Construction and operation method of aquifer gas storage

Abstract

The invention discloses a construction and operation method of an aquifer gas storage, which comprises the following steps of: S1, performing an in-situ burning explosion fracturing strategy on a selected aquifer to form a storage space containing a fracture network and a cavity in the selected aquifer; s2, controlling the reaction conditions of the in-situ burning explosion fracturing strategy, so that after the reaction is finished, the non-combustible gas is reserved in the storage space to serve as bottom gas of the gas storage; s3, periodical natural gas injection and production operation is conducted on the storage space; therefore, the reservoir space is actively created at a time through in-situ fire blast fracturing, the reaction is regulated and controlled to generate the self-generated cushion gas, and the problems that the period is long due to the fact that traditional aquifer reservoir building depends on slow gas injection water driving, and the initial investment cost is high due to outsourcing and injection of a large amount of cushion gas are solved.

Description

Technical Field

[0001] This invention relates to the field of underground energy storage technology, and in particular to a method for constructing and operating an aquifer gas storage facility. Background Technology

[0002] Underground gas storage facilities are indispensable peak-shaving and supply-guaranteeing facilities in natural gas transmission and distribution systems. They mainly include four types: gas reservoir type, salt cavern type, aquifer type, and mine pit type. Among them, aquifer type underground gas storage facilities are artificial gas reservoirs formed by injecting natural gas under high pressure into underground aquifers with good sealing conditions, thereby displacing pore water through gas injection.

[0003] However, the construction of traditional aquifer gas storage facilities is typically time-consuming and involves huge investments. It involves continuously injecting natural gas into a natural aquifer, gradually forming a gas cap of a certain size through long-term displacement. This process not only takes several years or even longer to reach the designed storage capacity, but also requires the injection of large amounts of expensive natural gas as "buffer gas" to maintain reservoir pressure and prevent water intrusion. This buffer gas cannot be extracted throughout the entire lifespan of the storage facility, constituting a huge sunk cost. Furthermore, the permeability of natural aquifers is usually limited, resulting in low injection and extraction rates, making it difficult to meet the rapid peak-shaving demands during peak periods.

[0004] Against this backdrop, there is an urgent need to develop an innovative method for constructing and operating aquifer gas storage facilities, aiming to overcome the shortcomings of traditional construction methods, such as long construction cycles, high costs, and low efficiency. Summary of the Invention

[0005] The technical problem solved by this invention is to address the shortcomings of traditional methods that rely on a slow gas injection and water displacement process, which cannot quickly respond to emergency peak-shaving capabilities and require the purchase of large quantities of natural gas for injection and permanent underground storage, resulting in huge capital expenditures that cannot be recovered.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for constructing and operating an aquifer gas storage facility includes the following steps:

[0008] S1. In-situ explosive fracturing of the selected aquifer to form a reservoir space containing a fracture network and cavities in the selected aquifer;

[0009] S2. Control the reaction conditions of the in-situ combustion and explosion fracturing so that after the reaction is completed, non-flammable gas is left in the storage space as the bottom gas of the gas storage tank.

[0010] S3. Perform periodic natural gas injection and extraction operations on the storage space.

[0011] Preferably, in step S1, the in-situ combustion and explosion fracturing includes the following steps:

[0012] The mixture of fuel gas and combustion-supporting gas is injected into the target section of the aquifer, and then detonated through an ignition electrode.

[0013] Preferably, in step S2, controlling the reaction conditions for the in-situ combustion-explosion fracturing includes the following steps:

[0014] By controlling the mixing ratio of the fuel gas and the combustion-supporting gas, the gas remaining in the storage space after the combustion and explosion reaction contains carbon dioxide.

[0015] Preferably, the fuel gas is methane, the combustion-supporting gas is oxygen, and the volume ratio of methane to oxygen is in a fuel-rich state.

[0016] Preferably, after step S1 and before step S3, a well-sealing step is also included:

[0017] After the combustion reaction ends, the wellhead is closed, and the wellbore and storage space system are kept closed under the downhole ambient temperature and pressure for a preset time.

[0018] Preferably, the duration of the well-steaming step is determined based on the temperature and pressure recovery curve of the aquifer.

