A method, apparatus, and system for safe storage of mixed gases in underground salt caverns

Abstract

The present application relates to a kind of underground salt cavern mixed gas safe storage method, device and system.The method comprises: determining whether the stratification phenomenon of underground salt cavern storage mixed gas, the mixed gas is the mixed gas formed by helium and natural gas;When determining that the stratification phenomenon of underground salt cavern storage mixed gas occurs, the mixed gas that stratification phenomenon occurs is mixed, to make the mixed gas mixed evenly stored in the underground salt cavern.This method can fully ensure the uniform distribution of mixed gas in underground salt cavern helium storage, prevent the stratification of helium small molecule gas and escape leakage and seepage loss from the top roof of salt cavern, ensure the permanent safe storage of helium in mixed gas in helium storage.

Description

Technical Field

[0001] This invention belongs to the field of mixed gas storage, specifically relating to a method, apparatus and system for safe storage of mixed gas in underground salt caverns. Background Technology

[0002] Currently, the construction of underground salt cavern storage facilities in my country has entered a stage of rapid development. Salt cavern gas storage facilities are a high-quality underground strategic material reserve carrier and are key to ensuring the peak-shaving needs of the national economy.

[0003] In order to respond to the strategic needs of national energy reserves, rapidly improve my country's helium reserve capacity and ensure the security of helium supply, the use of salt caverns as a high-quality storage medium for long-term helium storage has been proposed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method, apparatus, and system for the safe storage of mixed gases in underground salt caverns. This method, apparatus, and system can effectively ensure the uniform distribution of mixed gases within the underground salt cavern helium storage facility, prevent the stratification of small helium molecules and their escape, leakage, and seepage from the top plate of the salt cavern, and guarantee the permanent and safe storage of helium in the mixed gas within the storage facility.

[0005] The technical solution adopted in this invention is as follows.

[0006] In a first aspect, a method for safely storing a mixed gas in an underground salt cavern is provided, the method comprising:

[0007] To determine whether the mixed gas stored in the underground salt cavern exhibits stratification, wherein the mixed gas is a mixture of helium and natural gas;

[0008] When it is determined that the mixed gas stored in the underground salt cavern exhibits stratification, the stratified mixed gas is mixed to ensure that the mixed gas is uniformly mixed and stored in the underground salt cavern.

[0009] Optionally, determining whether the mixed gas stored in the underground salt cavern exhibits stratification includes:

[0010] The methane concentration information detected by each laser sensor in the laser sensor group is obtained. The laser sensor group includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity.

[0011] Based on the methane concentration information detected by each laser sensor in the laser sensor group, determine whether the methane concentration at the bottom, middle and top of the underground salt cavern is distributed in descending order;

[0012] When the methane concentration at the bottom, middle, and top of the underground salt cavern is distributed from high to low, it is determined that the mixed gas stored in the underground salt cavern exhibits stratification.

[0013] Optionally, before determining that the mixed gas stored in the underground salt cavern exhibits stratification, the method further includes:

[0014] Obtain the temperature difference characteristic curves along the composite optical cable before and after heating, as measured by the distributed optical fiber temperature measurement system.

[0015] Compare the temperature difference characteristic curves along the composite optical cable before and after heating;

[0016] Accordingly, the determination that the mixed gas stored in the underground salt cavern exhibits stratification includes:

[0017] When the temperature difference characteristic curve along the composite optical cable after heating exceeds the set fluctuation range compared to the temperature difference characteristic curve before heating, and a clear interface appears, it is determined that the mixed gas stored in the underground salt cavern has stratified.

[0018] Optionally, mixing the gas mixture that exhibits stratification includes:

[0019] The mixed gas is injected into or discharged from the underground salt cavern cavity through a straight pipe, which is vertically arranged within the underground salt cavern cavity.

[0020] Optionally, the method further includes:

[0021] Determine whether the stratification phenomenon has disappeared;

[0022] Once it is determined that the stratification phenomenon has disappeared, mixing of the gas mixture in which stratification occurred should be stopped.

[0023] Secondly, a safe storage device for mixed gas in an underground salt cavern is provided, the device comprising:

[0024] A determination module is used to determine whether the mixed gas stored in the underground salt cavern exhibits stratification, wherein the mixed gas is a mixture of helium and natural gas;

[0025] A mixing module is used to mix the stratified mixed gases when it is determined that the mixed gases stored in the underground salt cavern exhibit stratification, so as to ensure that the mixed gases are uniformly mixed and stored in the underground salt cavern.

[0026] Thirdly, an underground salt cavern mixed gas safe storage system is provided, the underground salt cavern mixed gas safe storage system comprising: a detection device, a mixing device, and a safe storage device;

[0027] The detection device is used to detect whether the mixed gas stored in the underground salt cavern exhibits stratification, and to obtain information on the stratification phenomenon. The mixed gas is a mixture of helium and natural gas.

