An underground large cavern tank system and a nitrogen replacement method thereof

Abstract

The present application relates to the technical field of underground oil storage tank construction, and particularly relates to an underground large-scale tank system and a nitrogen replacement method thereof. The underground large-scale tank system provided by the present application comprises a vertical shaft, oil storage caverns, connecting tunnels, oil and gas pipes and nitrogen injection pipes. The oil storage caverns are arranged at intervals, and all the oil storage caverns are connected through the connecting tunnels. The vertical shaft is connected with the oil storage caverns. The oil and gas pipes and the nitrogen injection pipes are arranged at the intersection of each oil storage cavern and the connecting tunnel. The distributed arrangement mode is adopted to avoid the gas short circuit of the nitrogen inlet and the gas outlet, and the nitrogen replacement period can be obviously shortened. The replacement is sufficient, and the safety hazard can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground oil storage tank construction, in particular to an underground large tank system and a nitrogen replacement method thereof. BACKGROUND

[0002] Before the first oil is put into the underground large oil storage tank, nitrogen replacement is needed to discharge the original air in the cavern to avoid the explosive mixture formed by the oil gas volatilized after the oil is put in and the oxygen in the air.

[0003] The traditional nitrogen injection and air discharge are both carried out by vertically inserting the nitrogen pipe and the oil gas pipe into a vertical shaft. Since the tank space is large, a large amount of nitrogen is needed for replacement. For the volume of millions of cubic meters in the cavern, the density of nitrogen and air is similar, and a long time is needed for diffusion, thus leading to a long nitrogen replacement period, and there is also the problem of insufficient replacement and safety hazards. SUMMARY

[0004] The present application aims to provide an underground large tank system and a nitrogen replacement method thereof to solve the technical problem of a long nitrogen replacement period and safety hazards caused by insufficient replacement in the prior art.

[0005] The underground large tank system provided by the present application comprises a vertical shaft, an oil storage cavern, a connecting tunnel, an oil gas pipe and a nitrogen injection pipe.

[0006] The oil storage caverns are arranged at intervals, and all the oil storage caverns are connected by the connecting tunnels, and the vertical shaft is connected with the oil storage caverns.

[0007] The oil gas pipes are arranged in each oil storage cavern, and the oil gas pipes correspond to the connecting tunnels one by one. One end of each oil gas pipe extends to the intersection of the corresponding connecting tunnel and the oil storage cavern, and the other end extends to the vertical shaft for air discharge.

[0008] The nitrogen injection pipes corresponding to the oil gas pipes are arranged in each oil storage cavern, and the nitrogen injection pipes correspond to the connecting tunnels one by one. The gas outlet end of each nitrogen injection pipe extends to the intersection of the corresponding connecting tunnel and the oil storage cavern, and the gas inlet end extends to the vertical shaft for nitrogen injection.

[0009] As a further technical solution, each of the oil and gas pipes is equipped with a first flow meter, a first control valve, a sampling pipe, and a sampling valve installed on the sampling pipe. The first flow meter is used to monitor the flow rate in the oil and gas pipe, the first control valve is used to adjust the flow rate in the oil and gas pipe, the sampling pipe is connected to an oxygen content analyzer and is used to sample the oxygen content analyzer, and the sampling valve is used to open or close the sampling pipe.

[0010] Each of the nitrogen injection pipes is equipped with a second flow meter and a second control valve. The second flow meter is used to monitor the flow rate in the nitrogen injection pipe, and the second control valve is used to adjust the flow rate in the nitrogen injection pipe.

[0011] As a further technical solution, it also includes a nitrogen main pipe, which is installed inside the vertical shaft, and the inlet ends of all the nitrogen injection pipes are connected to the nitrogen main pipe;

[0012] and / or;

[0013] It also includes an oil and gas main pipeline, which is located inside the vertical shaft, and the exhaust ends of all the oil and gas pipes are connected to the oil and gas main pipeline.

[0014] As a further technical solution, the connecting tunnels are provided in three parts, namely the first connecting tunnel, the second connecting tunnel, and the third connecting tunnel;

[0015] Along the length of the oil storage cavern, the distance between the first connecting roadway and the vertical shaft is D1, the distance between the second connecting roadway and the vertical shaft is D2, and the distance between the third connecting roadway and the vertical shaft is D3, where D1 < D2 < D3.