[0019] Preferably, step S3 further includes the following step:

[0020] During the gas injection phase of the first injection-production cycle, the peak applied gas injection pressure is close to but does not exceed the fracture pressure of the reservoir space formed by the in-situ combustion and fracturing described in step S1.

[0021] Preferably, during or after the execution of step S3, step S4 is further included:

[0022] Based on the monitoring results of the reservoir space morphology and gas migration, one or more additional in-situ combustion and detonation fracturing operations are carried out at new locations within the aquifer.

[0023] Preferably, the additional in-situ combustion and fracturing is carried out in a sequential manner at the planned boundary of the gas storage facility or within the storage area.

[0024] Preferably, the monitoring includes at least one of microseismic monitoring, tracer monitoring, or wellbore pressure monitoring.

[0025] The beneficial effects of this invention are:

[0026] First, the method for constructing and operating aquifer gas storage facilities provided by this invention actively creates storage space in a single operation through in-situ combustion-explosion fracturing and regulates the reaction to generate self-generated cushion gas. This solves the problems of long construction cycles due to slow gas injection for water displacement in traditional aquifer storage projects, and high initial investment costs caused by purchasing and injecting large amounts of cushion gas. Specifically, this invention uses high-energy gas fracturing as the core construction process to forcefully form a composite storage space of "cavity-fracture network" in a very short time. Furthermore, by controlling the fuel-rich ratio of fuel and combustion-supporting gas, the high-temperature, high-pressure products (mainly carbon dioxide) after combustion directly constitute the cushion gas. Consequently, this invention shortens the construction cycle (from several years to several months) and eliminates the sunk costs of traditional cushion gas procurement and injection, thus improving the economic feasibility of aquifer gas storage facilities.

[0027] Secondly, the construction and operation method of aquifer gas storage provided by this invention solves the problems of low injection and production rates due to poor permeability of natural aquifers and potential performance degradation of gas storage facilities during long-term cyclic operation by periodically injecting and producing natural gas in the storage space after combustion-explosion modification, and by using injection pressure to support and expand the fracture network. This invention thus gives conventional injection and production operation a "dynamic enhancement": the high pressure during the injection period acts as periodic hydraulic support, effectively inhibiting fracture closure and potentially promoting its gentle expansion; during the production period, the existing high-conductivity fracture network is fully utilized to achieve high-speed extraction. Therefore, this invention significantly improves the working gas injection and production rates of the gas storage facility, enhances peak-shaving response capabilities, and achieves long-term stable operation with consolidated and even optimized gas storage performance. Attached Figure Description

[0028] Figure 1 A schematic diagram of the overall process for constructing and operating a gas storage facility in an aquifer provided by the present invention;

[0029] Figure 2 This is a schematic diagram of the storage space morphology of a traditional aquifer gas storage facility provided by the present invention;

[0030] Figure 3 This is a schematic diagram of the storage space morphology of an aquifer gas storage facility in the construction and operation method of an aquifer gas storage facility provided by the present invention;

[0031] Figure 4 This is a schematic diagram illustrating the principle of forming self-generated cushion gas and fracture network through combustion-explosion fracturing in a method for constructing and operating an aquifer gas storage facility provided by the present invention.

[0032] Figure 5 This is a schematic diagram illustrating the dynamic strengthening effect of injection-production cycle on fracture network in a method for constructing and operating an aquifer gas storage facility provided by the present invention.

[0033] In the diagram: 1. Surface injection system; 2. Coiled tubing; 3. Wellbore; 4. Caprock; 5. Aquifer; 6. Cavity; 7. Fracture network; 8. Ignition electrode; 9. Fracturing tool; 10. Cushion gas. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] The core of this invention lies in transforming in-situ combustion and explosion fracturing technology from a production enhancement measure into a systematic method for constructing and operating high-performance aquifer gas storage facilities through a series of continuous and coordinated steps.

[0036] Reference Figure 1 This invention will describe in detail the specific implementation method, implementation principle, key control points and their role in the whole technical solution for each step in the order of steps.

