JP2593664Y2 - Long underwater pipe - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long underwater pipe suspended from a marine structure such as a ship floating on the sea when developing a submarine resource such as an offshore oil field drilling.

[0002]

2. Description of the Related Art As shown in FIG. 4, the above-mentioned long underwater pipe is suspended from the bottom of a ship 2 floating on the sea 1, and is disposed with its lower end fixed to the sea floor 3. In addition, before and after fixing the long underwater large pipe 4 to the seabed 3, there is a danger that the fishing will take place in the seawater and become extremely unstable. The underwater large pipe 4 is composed of a plurality of cylindrical steel pipes having a large bending rigidity and a high Young's modulus, and these cylindrical steel pipes are connected to each other via a joint member. It is a long tube.
A drilling pipe 6 having a drilling drill 5 attached to the lower end thereof is inserted from the vessel 2 into the inside of the large underwater large pipe 4 and is drooped down to the seabed 3. Development is being carried out.

[0003]

Since the ship 2 floating on the sea surface 1 is oscillated by ocean waves, the large underwater pipe 4 is fixed to the sea floor 3 and separated from the sea floor 3. In the later underwater fishing state, longitudinal vibration occurs in the long underwater pipe 4. The natural period of longitudinal vibration of the long underwater pipe 4 is: Tp: natural period of longitudinal vibration (sec), L: total length of the long underwater pipe, E: Young's modulus, A: cross-sectional area of the pipe, and m: cross section of the long underwater pipe. Assuming the apparent mass,

(Equation 1) Becomes On the other hand, the wave cycle Ts of the ocean wave is a wave cycle range up to about 20 seconds, and if the natural cycle Tp of the longitudinal vibration of the long underwater large pipe 4 is within the wave cycle range of the ocean wave, the periods coincide with each other. As a result, a resonance phenomenon occurs, and a very large longitudinal vibration occurs in the long underwater large pipe 4, which may lead to destruction. In particular, when the total length of the long underwater large pipe 4 is set to be 4000 m or more in order to develop the seabed resources in the deep water, the natural cycle of the longitudinal vibration of the long underwater pipe 4 is in the range of the wave cycle Ts of the ocean wave (maximum of 20 seconds). Easy to enter)
It is necessary to design an underwater large-sized tube 4 having an extremely large strength that can withstand a large longitudinal vibration caused by the above-described resonance phenomenon. However, increasing the strength naturally leads to an increase in the weight of the long submerged large pipe 4, and it is difficult to install the long submerged large pipe 4 in the deep sea area with the conventional technology.

The present invention has been made in view of the above circumstances, and provides a large underwater pipe which can be erected from a ship floating on the sea surface even when developing a seabed resource in a deep sea area. The purpose is to:

[0005]

The long underwater pipe of the present invention is
An underwater large pipe hanging from a marine structure such as a ship floating on the sea surface, a plurality of cylindrical portions having a predetermined bending rigidity and a large Young's modulus, and a bending rigidity and a Young's modulus higher than the cylindrical portions. And a plurality of connecting cylindrical tubes that connect the respective cylindrical portions with each other while maintaining watertightness. The connecting cylindrical tubes are flexible in the longitudinal direction.
It is characterized by being formed in a bellows shape that can be freely formed .

[0006]

According to the large underwater pipe of the present invention, a plurality of cylindrical portions having a predetermined length and a large bending stiffness and a large Young's modulus, and the bending stiffness and the Young's modulus are set to be extremely smaller than the cylindrical portions. A plurality of connecting cylindrical pipes for connecting the cylindrical parts while maintaining water tightness , wherein the connecting cylindrical pipes are long.
Since it is formed in a bellows shape that can be flexibly deformed in the hand direction , the overall apparent Young's modulus E becomes smaller, and thereby the natural period of the longitudinal vibration of the long underwater large pipe obtained by Expression 1 becomes longer. That is, the apparent Young's modulus E of the entire underwater long tube of the present invention is 1 compared with the conventional underwater long tube.
When the ratio becomes / 25, the natural period of the longitudinal vibration of the long underwater pipe of the present invention becomes five times. As a result, the total length of the long underwater large pipe is reduced to 40
When the length is 00 m, the natural cycle of the long underwater pipe made of steel according to the prior art has a natural period of about 6 seconds, whereas the natural cycle of the long underwater pipe of the present invention is as long as about 30 seconds. Therefore, when the long underwater pipe of the present invention is used in deep sea water, the natural cycle of its longitudinal vibration is out of the wave cycle range of the ocean wave (up to about 20 seconds) in the underwater fishing state in seawater. No resonance phenomenon occurs and there is no risk of destruction.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a large underwater pipe according to the present invention will be described below with reference to FIGS. The same components as those described with reference to FIG.
The description is omitted.

