JP2015200525A - Gas monitor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement method for measuring a gas flux evaporated from a ground or a rock layer and a gas concentration in a peripheral front layer surface atmosphere over a long period, a gas monitor device, and an alarm system for a gas leakage.SOLUTION: A gas monitor device includes: a bottom surface part opened to a ground of a detection object; an exhaust port 2b for exhausting the air; an intake port 2c for the intake air; opening/closing valves 5, 6a, and 6b arranged very nearby the exhaust port 2b and the intake port 2c; ventilation control means for ventilating the air; an exhaust chamber externally separated and exhausting the evaporated gas; and an intake chamber externally separated and taking-in a surface layer atmospheric air. The gas monitor device further collects a detection object gas evaporated from the ground or the rock layer via the opened bottom surface part and includes an internal circulation mode for agitating and mixing the evaporated gas by an air flow induced by the operation of the ventilation control means by simultaneously closing the exhaust opening/closing valves 6a, 6b and the intake opening/closing valve 5.

Description

  The present invention relates to an apparatus for alternately measuring a gas flux that flows out or dissipates per unit area and unit time from the surface of a soil or rock layer and the concentration of the gas in the surrounding surface atmosphere, and particularly in an apparatus such as a measurement chamber. The present invention relates to a measurement method, a gas monitor device, and an alarm system for reducing the influence of condensation and freezing in a room by ventilation, and performing stable and reliable measurement with low power for a long time at an installation position.

The present invention provides a long-term monitor of unit area such as carbon dioxide and methane gas that flows or diffuses from the surface of the soil or rock layer to the surface, gas flux that is the amount of radiation per unit time, and the concentration of the gas in the surrounding surface atmosphere. In addition to collecting gas fluxes such as carbon dioxide and methane gas emitted from the soil or rock layer at that location and background data of the gas concentration in the atmosphere under natural conditions, carbon dioxide, oil and natural gas, etc. The present invention relates to a structure and a measuring method of a monitor device for detecting gas emission leaked from an underground reservoir in which gas is stored into the atmosphere, and an alarm system related to abnormality of the gas emission based on statistical data of background data.

A large amount of carbon dioxide, a global warming gas, is emitted into the atmosphere from thermal power plants, ironworks, and refineries that use fossil fuels such as coal, oil, and natural gas. In addition, methane gas having a much greater global warming potential than carbon dioxide is released into the atmosphere from coal, oil and natural gas mining areas, their transport areas, and agricultural areas. In order to suppress global warming, it is necessary to reduce the amount of greenhouse gases such as carbon dioxide and methane gas emitted from these offices and regions into the atmosphere. In recent years, carbon dioxide recovery and storage technology (abbreviated as CCS) as a technology for separating carbon dioxide and storing it underground is being implemented not only in Japan but also around the world. Underground storage of carbon dioxide on a commercial scale is an oil / natural gas or aquifer filled with 15-30% of the volume of carbon dioxide separated from the gas discharged in the industrial activities described above. For example, it is press-fitted into an underground reservoir such as 10 to 1 million tons / year for storage. At this time, a reservoir with an upper layer with a low fluid permeability seal layer is selected as a layer for underground storage, but it was injected and stored through cracks in fine rocks that could not be found by geological exploration. The probability that some of the carbon dioxide leaks to the surface as gas is not zero.

In the US, where shale gas development is in progress, cracks in the seal layer, which may be caused by inappropriate hydraulic fracturing, have occurred, and methane gas leaks to the surface of the mining area.

For this reason, if residents living in the surrounding area or agriculture, forestry, fishery, etc. are operated, the safety of the surrounding environment cannot be ensured, resulting in great damage and confusion in the community. However, there is data that the amount of carbon dioxide released into the atmosphere from soil or rocks such as cultivated land in the world is 7 to 8 times the amount of carbon dioxide emitted by human activities. In addition, gas fluxes such as carbon dioxide released from the soil or rock surface to the atmosphere are strongly affected by climate change such as local temperature and precipitation. Therefore, in order to determine whether carbon dioxide or methane gas is leaking, it is essential to have a gas flux measurement method and monitoring device that can be clearly distinguished in light of the natural gas emission situation, as well as from soil or rock. Long-term measurement data related to gas flux is indispensable, and it is judged to be important basic data in setting the alarm level for the leakage amount.

Currently, carbon dioxide leakage detection methods include: a) measurement of carbon dioxide isotope in soil or rock or rock, b) measurement of carbon dioxide concentration in surface air, c) carbon dioxide in surface soil or rock Concentration measurement, d) measurement of carbon dioxide gas flux from soil or rock or rock to the atmosphere. In the method of measuring the isotope of carbon dioxide in a), there is no clear difference in the isotope ratio between the carbon dioxide recovered from the combustion exhaust gas of fossil fuel and the natural bacteria such as in the soil, and it is decisive. It is not a leak detection method. The measurement of carbon dioxide concentration in the surface air of b) has a simple structure and has few problems in long-term monitoring, but it is highly affected by wind on the ground surface, exhaust gas, exhalation of animals, etc., and the reliability at the time of leak judgment is low. In the measurement of carbon dioxide concentration in soil or rock in c), the accuracy of detection of the presence or absence of leaked gas is high, but there is no unique relationship between the gas concentration and the amount of leak, and the water vapor contained in the soil or rock There are problems in maintaining accuracy for a long time, such as measures against condensation or moisture freezing in winter. In the method of measuring gas flux d), it is possible to directly measure gas emission amount data per unit time such as leaked carbon dioxide, so it is highly reliable as a judgment criterion for leakage, such as US LI-COR Is the most suitable method for actual field measurement.