[0028] The safe storage device is used to determine whether the mixed gas stored in the underground salt cavern exhibits stratification based on the stratification information; when it is determined that the mixed gas stored in the underground salt cavern exhibits stratification, the mixing device is used to mix the stratified mixed gas so that the mixed gas is uniformly mixed and stored in the underground salt cavern.

[0029] Optionally, the stratification information includes methane concentration information.

[0030] The detection device includes a laser sensor array.

[0031] The laser sensor group includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity.

[0032] Each laser sensor in the laser sensor group is used to detect the methane concentration and obtain the methane concentration information.

[0033] Optionally, the stratification information also includes temperature difference characteristic curves along the composite optical cable before and after heating, wherein the composite optical cable is vertically arranged within the underground salt cavern cavity.

[0034] The detection device also includes a distributed fiber optic temperature measurement system.

[0035] The distributed fiber optic temperature measurement system includes a distributed temperature sensor host, the composite optical cable, and a heating control module.

[0036] The composite optical cable includes a multimode optical fiber and a heating wire. The multimode optical fiber is used to transmit photoelectric and temperature-sensitive signals, and the heating wire is used for heating.

[0037] The distributed temperature sensing host is used to control the heating wire to heat through the heating control module, collect the photoelectric temperature-sensitive signals transmitted by the multimode optical fiber before and after heating, and calculate the temperature difference characteristic curves of the composite optical cable before and after heating based on the collected photoelectric temperature-sensitive signals transmitted by the multimode optical fiber before and after heating.

[0038] Optionally, the mixing device includes a straight pipe arranged vertically within the underground salt cavern cavity.

[0039] The advantages of this invention are as follows: By determining whether the mixed gas stored in the underground salt cavern exhibits stratification, the mixed gas being a mixture of helium and natural gas, it can be observed that due to the different specific heat capacities of different gases, smaller molecules such as helium gradually rise to the top of the salt cavern cavity, while larger molecules such as natural gas and methane gradually sink to the bottom, resulting in stratification of the helium and natural gas mixture. Stratification can lead to helium escaping and leaking from the top plate of the salt cavern, causing leakage losses and safety hazards. When stratification is confirmed in the underground salt cavern, mixing the stratified gas can ensure a uniform distribution of the mixed gas within the underground salt cavern helium storage facility, preventing the stratification of small helium molecules and their escape, leakage, and loss from the top plate of the salt cavern, thus ensuring the permanent and safe storage of helium in the mixed gas within the helium storage facility. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of an underground salt cavern mixed gas safe storage system provided in an embodiment of the present invention;

[0041] Figure 2 A flowchart illustrating a method for the safe storage of mixed gas in underground salt caverns, as provided in an embodiment of the present invention;

[0042] Figure 3 A flowchart illustrating another method for safe storage of mixed gas in underground salt caverns, as provided in an embodiment of the present invention;

[0043] Figure 4 This is a structural block diagram of an underground salt cavern mixed gas safety storage device provided in an embodiment of the present invention. Detailed Implementation

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

[0045] Figure 1 This is a schematic diagram of a safe storage system for mixed gas in an underground salt cavern, provided in an embodiment of the present invention. (See attached diagram.) Figure 1 The underground salt cavern mixed gas safety storage system includes: a detection device 11, a mixing device 12, and a safety storage device 13.

[0046] The detection device 11 is used to detect whether the mixed gas stored in the underground salt cavern exhibits stratification and to obtain information on the stratification phenomenon.

[0047] The safety storage device 13 is used to determine whether the mixed gas stored in the underground salt cavern has stratified according to the stratification information; when it is determined that the mixed gas stored in the underground salt cavern has stratified, the mixing device 12 mixes the mixed gas that has stratified so that the mixed gas is uniformly mixed and stored in the underground salt cavern.

[0048] The mixed gas is a mixture of at least two different gases. For example, the mixed gas is a mixture of helium and natural gas.

[0049] In this embodiment, a detection device detects whether the mixed gas stored in the underground salt cavern exhibits stratification, obtaining stratification information. Based on this information, a safety storage device determines whether the mixed gas stored in the underground salt cavern exhibits stratification. The mixed gas is a mixture of helium and natural gas. Due to the different specific heat capacities of different gases, smaller molecules such as helium gradually rise to the top of the salt cavern cavity, while larger molecules such as natural gas and methane gradually sink to the bottom, resulting in stratification of the helium and natural gas mixture. Stratification will cause helium to escape and leak from the top plate of the salt cavern, causing leakage losses and posing safety hazards. When stratification is confirmed in the underground salt cavern, a mixing device is used to mix the stratified gas, ensuring a uniform distribution of the mixed gas within the underground salt cavern helium storage facility. This prevents the stratification of small helium molecules and their escape and leakage from the top plate of the salt cavern, ensuring the permanent and safe storage of helium in the storage facility.

[0050] In one embodiment, the stratification information includes methane concentration information. Correspondingly, the detection device 11 includes a laser sensor group. The laser sensor group includes a bottom laser sensor 111, a middle laser sensor 112, and a top laser sensor 113. The bottom laser sensor 111 is installed at the bottom of the underground salt cavern cavity, the middle laser sensor 112 is installed in the middle of the underground salt cavern cavity, and the top laser sensor 113 is installed at the top of the underground salt cavern cavity.

