JP2006037518A - Gas hydrate collecting method and gas hydrate collecting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas hydrate collecting method and a gas hydrate collecting system capable of stably collecting a gas hydrate in large quantity. <P>SOLUTION: An excavation object including sediment and the gas hydrate is provided while advancing the boring of a hydrate layer G2 by an excavator-agitator 10. The excavation object is mechanically agitated by the excavator-agitator 10, and the gas hydrate (and seawater) are recovered from the inside of the excavation object, and recovered by a ship and a base positioned on the sea via a shaft 1. When agitating the excavation object, the gas hydrate, the seawater and the sediment can be separated by its specific gravity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas hydride collection method and a gas hydride collection system.

In recent years, gas hydrates present in the seabed have attracted attention as natural resources. The gas hydrate is a gas mainly composed of methane. Gas hydrate is in the sand layer ground (hereinafter sometimes referred to as hydrate layer) having a layer thickness of 10 to 20 m in the seabed ground several hundred meters below the seabed located at a depth of 500 to 1000 m or more. In the voids between particles such as sand, they are condensed in a sherbet shape.
The goal is to collect gas hydrate and use it on a commercial basis in the near future. At present, the area where gas hydrate exists is being investigated.

Until now, in order to collect the gas hydrate from the seabed ground, the gas hydrate is decomposed by breaking the conditions for condensing the gas hydrate, gasified or liquefied, and then collected through a pipe or the like. In order to break the conditions for the gas hydrate to condense, it is necessary to apply heat to increase the temperature or decrease the pressure.
For this reason, in the past, vertical or horizontal production holes were constructed based on existing oil and natural gas production methods, and the gas hydrate was decomposed by depressurizing or heating the production holes. A method for recovering the wastewater has been studied in the mainstream. As another method, a method of adding warm water from one of the two horizontal holes and recovering the decomposed gas from the other has been studied.

  In addition, a method for collecting gas hydrate exposed on the sea floor by causing the conduit to reach the sea floor from the sea and applying heat or reducing the pressure at the tip thereof has already been proposed (for example, Patent Document 1). reference.).

Special table 2000-513061 gazette

  However, the technique of constructing a production hole in the seabed ground and reducing or heating the production hole is less effective for reducing or heating to a position away from the production hole. In addition, even if the gas hydrate is gasified or liquefied due to the effect of reduced pressure or heating far from the production hole, the gas must propagate through the hydrate layer to the production hole, and the collection efficiency Is extremely low.

  In addition, the method described in Patent Document 1 is a method of collecting gas hydrate exposed to the seabed to the last, and the gas hydrate from the hydrate layer located in the seabed ground several hundred meters below the seabed surface. It is not intended for collection.

Furthermore, in the first place, these methods collect gas hydrate from a specific point. Such a method is suitable for research and research purposes, such as when investigating the presence of gas hydrates, but it is not practical when trying to secure a production level at a commercial base level. In such a case, it is necessary to collect a large amount of gas hydrate from a wide range. In the conventional method, the points to be collected must be moved sequentially, which is time consuming and costly, and furthermore, collection cannot be performed while the points are moving, which hinders the stable supply of collected gas. Because there is a fear of coming.
The present invention has been made based on such a technical problem, and provides a gas hydride collection method and a gas hydride collection system capable of collecting a large amount of gas hydrate stably. Objective.

For this purpose, the gas hydrate collecting method of the present invention is a method for collecting gas hydrate from a hydrate layer that exists in the seabed and contains gas hydrate, and excavates the hydrate layer. The excavation process for obtaining excavated material including gas hydrate and earth and sand, and the agitation and separating process for mechanically agitating the excavated material to generate a mixture of gas hydrate and earth and sand, and further separating the gas hydrate and earth and sand And a recovery step of recovering the separated gas hydrate.
Here, in the stirring separation step, the gas hydrate and the earth and sand can be separated due to the difference in specific gravity between the gas hydrate and the earth and sand.
The stirring / separating step is preferably performed in the hydrate layer. And it is preferable that the earth and sand isolate | separated by the stirring separation process are refilled in a hydrate layer.

