JP6384919B2 - Hydrate drilling apparatus and hydrate drilling method - Google Patents

Description

  The present invention relates to a hydrate excavation apparatus and a hydrate excavation method having an excavating blade for excavating a water bottom such as a seabed or a lake bottom where methane hydrate exists.

  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 the guest molecule under the bottom of the ocean, lakes, etc. that meet the conditions for generating high-pressure and low-temperature gas hydrates. ing.

The methane hydrate on the bottom of the seabed, lake bottom, etc. is composed of a surface-type methane hydrate exposed on the surface of the bottom of the water at a depth of 400 m or more, and a sand layer-type methane hydrate that is mixed with sand in the basement of the bottom. There is a rate.
For the purpose of investigating the existence state of methane hydrate on the bottom of the water or collecting methane hydrate, the bottom of the sea or the bottom of the lake where the methane hydrate is present is excavated with a drilling device.

  In Patent Document 1, even if a hard ground exists, the purpose is to reliably excavate the ground and methane hydrate, and to efficiently produce methane gas from methane hydrate. A methane gas production apparatus is described in which water having a low methane concentration is supplied to an introduction chamber provided on the opposite side of the cutter head from the excavating blade, and water in the introduction chamber is pumped to recover methane gas. .

JP 2011-84896 A

Methane hydrate exists without being decomposed at deep water bottoms with a depth of 400 m or more because the pressure and temperature satisfy the conditions for producing methane hydrate. However, when excavating with the excavating blade of the excavator, methane hydrate is slightly decomposed due to heat generated by a large dynamic frictional resistance at the contact portion between the excavating blade and methane hydrate. The decomposition produces methane gas and water, but since the equilibrium condition at that location is on the production side, the production reaction proceeds immediately and methane hydrate is regenerated. At that time, part or most of the regenerated methane hydrate adheres to the surface of the drilling blade.
If the methane hydrate adheres gradually and the amount of adhesion increases, the rotation of the excavating blade may stop, causing a problem that the methane hydrate excavation cannot be continued. In Patent Document 1, such a problem is not considered at all.

  An object of the present invention is to reduce the possibility that excavation cannot be continued due to the stop of the rotation of the excavating blade when excavating a seabed such as a seabed or a lake bottom where methane hydrate exists.

  A first aspect of the present invention for solving the above problem is a hydrate drilling device having a drilling blade for drilling a bottom of water in which methane hydrate is present, wherein the fluid discharges fluid to the portion of the drilling blade. It has a discharge part, and the fluid discharge part discharges the fluid in which methane gas is not melted to a saturated state to the excavation blade part.

  Here, “fluid” is preferably seawater for the ocean and lake water for the lake. However, the term “fluid” is used in this specification to include fresh water, fresh water, brackish water, and the like other than the seawater and lake water. ing.

According to this aspect, the surface of the drilling blade is coated with the fluid discharged by the fluid discharge portion, and methane hydrate can be prevented from being generated and attached on the surface of the drilling blade by the coating. .
In addition, since the fluid discharged to the excavation blade portion is a fluid in which methane gas is not dissolved until saturation, even if methane hydrate is generated on the surface of the excavation blade, it is decomposed by the unsaturated fluid. can do. Thereby, it can suppress effectively that methane hydrate produces | generates and adheres on the surface of a digging blade.

  The hydrate excavation device according to a second aspect of the present invention is characterized in that, in the first aspect, the fluid discharge section discharges water near the bottom of the water as the fluid to the portion of the excavation blade. It is.

  According to this aspect, since the fluid discharge unit discharges water near the bottom of the water to the excavation blade portion, a low-powered power source for discharge such as a pump is used to supply water to the excavation blade portion. Can be released, and cost reduction can be achieved.

The hydrate excavation apparatus according to the third aspect of the present invention is the fluid according to the first aspect or the second aspect, wherein the fluid discharged to the excavation blade portion is a fluid having a temperature higher than the water temperature in the vicinity of the excavation blade. It is characterized by being.
Here, the “high temperature” in the “high temperature fluid” is preferably about 10 ° C., particularly about 20 ° C., from the practical viewpoint.

  According to this aspect, since the fluid having a temperature higher than the water temperature in the vicinity of the excavating blade is used as the fluid discharged to the excavating blade portion, even if methane hydrate is generated on the surface of the excavating blade, the high temperature is used. It can be decomposed more effectively by this fluid.

  According to a fourth aspect of the present invention, in the hydrate drilling device according to any one of the first to third aspects, the fluid discharge section is configured to continuously discharge the water. It is characterized by being.

