fluid to be pumped is calculated.

[0068]

[0069] Where: Q - pump displacement, m 3 / min;

[0070] C dmax ——Maximum sand-carrying fluid concentration, kg / m 3 ;

[0071] α——fracturing fluid efficiency;

[0072] e EOJ ——Fracturing fluid efficiency at the end of operation, decimal;

[0073] F d ——Sand-carrying fluid shape coefficient, 0.03 <F d <0.05.

[0074] Calculate flow capacity:

[0075]

[0076] Based on a comprehensive consideration of geological conditions and the performance of construction equipment, an end-sanding and gravel filling process adapted to reservoir characteristics was designed by optimizing fracturing parameters (including displacement, sand ratio, and closure pressure). Slickwater is used as the fracturing fluid. Taking advantage of its low viscosity and efficient sand-carrying capacity, the fracturing fluid is injected into the wellbore via a high-pressure pump group, gradually increasing the bottomhole pressure to the critical value for formation failure, opening natural fractures and forming a main fracture network. The pre-fluid forms a sand plugging barrier at the front of the fracture through filtration, precisely controlling the longitudinal extension of the fracture. Subsequently, low-sand ratio (5% to 10%) and high-sand ratio (20% to 30%) sand-carrying fluids are injected in stages to sequentially construct fracture diversion channels and force the fractures to expand laterally, forming narrow and wide propped fractures.

[0077] After the PdO@rGO ceramsite proppant injection process is completed, rock cuttings samples from the fracture filling section are obtained using a downhole sidewall coring device or directional drilling cuttings collection device. Fluorescence labeling quantitative analysis technology is used to verify the uniformity of the proppant distribution. After fracturing, sampling points are selected at intervals of 10 to 20 meters along the fracture extension direction. A high-temperature and high-pressure adaptive coring tool is used to obtain core columns containing proppant. Utilizing the wavelength specificity of the fluorescent nanoparticle excitation and the distinguishability of the formation background signal, laser ablation-inductively coupled plasma mass spectrometry is used to quantitatively measure the spatial distribution of the Pd element. The coverage rate per unit area of ​​the fracture surface and the distribution coefficient of variation are calculated.

[0078] Coverage rate per unit area (C area )

[0079]

[0080] Where: A covered,i ——The fluorescence intensity at the i-th sampling point exceeds the threshold (I threshold =I0+3σ background )’s pixel area;

[0081] A total ——Total imaging area of ​​the crack surface;

[0082] Coefficient of variation (CV) of distribution:

[0083]

[0084] Where: μ concentration —Average concentration of PdO@rGO at each sampling point on the fracture surface (calculated by inversion of the calibration curve);

[0085] σ concentration ——Standard deviation of concentration distribution.

[0086] PdO@rGO ceramsite proppant enters the fracture system along with the sand-carrying fluid. Its porous structure and surface functional coating efficiently capture microorganisms through electrostatic adsorption. 2 + Through transmembrane permeation, the proppant specifically binds to the sulfhydryl groups of bacterial intracellular enzymes (such as hydrogenase and ATP synthase), inhibiting energy metabolism and inducing a burst of reactive oxygen species, completely destroying microbial activity. During the fracture closure phase, the proppant embeds itself into the fracture wall, forming a stable permeable layer. Combined with the slow-release metal ions, it continuously inhibits the growth of sulfate-reducing bacteria and methanogens, thereby controlling hydrogen loss.

[0087] Subsequently, the underground hydrogen storage reservoir needs to be tested for bacterial content. Samples are taken for laboratory testing. Taking advantage of the ability of bacteria to grow and multiply under suitable culture conditions, conditions are created that are suitable for the growth of methanogens, acetic acid bacteria, sulfate-reducing bacteria, and hydrogen-oxidizing bacteria. Cultures are carried out under appropriate temperature and humidity conditions. The number of bacteria is calculated using the colony count method. The presence and content of bacteria in the sample are determined by the growth of bacteria on the culture medium.

[0088] Wherein, preparation of methanogen culture medium:

[0089] 1. Culture medium composition

[0090] Glucose or methanol: As the main carbon source for methanogens, select the appropriate carbon source and determine its dosage based on the type and specific needs of the methanogens.