[0051] Each laser sensor in the laser sensor group is used to detect methane concentration and obtain methane concentration information.

[0052] Correspondingly, the safety storage device 13 is used to acquire methane concentration information detected by each laser sensor in the laser sensor group; based on the methane concentration information detected by each laser sensor in the laser sensor group, determine whether the methane concentration at the bottom, middle and top of the underground salt cavern cavity is distributed in descending order; when the methane concentration at the bottom, middle and top of the underground salt cavern cavity is distributed in descending order, determine that the mixed gas stored in the underground salt cavern has stratified.

[0053] In another embodiment, the stratification information includes temperature difference characteristic curves along the composite optical cable 115 before and after heating, the composite optical cable 115 being vertically arranged within the underground salt cavern cavity. Correspondingly, the detection device 11 includes a distributed fiber optic temperature measurement system. The distributed fiber optic temperature measurement system includes a DTS (Distributed Temperature Sensing) host 118, the composite optical cable 115, and a heating control module 119.

[0054] The composite optical cable 115 includes a multimode optical fiber 116 and a heating wire 117. The multimode optical fiber 116 is used to transmit photoelectric and temperature-sensitive signals, and the heating wire 117 is used for heating.

[0055] The DTS host 118 is used to control the heating wire 117 to heat through the heating control module 119, collect the photoelectric temperature-sensitive signals transmitted by the multimode fiber 116 before and after heating, and calculate the temperature difference characteristic curves along the composite optical cable 115 before and after heating based on the collected photoelectric temperature-sensitive signals transmitted by the multimode fiber 116 before and after heating.

[0056] Correspondingly, the safe storage device 13 is used to acquire the temperature difference characteristic curves along the composite optical cable 115 before and after heating, as measured by the distributed optical fiber temperature measurement system; compare the temperature difference characteristic curves along the composite optical cable 115 before and after heating; and determine that the mixed gas stored in the underground salt cavern has stratified when the fluctuation range of the temperature difference characteristic curve along the composite optical cable 115 after heating exceeds the set fluctuation range and a clear interface appears.

[0057] The temperature difference characteristic curve refers to the temperature-length curve in a plane coordinate system. In this plane coordinate system, one axis represents the length of the composite optical cable 115, and the other axis represents the temperature.

[0058] The fluctuation range refers to the difference in temperature values ​​at the same measurement location on the composite optical cable 115. The measurement location is marked by length, such as 20 meters on the composite optical cable 115.

[0059] A clear interface refers to a situation where, in two adjacent composite optical cable segments 115, the temperature values ​​corresponding to each measurement position are the same in one composite optical cable segment 115, the temperature values ​​corresponding to each measurement position are the same in the other composite optical cable segment 115, and the temperature values ​​corresponding to the two composite optical cable segments 115 are different and the difference exceeds a predetermined difference.

[0060] In another embodiment, the stratification information includes methane concentration information and temperature difference characteristic curves along the composite optical cable 115 before and after heating. Correspondingly, the detection device 11 includes a laser sensor group and a distributed optical fiber temperature measurement system.

[0061] Correspondingly, the safe storage device 13 is used to acquire methane concentration information detected by each laser sensor in the laser sensor group; determine whether the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is distributed from largest to smallest based on the methane concentration information detected by each laser sensor in the laser sensor group; when the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is distributed from largest to smallest, acquire the temperature difference characteristic curves along the composite optical cable 115 measured by the distributed fiber optic temperature measurement system before and after heating; compare the temperature difference characteristic curves along the composite optical cable 115 before and after heating; when the fluctuation amplitude of the temperature difference characteristic curve along the composite optical cable 115 after heating exceeds the set fluctuation amplitude compared to the temperature difference characteristic curve before heating, and a clear interface appears, it is determined that the mixed gas stored in the underground salt cavern has stratified.

[0062] The laser sensor array allows for real-time, all-weather acquisition and analysis of methane concentrations in three layers of the underground salt cavern. The distributed fiber optic temperature measurement system, based on an actively heated optical cable, is used to actively heat and test the stratification of the mixed gas within the salt cavern cavity, and analyze the top-to-bottom distribution of the mixed gas. This represents a manual, proactive, timed, qualitative, and quantitative analysis of the mixed gas state. By coordinating the laser sensor array and the distributed fiber optic temperature measurement system, when the laser sensor array detects significant differences in methane concentration values ​​across the three layers of the salt cavern cavity, it indicates that stratification has essentially occurred in the mixed gas within the cavity. To further verify whether stratification has occurred in the mixed gas within the salt cavern cavity, the distributed fiber optic temperature measurement system based on the actively heated optical cable is activated. The heating control module 119 controls the heating wire 117 to begin heating, and the DTS host 118 calculates and analyzes the temperature difference characteristic curves of the composite optical cable 115 before and after heating. If the temperature difference characteristic curve obtained by the DTS host 118 fluctuates greatly and obvious interface appears, it further proves the generation of the stratification phenomenon of the mixed gas and improves the accuracy of the stratification phenomenon judgment.