  According to this aspect, since the fluid discharge part is configured to continuously discharge the water, it is easy to stably create a state where the surface of the drilling blade is coated with the fluid, and thus methane It can suppress more effectively that a hydrate produces | generates and adheres on the surface of a digging blade.

  According to a fifth aspect of the present invention, in the hydrate excavation device according to any one of the first to fourth aspects, the fluid discharge portion is disposed along the rotation axis of the excavation blade. The fluid is discharged to a portion of the excavation blade using a closed pipe as a flow path.

  According to this aspect, the fluid discharge portion discharges the fluid to the portion of the excavation blade by using a pipe disposed along the rotation axis of the excavation blade as a flow path. Can be easily realized.

  The hydrate excavation device according to a sixth aspect of the present invention is the digging device for a hydrate according to any one of the first to fourth aspects, wherein the fluid discharge portion uses the inside of the rotation shaft of the excavation blade as a flow path. A digging apparatus for hydrate, wherein the fluid is discharged to a portion of the excavating blade.

  According to this aspect, the fluid discharge portion discharges the fluid to the portion of the excavation blade by using the inside of the rotation shaft of the excavation blade as a flow path, so that the surface of the excavation blade is coated with the fluid. The structure to be made can be easily realized using the existing rotating shaft.

A hydrate excavation method according to a seventh aspect of the present invention is a hydrate excavation method for excavating a water bottom in which methane hydrate is present with an excavation blade, wherein a fluid in which methane gas is not melted to a saturated state is part of the excavation blade. It is characterized by excavating while being discharged.
According to this aspect, the same effect as in the first aspect can be obtained.

The schematic side view which shows the state of the excavation initial stage using the hydrate excavation apparatus which concerns on Embodiment 1 of this invention. The schematic side view which shows the state of the late excavation using the hydrate excavation apparatus which concerns on Embodiment 1 of this invention. The schematic side view which shows the state of the excavation initial stage using the hydrate excavation apparatus which concerns on Embodiment 2 of this invention.

[Embodiment 1]
Hereinafter, the hydrate excavation apparatus according to Embodiment 1 of the present invention will be described in detail with reference to FIGS. 1 and 2.
As shown in FIG. 1, the hydrate excavation apparatus 1 according to the first embodiment discharges a fluid L to the excavation blade 3 excavating the seabed 2 where the methane hydrate MH exists, and the excavation blade 3. A fluid discharge part 4 is provided. Although FIG. 1 shows a case where the object to be excavated is a surface layer type methane hydrate MH, a sand layer type methane hydrate may be used. In addition, since it becomes the description similar to the seabed 2 about the lake bottom, the description is abbreviate | omitted.

  The excavation blade 3 is attached to the lower end of the rotary shaft 5. The upper end of the rotary shaft 5 is rotatably held by the rotary power transmission unit 7 of the excavation ship 6. The rotary shaft 5 receives the rotational force from the rotational power transmission unit 7 and rotates around the shaft 8, and the lower excavation blade 3 rotates by this rotation to excavate the methane hydrate MH. Examples of the excavating blade include a drill structure and a structure having a cutter bit.

  In the present embodiment, the fluid discharge portion 4 is configured to discharge the fluid L to a portion of the excavation blade 3 using a tube 9 disposed along the rotation axis 5 of the excavation blade 3 as a flow path. Yes. The tube 9 is provided adjacent to the upper side of the excavating blade so as to integrally move in the excavation direction along with excavation of the excavating blade 3.

The fluid discharge unit 4 is configured to discharge the fluid L in which the methane gas is not dissolved to a saturated state to the excavation blade 3 part.
Here, it can be said that the lower the concentration of methane gas dissolved in the fluid L, the better. However, from a practical viewpoint, 50% or less, particularly 10% or less of the saturated state is preferable.
In addition, “release” in “release to the portion of the excavating blade 3” is preferably a state in which the fluid L is discharged from the discharge port 10 of the fluid discharge portion 4 so as not to be mixed with the surrounding seawater. . Furthermore, it is preferable that the fluid L flowing out from the discharge port 10 is discharged from the center of the tip of the excavation blade 3 toward the outer periphery of the excavation blade 3.
Further, when the fluid L penetrates the gap between the excavating blade 3 and the excavated methane hydrate and oozes out to the excavating blade 3 side, the surface of the excavating blade 3 is difficult to be coated with the fluid L. Therefore, it is preferable that the fluid L comes out of the discharge port 10 of the fluid discharge unit 4 and directly contacts the surface of the excavating blade 3. That is, the discharge port 10 is preferably arranged so that the fluid L flowing out from the discharge port 10 is in direct contact with the excavation blade 3.