[0016] As a further technical solution, the height of the oil storage cavern is H, the first connecting tunnel is located at 2 / 3H-H of the oil storage cavern, the second connecting tunnel is located at 1 / 3H-2 / 3H of the oil storage cavern, and the third connecting tunnel is located at 0-1 / 3H of the oil storage cavern.

[0017] As a further technical solution, the length of the oil storage cavern is L, the height of the oil storage cavern is H, and the width of the oil storage cavern is W, and L≥15×H, 0.5H≤W≤H.

[0018] As a further technical solution, the portion of the nitrogen injection pipe located inside the oil storage cavern and the portion of the oil and gas pipe located inside the oil storage cavern are both located at the top of the oil storage cavern.

[0019] This invention provides a nitrogen replacement method for a large underground cavern system, used in the aforementioned large underground cavern system. The nitrogen replacement method includes the following steps:

[0020] S1, seal the sampling pipe on each oil and gas pipe through the sampling valve, and introduce nitrogen into all nitrogen injection pipes;

[0021] S2, open the sampling tube on each oil and gas pipeline through the sampling valve to start sampling, and use an oxygen content analyzer to detect the oxygen content of the gas in each sampling tube;

[0022] S3, calculate the average oxygen content of the gas in all sampling tubes;

[0023] S4. When the average oxygen content in all sampling tubes is between 2% and 5%, stop supplying nitrogen to all nitrogen injection tubes.

[0024] As a further technical solution, a judgment and adjustment step is also included, the judgment and adjustment step comprising:

[0025] Compare the oxygen content of the gas in each sampling tube with the average oxygen content of the gas in all sampling tubes. If the oxygen content of the gas in any sampling tube exceeds 10% of the average oxygen content of the gas in all sampling tubes, then increase the opening of the first control valve on the oil and gas pipe corresponding to this sampling tube and increase the opening of the second control valve on the nitrogen injection pipe corresponding to this oil and gas pipe.

[0026] Sampling tubes with an oxygen content exceeding 10% of the average oxygen content of all sampling tubes are tested by an oxygen content analyzer. When the oxygen content of the gas in this sampling tube is within ±10% of the average oxygen content of all sampling tubes, the opening of the first control valve on the corresponding oil and gas pipe and the opening of the second control valve on the corresponding nitrogen injection pipe are restored.

[0027] As a further technical solution, step S2 also includes: obtaining the total amount of nitrogen introduced into all oil storage chambers through the second flow meter on each nitrogen injection pipe; when the total amount of nitrogen introduced accounts for 70%-99% of the total volume of all oil storage chambers, opening the sampling pipe on each oil and gas pipe through the sampling valve to start sampling, and detecting the oxygen content of the gas in each sampling pipe through an oxygen content analyzer.

[0028] Compared with existing technologies, the technical advantages of the underground large-scale cavern system and its nitrogen replacement method provided by this invention are as follows:

[0029] The underground large-scale cavern system provided by this invention includes: a vertical shaft, oil storage chambers, connecting tunnels, oil and gas pipelines, and nitrogen injection pipes; multiple oil storage chambers are spaced apart and connected to each other through multiple connecting tunnels, and the vertical shaft is connected to the oil storage chambers; each oil storage chamber is equipped with multiple oil and gas pipelines, and each oil and gas pipeline corresponds to a connecting tunnel, with one end of each oil and gas pipeline extending to the intersection of the corresponding connecting tunnel and the oil storage chamber, and the other end extending to the vertical shaft for venting; each oil storage chamber is equipped with multiple nitrogen injection pipes that correspond to the oil and gas pipelines, and each nitrogen injection pipe corresponds to a connecting tunnel, with the outlet end of each nitrogen injection pipe extending to the intersection of the corresponding connecting tunnel and the oil storage chamber, and the inlet end extending to the vertical shaft for introducing nitrogen.

[0030] Each oil storage chamber is equipped with oil and gas pipes and nitrogen injection pipes at the intersection with the connecting roadway. The distributed arrangement avoids gas short circuits between the nitrogen inlet and outlet, significantly reduces the nitrogen replacement cycle time, and ensures thorough replacement, thus avoiding safety hazards.

[0031] The nitrogen replacement method for underground large cavern tank systems provided by this invention is used in the aforementioned underground large cavern tank systems. Therefore, the technical advantages and effects achieved by this method include those achieved by the aforementioned underground large cavern tank systems, which will not be elaborated here.