[0063] Optionally, the mixing device 12 includes a straight pipe 121, which is vertically arranged within the underground salt cavern cavity.

[0064] Correspondingly, the safety storage device 13 is used to inject mixed gas into the bottom of the underground salt cavern cavity or discharge mixed gas from the underground salt cavern through the straight pipe 121 when it is determined that the mixed gas stored in the underground salt cavern has stratified.

[0065] Optionally, the safety storage device 13 is also used to determine whether the stratification phenomenon has disappeared; when it is determined that the stratification phenomenon has disappeared, the mixing of the mixed gas in which the stratification phenomenon occurred is stopped. At this time, the straight-through pipe 121 is closed to stop the injection of mixed gas into the bottom of the underground salt cavern or the discharge of mixed gas from the underground salt cavern.

[0066] Optionally, the safety storage device 13 is used to acquire methane concentration information detected by each laser sensor in the laser sensor group; determine whether the methane concentration at the bottom, middle and top of the underground salt cavern cavity is consistent based on the methane concentration information detected by each laser sensor in the laser sensor group; and determine that the stratification phenomenon has disappeared when the methane concentration at the bottom, middle and top of the underground salt cavern cavity is consistent.

[0067] Optionally, the safe storage device 13 is used to acquire the temperature difference characteristic curves along the composite optical cable 115 before and after heating, as measured by the distributed optical fiber temperature measurement system; compare the temperature difference characteristic curves along the composite optical cable 115 before and after heating; and determine that the stratification phenomenon has disappeared when the fluctuation amplitude of the temperature difference characteristic curve along the composite optical cable 115 after heating compared with the temperature difference characteristic curve before heating does not exceed the set fluctuation amplitude.

[0068] See Figure 1 The top of the underground salt cavern is equipped with a central tube column 800, which is used to transport a large amount of mixed gas into the underground salt cavern for storage.

[0069] One end of the straight-through pipe 121 is located outside the inlet of the central tubing 800, and the other end is located at the bottom of the underground salt cavern cavity. A control valve 122 is installed at one end of the straight-through pipe 121. This control valve 122 is used to discharge or inject trace amounts of the mixed gas. The central tubing 800 and control valve 122 provide sealing control of the underground salt cavern, ensuring the airtightness and safety of the underground salt cavern helium storage facility.

[0070] The laser sensor can be installed on the straight pipe 121. The bottom laser sensor 111, the middle laser sensor 112, and the top laser sensor 113 are fixed at the bottom, middle, and top positions of the straight pipe 121, respectively.

[0071] The laser sensor can be connected to the secure storage device 13 via laser communication cable 114. Laser communication cable 114 can be arranged together with composite optical cable 115. Laser communication cable 114 and composite optical cable 115 can be integrated into a single armored optical cable. This armored optical cable can be installed on a straight-through pipe 121 via a pipe coupling.

[0072] The DTS host 118 of the distributed fiber optic temperature measurement system can be connected to the secure storage device 13.

[0073] The laser sensor array mainly consists of a laser communication cable 114, a bottom miniature laser sensor, a middle miniature laser sensor, and a top miniature laser sensor. The safe storage device 13 controls the top, middle, and bottom miniature laser sensors located at the top, middle, and bottom of the salt cavern respectively via the laser communication cable 114, and uploads the methane concentration in the mixed gas at each location in real time, thereby obtaining the methane gas molecule concentration in the mixed gas at the bottom, middle, and bottom sections of the salt cavern. If the three methane concentration values ​​are distributed from top to bottom from smallest to largest, it indicates that the mixed gas stored in the salt cavern for a long time has begun to show stratification of helium and natural gas, thus indicating that measures need to be taken to prevent the mixed gas from stratifying.

[0074] For the distributed fiber optic temperature measurement system, this part mainly consists of a high-precision DTS host 118, a heating control module 119, a multimode fiber 116, and a heating wire 117. The multimode fiber 116 and the heating wire 117 can be integrated into a single downhole armored composite optical cable 115. The DTS host 118 is mainly used to collect and analyze the photoelectric temperature-sensitive signals (inverse Stokes signals) of the multimode fiber 116 in the downhole composite optical cable 115 before and after heating by the heating wire 117, and to calculate the temperature difference characteristic curves along the downhole composite optical cable 115 before and after heating by the heating wire 117. The heating control module 119 is mainly used to energize the heating wire 117 in the downhole composite optical cable 115, causing it to heat up and generate a certain amount of heat, which in turn causes the different gases around the downhole armored composite optical cable 115 to absorb heat. Due to the different specific heat capacities of various gases (helium Cp=5238.3 J / (kg•K), methane Cp=2215.24 J / (kg•K), water Cp=4200 J / (kg•K)), the rates at which different gases absorb heat vary, resulting in varying rates of temperature rise around the armored composite optical cable 115. This difference in the anti-Stokes signal is detected in real-time by the DTS host 118, thus determining the rate of temperature calculation signal curve generation. The multimode fiber 116 is a stable sensing unit connected to the DTS host 118. The heating wire 117 is an energized heating control unit used to actively heat the downhole composite optical cable 115, thereby inducing heat absorption by the surrounding gas and generating a temperature-sensitive characteristic curve.