[0037] S100: Site Selection and Assessment

[0038] The purpose of this step is to select suitable geological target areas for engineering modification and construction of gas storage facilities, and to establish accurate underground models to guide subsequent operations.

[0039] S110: Target Area Optimization:

[0040] The primary objective is to locate areas with relatively suitable geological conditions to reduce engineering risks and increase the success rate. Aquifer 5 needs to meet several basic geological conditions:

[0041] Caprock conditions: A continuous, stable rock layer of a certain thickness and low permeability, such as dense mudstone, gypsum, or salt rock, must exist above the target aquifer 5. This caprock 4 can prevent subsequently injected natural gas from escaping upwards. Specifically, the sealing capacity of caprock 4 needs to be evaluated through methods such as seismic data interpretation and analysis of adjacent well logging data.

[0042] Boundary conditions: An ideal aquifer 5 should possess certain structural trap morphologies, such as anticlines, nose-like structures, or lateral sealing conditions such as faults or lithological pinch-outs. These boundary conditions help confine natural gas within a specific spatial range, preventing its large-scale lateral migration and thus forming an effective gas reservoir. In gently sloping formations, aquifer 5 also requires assessment of hydrodynamic conditions to ensure stable gas accumulation after injection.

[0043] Reservoir conditions: The target aquifer 5 should have a certain thickness and distribution range, and its lithology can be sandstone, fractured limestone, etc. Although this invention can significantly improve its conductivity through combustion and explosion, if the original physical properties are too poor (such as extremely dense), the difficulty and cost of its modification will also increase dramatically.

[0044] Specifically, in practice, staff need to comprehensively utilize regional geological maps, seismic exploration data (including 2D and 3D seismic exploration data), and logging and well logging data from existing boreholes (hydrological wells and oil and gas exploration wells). Through the analysis of these data, several potential target areas can be preliminarily delineated.

[0045] S120: Geological Modeling

[0046] After selecting the initial target area, more detailed geological and geophysical exploration is required to construct a refined three-dimensional geological model suitable for engineering design. This includes:

[0047] Data Acquisition and Processing: High-precision 3D seismic exploration is deployed within the target area to obtain high-quality subsurface reflection data. Simultaneously, one or more appraisal wells need to be drilled for a full suite of logging operations (such as acoustic, density, resistivity, and nuclear magnetic resonance) and core sampling. Core samples need to be tested in the laboratory for rock mechanical parameters (elastic modulus, Poisson's ratio, compressive strength), porosity, permeability, etc.

[0048] Model Construction: Utilizing professional geological modeling software (such as Petrel, RMS, etc.), multi-source information, including seismic interpretation of stratigraphy and faults, well logging data, and core analysis data, is integrated. The constructed model should include: structural maps of the top and bottom surfaces of the caprock (4 layers), structural maps of the top and bottom surfaces of the target aquifer (5 layers), fault distribution, thickness map of the target layer, porosity and permeability attribute models, formation pressure and temperature field models, and models of the direction and magnitude of the geostress field.

[0049] Target Determination: Based on a three-dimensional geological model, personnel can determine the target segment (specific depth range) and initial gas injection point (precise location within wellbore 3) for the first in-situ explosive fracturing. When selecting the target segment, factors such as rock brittleness (ease of fracturing), burial depth (affecting construction pressure), and distance from the caprock 4 (ensuring a safe interval) need to be comprehensively considered. The initial gas injection point is usually selected at a location where the best stimulation effect is expected, such as a relatively thick section of the reservoir.

[0050] In summary, this invention, through target area optimization and geological modeling, establishes a reliable geological foundation, greatly reducing the risk of engineering failure due to unclear geological conditions, and thus providing a quantitative basis for subsequent combustion and explosion design, construction, and monitoring.

[0051] S200: Inject methane and combustion-supporting gas into the target layer.

[0052] The purpose of this step is to actively and rapidly create a high-conductivity space in the target aquifer 5 that meets the requirements for gas storage by using high-energy chemical reactions.

[0053] S210: Construction Preparation

[0054] In the target wellbore 3, a dedicated explosive fracturing tool string 9 (typically including a packer, ignition electrode 8, gas injection channel, etc.) is lowered into the target formation defined in step S100. The tool string is delivered via coiled tubing 22 or drill pipe. Ensure the packer is set to isolate the target formation from the rest of the wellbore 3.

