JP2016176314A - Water bottom excavation system and water bottom excavation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water bottom excavation system capable of inhibiting clogging of a riser pipe when matter-to-be-excavated separated from a water bottom is hoisted by the riser pipe, and a water bottom excavation method.SOLUTION: An excavation mechanism 5 comprises a drill pipe 6 and excavation teeth 7 that are installed at an end thereof. Matter-to-be-excavated m is crushed by a crushing blade 9 protruding toward a riser pipe 4 from an outer peripheral surface of the drill pipe 6 and rotating around an axis line c of the drill pipe 6, while the matter-to-be-excavated m, which is separated from a water bottom 2 by the excavation teeth 7, is hoisted toward a collection ship 3 through a space between the riser pipe 4 and the drill pipe 6.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a submarine excavation system and a submarine excavation method including a riser pipe disposed from a ship toward the bottom of the water and a excavation mechanism that excavates the water bottom at the bottom end of the riser pipe. The present invention relates to a water bottom excavation system and a water bottom excavation method that can suppress blockage of a riser pipe when a work to be excavated separated from the water bottom is taken up by the riser pipe.

  Various water bottom excavation systems for excavating methane gas hydrate present on the sea floor have been proposed (see, for example, Patent Document 1).

  Patent Document 1 proposes a water bottom excavation system including a riser pipe disposed from a ship toward the bottom of the water and an auger installed at a lower end portion of the riser pipe for excavating the water bottom. The auger is composed of screw-shaped excavating teeth having a rotation axis in the horizontal direction, and the water bottom is excavated by the rotation of the excavating teeth to separate the gas hydrate from the water bottom. The massive gas hydrate separated from the bottom of the water is taken up by the ship through the riser pipe.

  When the massive gas hydrate, which is the excavated material separated from the bottom of the water, is relatively large, the riser tube is clogged in the middle of the riser tube, causing a problem that the riser tube is blocked. When the riser tube is blocked, the gas hydrate floating in the riser tube is brought into contact with the blocked portion one after another and is fixed to each other, so that there is a high possibility that the closed section is enlarged.

  In the restoration work when the riser pipe is blocked, for example, a method of supplying seawater having a relatively high temperature from the ship side into the riser pipe to melt the gas hydrate in the closed section can be considered. However, when the riser pipe is completely blocked, the seawater supplied from the upper side of the water does not escape from the bottom of the riser pipe, so it is difficult to send the relatively high temperature seawater to the closed section itself. .

  Further, as a restoration work, for example, a method of raising the riser pipe onto the ship and heating and melting the gas hydrate in the closed section on the ship can be considered. However, the water bottom where the gas hydrate is present has a depth of, for example, 400 to 2000 m, and the riser pipe has the same length.

  When the riser tube is blocked, it is extremely difficult to recover, and the amount of gas hydrate that can be recovered from the bottom of the water is significantly reduced.

Japanese Patent No. 3395008

  The present invention has been made in view of the above-described problems, and a purpose of the present invention is to provide a water bottom excavation system and a water bottom excavation capable of suppressing the clogging of the riser pipe when the work to be excavated separated from the water bottom by excavation is lifted by the riser pipe. It is to provide a method.

  A bottom drilling system according to a first aspect of the present invention that achieves the above object includes a riser pipe extending from a collection ship arranged on the water toward the bottom of the water, and a drilling mechanism that drills the bottom of the water at the bottom of the riser pipe. The drilling mechanism includes a drill pipe disposed in the riser pipe, drilling teeth installed at the bottom end of the drill pipe, and the riser pipe from an outer peripheral surface of the drill pipe. The crushing blade is provided so as to be rotatable around the axis of the drill pipe.

  The water bottom excavation method of the first aspect of the present invention is the water bottom excavation method, wherein a riser pipe is arranged from a collection ship arranged on the water toward the water bottom, and the water bottom is excavated on the water bottom side of the riser pipe by a drilling mechanism. The mechanism is composed of a drill pipe and drilling teeth installed at the end thereof, and the work to be drilled separated from the bottom of the water by the drilling teeth is taken up between the riser pipe and the drill pipe toward the collection ship. The drilled object is crushed by a crushing blade that protrudes from the outer peripheral surface of the drill pipe toward the riser pipe and rotates around the axis of the drill pipe.