[0075] If the three methane concentration values ​​are distributed from top to bottom from smallest to largest, and the temperature curve shown by the distributed fiber optic temperature measurement system is uneven, it indicates that the mixed gas stored in the salt cavern for a long time has begun to exhibit stratification of helium and natural gas. In this case, control valve 122 needs to be opened to appropriately release high-pressure gas or inject mixed gas, thereby disrupting the static stratification state of the mixed gas within the salt cavern. Because the helium storage chamber contains high-pressure gas, even a slight release or injection of gas at the bottom of the salt cavern will disrupt the static state of the mixed gas. Under the influence of molecular dynamics, the mixed gas can be re-stirred and homogenized.

[0076] This embodiment does not limit the specific structure of the laser sensor and the distributed fiber optic temperature measurement system. The underground salt cavern mixed gas safe storage system provided in this embodiment can use the laser sensor and the distributed fiber optic temperature measurement system in the prior art.

[0077] Figure 2 This is a flowchart illustrating a method for the safe storage of mixed gas in underground salt caverns, as provided in an embodiment of the present invention. The entity executing this method may be... Figure 1 The safety storage device is shown. See also Figure 2 The process for the safe storage of mixed gas in underground salt caverns includes the following steps.

[0078] Step 21: Determine whether the mixed gas stored in the underground salt cavern exhibits stratification.

[0079] If stratification is detected in the mixed gas stored in the underground salt cavern, proceed to step 22. If stratification is not detected in the mixed gas stored in the underground salt cavern, continue to monitor whether stratification occurs.

[0080] The mixed gas is a mixture of at least two different gases. For example, the mixed gas is a mixture of helium and natural gas.

[0081] Step 22: Mix the gas mixture that shows stratification so that the gas mixture is evenly mixed and stored in the underground salt cavern.

[0082] In this embodiment, the presence of stratification in the mixed gas stored in the underground salt cavern is determined. The mixed gas is a mixture of helium and natural gas. Due to the different specific heat capacities of different gases, smaller molecules such as helium gradually rise to the top of the salt cavern cavity, while larger molecules such as natural gas and methane gradually sink to the bottom, resulting in stratification of the helium and natural gas mixture. Stratification can lead to helium escaping and leaking from the top plate of the salt cavern, causing leakage losses and safety hazards. When stratification is confirmed in the mixed gas stored in the underground salt cavern, mixing the stratified gas can ensure a uniform distribution of the mixed gas within the underground salt cavern helium storage facility, prevent the stratification of small helium molecules and their escape and leakage from the top plate of the salt cavern, and ensure the permanent and safe storage of helium in the mixed gas within the helium storage facility.

[0083] Figure 3 This is a flowchart illustrating another method for the safe storage of mixed gas in underground salt caverns, provided by an embodiment of the present invention. The entity executing this method may be... Figure 1 The safety storage device is shown. See also Figure 3 The process for the safe storage of mixed gas in underground salt caverns includes the following steps.

[0084] Step 31: Inject the mixed gas into the underground salt cavern.

[0085] The mixed gas can be a mixture of helium and natural gas.

[0086] In the helium storage facility at the well site of the underground salt cavern, a certain proportion of a mixture of helium and natural gas is injected into the underground salt cavern cavity through the central tubing at the wellhead. For example, the volume ratio of helium to natural gas is 10%, to ensure the safe high-pressure injection of the mixture.

[0087] After a certain volume ratio of mixed gas is injected into an underground salt cavern, it is left to stand for a period of time according to actual needs. Theoretically, the mixed gas will not stratify during this period. However, as time goes by and due to the influence of deep strata geothermal and other multiphase media, the overall temperature of the mixed gas will first gradually decrease and become fully homogenized. Then, after a period of time, influenced by the stratum temperature, it will gradually increase in temperature. Due to the different specific heat capacities of helium and natural gas molecules, stratification begins to occur. Small molecules such as helium gradually rise to the top of the salt cavern, while large molecules such as natural gas and methane gradually sink to the bottom. Ultimately, the salt cavern will contain, from top to bottom, small molecules such as helium and hydrogen, medium-sized molecules such as methane, and large particles such as propane in natural gas. This results in a stratification phenomenon from top to bottom within the cavern based on the size and physicochemical properties of the gas molecules.

[0088] Step 32: Determine whether the mixed gas stored in the underground salt cavern exhibits stratification.

[0089] If it is determined that the mixed gas stored in the underground salt cavern does not exhibit stratification, continue testing to check for stratification. If it is determined that stratification has occurred, proceed to step 33.

[0090] In one implementation, step 32 includes A1 and A2.