In this embodiment, the fluid discharge unit 4 is configured to discharge the water near the bottom 2 as the fluid L to the excavation blade 3. That is, the seawater supply pump 11 placed on the seabed 2 is configured to supply seawater in the vicinity of the seabed 2 into the pipe 9 via the flow path line 12. In the figure, reference numeral 13 denotes a connection portion between the flow path line 12 and the pipe 9. Reference numeral 16 denotes a connection line for electrically connecting the excavation ship 6 and the seawater supply pump 11.
Since seawater (water) in the vicinity of the seabed 2 is used in this way, water can be discharged to the portion of the drilling blade 3 using a low-powered power source for discharge such as the seawater supply pump 11. Cost reduction.

The seawater immediately above the surface layer 15 of methane hydrate MH often has methane gas dissolved in a saturated state. Therefore, in the present embodiment, the seawater supply pump 11 is placed not on the surface layer 15 of the methane hydrate MH but on the ground 14. By installing the seawater supply pump 11 on the ground 14 where seawater whose methane concentration is not saturated is present, the seawater having a low methane concentration can be easily supplied to the excavation blade 3 by the low power seawater supply pump 11. Can be released.
Further, since the installation position of the seawater supply pump 11 can be placed at a position far away from the excavation position of the methane hydrate MH (the position where the excavation blade 3 is located), Even when the hydrate MH layer collapses, the possibility that the seawater supply pump 11 is caught in the collapse can be reduced.
Alternatively, with the seawater supply pump 11 installed near the excavation position (position where the excavation blade 3 is located), only the intake line (for collecting seawater with a low methane concentration) is extended to intake water into the seawater region with a low methane concentration. Mouth can also be installed.

  In addition, it does not matter that the power of the seawater supply pump 11 becomes large, and when priority is given to discharging seawater having a low methane concentration to the excavation blade 3 part, seawater near the seabed 2 (near the ground 14) Alternatively, seawater near the sea surface 18 or near the sea surface 18 may be used. Moreover, you may utilize fresh water other than seawater, fresh water, brackish water, etc., if it has a low methane concentration.

The “near the bottom” in the “water near the bottom 2” means a region that does not greatly differ from the water pressure at the depth where the excavation blade 3 is located. Therefore, not only the sea bottom (water bottom) 2 as shown in the figure, but sea water (water) at a location above the sea bottom 2 and shallow, for example, about 50 m may be used. In this case, the seawater supply pump 11 is floated in the sea by a float or a hanger.
In this case, since it is separated from the seabed 2 to some extent, the methane concentration in the seawater tends to decrease by the distance. Therefore, the position above the methane hydrate MH layer may be used as the position for floating the seawater supply pump 11.

Furthermore, in this embodiment, the fluid discharge unit 4 is configured to continuously discharge the seawater (water) to the cutting blade 3. This continuous discharge structure makes it easy to stably create a state in which the surface of the excavation blade 3 is coated with the seawater (water). Thereby, it can suppress more effectively that methane hydrate produces | generates on the surface of the digging blade 3, and adheres.
In addition, it is preferable that the continuous discharge can be selected both when the flow velocity and the flow rate, which are the outflow states of the fluid L, are constant and when they are appropriately changed.
Further, it may be possible to repeat the release and stop instead of the continuous release.

Next, the operation of the hydrate excavation method by the hydrate excavation apparatus 1 will be described with reference to FIGS. 1 and 2.
The seawater supply pump 11 is installed on the ground 14 of the seabed 2. Then, the seawater supply pump 11 starts the excavation of methane hydrate MH by rotating the excavation blade 3 while discharging the fluid L, which is seawater in the vicinity of the seabed and having a low methane concentration, to the excavation blade 3 portion. To do. FIG. 1 shows a state at the initial stage of excavation, and FIG. 2 shows a state at the later stage of excavation, in which an excavation hole 17 is formed in the excavation direction of the excavation blade 3. The excavation depth is, for example, 100 meters, and the excavation diameter is several tens of centimeters.

According to this embodiment, the surface of the drilling blade 3 is coated with the fluid L, which is seawater discharged from the discharge port 10 of the fluid discharge unit 4, and methane hydrate is generated on the surface of the drilling blade 3. Adhesion can be suppressed by the coating.
Moreover, since the fluid L which is seawater discharged to the portion of the excavating blade 3 is a fluid L in which methane gas is not dissolved until saturation, even if methane hydrate is generated on the surface of the excavating blade 3, It can be decomposed by the unsaturated fluid L. Thereby, it can suppress effectively that methane hydrate produces | generates on the surface of the digging blade 3, and adheres.