[0055] S220: Gas Mixing and Injection

[0056] The pre-mixed gas is injected into the isolated target layer through the ground injection system 1.

[0057] Fuel gas: Methane is preferred because it is the main component of natural gas, is widely available, and its combustion products are relatively simple. Other combustible gases such as propane can also be used.

[0058] Combustion-supporting gas: Oxygen is preferred. Pure oxygen allows for a more complete reaction and a more concentrated energy.

[0059] Control of Mixing Ratio: To achieve "self-generated cushion gas 10," this invention emphasizes controlling the volume ratio of methane to oxygen in a fuel-rich state. A fuel-rich state means that the injected methane is stoichiometrically excess relative to the oxygen, with a fuel gas to combustion-supporting gas volume ratio of 1 / 3 to 1 / 2. For example, the stoichiometric reaction for complete methane combustion is: methane + 2 oxygen → carbon dioxide + 2 H₂O. If the injected methane to oxygen volume ratio is greater than 1:2, it is considered a fuel-rich state. In practical engineering design, this ratio is a parameter that requires fine-tuning, depending on the specific requirements for the final chamber pressure, temperature, and cushion gas 10 composition (carbon dioxide content volume ratio of 20%-30%). In this embodiment, a typical fuel-rich ratio range is between 15% and 80% methane:oxygen (the reason for setting the ratio within this range is to ensure sufficient combustion pressure can be generated at the bottom of the well). The amount of gas injected is determined based on the preset fracture propagation range.

[0060] S230: Triggered a fire and explosion

[0061] After the gas is injected into the target formation, the downhole ignition device (such as ignition electrode 8) is activated via ground command. Ignition then triggers rapid combustion of the gas mixture. Due to the confined space, combustion quickly transforms into deflagration or explosion. This process is completed within milliseconds to seconds, allowing the invention to release enormous energy. At this point, the gas remaining in the storage space after the combustion-explosion reaction contains approximately 20% to 30% carbon dioxide by volume.

[0062] S240: Gas storage space formation

[0063] The high-temperature (up to thousands of degrees Celsius) and high-pressure (far exceeding formation fracturing pressure) gases generated during the combustion and explosion exert enormous impact loads and quasi-static pressures on the surrounding rock strata. This pressure first overcomes the tensile and shear strength of the rock, causing it to generate radial, multidirectional tensile and shear fractures, forming a complex fracture network 7. At the same time, the rock adjacent to the wellbore 3 may be crushed, compacted, or partially melted, forming a relatively large central cavity (or expansion cavity 6).

[0064] Ultimately, a composite reservoir space was formed, centered on wellbore 3 and consisting of a "main cavity 6" and a radiating "multi-level fracture network 7" (e.g., Figure 2 and Figure 3 (As shown). The total volume of this space (including the volume of fracture pores and the volume of cavity) is much larger than the pore volume of the original strata, and thus its equivalent permeability is increased due to the presence of fractures.

[0065] In summary, this invention abandons the traditional passive gas storage construction mode that relies on natural pores, and enables the rapid and large-scale construction of gas storage spaces through the above-mentioned technical solution. Moreover, the resulting "cavity 6 + fracture network 7" structure has both a large storage volume and extremely high fluid conductivity, providing a foundation for the further generation of "self-generated cushion gas 10".

[0066] S300: Mist-like Well

[0067] After the explosion, the underground cavity 6 is filled with high-temperature and high-pressure reaction products. Therefore, the purpose of this step is to allow the system to evolve naturally through the process of "steaming the well" and eventually stabilize into a "cushion gas 10 gas cap" mainly composed of non-combustible gas.

[0068] S310: Rapid well shut-off and well smothering

[0069] After the combustion reaction is completed, all valves at the wellhead are immediately (usually within a few minutes) closed, making the entire wellbore 3 and the storage space connected to the wellbore 3 a completely closed high-temperature and high-pressure system, i.e., "steaming the well".