[0091] Inorganic ammonium salts (such as NH4Cl): Provide the necessary nitrogen source to support the growth and metabolism of methanogens. The dosage should be determined according to the specific formula.

[0092] Trace element solution: Contains trace elements such as nickel, cobalt, and molybdenum required for the growth of methanogens. The dosage generally ranges from a few milliliters to tens of milliliters, and is added according to the specific formula requirements.

[0093] Agar (for solid culture media): Acts as a coagulant, solidifying the culture medium into a solid form for easier manipulation and observation. The typical dosage is 15g to 20g.

[0094] Distilled water: As a solvent, dissolve all the above ingredients. Generally, 1000ml of distilled water is used or it can be determined according to the recipe requirements.

[0095] Oxygen-free gas (such as N2 or CO2 / N2 mixed gas): used to drive out air during the preparation and inoculation process to maintain an anaerobic environment for the culture medium.

[0096] 2. Preparation steps

[0097] Weigh ingredients: Accurately weigh glucose (or methanol), inorganic ammonium salt, trace element solution, yeast extract (or peptone, if included in the recipe), agar and other ingredients according to the recipe.

[0098] Dissolving and mixing: Place the weighed ingredients into a beaker, add appropriate amount of distilled water, heat and stir until completely dissolved, taking care to avoid introducing air.

[0099] Adjust pH (if necessary): According to the recipe requirements, use an appropriate amount of acid or base solution (such as NaOH or HCl) to adjust the pH of the culture medium to the appropriate range.

[0100] Anaerobic treatment: Pour the dissolved culture medium into a conical flask and use oxygen-free gas (such as N2 or CO2 / N2 mixed gas) to drive out the air to ensure that the culture medium is in an anaerobic state.

[0101] Sterilization: The anaerobic culture medium is sterilized with high-pressure steam to kill any bacteria. Sterilization conditions are usually 121°C for 30 minutes.

[0102] Cooling and solidification (for solid culture medium): Cool the sterilized culture medium to a suitable temperature (usually 50-60°C), then quickly pour it into a sterile culture dish and wait for it to solidify naturally. Maintain an anaerobic environment.

[0103] Inoculation and culture: Under sterile, anaerobic conditions, methanogens are inoculated onto the prepared culture medium and then cultured at an appropriate temperature (depending on the type of methanogen and specific requirements). This culture is typically performed in an anaerobic environment, such as an anaerobic incubator or sealed culture flask.

[0104] Among them, the preparation of iron bacterial culture medium:

[0105] 1. Culture medium composition:

[0106] Ferrous sulfate (FeSO4·7H2O): As the main energy source for iron bacteria, it provides them with ferrous ions for oxidative metabolism. The general dosage is 0.5g-1g.

[0107] Magnesium sulfate (MgSO4·7H2O): provides magnesium ions, participates in various enzymatic reactions in cells, and promotes the growth of iron bacteria. The dosage is about 0.5g.

[0108] Potassium hydrogen phosphate (K2HPO4): used to maintain the acid-base balance of the culture medium and provide phosphorus for bacteria. The usual dosage is 0.5g.

[0109] Ammonium nitrate (NH4NO3): As a nitrogen source, it provides iron bacteria with the nitrogen elements needed to synthesize nitrogen-containing substances such as proteins. The dosage is about 1g.

[0110] Calcium chloride (CaCl2): provides calcium ions, which helps maintain the stability of cell structure. The dosage is approximately 0.2g.

[0111] Agar (if preparing solid culture medium): solidifies the culture medium to facilitate observation and separation of iron bacteria. The usual dosage is 15g-20g.

[0112] Distilled water: As a solvent, dissolve all the above ingredients, generally use 1000ml.

[0113] 2. Preparation steps:

[0114] Weighing: Accurately weigh ferrous sulfate, magnesium sulfate, dipotassium hydrogen phosphate, ammonium nitrate, calcium chloride (if agar is used), and other ingredients according to the formula.