[0091] A1. Obtain the methane concentration information detected by each laser sensor in the laser sensor group.

[0092] The laser sensor group includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity.

[0093] A2. Based on the methane concentration information detected by each laser sensor in the laser sensor group, determine whether the methane concentration at the bottom, middle and top of the underground salt cavern is distributed in descending order.

[0094] When the methane concentration at the bottom, middle, and top of the underground salt cavern cavity decreases sequentially, it is determined that the mixed gas stored in the underground salt cavern exhibits stratification. When the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is uniform, it is determined that the mixed gas stored in the underground salt cavern does not exhibit stratification, and A1 is executed.

[0095] In another implementation, step 32 includes B1 and B2.

[0096] B1. Obtain the temperature difference characteristic curves along the composite optical cable before and after heating, as measured by the distributed optical fiber temperature measurement system.

[0097] The composite optical cable is vertically arranged inside the underground salt cavern.

[0098] B2. Compare the temperature difference characteristic curves along the composite optical cable before and after heating.

[0099] When the temperature difference characteristic curve of the composite optical cable after heating exceeds the set fluctuation range compared with the temperature difference characteristic curve before heating, and a clear interface appears, it is determined that the mixed gas stored in the underground salt cavern has stratified.

[0100] When the fluctuation range of the temperature difference characteristic curve along the composite optical cable after heating is not greater than the fluctuation range of the temperature difference characteristic curve before heating, it is determined that the mixed gas stored in the underground salt cavern has not shown stratification.

[0101] In another embodiment, step 32 includes C1-C4.

[0102] C1. Obtain the methane concentration information detected by each laser sensor in the laser sensor group.

[0103] C2. Based on the methane concentration information detected by each laser sensor in the laser sensor group, determine whether the methane concentration at the bottom, middle and top of the underground salt cavern is distributed in descending order.

[0104] When the methane concentration at the bottom, middle, and top of the underground salt cavern is distributed from highest to lowest, proceed to step C3. When the methane concentration at the bottom, middle, and top of the underground salt cavern is the same, it is determined that the mixed gas stored in the underground salt cavern has not stratified, and proceed to step C1.

[0105] C3. Obtain the temperature difference characteristic curves along the composite optical cable before and after heating, as measured by the distributed optical fiber temperature measurement system.

[0106] C4. Compare the temperature difference characteristic curves along the composite optical cable before and after heating.

[0107] When the temperature difference characteristic curve of the composite optical cable after heating exceeds the set fluctuation range compared with the temperature difference characteristic curve before heating, and a clear interface appears, it is determined that the mixed gas stored in the underground salt cavern has stratified.

[0108] When the fluctuation range of the temperature difference characteristic curve after heating along the composite optical cable does not exceed the set fluctuation range compared to the temperature difference characteristic curve before heating, it is determined that the mixed gas stored in the underground salt cavern has not shown stratification, and C1 is executed.

[0109] To detect the stratification of gas molecules within the salt cavern cavity from top to bottom, a real-time methane detection system based on multiple sets of point-type micro laser sensors was activated to monitor the methane concentration at the top, middle, and bottom of the cavity. Significant differences in methane concentration indicate that stratification has occurred within the cavity. To further verify stratification, a distributed fiber optic temperature measurement system based on an actively heated optical cable was activated. The heating control module activated the heating wires in the armored downhole optical cable, and the DTS (Digital Transmission System) host recorded the temperature difference curves before and after heating. This verified the stratification and analyzed the stratification characteristic curves. Large fluctuations and distinct interfaces in the temperature difference curves obtained by the DTS further confirm the presence of other stratification phenomena.

[0110] Step 33: Mix the gas mixture that shows stratification so that the gas mixture is evenly mixed and stored in the underground salt cavern.

[0111] The mixing methods include injecting or releasing the mixed gas from the underground salt cavern through a straight pipe. The straight pipe is arranged vertically within the underground salt cavern cavity.

[0112] After confirming that the mixed gas in the salt cavern cavity has stratified, the control valve on the straight pipeline at the wellhead is opened to control the appropriate discharge or injection of the mixed gas at the bottom of the cavity through the straight pipeline, thereby disturbing the movement of the mixed gas molecules throughout the cavity and ultimately achieving the re-dispersal and homogenization of the mixed gas in the helium storage tank.

[0113] Step 34: Determine if the stratification phenomenon has disappeared.

[0114] If the stratification phenomenon has not disappeared, proceed to step 33. If the stratification phenomenon has disappeared, proceed to step 35.

[0115] In one embodiment, step 34 includes: acquiring methane concentration information detected by each laser sensor in the laser sensor group; determining whether the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is consistent based on the methane concentration information detected by each laser sensor in the laser sensor group; and determining that the stratification phenomenon has disappeared when the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is consistent.

[0116] In another approach, step 34 includes: acquiring the temperature difference characteristic curves along the composite optical cable before and after heating, measured by the distributed optical fiber temperature measurement system; comparing the temperature difference characteristic curves along the composite optical cable before and after heating; and determining that the stratification phenomenon has disappeared when the fluctuation range of the temperature difference characteristic curve along the composite optical cable after heating compared with the temperature difference characteristic curve before heating does not exceed the set fluctuation range.