Further, in the excavation process, it is preferable to continuously excavate the hydrate layer in the lateral direction. For this purpose, it is preferable to continuously excavate in the lateral direction as in the case of excavating the tunnel. Further, the hydrate layer can be excavated and gas hydrate can be collected from the obtained excavated material by turning the excavator in the lateral direction around a predetermined position in the hydrate layer. In this way, gas hydrate can be collected from a wide range of hydrate layers.
Moreover, in order to obtain gas hydrate, when an excavation pit is formed in the hydrate layer in the excavation process, the outer peripheral side of the excavation pit can be further excavated, and gas hydrate can be collected from the obtained excavated material. As a result, a large section is excavated and a larger amount of gas hydrate is collected. Also in this case, the obtained excavated material is subjected to the stirring separation process and the recovery process in the same manner, and gas hydrate is collected.

The present invention can also be regarded as a gas hydrate collection system for collecting gas hydrate from a hydrate layer that exists in the seabed ground and includes gas hydrate. This system excavates a hydrate layer and obtains an excavated material containing gas hydrate and earth and sand, an agitation device that mechanically agitates the excavated material, And a recovery device for recovering the separated gas hydrate.
At this time, it is preferable that the excavator excavates the forward hydrate layer while moving forward like a tunnel boring machine (TBM) or a shield excavator.
A screw conveyor can be used for the excavator. By advancing while rotating the screw member of the screw conveyor, excavation and conveyance of excavated material can be performed.
When the excavator is to excavate the forward hydrate layer while moving forward like a TBM or shield excavator, the agitator can be provided integrally with the excavator.
Further, the agitator may be installed (fixed) behind the excavator in the traveling direction, and the excavator may be conveyed from the excavator to the agitator by the conveying device.

  ADVANTAGE OF THE INVENTION According to this invention, a gas hydrate can be collect | recovered from excavated material by excavating a hydrate layer, obtaining the excavated material containing earth and sand and gas hydrate, and stirring this mechanically. And by excavating the hydrate layer continuously in the lateral direction as if excavating a tunnel, a large amount of gas hydrate can be continuously collected from a wide range of hydrate layers. As a result, a large amount of gas hydrate can be collected stably.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings. In the following, a plurality of embodiments will be shown, but the same reference numerals are given to components common to the respective embodiments, and the description thereof may be omitted.

[First embodiment]
FIG. 1 is a diagram for explaining a gas hydrate collection method and a gas hydrate collection system according to the first embodiment.
As shown in FIG. 1, in the present embodiment, a vertical shaft 1 is constructed from the sea to the hydrate layer G2 in the seabed ground G1, and an excavator agitator (excavator, agitator) is formed from the bottom of the vertical shaft 1. ) 10 is propelled laterally into the hydrate layer G2. Then, the excavator and agitator 10 collects the earth and sand of the formation (sand layer) constituting the hydrate layer G2 and the gas hydrate excavated matter mixed in the earth and sand. Further, the excavator agitator 10 mechanically agitates the collected excavated material, collects gas hydrate (and seawater) from the excavated material, passes this through the vertical shaft 1, and is used by a ship or base located on the sea. to recover. It is also possible to separate the gas hydrate and seawater on the seabed, etc., further gasify or liquefy the gas hydrate, and send it through a pipeline laid on the seabed. In the present embodiment, there is no limitation on the method by which the collected gas hydrate is conveyed.

In this manner, the gas hydrate is recovered by propelling the excavator stirrer 10 in the lateral direction with the hydrate layer G2 so as to excavate the tunnel.
Here, FIG. 2 is a plan view showing an example of the excavation pit T (propulsion locus L) excavated by the excavator agitator 10 in the hydrate layer G2. As shown in FIG. 2, the gas hydrate is recovered from the hydrate layer G2 in a wide range by scanning the excavator agitator 10 in various directions in the hydrate layer G2 with the vertical shaft 1 as a base point. The propulsion locus L shown in FIG. 2 is an example when two shafts 1 are constructed. Of course, the excavator agitator 10 can be propelled in other patterns, and the number of shafts 1 Or one or three or more.

  Further, after the excavation stirrer 10 forms the excavation pit T, heat is applied to the excavation pit T or decompression is performed, so that the gas hydrate is decomposed in the hydrate layer G2 around the excavation pit T. It can also be made. The decomposed gas hydrate can be collected through the excavation pit T.

FIG. 3 shows an example of the excavator stirrer 10 used when collecting the gas hydrate as described above.
As shown in FIG. 3, the excavator agitator (excavator, agitator) 10A basically has a configuration such as a tunnel boring machine, and a drill 11 for excavation provided at the tip portion and the drill 11 are driven to rotate. A stirrer 13 for stirring the excavated material excavated by the drill 11 and separating the gas hydrate from the excavated material, a motor 14 serving as a drive source of the stirrer 13, and the gas hydrate separated by the stirrer 13 A pump (collecting device) 16 for sending the rate backward through a flexible tube (conveying device) 15 is provided.

