JP4508494B2 - Gas hydrate exploration system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to exploration system for probing a gas hydrate present in the soil of the sea bed, such as submarine or the like.
[0002]
[Prior art]
Natural gas often exists in a gaseous state inside a gas layer formed in the ground (referred to as a “free gas layer”), and is generally excavated from the free gas layer and used. However, apart from this, natural gas may exist as a hydrate in a solid state produced by hydration. The natural gas hydrate (hereinafter referred to as “gas hydrate”) is a kind of clathrate compound (clathrate compound) and is a three-dimensional basket formed by a plurality of water molecules (H ₂ O). This is a crystal structure in which molecules such as methane (CH ₄ ) and ethane (C ₂ H ₆ ), which are natural gas components, enter and are included in a clathrate of the mold.
Such a gas hydrate is in a state in which natural gas is densely filled therein. Theoretically, natural gas of about 170 m ³ in terms of gas in the standard state is contained in 1 m ^{3 of} gas hydrate, which attracts much attention as a next-generation energy source.
[0003]
Gas hydrates can be produced and exist stably under conditions of low temperature and high pressure, so they form a layer in the ground that meets these conditions (“gas hydrate layer”, or simply “hydrate” Can be present). Specifically, it has been found that it is widely distributed in the lower part of permafrost such as the Arctic Circle and the Antarctic Circle, or in the submarine ground at a depth of about 300 m or more. In addition, it is thought that there will be a large amount in the submarine ground near Japan, and the exploration or investigation is being conducted sequentially.
[0004]
As a method for exploring the hydrate layer existing on the bottom of the sea such as the sea bottom, an elastic wave including sound waves is transmitted from the surface exploration ship toward the sea bottom as an exploration signal, and the reflected elastic wave is received. In general, a method for exploring the hydrate layer by analyzing the propagation speed of elastic waves and the like is generally used.
[0005]
[Problems to be solved by the invention]
In order to conduct such exploration with high accuracy, the exploration ship is required to accurately grasp the absolute position of the ship and the relative position with the consort ship at sea, and to maintain that position. Such position is often grasped using a radar or the like, but it is difficult to grasp and maintain the position due to the influence of ocean current, wave height or wind.
In addition, the elastic waves transmitted and received from the exploration ship toward the seabed are easily attenuated in the water, and therefore the exploration accuracy is not always good in places where the water depth is deep or where the seafloor topography is undulating.
Due to these various factors, it has been very difficult to improve the exploration accuracy and exploration efficiency of the gas hydrate present at the bottom of the water.
[0006]
The present invention has been made in view of the above circumstances, capable of improving the search accuracy and search efficiency of the gas hydrate is present in the sea bed, and an object thereof is to provide a gas hydrate exploration system.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is a system for exploring a gas hydrate existing in the ground of the bottom of the water , wherein the transmitter transmits an elastic wave from the water side toward the bottom of the water, and the ground of the bottom of the water An exploration rig that has an oscillating portion that is installed on the surface and oscillates the ground of the bottom by remote control, and the elastic wave that is reflected from the direction of the bottom of the water , or A receiver that receives elastic waves propagated from the ground into the water on the upper side of the water, and at least one of the transmitter or the receiver moves on the water, and self-position is determined by a signal from an artificial satellite. And a self-position recognition device for recognizing.
[0008]
In this way, since at least one of the transmitter and the receiver can recognize its own position from a signal from an artificial satellite, it is hardly affected by ocean currents, wave heights, winds, etc. The gas hydrate can be explored while always grasping its own position with high accuracy and maintaining the position or performing correction according to the change.
In addition, since the exploration rig that transmits the exploration signal from the ground on the bottom is used, the exploration signal can be transmitted directly to the ground on the bottom without using water.
[0009]
The invention according to claim 2 is the gas hydrate exploration system according to claim 1, wherein at least one exploration ship having the transmitter and the self-position recognition device, the receiver and the self And at least one exploration ship having a position recognition device.
[0010]
As described above, since the search signals are transmitted and received using a plurality of search ships equipped with self-position recognition devices, it is possible to grasp the absolute position of each search ship extremely accurately. In addition, the relative positions of the exploration ships can be grasped very accurately.
[0011]
A third aspect of the present invention is the gas hydrate exploration system according to the second aspect, further comprising a submersible craft that searches the bottom of the water and transmits the searched information to the exploration ship. .
