A drainage method using intelligent control of gas pressure in a high-pressure gas storage cavern

Abstract

The present invention discloses a drainage method using intelligent control of the air pressure in a high-pressure gas storage cavern. The method utilizes a closed water collection channel inside the gas storage cavern to collect condensate in the gas storage cavern into a water collection well. A sensor is provided in the water collection well. The water collection well is connected to a high place through a drainage connecting pipe and introduced into an external drainage pool. A valve is provided at the external end of the drainage connecting pipe. The water level in the water collection well is monitored by an intelligent control system, and appropriate control water level parameters are set. The valve is controlled by the intelligent control system. The high-pressure compressed gas in the gas storage cavern is used as a power source to automatically discharge the condensate through the drainage connecting pipe, while preventing the compressed gas in the gas storage cavern from leaking out. The present invention utilizes the high-pressure compressed air in the gas storage cavern as a power source, selects appropriate drainage conditions and timing, and automatically discharges the condensate outside the system. No external power is required, no additional equipment is required, the structure and operation are inherently safe, and maintenance is convenient. The method greatly reduces the space required for drainage pumps in the gas storage cavern.

Description

Technical Field

[0001] The present invention relates to a drainage method for a high-pressure gas storage cavern, and in particular to a drainage method utilizing intelligent control of the gas pressure in the cavern within the high-pressure gas storage cavern. Background Art

[0002] High-pressure underground gas storage caverns, such as those in compressed air storage power plants, are critical infrastructure. Underground gas storage offers advantages such as high safety, large storage capacity, flexibility, and stability. Artificially excavated underground caverns in hard rock are the most widely used type of underground gas storage cavern. To withstand the high internal pressures of high-pressure gas storage, these caverns are buried at great depths, often exceeding 200 meters. This complicates manual maintenance and mechanical equipment replacement.

[0003] Water accumulation in high-pressure underground gas storage caverns is a common problem in heat exchange coupling systems. For example, in compressed air storage power plants, the repeated compression and release of air in high-pressure underground gas storage caverns causes temperature and humidity fluctuations, converting gaseous water in the air into liquid water. If left untreated for a long time, this accumulated water can affect air humidity and corrode the steel lining inside the gas storage caverns, leading to reduced sealing performance, gas leakage, and equipment failure, thus affecting the safe and stable operation of the surrounding rock and the gas storage system. Therefore, timely, reliable, and efficient drainage of accumulated water from the caverns is essential.

[0004] Taking the high-pressure underground gas storage caverns of compressed air energy storage power plants as an example, when the caverns are activated or fully deflated, the pressure inside the caverns is equivalent to atmospheric pressure. Under normal operating conditions, the compressed air pressure inside the caverns fluctuates repeatedly, but generally maintains a high pressure (generally above 4 MPa). During drainage, it is necessary to ensure that the compressed air does not leak out, causing gas leakage and pressure relief. When the caverns are repeatedly filled and deflated, it is not only difficult to place drainage equipment, but also difficult to control, maintain, and repair. Existing pneumatic drainage structures, such as (CN111173780A, a pneumatic drainer), (CN214061669U, a pneumatic drain device for a water pit), and (CN211863876U, a pneumatic drain device for industrial MVR evaporators), all rely on metal tanks to store condensate. Due to the high corrosion and rust of metal equipment, the high maintenance and repair costs, and the small water storage capacity, they do not meet the requirements of underground high-pressure water storage and drainage environments. Other existing pneumatic drainage systems, such as (CN211624873U, vacuum drainage waterway) and (CN205012446U, simple pneumatic drainage device), have different implementation scenarios, purposes, and method paths.

[0005] Therefore, according to the operating characteristics and special requirements of high-pressure underground gas storage caverns, it is urgent to set up a reliable, durable and efficient drainage structure and control method. Summary of the Invention

[0006] The present invention aims to provide a drainage method for high-pressure gas storage caverns using intelligent control of the gas pressure inside the cavern. This method can achieve economical, stable, safe, and efficient drainage of accumulated water in high-pressure underground gas storage caverns.

[0007] The technical solution of the present invention is: a drainage method that utilizes intelligent control of the air pressure in a high-pressure gas storage cavern, utilizing a closed water collection channel inside the gas storage cavern to collect condensate in the gas storage cavern into a water collection well, a sensor is provided in the water collection well, the water collection well is led to a high place through a drainage connecting pipe and introduced into an external drainage pool, a valve is provided at the external end of the drainage connecting pipe, the water level in the water collection well is monitored by an intelligent control system, appropriate control water level parameters are set, and the valve is controlled by the intelligent control system, using the high-pressure compressed gas in the gas storage cavern as power to automatically discharge the condensate through the drainage connecting pipe, while preventing the compressed gas in the gas storage cavern from leaking out.