[0032] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 A schematic diagram of an underground large-scale cavern system provided in an embodiment of the present invention;

[0035] Figure 2 This is a cross-sectional view of a large underground cavern system provided in an embodiment of the present invention;

[0036] Figure 3 A cross-sectional view of an oil storage cavern provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of an oil and gas pipeline provided in an embodiment of the present invention;

[0038] Figure 5This is a schematic diagram of a nitrogen injection pipeline provided in an embodiment of the present invention.

[0039] Icons: 1-Vertical shaft; 2-Oil storage chamber; 3-Pipeline assembly; 4-Oil and gas pipeline; 5-Nitrogen injection pipe; 6-First flow meter; 7-First control valve; 8-Sampling pipe; 9-Oxygen content analyzer; 10-Second flow meter; 11-Second control valve; 12-First connecting roadway; 13-Second connecting roadway; 14-Third connecting roadway; 15-Nitrogen main pipe; 16-Oil and gas main pipe; 17-Sampling valve. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0044] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0045] The specific structure is as follows: Figures 1 to 5 As shown.

[0046] This embodiment provides an underground large-scale cavern system, including: a vertical shaft 1, oil storage caverns 2, connecting tunnels, oil and gas pipes 4, and nitrogen injection pipes 5; multiple oil storage caverns 2 are spaced apart, and all oil storage caverns 2 are connected by multiple connecting tunnels, and the vertical shaft 1 is connected to the oil storage caverns 2; each oil storage cavern 2 is provided with multiple oil and gas pipes 4, and each oil and gas pipe 4 corresponds one-to-one with a connecting tunnel, one end of each oil and gas pipe 4 extends to the intersection of the corresponding connecting tunnel and the oil storage cavern 2, and the other end extends to the vertical shaft 1 for venting; each oil storage cavern 2 is provided with multiple nitrogen injection pipes 5 that correspond one-to-one with the oil and gas pipes 4, and each nitrogen injection pipe 5 corresponds one-to-one with a connecting tunnel, the outlet end of each nitrogen injection pipe 5 extends to the intersection of the corresponding connecting tunnel and the oil storage cavern 2, and the inlet end extends to the vertical shaft 1 for introducing nitrogen.

[0047] In this embodiment, each of the oil storage caverns 2 is provided with multiple pipe groups 3, and each pipe group 3 corresponds to a connecting roadway. One end of each pipe group 3 extends to the intersection of the corresponding connecting roadway and the oil storage cavern 2, and the other end extends to the vertical shaft 1. Each pipe group 3 includes corresponding oil and gas pipes 4 and nitrogen injection pipes 5.

[0048] In this embodiment, each oil storage chamber 2 is equipped with an oil and gas pipe 4 and a nitrogen injection pipe 5 at the intersection with the connecting roadway. The distributed arrangement avoids gas short circuit between the nitrogen inlet and the gas outlet, and can significantly reduce the duration of the nitrogen replacement cycle. At the same time, this arrangement ensures sufficient replacement and avoids safety hazards.

[0049] In the optional technical solution of this embodiment, each of the oil and gas pipes 4 is provided with a first flow meter 6, a first control valve 7, a sampling pipe 8, and a sampling valve 17 provided on the sampling pipe 8. The first flow meter 6 is used to monitor the flow rate in the oil and gas pipe 4, the first control valve 7 is used to adjust the flow rate in the oil and gas pipe 4, the sampling pipe 8 is connected to the oxygen content analyzer 9 and is used to sample the oxygen content analyzer 9, and the sampling valve 17 is used to open or close the sampling pipe 8; each of the nitrogen injection pipes 5 is provided with a second flow meter 10 and a second control valve 11. The second flow meter 10 is used to monitor the flow rate in the nitrogen injection pipe 5, and the second control valve 11 is used to adjust the flow rate in the nitrogen injection pipe 5.

[0050] In this embodiment, the flow rate in the oil and gas pipe 4 is monitored by the first flow meter 6, and the flow rate in the nitrogen injection pipe 5 is monitored by the second flow meter 10. When the value monitored by the second flow meter 10 is significantly greater than the value monitored by the first flow meter 6, it indicates that the pressure at the corresponding location of the oil storage cavern is high, posing a danger. At this time, the opening of the first control valve 7 can be increased and / or the opening of the second control valve 11 can be decreased. If there is no improvement, it indicates that the oil and gas pipe 4 is blocked and needs to be repaired in time. At the same time, the total amount of nitrogen introduced into all oil storage caverns 2 can be obtained by monitoring the values ​​of all the second flow meters 10. One end of the sampling pipe 8 is connected to the oil and gas pipe 4, and the other end is connected to the oxygen content analyzer 9. By opening the sampling valve 17, the sampling pipe 8 can obtain the flow rate in the oil and gas pipe 4, thereby sampling the oxygen content analyzer 9.