[0117] In another approach, step 34 includes: acquiring methane concentration information detected by each laser sensor in the laser sensor group; determining whether the methane concentrations at the bottom, middle, and top of the underground salt cavern cavity are consistent based on the methane concentration information detected by each laser sensor in the laser sensor group; when the methane concentrations at the bottom, middle, and top of the underground salt cavern cavity are consistent, acquiring the temperature difference characteristic curves along the composite optical cable measured by the distributed fiber optic temperature measurement system before and after heating; comparing the temperature difference characteristic curves along the composite optical cable before and after heating; when the fluctuation amplitude of the temperature difference characteristic curve along the composite optical cable after heating compared to the temperature difference characteristic curve before heating does not exceed a set fluctuation amplitude, determining that the stratification phenomenon has disappeared.

[0118] The set fluctuation range can be 0. If the fluctuation range of the temperature difference characteristic curve along the composite optical cable after heating is less than that of the temperature difference characteristic curve before heating, then the temperature difference characteristic curves along the composite optical cable before and after heating are both straight lines.

[0119] Step 35: Stop mixing the gas mixture that has shown stratification.

[0120] Once it is determined that the stratification phenomenon has disappeared, close the straight-through pipe and stop injecting mixed gas into the bottom of the underground salt cavern or stop discharging mixed gas from the underground salt cavern, so that the mixed gas can be stored in the underground salt cavern cavity.

[0121] After executing step 33 for a period of time (e.g., 1 hour), recheck in step 34 whether the DTS temperature difference characteristic curve has returned to a straight line and whether the methane concentrations of the upper, middle, and lower layers are consistent. If the DTS temperature difference characteristic curve has returned to a straight line and the methane concentrations of the upper, middle, and lower layers are consistent, then close the control valve on the wellhead direct pipeline and let it stand for a period of time again (e.g., 24 hours).

[0122] Figure 4 A structural block diagram of an underground salt cavern mixed gas safety storage device provided in an embodiment of the present invention is shown below. Figure 4 The underground salt cavern mixed gas safety storage device includes: a determination module 41 and a mixing module 42.

[0123] Module 41 is used to determine whether the mixed gas stored in the underground salt cavern exhibits stratification. The mixed gas is a mixture of helium and natural gas.

[0124] The mixing module 42 is used to mix the stratified mixed gas when it is determined that the mixed gas stored in the underground salt cavern has stratified, so as to make the mixed gas uniformly stored in the underground salt cavern.

[0125] Optionally, the determining module 41 is used to acquire methane concentration information detected by each laser sensor in the laser sensor group, which includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity. Based on the methane concentration information detected by each laser sensor in the laser sensor group, it determines whether the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is distributed in descending order. When the methane concentration at the bottom, middle, and top of the underground salt cavern cavity is distributed in descending order, it is determined that the mixed gas stored in the underground salt cavern exhibits stratification.

[0126] Optionally, the determining module 41 is further configured to, when the methane concentration at the bottom, middle and top of the underground salt cavern cavity is distributed from large to small, acquire the temperature difference characteristic curves along the composite optical cable measured by the distributed optical fiber temperature measurement system before and after heating; compare the temperature difference characteristic curves along the composite optical cable before and after heating; when the fluctuation amplitude of the temperature difference characteristic curve along the composite optical cable after heating exceeds the set fluctuation amplitude compared with the temperature difference characteristic curve before heating and a clear interface appears, determine that the mixed gas stored in the underground salt cavern has stratified.

[0127] Optionally, the mixing module 42 is used to inject mixed gas into the bottom of the underground salt cavern cavity or discharge mixed gas from the underground salt cavern cavity through a straight pipe, the straight pipe being arranged vertically within the underground salt cavern cavity.

[0128] Optionally, module 41 is also used to determine whether the stratification phenomenon has disappeared.

[0129] Correspondingly, the mixing module 42 is also used to stop mixing the mixed gas that has stratified when it is determined that the stratification phenomenon has disappeared.

[0130] In this embodiment, a safe storage device for mixed gas in underground salt caverns can be a computer, including: a processor; and a memory for storing executable instructions of the processor; wherein the processor is configured to execute the aforementioned safe storage method for mixed gas in underground salt caverns by executing the executable instructions. The memory and the processor can be connected via a bus. The storage unit may include a readable medium in the form of volatile memory units, such as random access memory (RAM) and / or cache memory units, and may further include read-only memory units (ROM). The computer also includes a display unit connected to the bus. The display unit can display information such as the aforementioned temperature difference characteristic curve.

[0131] A computer-readable storage medium having a computer program stored thereon, which, when executed by the processor, implements the aforementioned method for safe storage of mixed gas in underground salt caverns.