[0008] In the aforementioned drainage method using intelligent control of the air pressure in a high-pressure gas storage cavern, the gas storage cavern includes a plurality of gas storage caverns, one end of the gas storage cavern is connected to the main tunnel via a connecting branch tunnel, a water collection well is provided at one end of the main tunnel, a sensor is provided in the water collection well, the sensor is connected to the intelligent control system, a drainage connecting pipe is provided at the bottom of the water collection well to the ground surface or to a certain elevation above the top of the gas storage cavern, an emergency valve and a working valve are provided on the drainage connecting pipe, and the sensor, the emergency valve and the working valve are all electrically connected to the intelligent control system.

[0009] In the aforementioned drainage method using intelligent control of the gas pressure in the high-pressure gas storage cavern, the specific drainage method includes the following steps:

[0010] S1: At time t0, when the underground gas storage system has not yet injected air into the gas storage cavern, the emergency valve and the working valve are opened, and a certain volume of water is introduced into the water collection well through the drainage connecting pipe. The water level is controlled at the safe minimum water level h1. This pre-stored water can be used to seal and isolate the internal and external air pressures of the system, making the gas storage cavern pressurized.

[0011] S2: In the initial inflation state, the emergency valve and the working valve are closed in sequence, and air is injected into the gas storage cave through the underground gas storage system to start the inflation-storage-deflation cycle. During this period, at any time t', the gas storage cave begins to increase pressure, and the internal air pressure P1' is shown in formula (1). The liquid level on the right side of the drainage connecting pipe fluctuates continuously with the inflation and deflation process;

[0012] P1'=P a +γ w Δh (1)

[0013] Where, P1′─gas pressure above the free surface of the water collection well at a certain moment, kPa;

[0014] P a─1 atmospheric pressure under standard conditions, kPa;

[0015] Δh─Difference in liquid level height between the left and right sides of the drainage connecting pipe, m;

[0016] γ w ─Liquid density in the water collection well, kN / m 3 ;

[0017] S3: When the system runs a cycle and reaches a low-pressure state, and the water level in the water collection well has accumulated to the safe maximum water level h2, the working valve and the emergency valve are opened in sequence, and the condensate is automatically discharged through the drainage connecting pipe under the action of the air pressure in the air storage cavern;

[0018] S4: When the liquid level in the water collection well drops to the safe minimum water level h1, the intelligent control system is triggered to close the emergency valve first. When the condensate between the two valves is drained, the working valve is closed again. At this time, the drainage connecting pipe is full of condensate.

[0019] S5: Repeat steps S2 to S4 in a loop.

[0020] In the aforementioned drainage method using intelligent control of the air pressure in a high-pressure gas storage cavern, during normal operation, that is, the charging and discharging cycle after the initial inflation, the condensed water collected in the water collection well is discharged using air pressure in a low-pressure state. During normal operation, the emergency valve can be kept in a normally open state, and only the working valve is required for control; after the normal operation ends and before the complete pressure relief state begins, the emergency valve is slowly closed first, and then the working valve is closed.

[0021] In the aforementioned drainage method using intelligent control of the air pressure in a high-pressure gas storage cavern, a pressure-regulating valve is further provided on the pipeline between the emergency valve and the working valve. The pressure-regulating valve is electrically connected to the intelligent control system. When in a fully depressurized state, the emergency valve is first slowly opened, and the pressure-regulating valve is opened to adjust the air pressure in the drainage connecting pipe to the standard atmospheric pressure, and then the working valve is opened; when inspecting the working gate, it should be carried out under fully depressurized conditions, and the emergency valve should be closed, and the air pressure between the two valves should be controlled at the standard safety pressure through the pressure-regulating valve.

[0022] In the aforementioned drainage method using intelligent control of the internal air pressure in a high-pressure gas storage cavern, the wall of the water collection well is composed of a sealing layer, a structural layer, and a first-phase surrounding rock lining layer, and the structure of the gas storage cavern, connecting branch caverns, and connecting main tunnels is the same as that of the water collection well;

[0023] The gas storage caverns, connecting branch caverns, and water collection wells have a certain hydraulic gradient, allowing the water flow in the gas storage cavern system to flow into the water collection well by gravity. The bottom of the gas storage caverns is tangent to the bottom of the connecting branch caverns, and the bottom receives condensate. For the connecting main roadway with a flat floor, water collection tanks are installed on both sides of the bottom of the connecting main roadway to collect the condensate generated by each gas storage cavern.

[0024] The water collection well is arranged at a side away from the air inlet, an ultrasonic electrode plate for transmitting signals is pre-buried below the water collection well, and a sensitive meter sensor sheet is pre-buried above the water collection well. The lines of the ultrasonic electrode plate and the sensitive meter sensor sheet are led out to the surface through the line reserved hole and electrically connected to the intelligent control system. The line reserved hole is permanently sealed after the wiring is completed;

[0025] A water trap is provided at the connecting end of the drainage connecting pipe and the water collecting well, the connecting head between the drainage connecting pipe and the water collecting well is reliably sealed, and the drainage connecting pipe and the hole wall are filled tightly.