[0051] In the optional technical solution of this embodiment, a nitrogen main pipe 15 is further included. The nitrogen main pipe 15 is disposed within the vertical shaft 1, and the inlet ends of all the nitrogen injection pipes 5 are connected to the nitrogen main pipe 15. One end of the nitrogen main pipe 15 extends out of the vertical shaft 1, and the other end is connected to all the nitrogen injection pipes 5, to avoid pipeline confusion within the vertical shaft 1. And / or; it also includes an oil and gas main pipe 16, which is disposed within the vertical shaft 1, and the exhaust ends of all the oil and gas pipes 4 are connected to the oil and gas main pipe 16. One end of the oil and gas main pipe 16 extends out of the vertical shaft 1, and the other end is connected to all the oil and gas pipes 4, to avoid pipeline confusion within the vertical shaft 1.

[0052] This embodiment is not limited to this; it may also be that all of the nitrogen injection pipes 5 extend out of the vertical shaft 1, or all of the oil and gas pipes 4 extend out of the vertical shaft 1.

[0053] In the optional technical solution of this embodiment, three connecting tunnels are provided, namely a first connecting tunnel 12, a second connecting tunnel 13, and a third connecting tunnel 14; along the length direction of the oil storage cavern 2, the distance between the first connecting tunnel 12 and the vertical shaft 1 is D1, the distance between the second connecting tunnel 13 and the vertical shaft 1 is D2, and the distance between the third connecting tunnel 14 and the vertical shaft 1 is D3, and D1 < D2 < D3.

[0054] In the optional technical solution of this embodiment, the height of the oil storage cavern 2 is H, the first connecting tunnel 12 is located at 2 / 3H-H of the oil storage cavern 2, the second connecting tunnel 13 is located at 1 / 3H-2 / 3H of the oil storage cavern 2, and the third connecting tunnel 14 is located at 0-1 / 3H of the oil storage cavern 2.

[0055] In this embodiment, by setting up three connecting tunnels at different heights, effective communication between multiple oil storage chambers 2 can be ensured, improving the flexibility of storage and transportation.

[0056] In this embodiment, two or three oil storage chambers 2 are preferably provided, but not limited to this, and other numbers are also possible.

[0057] In this embodiment, taking the example of setting three oil storage caverns 2, there are nine pipeline groups 3, that is, nine oil and gas pipes 4 and nine nitrogen injection pipes 5.

[0058] In the optional technical solution of this embodiment, the length of the oil storage chamber 2 is L, the height of the oil storage chamber 2 is H, and the width of the oil storage chamber 2 is W, where L≥15×H and 0.5H≤W≤H. This arrangement facilitates construction and structural design. The reason for this limitation is that if the oil storage chamber 2 is too short, the cross-sectional area is large, making gas replacement easier, and a relatively long and thin oil storage chamber 2 is more effective. The longer and thinner the oil storage chamber 2, the longer the gas flow path, and the less likely it is to achieve satisfactory replacement.

[0059] In an optional technical solution of this embodiment, the portion of the nitrogen injection pipe 5 located inside the oil storage chamber 2 and the portion of the oil-gas pipe 4 located inside the oil storage chamber 2 are both located at the top of the oil storage chamber 2. This prevents the nitrogen injection pipe 5 and the oil-gas pipe 4 from being submerged after the oil storage chamber 2 is filled with oil.

[0060] This embodiment provides a nitrogen replacement method for a large underground cavern system, which is used in the aforementioned large underground cavern system. Therefore, the technical advantages and effects achieved by the nitrogen replacement method for the large underground cavern system include those achieved by the aforementioned large underground cavern system, which will not be repeated here.

[0061] The nitrogen replacement method includes the following steps:

[0062] S1, the sampling pipe 8 on each oil and gas pipe 4 is closed through the sampling valve 17, and nitrogen is introduced into all nitrogen injection pipes 5;

[0063] S2, open the sampling tube 8 on each oil and gas pipe 4 through the sampling valve 17 to start sampling, and use the oxygen content analyzer 9 to detect the oxygen content of the gas in each sampling tube 8.