[0012]
In this way, since the submarine is used to explore the seabed, it is possible to explore the bottom from a position closer to the bottom.
[0013]
The invention according to claim 4 is the gas hydrate exploration system according to claim 1 , wherein the exploration rig includes a propulsion device for moving in water.
[0014]
As described above, since the exploration rig is provided with the propulsion device, the exploration rig can be easily installed and collected, and the point to be explored can be easily changed.
[0015]
The invention according to claim 5 is a laser oscillator that oscillates a laser beam for irradiating methane in the gas hydrate , a spectroscope that splits Raman scattered light from the methane, and the spectroscope. And a detector for detecting the methane by analyzing the Raman scattered light.
[0016]
In this way, the methane is detected and the gas hydrate is probed by spectroscopic analysis of the Raman scattered light, that is, by chemical component analysis. Therefore, the existence of the gas hydrate is more reliably probed. be able to.
[0017]
A sixth aspect of the present invention is the gas hydrate exploration system according to the fifth aspect , wherein the exploration ship includes the laser oscillator, the spectroscope, and the detector. Using an optical fiber suspended to a nearby position, the methane is irradiated with the laser light and the Raman scattered light is introduced into the spectrometer.
[0018]
In this way, optical fiber is used to irradiate methane near the bottom of the water with laser light and to introduce Raman scattered light into the spectrometer, which is necessary for spectral analysis such as laser oscillators, spectrometers, and detectors. The main equipment can be installed in the exploration ship to avoid contact with water.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
First reference Embodiment
First, a first reference embodiment of the gas hydrate search system according to the present invention will be described with reference to FIG.
This gas hydrate exploration system (hereinafter may be simply referred to as “exploration system”) includes a hydrate layer (gas hydrate) H formed in the seabed ground (water bottom ground) G and includes sound waves. It is comprised from the exploration ship 10A and the exploration ship 10B which explore using an elastic wave.
These exploration ships 10A and 10B have substantially the same configuration, and transmit / receive receivers (transmitters and receivers) that transmit and receive elastic waves (exploration signals) including sound waves to search the hydrate layer H. 11a and 11b, and self-position recognition devices 12a and 12b for recognizing the position of the ship by a signal from the artificial satellite S, respectively. In other words, the exploration ships 10A and 10B can conduct exploration of the hydrate layer H while accurately grasping the position of the ship by GPS (Global Positioning System). Although only one artificial satellite S is shown in FIG. 1, the self-position recognition devices 12a and 12b actually recognize the position of the ship by signals from a plurality of artificial satellites S.
[0021]
Thus, since the self-position recognizing devices 12a and 12b allow the exploration ships 10A and 10B to recognize the absolute position of the own ship at sea with extremely high accuracy, the relative positions of the exploration ships 10A and 10B are relative to each other. Can be determined with extremely high accuracy.
[0022]
In the exploration method using this exploration system, an elastic wave is transmitted from the exploration ship 10A or the exploration ship 10B toward the surface (sea floor) of the seabed ground G, and the elastic wave (reflected wave) reflected from the seabed is transmitted to the exploration ship. 10A or the exploration ship 10B receives and analyzes it, and whether or not the hydrate layer H exists, and if so, its size, depth, layer thickness, etc. can be explored. In FIG. 1, as an example, an elastic wave l is transmitted from the exploration ship 10 </ _b > A, and the exploration ship 10 </ _b > B reflects the reflected wave l ₁ reflected from the seabed and the reflected wave l ₂ reflected from the hydrate layer H. Is shown.
[0023]
In the gas hydrate exploration system according to the present embodiment, the exploration ships 10A and 10B receive their absolute position self-position recognition devices 12a and 12b based on signals from the artificial satellites S1, S2, and S3. Each is provided. Therefore, it is possible to grasp the absolute position of the ship with high accuracy without being affected by the influence of ocean currents, wave heights, winds, etc. Can be corrected. In addition, since the absolute positions of the ship's own ships can be grasped very accurately in this way, the relative positions of the exploration ship 10A and the exploration ship 10B can also be grasped accurately. Therefore, the search for the hydrate layer H can be performed with extremely high accuracy.
Further, it is possible to reduce the cost for constructing the exploration system without requiring an expensive device such as a radar for measuring the relative position with the consort ship (other ship).