  When the drill 11 is rotated, the excavator agitator 10A obtains a propulsive force by the force that the blade of the drill 11 bites into the hydrate layer G2. In order to receive the reaction force of this propulsive force, the excavator agitator 10A includes a gripper 17 that is pressed against the pit wall surface 100 formed by excavation. Further, the flexible tube 15 can be extended as the excavator agitator 10A advances.

Such an excavator agitator 10A excavates the hydrate layer G2 ahead of the traveling direction with the drill 11, and takes the sediment and gas hydrate excavated material from the formation back. The configuration of the drill 11 itself can be the same configuration as that of a normal drill for ground excavation, and since there is no intention to limit the configuration in particular, the description thereof is omitted here.
The excavated material taken in by the drill 11 is stirred by the stirring member 13 a of the stirring device 13. As a result, the excavated material is finely crushed and becomes a mixture in which gas hydrate, seawater (ice), earth and sand, and respective particles are mixed. At this time, the excavated material that has been in a large lump shape is also finely crushed, so that the gas hydrate contained in the lump also becomes particles. Here, the particle diameter is determined by the stirring time such as the pitch of the stirring member 13a and the like, and here, a particle diameter of about several centimeters to several tens of centimeters is assumed.

  Gas hydrate, seawater (ice), and earth and sand particles are gradually different in specific gravity as they continue to be stirred (gas hydrate: 0.9, seawater: 1.03, earth and sand: about 2.6). Thus, gas hydrate and seawater are separated into earth and sand. Thereby, gas hydrate and seawater float on the upper part of the stirring device 13, and earth and sand settle on the lower part.

  The gas hydrate and seawater separated from the earth and sand are sent out from the pipe 18 connected to the upper part of the stirring device 13 to the rear flexible tube 15 by the pump 16. And it is sent to the sea etc. through the vertical tube 1 through the flexible tube 15. On the other hand, the remaining earth and sand are discharged rearward from the lower part of the stirring device 13, and the excavation mine T formed in the hydrate layer G2 is refilled as it is.

  By the way, excavation / stirring / separation as described above is performed in parallel with the excavation (advance) of the excavator agitator 10A. Therefore, for example, the excavated matter taken in by the drill 11 is started when the agitator 13 reaches the position of the excavated material from behind by the excavation of the excavator agitator 10A, and the position of the excavated matter is changed to the agitator 13. The stirring is completed by passing. And the earth and sand from which the gas hydrate and seawater have been separated by stirring are also left in the excavation mine T as they pass through the stirring device 13. Of course, it is possible to use a pump or the like to feed the excavated material from the drill 11 to the stirring device 13 and discharge the earth and sand from the stirring device 13 to the rear, but the above-described configuration can also be used.

  In this manner, the hydrate layer G2 is excavated with the excavator agitator 10A to obtain an excavated material including earth and sand and gas hydrate, and this is mechanically agitated, so that the gas hydrate ( And seawater). By excavating the hydrate layer G2 while excavating the tunnel while moving the excavator agitator 10A forward, a large amount of gas hydrate can be collected continuously from a wide range of hydrate layers G2. As a result, the productivity of gas hydrate is greatly improved and stable production is possible.

  FIG. 4 is a modification of the excavator stirrer 10A of FIG. The excavator agitator (excavator, agitator) 10B shown in FIG. 4 is obtained by adding a propulsion jack 20 to the excavator agitator 10A of FIG. The propulsion jack 20 is provided between the drill 11 side and a receiving member 21 provided between the grippers 17 and 17. In such excavator stirrer 10B, the drill 11 can be propelled forward by extending the propulsion jack 20 with hydraulic pressure or the like while the grippers 17 and 17 are pressed against the pit wall surface 100. Thereby, even if the propulsive force is insufficient only by the biting force of the drill 11 depending on the state of the hydrate layer G2 in the front, a large propulsive force can be applied to the excavator agitator 10B.

  FIG. 5 shows an example of an excavator agitator (excavator, agitator) 10 </ b> C provided with a cutter face 30 instead of the drill 11. This excavator agitator 10C includes a disc-shaped cutter face 30 instead of the drill 11 in the excavator agitators 10A and 10B shown in FIGS. The cutter face 30 is rotationally driven by the motor 12 and has a plurality (large number) of excavation bits 30a on the front surface thereof. Such a cutter face 30 can be applied with a configuration similar to that used in shield excavators and the like, and since there is no intention to limit the configuration in particular, further description thereof is omitted here.