[0115] Dissolution: Add each weighed ingredient sequentially to a beaker filled with an appropriate amount of distilled water, stirring. Since ferrous sulfate is easily oxidized, add a small amount of dilute sulfuric acid after dissolution to prevent oxidation. Heat and continue stirring until all ingredients are completely dissolved.

[0116] pH adjustment: Use pH paper or a pH meter to measure the pH of the culture medium. Usually, the pH value suitable for the growth of iron bacteria is between 6.0 and 7.0, which can be adjusted to the appropriate range with dilute hydrochloric acid or sodium hydroxide solution.

[0117] Make up the volume: Transfer the dissolved and pH-adjusted culture medium to a 1000ml volumetric flask and make up to the mark with distilled water.

[0118] Aliquot (if necessary): Aliquot the culture medium into different containers, such as test tubes, conical flasks, etc., according to experimental requirements.

[0119] Sterilization: Plug the container containing the culture medium with cotton and sterilize it by high pressure steam at 121°C for 20-30 minutes.

[0120] Cooling and solidification (for solid culture medium): If a solid culture medium is being prepared, cool it to about 50℃-60℃ after sterilization. At this time, the culture medium is in liquid state. Pour it into a sterile culture dish and wait for it to cool and solidify naturally.

[0121] Inoculation and Culture: Under a sterile environment, use an inoculating loop or other tool to inoculate the iron bacteria onto the prepared culture medium. The culture medium is then placed in a constant temperature incubator at an appropriate temperature (usually 25-30°C) for incubation. During the incubation process, the growth of the iron bacteria can be observed, such as the formation of characteristic rust-colored precipitates.

[0122] Wherein, preparation of sulfate-reducing bacteria culture medium:

[0123] 1. Culture medium composition:

[0124] C3H5NaO3 or C3H3NaO3: As the main carbon source for sulfate-reducing bacteria, the dosage usually depends on the specific formula and is generally between 10g and 30g.

[0125] (NH4)2SO4 or MgSO4: Provides the necessary sulfur source and also serves as an inorganic salt component in the culture medium, promoting the growth and metabolism of sulfate-reducing bacteria. Typical dosages range from a few grams to over ten grams.

[0126] Yeast extract or peptone: Provides a nitrogen source and growth factors to support the growth of sulfate-reducing bacteria. The typical dosage is 5g to 10g.

[0127] KCl or NaCl: As an inorganic salt component, it adjusts the osmotic pressure and pH value of the culture medium. The usual dosage is several grams.

[0128] Agar (for solid culture media): Acts as a coagulant, solidifying the culture medium into a solid form for easier manipulation and observation. The typical dosage is 15g to 20g.

[0129] Distilled water: As a solvent, dissolve all the above ingredients. Generally, 1000ml of distilled water is used.

[0130] Some sulfate-reducing bacteria culture medium formulas may also contain other ingredients, such as vitamins, trace elements, etc., depending on the bacterial species and experimental requirements.

[0131] 2. Preparation steps:

[0132] Weigh ingredients: Accurately weigh C3H5NaO3 (or C3H3NaO3), (NH4)2SO4 (or MgSO4), yeast extract (or peptone), KCl (or sodium chloride), agar and other ingredients according to the recipe.

[0133] Dissolving and mixing: Place the weighed ingredients into a beaker, add appropriate amount of distilled water, heat and stir until completely dissolved. Be careful to avoid excessive foaming.

[0134] Adjust the pH value: According to the formula requirements, use an appropriate amount of acid or alkali solution (such as NaOH or HCl) to adjust the pH value of the culture medium to the appropriate range. Sulfate-reducing bacteria usually grow better in a neutral or slightly alkaline environment.

[0135] Anaerobic treatment (optional): Because sulfate-reducing bacteria are anaerobic or facultative anaerobes, some formulations may require preparation under anaerobic conditions. This can be achieved by bubbling an oxygen-free gas (such as N2 or a CO2 / N2 mixture) into the culture medium, or by using equipment such as an anaerobic incubator for anaerobic treatment.

[0136] Sterilization: Pour the dissolved and pH-adjusted culture medium into a conical flask, plug the flask with a cotton plug, and then sterilize it with high-pressure steam. Sterilization conditions are usually 121°C for 30 minutes to ensure the sterility of the culture medium.