[0024]
In the present embodiment, the case where two exploration ships are used has been described as an example, but the present invention is not limited to this. If a fleet of exploration ships is formed using a larger number of exploration ships, the exploration accuracy can be further improved.
Further, the exploration ship may tow one or more floats equipped with a transmitter / receiver. In this case, since it is possible to search with at least one exploration ship, the exploration cost can be further reduced.
[0025]
Second Reference Embodiment
A second reference embodiment of the gas hydrate search system according to the present invention will be described with reference to FIG.
In the present embodiment, the submersible boats 20A and 20B are added to the components of the exploration system in the first reference embodiment. That is, the hydrate layer H in the seabed ground G is searched from both the sea and the sea.
[0026]
The submersible crafts 20A and 20B are manned submersibles that are operated by crew members, and search for the topography and geology of the seabed by diving in the sea. These submersibles 20A and 20B use a transmitter / receiver 21a, 21b for transmitting an elastic wave including a sound wave toward the seabed and receiving an elastic wave reflected from the seabed, and a sonar, a laser, a millimeter wave, or the like. A communication device (not shown) that performs communication between the ships 10A, 10B or the submersibles is provided.
[0027]
In the exploration method using this exploration system, an elastic wave (reflected wave) transmitted from the oceanic exploration ships 10A and 10B or the submersibles 20A and 20B in the sea is directed toward the seabed and reflected from the seabed. The exploration ships 10A and 10B or the submersible boats 20A and 20B receive them.
The information obtained from the elastic waves is analyzed by adding information obtained by the crew of the submersibles 20A and 20B by visually observing the seabed side, that is, information such as the undulation state or geology of the seabed topography. Whether or not H exists and, if present, its size, depth, layer thickness, etc. can be probed.
[0028]
In the gas hydrate exploration system according to the present embodiment, since the submersible boats 20A and 20B are used, since the exploration can be performed from a position closer to the seabed, the attenuation of elastic waves in water can be further reduced. Further, the exploration accuracy of the hydrate layer H can be further improved.
In addition to the information obtained by the elastic wave, the information can be comprehensively explored by adding information obtained by observing the seabed by the crew member, so that the exploration accuracy can be further improved.
[0029]
In the present embodiment, the submersible is operated manned, but may be unmanned capable of automatic operation.
Moreover, although the case where two water boats were used was described as an example, the present invention is not limited to this. If a larger number of submersibles are used, the search accuracy can be further improved.
Further, the submersible craft may be towing one or a plurality of floats to which the transmitter / receiver is attached, that is, to blow underwater. In this case, since it is possible to search with at least one submersible craft, the search cost can be further reduced.
[0030]
First Embodiment
Next, a first embodiment of a gas hydrate exploration system according to the present invention will be described with reference to FIG.
In the present embodiment, the exploration rig 30 disposed on the seabed ground G is added to the components of the second reference embodiment. Therefore, the same components as those in the second reference embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0031]
The exploration rig 30 is installed on the seabed, and includes a main body 31, a leg 32 provided on the lower side of the main body 31 and standing on the seabed G, and provided on the lower side of the main body 33. And a vibration unit 33 that vibrates the ground G.
The main body 31 is between the remote control device that operates the shaking unit 33 by remote control from the oceanic exploration vessels 10A and 10B or the submersible boats 20A and 20B, and the exploration vessels 10A and 10B or the submersible boats 20A and 20B. A communication device that transmits and receives information (none of which is shown).
In FIG. 3, only one exploration rig 30 is shown, but a plurality of exploration rigs 30 are actually provided.
[0032]
An elastic wave is propagated from the seabed ground G struck by the exploration rig 30 and is detected by another exploration rig 30. In addition, the elastic wave propagated from the seabed ground G into the seawater is detected by the submersibles 20A and 20B or the exploration ships 10A and 10B. The state of the seabed G can be grasped from the propagation speed of this elastic wave.
[0033]
In the gas hydrate exploration system according to the present embodiment, the exploration rig 30 is provided so that elastic waves can be transmitted directly to the seabed ground G without passing through seawater. For this reason, the elastic wave is not attenuated in water as in the case of transmitting an elastic wave from the water or underwater, for example, so that the search accuracy can be further improved with less search error.
In addition, even if the number of submersible crafts, which are generally expensive, is reduced, the search accuracy can be made sufficiently high, so that the entire system can be configured in a simple manner, reducing the search cost and improving the search efficiency. Can be planned.
