JP2006214772A - Leakage detection method for high-pressure gas underground storage facility, and high-pressure gas underground storage facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage detection method which can perform leakage detection for the entire storage tank, embedded in the ground comprehensively and detect leakage of wide-ranging high-pressure gas, without being limited to specific kinds of high-pressure gases, and to provide a high-pressure gas underground storage facility. <P>SOLUTION: A perforated drainpipe 8 for collecting groundwater in the ground is installed reticulately on the entire periphery of the storage tank 21, which is embedded in the ground to store high-pressure gas therewithin. The storage tank 21 comprises an airtight material 5 for ensuring the airtightness of the inside of the storage tank 21 and a back-filling material 6, which is interposed between the airtight material 5 and the ground and in which cracks crossing the perforated drainpipe 8 occur comprehensively and separately. The temperature within the perforated drainpipe 8 is measured continuously, and the temperature distribution within the perforated drainpipe 8 is observed in a time series manner, to detect drop in the temperature. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leak detection method for a high-pressure gas underground storage facility that is constructed underground and stores high-pressure gas therein, and a high-pressure gas underground storage facility that includes equipment for performing the leak detection method.

  Conventionally, various methods have been used as leak detection methods in energy storage facilities such as gas holders and liquefied natural gas (LNG) tanks, and fluid flow conduits such as gas conduits and pipelines. For example, as a direct method, there are a gas concentration measurement method such as a gas detector or a non-destructive inspection method. Further, there are methods such as a gas leak test and a liquid leak test as detection of the leak position, and there is also a method based on acoustic characteristic measurement of the leak location.

  In recent years, measuring devices using optical fibers such as OTDR (Optical Time Domain Reflectometry) type thermometers and OFDR (Optical Frequency Domain Reflectometry) type thermometers that measure temperature distribution by measuring temperature and position are provided. Has been. For example, a heating element or cooling element arranged close to the optical fiber is arranged, a reference temperature distribution of the measurement target is measured in advance, and a temperature change caused by heat absorption or heating from the optical fiber accompanying an environmental change is detected. Measure. When this measuring apparatus is used as a leakage detection means, for example, a detection unit having a configuration in which an optical fiber is inserted into a cylindrical heating element is inserted into a pipe through which a fluid flows, and heat dissipation of the reference optical fiber is performed. The distribution is measured and the temperature of the optical fiber is constantly measured. When the pipe body breaks and the fluid in the pipe leaks, the fluid flow speed increases at the upstream side of the leaked part, the temperature of the optical fiber decreases, and the fluid flow speed decreases at the downstream side of the leaked part. The temperature of the optical fiber rises. Therefore, if the heat dissipation distribution of the optical fiber is measured, it is possible to detect at which location the leakage occurs (see, for example, Patent Document 1).

Also, in LNG storage facilities, etc., there is a leak detection method that uses the low temperature characteristics of LNG. For example, an optical fiber is installed in a heat insulating material installed outside the storage tank, and the temperature drop of this optical fiber is detected. There is a way to detect leaks. This is to detect the leakage by detecting the temperature drop around the storage tank because the temperature around the storage tank is lowered when the low temperature LNG leaks from the storage tank (see, for example, Patent Document 2). .
JP-A-5-107121 JP-A-9-323784

However, according to the conventional leak detection method described above, the gas concentration measurement method limits the space in which a gas detector or the like can be installed (for example, an access tunnel). It cannot be installed, and early detection may be difficult.
Also, in non-destructive inspection, gas leak test, liquid leak test, etc., it is necessary to inspect directly at the position where there is a possibility of leakage, and the inspection position is limited to the range where the inspector can enter, so the underground storage tank The outer periphery cannot be inspected, and it is difficult to always inspect.
In addition, in the method of detecting gas leakage based on acoustic characteristics, a sensor is installed on the inner wall surface of the storage tank, but it is difficult to detect leakage at a position away from the sensor, so detection covering the entire storage tank I can't. Furthermore, if a sensor is installed on the inner wall of the storage tank, the maintenance of the sensor will be performed using the time when the storage tank is opened, so maintenance opportunities are limited, and if the sensor is embedded, maintenance will be difficult. Become.