  A bottom drilling system according to a second aspect of the present invention includes a riser pipe extending from a collection ship arranged on the water toward the bottom of the water, and a drilling mechanism for drilling the bottom of the water at the bottom of the riser pipe. The drilling mechanism protrudes from the inner peripheral surface of the riser pipe toward the drill pipe, the drill pipe disposed in the riser pipe, the drill teeth installed at the bottom end of the drill pipe A fixed crushing blade is provided.

  The water bottom excavation method of the second aspect of the present invention is the water bottom excavation method in which the riser pipe is arranged from the collection ship arranged on the water toward the water bottom, and the water bottom is excavated on the water bottom side of the riser pipe by a drilling mechanism. The mechanism is composed of a drill pipe and a drilling tooth installed at the end thereof, and a fixed crushing blade protruding from the inner peripheral surface of the riser pipe toward the drill pipe is installed and separated from the bottom of the water by the drilling tooth. The excavated object is crushed by the fixed crushing blade while the excavated object is collected toward the collection ship through the riser pipe and the drill pipe.

  In the water bottom excavation system and the water bottom excavation method according to the first aspect of the present invention, the work to be excavated in the riser pipe collides with the crushing blade rotating around the axis of the drill pipe and is crushed and becomes smaller. It is advantageous to prevent an object from being caught between the riser pipe and the drill pipe and closing the riser pipe.

  The crushing blade can be configured to include a paddle surface that turns the water in the riser pipe around the axis of the drill pipe. According to this configuration, since the crushing blade having the paddle surface generates a swirling flow in the riser pipe, it is advantageous for suppressing the excavated material from adhering to the inner peripheral surface of the riser pipe and closing the riser pipe. is there.

  In the water bottom excavation system and the water bottom excavation method according to the second aspect of the present invention, the work to be excavated inside the riser pipe collides with the fixed crushing blade protruding from the inner peripheral surface of the riser pipe toward the drill pipe and crushes. Therefore, it is advantageous to suppress the object to be excavated from being sandwiched between the riser pipe and the drill pipe and blocking the riser pipe.

  The crushing blade and / or the fixed crushing blade can be configured to be installed at a plurality of locations at intervals in the axial direction of the drill pipe. It is possible to sequentially crush the work to be excavated in the riser pipe at a plurality of locations.

It is explanatory drawing which illustrates the water bottom excavation system of this invention. It is explanatory drawing which expands and illustrates the bottom end part of the riser pipe | tube of the bottom drilling system of 1st this invention. It is explanatory drawing which illustrates the riser pipe | tube of FIG. 2 by AA arrow. It is explanatory drawing which expands and illustrates the bottom end part of the riser pipe | tube of the bottom drilling system of 2nd this invention. It is explanatory drawing which illustrates the riser pipe | tube of FIG. 4 by BB arrow. It is explanatory drawing which expands and illustrates the water-bottom side edge part of the riser pipe | tube of another embodiment. It is explanatory drawing which illustrates the riser pipe | tube of FIG. 6 by CC arrow.

  Hereinafter, a water bottom excavation system and a water bottom excavation method of the present invention will be described based on the embodiments shown in the drawings. In the drawing, the axial direction of the riser pipe and the drill pipe is indicated by an arrow z, the direction orthogonal to the axial direction is indicated by an arrow x, and the direction orthogonal to the arrows x and z is indicated by an arrow y.

  As illustrated in FIG. 1, the underwater excavation system 1 of the present invention can be used when excavating and recovering a surface layer methane hydrate existing in the bottom 2 of the sea or lake. On the bottom 2 having a depth of several hundreds to thousands of meters, the so-called surface methane hydrate in which the gas hydrate m is dense and a part of the gas hydrate m is exposed from the bottom 2 or the gas hydrate m is a sand grain of the bottom 2 There is a so-called sand layer methane hydrate dispersed between the two.