[0070] S320: Physicochemical changes during well shut-in process

[0071] During the well shut-in period, the system undergoes a series of spontaneous changes under the influence of the downhole environment (surrounding rock):

[0072] Heat exchange and temperature equilibrium: The extremely high-temperature gas (mainly composed of carbon dioxide, H2O vapor, unreacted methane, etc.) inside cavity 6 begins to transfer heat to the surrounding rocks. As the rocks are heated, the gas temperature gradually decreases.

[0073] Water vapor condensation: As the gas temperature drops below the dew point at that pressure, water vapor in the gas begins to condense into liquid water. This water either flows along the crack walls or remains at the bottom of the crack. The latent heat released during condensation also slows down the system's cooling rate.

[0074] Carbon dioxide dissolution and weak acid corrosion: Carbon dioxide gas partially dissolves in formation water to form carbonic acid. This weakly acidic fluid has a slight dissolving effect on carbonate minerals (such as calcite) or certain silicate minerals on the fracture walls, which can slightly increase the fracture opening or clear some blockages at the microscopic level, thereby providing additional enhancement to the conductivity.

[0075] Pressure and volume rebalancing: Due to the decrease in temperature, condensation of water vapor, and partial dissolution of gases, the overall pressure of the system will gradually decrease from the peak value after combustion and eventually tend to a stable "thermal equilibrium-chemical equilibrium" pressure. This pressure is usually still much higher than the original formation pressure.

[0076] S330: Formation of self-generated cushion air 10

[0077] By pre-controlling the gas ratio to a "fuel-rich state" in step S200, it was ensured that the post-combustion products contained a large amount of unreacted methane and a large amount of carbon dioxide produced by complete combustion. After the system stabilized following well shut-in, the gas remaining in chamber 6 was mainly carbon dioxide, mixed with some residual methane and a small amount of other inert gases. These gases were generated in situ during the storage construction process, rather than injected from the outside. Carbon dioxide is a non-flammable gas with relatively stable chemical properties and can be used as a cushion gas. This high-pressure gas occupies the upper part (or the entire space) of the storage space, forming the initial gas crown of the gas storage facility, namely "self-generated cushion gas 10". Its pressure provides the base pressure for subsequent natural gas injection and further ensures that the storage space is not reinjected by formation water.

[0078] Since the well shut-in time is a parameter that needs to be optimized, if the time is too short, the system will not be stable, and the gas composition and pressure will fluctuate greatly; if the time is too long, it will affect the reservoir construction progress. Therefore, it is necessary to keep the wellbore 3 and the storage space system in a closed state under the downhole ambient temperature and pressure for a preset time.

[0079] Typically, the preset time for well shut-in needs to be determined based on the temperature and pressure recovery curves monitored by downhole thermometers and pressure gauges. That is, well shut-in is complete when the temperature of aquifer 5 is between 60-80℃ and the pressure recovers to the pore pressure level of aquifer 5.

[0080] In summary, this invention achieves "zero-cost" in-situ manufacturing of cushion gas 10 resources, solving the problem of high costs associated with purchasing and injecting cushion gas 10 in traditional methods. Simultaneously, the thermal and chemical processes during the well-closing process further optimize the reservoir space and improve the flowability, enabling the entire system to smoothly transition to a stable state suitable for injection and production operations.

[0081] S400: Dynamic Enhancement of Injection-Production Cycle

[0082] Once a stable storage space with self-generated cushion gas 10 is formed, the gas storage facility can be put into formal periodic injection and production operation.

[0083] S410: Gas Injection Operation

[0084] During periods of natural gas surplus (such as summer), surplus natural gas (mainly methane) from the pipeline network is injected through wellbore 3 into the storage space created and modified in steps S200-S300.

[0085] Injection pressure control: The injection pressure during the first injection-production cycle requires special attention. The peak injection pressure should be close to, but not exceed, the fracture pressure of the reservoir space formed by the combustion explosion and the surrounding rock under the current stress state. This fracture pressure can be estimated through preliminary small-scale tests, rock mechanics analysis, or analysis based on pressure drop data after the combustion explosion. The fracture pressure is related to reservoir depth; at a depth of 1000m, the fracture pressure is approximately 20-25 MPa.