There are roughly two types of methods for measuring gas flux from the soil or rock layer that are judged to be the most suitable methods. The first method is called a concentration gradient measurement method, which measures carbon dioxide concentrations (ppm) at different depths in soil or rocks, etc., and uses the concentration difference (ppm) and distance (m) to determine the concentration gradient ( ppm / m), and the soil or rock gas flux (mL / m ² / s) is obtained by multiplying the effective gas diffusion coefficient (m ² / s) in the soil or rock or rock. This method has problems of failure due to selection of appropriate depth, estimation error of effective gas diffusion coefficient, and influence of moisture in soil or rock.

The second gas flux measurement method described above is also called a chamber method, which uses a chamber that is a container for receiving gas such as carbon dioxide emitted from the contact surface between the soil or rock layer and the atmosphere. The stationary chamber method and the unsteady chamber method are classified. The steady chamber method multiplies two gas concentration differences (ppm) and air flow rate (m ³ / s), such as two carbon dioxides before and after the air is circulated from the atmosphere into the chamber and released to the atmosphere. since the determined by dividing the chamber bottom of the opening area S (m ²⁾ Te, it is necessary to accurately measure the three data at a minimum, expensive and and required power amount production costs including the precise plurality of sensors also large. On the other hand, the unsteady chamber method measures the time gradient (ppm / s) of the carbon dioxide concentration in the chamber, multiplies the chamber volume V (m ³ ), divides it by the open area S (m ² ), and gives the gas flux (mL / M ² / s) is measured. The measurement by the unsteady chamber method is simple, but it is necessary to mechanically open the chamber after one measurement is completed and expose the air in the chamber to the atmosphere to reset it. There is a problem in power supply to realize long-term measurement implementation at the construction and installation position. However, the unsteady chamber method can solve the problems related to the dew condensation and freezing of water advected or transpiration from the soil or rock layer by replacing the air in the chamber.

As described above, it cannot be said that a reliable method has been established to continuously measure gas flux from the soil or rock layer surface such as carbon dioxide for a long period of time at a fixed interval. Devise measurement methods to increase social acceptability, which is indispensable for promoting the production of unconventional natural gas such as CCS and shale gas, which are expected as effective technologies There is a need to develop a gas monitor and alarm system.

Therefore, for example, in Japanese Patent Application Laid-Open No. 2011-296215 (Patent Document 1), the air inside the measurement chamber is guided to a gas cleaning bottle of an alkaline solution, carbon dioxide is absorbed, and the air inside the measurement chamber is brought into a state close to natural air. A way to return is presented. However, the concentration inside the measurement chamber is complicated in order to accurately control it by providing different air circulation circuits, and requires a lot of electric power, resulting in high cost. Furthermore, since a gas cleaning bottle containing an alkaline solution is used, it is difficult to cope with long-term monitoring and low-temperature environments, and it is also difficult to cope with problems caused by condensation inside the measurement chamber due to the addition of moisture in the cleaning bottle.

In Japanese Patent Laid-Open No. 2008-203124 (Patent Document 2), in order to discriminate between carbon dioxide gas generated by biological metabolism and carbon dioxide gas leaked to the ground by carbon dioxide injected underground, the oxygen concentration in the measurement chamber is set. Evaluate the amount of carbon dioxide gas leaked from the underground reservoir to the ground surface by calculating the oxygen consumption and carbon dioxide emission due to biological metabolism by measuring accurately and calculating the difference in the balance of carbon dioxide gas amount Propose that.

However, as a result of long-term measurement of the amount of carbon dioxide gas flux at the Ito Campus of Kyushu University, the inventors have found that about 0.5-6 liters of carbon dioxide per day is diffused from the soil surface to the atmosphere. It is revealed. These carbon dioxides are produced by the decomposition of hydrocarbon components in the soil mainly due to microbial activity, and it has been confirmed that they also change due to seasonal variations in soil temperature and moisture contained in the soil. For this reason, when carbon dioxide released from the soil to the atmosphere by microbial activity is mixed with carbon dioxide leaked from the underground reservoir, it is substantially difficult to distinguish them. In addition, when the atmosphere contains carbon dioxide at a concentration of about 400 ppm, the carbon dioxide leaked from the underground reservoir is mixed with the soil or rock atmosphere gas and released to the surface at a low concentration of several percent or less. It is difficult to clearly define the source of carbon dioxide emissions.

JP 2011-296215 A JP 2008-203124 A

In areas where underground storage such as carbon dioxide and methane gas is carried out, and oil and natural gas, especially shale gas development areas, the gas flux released to the surface and the concentration of the gas in the surface atmosphere are continuously reduced with low power. In order to ensure the safety and security of the residents, long-term measurements, annual fluctuation patterns as background data of the natural world are established, and the presence or absence of carbon dioxide and methane gas leakage from the surface of the earth is monitored. is there. However, it must be a device that can perform unattended measurements over a long period of time even in areas where social infrastructure such as power supply is not sufficiently established.

However, the conventional measurement of gas flux from soil or rock must be performed batch-wise by the unsteady chamber method or by multiplying sensor output such as high-precision gas concentration and air flow with an expensive monitoring device. Therefore, it is not suitable for monitoring at low cost while maintaining long-term reliability at a fixed position. Also, in long-term use, moisture transpiration from the soil or rock layer is difficult to use for a long time because the measurement function deteriorates due to condensation or freezing in the air supply means inside the measuring device, gas sensor or external gas concentration sensor It is.