The large underwater pipe 7 of this embodiment is composed of a plurality of cylindrical parts 8 having high bending rigidity, and flexible pipes (connection cylindrical pipes) 9 connecting the cylindrical parts 8, 8 to each other. However, the lowermost cylindrical portion 8 has a structure that can be fixed on the seabed 3.

Each cylindrical portion 8 has, for example, a diameter of 400 mm.
A steel pipe 8a having a length of about 700 mm and a length of about 30 m is a constituent member, and a plurality of (for example, about 10) steel pipes 8a are provided.
They are directly connected while maintaining watertightness.
As an example of the connection of these steel pipes 8a, 8a, as shown in FIG.
b, 8b are provided, and there is a structure in which the flanges 8b, 8b are integrally connected by bolt fastening means. Further, as another connection structure, as shown in FIG. 2B, a joint member 1 in which internal thread portions 10a and 10b are formed on the inner peripheral surface.
0, a steel pipe 8a having threaded portions 8c formed on the outer periphery of both ends,
A structure that is screwed to 8a and integrally connected is also conceivable. At this time, the internal thread portions 10a and 10b have a reverse thread structure.

The flexible pipe 9 is, as shown in FIG.
It is a bellows-shaped cylindrical tube having a diameter substantially the same as that of the steel pipe 8, formed of a metal material having an extremely small apparent Young's modulus as compared with the steel pipe 8, and sufficient for seawater pressure and fluid pressure inside the pipe. It has a tube structure that can withstand. 2 (a) and 2 (b), while maintaining the watertightness with the end portion of the cylindrical portion 8 while being a member which can be flexibly deformed in the longitudinal direction and the direction orthogonal thereto. It is connected while being.

The large underwater pipe 7 of this embodiment, which is constructed by connecting a flexible pipe 9 between the cylindrical portions 8 and 8 having the above configuration, is connected so that the total length becomes about 4000 m, and is used in a deep sea area. Even if it is used, the overall apparent Young's modulus E becomes small, and as a result,
, The natural period of the longitudinal vibration becomes longer. Accordingly, the natural period Tp is outside the range of the wave period of the ocean wave (up to a maximum of about 20 seconds), so that no resonance phenomenon occurs and there is no possibility of destruction.

[0012]

As described above, the large underwater pipe of the present invention has a plurality of cylindrical portions having a predetermined length of bending rigidity and a large Young's modulus, and has extremely low bending rigidity and Young's modulus than the cylindrical portions. A plurality of connecting cylindrical pipes that are set and connect each cylindrical part while maintaining watertightness ,
The connecting cylindrical tube has a bellows shape that can be flexibly deformed in the longitudinal direction.
Since it is formed , the overall apparent Young's modulus becomes smaller, thereby increasing the natural period of the longitudinal vibration of the long underwater pipe. Therefore, even if the long underwater pipe of the present invention is used in the deep sea, the natural period is out of the range of the wave period of the ocean wave (up to about 20 seconds). There is no danger, and it is possible to develop deep-sea resources in deep water.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a long underwater large pipe according to the present invention is suspended in the sea.

FIG. 2 is a diagram showing a connection structure of cylindrical tubes as constituent members of the present invention.

FIG. 3 is a diagram showing a state in which the cylindrical portions, which are constituent members of the present invention, are connected by a connecting cylindrical tube.

FIG. 4 is a view showing a state in which a conventional long underwater large pipe is suspended in the sea.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 At sea 2 Ship 3 Sea bottom 7 Underwater large pipe 8 Cylindrical part 8a Steel pipe 9 Flexible pipe (connection cylindrical pipe) Tp Natural period of longitudinal vibration of underwater large pipe L Total length of underwater large pipe E Young's modulus of underwater large pipe A Cross-sectional area of m

Claims (1)

(57) [Scope of request for utility model registration] An underwater large pipe suspended from a marine structure such as a ship floating on the sea surface, comprising: a plurality of cylindrical portions having a predetermined bending rigidity and a large Young's modulus; and the cylindrical portions. Bending rigidity and Young's modulus are set to be extremely small, and a plurality of connecting cylindrical tubes are connected to each other while maintaining watertightness , and the connecting cylindrical tubes are freely deformable in the longitudinal direction. Like a bellows
An underwater large tube characterized by being formed .