JP6396172B2 - Hydrate collection device and collection method - Google Patents

Description

  The present invention relates to a hydrate collecting device and a collecting method for collecting methane hydrate buried in the bottom of the ocean, a lake or the like.

  A gas hydrate is a molecule (guest molecule) inside a cage structure (sometimes called clathrate) of water molecules (host molecules) formed by hydrogen bonding under high pressure and low temperature generation conditions. ) Are encased crystals. It is known that methane hydrate mainly containing methane gas is present as guest molecules under the bottom of the ocean, lakes, etc. that satisfy the conditions for high-pressure and low-temperature gas hydrate formation. ing.

The methane hydrate on the bottom of the sea or lake (hereinafter collectively referred to as the bottom of the water) is in a state where the surface methane hydrate exposed on the bottom surface of several hundred meters in depth is mixed with sand in the basement of the water bottom. There is an existing sand layer type methane hydrate.
Sand layer-type methane hydrate is deeper underground than the bottom of the water and is mixed with sand, so it is considered difficult to collect technically and cost-wise.
On the other hand, since the surface layer type methane hydrate is exposed at the bottom of the water, it is easier to collect than the sand layer type, and a method for efficiently collecting the surface layer type methane hydrate is required.

  For example, in Patent Document 1, as a method of collecting a mass of methane hydrate mined from a methane hydrate layer on the sea floor, a pipe having both ends released is used as a transfer pipe from the sea floor to the sea surface. A method of raising the inside of the transfer pipe and collecting from above the transfer pipe is disclosed. Since methane hydrate has a lower density than water, it rises in the transfer pipe by buoyancy. In Patent Document 1, high-pressure gas such as compressed air is blown from the lower side in the transfer pipe, and the lift in the transfer pipe is increased by a bubble pump principle (also referred to as gas lift effect) in which bubbles of the blown gas form an upward flow. ing.

  In addition, when the methane hydrate mass rises in the transfer pipe, the pressure and temperature in the pipe become lower and higher than the sea floor as it approaches the sea surface, so part of the methane hydrate mass breaks down as it rises in the pipe. To do. It is described that the gas lift effect is increased by the bubbles of methane gas generated by the decomposition.

JP 2002-536573 A

Here, the volume of bubbles present in the water greatly changes depending on the pressure. Specifically, the volume of the bubble is reduced under high pressure, and the volume is increased when the pressure is reduced. For example, when the bubble rises from a water depth of 1000 m to near the sea surface (water depth of 0 m), the volume of the bubble is about 100 Double.
If the volume of bubbles in the transfer pipe becomes large and the ratio of the bubbles (gas) in the pipe becomes too large, the upward flow due to the bubbles may not be formed well and the flow of water may become unstable. Thereby, there exists a possibility that the raise efficiency of methane hydrate may fall.

  In particular, methane hydrate decomposes as it rises, generating cracked gas (methane) bubbles, so the proportion of bubbles in the transfer pipe tends to increase as you approach the sea surface. The risk of a decrease in efficiency increases.

  An object of the present invention is to solve the above problems and to provide a hydrate collecting device and a hydrate collecting method capable of collecting methane hydrate in the bottom of the water as a lump.

  In view of the above problems, the hydrate collecting device according to the first aspect of the present invention is a hydrate collecting device that collects methane hydrate in the bottom of the water, and an inlet portion into which a mass of methane hydrate that rises in water enters. And a hydrate riser pipe having a methane hydrate take-out portion on the upper side, and an injection for injecting water in which methane gas is not dissolved to a saturated state into a pipe in a region deeper than the water depth of 400 m of the hydrate riser pipe And a section.

In the present specification, “methane hydrate” means a gas hydrate formed by mainly incorporating methane into the water-like cage structure of water molecules formed by hydrogen bonds, and includes pure methane. In addition to the gas hydrate to be used, natural gas hydrate containing methane as a main component (for example, containing other components such as hydrocarbons such as ethane and propane, carbon dioxide, etc.) is included.
“Water” includes seawater, brackish water, etc. in addition to fresh water and fresh water. For example, ocean and lake water.