  Moreover, according to the leak detection method using the optical fiber as described in Patent Document 1, the inside of the storage tank for storing the high-pressure gas needs to ensure airtightness, and therefore cannot be frequently opened. There is a problem that the maintenance after the detection unit is once installed cannot be easily performed.

Moreover, according to the leak detection method using the optical fiber as described in Patent Document 2, the outside of the underground storage tank is surrounded by the ground such as the rock, so the installation space of the optical fiber is limited, and the entire storage tank is There is a problem that it is difficult to comprehensively detect leakage.
Moreover, it is limited to gas leak detection having temperature characteristics such as low temperature, and there is a problem that various high-pressure gases cannot be detected.

  The present invention has been made in consideration of the above-described conventional problems, and continuously detects the leakage of high-pressure gas, can be detected early when leakage occurs, and is buried in the ground. Leak detection method for high-pressure gas underground storage facilities that can detect leaks covering the entire storage tank and can detect a wide range of high-pressure gas leaks without being limited to a specific type of high-pressure gas It aims to provide a high-pressure gas underground storage facility. Moreover, it aims at providing the high pressure gas underground storage facility which can perform the maintenance of the location which detects leak easily.

  According to the first aspect of the present invention, a perforated drainage pipe for collecting groundwater in the ground is installed in a mesh pattern on the entire outer periphery of a storage tank embedded in the ground and storing high-pressure gas therein, and the storage tank At least an airtight material that secures airtightness inside the storage tank, and a backfilling material that is interposed between the airtight material and the ground and cracks that intersect with the perforated drainage pipes are dispersed throughout. In the leak detection method of the high-pressure gas underground storage facility that consists of the above, the temperature in the perforated drain pipe is continuously measured, and the temperature distribution in the perforated drain pipe is observed in time series to detect the temperature drop It is characterized by that.

  Due to such characteristics, when high-pressure gas leaks from the storage tank, the high-pressure gas leaked from the leaked portion of the airtight material flows into the cracks generated in the backfill material. Since the pressure in the perforated drain pipe intersecting with the crack is lower than the internal pressure of the storage tank for storing the high-pressure gas, the high-pressure gas leaking into the crack flows into the perforated drain pipe having a pressure lower than the internal pressure of the storage tank. When the high-pressure gas flows into the low-pressure perforated drain pipe, an adiabatic expansion phenomenon occurs, the gas volume expands, the gas temperature decreases, and the perforated drain pipe temperature decreases. That is, the presence or absence of leakage is detected by detecting a temperature drop in the perforated drain pipe, and the leak position is detected by detecting the position of the temperature drop.

  In the invention of claim 2, a perforated drainage pipe for collecting groundwater in the ground is installed in a mesh pattern on the entire outer periphery of the storage tank embedded in the ground and storing high-pressure gas therein, and the storage tank At least an airtight material that secures airtightness inside the storage tank, and a backfilling material that is interposed between the airtight material and the ground and cracks that intersect with the perforated drainage pipes are dispersed throughout. In a high-pressure gas underground storage facility consisting of: and at least the optical fiber temperature sensor installed in the perforated drainage pipe and the temperature of the installation location of the optical fiber temperature sensor to continuously measure the temperature in the perforated drainage pipe An optical fiber thermometer comprising a measurement unit for observing the temperature distribution in a time series is provided, and a temperature change in the perforated drain pipe is detected by the optical fiber thermometer.

  Due to such characteristics, when high-pressure gas leaks from the storage tank, the temperature in the perforated drainage pipe is lowered by an adiabatic expansion phenomenon as in the case of claim 1. By detecting this temperature drop by the measuring unit, the presence or absence of gas leakage is detected, and the leakage position is detected. For high-pressure gas that has a temperature difference from the temperature in the perforated drainage pipe, when the high-pressure gas leaks from the storage tank, the temperature changes even if the temperature drop due to adiabatic expansion is not significant, and whether there is leakage And the leak position are detected respectively.

