JP4427441B2 - Riser system - Google Patents

Description

  The present invention relates to a riser system used when excavating seabed ground.

  A riser system is used for investigation of deep seabed. As shown in FIG. 1, the riser system lowers the riser pipe 2 from the ship 1 anchored on the sea, causes the drill pipe 3 to reach the seabed ground G through the inside of the riser pipe 2, and excavates the seabed ground G.

The lower end 2a of the riser pipe 2 is fixed to the seabed ground G. A support tube 4 fixed to the ship 1 is inserted into the upper end portion 2b of the riser tube 2, whereby the riser tube 2 and the support tube 4 have a double tube structure inside and outside, and can be relatively moved in the vertical direction. A simple telescopic mechanism. With such a configuration, the vertical movement of the ship 1 due to waves is absorbed.
Further, the upper end portion 2 b of the riser pipe 2 is supported on the ship 1 side via the tensioner 5. The tensioner 5 includes a tensioner cylinder 6 having one end 5a fixed to the ship 1 and the other end 5b fixed to the riser pipe 2, and applying tension in a direction in which the one end 5a and the other end 5b approach each other. The tension applied by the tensioner cylinder 6 prevents the riser tube 2 from buckling.

In the riser system, the vertical movement of the ship 1 due to the waves can be absorbed by being fixed to the submarine ground G and the ship 1 with the above-described configuration. If the vertical movement exceeds the allowable amount, the fixing portion of the riser pipe 2 to the seabed ground G and the connecting portion to the ship 1 may be damaged.
For this reason, the fixing part 7 which fixes the riser pipe 2 to the seabed ground G is made to be vertically divided, and the riser pipe 2 is separated from the seabed ground G by dividing the fixing part 7 vertically when necessary. (For example, refer to Patent Document 1).
Then, when the riser pipe 2 is separated from the seabed ground G, the riser pipe 2 rises due to the tension of the tensioner 5, so the tensioner 5 is controlled to stop the riser pipe 2 at an appropriate position, and then the riser pipe 2 2 is secured to the ship 1 side.

Japanese Patent Laid-Open No. 10-311191

  However, after the riser pipe 2 is moved up and down largely after the riser pipe 2 is separated from the seabed ground G until it is secured to the ship 1 side, the rising riser pipe 2 pushes up the submerged ship 1. The riser pipe 2 and the ship 1 may be damaged.

  As shown in FIG. 6, the upper end 2b of the riser pipe 2 is supported in a state in which only downward movement is restricted by the support ring 8 to which the other end 5b of the tensioner 5 is fixed. For this reason, when the riser pipe 2 is separated from the seabed ground G, the upper end 2b of the riser pipe 2 greatly jumps upward from the support ring 8 due to the tension of the tensioner 5, and the ship 1 is pushed up. Sometimes.

Even in a state after the riser pipe 2 is tied to the ship 1 side, if the ship 1 moves up and down greatly, the riser pipe 2 may hit the seabed ground G when the ship 1 sinks. The tube 2 may be damaged.
The present invention has been made based on such a technical problem, and prevents the riser pipe from hitting the seabed ground and the ship when the riser pipe is separated from the seabed ground, and prevents damage to the ship and the riser pipe. It is an object of the present invention to provide a riser system that can be used.

  For this purpose, the riser system of the present invention includes a riser pipe whose upper end is supported so as to be movable up and down with respect to a marine vessel, and a drill pipe that reaches the seabed ground through the riser pipe and excavates the seabed ground. And a fixing device that fixes the lower end of the riser pipe to the seabed ground and that can release the riser pipe to the seabed ground when necessary, and a tensioner that applies tension to the riser pipe in the direction to draw the riser pipe to the ship side. And comprising. In such a riser system, a resistance member that exhibits resistance when the riser pipe rises in the sea is provided on the surface of the riser pipe. In an emergency or the like, when the riser pipe is fixed to the seabed ground by the fixing device, the riser pipe rises in the sea due to the tensioner tension. At this time, the rising speed of the riser tube can be suppressed by the resistance force exerted by the resistance member. Thereby, it is possible to prevent the raised riser pipe from hitting the ship.