[0086] Therefore, this invention, on the one hand, utilizes higher pressure to inject natural gas into the deep part of the fracture network 7 as much as possible, expanding the gas spread range; on the other hand, it can also avoid excessive pressure causing the generation of new, uncontrolled fractures or damaging the integrity of the caprock 4. Furthermore, during this high-pressure injection process, this invention acts as a "hydraulic support" for the existing fracture network 7. In this way, the system can resist geostress and maintain its open state.

[0087] S420: Gas extraction operation

[0088] During peak gas consumption periods (such as winter), natural gas stored in fracture network 7 and cavities is extracted by opening production valves to reduce bottom hole flowing pressure.

[0089] High-speed gas production is achieved thanks to the highly conductive fracture network created by combustion and explosion, resulting in minimal gas flow resistance. Therefore, even under large pressure differentials, high production can be maintained, and the bottomhole pressure drop is relatively gradual, which helps maintain a high recovery rate and a stable supply rate.

[0090] Pressure Changes and Fracture Conditions: During gas production, the pressure within the reservoir gradually decreases. Due to the support of the previous injection pressure and potential rock debris on the fracture surfaces, most fractures do not completely close even as the pressure decreases, but retain a considerable amount of residual opening, thus maintaining high conductivity.

[0091] S430: Cyclic Promotion and Dynamic Enhancement

[0092] The gas storage facility will repeat the S410 and S420 injection and production processes according to seasonal or market demand. Each complete injection and production cycle is equivalent to a reinforcement and modification of the reservoir.

[0093] Gas injection period: High-pressure injection is not only a gas storage process, but also a gentle "hydraulic crack widening" process, which consolidates and extends the crack system.

[0094] Gas extraction period: High-speed extraction verifies the unobstructed flow path, and periodic pressure fluctuations also help to clear any microscopic blockages that may form.

[0095] After multiple cycles, the gas flow channels will be further optimized under alternating pressure loads and fluid scouring, potentially resulting in higher flow efficiency than in the initial stages of reservoir construction. This continuous enhancement effect from periodic injection and production operations, combined with the static effect of the one-time high-intensity combustion-explosion modification in the S200 step, forms a long-term performance assurance mechanism that combines dynamic and static elements (such as...). Figure 5 (As shown).

[0096] In summary, this invention not only realizes the basic peak-shaving function of gas storage facilities, but also utilizes the positive enhancement effect of the injection and production process on the performance of gas storage facilities. This allows gas storage facilities to escape the predicament of natural performance degradation over time and shift to a virtuous cycle of "optimization during use and enhancement during circulation." Consequently, it ensures the long-term, efficient, and stable operation of gas storage facilities.

[0097] S500: Monitoring and Optimization

[0098] The purpose of this step is to monitor the status of the gas storage facility in real time and, based on this, to achieve intelligent and precise expansion of the gas storage capacity.

[0099] S510: Operation Monitoring

[0100] During the injection and production process, multiple technologies are used to monitor the gas storage facility in all aspects:

[0101] Microseismic monitoring: Deploy or install downhole geophone arrays around the gas storage facility. Pressure changes caused by injection and production will induce microseismic events. By monitoring the spatiotemporal distribution of these events, the real-time expansion of fracture network 7, the advancement position of the gas front, and changes in the stress field can be reconstructed, visually presenting the "outline of the gas storage facility".

[0102] Tracer monitoring: Trace amounts of chemically inert, detectable tracers (such as perfluoromethylcyclohexane, perfluorodimethylcyclohexane, etc.) are added to the injected natural gas. The timing and concentration of the tracer's presence are detected in the produced gas or surrounding monitoring wells to determine the gas flow direction, migration speed, and the presence of potential leakage channels.

[0103] Wellbore 3 Pressure / Temperature Monitoring: Using downhole permanent pressure gauges and thermometers, pressure and temperature changes within the storage space are continuously recorded. This provides the most direct dynamic data for assessing storage capacity, calculating working gas volume, and diagnosing wellbore 3 integrity.