  According to a third aspect of the present invention, in the high-pressure gas underground storage facility according to the second aspect, the optical fiber temperature measuring section is formed in a cable shape.

  Due to these features, when performing maintenance on the optical fiber temperature sensing unit, the cable-shaped optical fiber temperature sensing unit is pulled out from the end of the perforated drainage pipe and maintained outside the perforated drainage pipe. Reinserted into the perforated drainage pipe at the location.

  According to the high pressure gas underground storage facility leakage detection method and high pressure gas underground storage facility according to the present invention, in order to measure the temperature distribution of the installation location of the optical fiber temperature sensing portion in time series, the high pressure gas leakage is continuously detected. Can be detected. Moreover, since the temperature change in the perforated drain pipe is immediately detected by the measuring section, it can be detected at an early stage when leakage occurs. In addition, since the optical fiber temperature detection unit is appropriately disposed in a perforated drain pipe installed in a mesh shape around the entire outer periphery of the storage tank, leakage detection can be performed covering the entire storage tank. Further, if the leaked gas is a high-pressure gas, any high-pressure gas causes an adiabatic expansion phenomenon and a temperature drop occurs, so that a wide range of high-pressure gas leaks can be detected.

  Furthermore, the optical fiber temperature detector is formed in a cable shape so that when performing maintenance of the optical fiber temperature detector, the optical fiber temperature detector can be pulled out, so maintenance work such as inspection work or replacement or repair in the event of a failure. Can be easily performed.

  Hereinafter, embodiments of a leak detection method for a high-pressure gas underground storage facility and a high-pressure gas underground storage facility according to the present invention will be described with reference to the drawings.

First, the configuration of the high-pressure gas underground storage facility will be described.
FIG. 1 is a cross-sectional view of a high-pressure gas underground storage facility. As shown in FIG. 1, the cavity 1 is formed by excavating the rock mass A. The cavity 1 is connected to the ground surface via an access tunnel 2. The access tunnel 2 is configured such that an upper access tunnel 2 a connected to the upper portion of the cavity portion 1 and a lower access tunnel 2 b connected to the lower portion of the cavity portion 1 are joined on the way. Above the cavity 1, a top tunnel 3 is formed in the rock mass A, and the cavity 1 and the top tunnel 3 are connected via a shaft 4. The top tunnel 3 is connected to the access tunnel 2.

  A storage tank 21 for storing high-pressure gas is constructed in the cavity 1 in the rock mass A. The storage tank 21 includes a lining material 5 installed along the inner wall 1 a of the cavity portion 1, a backfilled concrete material 6 interposed between the outer peripheral surface of the lining material 5 and the inner wall 1 a of the cavity portion 1, and the outer periphery of the lining material 5. It is comprised from the buffer material 7 interposed between the surface and the back-filled concrete material 6 inner peripheral surface.

  The lining material 5 is a plate-like member that ensures the airtightness of the internal space of the storage tank 21. For example, a steel lining material or the like is used. Needless to say, a lining material other than steel may be used as long as airtightness can be ensured, for example, a resin film may be coated on a concrete inner surface.

  The backfill concrete material 6 is a reinforced concrete body for transmitting the internal pressure of the storage tank 21 to the bedrock A, arranges the reinforcing bars along the inner wall 1a of the cavity 1 and has a predetermined interval between the inner wall 1a of the cavity 1 After the lining material 5 is disposed by opening, concrete is placed between the lining material 5 and the inner wall 1a of the cavity 1. Since the internal pressure of the storage tank 21 is high, cracks 6a due to tensile stress occur in the backfilled concrete material 6. If the cracks 6a are excessively concentrated, local deformation of the lining material 5 is increased and the airtightness of the storage tank 21 is adversely affected. Therefore, the cracks 6a of the backfilled concrete material 6 are kept at an appropriate interval. The reinforcing bars in the back-filled concrete material 6 are arranged so that they are formed and dispersed throughout.

  The buffer material 7 relieves the impact and pressure at the time of concrete placement so that the lining material 5 is not deformed or damaged at the time of concrete placement of the backfill concrete material 6.