Such a resistance member may be fixed on the surface of the riser pipe, but in the normal state, that is, when the riser pipe is fixed to the seabed ground by the fixing device, the influence of the tidal current is increased by the resistance member. It is not preferable. For this reason, the resistance member is positioned along the surface of the riser pipe when the lower end of the riser pipe is fixed to the seabed ground by a fixing device, and the fixing of the riser pipe to the seabed ground is released by the fixing device. Then, it is preferable that the movable plate is configured to be open with respect to the surface of the riser tube. In this case, when the riser pipe is separated from the seabed ground, it is necessary to reliably open the movable plate. For this reason, for example, the movable plate may be forcibly opened by a motor, a cylinder, a spring, etc., but the upper end of the movable plate may be opened by the resistance force of seawater when the riser pipe rises in the sea. If an inclined surface is formed in the part, the movable plate can be opened without using any mechanism.
In addition, the movable plate is formed of a material that causes buoyancy to act on the movable plate in the sea, so that the movable plate can be placed along the riser pipe at normal times without using any mechanism.

  Karman vortices are generated around the riser pipe in the sea due to tidal currents. On the other hand, by arranging the resistance members in a spiral manner on the surface of the riser tube, it is possible to shift the generation phase of the Karman vortex and suppress the vibration caused by the Karman vortex.

Moreover, it is preferable that the lower end part of such a riser pipe is provided with a contraction mechanism that allows the length of the riser pipe to be contracted in a state in which the riser pipe is fixed to the seabed ground by a fixing device.
At this time, in the contraction mechanism, if the riser pipe is automatically contracted when the fixing of the riser pipe to the seabed ground is released by the fixing device, the riser pipe is almost simultaneously with the separation of the riser pipe. The lower end of the pipe can be moved away from the seabed, and interference with the seabed ground can be prevented.

  Furthermore, you may make it provide the displacement relaxation mechanism which relieve | moderates the displacement with respect to the tensioner of a riser pipe | tube between a riser pipe | tube and a tensioner. Thereby, when a riser pipe | tube is cut | disconnected from the seabed ground and it raises, the displacement can be relieved with a displacement mitigation mechanism, and the collision to a ship can be prevented.

The riser system of the present invention includes a riser pipe whose upper end is supported so as to be movable up and down with respect to a marine vessel, a drill pipe that reaches the seabed ground through the riser pipe, and excavates the seabed ground. A fixing device capable of fixing the lower end portion to the submarine ground and releasing the fixing of the riser pipe to the submarine ground when necessary, and a tensioner that applies tension to the riser pipe in a direction to draw the riser pipe to the ship side, The lower end portion of the riser pipe is provided with a movable pipe that can be moved up and down with respect to the riser pipe and connected to the fixing device, and a biasing member that biases the movable pipe upward. It is characterized by.
In such a riser system, when the fixing of the lower end of the riser pipe to the seabed ground is released by the fixing device, the movable pipe connected to the fixing member is moved against the riser pipe by the biasing force of the biasing member. To rise. As a result, the entire length of the riser pipe contracts, and the distance between the lower end of the riser pipe and the seabed ground is increased. As a result, the riser pipe can be prevented from colliding with the seabed ground.

  Moreover, the riser system of this invention is provided with the displacement control mechanism which controls the upward displacement with respect to the tensioner of a riser pipe | tube between a riser pipe | tube and a tensioner. Thereby, when a riser pipe | tube is cut | disconnected from the seabed ground and it raises, the displacement can be controlled with a displacement control mechanism, and it can prevent hitting a ship etc.

  According to the present invention, after disconnecting from the seabed ground in an emergency or the like, the riser pipe effectively avoids damage to the riser pipe and the ship by pushing up the ship or colliding with the seabed ground. Is possible.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a diagram for explaining a configuration of a riser system 10 in the present embodiment.
As shown in FIG. 1, a riser system 10 used for surveying deep seabed ground and excavating resources such as oil and natural gas includes a cylindrical riser pipe 11 and a seabed ground G through the inside of the riser pipe 11. And a drill pipe 12 that excavates the seabed ground G.