  In general, since the pressure is high and the water temperature is low at a depth deeper than 400 m, methane hydrate is generated when sufficient methane is present in the water (in a saturated state). Therefore, the methane hydrate layer usually exists at a depth of 400 m or more.

A methane hydrate layer at the bottom of the seabed or lake bottom is excavated by a drilling means such as a drill or a bucket, and separated from the methane hydrate layer as a mass of methane hydrate (hereinafter sometimes referred to simply as a mass). The In this aspect, the excavated methane hydrate lump enters the pipe from an inlet provided below the hydrate riser pipe, rises in the water in the pipe, and is taken out from the take-out section above. It is configured as follows.
It is desirable to collect the methane hydrate mass as large as possible as long as it can pass through the hydrate riser pipe. However, when drilling with a drill or the like, small lumps (grains) are usually formed. Both lumps enter the inlet.

By the way, methane is almost dissolved in the water existing near the methane hydrate layer at the bottom of the water. Therefore, methane hydrate is not normally decomposed in a portion deeper than the depth of 400 m that satisfies the methane hydrate generation condition.
On the other hand, when the mass of methane hydrate rises in the hydrate riser to a depth of less than 400 m, the pressure and temperature in the water are outside the conditions for producing methane hydrate, so decomposition begins. At this time, if there are many small chunks of methane hydrate as described above, the small chunks have a large specific surface area and thus are easily decomposed, and excessive bubbles of cracked gas (methane) may be generated in the water in the pipe. is there. In addition, since the volume of bubbles increases when the water depth becomes shallow, the proportion of bubbles in the tube becomes too large, which may hinder the rise of methane hydrate.

Here, the hydrate sampling apparatus according to the present aspect includes an injection section for injecting water in which methane gas is not dissolved to a saturated state into a pipe in a region deeper than the water depth of 400 m of the hydrate riser pipe.
As described above, water in the vicinity of the methane hydrate layer at the bottom of the water is almost saturated, so water saturated with methane gas enters the hydrate riser from the inlet. If water in which methane gas is not dissolved to a saturated state is injected into a tube deeper than 400 m, the methane concentration in the water in the tube can be lowered.

When the methane concentration in the water in the hydrate riser is lowered, the mass of methane hydrate is decomposed even if the pressure and temperature are the conditions for producing methane hydrate.
At this time, as described above, since the small methane hydrate lump (grain) is easily decomposed, it is decomposed and almost disappeared when the methane concentration in the water in the pipe is lowered. Methane gas generated by the decomposition is dissolved in water under high pressure (pressure in a region deeper than 400 m).
On the other hand, a large mass of methane hydrate stops with only a slight decomposition of the surface and is an endothermic reaction, so ice is generated on the surface of the methane hydrate mass and the decomposition reaction of methane hydrate is suppressed. .

In that state, the mass of methane hydrate rises in the pipe by buoyancy. That is, the mass of methane hydrate in the pipe rises as a collection of mainly large masses with few small masses. And if it raises to the area | region shallower than 400 m of water depth, since the production | generation equilibrium (pressure) of methane hydrate will be a decomposition condition, the surface of a lump will start decomposition | disassembly. At the same time, ice is further generated due to decomposition endotherm, and the surface of the methane hydrate lump is covered with an ice film together with the ice previously generated on the surface. Thereby, the decomposition reaction of methane hydrate stops due to the self-preserving effect.
In addition, since the small chunks (grains) of methane hydrate have already decomposed and almost disappeared as described above, the possibility that the small chunks (grains) are decomposed and generate methane gas in a region where the water depth is shallow is reduced. The

  Accordingly, by injecting water from which the methane gas is not dissolved to the saturated state into the pipe in a region deeper than the water depth of 400 m of the hydrate riser pipe from the injection part, a region where the water depth at which the methane hydrate is subjected to the decomposition condition is shallow ( At the stage where the water depth is raised to less than 400 m), the amount of methane gas generated by the decomposition of the methane hydrate can be reduced.