  The water bottom excavation system 1 includes a collection ship 3 disposed on the water, a riser pipe 4 extending from the collection ship 3 toward the water bottom 2, and a drilling mechanism 5 that excavates the water bottom 2. The excavation mechanism 5 includes a drill pipe 6 disposed in the riser pipe 4 so as to be able to advance and retreat in the axial direction (extension direction) z, and excavation teeth 7 installed at the bottom end of the drill pipe 6. Yes.

  When the gas hydrate in the bottom 2 is excavated and recovered by the bottom excavation system 1, the riser pipe 4 is first arranged from the collection vessel 3 toward the bottom 2. The riser pipe 4 is disposed in a state where the bottom end of the water bottom has a gap with the water bottom 2. That is, the bottom end of the riser pipe 4 and the bottom 2 are not in contact with each other.

  The drill pipe 6 provided with the excavating teeth 7 is lowered from the water-side end of the riser pipe 4. The drill pipe 6 and the riser pipe 4 are mounted on the collection ship 3 in a state of being divided into a plurality of parts in the axial direction, and extend toward the water bottom 2 while being connected on the collection ship 3.

  After the excavation teeth 7 are landed on the bottom 2, the excavation teeth 7 are rotated by rotating the drill pipe 6 around its axis to excavate the bottom 2. The method of rotating the excavation teeth 7 is not limited to the above, for example, the excavation teeth 7 provided with a turbine motor are installed at the bottom end of the drill pipe 6, and the fluid is supplied to the bottom via the drill pipe 6. You may make it the structure which rotates the excavation tooth | gear 7 by rotating a turbine motor with the pressure of this fluid.

  In the gas hydrate m, molecules such as methane gas enter into the gaps of the three-dimensional network structure of water molecules to form ice crystals. In this specification, seawater, lake water, and the like constituting a network structure are referred to as raw water, and natural gas composed of methane gas and a plurality of types of gas including methane gas is sometimes referred to as raw material gas.

  The massive gas hydrate that is the work to be excavated separated from the water bottom 2 by the excavating teeth 7 has a specific gravity of about 0.9, and therefore floats between the drill pipe 6 and the riser pipe 4 by buoyancy.

Since the pressure (water pressure) in the riser pipe 4 becomes lower as the water depth becomes shallower, a part of the massive gas hydrate m melts as it goes above the riser pipe 4 and bubbles of the raw material gas are generated. is there. Further, since the amount of the source gas that can be dissolved in water decreases (the solubility decreases) as the water depth becomes shallower, the source gas that can no longer be dissolved may be in the form of bubbles. The closer to the water-side end of the riser tube 4, the more easily bubbles are generated, and the amount thereof increases, so the density of the fluid flowing in the riser tube 4 becomes lower as it is closer to the water-side end.

  Since the density of the fluid in the riser pipe 4 is smaller than that of the surrounding water, the surrounding water flows in from the bottom end of the riser pipe 4, and an upward flow is generated in the riser pipe 4. The gas hydrate m is conveyed toward the water also by this upward flow. The same effect as the so-called gas lift system can be obtained. Since the buoyancy generated in the gas hydrate m and the density difference between the riser pipe 4 and the surrounding water are used, the gas hydrate m can be transported from the bottom 2 to the water without requiring enormous energy. . This merit becomes remarkable when the bottom 2 is in a deep position.

  An air lift pump that forcibly sends gas into the riser pipe 4 can be installed to further increase the density difference from the riser pipe 4. When the density difference increases, the flow rate of the upward flow generated in the riser pipe 4 increases, so that the moving speed of the gas hydrate m can be increased to improve the conveyance efficiency. A fluid pump may be installed in the collection ship 3 and the fluid in the riser pipe 4 may be sucked up by this fluid pump.

  The massive gas hydrate m conveyed to the water upper end of the riser pipe 4 is collected and stored by the collection ship 3. The gas hydrate m may be melted in the riser pipe 4 and recovered in a raw material gas state.