[0137] Cooling and solidification (for solid culture medium): Cool the sterilized culture medium to an appropriate temperature (usually 50-60°C), then quickly pour it into a sterile culture dish and allow it to solidify naturally. Be careful to avoid contamination during the cooling process.

[0138] Inoculation and Culture: Under sterile and anaerobic conditions (if anaerobic treatment is used), inoculate sulfate-reducing bacteria onto the prepared culture medium and then culture at an appropriate temperature (depending on the strain and experimental requirements). Culture is usually performed in an anaerobic or low-oxygen environment, such as an anaerobic incubator or sealed culture flask.

[0139] Wherein, preparation of acetic acid bacteria culture medium:

[0140] 1. Culture medium composition:

[0141] Glucose: As the main carbon source for acetic acid bacteria, the dosage usually ranges from 10g to 30g. The specific dosage can be adjusted according to actual needs.

[0142] Yeast extract or yeast paste: Provides the necessary nitrogen source and growth factors to promote the growth of acetic acid bacteria. The general dosage is 5g to 10g.

[0143] Calcium carbonate: As a buffer, it neutralizes the acid produced during the culture process and maintains a stable pH in the culture medium. The usual dosage is 10g to 20g.

[0144] Agar: Serves as a coagulant to solidify the culture medium into a solid form for easier manipulation and observation. The typical dosage is 15g to 20g.

[0145] Distilled water: As a solvent, dissolve all the above ingredients. Generally, 1000ml of distilled water is used.

[0146] Absolute alcohol (optional): Some acetic acid bacteria culture medium formulas contain anhydrous alcohol, which can be added after the culture medium is sterilized and cooled to a suitable temperature. The dosage is generally 20 ml.

[0147] 2. Preparation steps:

[0148] Weigh ingredients: Accurately weigh glucose, yeast extract (or yeast paste), calcium carbonate, agar and other ingredients according to the recipe.

[0149] Dissolving and mixing: Place the weighed ingredients into a beaker, add appropriate amount of distilled water, heat and stir until completely dissolved.

[0150] Adjusting pH: If the recipe requires pH adjustment, use an appropriate amount of acid or base solution (such as NaOH or HCl). However, some acetic acid culture medium recipes may not require pH adjustment.

[0151] Sterilization: Pour the dissolved culture medium into a conical flask, plug the flask with a cotton plug, and then sterilize it with high-pressure steam. Sterilization conditions are usually 121°C for 30 minutes.

[0152] Cooling and solidification (for solid culture media): Cool the sterilized culture media to an appropriate temperature (usually 50-60°C). If anhydrous alcohol is included in the formulation, add it at this temperature and mix thoroughly. Then, pour the culture media into a sterile culture dish and allow it to solidify naturally.

[0153] Inoculation and culture: Under sterile conditions, inoculate acetic acid bacteria onto the prepared culture medium and then culture it at an appropriate temperature (usually 30-32°C).

[0154] Wherein, the preparation of hydrogen oxidizing bacteria culture medium:

[0155] 1. Culture medium composition:

[0156] NaHCO3 or Na2CO3: As the main carbon source for hydrogen oxidizing bacteria and the substance that provides alkalinity, its dosage depends on the specific formula. (Usually between 5g and 20g)

[0157] NH4Cl or NH4NO3: Provides the necessary nitrogen source to support the growth of hydrogen-oxidizing bacteria. (Usually used dosage is 1g to 5g)

[0158] KH2PO4 or K2HPO4: As an inorganic salt component, it provides phosphorus and helps regulate the pH and osmotic pressure of the culture medium. (Used dosage is 0.5g to 2g)

[0159] Yeast extract or peptone: Provides additional nitrogen source, growth factors and vitamins to promote the growth of hydrogen oxidizing bacteria. (Usually used dosage is 2g to 5g)

[0160] Agar (for solid culture medium): acts as a coagulant to solidify the culture medium into a solid form for easy operation and observation. (Usage: 15g to 20g)

[0161] Distilled water: 1000ml distilled water.