By the way, in the region where the water depth is shallower than 400 m, the methane gas generated until the ice film is formed and the decomposition is stopped becomes a bubble and exhibits a gas lift effect that supports the buoyancy of the methane hydrate lump. Thereby, the upward movement of the methane hydrate lump becomes smoother. However, as described above, the volume of gas generated in a shallow region is large, so if a large amount of methane gas is generated at a stretch in that region, the volume occupied by bubbles relative to water in the hydrate riser tube becomes excessive, As a result, the methane hydrate lump may be prevented from moving up smoothly. Since the generation amount of methane gas by methane hydrate decomposition | disassembly is reduced in the area | region as above-mentioned, this invention can reduce the possibility.
Therefore, it is possible to efficiently collect methane hydrate lump at the bottom of the water.

  The hydrate sampling apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, the injection port of the injection portion is provided at a position of a lower end portion of the hydrate riser pipe. It is.

In other words, the injection port of the injection part is provided at a position near the inlet part provided below the hydrate riser pipe.
According to this aspect, it is possible to increase the distance from the position where the injection port of the injection portion is provided until the pressure and temperature in the hydrate riser pipe reach a water depth of 400 m which is a decomposition condition of methane hydrate. Therefore, the gas hydrate lump that moves up and down in the pipe can be reliably decomposed until the gas hydrate lump reaches a water depth of 400 m.

  The hydrate sampling apparatus according to the third aspect of the present invention is characterized in that, in the first aspect or the second aspect, a plurality of injection ports of the injection part are provided in the vertical direction. .

  According to this aspect, by injecting water into the pipe in stages, it is possible to prevent the gas hydrate lump from being decomposed at once in the vicinity of the injection port and to decompose the gas hydrate in stages.

  The hydrate sampling apparatus according to a fourth aspect of the present invention is characterized in that, in the third aspect, the injection section is capable of adjusting the amount of water injected from each inlet.

According to this aspect, the amount of water injected from each inlet can be adjusted in accordance with the size of the excavated methane hydrate lump and the proportion of the lump size.
The size of the excavated methane hydrate lump and the ratio of the size of the lump vary depending on the state of the methane hydrate layer to be excavated, the underwater environment, the type of excavation means, and the like. For example, when there are many small lumps, the injection amount of water can be increased and the small lumps can be reliably decomposed.

  A hydrate sampling apparatus according to a fifth aspect of the present invention is the fluid supply unit according to any one of the first to fourth aspects, wherein the fluid supply unit supplies fluid into a pipe in a region shallower than a water depth of 400 m of the hydrate riser pipe. It is characterized by providing.

The “fluid” means liquid or gas. Examples of the liquid include water such as seawater and lake water, and examples of the gas include air.
In the hydrate riser pipe, ice is generated by the decomposition and endotherm of methane hydrate, so that the mass of methane hydrate moving up may be clogged. In such a case, for example, by supplying water (fluid) having a temperature higher than that of the water in the pipe into the pipe, the generated methane hydrate and the ice generated on the surface of the methane hydrate lump are decomposed. The clogging can be eliminated.
Moreover, clogging can be eliminated by temporarily blowing a gas (fluid) such as air vigorously.

  The hydrate sampling apparatus according to a sixth aspect of the present invention is characterized in that, in the fifth aspect, a plurality of supply ports of the fluid supply section are provided in the vertical direction.

  According to this aspect, the supply position of the fluid can be changed according to the position where the mass of methane hydrate is clogged in the pipe.

  A hydrate collection method according to a seventh aspect of the present invention is a hydrate collection method for collecting methane hydrate from the bottom of water, wherein methane rises in water from an inlet provided below a hydrate riser pipe. A hydrate lump is put, water in which methane gas is not dissolved to a saturated state is injected into a pipe deeper than the water depth of 400 m of the hydrate riser pipe, and the methane hydrate lump rising in the water in the pipe is added to the hydrate It takes out from the taking-out part provided above the rate riser.

  According to this aspect, there exists an effect similar to a 1st aspect.