[0104] S520: Scalable Construction Decisions

[0105] Based on the monitoring data obtained from step S510, combined with a three-dimensional geological model, a comprehensive assessment of the current state of the gas storage facility can be conducted, specifically addressing the following questions: What is the extent of the gas spillover? Which direction has the greatest potential for expansion? How is the boundary sealing?

[0106] S530: Serialization Append Ignition

[0107] When it is necessary to expand the capacity of gas storage facilities, scalable construction can be implemented. Specifically, based on the assessment results, one or more additional in-situ combustion-explosion fracturing operations can be designed and implemented at the planned boundary of the gas storage facility, or at new locations within the storage area where the gas has not been fully affected.

[0108] Serialization method: "Serialization" means that these additional detonation operations are not random, but are carried out according to a certain spatial logic and sequence. For example, they can be carried out sequentially from the bottom of the well to the top.

[0109] This allows the effective storage capacity and working gas volume of gas storage facilities to grow gradually and controllably, matching changes in future market demand.

[0110] In summary, this step transforms the construction of gas storage facilities from a "one-time, high-risk" investment into a sustainable development model of "operation, verification, and expansion," and reduces the geological risks of expansion based on real-time monitoring decisions. Simultaneously, the sequential and modular expansion approach allows for phased investment, resulting in higher capital utilization efficiency and enabling "on-demand customization" of gas storage capacity.

[0111] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing and operating an aquifer gas storage facility, characterized in that, Includes the following steps: S1. In-situ combustion and detonation fracturing is performed on the selected aquifer (5) to form a reservoir space containing a fracture network (7) and cavities in the selected aquifer (5); S2. Control the reaction conditions of the in-situ combustion and explosion fracturing so that after the reaction is completed, non-flammable gas is left in the storage space as the bottom gas of the gas storage tank. S3. Perform periodic natural gas injection and extraction operations on the storage space.

2. The method for constructing and operating an aquifer gas storage facility according to claim 1, characterized in that, In step S1, the in-situ combustion and explosion fracturing includes the following steps: The mixture of fuel gas and combustion-supporting gas is injected into the target section of the aquifer (5) and then deflagrated through the ignition electrode (8).

3. The method for constructing and operating an aquifer gas storage facility according to claim 2, characterized in that, In step S2, controlling the reaction conditions for the in-situ combustion-explosion fracturing includes the following steps: By controlling the mixing ratio of the fuel gas and the combustion-supporting gas, the gas remaining in the storage space after the combustion and explosion reaction contains carbon dioxide.

4. The method for constructing and operating an aquifer gas storage facility according to claim 3, characterized in that, The fuel gas is methane, the combustion-supporting gas is oxygen, and the volume ratio of methane to oxygen is in a fuel-rich state.

5. The method for constructing and operating an aquifer gas storage facility according to claim 4, characterized in that, The process following step S1 and before step S3 includes a well-sealing step: After the combustion reaction ends, the wellhead is closed, and the wellbore (3) and the storage space system are kept closed under the downhole ambient temperature and pressure for a preset time.

6. The method for constructing and operating an aquifer gas storage facility according to claim 5, characterized in that, The duration of the well-steaming step is determined based on the temperature and pressure recovery curve of the aquifer (5).

7. The method for constructing and operating an aquifer gas storage facility according to claim 1, characterized in that, Step S3 also includes the following steps: During the gas injection phase of the first injection-production cycle, the peak applied gas injection pressure is close to but does not exceed the fracture pressure of the reservoir space formed by the in-situ combustion and fracturing described in step S1.

8. A method for constructing and operating an aquifer gas storage facility according to any one of claims 1 to 7, characterized in that, During or after the execution of step S3, step S4 is also included: Based on the monitoring results of the reservoir space morphology and gas migration, one or more additional in-situ combustion and detonation fracturing operations are carried out at new locations within the aquifer (5).

9. The method for constructing and operating an aquifer gas storage facility according to claim 8, characterized in that, The additional in-situ combustion and fracturing is carried out in a sequential manner at the planned boundary of the gas storage facility or within the storage area.

10. The method for constructing and operating an aquifer gas storage facility according to claim 8, characterized in that, The monitoring includes at least one of microseismic monitoring, tracer monitoring or wellbore (3) pressure monitoring.

Images