[0026] In the aforementioned drainage method using intelligent control of the internal gas pressure in a high-pressure gas storage cavern, the water level and volume in the water collection well should satisfy the following relationship:

[0027]

[0028] Where V a ─Volume of the water collection well below the safe minimum water level h1, m 3 ;

[0029] V b ─Volume of the water collection well above the safe maximum water level h2, m 3 ;

[0030] V5─ Volume of drainage connecting pipe, m 3 ;

[0031] V0─Condensate volume of one filling and discharging cycle, m 3 ;

[0032] The safe maximum water level h2 and the safe minimum water level h1 are the effective volume V4 of the water collection tank. The effective volume V4 of the water collection tank should satisfy the following relationship:

[0033]

[0034] Where, V4─effective volume of water collection tank, m 3 ;

[0035] V0─Condensate volume of one filling and discharging cycle, m 3 ;

[0036] n─Number of inflation and deflation cycles;

[0037] V5─ Volume of drainage connecting pipe, m 3 ;

[0038] V1─Total volume of all gas storage holes, m 3 .

[0039] In the aforementioned drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern, a signal can be emitted from the water collection well through an ultrasonic electrode plate. When the signal reaches the liquid level interface of the water collection well, a reflection will occur. The liquid level height can be calculated by the response time and the ultrasonic velocity as shown in formula (4):

[0040]

[0041] Where, h─the height of the liquid level in the water collection well under a certain working condition, m;

[0042] v─ ultrasonic emission speed, m / s;

[0043] t─Total time for ultrasonic wave to go back and forth, s.

[0044] In the aforementioned drainage method using intelligent control of the internal gas pressure in a high-pressure gas storage cavern, the buried depth of the drainage connecting pipe can be preliminarily determined according to formula (5):

[0045]

[0046] Where, P1 is the low-pressure gas pressure above the free surface of a certain liquid level in the water collection well under the operating conditions of the gas storage reservoir, kPa;

[0047] P2─the liquid level pressure at the centerline of the horizontal outlet of the tail end drainage connecting pipe, including the atmospheric pressure acting on the liquid surface, kPa;

[0048] P a ─1 atmospheric pressure under standard conditions, kPa;

[0049] H─height difference of liquid level on the left and right sides of the drainage connecting pipe, m;

[0050] H0─the height of the water column at 1 atmospheric pressure, m;

[0051] H1─corresponding water column height under the operating condition of the gas storage cave, m;

[0052] γ w ─Liquid density in the water collection well, kN / m 3 .

[0053] Beneficial effects of the present invention: Compared with the prior art, the present invention discloses a drainage method in a high-pressure gas storage cavern using intelligent control of the air pressure in the cavern. The drainage method utilizes a drainage system including a gas storage cavern as a main gas storage container, a drainage system, a water collection well, an intelligent control system and a valve system. The water collection well is provided with a water level monitoring device and a sensitive physical sensor, which are respectively used to monitor the liquid level changes and air pressure amplitude changes in the water collection well in real time, and is connected to the surface control system through a line reserved hole. Under low-pressure working conditions, an appropriate number of cycles of filling and discharging air pressure is selected. During the different operating processes of initial inflation, normal operation and complete pressure relief, the emergency valve, the working valve and the pressure regulating exhaust valve are controlled to discharge the condensate out of the mountain nearby, thereby effectively solving the practical problem of the complex drainage system in the field of underground energy storage technology, and making the water discharge system of the high-pressure underground gas storage cavern more reliable, durable and efficient.

[0054] The present invention utilizes the high-pressure compressed air inside the gas storage cavern as power, selects appropriate drainage conditions and timing, and automatically discharges condensate out of the system without the need for external power or additional equipment. The structure and operation are inherently safe, and the inspection and maintenance are convenient. The space required for drainage pumps in conventional high-pressure gas storage caverns is greatly reduced, and equipment maintenance is reduced. It is applied to water collection and drainage in gas storage reservoirs of compressed air energy storage power stations, and can achieve energy conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic diagram of the overall drainage system structure of the present invention;

[0056] Figure 2 This is a schematic diagram of the cross-sectional layout of the overall drainage system of the present invention;

[0057] Figure 3 This is a schematic diagram of the overall drainage system layout of the present invention;

[0058] Figure 4 Schematic diagram of the water collection well and its intelligent control equipment of the present invention;

[0059] Figure 5 for Figure 3 AA section view and EE section view in;

[0060] Figure 6 for Figure 3 BB, CC and DD cross-sectional views.