The riser tube 11 is configured by connecting a large number of unit tubes 13 having a predetermined length.
As shown in FIG. 2, a resistance member 15 that exerts a resistance force when the riser pipe 11 ascends in the sea is provided on the outer surface of each unit pipe 13 constituting the riser pipe 11.
An example of such a resistance member 15 is a retractable flap (movable plate) 15A. The lower end of the flap 15A is rotatably connected to the outer surface of the riser tube 11 via a hinge 16, and the opening angle with respect to the riser tube 11 is regulated by a stopper member (not shown). ing. As a result, the flap 15 </ b> A can be opened and closed between a state along the outer surface of the riser pipe 11 and a state opened at a predetermined angle with respect to the riser pipe 11. The upper end of the flap 15A is preferably an inclined surface 15a so that when the riser pipe 11 is lifted, a force in the direction of opening the flap 15A is exerted by the resistance of seawater.

The flap 15A is preferably maintained in a state along the outer surface of the riser pipe 11 in order to minimize the influence of the tidal current in a normal state. For this reason, the flap 15A can be formed of a material that causes buoyancy to act on the flap 15A in the sea, such as a material containing bubbles, referred to as a syntactic foam or the like. Thereby, in the normal state, the flap 15A is in a state along the outer surface of the riser pipe 11 due to the buoyancy acting on the flap 15A, and when the riser pipe 11 is raised, seawater hits the inclined surface 15a, so that the flap 15A It can be opened automatically.
In addition to this, the flap 15A may be biased by an elastic member such as a spring so that the flap 15A maintains a state along the outer surface of the riser tube 11.
For example, it is preferable to provide a plurality of the flaps 15A at a predetermined level in the vertical direction of the unit tube 13 at substantially equal intervals in the circumferential direction.

  Such a flap 15A opens at a predetermined opening angle with respect to the riser pipe 11 due to the resistance of seawater when the riser pipe 11 starts to rise. When the flap 15A is opened, it functions as a resistance member 15 that exerts resistance against the rise of the riser pipe 11.

Further, as shown in FIG. 3, the flaps 15 </ b> A may be arranged in a spiral shape with respect to the unit tube 13 constituting the riser tube 11. In the sea, Karman vortices are generated by the tidal current hitting the riser pipe 11, and this may cause vibration in the riser pipe 11 perpendicular to the flow. This vibration may cause the riser tube 11 to fatigue and adversely affect the strength. When the flap 15A is spirally arranged in such a riser pipe 11, the flow of seawater around the riser pipe 11 is changed by the flap 15A, and a phase shift occurs in the vertical direction of the riser pipe 11, thereby suppressing vibration.
Accordingly, the flap 15 </ b> A not only functions as the resistance member 15 that exerts resistance against the rise of the riser tube 11, but also functions to suppress vibration due to the generation of Karman vortices around the riser tube 11. You can also.

  Now, the lower end portion 11 a of the riser pipe 11 is fixed to the seabed ground G via an anti-blowing device (fixing device) 20. The spray prevention device 20 includes a pressure release mechanism for preventing the riser pipe 11 from being blown off when gas or the like is ejected from the seabed ground G during excavation. This blow-proof device 20 is also provided with a separation mechanism for separating the riser pipe 11 from the seabed ground G during stormy weather or the like. For this reason, the blow-proof device 20 is divided into two parts including a base part 20A fixed to the seabed ground G, and a connecting part 20B that is detachable from the base part 20A and connected to the lower end part 11a of the riser pipe 11. Possible configuration. The connecting portion 20B is normally connected to the base portion 20A, and when necessary, the connection to the base portion 20A is released by control or the like from the ship 1 side.

  Further, the blow prevention device 20 is provided with a cutting mechanism (not shown) for cutting the drill pipe 12 passing through the riser pipe 11. When the connecting portion 20B and the riser pipe 11 are separated from the base portion 20A by the separation mechanism of the blow-proof device 20, the drill pipe 12 is usually pulled up first, but there is no time to lift the drill pipe 12 or the like. After cutting the drill pipe 12 passing through the riser pipe 11 with this cutting mechanism (not shown), the disconnecting mechanism separates the connecting portion 20B and the riser pipe 11 from the base portion 20A.