In addition, in an apparatus using the unsteady chamber method, it is necessary to provide a mechanical measurement chamber opening mechanism with a large driving power in order to reset the air in the measurement chamber to the atmosphere. Therefore, it is not suitable as a simple long-term monitoring device that operates at low power even in an area where social infrastructure is not established.

Furthermore, there has been no gas monitoring device that can alternately measure the gas flux emitted from the soil or rock layer and the gas concentration in the surface atmosphere with a single gas concentration sensor.

  The present invention has been made to solve the above-mentioned problems. The gas flux emitted from the soil or the rock layer is simply installed at a low cost for a long period of time without manual intervention after the installation. A gas monitoring device that realizes a measurement method and structure for measuring the gas flux emitted from the surface of the soil or rock layer and the concentration of the gas in the surrounding surface layer atmosphere, which can be measured, and abnormal gas emission The purpose is to provide related alarm systems.

The gas monitor device disclosed in claim 1 of the present application has a function of measuring the flux of the detection target gas diffused from the surface of the soil or rock layer, and is a bottom surface portion opened to the detection target soil or rock layer. A measurement chamber having an exhaust, an exhaust port for exhaust, an intake port for intake, an on-off valve provided in the vicinity of the exhaust port and the intake port, and a ventilation control means for performing ventilation And an exhaust chamber that is isolated from the outside and exhausts the diffused gas, and an intake chamber that is isolated from the diffused gas and enters the surface atmosphere (outside air), through an open bottom surface at the bottom of the measurement chamber The emitted gas entering from the soil or rock layer is collected, and the opening and closing valves provided at the exhaust port and the intake port are closed, and the emitted gas is stirred and mixed by the air flow of the ventilation control means. Realizes internal circulation mode, communicates with the outside air through the exhaust port and the exhaust chamber, and simultaneously communicates from the outside air through the inlet chamber and the inlet port, and introduces the outside air through the inlet port And a measurement chamber that realizes two types of operation modes of a ventilation mode for exhausting the collected air containing the emitted gas to the outside, and a detection target in the two types of operation modes. Gas concentration detection means for measuring the gas concentration of the internal circulation mode in the measurement chamber, the gas concentration detection means for measuring the gas flux from the calculated value of the initial gas concentration time gradient in the internal circulation mode, in the ventilation mode The gas concentration in the surrounding surface atmosphere is measured alternately.
In addition, the trench may be given with respect to the said soil or rock layer surface as a rain countermeasure. Further, the gas concentration detection means may be a means (for example, a gas concentration sensor) for directly measuring the gas concentration inside the measurement chamber, and the air inside the measurement chamber is connected to the outside of the measurement chamber. In order to supply as a sample to the gas concentration sensor installed in the apparatus, a means for sending the gas concentration sensor outside the measurement chamber may be used.

  That is, in a measurement chamber that is placed in contact with the soil or rock layer to be detected and has a closed communication path with the atmosphere, the radiation is emitted from the soil through the bottom bottom surface of the measurement chamber that is opened in contact with the soil or rock layer. The gas is collected in the measurement chamber, the gas concentration detection means measures the gas concentration to be detected for a certain time, and the gas flux is measured from the calculated value of the initial gas concentration time gradient. After that, the air in the measurement chamber containing the diffused gas is discharged to the atmosphere through the exhaust port and the exhaust chamber, and at the same time, the inlet chamber and the inlet port (and the inlet cylinder if necessary) communicating with the atmosphere are provided. Then, the inside of the measurement chamber is ventilated by sucking the surface layer atmosphere, and the gas concentration of the air in the measurement chamber that is the same as the surface layer atmosphere is measured by the gas concentration detection means.

By the series of operations described above, the gas flux flowing out or released from the soil or rock layer and the gas concentration in the surface atmosphere are alternately measured by the gas concentration detecting means.

As described above, according to the gas monitoring device disclosed in the present application, after the detection gas in the measurement chamber is detected by the gas concentration detection unit, fresh outside air in the atmosphere is transferred from the inlet chamber to the measurement chamber. While being introduced, air containing the diffused gas and water vapor in the measurement chamber is exhausted from the exhaust chamber to the outside.

From the above, air mixed with gas in the measurement chamber is discharged, and ventilation with fresh air from the atmosphere is performed at the same time. After measuring the flux of the emitted gas, mechanical opening work for ventilation is performed. The flux of the detection target gas diffused from the surface of the soil or rock layer can be stably measured at low cost and low power for a long period of time.

In addition, since the gas monitoring device disclosed in the present application includes the ventilation control unit, the air flow generated in the measurement chamber by the ventilation control unit promotes the uniformization of the diffused gas concentration. It is possible to accurately measure the gas flux as the detection target.

  The gas monitor device disclosed in claim 2 is an internal circulation mode in which the measurement chamber is closed by the on-off valve, and the diffused gas diffused from below is retained in the measurement chamber and stirred and mixed, and the measurement Air containing the diffused gas in the chamber is exhausted to the outside through the on-off valve, the exhaust port, and the exhaust chamber, and the surface air is supplied to the measurement chamber through the inlet chamber, the inlet port, and the on-off valve. And a ventilation control means for realizing a ventilation mode by the on-off valve for exchanging the internal air of the measurement chamber and excluding the diffused gas and water vapor diffused from underground.