[0132] It should be noted that the underground salt cavern mixed gas safety storage device, method and system in this embodiment are based on the same inventive concept. For details on the function of the underground salt cavern mixed gas safety storage device, please refer to the embodiments of the underground salt cavern mixed gas safety storage method and system.

[0133] The above embodiments are merely exemplary, and those skilled in the art should understand that the methods and systems described in this invention are not limited to the specific embodiments described. Those skilled in the art, after considering the technical solutions of this invention, will readily conceive of other embodiments, which also fall within the scope of this invention's technical innovation. The scope of protection of this invention is specified in the claims.

Claims

1. A method for safe storage of mixed gas in underground salt caverns, characterized in that, The method for safely storing mixed gases in underground salt caverns includes: To determine whether the mixed gas stored in the underground salt cavern exhibits stratification, wherein the mixed gas is a mixture of helium and natural gas; When it is determined that the mixed gas stored in the underground salt cavern exhibits stratification, the stratified mixed gas is mixed to ensure that the mixed gas is uniformly mixed and stored in the underground salt cavern. The determination of whether the mixed gas stored in the underground salt cavern exhibits stratification includes: The methane concentration information detected by each laser sensor in the laser sensor group is obtained. The laser sensor group includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity. Based on the methane concentration information detected by each laser sensor in the laser sensor group, determine whether the methane concentration at the bottom, middle and top of the underground salt cavern is distributed in descending order; When the methane concentration at the bottom, middle, and top of the underground salt cavern is distributed from high to low, it is determined that the mixed gas stored in the underground salt cavern exhibits stratification.

2. The method for safe storage of mixed gas in underground salt caverns as described in claim 1, characterized in that, Before determining that the mixed gas stored in the underground salt cavern exhibits stratification, the method further includes: Obtain the temperature difference characteristic curves along the composite optical cable before and after heating, as measured by the distributed optical fiber temperature measurement system. Compare the temperature difference characteristic curves along the composite optical cable before and after heating; Accordingly, the determination that the mixed gas stored in the underground salt cavern exhibits stratification includes: When the temperature difference characteristic curve along the composite optical cable after heating exceeds the set fluctuation range compared to the temperature difference characteristic curve before heating, and a clear interface appears, it is determined that the mixed gas stored in the underground salt cavern has stratified.

3. The method for safe storage of mixed gas in underground salt caverns as described in claim 1, characterized in that, The mixing of the gas mixture exhibiting stratification includes: The mixed gas is injected into or discharged from the underground salt cavern cavity through a straight pipe, which is vertically arranged within the underground salt cavern cavity.

4. The method for safe storage of mixed gas in underground salt caverns as described in any one of claims 1-3, characterized in that, The method further includes: Determine whether the stratification phenomenon has disappeared; Once it is determined that the stratification phenomenon has disappeared, mixing of the gas mixture in which stratification occurred should be stopped.

5. A safe storage system for mixed gas in underground salt caverns, characterized in that, The underground salt cavern mixed gas safety storage system includes: a detection device, a mixing device, and a safety storage device; The detection device is used to detect whether the mixed gas stored in the underground salt cavern exhibits stratification, and to obtain information on the stratification phenomenon. The mixed gas is a mixture of helium and natural gas. The safe storage device is used to determine whether the mixed gas stored in the underground salt cavern has stratified according to the stratification information; when it is determined that the mixed gas stored in the underground salt cavern has stratified, the mixing device is used to mix the mixed gas that has stratified so that the mixed gas is uniformly mixed and stored in the underground salt cavern. The stratification information includes methane concentration information. The detection device includes a laser sensor array. The laser sensor group includes a bottom laser sensor, a middle laser sensor, and a top laser sensor. The bottom laser sensor is installed at the bottom of the underground salt cavern cavity, the middle laser sensor is installed in the middle of the underground salt cavern cavity, and the top laser sensor is installed at the top of the underground salt cavern cavity. Each laser sensor in the laser sensor group is used to detect the methane concentration and obtain the methane concentration information.

6. The underground salt cavern mixed gas safe storage system as described in claim 5, characterized in that, The information on the stratification phenomenon also includes temperature difference characteristic curves along the composite optical cable before and after heating, wherein the composite optical cable is vertically arranged within the underground salt cavern cavity. The detection device also includes a distributed fiber optic temperature measurement system. The distributed fiber optic temperature measurement system includes a distributed temperature sensor host, the composite optical cable, and a heating control module. The composite optical cable includes a multimode optical fiber and a heating wire. The multimode optical fiber is used to transmit photoelectric and temperature-sensitive signals, and the heating wire is used for heating. The distributed temperature sensing host is used to control the heating wire to heat through the heating control module, collect the photoelectric temperature-sensitive signals transmitted by the multimode optical fiber before and after heating, and calculate the temperature difference characteristic curves of the composite optical cable before and after heating based on the collected photoelectric temperature-sensitive signals transmitted by the multimode optical fiber before and after heating.

7. The underground salt cavern mixed gas safe storage system as described in claim 5 or 6, characterized in that, The mixing device includes a straight pipe that is vertically arranged within the underground salt cavern cavity.

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