[Embodiment 2]
Next, the hydrate excavation apparatus 1 according to the second embodiment will be described with reference to FIG. In the second embodiment, since many of the constituent elements are common to the first embodiment, the parts of the different constituent elements will be described, the same reference numerals are given to the common parts, and the description thereof will be omitted.
In the second embodiment, the fluid discharged to the portion of the excavation blade 3 is a fluid having a temperature higher than the water temperature in the vicinity of the excavation blade 3. A heating unit 19 is provided in the flow path line 12, and the high-temperature fluid is created by the heating unit 19. Here, the “high temperature” in the “high temperature fluid” is preferably about 10 ° C., particularly about 20 ° C., from the practical viewpoint.

  According to the second embodiment, since the fluid L having a temperature higher than the water temperature in the vicinity of the excavating blade 3 is used as the fluid L released to the excavating blade 3 portion, methane hydrate is generated on the surface of the excavating blade 3. Even so, it can be more effectively decomposed by the hot fluid L.

[Embodiment 3]
The hydrate excavation apparatus 1 according to the third embodiment is configured such that the fluid discharge unit 4 discharges the fluid L to a portion of the excavation blade 3 using the inside of the rotary shaft 5 of the excavation blade 3 as a flow path. (Not shown). Also in this embodiment, the outlet is preferably configured so that the fluid L flowing out from the discharge port directly contacts the excavating blade 3 as in the first embodiment.

  According to the third embodiment, the fluid discharge unit 4 discharges the fluid L to the portion of the excavating blade 3 using the inside of the rotary shaft 5 of the excavating blade 3 as a flow path. The structure which makes the surface of 3 coated can be easily realized using the existing rotating shaft.

[Other Embodiments]
Although the said embodiment demonstrated the case where the surface layer type methane hydrate of a seabed was excavated, it is applicable similarly to a sand layer type methane hydrate. Sand layer type methane hydrate often exists on the seabed at a depth of several hundred meters below the ground. Therefore, unlike the surface layer type methane hydrate excavation, in the sand layer type methane hydrate, the seawater near the excavation position has a low methane concentration. Can be installed on top.

  The present invention is not limited to the above-described embodiment, 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. .

1 hydrate drilling equipment, 2 water bottom (sea bottom, lake bottom), 3 drilling blades,
4 Fluid discharge part, 5 Rotating shaft, 6 Drilling ship, 7 Rotating power transmission part,
8 axis, 9 pipes, 10 discharge port, 11 seawater supply pump,
12 channel line, 13 connection part, 14 ground, 15 surface layer, 16 connection line,
17 drilling holes, 18 sea level, 19 heating section

Claims (7)

A hydrate drilling device having a drilling blade for drilling a water bottom where methane hydrate is present,
A fluid discharge part that discharges fluid to a portion of the excavation blade;
The hydrating excavator is characterized in that the fluid discharge unit discharges a fluid in which methane gas is not dissolved to a saturated state to a portion of the excavating blade so that the fluid is in direct contact with the excavating blade. The hydrate drilling device according to claim 1,
The hydrating excavator is characterized in that the fluid discharge section discharges the fluid from the center of the tip of the excavating blade toward the outer periphery of the excavating blade . The hydrate drilling device according to claim 1 or 2,
The hydrate drilling device according to claim 1, wherein the fluid discharged to the portion of the drilling blade is a fluid having a temperature higher than a water temperature in the vicinity of the drilling blade. The hydrate drilling device according to claim 3 ,
The fluid discharge section includes a heating section that heats the fluid to be discharged,
The digging apparatus for hydrate , wherein the heating unit heats the fluid to a temperature higher than a water temperature in the vicinity of the excavating blade and releases the fluid to the excavating blade portion . The hydrate drilling device according to any one of claims 1 to 4,
The hydrating excavator is characterized in that the fluid discharge unit discharges the fluid to a portion of the excavation blade by using a pipe disposed along the rotation axis of the excavation blade as a flow path. The hydrate drilling device according to any one of claims 1 to 4,
The hydrating excavator is characterized in that the fluid discharge section discharges the fluid to a portion of the excavating blade by using the inside of the rotary shaft of the excavating blade as a flow path. A hydrate excavation method for excavating a water bottom in which methane hydrate exists with a drilling blade,
A hydrate excavation method characterized in that excavation is performed while discharging a fluid in which methane gas is not dissolved to a saturated state to a portion of the excavation blade so that the fluid is in direct contact with the excavation blade.

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