The structure of the part connected with respect to the connection part 20B of the anti-injection apparatus 20 in the lower end part 11a of the riser pipe | tube 11 is the following contraction mechanisms.
That is, as shown in FIG. 4, the lower end portion 11 a of the riser tube 11 is configured such that the movable tube 22 is attached to the tube body 21 so as to be movable in the vertical direction. Flange 21a, 22a is formed in the lower end part of the pipe main body 21, and the upper end part of the movable pipe 22, and the downward movement of the movable pipe 22 is controlled by this. And between the flange 22a of the movable tube 22 and the tube main body 21, when the movable tube 22 moves upward, the urging member 23 that emits the urging force in the direction of pulling up the movable tube 22 has its moving speed. A damper 25 for damping is provided.

Further, the movable tube 22 is provided with a stopper mechanism for fixing the movable tube 22 to the tube main body 21 in a state where the lower end position of the moving stroke, that is, the flanges 21a and 22a are in contact with each other. This stopper mechanism is configured to release the movable tube 22 so as to be movable with respect to the tube main body 21 when the connecting portion 20B of the blow-proof device 20 is disconnected from the base portion 20A.
As such a stopper mechanism, for example, there is a mechanism in which a stopper pin 24 is inserted into a hole formed in a predetermined position of the tube main body 21. The stopper pin 24 is positioned immediately below the flange 21a of the tube main body 21 in a state where the stopper pin 24 is inserted into the hole of the tube main body 21, thereby restricting the upward movement of the movable tube 22. Then, for example, the stopper pin 24 is connected to the base portion 20A of the blow-proof device 20 with a wire 26 or the like, so that the connecting portion 20B of the blow-proof device 20 is disconnected from the base portion 20A and the riser pipe 11 is raised. When this occurs, the stopper pin 24 is removed from the hole of the tube body 21.
In addition to this, for example, a mechanism for inserting / removing the stopper pin 24 into / from the hole of the tube main body 21 is provided, and the stopper pin 24 is automatically moved when the connecting portion 20B of the blow-proof device 20 is separated from the base portion 20A. The tube body 21 can be removed from the hole.

  Since the lower end portion 11a of the riser tube 11 has the contraction mechanism having such a structure, as shown in FIG. 4B, the connecting portion 20B of the blow-proof device 20 is separated from the base portion 20A, and the riser tube 11 Is raised, the stopper mechanism is released, the movable tube 22 becomes movable with respect to the tube main body 21, and the movable tube 22 rises with respect to the tube main body 21 by the urging force of the urging member 23. This shortens the entire length of the riser pipe 11, secures a large gap between the lower end portion 11a and the connecting portion 20B of the riser pipe 11 and the seabed ground G, and the riser pipe 11 unnecessarily interferes with the seabed ground G and lower end section 11a. It is possible to prevent the connecting portion 20B from being damaged. In addition, the movable tube 22 moves immediately after the connecting portion 20B of the blow-proof device 20 is disconnected from the base portion 20A and the stopper mechanism is released, and the interval between the lower end portion 11a of the riser tube 11 and the seabed ground G is increased. So the effect is great.

As shown in FIG. 5, the upper end portion 11b of the riser pipe 11 has a telescopic mechanism. That is, the support pipe 30 fixed to the ship 1 is inserted into the upper end portion 11b of the riser pipe 11, and thereby the riser pipe 11 and the support pipe 30 have a double pipe structure inside and outside, and can be relatively moved in the vertical direction. Thus, relative movement in the vertical direction between the ship 1 and the riser pipe 11 is allowed.
A flange 31 is formed on the upper end portion 11b of the riser pipe 11 so as to project outward. A ring-shaped support ring 32 is provided below the flange 31. The support ring 32 is restricted from moving upward with respect to the riser pipe 11 by the flange 31.