[0061] Figure numerals: 1-gas storage cave, 2-connecting branch cave, 3-connecting main tunnel, 4-water collection well, 401-sealing layer, 402-structural layer, 403-first phase surrounding rock lining layer, 404-ultrasonic electrode plate, 405-sensitive meter sensor plate, 5-drainage connecting pipe, 6-intelligent control system, 7-accident valve, 8-working valve, 9-pressure regulating valve, 10-line reserved hole. DETAILED DESCRIPTION

[0062] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0063] Embodiments of the present invention: A drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern, such as Figure 1-6 As shown, the condensate in the gas storage caverns is collected into a collection well 4 using a sealed internal water collection channel. The condensate is generated by the compressed air in the gas storage caverns 1 as the temperature, humidity, and pressure change dynamically. It flows along the walls of the gas storage caverns 1 to the bottom of their circular cross-sections, and then is collected in the collection well 4 through a network system of connecting branch caverns. A sensor is installed in the collection well 4, which is connected to a higher place through a drainage connecting pipe 5 and introduced into an external drainage tank. A valve is installed at the external end of the drainage connecting pipe 5. The water level in the collection well 4 is monitored by an intelligent control system 6, and appropriate control parameters are set. The intelligent control system 6 controls the valve, using the high-pressure compressed gas in the gas storage caverns as power to automatically discharge the condensate through the drainage connecting pipe 5, while preventing the compressed gas in the gas storage caverns from leaking out.

[0064] The gas storage cavern includes a number of gas storage caverns 1, one end of the gas storage caverns 1 is connected to the main tunnel 3 through a connecting branch tunnel 2, and a water collection well 4 is provided at one end of the main tunnel 3. A sensor is provided in the water collection well 4, and the sensor is connected to the intelligent control system 6. A drainage connecting pipe 5 is provided at the bottom of the water collection well 4 to the surface or a certain elevation above the top of the gas storage cavern. An emergency valve 7 and a working valve 8 are provided on the drainage connecting pipe 5, and the sensor, the emergency valve 7 and the working valve 8 are all electrically connected to the intelligent control system 6.

[0065] Based on the stress distribution of the surrounding rock and construction requirements, the cross-section of gas storage tunnel 1 is circular. The cross-section of gas storage tunnel 1 and connecting branch tunnel 2 is circular, while the cross-section of the connecting main roadway 3 is gate-shaped. The bottom of gas storage tunnel 1 is coated with an anti-corrosion coating. To ensure that condensate is collected in a desired direction, a slope is established. This allows condensate from gas storage tunnel 1 to flow sequentially into connecting branch tunnel 2, connecting main roadway 3, and finally into collection well 4.

[0066] The array-like distribution of the gas storage vessels, including the several gas storage caverns 1, connecting branch caverns 2, and the water collection well 4, ensures a defined hydraulic gradient, ensuring that water in the gas storage cavern system can flow by gravity into the water collection well 4. The bottoms of the gas storage caverns 1 and the connecting branch caverns 2 are tangent to each other, and the bottoms receive condensate. For the connecting main tunnel 3, whose floor is flat, water collection troughs 301 are located on both sides of the bottom of the connecting main tunnel 3 to collect condensate generated by each gas storage cavern 1. Their structure is consistent with the cavern structure, ensuring reliable strength and sealing. The connecting main tunnel 3 and each connecting branch cavern 2 form a water collection network. The water collection troughs 301 maintain a defined hydraulic gradient (e.g., 1%) toward the water collection well 4. Drainage flows from the proximal end of the air inlet to the distal end. The connecting branch caverns 2 and the connecting main tunnel 3 are at the same height, ensuring that both are accessible to small maintenance vehicles and personnel for travel and inspection.

[0067] The water collection well 4 is located away from the air inlet to prevent the high-pressure airflow from affecting the monitoring inside the water collection well 4, which could result in large errors in the detection data. The water collection well 4 has a circular cross-section and a pot-shaped bottom to avoid stress concentration. The wall and surrounding rock of the water collection well 4 are composed of a three-layer structure: from the inside to the outside, a sealing layer 401, a structural layer 402, and a first-phase lining surrounding rock layer 403. This structure is used to prevent groundwater disturbance within the rock from sealing the impermeable layer and provide support for the external surrounding rock pressure and internal air pressure. The sealing layer 401 is made of an airtight and water-impermeable material that acts as an anti-seepage and airtight seal. Steel plate can be used as the anti-seepage sealing material. The structural layer 402 is typically composed of materials such as reinforced concrete lining as the cavern support structure. The thickness of the reinforced concrete lining is determined by factors such as the internal gas pressure, the cavern burial depth, the surrounding rock conditions, and the external water pressure. The gas storage cavern 1, the connecting branch cavern 2, and the connecting main tunnel 3 use the same support structure and anti-seepage standards to prevent structural damage and gas leakage.