In addition, the excavator agitator 10C includes a propulsion jack 31 that is extended and contracted by hydraulic pressure or the like between the grippers 17f and 17r that move forward and backward. The front gripper 17f is connected to the cutter face 30 side, and the rear gripper 17r is connected to the main body side of the stirring device 13 and the like.
When the cutter face 30 is moved forward, while the cutter face 30 is rotated by the motor 12, the propulsion jack 31 is extended with the front gripper 17f being released from being pressed against the wall surface 100, and the front gripper 17f and the cutter face 30 are moved. Move forward. Thereby, the forward hydrate layer G2 is excavated. When the predetermined stroke is advanced, the front gripper 17f is pressed against the pit wall surface 100, and then the pressing of the rear gripper 17r to the pit wall surface 100 is released. And the propulsion jack 31 is shrunk and main bodies, such as the rear gripper 17r and the stirring apparatus 13, are advanced. Thereafter, the rear gripper 17r is pressed against the well wall surface 100.
By repeating such an operation, the propulsion jack 31 moves the cutter face 30 forward and retracts the main body of the stirring device 13 and the like. As a result, the pulling-in of the stirring device 13 and the like does not depend on the frictional force between the cutter face 30 and the face surface, so that there is little influence due to the state of the hydrate layer G2, and the construction can be performed stably.

  Of course, the configuration shown in FIG. 5 can be similarly applied to the case where the drill 11 is provided instead of the cutter face 30, but the excavation control is facilitated by providing the cutter face 30.

  The excavator agitator (excavator, agitator) 10D shown in FIG. 6 includes a rotation preventing member 40 in place of the gripper 17. As shown in FIG. 6, the rotation preventing member 40 includes a plurality of rollers 41 that are rotatable in the digging direction (front-rear direction) of the digging stirrer 10D. When the drill 11 rotates and digs into the hydrate layer G2 while digging into the hydrate layer G2, the roller 41 rotates to suppress its propulsion resistance, and against the rotational reaction force of the drill 11, the roller 41 and the pit. A drag is exerted by friction with the wall surface 100 to prevent the rear stirring device 13 and the like from rotating together.

[Second Embodiment]
FIG. 7 is a diagram showing the excavator 50 in the second embodiment. As shown in FIG. 7, the excavator 50 includes a drill 11, a motor 12, a pump 16, a gripper 17, and the like. The excavator 50 includes a screw conveyor (conveyor) 51 for excavating the drill 11 with the drill 11 and supplying the excavated material taken backward to the pipe 18 connected to the pump 16. In this excavator 50, the excavated material taken in from the hydrate layer G2 is sent out from the pump 16 toward the flexible tube 15 at the rear.
When using such an excavating device 50, as shown in FIG. 8, the stirring device 60 is installed in the vertical shaft 1. In the agitator 60, the excavated material fed from the excavator 50 through the flexible tube 15 is agitated by the agitating member 60a. Then, like the stirring device 13 shown in FIG. 3, the excavated material is finely crushed and becomes a mixture of gas hydrate, seawater (ice), earth and sand, and respective particles. Gas hydrate, seawater (ice), and earth and sand particles are different in specific gravity (gas hydrate: 0.9, seawater: 1.03, earth and sand: about 2.6). And separated into earth and sand.

The vertical shaft 1 is provided with a pipe 52 for recovering gas hydrate and seawater to the sea or the like. Further, the stirring device 60 is provided with a screw conveyor 53 for backfilling the earth and sand. Thereby, the gas hydrate and seawater separated by the stirring device 60 are sent out toward the sea etc. through the pipe 52. Moreover, the earth and sand remaining by separating the gas hydrate and seawater with the stirring device 60 is backfilled into the seabed ground by the screw conveyor 53.
Here, the screw conveyor 53 is installed and the earth and sand are backfilled in other excavation pits T already excavated by the excavator 50.

  In such a configuration, since the excavator 50 does not include the agitator 13 or the like, the excavator 50 may be more compact and lighter than the excavator agitators 10A to 10D illustrated in FIGS. it can. By making the excavator 50 compact, the flexibility of the excavator 50 (degree of freedom in the excavation direction) is increased, and by reducing the weight, the risk of subsidence of the excavator 50 into the hydrate layer G2 can be reduced. it can.