  In the gas monitor disclosed in claim 3 of the present application, the ventilation control means is disposed between the inlet and the gas concentration detecting means inside the measurement chamber, and the exhaust outlet of the measurement chamber is connected to the ventilation. An opening / closing valve disposed on the downstream side of the air flow of the control means, wherein the inlet is formed by an on-off valve that is opened by a slight negative pressure of the air flow, and the opening / closing is opened by the wind pressure of the air flow. The measuring chamber having a mechanism formed by a valve is provided.

That is, in the gas monitoring device disclosed in the present application, if necessary, the ventilation control means is disposed between the inlet of the measurement chamber and the gas concentration detecting means, and the inlet is slightly negative. It is formed by an on-off valve that is open at a pressure (for example, about 1 mm water column), and a discharge port disposed on the downstream side of the air flow in the measurement chamber has a slight air pressure (for example, It can be formed with an on-off valve that opens in about 1 mm water column). Thus, according to the gas monitor device disclosed in the present application, the ventilation control means is disposed at the connection portion between the measurement chamber and the exhaust chamber, and at the connection portion between the measurement chamber and the inlet cylinder, The measurement chamber is ventilated so that the incoming airflow is generally downward and the exhaust airflow is generally horizontal (radial direction). That is, the inlet and outlet are automatically opened and closed by the mechanical action of the air flow of the measurement chamber, and the air containing the diffused gas and water vapor inside the measurement chamber and the outside air are not controlled by external control. Ventilation can be realized with a simple structure with lower power, and the gas flux and gas concentration in the surface air can be measured in a short time.

  In the gas monitor disclosed in claim 4 of the present application, the measurement chamber is formed of a semicircular sphere having a circular lower opening, and the inlet is disposed at the top of the semispherical sphere. An exhaust port is disposed in the vicinity of the outer periphery of the semispherical sphere. As described above, the measurement chamber is formed of a semispherical sphere having a circular lower opening portion, and the inlet is disposed at the top of the semispherical sphere, and the vicinity of the outer periphery of the semispherical sphere. Since the exhaust port is disposed in the air outlet, the air flow in the measurement chamber is easily made uniform, and the gas flux and the gas concentration in the surrounding surface air can be measured in a shorter time.

That is, in the gas monitor device disclosed in the present application, the measurement chamber is formed as a semicircular sphere having a circular lower opening portion as necessary, and the inlet is disposed at the top of the semispherical sphere. In addition, a discharge port is disposed in the vicinity of the outer periphery of the semispherical sphere. As described above, according to the gas monitoring device disclosed in the present application, the measurement chamber is formed of, for example, a semicircular sphere having a circular lower opening portion, and the inlet is disposed at the top of the semispherical sphere. In addition, since the discharge port is disposed in the vicinity of the outer periphery of the hemispherical body, the airflow including the diffused gas from the soil or the like in the measurement chamber is uniformed more quickly without unevenness, With higher efficiency, the flux of the emitted gas can be measured in a short time.

  The gas monitoring device disclosed in claim 5 of the present invention is a method for measuring data under natural conditions in the gas flux diffused from the soil or rock layer measured by the gas concentration detection means and the gas concentration in the surrounding surface atmosphere. A risk factor is set for the background probability density distribution obtained by statistically processing the fluctuation value, an abnormality in gas emission from the soil or rock layer is judged, and an alarm is output. Thus, based on the measurement data by the gas concentration detection means, the gas flux from the soil or rock layer or the surface layer is set by setting the risk factor for the probability density distribution which is the statistical value of the fluctuation data under natural conditions. Since the abnormality of the gas concentration in the atmosphere is judged and an alarm is output, an alarm is promptly issued when an abnormality occurs, and the danger caused by the emitted gas can be avoided.

The gas monitor device for measuring the gas flux on the surface of the soil or rock layer of the present invention and the concentration of the gas in the surrounding surface atmosphere is a surrounding surface atmosphere (outside air) in a measurement chamber placed in contact with the surface soil or rock. Inlet and outlet valves that allow air to enter, and a mechanical on-off valve that is operated by electromagnetic force at multiple exhaust ports at appropriate positions for exhausting the air inside the measurement chamber, or opens and closes depending on the state of internal air flow An internal circulation mode that has a film on-off valve and that closes all the on-off valves to keep the gas emitted from the surface of the soil or rock surface inside the measurement chamber and at the same time agitates and mixes to a uniform emission gas concentration by the ventilation control means Open all the open / close valves to introduce fresh outside air from the surrounding surface layer atmosphere into the measurement chamber and exhaust the air in the measurement chamber containing the emitted gas to the outside. The ventilation mode to be switched is switched at an appropriate time cycle, and in each mode, the gas is detected from the soil or rock layer based on the measurement data of the gas concentration in the air in the measurement chamber by one gas concentration detection means provided in the chamber. It is characterized by a method for alternately measuring the gas flux and the gas concentration in the surface layer atmosphere, a gas monitoring device, and an alarm system for judging abnormalities in the emitted gas.

According to the gas monitor apparatus and the measurement method having a measurement chamber having a function capable of switching between the ventilation mode and the internal circulation mode of the present invention, the gas flux emitted from the surface of the soil or the rock layer and the surrounding surface atmosphere The gas concentration can be measured continuously over a long period of time with a time cycle of about 30 seconds or more.