  A cylindrical collection cover 8 that expands toward the water bottom 2 may be installed at the bottom end of the riser pipe 4. The configuration in which the collection cover 8 is installed makes it easier to guide the gas hydrate m, which is the work to be excavated separately from the bottom 2, into the riser pipe 4, and eliminates the recovery leakage of the gas hydrate m to reduce the recovery amount. It is advantageous to increase.

  As illustrated in FIGS. 2 and 3, the bottom drilling system 1 of the first aspect of the present invention has a plurality of crushing blades 9 protruding from the outer peripheral surface of the drill pipe 6 in the vicinity of the bottom end of the drill pipe 6. is set up. The crushing blade 9 protruding from the outer peripheral surface of the drill pipe 6 is in a state of being rotatable around the axis c of the drill pipe 6. In this embodiment, the bottom end of the riser pipe 4 is arranged in a state where it does not contact the bottom 2.

  The crushing blade 9 is formed in a substantially flat plate shape, and is installed in the drill pipe 6 with the top surface facing the water side and the bottom surface facing the water bottom side. As illustrated in FIG. 3, the fixed end side of the flat crushing blade 9 is installed in contact with the outer peripheral surface of the drill pipe 6, and the free end side extends toward the inner peripheral surface of the riser pipe 4. The free end of the crushing blade 9 is a position that does not contact the inner peripheral surface of the riser tube 4, and the length from the fixed end to the free end is a straight line connecting the outer peripheral surface of the drill pipe 6 and the inner peripheral surface of the riser tube 4. The length is about 40 to 70% of the shortest distance.

  When the crushing blade 9 rotates around the axis c of the drill pipe 6, the crushing blade 9 includes a paddle surface 10 that pushes the fluid in the riser pipe 4 to generate a swirling flow around the axis c. That is, the top surface or the bottom surface of the crushing blade 9 becomes the paddle surface 10 according to the rotation direction of the drill pipe 6.

In this embodiment, the four crushing blades 9 are installed by shifting by 90 ° in the circumferential direction along the outer peripheral surface of the drill pipe 6, but the present invention is not limited to this configuration. It is sufficient that at least one crushing blade 9 is installed, and five or more crushing blades 9 may be installed. Further, the crushing blade 9 can be installed at any position in the axial direction z of the drill pipe 6. At this time, if the crushing blade 9 is installed in the vicinity of the bottom end of the drill pipe 6, the massive gas hydrate m collected in the riser pipe 4 can be crushed at an early stage, and the riser pipe 4 is blocked. It is advantageous to suppress.

  After bringing the excavating teeth 7 into contact with the bottom 2, the drill pipe 6 is rotated counterclockwise around its axis c. For example, when the drill pipe 6 is rotated at 10 to 300 rpm, the excavating teeth 7 are rotated in accordance with this and the bottom 2 is excavated. At this time, a fluid such as seawater can be supplied from the collection ship 3 into the drill pipe 6 and discharged from the vicinity of the excavating teeth 7. With this fluid, the work to be excavated from the bottom 2 can be easily separated from the bottom 2.

  The massive gas hydrate m (the drilled object) separated from the water bottom 2 is taken up to the collection ship 3 through the drill pipe 6 and the riser pipe 4. Due to the upward flow generated in the riser pipe 4, surrounding seawater and the like flow into the riser pipe 4 from between the bottom end of the riser pipe 4 and the bottom 2. The crushing blade 9 rotating around the axis c together with the drill pipe 6 collides with the massive gas hydrate m rising between the drill pipe 6 and the riser pipe 4 and crushes. Since the massive gas hydrate m is crushed small by the crushing blade 9, it is advantageous for suppressing the gas hydrate m from being sandwiched between the drill pipe 6 and the riser pipe 4 to block the riser pipe 4. .

  In this embodiment, since the crushing blade 9 has the paddle surface 10, a swirling flow is generated in the riser pipe 4. By this swirling flow, the massive gas hydrate m having a relatively small specific gravity collects in the central portion of the riser pipe 4, and the gas hydrate m can be prevented from adhering to the inner peripheral surface of the riser pipe 4. It is advantageous for suppressing the blockage. An angle θ of the surface direction of the paddle surface 10 with respect to the axial direction z can be determined as appropriate.