[0034]
In the present embodiment, each of the plurality of exploration rigs is remotely controlled by radio, but each exploration rig may be connected by wire.
[0035]
FIG. 4 shows an exploration rig 30A as a modification of the exploration rig 30 described above.
This exploration rig 30A is obtained by adding a function for moving underwater to the exploration rig 30. A propulsion device 36 and a float 37 are added to the main body 31 of the exploration rig 30 described above. It has a configuration with.
[0036]
The propulsion device 36 is composed of a propeller and an actuator (not shown) that rotationally drives the propeller, and a plurality of propulsion devices 36 are provided on the side or above the main body 31. In the main body 31, remote control means (not shown) for remotely controlling these propulsion devices 36 is provided. That is, the exploration rig 30A can be moved in the sea by remote control from the exploration ships 10A and 10B or the submersibles 20A and 20B.
The float 37 is composed of a fiber, a steel shell, or the like that can withstand water pressure in the deep sea, and gives an appropriate buoyancy to the exploration rig 30A by entering and discharging internal gas. By providing this float 37, the exploration rig 30A can be softly landed on the seabed and can be easily detached from the seabed.
[0037]
If such an exploration rig 30A equipped with the propulsion device 36 is used, the exploration rig 30A can be easily installed and collected, and the exploration point can be easily changed. A wide range can be explored per unit time, and the exploration efficiency can be improved.
[0038]
Second Embodiment
A second embodiment of the gas hydrate exploration system according to the present invention will be described with reference to FIGS.
The exploration system in the present embodiment is configured by an exploration ship 10 </ b> C provided with a Raman spectroscopic analyzer 40. This exploration ship 10C has the same configuration as the exploration ship 10A shown in the first reference embodiment and the second reference embodiment, except that the Raman spectroscopic analyzer 40 is provided.
[0039]
As shown in FIG. 5, when a crack or the like occurs in a part of the seabed ground G including the hydrate layer H, methane in the hydrate layer H gradually leaks into the sea from this crack. In FIG. 5, seawater in which methane is dissolved or methane (methane gas) leaking into the sea as bubbles is shown as a symbol m. That is, if methane can be detected from the sea, the possibility that the hydrate layer H exists in the seabed ground G below it is very high.
The Raman spectroscopic device 40 can detect the hydrate layer H in the seabed ground G by detecting such methane m in the sea.
[0040]
As shown in FIG. 6, the Raman spectroscopic analyzer 40 includes a laser oscillator 41, a dichroic mirror 42, an optical fiber 43, a spectrometer 44, and a detector 45.
In the Raman spectroscopic analysis device 40, components other than the optical fiber 43 are provided in the exploration ship 10C. The optical fiber 43 is suspended in the sea such that the tip thereof reaches a position near the seabed, and laser light is irradiated to the seawater from a convex lens 43a provided at the tip.
[0041]
In the exploration method using this exploration system, first, the laser oscillator 41 oscillates laser light L such as an argon (Ar) ion laser. The oscillated laser light L passes through the dichroic mirror 42, travels through the optical fiber 43, and is irradiated into seawater from the convex lens 43a at the tip. When the laser light L is incident on each substance in the seawater, the Raman scattered light R slightly shifted in frequency corresponding to the component of each substance is scattered. That is, the Raman scattered light R is in a state in which many light components having a specific frequency corresponding to the component of each substance are included. If this Raman scattered light R is spectrally analyzed, it is possible to detect whether or not methane m exists in the sea.
[0042]
A part of the Raman scattered light R is introduced from the convex lens 43a into the optical fiber 43 and travels again toward the exploration ship 10C. Then, it is introduced into the spectroscope 44 by the dichroic mirror 42 on the exploration ship 10 </ b> C, where it is split. The spectrally scattered Raman scattered light R is introduced into the detector 45 where it is detected whether or not methane m is present. That is, if a light component corresponding to methane m is detected, the hydrate layer H existing in the seabed ground G below it is searched.
[0043]
In the gas hydrate exploration system according to the present embodiment, the methane m is detected by spectroscopically analyzing the Raman scattered light R using the Raman spectroscopic analyzer 40, that is, by chemical component analysis, and the hydrate layer H Therefore, the existence of the hydrate layer H can be more reliably explored.