  The support ring 32 is connected to the ship 1 via a tensioner 33. The tensioner 33 includes a tensioner cylinder 34 having one end 33a fixed to the ship 1 and the other end 33b fixed to the support ring 32, and applying tension in a direction in which the one end 33a and the other end 33b approach each other. As a result, the upper end portion 11 b of the riser pipe 11 is supported by the ship 1 in a state where a tension in a direction to be drawn toward the ship 1 is applied via the support ring 32 and the tensioner 33.

Here, between the support ring 32 and the flange 31 of the riser pipe 11, a mechanism (a displacement relaxation mechanism, a displacement restriction mechanism) that suppresses the upward movement of the riser pipe 11 relative to the support ring 32 is provided. As this mechanism, a biasing member 35 that applies a biasing force in a direction in which both the support ring 32 and the flange 31 of the riser pipe 11 approach each other, and the upward movement of the riser pipe 11 with respect to the support ring 32. And a damper 36 for damping the speed. The urging member 35 and the damper 36 can suppress the upward movement of the riser pipe 11 with respect to the support ring 32, thereby causing the riser pipe 11 to rise excessively and hit the ship 1, and the tensioner 33. It is possible to prevent an excessive compressive force from acting on the cylinder 34.
Further, since the support ring 32 and the riser pipe 11 are connected by the above-described mechanism, downward tension by the tensioner 33 can be transmitted to the riser pipe 11 via the support ring 32, and this also causes the riser pipe 11 to Excessive rise can be suppressed.

In the riser system 10 having such a configuration, the lower end portion 11a of the riser pipe 11 is fixed to the seabed ground G via the anti-injection device 20, and the upper end portion 11b is connected to the ship 1 via the support pipe 30 and the tensioner 33. Support with. Then, the drill pipe 12 is rotated by a driving source (not shown) in a state where the drill pipe 12 reaches the sea bed ground G through the inside of the riser pipe 11, thereby excavating the sea bed ground G.
In this state (normal state), the riser pipe 11 and the support pipe 30 constitute a telescopic mechanism to absorb the vertical movement of the ship 1 due to waves. In this state, the tensioner 33 provided with the tensioner cylinder 34 pulls the riser pipe 11 upward to apply tension, thereby preventing the riser pipe 11 from buckling.

  And when the vertical movement of the ship 1 becomes more than the allowable amount during stormy weather or the like, the blow-proof device 20 is separated into the base portion 20A and the connecting portion 20B. Then, the riser pipe 11 is raised by the tension applied by the tensioner 33. At this time, the flap 15 </ b> A provided on the outer surface of the riser pipe 11 opens at a predetermined opening angle with respect to the riser pipe 11 due to the resistance of seawater to exert a resistance force, and suppresses the rising speed of the riser pipe 11. Further, the upward movement of the riser pipe 11 is also suppressed by the urging member 35 and the damper 36. As a result, it is possible to prevent the riser pipe 11 from rising excessively and hitting the ship 1 and applying an excessive compressive force to the tensioner cylinder 34 of the tensioner 33. Further, when the riser pipe 11 is raised, the tension exerted by the tensioner cylinder 34 of the tensioner 33 is appropriately controlled to stop the riser pipe 11 at an appropriate position, and then the riser pipe 11 is secured to the ship 1 side.

Further, as soon as the riser pipe 11 is disconnected, the movable pipe 22 rises due to the urging force of the urging member 23 and the overall length of the riser pipe 11 is shortened, so that the riser pipe 11 interferes with the seabed ground G unnecessarily. It can prevent that the lower end part 11a and the connection part 20B are damaged.
In the state after the riser pipe 11 is secured to the ship 1, even if the ship 1 moves up and down largely unexpectedly, the lower end portion 11a and the connecting portion 20B of the riser pipe 11 collide with the seabed ground G or the like. Since the upward movement of the riser pipe 11 is suppressed by the biasing member 35 and the damper 36 on the upper end portion 11b side of the riser pipe 11, the riser pipe 11 rises excessively and hits the ship 1. In addition, it is possible to prevent an excessive compressive force from acting on the tensioner cylinder 34 of the tensioner 33.