  The crushing blade 9 may be configured to be installed on the outer peripheral surface of the drill pipe 6 via the support shaft 11. The support shaft 11 extends in a direction perpendicular to the axial direction z of the drill pipe 6, and the crushing blade 9 is installed in a state in which the crushing blade 9 can tilt by the support shaft 11. At this time, the crushing blade 9 formed with a bearing may rotate with respect to the support shaft 11 fixed to the drill pipe 6, and the support shaft 11 is fixed to the bearing formed with the drill pipe 6. You may make it the structure which the crushing blade 9 rotates.

  Since the angle θ of the surface direction of the paddle surface 10 with respect to the axial direction z can be made variable, the strength of the swirling flow can be controlled. This angle θ is inclined in a direction from the state in which the surface direction of the paddle surface 10 is parallel to the axis c to the water side when the crushing blade 9 passes through the fixed end side from the free end side and the axis c is viewed. The angle between the axis c and the plane of the paddle surface 10. For example, when the angle θ is 0 °, the surface direction of the paddle surface 10 and the axis c are parallel to each other, and the range of the paddle surface 10 that pushes the water in the riser pipe 4 is maximized. When the angle θ is 45 °, for example, the paddle surface 10 is inclined to the water side, so that it is possible to generate a swirling flow that swirls around the axis c and rises. When the angle θ is 90 °, for example, the paddle surface 10 is completely directed upward, so that a swirl flow is hardly generated. That is, the function as the paddle surface 10 is not performed. This is advantageous when it is desired to only crush the gas hydrate m without generating a swirl flow. Moreover, since the rotational resistance of the drill pipe 6 can be reduced, the drill pipe 6 can be rotated with a comparatively small force. In the case where the paddle surface 10 is not a flat surface but has a curved or undulating shape, the angle θ is defined by the angle formed between the average surface and the axis c where the undulation of the paddle surface 10 is approximately a flat surface.

  When the angle is larger than 90 °, for example, the bottom surface, which is the surface opposite to the above, becomes the paddle surface 10, which generates a swirling flow and a descending flow. That is, the angle θ of the paddle surface 10 with respect to the axial direction z can be varied in the range of 0 ° or more and less than 180 °.

  Similarly, when the rotation direction of the drill pipe 6 is reversed, the swirling flow and the upward flow are generated according to the angle at which the paddle surface 10 is inclined upward, and the downward flow is generated when the paddle surface 10 is inclined downward. Will occur.

  Since the gas hydrate m can be withdrawn while adjusting the inclination of the paddle surface 10 as appropriate, the strength of the swirling flow can be adjusted while adjusting the amount of energy required to rotate the drill pipe 6.

  The gas hydrate m can be recovered by the collection ship 3 as a relatively small block crushed by the crushing blade 9. Further, the crushed lump may be collected while being melted with seawater or the like, separated on the collection ship 3, and recovered in a gaseous state. In this case, since it is crushed relatively small with the crushing blade 9 and then melted into seawater or the like, it can be melted more efficiently than when melted into seawater or the like as a relatively large lump.

  A plurality of crushing blades 9 may be installed along the axial direction z of the drill pipe 6. Since the lump gas hydrate m to be collected in the riser tube 4 can be crushed by the crushing blades 9 at a plurality of locations, it is advantageous to efficiently crush the lump gas hydrate m without leaking.

  At this time, it is desirable to install at least one crushing blade 9 in the vicinity of the bottom end of the drill pipe 6. Crushing the relatively large lump gas hydrate m collected in the riser pipe 4 at an early stage is advantageous for suppressing the riser pipe 4 from being blocked.

  A driving mechanism such as a turbine pump can be incorporated in the middle of the drill pipe 6 and the crushing blade 9 can be rotated by this driving mechanism. Even if the excavating teeth 7 are rotated by a turbine pump or the like and the drill pipe 6 is not rotated, the crushing blade 9 can be rotated by incorporating a drive mechanism.