In particular, an internal circulation mode that collects gas released from the surface of the soil or rock layer and stirs it to a uniform gas concentration and fresh outside air in the surrounding surface layer atmosphere are introduced into the measurement chamber, and air and water vapor containing the released gas are introduced. By switching between the two modes of the ventilation mode to be discharged with a time cycle set to about 30 seconds or more, water vapor that evaporates from the lower soil or rock layer is periodically discharged into the measurement chamber in the ventilation mode, and the gas monitor Since heat transfer is performed so that the temperature of the device and its internal temperature are the same as the ambient surface air temperature, it is possible to prevent condensation and freezing on the inner wall of the monitor device and the sensing part of the gas concentration sensor. The soundness and life of gas concentration detection means such as sensors can be extended.

In addition, according to the present invention, by measuring the gas flux from the surface of the soil or rock surface and simultaneously measuring the gas concentration in the surface atmosphere in a cycle set to about 30 seconds or more, there is no gas leakage with high reliability. Can be measured continuously for a long period of time, and can also be used as calibration data for the gas concentration sensor or as soundness determination data based on the measured gas concentration data in the atmosphere. For example, using the fact that the carbon dioxide gas concentration in the atmosphere is usually 340 ppm to 400 ppm, it is possible to adjust a coefficient for converting from output to concentration or an output value of zero concentration. However, since the measurement method of the present invention is a method for obtaining the gas flux based on the time gradient of the concentration data, not the absolute concentration of the gas, the accuracy drop due to the deviation of the gas concentration sensor output is extremely small.

Furthermore, it is sufficient to provide at least one type of the gas concentration sensor to be detected. For example, by providing a plurality of gas concentration detection means such as carbon dioxide and methane, a plurality of flue gas fluxes and the atmosphere Concentration can be measured simultaneously. A hydrogen sensor can also be used when hydrogen gas or the like is contained in carbon dioxide separated and collected for underground storage. By installing a plurality of the same gas concentration sensors in the measurement chamber, it is possible to construct a backup system against sensor failure. In addition, the gas concentration detection means may be configured to directly measure the gas concentration inside the measurement chamber and directly measure with the gas concentration sensor, but may be configured to attract and measure the air in the measurement chamber to the outside.

As described above, according to the present invention, the measurement chamber has a simple mechanism for measuring the gas flux released from the underground soil layer or rock surface layer of global warming gas such as carbon dioxide and methane into the atmosphere. Measurement method, gas monitor device, and leak detection for realizing long-term measurement of gas flux and atmospheric gas concentration of the gas at low cost and low power while realizing ventilation mode and internal circulation mode. A system can be provided.

Measurement status of gas flux from soil in internal circulation mode in chamber It is a figure which shows the measurement condition of the gas flux from the soil in the ventilation mode in a chamber. It is a figure which shows the whole system which controls a ventilation mode and an internal circulation mode by the valve function of the air intake / exhaust port using a mechanical type or electromagnetic, and outputs an alarm. The solid line arrows in the figure represent the control line of the on-off valve, the power supply line, and the information line for the alarm circuit, and the broken line arrows represent the power supply to the gas concentration sensor and the measurement signal line. It is a figure which shows the Example which implement | achieved ventilation mode by the valve function of the air intake / exhaust port using a fan and a film. It is a figure which shows the Example which ventilation mode was implement | achieved by the valve function of the air intake / exhaust port using a fan and a film. It is a figure which shows the example of a measurement of the time change curve of the carbon dioxide concentration inside the chamber in the actual field. It is the figure which showed the measurement result about the relationship between the soil moisture content measured in the test field of Kyushu University Ito campus, soil temperature, and a carbon dioxide gas flux. As part of the data, the measurement results in Edmonton, Canada are included.

(First embodiment)
Hereinafter, the form for implementing this invention is shown in FIG.1 and FIG.2. First, with reference to FIG. 1 and FIG. 2, the overall configuration of a gas concentration monitoring apparatus for measuring the gas flux and the gas concentration in the surface air according to the present embodiment will be described.

  As shown in FIG. 1, the gas monitor apparatus according to the present embodiment is configured to detect a gas concentration to measure a flux of a detection target gas contained in a gas diffused from soil or a rock layer A to which a trench B is applied as a rain countermeasure. An apparatus having a bottom surface open to the soil or rock layer A to be detected, and collecting the emitted gas from the soil or rock layer A through the open bottom opening 2a. From the calculated value of the initial time gradient of the gas concentration measured by the gas concentration detection means 3, the gas released from the lower part is stirred and mixed by the internal circulation and ventilation control means 4 (fan) with the measurement chamber 1 closed. Measure the flux. The measurement chamber 1 is provided with an exhaust port 2b for exhausting the air in the measurement chamber containing the diffused gas to the outside and an inlet port 2c for introducing outside air, and the measurement chamber 1, the exhaust port 2b, and the intake air are provided. It has outside air openings 15a, 15b, 8a, and 8b that communicate with each other through the mouth 2c and are open to the outside air. Here, the outside air opening portion 15a and the outside air opening portion 15b are collectively configured as the inlet cylinder 7, and the outside air opening portion 8a and the outside air opening portion 8b are collectively configured as the exhaust port 8 to the atmosphere. The outlet 8 controls the flow of air in conjunction with the mechanical inlet / outlet valve 5, the exhaust port 2 b and the exhaust on / off valve 6, which are actuated by electric signals. As a result, outside air is introduced into the measurement chamber 1 through the outside air openings 13a and 14a, the inlet chamber 21 and the inlet cylinder 7, and the inlet 2c, and air containing the diffused gas in the measuring chamber 1 is introduced. The gas concentration in the surrounding surface atmosphere introduced into the measurement chamber 1 is measured by the gas concentration detection means 3 which is discharged to the outside through the exhaust chamber 20 and disposed inside the measurement chamber 1. 1 and 2 have only one inlet 2c and an inlet on / off valve 5. However, there may be a plurality of inlets depending on environmental conditions. The inlet and exhaust directions of the measurement chamber 1 shown in FIG. A mechanism for reversing the rotation may be used.