[0068] An ultrasonic electrode plate 404 for transmitting signals is embedded beneath the water collection well 4, while a sensitive meter sensor plate 405 is embedded above it. The ultrasonic electrode plate 404 measures the real-time condensate level in the water collection well 4, while the sensitive meter sensor plate 405 monitors physical parameters such as the pressure and temperature of the gas within the gas storage cavern 1. The wiring from the ultrasonic electrode plate 404 and the sensitive meter sensor plate 405 is brought to the surface through a pre-wired hole 10 for electrical connection to the intelligent control system 6. Once wired, the pre-wired hole 10 is permanently sealed to prevent leaks and air leakage. The intelligent control system 6 records the condensate level in the water collection well 4 and the air pressure, temperature, and humidity above it in real time.

[0069] A water trap is provided at the connection end between the drainage connecting pipe 5 and the water collection well 4 to ensure that under the operating conditions of the gas storage cave 1, low air pressure can press the accumulated water in the water collection well 4 out of the drainage connecting pipe 5. The connection between the drainage connecting pipe 5 and the water collection well 4 is reliably sealed, and the space between the drainage connecting pipe 5 and the hole wall is tightly filled to ensure drainage under the action of air pressure.

[0070] The surface end of drainage connection pipe 5 is connected in sequence to emergency valve 7, pressure regulating valve 9, and working valve 8. The opening and closing of these three valves are controlled by the surface intelligent control system 6. When the valves are opened, condensate is discharged from gas storage cavern 1 to the outside of the mountain. Intelligent control system 6 can be installed on the surface outside the mountain, facilitating the daily monitoring and maintenance of operations personnel.

[0071] The specific drainage method includes the following steps:

[0072] S1: At time t0, when the underground gas storage system has not yet injected air into the gas storage cavern 1, the emergency valve 7 and the working valve 8 are opened, and a certain volume of water is introduced into the water collection well 4 through the drainage connecting pipe 5. The water level is controlled at the safe minimum water level h1. At this point, the liquid levels on the left and right sides of the drainage connecting pipe 5 are flush, and the liquid pressure at the right end is at atmospheric pressure. The pre-stored water in the water collection well 4 can effectively isolate the internal and external air pressures of the system, keeping the gas storage cavern 1 pressurized.

[0073] S2: In the initial inflation state, the emergency valve 7 and the working valve 8 are closed in sequence, and air is injected into the gas storage cave 1 through the underground gas storage system to start the inflation-gas storage-gas deflation cycle. During this period, at any time t', the gas storage cave 1 begins to increase pressure, and the internal air pressure P1' is as shown in formula (1). During the pressure increase process, the liquid level on the right side of the drainage connecting pipe 5 fluctuates continuously with the inflation and deflation process;

[0074] P1'=P a +γ w Δh (1)

[0075] Where, P1′─gas pressure above the free surface of water collection well 4 at a certain moment, kPa;

[0076] P a ─1 atmospheric pressure under standard conditions, kPa;

[0077] Δh─Difference in liquid level height on the left and right sides of the drainage connecting pipe 5, m;

[0078] γ w ─Liquid density in water collection well 4, kN / m 3 ;

[0079] S3: When the system runs a cycle (inflating-storing) to a low-pressure state, and the water level in the water collection well 4 has accumulated to the safe maximum water level h2, the working valve 8 and the emergency valve 7 are opened in sequence, and the condensate is automatically discharged through the drainage connecting pipe 5 under the action of the air pressure in the air storage cavern 1 (the cavern pressure is always greater than the atmospheric pressure);

[0080] S4: As the water body is drained, when the liquid level in the water collection well 4 drops to the safe minimum water level h1, the intelligent control system 6 is triggered. The intelligent control system 6 first closes the emergency valve 7. When the condensate between the two valves is drained, the intelligent control system 6 then closes the working valve 8. At this time, the drainage connecting pipe 5 between the emergency valve 7 and the water collection well 4 is full of condensate, that is, there is air in the right side of the drainage connecting pipe 5 only during the first charging and discharging cycle;

[0081] S5: Repeat steps S2 to S4 in a loop.

[0082] During normal operation, i.e., the charge-discharge cycle after initial inflation, condensate collected in sump 4 is discharged using air pressure in a similarly low-pressure state. During normal operation, emergency valve 7 can be kept normally open, with only working valve 8 acting as the control valve. Emergency valve 7 is used only for emergency air-blocking. After normal operation ends and before full pressure relief begins, emergency valve 7 is slowly closed, followed by working valve 8.

[0083] A pressure regulating valve 9 is also provided on the pipeline between the emergency valve 7 and the working valve 8. The pressure regulating valve 9 is electrically connected to the intelligent control system 6. When the pressure is fully relieved, P1 is reduced to atmospheric pressure, and the condensate filled in the right drainage connecting pipe 5 flows back to the collection well 4 under the action of gravity. At this time, negative pressure appears in the drainage pipe cavity, so the emergency valve 7 is slowly opened, and the pressure regulating valve 9 is opened to adjust the air pressure in the drainage connecting pipe 5 to the standard atmospheric pressure, and then the working valve 8 is opened.