  Further, the crushing blade 9 may be rotated at a speed different from the rotation of the drill pipe 6 by a configuration incorporating a drive mechanism. For example, in the initial stage when excavating the bottom 2, the rotational speed of the crushing blade 9 is being excavated while checking the state of the bottom 2 with the rotational speed of the excavating teeth 7 rotating together with the drill pipe 6 being about 10 to 30 rpm. Ascending flow can be generated in the riser pipe 4 at about 300 to 800 rpm.

  As illustrated in FIGS. 4 and 5, the bottom excavation system 1 according to the second aspect of the present invention includes a plurality of fixed crushing blades in a state of protruding from the inner peripheral surface of the riser pipe 4 in the vicinity of the bottom end of the riser pipe 4. 12 is installed. In this embodiment, the bottom end of the riser pipe 4 is disposed in contact with the bottom 2. Further, the fluid is supplied from the water side of the drill pipe 6 and the fluid discharged from the vicinity of the drilling teeth 7 is circulated in the riser pipe 4.

  In this embodiment, the fixed crushing blade 12 is formed in a substantially flat plate shape, and this top surface is orthogonal to the axial direction z (90 °) with the top surface facing the water upper side and the bottom surface facing the water bottom side. ) In the riser tube 4 in the state. Three fixed crushing blades 12 are stacked in the axial direction z of the riser tube 4 to form a set. As illustrated in FIG. 5, the fixed end side of the set of fixed crushing blades 12 is installed in contact with the inner peripheral surface of the riser pipe 4, and the free end side extends toward the drill pipe 6. The free end of the fixed crushing blade 12 is a position not in contact with the outer peripheral surface of the drill pipe 6, and the length from the fixed end to the free end is a straight line connecting the inner peripheral surface of the riser pipe 4 and the outer peripheral surface of the drill pipe 6. The length is about 40 to 70% with respect to the shortest distance.

  As illustrated in FIG. 4, in the vicinity of the free end of the fixed crushing blade 12, the three fixed crushing blades 12 stacked are spaced apart from each other and are not in contact with each other. That is, the three fixed crushing blades 12 are formed so that the thickness thereof decreases toward the free end.

  In this embodiment, four sets of fixed crushing blades 12 are installed by shifting by 90 ° in the circumferential direction along the inner peripheral surface of the riser tube 4, but the present invention is not limited to this configuration. It is sufficient that at least one set of fixed crushing blades 12 is installed, and five or more fixed crushing blades 12 may be installed. Three or more fixed crushing blades 12 may be stacked to form a set, or may be used alone without being stacked.

  Further, the fixed crushing blade 12 can be installed at any position in the axial direction z of the riser tube 4. At this time, if the fixed crushing blade 12 is installed in the vicinity of the bottom end of the riser pipe 4, the massive gas hydrate m collected in the riser pipe 4 can be crushed at an early stage, and the riser pipe 4 is blocked. It is advantageous to suppress this.

  The angle of the top surface of the fixed crushing blade 12 with respect to the axial direction z is not limited to 90 ° illustrated in FIG. 4 and can be appropriately determined within a range of 0 ° to less than 180 °.

  The massive gas hydrate m separated from the bottom 2 by the excavating teeth 7 rises between the drill pipe 6 and the riser pipe 4. At this time, the flow rate of the upward flow generated between the drill pipe 6 and the riser pipe 4 can be increased by increasing the flow rate of the fluid discharged from the bottom end of the drill pipe 6. The massive gas hydrate m that rises in the riser pipe 4 due to the upward flow collides with the fixed crushing blade 12 and is crushed by the impact to become smaller.

  The massive gas hydrate m is crushed by being sandwiched between the free end of the fixed crushing blade 12 and the rotating drill pipe 6.

  Since the block-shaped gas hydrate m can be crushed by the fixed crushing blade 12, it is advantageous for suppressing the gas hydrate m from being sandwiched between the drill pipe 6 and the riser pipe 4 to block the riser pipe 4.