  FIG. 2 is a perspective view of the storage tank 21. As shown in FIG. 2, the outer periphery of the storage tank 21 has a crack C in the bedrock A when the internal pressure decreases during construction of a high-pressure gas underground storage facility where the internal pressure does not act on the storage tank 21 or during open inspection. A plurality of perforated drainage pipes 8 that collect groundwater in the bedrock A are installed in a mesh shape so that groundwater pressure (external water pressure) does not act. The perforated drainage pipe 8 is stretched over the entire outer peripheral surface, and the plurality of perforated drainage pipes 8 are connected to a water collecting pipe 9 piped along the outer circumference of the storage tank 21.

  FIG. 3 is a partially enlarged sectional view of the storage tank 21. As shown in FIG. 3, the perforated drainage pipe 8 is stretched over the entire outer periphery of the storage tank 21, and therefore the crack 6 a generated by being dispersed throughout the perforated drainage pipe 8 and the backfill concrete material 6 is described. They are crossing each other.

  FIG. 4 is an enlarged view of the perforated drain pipe 8. As shown in FIG. 3, the perforated drain pipe 8 is made of a pipe material in which a plurality of holes for taking in groundwater are provided on the outer peripheral surface. The perforated drainage pipe 8 may be a mesh pipe whose peripheral surface is formed in a mesh shape, and any pipe body having a configuration having a plurality of holes 8a on the peripheral surface may be used.

  FIG. 5 is a diagram illustrating an optical fiber thermometer 10 for detecting leakage of high-pressure gas in a high-pressure gas underground storage facility. As shown in FIGS. 1, 4, and 5, the optical fiber thermometer 10 includes a plurality of optical fiber temperature detectors 11 disposed in a plurality of perforated drain pipes 8, and an installation of the optical fiber temperature detectors 11. It comprises a measuring unit 12 that measures the temperature distribution of the place in time series, and an optical fiber connecting unit 13 that connects the optical fiber temperature measuring unit 11 and the measuring unit 12.

  The optical fiber temperature measuring unit 11 is composed of a well-known optical fiber 14, and a perforated drainage pipe at a predetermined position among the plurality of perforated drainage pipes 8 so as to be stretched around the entire outer peripheral surface of the storage tank 21. 8 is inserted. The optical fiber 14 is a cable having a tensile strength that does not break when pulled, and is coated with a coating material 14a having excellent thermal conductivity. The measuring unit 12 is arranged in the top tunnel 3, and a connecting pipe 15 extending from the shaft 4 to the top tunnel 3 is provided between the measuring unit 12 and the water collecting pipe 9 on the top side of the storage tank 21. It is piped. The optical fiber connecting portion 13 has a configuration in which the optical fibers 14 constituting the optical fiber temperature detecting portion 11 are bundled on the top side of the storage tank 21, and is inserted into the water collecting pipe 9 and the connecting pipe 15. In addition, the connection pipe 15 and the optical fiber connection part 13 may be extended to the ground, and the measurement part 12 may be installed on the ground.

  In addition, the shape, distribution, installation method, etc. of the hole 8a of the perforated drainage pipe 8 are designed so as not to hinder the drainage function and inflow / collection of leaked high-pressure gas in consideration of workability in the backfilled concrete. . For example, if there is no hole 8a at a location intersecting with the crack 6a, the leaked high-pressure gas will not flow into the perforated drain pipe 8, so that the hole 8a is always formed at a location intersecting with the crack 6a. It is necessary that a plurality of the drain pipes 8 are uniformly formed on the outer periphery of the drain pipe 8, and it is preferable that the drain pipe 8 be formed so as to intersect with the holes 8a regardless of the cross section.

  On the other hand, as shown in FIG. 1, in the lower access tunnel 2b, groundwater that has flowed into the perforated drain pipe 8 and collected in the water collection pipe 9 is collected into the water collection installed in the lower access tunnel 2b. A first drain main pipe 16 that feeds water into the pit 18 is provided. One end of the first drain main pipe 16 is connected to the water collecting pipe 9 on the bottom side of the storage tank 21, and the other end is disposed in the water collecting pit 18. 17 is interposed.