Further, if the exploration method using such a gas hydrate exploration system is carried out after the exploration using the elastic wave described in the above embodiments, the hydrate layer H of the hydrate layer H can be obtained by both physical basis and chemical basis. Can support existence.
[0044]
Furthermore, since the optical fiber 43 is used to irradiate the methane m near the seabed with the laser light R and introduce the Raman scattered light R into the spectrometer 44, the laser oscillator 41, the spectrometer 44 and the detector. The main components of the Raman spectroscopic analyzer 40 such as 45 can be provided in the exploration ship 10C. Therefore, contact between precise equipment and seawater can be avoided, maintenance can be facilitated, and reliability and durability of the Raman spectroscopic analyzer 40 can be improved.
[0045]
If the seafloor topography is severe, the main components of the Raman spectroscopic analyzer, such as a laser oscillator, spectrometer, and detector, are mounted on an unmanned small submersible, etc., and explored while submerging in the sea. You may do it. In this case, the optical fiber is not an essential component.
[0046]
【The invention's effect】
As described above, in the gas hydrate exploration system and exploration method according to the present invention, since the above-described configuration is adopted, the exploration accuracy and exploration efficiency of the gas hydrate existing in the bottom of the water can be improved. A gas hydrate exploration system and exploration method can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first reference embodiment of a gas hydrate search system according to the present invention.
FIG. 2 is a schematic configuration diagram showing a second reference embodiment of the gas hydrate search system according to the present invention.
FIG. 3 is a schematic configuration diagram showing a first embodiment of a gas hydrate search system according to the present invention.
FIG. 4 is a schematic configuration diagram showing a modification of the exploration rig shown in FIG. 3;
FIG. 5 is a schematic configuration diagram showing a second embodiment of the gas hydrate search system according to the present invention.
FIG. 6 is a schematic configuration diagram showing a Raman spectroscopic analyzer.
FIG. 7 is a partially enlarged view showing a part of FIG. 6 in an enlarged manner.
[Explanation of symbols]
10A, 10B, 10C Exploration ships 11a, 11b Transmitter / receiver (transmitter, receiver)
12a, 12b Self-position recognition devices 20A, 20B Submersible craft 21a, 21b Transmitter / receiver (transmitter, receiver)
30, 30A exploration rig 36 propulsion device 37 float 40 Raman spectroscopic analysis device 41 laser oscillator 42 dichroic mirror 43 optical fiber 44 spectroscope 45 detector l, l ₁ , l ₂ elastic wave (probing signal)
m Methane (methane gas)
G Submarine ground (submarine ground)
H Hydrate layer (gas hydrate)
L Laser light R Raman scattered light S Artificial satellite

Claims (6)

A system for exploring gas hydrates existing in the bottom of the water,
A transmitter for transmitting an elastic wave from the water upper side toward the water bottom;
An exploration rig installed on the ground of the bottom of the water and having an oscillating portion that vibrates the ground of the bottom of the water by remote control;
A receiver that receives the elastic wave reflected from the bottom of the water , or the elastic wave propagated into the water from the ground of the bottom of the water quake by the vibration unit, on the water side;
A self-position recognizing device that moves on the water integrally with at least one of the transmitter or the receiver and recognizes the self-position by a signal from an artificial satellite;
A gas hydrate exploration system characterized by comprising: At least one exploration ship having the transmitter and the self-position recognition device;
At least one exploration ship having the receiver and the self-position recognition device;
The gas hydrate exploration system according to claim 1, comprising:   The gas hydrate exploration system according to claim 2, further comprising a submersible craft that explores the bottom of the water and transmits the searched information to the exploration ship. The gas hydrate exploration system according to claim 1 , wherein the exploration rig includes a propulsion device for moving in water. A laser oscillator that oscillates a laser beam for irradiating methane in the gas hydrate ;
A spectroscope for spectroscopic analysis of Raman scattered light from the methane;
A detector for detecting the methane by analyzing the Raman scattered light separated by the spectrometer;
The gas hydrate exploration system according to any one of claims 1 to 4, further comprising: While providing the laser oscillator, the spectrometer and the detector in an exploration ship,
By using an optical fiber which is suspended from the survey vessel to a position near the sea bed, wherein the Raman scattered light irradiates the laser light to the methane to claim 5, characterized in that introduced into the spectroscope Gas hydrate exploration system.

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