  In addition, methane gas generated by the decomposition of methane hydrate in a region shallower than 400 m in water depth becomes a bubble and exhibits a gas lift effect that supports the buoyancy of the methane hydrate lump. Thereby, the upward movement of the methane hydrate lump becomes smoother, and the methane hydrate lump on the bottom of the water can be efficiently collected.

The schematic block diagram which shows an example of the hydrate sampling device which concerns on this invention. The figure explaining the lump of the hydrate which moves up and moves underwater. The schematic block diagram which shows the other example of the hydrate sampling device which concerns on this invention.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.
In the following description, two embodiments of Example 1 and Example 2 are taken as examples, and the schematic configuration of the hydrate sampling apparatus according to Example 1 will be described first.
Next, a hydrate sampling method using the hydrate sampling apparatus according to the first embodiment and the operation thereof will be described, and then a second embodiment as another example of the hydrate sampling apparatus will be described.

[Example 1]
<Schematic configuration of hydrate sampling device>
A schematic configuration of the hydrate sampling apparatus will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of a hydrate sampling apparatus according to the present invention.
As shown in FIG. 1, in this embodiment, a case where a methane hydrate lump GH is collected by excavating a surface type methane hydrate layer 14 on the sea bottom 12 (water bottom) will be described. The methane hydrate layer 14 is excavated by an excavator 40 having a drill or a bucket. The excavator 40 is driven by a driving source 42 provided near the sea floor by the support ship 18.
The methane hydrate lump GH separated from the methane hydrate layer 14 by excavation by the excavator 40 is recovered by the hydrate sampling apparatus 10 according to the present invention.

The hydrate collecting apparatus 10 has a hydrate riser pipe 20 (hereinafter simply referred to as a pipe) having an inlet portion 22 for receiving a methane hydrate mass GH rising in water and having an outlet portion 24 for the methane hydrate on the upper side. 20).
The methane hydrate recovery ship 16 is a ship that recovers the methane hydrate lump GH from the take-out unit 24.

  For example, a riser pipe can be used as the hydrate riser pipe 20. The inlet portion 22 is preferably formed in a tapered shape so that the methane hydrate lump GH can be easily inserted. The hydrate riser 20 shown in FIG. 1 has the same diameter from the bottom to the top except for the tapered inlet portion 22, but may be configured such that the pipe diameter increases as it goes upward.

  Further, the hydrate collecting apparatus 10 includes an injection unit 26 that injects water W1 in which methane gas is not dissolved to a saturated state into a pipe in a region deeper than the water depth 400 m of the hydrate riser pipe 20. In this embodiment, a plurality of injection ports 28 a, injection ports 28 b, and injection ports 28 c are provided as the injection portion 26 in the vertical direction of the hydrate riser 20.

The injection part 26 is provided so that the injection amount of the water W1 from each injection port (injection port 28a, injection port 28b, injection port 28c) can be adjusted.
In addition, it is desirable that the injection port of the injection portion 26 is provided at least at the position of the lower end portion of the hydrate riser 20. In the present embodiment, the inlet 28 a is located at the lower end of the hydrate riser 20.

The saturation of the water W1 in which the methane gas is not dissolved to the saturation state may be a saturation that allows the methane gas to be further dissolved, and may be less than 100%, preferably 50% or less, more preferably 10% or less. It is.
As the water W1 in which the methane gas is not dissolved until saturation, seawater of the same sea where the methane hydrate layer 14 exists can be used. Since the water W0 existing in the vicinity of the methane hydrate layer 14 is substantially saturated with methane, for example, in a region away from directly above the methane hydrate layer 14 and other methane hydrate layers (not shown). Seawater may be used as the water W1.
In the present embodiment, the first water supply means 30 such as a pump provided by the support ship 18 is provided in a region near the seabed 12 that is a distance R away from the end of the methane hydrate layer 14 along the seabed 12. ing. Moreover, the 1st water supply means 30 can also be provided in the area | region away above the methane hydrate layer 14 (direction approaching the sea surface).
The above is the schematic configuration of the hydrate sampling apparatus 10, and the hydrate sampling method using the apparatus 10 will be described below.