[0084] To ensure safety, when inspecting and repairing the working gate 8, it should be carried out under full pressure relief conditions, and the emergency valve 7 should be closed, and the air pressure between the two valves should be controlled at the standard safety pressure through the pressure regulating valve 9.

[0085] During the entire drainage process, according to the required working conditions, the opening and closing of the emergency valve 7 and the working valve 8 are controlled by the intelligent control system to adjust whether the condensate can be smoothly discharged to the outside of the system through the tail end drainage connecting pipe 5. By reasonably controlling the opening rate, the damage to the valve structure caused by the water hammer effect is avoided, and the pressure regulating valve 9 is reasonably controlled according to the different operating processes of initial inflation, normal operation, and complete pressure relief.

[0086] The surface air contact end of the tail drainage connecting pipe 5 is equipped with a working valve 8 to ensure that the pipe is full of water and pressurized, and an emergency valve 7 is provided on the side of the working valve 8 close to the water collection well 4, which is used for emergency closure in the event of an accident or regular maintenance in the pipe. The emergency valve 8 and the working valve 7 should be able to withstand 1.5 to 2 times the maximum indoor gas pressure. At the same time, the connecting branch hole 2 between the gas storage cave 1 and the water collection well 4 should ensure that people can enter for maintenance and inspection. The pressure regulating valve 9 is used to adjust the water pressure and air pressure in the drainage connecting pipe 5 under different working conditions, effectively reduce water level fluctuations, stabilize the water head, and ensure the safe and stable operation of the system. If the buried depth of the gas storage reservoir is too large, a water pump can be installed for conventional secondary pumping.

[0087] The water level volume in the water collection well 4 in the drainage system should satisfy the following relationship:

[0088]

[0089] Where V a ─Volume of water collection well 4 below the safe minimum water level h1, m 3 ;

[0090] V b ─Volume of water collection well 4 above the safe maximum water level h2, m 3 ;

[0091] V5─ Volume of drainage connecting pipe 5, m 3 ;

[0092] V0─Condensate volume of one filling and discharging cycle, m 3 .

[0093] The effective volume V4 of the sump is between the maximum safety water level h2 and the minimum safety water level h1. The volume below the minimum safety water level h1 should be greater than twice the volume of the tail drain pipe 5. When the air storage cavern 1 is in an unpressurized state (1 atmosphere), water is injected into the sump 4 to the minimum safety water level h1, ensuring that the initial water volume can fill the drain pipe 5 during the initial pressure increase of the air storage cavern 1. The remaining volume of the sump 4 above the maximum safety water level h2 should be greater than the condensate volume of one filling and discharging cycle, and there should be an additional volume twice the volume of the drain pipe 5 to ensure that the remaining space in the sump 4 can accommodate the return water from the drain pipe 5 during fault conditions and during the complete depressurization of the air storage cavern 1. Under normal charging and discharging pressure conditions, when the liquid level reaches h2, the intelligent control system 6 uses the high internal pressure of the air storage cavern 1 to force the condensate out of the drain pipe 5. When the liquid level drops to h1, drainage stops.

[0094] The effective volume V4 of the water collection tank is between the safe maximum water level h2 and the safe minimum water level h1. The effective volume V4 of the water collection tank should satisfy the following relationship:

[0095]

[0096] Where, V4─effective volume of water collection tank, m 3 ;

[0097] V0─Condensate volume of one filling and discharging cycle, m 3 ;

[0098] n─Number of inflation and deflation cycles;

[0099] V5─ Volume of drainage connecting pipe 5, m 3 ;

[0100] V1─Total volume of all gas storage holes 1, m 3 .

[0101] That is, the volume of the water collection well 4 should not be less than the volume of condensate in n cycles of inflation and deflation to avoid frequent drainage and increase the opening cycle; the volume of the water collection well 4 should also have at least 4 times the volume of the tail end drainage connecting pipe 5 to prevent the backwater in the pipeline from overflowing the wellhead; in addition to the above two volumes, the volume of the water collection well 4 should also ensure a certain safety margin volume (such as the volume of condensate in one inflation and deflation cycle); the volume of the water collection well 4 should not be greater than 0.5% of the volume of the gas storage cave 1 to avoid drainage causing a large expansion of the compressed air in the gas storage reservoir and a large decrease in air pressure.

[0102] The ultrasonic electrode plate 404 can transmit a signal in the water collection well 4. When the signal reaches the liquid level interface of the water collection well 4, it will be reflected. The liquid level height can be calculated by the response time and the ultrasonic velocity as shown in formula (4):

[0103]

[0104] Where, h─the height of the liquid level in the water collection well 4 under a certain working condition, m;

[0105] v─ ultrasonic emission speed, m / s;

[0106] t─Total time for ultrasonic wave to go back and forth, s.