[0064] S3, calculate the average value of the gas oxygen content in all sampling tubes 8;

[0065] S4. When the average oxygen content in all sampling tubes 8 is between 2% and 5%, stop supplying nitrogen to all nitrogen injection tubes 5.

[0066] In this embodiment, the nitrogen replacement method described above can effectively reduce the replacement time while ensuring thorough replacement.

[0067] In the optional technical solution of this embodiment, a judgment and adjustment step is further included, the judgment and adjustment step including:

[0068] Compare the oxygen content of the gas in each sampling tube 8 with the average oxygen content of the gas in all sampling tubes 8. If the oxygen content of the gas in any sampling tube 8 exceeds 10% of the average oxygen content of the gas in all sampling tubes 8, then increase the opening of the first control valve 7 on the oil and gas pipe 4 corresponding to this sampling tube 8 and increase the opening of the second control valve 11 on the nitrogen injection pipe 5 corresponding to this oil and gas pipe 4.

[0069] Sampling tube 8 whose oxygen content exceeds 10% of the average oxygen content of all sampling tubes 8 is detected by oxygen content analyzer 9. When the oxygen content of the gas in this sampling tube 8 is within ±10% of the average oxygen content of all sampling tubes 8, the opening of the first control valve 7 on the oil and gas pipe 4 corresponding to this sampling tube 8 and the opening of the second control valve 11 on the nitrogen injection pipe 5 corresponding to this oil and gas pipe 4 are restored.

[0070] In this embodiment, the determination and adjustment step is performed after step S3. The determination and adjustment step can effectively ensure the nitrogen replacement effect and safety.

[0071] In the optional technical solution of this embodiment, step S2 further includes: obtaining the total amount of nitrogen introduced into all oil storage chambers 2 through the second flow meter 10 on each nitrogen injection pipe 5; when the total amount of nitrogen introduced accounts for 70%-99% of the total volume of all oil storage chambers 2, opening the sampling pipe 8 on each oil and gas pipe 4 through the sampling valve 17 to start sampling, and detecting the oxygen content of the gas in each sampling pipe 8 through the oxygen content analyzer 9.

[0072] In this embodiment, sampling begins after the total amount of nitrogen introduced reaches 70%-99% of the total volume of all oil storage chambers 2, ensuring that a certain amount of nitrogen is present in the oil storage chambers 2. Sampling data obtained at this point is more accurate, effectively guaranteeing the reliability of the judgment and adjustment steps. Preferably, sampling begins after the total amount of nitrogen introduced reaches 80% of the total volume of all oil storage chambers 2, yielding even better results.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for nitrogen replacement of a large underground cavern tank system, characterized by, The underground large hole tank system comprises a shaft (1), an oil storage cave (2), connecting lanes, oil and gas pipes (4) and nitrogen injection pipes (5); The oil storage caves (2) are arranged at intervals, and all the oil storage caves (2) are communicated through the connecting lanes, and the shaft (1) is communicated with the oil storage caves (2); Each oil storage cave (2) is provided with a plurality of oil and gas pipes (4), and the oil and gas pipes (4) correspond to the connecting lanes one by one, one end of each oil and gas pipe (4) extends to the intersection of the corresponding connecting lane and the oil storage cave (2), and the other end extends to the shaft (1) for exhaust; Each oil storage cave (2) is provided with a plurality of nitrogen injection pipes (5) corresponding to the oil and gas pipes (4), and the nitrogen injection pipes (5) correspond to the connecting lanes one by one, and the gas outlet end of each nitrogen injection pipe (5) extends to the intersection of the corresponding connecting lane and the oil storage cave (2), and the gas inlet end extends to the shaft (1) for nitrogen injection; Each oil and gas pipe (4) is provided with a first flow meter (6), a first control valve (7), a sampling pipe (8) and a sampling valve (17) arranged on the sampling pipe (8), the first flow meter (6) is used for monitoring the flow in the oil and gas pipe (4), the first control valve (7) is used for adjusting the flow in the oil and gas pipe (4), the sampling pipe (8) is connected to an oxygen content analyzer (9) and is used for sampling for the oxygen content analyzer (9), and the sampling valve (17) is used for opening or closing the sampling pipe (8); Each nitrogen injection pipe (5) is provided with a second flow meter (10) and a second control valve (11), the second flow meter (10) is used for monitoring the flow in the nitrogen injection pipe (5), and the second control valve (11) is used for adjusting the flow in the nitrogen injection pipe (5); The nitrogen replacement method comprises the following steps: S1, close the sampling pipe (8) on each oil and gas pipe (4) through the sampling valve (17), and inject nitrogen into all nitrogen injection pipes (5); S2, open the sampling pipe (8) on each oil and gas pipe (4) through the sampling valve (17) to start sampling, and detect the oxygen content of the gas in each sampling pipe (8) through the oxygen content analyzer (9); S3, calculate the average value of the oxygen content of the gas in all sampling pipes (8); S4, when the average value of the oxygen content of the gas in all sampling pipes (8) is between 2% and 5%, stop injecting nitrogen into all nitrogen injection pipes (5); Further comprising a judgment and adjustment step, which comprises: Comparing the oxygen content of the gas in each sampling pipe (8) with the average value of the oxygen content of the gas in all sampling pipes (8), if the oxygen content of the gas in a sampling pipe (8) exceeds 10% of the average value of the oxygen content of the gas in all sampling pipes (8), then increase the opening degree of the first control valve (7) on the oil and gas pipe (4) corresponding to the sampling pipe (8) and increase the opening degree of the second control valve (11) on the nitrogen injection pipe (5) corresponding to the oil and gas pipe (4). The oxygen content analyzer (9) detects the sampling tube (8) whose oxygen content exceeds 10% of the average value of the oxygen content of the gas in all the sampling tubes (8), and when the oxygen content of the gas in the sampling tube (8) is within ±10% of the average value of the oxygen content of the gas in all the sampling tubes (8), the opening degree of the first control valve (7) on the oil and gas pipe (4) corresponding to the sampling tube (8) is restored, and the opening degree of the second control valve (11) on the nitrogen injection pipe (5) corresponding to the oil and gas pipe (4) is restored.