<Hydrate collection method>
Next, the operation of the hydrate sampling method using the hydrate sampling apparatus 10 will be described with reference to FIGS. FIG. 2 is a diagram illustrating a hydrate lump that moves up and down in water.

As described above, the methane hydrate lump GH excavated by the excavator 40 and separated from the methane hydrate layer 14 enters the hydrate riser 20 through the inlet 22. The methane hydrate lump GH having a density lower than that of seawater (small specific gravity) rises in the water in the pipe and is taken out from the upper takeout unit 24.
The methane hydrate lump GH is desirably collected as the largest lump L that can pass through the hydrate riser 20, but usually a small lump S (grains) is also formed when drilling with a drill or the like. Both L and the small mass S enter the inlet 22.

  Here, the water W <b> 1 in which the methane gas is not dissolved to the saturation state is injected into the hydrate riser pipe 20 from the injection portion 26 of the hydrate sampling apparatus 10. The effects obtained by the injection of the water W1 will be described below.

  In the water W0 existing near the methane hydrate layer 14 on the seabed 12, methane gas is dissolved to a substantially saturated state, and the methane hydrate is not normally decomposed in a portion deeper than a water depth of 400 m that satisfies the methane hydrate generation condition.

  On the other hand, when the mass GH of methane hydrate rises in the hydrate riser 20 to a depth of less than 400 m, decomposition begins because the pressure and temperature in the sea are outside the conditions for producing methane hydrate. At this time, if there are many small methane hydrate lumps S described above, the small lumps S are easily decomposed because of their large specific surface area, and excessive bubbles 50 of cracked gas (methane gas) are generated in the water in the tube 20. May be. In addition, since the pressure decreases and the volume of the bubbles 50 increases as the water depth becomes shallower, the proportion of the bubbles 50 in the tube 20 may increase so much that the rise of the methane hydrate lump GH may be hindered.

  Here, since the inlet portion 22 is in the vicinity of the methane hydrate layer 14 on the seabed, water W0 in which methane gas is saturated enters the hydrate riser pipe 20 from the inlet portion 22, but a pipe in a region deeper than the water depth of 400 m. When water W1 in which methane gas is not dissolved to a saturated state is injected into 20, the methane concentration in the water in the pipe 20 can be lowered.

When the methane concentration in the water in the hydrate riser 20 decreases, the methane lumps GH are decomposed even if the pressure and temperature are the conditions for producing methane hydrate.
At this time, the lumps S (grains) having a small methane hydrate are easily decomposed as described above, and thus almost disappear due to the decomposition at this time (in FIG. 2, the disappeared small lumps S are indicated by dotted lines). Methane gas generated by this decomposition dissolves in water W2 under high pressure (pressure in a region deeper than 400 m).

On the other hand, the mass L with a large methane hydrate stops with only a slight decomposition of the surface, and is an endothermic reaction, so that ice 52 is formed on the surface of the methane hydrate mass L [the bottom mass in FIG. State (a)].
In this state, the methane hydrate lump GH (large lump L) rises in the tube 20 by buoyancy. That is, the mass of methane hydrate in the pipe 20 rises as a collection of large masses L with little small masses S. And if it raises to the area | region shallower than 400 m of water depth, since the production | generation equilibrium (pressure) of methane hydrate will become a decomposition | disassembly condition, the surface of the lump L will start decomposition | disassembly. At the same time, ice 52 is further generated by decomposition endotherm [the state of the middle lump (b) in FIG. 2], and together with the ice 52 previously formed on the surface in a region deeper than the water depth of 400 m, a lump of methane hydrate L Is covered with a film of ice 52 [the state of the top lump (c) in FIG. 2]. Thereby, the decomposition reaction of methane hydrate stops due to the self-preserving effect.
Moreover, since the small methane hydrate lump S (grains) has already been decomposed and almost disappeared as described above, there is a risk that the small lump S (grains) will decompose and generate methane gas in this shallow region. Reduced.