  Further, a second drain main 19 for discharging the groundwater collected in the water collecting pit 18 to the ground is provided in the access tunnel 2. The second drain main 19 is routed from the water collection pit 18 through the access tunnel 2 to the surface of the ground, and the second drain main 19 receives the groundwater in the water collection pit 18. A drainage pump 20 for pumping is interposed.

  Next, a method for detecting leakage of high-pressure gas in the high-pressure gas underground storage facility having the above-described configuration will be described.

First, during the normal operation period when the high-pressure gas underground storage facility is not under construction or when the internal pressure is reduced, the drainage pump 20 is stopped and the drainage function for discharging spring water (groundwater) from the rock mass A is not operated. As a result, the inside of the perforated drainage pipe 8 stretched around the entire outer periphery of the storage tank 21 has almost no groundwater flow, the heat flow is close to a steady state, and is maintained at a constant temperature state.
In addition, the installation path of the optical fiber temperature measuring part 11 disposed in the perforated drain pipe 8 is determined in advance and installed, and the position of the outer periphery of the storage tank 21 can be specified by appropriately determining the distance from the reference position. .

  Next, during the operation period of the high-pressure gas underground storage facility, the temperature in the perforated drain pipe 8 is continuously measured, and the temperature distribution in the perforated drain pipe 8 is observed in time series by the measuring unit 12. As described above, since the temperature inside the perforated drainage pipe 8 is kept constant, when the high-pressure gas is not leaked, the temperature distribution measured by the measuring unit 12 is constant. The value of the temperature distribution becomes the reference temperature distribution.

  When the high-pressure gas leaks from the storage tank 21, the high-pressure gas leaked from the leakage portion of the lining material 5 flows into the crack 6 a generated in the backfilled concrete material 6. Since the pressure in the perforated drain pipe 8 intersecting with the crack 6a is significantly lower than the internal pressure of the storage tank 21 for storing the high-pressure gas, the high-pressure gas leaked into the crack 6a is lower than the internal pressure of the storage tank 21. It flows into the hole drain pipe 8. When the high-pressure gas flows into the low-pressure perforated drain pipe 8, a phenomenon of adiabatic expansion occurs, the gas volume expands and the temperature of the gas decreases, and the temperature inside the perforated drain pipe 8 decreases. . This temperature drop is detected by the measurement unit 12 that observes the temperature distribution in the perforated drain pipe 8 in time series, and the presence or absence of leakage is detected. Moreover, the position of the temperature fall part in the outer periphery of the storage tank 21 is specified according to the distance from the reference position determined appropriately, and the leakage position is specified three-dimensionally.

  According to the leakage detection method and the high-pressure gas underground storage facility having the above-described configuration, the high-pressure gas leakage is continuously measured in order to measure the temperature distribution at the installation location of the optical fiber temperature detection unit 11 in time series. Can be detected automatically. Moreover, since the temperature change in the perforated drainage pipe 8 is immediately detected by the measuring unit 12, it can be detected at an early stage when leakage of high-pressure gas occurs. In addition, since the optical fiber temperature detector is appropriately disposed in the perforated drain pipe 8 installed in a mesh shape around the entire outer periphery of the storage tank 21, leakage detection can be performed covering the entire storage tank. Further, if the leaked gas is a high-pressure gas, any high-pressure gas causes an adiabatic expansion phenomenon and a temperature drop occurs, so that a wide range of high-pressure gas leaks can be detected.

  Furthermore, since the optical fiber temperature detection unit 11 is formed in a cable shape, when performing maintenance on the optical fiber temperature detection unit 11, the optical fiber temperature detection unit 11 is pulled out from the perforated drainage pipe 8 for inspection work or replacement at the time of failure. Can be inserted into the perforated drain pipe 8 after the inspection or the like is completed, and the maintenance of the optical fiber thermometer 10 can be easily performed.