  In addition, the excavation apparatus 50 does not dig up the earth and sand generated while backfilling the excavation pit T behind the excavation apparatus 50, but backfills it into another excavation mine T or the like. When a failure occurs in the excavator 50, the excavator 50 can be reached through the excavation pit T, and repair or maintenance work can be performed.

FIG. 9 shows an application example of the configuration shown in FIG. As shown in FIG. 9, a circulation pump 70 and a circulation pipe 71 can be provided in a pipe 52 for sending gas hydrate and seawater toward the sea or the like from a stirring device 60 installed in the vertical shaft 1. In such a configuration, part of the gas hydrate and water sent out from the stirring device 60 is taken into the circulation pipe 71 and circulated in the pipe 52 by the circulation pump 70.
By doing so, the gas hydrate and water pumped and circulated in the pipe 52 by the circulation pump 70 collide with the gas hydrate and water flowing in the pipe 52, and an upward flow is further generated in the pipe 52. Occurs (accelerated). Thereby, the earth and sand which could not be separated by the stirring device 60 but were sent into the pipe 52 together with the gas hydrate and water can be separated here. As a result, it is possible to reduce the proportion of earth and sand mixed in the gas hydrate recovered at sea or the like, that is, improve the gas hydrate recovery efficiency.

In the first and second embodiments as described above, various configurations can be changed, added, omitted, and the like.
For example, as shown in FIG. 10, the cutter face 30 shown in FIG. 5 is provided with a nozzle 31, and water pumped from the pump 32 may be sprayed from the nozzle 31 to the hydrate layer G2 ahead (so-called water). jet). In this way, the forward hydrate layer G2 is loosened, the excavation resistance of the cutter face 30 can be reduced, the rotational speed of the cutter face 30, that is, the excavation speed can be improved, and the productivity can be increased.
Furthermore, as shown in FIG. 11, the water pumped by the pump 32 may be heated by a heat source 33 such as a heater and the hot water may be ejected from the nozzle 31. In this way, decomposition of the gas hydrate can be promoted in the forward hydrate layer G2. Furthermore, when decomposition of the gas hydrate occurs in the hydrate layer G2, the hydrate layer G2 also loosens, so that the excavation speed can be further improved and the productivity can be increased.

[Third embodiment]
Now, after the excavation pit T is formed by the method shown in the first and second embodiments, the excavation pit T is used as a pilot pit, and a larger diameter excavation is performed to collect gas hydrate from a wider range. You can also
For example, a configuration as shown in FIG. 12 can be applied.
As shown in FIG. 12, a gripper 81 of a large-diameter excavator (excavator) 80 and a propulsion jack 82 are installed in the excavation pit T that has already been formed. A large-diameter excavating portion 83 is connected to the rear gripper 81. The large-diameter excavation part 83 is driven to rotate by a motor 84 and excavates the hydrate layer G2 on the outer peripheral side of the excavation pit T with an excavation bit 83a provided on the surface thereof.
Further, in this large-diameter excavator 80, the large-diameter excavating portion 83 is formed by expanding and contracting the propulsion jack 82 while pressing and releasing the grippers 81 provided before and after the propulsion jack 82 against the pit wall surface 100. Can be advanced in the direction of the arrow in the figure.

Here, by providing a stirrer 85 including a stirring member 85a behind the large-diameter excavation part 83, the gas hydrate, seawater, and earth and sand removed from the hydrate layer G2 by the large-diameter excavation part 83 are provided. The drilling can be agitated to separate the gas hydrate and seawater. Moreover, in the stirring apparatus 85, the earth and sand remaining after gas hydrate and seawater isolate | separate are backfilled as it is back in a digging direction.
The separated gas hydrate and seawater can penetrate the large-diameter excavation part 83 and can be sent out through the flexible tube 15 laid toward the vertical shaft 1 (see FIG. 1). As this flexible tube 15, the one used when excavating the excavation pit T by the method as shown in the first and second embodiments can be used as it is.

With such a configuration, a wider area around the excavation pit T can be excavated, and a large amount of gas hydrate can be collected. In addition, by using the excavation pit T formed in advance as a pilot mine, the excavation mine T can be used for power supply used in the large-diameter excavator 80, a transport line for gas hydrate, and the like. it can.
Also in this case, the delivered excavated material can be agitated and separated by the agitator 60 installed in the shaft 1 as shown in FIG. 8 or FIG. 9, and the gas hydrate and seawater can be sent to the sea or the like. it can.