  Accordingly, by injecting water W1 in which the methane gas is not dissolved to the saturated state into the pipe 20 in a region deeper than the water depth 400m of the hydrate riser pipe 20 from the injection portion 26, the water depth at which the methane hydrate becomes the decomposition condition is reduced. The amount of methane gas generated by the decomposition of methane hydrate can be reduced at the stage where it has risen to a shallow region (region having a water depth of less than 400 m).

  In addition, the volume of gas generated in shallow regions is large, so if a large amount of methane gas is generated at a stretch in that region, the volume occupied by bubbles in water in the hydrate riser tube becomes excessive, which causes methane hydrate. There is a possibility that the smooth movement of the rate lump GH may be hindered. In the present invention, since the amount of methane gas generated by methane hydrate decomposition is reduced in that region, the risk can be reduced.

  Also, the methane gas generated until the film of ice 52 is formed and the decomposition stops forms bubbles 50 and forms an upward flow (arrow A), and the buoyancy of the methane hydrate lump GH (mainly large lump L). Demonstrate gas lift effect to support. Thereby, the upward movement of the methane hydrate lump GH becomes smoother. Accordingly, it is possible to efficiently collect the methane hydrate lump GH at the bottom of the water.

In addition, it is preferable that the temperature of the water W1 (the methane gas is not dissolved to the saturated state) injected from the injection unit 26 of the hydrate sampling apparatus 10 is lower. This is because, under high pressure, the lower the temperature of water, the higher the solubility of methane gas.
Accordingly, the first water supply means 30 is preferably provided at a deep water depth, for example, near the seabed 12. In addition, since the big change of water temperature will decrease when it becomes a certain depth, the position which provides the 1st water supply means 30 according to the surrounding water temperature can be changed.

Moreover, it is preferable to inject | pour the water W1 in which methane gas is not melt | dissolving to a saturated state from the position of the lower end part of the hydrate riser pipe 20 at least. That is, it is preferable to carry out at least from the injection port 28a of the injection part 26.
This makes it possible to increase the distance from the injection position of the water W1 until the pressure and temperature in the hydrate riser 20 reach a water depth of 400 m, which is a decomposition condition for methane hydrate. Therefore, the mass S having a small gas hydrate can be reliably decomposed before the decomposition in the region shallower than the water depth of 400 m starts.

  Further, by gradually injecting water W1 into the pipe 20 from the plurality of inlets 28a, inlets 28b, and inlets 28c, the gas hydrate lump GH is decomposed in the vicinity of one inlet. Can be prevented.

In addition, the size of the excavated methane hydrate lump GH and the size ratio of the lump vary depending on the state of the methane hydrate layer 14 to be excavated, the environment in the sea, the type of the excavator 40, and the like. Therefore, the amount of water W1 injected from each of the plurality of inlets 28a, inlets 28b, and inlets 28c provided in the vertical direction can be adjusted, for example, according to the amount of small lump S generated when excavating. . More specifically, when there are many small lumps S, the injection amount of water can be increased and the small lumps S can be reliably decomposed.
Further, the injection amount can be adjusted by the methane saturation of the water W1 in which the methane gas is not dissolved to the saturation state. For example, in the case of water W1 that is not saturated but has a high degree of saturation, the injection amount can be increased, and in the case of water W1 that has a low degree of saturation, the injection amount can be adjusted to be small.

[Example 2]
In the second embodiment, another embodiment of the hydrate sampling apparatus will be described with reference to FIG. FIG. 3 is a schematic configuration diagram showing another example of the hydrate sampling apparatus according to the present invention.
In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description of the components is omitted.

The hydrate sampling apparatus 60 according to the present embodiment includes a fluid supply unit 34 that supplies fluid into a pipe in a region shallower than the water depth 400 m of the hydrate riser pipe 20.
A plurality of supply ports of the fluid supply unit 34 are provided in the vertical direction of the hydrate riser 20. In this embodiment, a supply port 36a, a supply port 36b, and a supply port 36c are provided.