Even if the temperature drop due to the adiabatic expansion phenomenon is not significant, if there is a temperature difference between the storage temperature of the high-pressure gas stored in the storage tank 21 and the temperature in the perforated drainage pipe 8 at normal times Temperature change can be detected, and leakage can be detected.
Further, by adjusting the interval between the perforated drainage pipes 8 where the optical fiber temperature measuring unit 11 is installed, the number of installed side lines of the optical fiber 14, and the installation route, the accuracy of specifying the leakage position can be improved.

  As mentioned above, although the leak detection method of the high-pressure gas underground storage facility and the embodiment of the high-pressure gas underground storage facility according to the present invention have been described, the present invention is not limited to the above-described embodiment, and departs from the gist thereof. It is possible to change appropriately within the range not to be. For example, in the above-described embodiment, the optical fiber temperature detection unit 11 is disposed uniformly on the whole so as to be stretched around the entire outer peripheral surface of the storage tank 21, but the present invention is particularly effective for leakage. You may arrange | position an optical fiber temperature-sensing part densely in the place with a possibility.

In the above-described embodiment, the high-pressure gas underground storage facility constructed in the bedrock A is described. However, the present invention is, of course, a high-pressure gas underground storage facility constructed in other ground. Also good.
In the above-described embodiment, the temperature in the perforated drain pipe 8 is measured using the optical fiber 14, but the leak detection method for the high-pressure gas underground storage facility according to the present invention measures the temperature using the optical fiber. You may measure the temperature in a perforated drain pipe by methods other than.
In the above-described embodiment, the optical fiber temperature detector 11 is formed in the shape of a cable. However, the present invention is based on the assumption that the optical fiber temperature detector 11 is not pulled out, except for the cable-shaped optical fiber temperature detector. For example, a bar-shaped optical fiber temperature detector may be used.

It is sectional drawing of the high pressure gas underground storage facility for demonstrating embodiment which concerns on this invention. It is a perspective view of the storage tank for demonstrating embodiment which concerns on this invention. It is a fragmentary sectional view for describing an embodiment concerning the present invention. It is a perspective view of a perforated drain pipe for explaining an embodiment concerning the present invention. It is a figure showing the optical fiber thermometer for demonstrating embodiment which concerns on this invention.

Explanation of symbols

5 Lining material (airtight material)
6a Crack 6 Backfilling concrete material (backfilling material)
8 Perforated drain pipe 10 Optical fiber thermometer 11 Optical fiber thermometer 12 Measuring unit 21 Storage tank A Rock (ground)

Claims (3)

A perforated drain pipe that collects groundwater in the ground is installed in a mesh pattern on the entire outer periphery of the storage tank that is buried in the ground and stores high pressure gas inside, and the storage tank is at least airtight inside the storage tank. A high-pressure gas composed of an air-tight material that secures water and a back-filling material that is interposed between the air-tight material and the ground and that has cracks that intersect with the perforated drainage pipe as a whole. In the leak detection method for underground storage facilities,
A leak detection method for a high-pressure gas underground storage facility, wherein the temperature in a perforated drain pipe is continuously measured, and the temperature distribution in the perforated drain pipe is observed in time series to detect a temperature drop. A perforated drain pipe that collects groundwater in the ground is installed in a mesh pattern on the entire outer periphery of the storage tank that is buried in the ground and stores high pressure gas inside, and the storage tank is at least airtight inside the storage tank. A high-pressure gas composed of an air-tight material that secures water and a back-filling material that is interposed between the air-tight material and the ground and that has cracks that intersect with the perforated drainage pipe as a whole. In underground storage facilities,
At least an optical fiber thermometer disposed in the perforated drain pipe, and a measuring section that continuously measures the temperature of the installation location of the optical fiber thermometer and observes the temperature distribution in the perforated drain pipe in time series An optical fiber thermometer consisting of
A high-pressure gas underground storage facility that detects temperature changes in perforated drain pipes using an optical fiber thermometer. In the high-pressure gas underground storage facility according to claim 2,
A high-pressure gas underground storage facility characterized in that the optical fiber temperature measuring part is formed in a cable shape.

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