2. The method of nitrogen replacement of a large underground cavern tank system according to claim 1, wherein, The underground large hole tank system further comprises a nitrogen main pipe (15) arranged in the shaft (1), and the gas inlet ends of all the nitrogen injection pipes (5) are in communication with the nitrogen main pipe (15); and / or; The oil and gas main pipe (16) is arranged in the shaft (1), and the gas outlet ends of all the oil and gas pipes (4) are in communication with the oil and gas main pipe (16).

3. The method of nitrogen replacement of a large underground cavern tank system according to claim 1, wherein, The connecting tunnels are provided with three first connecting tunnels (12), second connecting tunnels (13) and third connecting tunnels (14); Along the length direction of the oil storage chamber (2), the distance between the first connecting tunnel (12) and the shaft (1) is D1, the distance between the second connecting tunnel (13) and the shaft (1) is D2, the distance between the third connecting tunnel (14) and the shaft (1) is D3, and D1 4. The method of nitrogen replacement of a large underground cavern tank system according to claim 3, wherein, The height of the oil storage chamber (2) is H, the first connecting tunnel (12) is located at 2 / 3H-H of the oil storage chamber (2), the second connecting tunnel (13) is located at 1 / 3H-2 / 3H of the oil storage chamber (2), and the third connecting tunnel (14) is located at 0-1 / 3H of the oil storage chamber (2).

5. The method of nitrogen replacement of a large underground cavern tank system according to any one of claims 1 to 4, characterized in that, The length of the oil storage chamber (2) is L, the height of the oil storage chamber (2) is H, and the width of the oil storage chamber (2) is W, and L≥15×H, 0.5H≤W≤H.

6. The method of nitrogen replacement of a large underground cavern tank system according to any one of claims 1 to 4, wherein The part of the nitrogen injection pipe (5) located in the oil storage chamber (2) and the part of the oil and gas pipe (4) located in the oil storage chamber (2) are located at the top of the oil storage chamber (2).

7. The method of nitrogen replacement of a large underground cavern tank system according to claim 1, wherein, In step S2, the total amount of nitrogen introduced into all the oil storage chambers (2) is obtained through the second flow meter (10) on each nitrogen injection pipe (5), and when the total amount of introduced nitrogen accounts for 70%-99% of the total volume of all the oil storage chambers (2), the sampling tube (8) on each oil and gas pipe (4) is opened for sampling through the sampling valve (17), and the oxygen content of the gas in each sampling tube (8) is detected by the oxygen content analyzer (9).

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