  In this embodiment, the drill pipe 6 may be configured to have a crushing blade 9 having a paddle surface 10. That is, the water bottom excavation system 1 including the crushing blade 9 and the fixed crushing blade 12 can be provided. According to this configuration, a swirling flow is generated in the riser pipe 4, and the swirling flow raises the massive gas hydrate m and collides with the fixed crushing blade 12 while swirling around the axis c of the riser pipe 4. Since the force with which the massive gas hydrate m collides with the fixed crushing blade 12 can be increased, it is advantageous for efficiently crushing the gas hydrate m.

  As illustrated in FIGS. 6 and 7, in addition to the crushing blade 9 installed in the vicinity of the bottom end of the drill pipe 6, the second crushing blade 13 can be installed on the water side. The second crushing blade 13 is formed in a flat plate shape and is directly fixed to the drill pipe 6 without the support shaft 11 unlike the crushing blade 9. Further, the second crushing blade 13 is installed in a state in which the angle θ of the top surface is 90 ° with respect to the axial direction z of the drill pipe 6 and the top surface completely faces the water side. Since the top and bottom surfaces of the second crushing blade 13 do not push the water in the riser tube 4, it can be said that the paddle surface 10 is not provided.

  As illustrated in FIG. 7, four second crushing blades 13 are installed while being shifted by 90 ° in the circumferential direction along the outer peripheral surface of the drill pipe 6. The fixed crushing blades 12 project from the inner peripheral surface of the riser pipe 4 toward the drill pipe 6 and are arranged in four pieces shifted by 90 ° in the circumferential direction along the inner peripheral surface of the riser pipe 4.

As illustrated in FIG. 6, the fixed crushing blades 12 are arranged at a plurality of positions at intervals in the axial direction z of the riser pipe 4. With this configuration, even when the drill pipe 6 moves in the axial direction z of the drill pipe 6 due to the progress of excavation or the like, the second crushing blade 13 maintains a state of facing any one of the fixed crushing blades 12, The gas hydrate m passing between the second crushing blade 13 and the fixed crushing blade 12 can be efficiently crushed.

The fixed crushing blade 12 and the second crushing blade 13 are formed in such a size that their free ends do not contact each other when moved in the axial direction z of the drill pipe 6. That is, the fixed crushing blade 12 and the second crushing blade 13 are not overlapped with each other in the axial direction z of the riser tube 4.

  The massive gas hydrate m separated from the bottom 2 and rising in the riser pipe 4 is first crushed by the crushing blade 9. The crushed gas hydrate m rises while swirling by a swirling flow generated by the paddle surface 10 of the crushing blade 9. The crushed gas hydrate m collides with a pair of fixed crushing blades 12 and a second crushing blade 13 that rotates between them and is further crushed and then rises in the riser pipe 4. It is collected and collected by the collection ship 3.

  According to this configuration, the massive gas hydrate m cannot pass through the fixed crushing blade 12 and the second crushing blade 13 unless crushing to a certain size or less. That is, the relatively large lump gas hydrate m can be reliably crushed and reduced. Since it becomes difficult for the massive gas hydrate m that moves in the riser tube 4 to remain relatively large without colliding with the crushing blade 9 or the like, it is further advantageous to prevent the riser tube 4 from being blocked.

  It is desirable to install the fixed crushing blade 12 and the second crushing blade 13 at a position away from the water bottom side end of the riser pipe 4 to some extent. Stones and the like separated from the bottom 2 may rise in the riser pipe 4 due to the upward flow. However, since stones and the like have a large specific gravity, they become harder to rise as they become larger lumps. By installing the fixed crushing blade 12 or the like at a position where a large block of stone or the like cannot rise, it is advantageous to prevent the fixed crushing blade 12 and the like from being damaged by biting the stone or the like.

  When the fluid is supplied to the vicinity of the drilling teeth 7 via the drill pipe 6, an opening is formed in the vicinity of the second crushing blade 13 on the outer peripheral surface of the drill pipe 6, and this fluid is the second You may make it the structure supplied to the vicinity of the crushing blade 13. FIG. Since water with a low raw material gas concentration is supplied in the vicinity of the second crushing blade 13, a gas hydrate is generated by the reaction between the raw water, such as seawater, and the raw material gas dissolved in the seawater, and this gas hydrate m It is advantageous to prevent the second crushing blade 13 and the fixed crushing blade 12 from adhering to hindering the rotation of the second crushing blade 13.