[Fourth embodiment]
The following configuration can also be adopted for the technique of excavating a large diameter after forming a small-diameter pilot mine.
FIG. 13 shows an excavator 90 that can be used for such a technique.
The excavator 90 includes a plurality of excavation bits 92 at the distal end of a main body 91, and two pairs of screw cutters 93 are rotatably supported by pins 94 on the base end side of the main body 91, for example.
Each screw cutter 93 is rotated around a pin 94 with respect to the main body 91 by a drive cylinder 95 and a link plate 96 provided between the drive cylinder 95 and the screw cutter 93. Each screw cutter 93 is driven to rotate about its axis by a drive mechanism 97.
Further, the main body 91 provided with the excavation bit 92 at the tip is also rotationally driven around its axis by a rotation driving mechanism (not shown).
The main body 91 collects the gas hydrate, seawater, and earth excavated material excavated by the excavating bit 92 or the screw cutter 93 as described later, and discharges it from the base end side of the main body 91. 98 and 99 are provided.

  In such excavator 90, as shown in FIG. 14 (a), first, propulsion (not shown) is performed while rotating the main body 91 with a rotary drive mechanism (not shown) while the screw cutter 93 is placed along the main body 91. The hydrate layer G2 is excavated with the excavation bit 92 at the tip. At this time, the excavated excavated material is recovered through the recovery tube 98 shown in FIG. 13A and is sent to the vertical shaft 1 through the rear excavation shaft T.

  When the excavation is completed to a predetermined position, each screw cutter 93 is driven to rotate around the axis by the drive mechanism 97, and the drive cylinder 95 is operated while the main body 91 is rotated by the rotation drive mechanism. The two screw cutters 93 are rotated around the pins 94. Then, as shown in FIG. 14B, the two screw cutters 93 excavate the hydrate layer G <b> 2 on the outer peripheral side of the excavation pit T while opening with respect to the main body 91. The excavated material excavated at this time is recovered from the recovery tube 99 opened in the intermediate portion of the main body 91, and is sent to the vertical shaft 1 through the rear excavation shaft T.

  When the two screw cutters 93 are opened to a predetermined angle, the excavator 90 is now retracted. Then, as shown in FIG.14 (c), the outer peripheral side of the excavation mine T is excavated by a larger cross section with the screw cutter 93, and excavated material can be collect | recovered.

  In the configuration as described above, the configuration shown in FIG. 8 or FIG. 9, that is, the excavated material is stirred and separated by the stirring device 60 installed in the vertical shaft 1, and the gas hydrate and seawater are sent to the sea or the like. it can.

[Fifth embodiment]
In this method, as shown in FIG. 15, a plurality of screw conveyors 200 are arranged around the shaft 1. Each screw conveyor 200 includes screw blades 201a, and includes a screw member 201 that is driven to rotate about its axis by a driving source (not shown).
Gas hydrate is collected while using such a screw conveyor 200 for excavation of excavated material and backfilling of earth and sand.

For this purpose, the screw member 201 is rotated while the screw conveyor (excavator) 200A used for excavation is advanced by a propulsion mechanism (not shown), and the front hydrate layer G2 is excavated at the tip of the screw member 201. To do. The excavated excavated material is conveyed backward by the rotating screw member 201. The excavated material is stirred and separated by the stirring device 60 installed in the vertical shaft 1, and the gas hydrate and seawater are sent to the sea through the vertical shaft 1.
At this time, as the screw conveyor 200A digs up, another screw conveyor 200A may be sequentially added to the rear, or the flexible tube 15 or the like as in the first to third embodiments. May be connected to the rear, and the excavated material may be conveyed to the vertical shaft 1 through the flexible tube 15.

  Now, the earth and sand remaining by separating the gas hydrate and seawater by the stirring device 60 is discharged to the screw conveyor 200B for backfilling. The screw conveyor 200B for backfilling can rotate the screw member 201 to convey the earth and sand discharged from the stirring device 60 and backfill the other excavation mine T and the like already excavated.