As an embodiment that does not use a mechanical on-off valve that controls opening and closing by an electrical signal, a fan 41 capable of forward / reverse rotation control is provided inside the measurement chamber 1, and the fan 41 is an inlet 2 c inside the measurement chamber 1. The exhaust port 2b of the measurement chamber 1 is disposed on the downstream side of the ventilating air blowing direction of the forward / reverse rotation controllable fan 41, and the input is made with a negative pressure. When the air inlet film opening / closing valve 200 of the air opening 2c is opened and the exhaust film opening / closing valve 210 of the air outlet 2b is also opened with a positive wind pressure, the ventilation mode is set, and the forward / reverse rotation controllable fan 41 becomes an air flow in the opposite direction. When operating in this manner, both the inlet film on-off valve 200 and the exhaust film on-off valve 210 are closed, and the inside of the measurement chamber 1 is switched to the internal circulation mode in which the air flow circulates.

In addition, although this embodiment can be used as a leak monitor device to the ground of carbon dioxide stored underground, for example in a CCS business, it is not limited to this and detects various gas fluxes Is possible. For example, leakage of water, carbon dioxide, hydrocarbon gas, etc. from the target reservoir to the ground surface in the oil / natural gas development / production area or shale gas development area by the Enhanced Oil Recovery Law It can be similarly applied as a gas monitor device for detecting the above.

An inlet 2c and an inlet opening / closing valve 5 provided in the upper part of the measurement chamber 1 fixed on the soil or rock layer A connected to the underground stratum A and a plurality of two to four below the side of the measurement chamber 1 An exhaust port 2b and an exhaust opening / closing valve 6 are provided at a location, and an internal circulation and ventilation control means 4 and a gas concentration detection means 3 are arranged inside the measurement chamber 1 to constitute a measurement system. The shape of the measurement chamber 1 has various shapes such as a cylinder, a quadrangle, and a hemisphere capable of defining the bottom opening area S (m ² ) that contacts the lower soil or rock layer and the internal volume V (m ³ ). May be.

FIG. 1 represents an internal circulation mode in a closed system in which the measurement chamber 1 is interrupted except for the contact surface with the soil or rock layer A below it. The arrows in the figure indicate the circulating flow of air in the chamber. The inlet / outlet valve 5 provided at the top of the measurement chamber 1 and the exhaust opening / closing valves 6a and 6b provided at a plurality of two to four locations below the side surface of the measurement chamber 1 are all closed. In the internal circulation mode in which the internal ventilation control means 4 is operated and stirred and mixed so that the gas diffused from the bottom opening 2a and the internal air have a uniform concentration, from the start time of the measurement chamber 1 The gas concentration in the internal air is measured for an appropriate time by the gas concentration detection means 3, and the initial gas concentration time gradient is derived, whereby the gas flux is calculated from Equation 1 below.

G _flux : Gas flux emitted from soil or rock layer (mL / s / m ² )
Cchamber: Emission gas concentration (ppm) in the air in the measurement chamber
t: Elapsed time from the start of setting the internal circulation mode (s)
V: Internal volume of measurement chamber (m ³ )
S: Open area of the bottom (m ² ) in contact with the soil or rock layer below the measurement chamber

FIG. 2 shows a situation where a ventilation mode is realized in which the air inside the measurement chamber 1 is replaced with air in the atmosphere. The arrows in the figure indicate the direction of air flow in the entire monitor device and in the measurement chamber 1. The inlet 2c and the inlet on / off valve 5 provided at the upper part of the measurement chamber 1 are connected to the inlet cylinder 7, and are connected by screens (filters) 9a to 9e, an inlet cylinder cover 10, an inlet cylinder protection cover 12, and an upper protection cylinder 13. The surface air is introduced by removing rain, snow or dust, and the exhaust port 8a and 8b opened to the side of the lower defense cylinder 14 from the exhaust port 2b and the exhaust on-off valves 6a and 6b provided below the measurement chamber 1. According to the configuration of the in-cylinder cover 10, a ventilation mode is set in which the internal air of the measurement chamber 1 is discharged to the surrounding atmosphere without being influenced by weather such as rain. At the time when the ventilation of the measurement chamber 1 ends, the gas concentration in the surrounding surface layer atmosphere is measured by the gas concentration detection means 3 installed in the measurement chamber 1. Although the gas monitor apparatus shown in FIG. 2 includes a plurality of screens (filters) 9a to 9e, depending on the environmental conditions in the area where the monitor apparatus is installed, the air flow path includes 9a to 9e. The screen (filter) is appropriately inserted and arranged so that clean surface air (outside air) is guided to the measurement chamber 1 with a sufficiently small pressure loss that does not affect the measurement accuracy.

(Second Embodiment)
FIG. 3 shows an example of a system that realizes the ventilation mode and the internal circulation mode by controlling the operation of the mechanical intake opening / closing valve 50 and the exhaust opening / closing valve 60 that are opened and closed using electromagnetic force. In the gas monitor device according to the present embodiment, in addition to the configuration described in the first embodiment, the measurement chamber 1 is formed of a semicircular sphere including, for example, a circular lower opening portion. An inlet on / off valve 50 as the inlet 2c is provided at the top of the sphere, and an exhaust on / off valve 60 as an outlet 2b is provided in the vicinity of the outer periphery of the semicircular sphere. The shape of the measurement chamber 1 may be not only a semispherical shape but also a cylindrical or quadrangular prism shape whose bottom area S and internal volume V are known.