  The crushing blade 9, the fixed crushing blade 12, and the second crushing blade 13 are not limited to the above, and can be installed in appropriate combinations. In addition, the riser tube 4 can be installed in appropriate combination at a plurality of locations with an interval in the axial direction z. The bottom end of the riser pipe 4 may or may not contact the bottom 2.

DESCRIPTION OF SYMBOLS 1 Water bottom drilling system 2 Water bottom 3 Collection ship 4 Riser pipe 5 Drilling mechanism 6 Drill pipe 7 Drilling tooth 8 Collecting cover 9 Crushing blade 10 Paddle surface 11 Support shaft 12 Fixed crushing blade 13 Second crushing blade c (Riser pipe or drill pipe A) axis m gas hydrate

Claims (9)

In a bottom drilling system comprising a riser pipe extending from a collection ship arranged on the water toward the bottom of the water, and a drilling mechanism for drilling the bottom of the water at the bottom of the riser pipe,
The drilling mechanism includes a drill pipe disposed in the riser pipe, drilling teeth installed at the bottom end of the drill pipe, and a crushing blade protruding from the outer peripheral surface of the drill pipe toward the riser pipe. With
The water bottom excavation system, wherein the crushing blade is rotatably installed around an axis of the drill pipe.   The water bottom excavation system according to claim 1, wherein the crushing blade includes a paddle surface for turning water in the riser pipe around an axis of the drill pipe.   The water bottom excavation system according to claim 1, further comprising a fixed crushing blade protruding from the inner peripheral surface of the riser pipe toward the drill pipe. In a bottom drilling system comprising a riser pipe extending from a collection ship arranged on the water toward the bottom of the water, and a drilling mechanism for drilling the bottom of the water at the bottom of the riser pipe,
The excavation mechanism includes a drill pipe disposed in the riser pipe, excavation teeth installed at the bottom end of the drill pipe, and a fixed crush projecting from the inner peripheral surface of the riser pipe toward the drill pipe. A bottom drilling system comprising a blade.   The water bottom excavation system according to any one of claims 1 to 4, wherein the crushing blade and / or the fixed crushing blade are arranged at a plurality of locations at intervals in an axial direction of the drill pipe. In the water bottom excavation method, the riser pipe is arranged from the collection ship arranged on the water toward the water bottom, and the water bottom is excavated on the water bottom side of the riser pipe by a drilling mechanism.
The excavation mechanism is composed of a drill pipe and excavating teeth installed at the end thereof, and an excavation object separated from the bottom by the excavating teeth is lifted toward the collection ship through the riser pipe and the drill pipe. A submerged excavation method characterized by crushing the work to be excavated with a crushing blade that protrudes from the outer peripheral surface of the drill pipe toward the riser pipe and rotates about the axis of the drill pipe.   The water bottom excavation method according to claim 6, wherein a paddle surface is formed on the crushing blade, and the paddle surface rotates water in the riser pipe around an axis of the drill pipe.   While installing a fixed crushing blade that protrudes from the inner peripheral surface of the riser pipe toward the drill pipe, the object to be excavated is collected between the riser pipe and the drill pipe toward the collection ship, The water bottom excavation method according to claim 6 or 7, wherein the excavation object is crushed by the fixed crushing blade. In the water bottom excavation method, the riser pipe is arranged from the collection ship arranged on the water toward the water bottom, and the water bottom is excavated on the water bottom side of the riser pipe by a drilling mechanism.
The excavation mechanism is composed of a drill pipe and excavating teeth installed at the end thereof, a fixed crushing blade protruding from the inner peripheral surface of the riser pipe toward the drill pipe is installed, and the excavating teeth from the bottom of the water A water bottom excavation method, wherein the excavated material is crushed by the fixed crushing blade while the separated excavated material is collected toward the collection ship through the riser pipe and the drill pipe.

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