[Sixth embodiment]
In the first to fifth embodiments, the method of collecting gas hydrate while digging in one direction and forming the tunnel-shaped excavation mine T is exemplified, but other methods as shown below are also possible. Can be adopted.
That is, as shown in FIG. 16, excavation of the hydrate layer G2 while rotating the screw conveyor (excavator) 200A for excavation and the screw conveyor 200B for backfilling in a substantially horizontal direction around the stirring device 60. And the earth and sand are backfilled.
In this case, in the screw conveyor 200A for excavation, the hydrate layer G2 is excavated on the side surface (front in the turning direction) of the screw member 201 that is rotationally driven. The excavated excavated material is sent to the stirring device 60 by the screw member 201.
On the other hand, in the screw conveyor 200B for backfilling, in the process of conveying the earth and sand discharged from the stirring device 60 to the tip by the rotationally driven screw member 201 while turning in a substantially horizontal direction, Backfill).

  At this time, for example, a plurality of screw conveyors 200B for backfilling may be provided, or a plurality of screw conveyors 200A for excavation may be provided. However, when the number of screw conveyors 200A for excavation is increased, excavation resistance increases, and a load is applied to the driving force for turning these screw conveyors 200A and 200B. For this reason, it is preferable to set the number, length, etc. of these according to the output of the drive mechanism for turning these screw conveyors 200A and 200B.

For example, as shown in the fifth embodiment, the excavation of the hydrate layer G2 by such turning is performed after the excavation screw conveyor 200A is dug in one direction to form the excavation pit T. The excavation pit T can be used as a base point. That is, the screw conveyor 200A is turned from the position of the excavation mine T.
In this manner, the hydrate layer G2 around the excavation pit T can be excavated in a wide range, and the production amount of gas hydrate can be increased.

In the fifth or sixth embodiment, as shown in FIG. 17, a screw conveyor 200A for excavation and a screw conveyor 200B for backfilling are provided one above the other to perform excavation or swivel excavation. Is possible. In this case, the screw conveyor 200A for excavation is arranged in the upper stage, the screw conveyor 200B for backfilling is arranged in the lower stage, and the partition member 210 is provided between the two.
In this way, the excavated material excavated from the hydrate layer G2 by the excavating screw conveyor 200A is conveyed toward the stirring device 60 by the screw member 201, and the hydrate layer by the lower backfilling screw conveyor 200B. Backfilled to G2. At this time, in the stirrer 60, due to the specific gravity, the gas hydrate and seawater separated by stirring float upward, and the earth and sand sink downward. The earth and sand sinking downward is carried out of the stirring device 60 by the screw conveyor 200B for backfilling. In this way, by disposing the screw conveyor 200B for backfilling at the lower stage, it is possible to smoothly discharge and backfill the sediment that sinks downward due to the specific gravity. For this reason, it is preferable that the stirring member 60b of the stirring device 60 be rotationally driven in the lateral direction.

At this time, as shown in FIG. 18, a mesh member 220 having a large number of openings may be provided instead of the partition member 210.
The excavated material excavated from the hydrate layer G <b> 2 by the excavating screw conveyor 200 </ b> A is conveyed toward the stirring device 60 by the screw member 201. At this time, when the excavated material comes into contact with the mesh member 220 or is agitated by the rotating screw member 201, a part of the excavated material may be separated into gas hydrate, seawater, and earth and sand. Since the separated gas hydrate and seawater and earth and sand are divided into upper and lower parts by specific gravity, the earth and sand that sinks downward passes through the opening of the mesh member 220 and falls on the screw conveyor 200B for backfilling below. The fallen earth and sand are backfilled into the hydrate layer G2 by the screw conveyor 200B.
Accordingly, the excavated material can be conveyed and separated even during conveyance on the excavating screw conveyor 200A, and the efficiency is further improved.

By the way, the screw member 201 of the screw conveyor 200A for excavation is not limited to a normal spiral screw blade shape, but may be various other types.
For example, as shown in FIG. 19A, screw blades 230 having different lengths may be provided side by side on the screw member 201A. If it does in this way, the excavated material contacts the screw blade 230 while conveying the excavated material, the function of stirring is improved, and the separation efficiency of gas hydrate can be increased.
In addition, as shown in FIG. 19B or 19C, a bit 240 can be provided at the tip of a zigzag screw member 201B or a spiral screw member 201C. If it does in this way, excavation capability when it advances while rotating screw members 201B and 201C will improve, and it can raise productivity.
Furthermore, as shown in FIG. 19D, a bit 250 may be provided at the tip of the screw member 201D. Thereby, the initial insertion load when the screw member 201D bites into the forward hydrate layer G2 can be significantly reduced.
Of course, these may be combined, and other configurations may be employed.