  The monitoring data processing and mode switching control device 100 of the entire monitoring device controls the exhaust valve / intake valve control / power supply circuit 120 to control the intake / exhaust valve 50 and the exhaust on / off valve 60 controlled to open and close by electromagnetic force. By operating, ventilation mode and internal circulation mode are realized alternately in a certain time cycle. At this time, the air flow by the ventilation control means 4 is a flow from the upper part to the lower part of the measurement chamber 1 and is designed to have a performance capable of realizing a sufficient ventilation flow and internal circulation flow. The power and signal of the gas concentration detection means 3 are transmitted to the measurement data processing and mode switching control device 100 of the entire monitor as a signal by the circuit 110 relating to the measurement amplifier and data transmission of the gas concentration detection means, and the gas flux and the atmosphere. The gas concentration data inside is analyzed and recorded in the main body or transferred to an external circuit. Examples of the mechanical or electromagnetic intake on / off valve 50 and the exhaust on / off valve 60 include a mechanical shutter valve or a butterfly valve that can be opened and closed by an electric signal. The circuit 110 relating to the measurement amplifier and data transmission of the gas concentration detecting means transmits the measured gas flux and the gas concentration data in the surface layer atmosphere to the alarm circuit 140 for judging the abnormality of the gas flux, and the fluctuation of the past background data. In light of the probability density distribution of the characteristics, a system is provided that issues an alarm signal related to an abnormality in gas flux from the soil or rock layer A by setting an appropriate risk factor.

When using the mechanical inlet / outlet valve 50 and the exhaust on / off valve 60, it is not particularly necessary to change the rotation of the ventilation control means 4 installed in the measurement chamber 1. The gas concentration sensor installed in the measurement chamber 1 may be a gas concentration sensor of interest, and a multi-gas monitor device can be formed by installing a plurality of them. However, when there is a limit to the amount of power that can be used, an apparatus configuration that realizes the valve opening / closing function by deforming the film by the fluid pressure of the airflow shown in FIGS.

4 and 5 show an embodiment of the measurement chamber 1 capable of switching between a ventilation mode and an internal circulation mode without using a valve operated by electromagnetic force. An inlet film opening / closing valve 200 using two thin and moderately elastic films that are respectively fixed at both ends inside the inlet port 2c arranged at the upper part of the measuring chamber 1 is provided on the lower side surface of the measuring chamber 1. Intake and exhaust are controlled by including an exhaust film opening / closing valve 210 using a thin film that is stopped from the outside of the exhaust port 61. These films are fixed at one end only to the chamber, and the other end is set as a free end so that the film can be easily opened and closed by a minute change in air pressure applied depending on the direction of air flow of the ventilation control means 4 in the chamber. The structure is made.

As shown in FIG. 4, when the air flow is induced upward by the forward / reverse rotation controllable fan 41, the inlet film opening / closing valve 200 closes the inlet 2c, and the exhaust film opening / closing valve 210 opens the outlet 61. By closing, the air in the measurement chamber 1 circulates internally (internal circulation mode). In this internal circulation mode, the gas diffused from the soil or rock layer A to the measurement chamber 1 is agitated and mixed by the internal circulation air flow, and quickly becomes a uniform gas concentration. Gas concentration increase data of about 30 to 100 seconds from the time when the internal circulation mode is started is recorded in the measurement data processing of the entire monitor device and the memory of the mode switching control device 100, and the gas is processed by numerical data processing based on a linear approximation formula. The concentration gradient is obtained, and the gas flux is calculated from Equation 1.

At this time, when the air flow is induced in the lower direction by the forward / reverse rotation controllable fan 41, the two films provided in the air inlet film opening / closing valve 200 are bent downward and deformed, and the atmospheric air from the air inlet 2c is deformed. The air is attracted to the measurement chamber 1, and at the same time, the films of the plurality of exhaust film opening / closing valves 210 are also deformed to the outside, whereby the ventilation mode in which the air inside the measurement chamber 1 is exhausted from the exhaust port 2 b to the atmosphere. At this time, since the ambient air around the gas concentration detection means 3 installed in the chamber is the same as the surface atmosphere, the gas concentration detection means 3 can measure the gas concentration in the surface atmosphere.

Using a prototype gas monitor device that embodies the gas flux measurement method of the present invention, in the actual test field of Kyushu University Ito Campus, the carbon dioxide gas flux in the natural state released from the soil in the test field Background data were measured for about one year using a chamber with a hemisphere diameter of 18.5 cm, a height of 9.5 cm, and an internal volume of 2.0 liters.

FIG. 6 is a plot of changes in carbon dioxide gas flux versus soil moisture content and soil temperature in the actual test field of Kyushu University Ito Campus. The carbon dioxide gas flux at a soil temperature of 20 ° C. shows an average value of ² μmol / s / m ² , and it is clear that the gas flux value tends to increase as the temperature rises. This is because the microbial activity in the soil is activated as the temperature rises, increasing the carbon dioxide concentration in the soil, resulting in an increase in the amount of carbon dioxide gas released into the atmosphere due to molecular diffusion. . In addition to soil temperature, effects such as soil moisture and surface wind speed were also observed. In addition, since measured values of 10 μmol / s / m ² or more were not observed throughout the year, as a setting of the ultimate risk factor, when measured values exceeding these values are observed, It is possible to assume an alarm system that determines that an abnormality occurs due to carbon dioxide from some other emission source mixed in the carbon dioxide emission in the natural state.