[0107] The condensate drainage operation in the water collection well 4 and the tail end drainage connecting pipe 5 should be carried out in a relatively low pressure environment after the pressure is released during the operation of the gas storage cavern 1. The buried depth of the drainage connecting pipe 5 can be preliminarily determined according to formula (5):

[0108]

[0109] Where, P1 is the low-pressure gas pressure above the free surface of a certain liquid level in the water collection well 4 under the operating conditions of the gas storage reservoir, kPa;

[0110] P2─the liquid level pressure at the centerline of the ground-level outlet of the tail-end drainage connecting pipe 5, including the atmospheric pressure acting on the liquid surface, kPa;

[0111] P a ─1 atmospheric pressure under standard conditions, kPa;

[0112] H─Difference in liquid level on the left and right sides of drainage connecting pipe 5, m;

[0113] H0─the height of the water column at 1 atmospheric pressure, m;

[0114] H1─corresponding water column height under the operating condition of gas storage cave 1, m;

[0115] γ w ─Liquid density in water collection well 4, kN / m 3 .

[0116] That is, the height H of the drainage connecting pipe 5 is lower than 2 / 3 of the water column height corresponding to the low air pressure in the gas storage cave 1 under operating conditions, and 1 / 3 of the water column height corresponding to the low air pressure in the gas storage cave 1 under operating conditions is greater than the water column height corresponding to one atmospheric pressure Pa.

Claims

1. A drainage method in a high-pressure gas storage cavern utilizing intelligent control of the gas pressure in the cavern, characterized by: The condensate in the gas storage cavern is collected into a water collection well (4) by utilizing a closed water collection channel inside the gas storage cavern. A sensor is provided in the water collection well (4). The water collection well (4) is led to a higher place through a drainage connecting pipe (5) and introduced into an external drainage pool. A valve is provided at the external end of the drainage connecting pipe (5). The water level in the water collection well (4) is monitored by an intelligent control system (6). Appropriate control parameters for the water level are set. The valve is controlled by the intelligent control system (6). The high-pressure compressed gas in the gas storage cavern is used as a power source to discharge the condensate through the drainage connecting pipe (5) by itself, while preventing the compressed gas in the gas storage cavern from leaking out. The gas storage cavern includes a plurality of gas storage caverns (1), one end of the gas storage caverns (1) is connected to a connecting main tunnel (3) via a connecting branch tunnel (2), a water collection well (4) is provided at one end of the connecting main tunnel (3), a sensor is provided in the water collection well (4), the sensor is connected to an intelligent control system (6), a drainage connecting pipe (5) is provided at the bottom of the water collection well (4) to the ground surface or to a certain elevation above the gas storage cavern top, an emergency valve (7) and a working valve (8) are provided on the drainage connecting pipe (5), and the sensor, the emergency valve (7) and the working valve (8) are all electrically connected to the intelligent control system (6); The specific drainage method includes the following steps: S1: When the underground gas storage system has not yet injected air into the gas storage hole (1) t At time 0, the emergency valve (7) and the working valve (8) are opened, and a certain volume of water is introduced into the water collection well (4) through the drainage connecting pipe (5), and the water level is controlled at the safe minimum water level. h 1, the pre-stored water can be used to seal the air pressure inside and outside the isolation system, so that the air storage hole (1) is in a pressurized state; S2: In the initial inflation state, the emergency valve (7) and the working valve (8) are closed in sequence, and air is injected into the gas storage cave (1) through the underground gas storage system to start the inflation-storage-deflation cycle. At this moment, the air storage hole (1) begins to increase the pressure, and the internal pressure As shown in formula (1), the liquid level on the right side of the drainage connecting pipe (5) fluctuates continuously with the filling and releasing process; （1） Where, ─ Gas pressure above the free surface of the water collection well (4) at a certain moment, kPa; ─1 atmospheric pressure under standard conditions, kPa; ─Difference in liquid level between the left and right sides of the drainage connecting pipe (5), m; ─Liquid density in the water collection well (4), kN / m 3 ; S3: When the system runs a cycle to a low pressure state, and the water level in the water collection well (4) has accumulated to the safe maximum water level h At 2 o'clock, the working valve (8) and the emergency valve (7) are opened in sequence, and the condensate is automatically discharged through the drainage connecting pipe (5) under the action of the air pressure in the air storage cave (1); S4: When the liquid level in the water collection well (4) drops to the safe minimum water level h At 1, the intelligent control system (6) is triggered to close the emergency valve (7) first, and then close the working valve (8) when the condensate between the two valves is drained. At this time, the drainage connecting pipe (5) is full of condensate; S5: Repeat steps S2 to S4 in a loop.

2. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 1, characterized in that: During normal operation, i.e., the charging and discharging cycle after the initial inflation, the condensed water collected in the water collection well (4) is discharged by air pressure in the same low-pressure state. During normal operation, the emergency valve (7) can be kept in a normally open state, and only the working valve (8) is controlled. After the end of the normal operation state, before the start of the complete pressure relief state, the emergency valve (7) is slowly closed first, and then the working valve (8) is closed.

3. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 1 is characterized in that: A pressure regulating valve (9) is also provided on the pipeline between the emergency valve (7) and the working valve (8). The pressure regulating valve (9) is electrically connected to the intelligent control system (6). In the fully depressurized state, the emergency valve (7) is first slowly opened, and the pressure regulating valve (9) is opened to adjust the air pressure in the drainage connecting pipe (5) to the standard atmospheric pressure, and then the working valve (8) is opened. When the working valve (8) is inspected and repaired, it should be carried out under the fully depressurized working condition, and the emergency valve (7) should be closed. The air pressure between the two valves is controlled at the standard safety pressure through the pressure regulating valve (9).

4. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 1 is characterized in that: The wall of the water collection well (4) is composed of a sealing layer (401), a structural layer (402) and a first-stage surrounding rock lining layer (403); the structure of the gas storage cave (1), the connecting branch cave (2) and the connecting main tunnel (3) is the same as that of the water collection well (4); The gas storage cave (1), the connecting branch cave (2) and the water collection well (4) have a certain hydraulic gradient, so that the water flow of the gas storage cave system can flow into the water collection well (4) by gravity. The bottom side of the gas storage cave (1) is tangent to the bottom side of the connecting branch cave (2), and the bottom receives condensate. For the connecting main roadway (3) with a flat bottom plate, water collection tanks (301) for collecting condensate generated by each gas storage cavern (1) are provided on both sides of the bottom of the connecting main roadway (3); The water collection well (4) is arranged at a side away from the air inlet, an ultrasonic electrode plate (404) for transmitting signals is pre-buried below the water collection well (4), and a sensitive meter sensor plate (405) is pre-buried above the water collection well (4). The lines of the ultrasonic electrode plate (404) and the sensitive meter sensor plate (405) are led out to the surface through the line reserved hole (10) and electrically connected to the intelligent control system (6). The line reserved hole (10) is permanently sealed after the wiring is completed; A water trap is provided at the connection end of the drainage connecting pipe (5) and the water collecting well (4), the connection head between the drainage connecting pipe (5) and the water collecting well (4) is reliably sealed, and the space between the drainage connecting pipe (5) and the hole wall is densely filled.

5. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 1 is characterized in that: The water level volume in the water collection well (4) should satisfy the following relationship: （2） Where, V a ─Safe minimum water level of water collection well (4) h Volume below 1, m 3 ; V b ─ Maximum safe water level of the water collection well (4) h Volume above 2, m 3 ; V 5─ Volume of drainage connecting pipe (5), m 3 ; V 0─1 condensate volume of the filling and discharging cycle, m 3 ; Safe maximum water level h 2 and safe minimum water level h 1 is the effective volume of the water collection tank V 4. Effective volume of water collection tank V 4 The following relationship should be satisfied: （3） Where, V 4─Effective volume of water collection tank, m 3 ; V 0─1 condensate volume of the filling and discharging cycle, m 3 ; n ─Number of inflation and deflation cycles; V 5─ Volume of drainage connecting pipe (5), m 3 ; V 1─Total volume of all gas storage holes (1), m 3 .

6. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 4 is characterized in that: The ultrasonic electrode plate (404) can transmit a signal in the water collection well (4). When the signal reaches the liquid level interface of the water collection well (4), a reflection will occur. The liquid level height can be calculated by the response time and the ultrasonic velocity as shown in formula (4): （4） Where, h ─Liquid level height in the water collection well (4) under certain working conditions, m; v ─Ultrasonic emission speed, m / s; t ─Total time of ultrasound round trip, s.

7. The drainage method using intelligent control of the gas pressure in a high-pressure gas storage cavern according to claim 1 is characterized in that: The buried depth of the drainage connecting pipe (5) can be preliminarily determined according to formula (5): （5） Where, P 1─ The low-pressure gas pressure above the free surface of a certain liquid level in the water collection well (4) under the operating conditions of the gas storage reservoir, kPa; P 2─ Liquid level pressure at the centerline of the ground-level outlet of the tail-end drain connecting pipe (5), including the atmospheric pressure acting on the liquid surface, in kPa; P a ─1 atmospheric pressure under standard conditions, kPa; H ─Difference in liquid level between the left and right sides of the drainage connecting pipe (5), m; H 0─the height of the water column at 1 atmospheric pressure, m; H 1─Height of water column corresponding to the operating condition of the gas storage cave (1), m; ─Liquid density in the water collection well (4), kN / m 3 .

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