  In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is an elevation sectional view for explaining roughly a gas hydrate collecting method in the present embodiment. It is a plane sectional view showing an example of excavation locus of an excavator. It is sectional drawing which shows the excavation stirrer in 1st embodiment. It is sectional drawing which shows the excavation stirrer provided with the propulsion jack. It is sectional drawing which shows the excavation stirrer provided with the cutter face. It is sectional drawing which shows the excavation stirrer provided with the rotation prevention member. It is sectional drawing which shows the excavation apparatus in 2nd embodiment. It is sectional drawing which shows the stirring apparatus used in 2nd embodiment. It is a figure which shows the modification of the structure of FIG. It is a figure which shows the example of the excavator provided with the water jet. It is a figure which shows the modification of the structure of FIG. It is sectional drawing which shows the excavator in 3rd embodiment. It is a figure which shows the excavator in 4th embodiment, (a) is sectional drawing of the direction orthogonal to the direction where a screw cutter opens, (b) is sectional drawing of the direction where a screw cutter opens. It is sectional drawing which shows the process of excavating using the excavator of FIG. In 5th Embodiment, it is sectional drawing which shows the structure which excavates using a screw conveyor. In 6th Embodiment, it is sectional drawing which shows the structure which turns a screw conveyor and excavates. It is sectional drawing which shows the example in the case of using a screw conveyor piled up on two steps up and down. FIG. 18 is a cross-sectional view illustrating a modification example of FIG. 17, in which a mesh member is provided between screw conveyors that are stacked in two upper and lower stages. It is a figure which shows the multiple examples of the shape of a screw member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vertical shaft 10, 10A, 10B, 10C, 10D ... Excavation stirrer (excavation apparatus, stirring apparatus), 13 ... Stirring apparatus, 15 ... Flexible tube (conveyance apparatus), 16 ... Pump (collection apparatus), 50 ... Drilling device 51 ... Screw conveyor (conveying device) 60 ... Stirring device 80 ... Large diameter drilling device (digging device) 85 ... Stirring device 90 ... Drilling device 200A ... Screw conveyor (digging device, excavator), G1 ... Submarine ground, G2 ... Hydrate layer, T ... Drilling mine

Claims (11)

A method for collecting the gas hydrate from a hydrate layer that exists in the seabed and includes gas hydrate,
A drilling step of drilling the hydrate layer to obtain a drilled object containing the gas hydrate and earth and sand;
Mechanically stirring the excavated matter to produce a mixture of the gas hydrate and the earth and sand, and further stirring and separating the gas hydrate and the earth and sand;
A recovery step of recovering the separated gas hydrate;
A gas hydrate collection method comprising:   2. The gas hydrate collecting method according to claim 1, wherein in the stirring and separating step, the gas hydrate and the earth and sand are separated based on a difference in specific gravity between the gas hydrate and the earth and sand.   The gas hydrate collecting method according to claim 1, further comprising a step of filling the earth and sand separated in the stirring separation step back into the hydrate layer.   The gas hydrate collection method according to any one of claims 1 to 3, wherein in the excavation step, the hydrate layer is continuously excavated in a lateral direction.   The gas hydrate collecting method according to claim 4, further comprising excavating an outer peripheral side of the excavation pit formed in the hydrate layer in the excavation step, and collecting gas hydrate from the obtained excavated material. .   In the excavation step, excavating the hydrate layer by turning an excavator laterally around a predetermined position in the hydrate layer, and collecting gas hydrate from the obtained excavation The gas hydrate collection method according to claim 1, wherein the gas hydrate is collected. A gas hydrate collection system for collecting the gas hydrate from a hydrate layer that exists in the seabed and includes gas hydrate,
A drilling device for drilling the hydrate layer to obtain a drilled article containing the gas hydrate and earth and sand;
A stirring device for mechanically stirring the excavated material;
A recovery device that recovers the gas hydrate separated from the excavated matter by being stirred by the stirring device;
A gas hydrate collection system comprising:   The gas hydrate collection system according to claim 7, wherein the excavator excavates the forward hydrate layer while moving forward.   The gas hydrate collection system according to claim 8, wherein the stirring device is provided integrally with the excavation device.   The gas hydrate collection system according to claim 7, wherein the excavator is a screw conveyor.   11. The gas hydrate according to claim 7, wherein the agitation device is installed behind the excavation device in a traveling direction, and the excavated material is conveyed from the excavation device to the agitation device by a conveyance device. Collection system.

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