Regions and shale gas that carry out enhanced oil recovery and recovery (EOR) to monitor production and increase of oil and natural gas by using carbon dioxide and hydrocarbon gas, etc. It can be used for a wide range of applications, such as monitoring monitoring of leakage of hydrocarbon gas such as carbon dioxide and methane gas to the ground in the development area, and monitoring of carbon dioxide gas flux of cultivated soil in agricultural areas.

A Soil or rock layer B Trench for rain prevention 1 Measurement chamber 2a Bottom opening 2b Exhaust port 2c Inlet port 3 Gas concentration detection means (gas supply sensor or air supply means to external gas concentration sensor)
4 Ventilation control means (fan)
5 Inlet air on / off valve 6a, 6b Exhaust on / off valve 7 Inlet cylinder 8a, 8b 8 Air outlet 9a, 9b, 9c, 9d, 9e Screen (filter)
DESCRIPTION OF SYMBOLS 10 Entry cylinder cover 11 Measurement chamber protection cover 12 Entry cylinder protection cover 13 Upper defense cylinder 13a, 13b Outside air opening 14 Lower defense cylinder 14a, 14b Outside air opening 15a, 15b Outside air opening 20 Exhaust chamber (8a, 8b, 9d 9e, 11, 14, 14a, 14b)
21 Intake chamber (9a, 9b, 9c, 10, 12, 13, 13a, 13b, 15a, 15b)
41 Forward / reverse rotation controllable fan 50 Inlet on / off valve 60 that opens / closes using electromagnetic force Exhaust on / off valve 100 that opens / closes using electromagnetic force Measurement data processing and mode switching control device 110 for the entire monitoring device Measurement amplifier and circuit 120 related to data transmission control of exhaust valve and intake valve / power supply circuit 130 fan control / power supply circuit 140 inside the chamber alarm circuit 200 for judging abnormality of gas flux Inlet film on / off valve using two films (Inlet film on / off valve)
210 Exhaust film opening / closing valve (exhaust film opening / closing valve) using thin elastic film

Claims (5)

In a gas monitor device that measures the unit area of the detection target gas contained in the gas emitted from the soil or rock layer, the gas flux per unit time and the gas concentration in the surface layer atmosphere,
Provided at a position near the detection target soil or rock layer, an opening for exhaust, an inlet for inlet, an inlet for the inlet, and the inlet and the inlet. Each open / close valve, ventilation control means for performing internal circulation and ventilation, an exhaust chamber that is isolated outside and exhausts the emitted gas, and an outside that is isolated outside and enters the surface atmosphere (outside air) A gas chamber,
The emitted gas is collected from the soil through the open bottom surface of the lower part of the measurement chamber, and the on-off valves provided at the exhaust port and the intake port are closed, and the air flow of the ventilation control means is used. An internal circulation mode that stirs and mixes the emitted gas is realized, communicates with the outside air through the exhaust port and the exhaust chamber, and simultaneously communicates from the outside air through the intake chamber and the intake port. A measurement chamber that realizes two types of operation modes, a ventilation mode that introduces outside air through a vent and exhausts the collected air containing the emitted gas to the outside;
A gas concentration detection means disposed inside the measurement chamber and measuring a gas concentration of a detection target in the two types of operation modes;
The gas concentration detection means measures gas flux from the calculated value of the initial gas concentration time gradient in the internal circulation mode in the measurement chamber, and alternately measures the gas concentration in the atmosphere in the ventilation mode. Gas monitor device. The gas monitor device according to claim 1,
An internal circulation mode in which the measurement chamber is closed by the on-off valve and the diffused gas diffused from below is kept in the measurement chamber and stirred and mixed, and air including the diffused gas in the measurement chamber is supplied to the on-off valve. The exhaust air is exhausted to the outside through the exhaust port and the exhaust chamber, and the surface air is introduced into the measurement chamber through the intake chamber, the intake port and the on-off valve, and the internal air of the measurement chamber is replaced. And a ventilation control means for realizing a ventilation mode by the on-off valve that eliminates the emitted gas and water vapor diffused from underground. In the gas monitor device according to claim 1 or 2,
The ventilation control means is disposed between the inlet in the measurement chamber and the gas concentration detection means;
An exhaust port of the measurement chamber is disposed on the downstream side of the air flow of the ventilation control means;
The measurement chamber has a mechanism in which the inlet is formed by an opening / closing valve that is opened by a slight negative pressure of the airflow, and the exhaust port is formed by an opening / closing valve that is opened by the wind pressure of the airflow. A gas monitor device characterized by that. The gas monitor device according to claim 3, wherein
The measurement chamber is formed of a semispherical sphere having a circular lower opening portion, the inlet is disposed at the top of the semispherical sphere, and an exhaust outlet is provided near the outer periphery of the semispherical sphere. A gas monitor device that is arranged. The gas monitor device according to claim 1,
The gas concentration detection means statistically processes the fluctuation value of the background measurement data in the natural conditions in the gas flux emitted from the soil or rock layer and the gas concentration in the surface layer atmosphere, and sets the risk factor to the soil or A gas monitor device that judges an abnormality of gas flux from a rock layer and outputs an alarm.