  In this way, it is possible to effectively avoid the riser pipe 11 after being disconnected in an emergency from pushing up the ship 1 or colliding with the seabed ground G and damaging the riser pipe 11 or the ship 1. Is possible.

  In the above-described embodiment, the resistance member 15 and the structure of the lower end portion 11a and the upper end portion 11b of the riser pipe 11 are appropriately adopted as long as the same function as described above can be exhibited. There is no problem. In addition to this, as long as the gist of the present invention is not deviated, the configurations described in the above embodiments can be selected or changed to other configurations as appropriate.

It is a figure which shows the outline | summary of the riser system in this Embodiment. It is a figure which shows an example of the resistance member provided in the riser pipe. It is a figure which shows the other example of a resistance member. It is a figure which shows a state when cut | disconnecting the lower end part of a riser pipe | tube. It is a figure which shows the support structure of the upper end part of a riser pipe | tube. It is a figure which shows the support structure of the upper end part of the conventional riser pipe | tube.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ship, 10 ... Riser system, 11 ... Riser pipe, 12 ... Drill pipe, 13 ... Unit pipe, 15 ... Resistance member, 15A ... Flap (movable plate), 15a ... Inclined surface, 16 ... Hinge, 20 ... Anti-jet Device (fixing device), 20A ... base portion, 20B ... coupling portion, 21 ... pipe body, 22 ... movable tube, 23 ... biasing member, 24 ... stopper pin, 30 ... support tube, 31 ... flange, 32 ... support ring 33 ... Tensioner, 34 ... Tensioner cylinder, 35 ... Biasing member, 36 ... Damper, G ... Submarine ground

Claims (9)

A riser pipe whose upper end is supported so as to be movable up and down with respect to the ship at sea;
A drill pipe that reaches the seabed ground through the riser pipe and excavates the seabed ground;
Fixing the lower end of the riser pipe to the seabed ground, and a fixing device capable of releasing the riser pipe to the seabed ground when necessary;
A tensioner that acts on the riser pipe with a tension in a direction to draw the riser pipe toward the ship,
A riser system characterized in that a resistance member is provided on the surface of the riser pipe to exert resistance when the riser pipe rises in the sea.   The resistance member is positioned along a surface of the riser pipe in a state where a lower end portion of the riser pipe is fixed to the seabed ground by the fixing device, and fixing the riser pipe to the seabed ground is the fixing device. 2. The riser system according to claim 1, wherein the riser system is a movable plate that is open and positioned with respect to a surface of the riser tube in a state where the riser tube is released.   The riser system according to claim 2, wherein an upper end portion of the movable plate is formed with an inclined surface so that the movable plate is opened by a resistance force of seawater when the riser pipe rises in the sea. .   The riser system according to claim 2, wherein the movable plate is made of a material that causes buoyancy to act on the movable plate in the sea.   The riser system according to claim 1, wherein the resistance members are arranged in a spiral shape on a surface of the riser tube.   The lower end portion of the riser pipe includes a contraction mechanism that allows the length of the riser pipe to contract in a state where the riser pipe is fixed to the seabed ground by the fixing device. Item 6. The riser system according to any one of Items 1 to 5.   The riser system according to claim 6, wherein the contraction mechanism automatically contracts the length of the riser pipe when the fixation of the riser pipe to the seabed ground is released by the fixing device. .   The riser system according to any one of claims 1 to 7, further comprising a displacement relaxation mechanism that relaxes a displacement of the riser tube relative to the tensioner between the riser tube and the tensioner. A riser pipe whose upper end is supported so as to be movable up and down with respect to the ship at sea;
A drill pipe that reaches the seabed ground through the riser pipe and excavates the seabed ground;
Fixing the lower end of the riser pipe to the seabed ground, and a fixing device capable of releasing the riser pipe to the seabed ground when necessary;
A tensioner that acts on the riser pipe with a tension in a direction to draw the riser pipe toward the ship,
The lower end portion of the riser pipe is provided with a movable pipe connected to the fixing device and capable of moving up and down with respect to the riser pipe, and an urging member for urging the movable pipe upward. Riser system characterized by being.

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