Examples of the fluid include water (liquid) such as seawater and lake water, and air (gas).
In the hydrate riser 20, ice is generated due to decomposition and endotherm of methane hydrate, and the methane hydrate lump GH that moves upward may be clogged. In such a case, for example, by supplying water W3 (fluid) having a temperature higher than that of the water in the pipe 20 into the pipe 20, the ice formed on the surface of the clogged methane hydrate and the methane hydrate lump. The clogging can be resolved by decomposing.
In this embodiment, the water near the sea surface (temperature is high) is sent to the supply port 36a, the supply port 36b, and the supply port 36c by the second water supply means 32 such as a pump.

Note that methane hydrate can be decomposed even when water in which methane gas is not dissolved to saturation is used as water supplied from the fluid supply unit 34.
In the present embodiment, water is supplied as a fluid from the fluid supply unit 34, but clogging can be eliminated by temporarily blowing a gas such as air as the fluid.

Further, in this embodiment, water W3 can be injected into the pipe 20 from the plurality of supply ports 36a, supply ports 36b, and supply ports 36c, so that the water W3 according to the position where the methane hydrate lump GH is clogged in the pipe 20. The feeding position can be changed.
If clogging occurs in a pipe deeper than 400 m, the position of the first water supply means 30 (water depth) is changed to a position closer to the sea surface, and hot water is poured from the injection section 26. It is also possible to break up clogged methane hydrate and eliminate clogging.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. .

10 Hydrate sampling device, 12 seabed, 14 methane hydrate layer,
16 hydrate recovery vessels, 18 support vessels,
20 hydrate riser pipe, 22 inlet part, 24 take-out part, 26 injection part 28a, 28b, 28c inlet, 30 first water supply means,
32 2nd water supply means, 34 Fluid supply part, 36a, 36b, 36c Supply port,
40 excavator, 42 drive source, 50 bubbles, 52 ice, 60 hydrate sampling device W0 water saturated with methane gas,
W1, water in which methane gas is not dissolved to saturation,
W2 Water in the hydrate riser,
W3 Water whose temperature is higher than W1

Claims (7)

A hydrate collector for collecting methane hydrate from the bottom of the water,
A hydrate riser pipe having an inlet portion for receiving a mass of methane hydrate rising in the water at the bottom, and an extraction portion for the methane hydrate at the top;
An injection part for injecting water in which the methane gas is not dissolved to a saturated state into a pipe in a region deeper than the water depth of 400 m of the hydrate riser pipe ,
The injection port of the injection part is provided above the inlet part, and vertically so as to inject water stepwise into the pipe in the region from the lower end side of the hydrate riser pipe to a water depth of 400 m. It characterized that you have provided a plurality hydrate collection device. The hydrate collection device according to claim 1,
One of the plurality of injection ports of the injection unit is provided at a position of a lower end portion of the hydrate riser pipe. The hydrate sampling device according to claim 2,
  The other one of the plurality of injection ports of the injection unit is provided at a position closer to a water depth of 400 m than the water bottom in the hydrate riser pipe. In the hydrate sampling device according to any one of claims 1 to 3,
The hydrate sampling apparatus according to claim 1, wherein the injection section is capable of adjusting an amount of water injected from each inlet. In the hydrate sampling apparatus according to any one of claims 1 to 4,
A hydrate collecting apparatus comprising a fluid supply unit for supplying fluid into a pipe in a region shallower than a water depth of 400 m of the hydrate riser pipe. In the hydrate sampling apparatus according to claim 5,
2. A hydrate sampling apparatus according to claim 1, wherein a plurality of supply ports of the fluid supply unit are provided in a vertical direction. A hydrate collecting method for collecting methane hydrate from the bottom of water,
From the inlet provided below the hydrate riser pipe, put a mass of methane hydrate rising in the water,
Stepwise from an inlet provided in the vertical direction with a plurality of water in which the methane gas is not dissolved to a saturated state in a pipe in a region above the inlet part and from the lower end side of the hydrate riser pipe to a water depth of 400 m. injected into,
A method for collecting hydrate, characterized in that a mass of methane hydrate rising in the water in the pipe is taken out from a take-out section provided above the hydrate riser pipe.

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