[0162] (Note: Some hydrogen oxidizing bacteria culture medium formulas may also contain other ingredients, such as trace elements, vitamins, etc., depending on the bacterial species and experimental requirements)

[0163] 2. Preparation steps:

[0164] Weigh ingredients: Accurately weigh NaHCO3 (or Na2CO3), NH4Cl (or NH4NO3), KH2PO4 (or K2HPO4), yeast extract (or peptone), agar and other ingredients according to the recipe.

[0165] Dissolving and mixing: Place the weighed ingredients into a beaker, add an appropriate amount of distilled water, heat and stir until completely dissolved. (Note: Avoid excessive foaming and ensure that all ingredients are evenly mixed)

[0166] Adjust pH: Depending on the recipe, use an appropriate amount of an acid or base solution (such as NaOH or HCl) to adjust the pH of the culture medium to the appropriate range. Hydrogen-oxidizing bacteria generally grow best in neutral or slightly alkaline environments, so the pH may need to be adjusted to between 7.0 and 8.5.

[0167] Sterilization: Pour the dissolved and pH-adjusted culture medium into a conical flask, plug the flask with a cotton plug, and then sterilize it with high-pressure steam. Sterilization conditions are usually 121°C for 30 minutes to ensure the sterility of the culture medium.

[0168] Cooling and solidification (for solid culture medium): Cool the sterilized culture medium to a suitable temperature (usually 50-60°C), then quickly pour it into a sterile culture dish and wait for it to solidify naturally. (Note: Avoid contamination during the cooling process)

[0169] Inoculation and Culture: Under sterile conditions, inoculate the hydrogen oxidizing bacteria onto the prepared culture medium and then culture at an appropriate temperature (depending on the strain and experimental requirements, usually between 25°C and 37°C). Hydrogen oxidizing bacteria generally require a certain amount of oxygen or facultative anaerobic conditions for growth, so the appropriate culture environment should be selected based on the needs of the specific strain.

Claims

1. A method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO, characterized in that: The following steps are involved: S1: Preparation of pre-oxidized expanded graphite; S2: Preparation of PdO@rGO composites; S3: Preparation of porous ceramsite proppant; S4: injecting the prepared proppant into the formation through the end screenout technique; S5: Fluorescent labeling for proppant distribution uniformity assessment; S6: Preparation of culture medium to detect bacterial content in the formation.

2. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The oxidation reaction vessel in step S1 includes a round-bottom flask, a three-necked flask, a conical flask or a reactor, and the reaction temperature is controlled at 15° C. to 80° C.

3. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The metal cation in the metal nitrate in step S2 is selected from at least one of the following: lead ion (Pd 2 +), mercury ions (Hg2+), silver ions (Ag+), copper ions (Cu2+), and zinc ions (Zn2+).

4. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The calcination equipment in step S2 is a vacuum furnace, a tubular furnace or a muffle furnace equipped with a vacuum pump, the calcination temperature is 400° C. to 600° C., and the calcination time is 2 to 5 hours.

5. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The mixing equipment in step S3 is a brute force mixer, a ball mill, a twin-screw mixer or a planetary ball mill, the mixing time is 0.5 to 3 hours, and the mixing speed is 200 to 800 rpm.

6. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The sintering equipment in step S3 is a high-temperature sintering furnace, a resistance furnace or a microwave sintering furnace, the sintering temperature is 1200° C. to 1300° C., and the heating rate is 3° C. / min to 10° C. / min.

7. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The porosity of the ceramsite proppant in step S3 is 35% to 65%, the particle size range is 0.1 mm to 0.5 mm, and the compressive strength is ≥15 MPa.

8. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: In step S3, the mass ratio of lead oxide in the PdO@rGO composite material is 0.1% to 5%, and the mass ratio of rGO to ceramsite carrier is 1:50 to 1:

10.

9. The method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to claim 1, characterized in that: The proppant injection method in step S4 includes hydraulic fracturing, gas driving or mechanical pushing, and the sand particles at the ends of the cracks are replaced first.

10. A method for controlling hydrogen storage loss in depleted gas reservoirs based on the special material PdO@rGO according to any one of claims 1 to 9, characterized in that: By inhibiting the metabolic activity of sulfate-reducing bacteria and methanogens, the hydrogen loss rate is reduced.

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