JPS6035519B2 - Riser tube for floating platform - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floating platform riser tube for conveying oil produced from equipment located on the seabed to an offshore floating platform.

A base is used to produce oil on the seabed using equipment installed on the seabed and to transport it from a base 2 installed on the seabed 1 shown in Figure 1 to an offshore floating platform 3 floating on the water surface W. 2 and platform 3 are simply connected by a flexible pipe 4, which is called the Chinese lantern type, and has been widely adopted. The movement of the flexible pipe 4 becomes extremely unstable due to the force of the tidal current, and excessive force is applied to the flexible pipe 4.

Therefore, although flexible pipe 4 has flexibility but is inherently weaker than metal pipes, its durability is reduced, its lifespan is shortened, requiring frequent replacement, and there is a possibility of sudden breakage. There was also the problem of high sex. Also, the second
As shown in the figure, if a buoy 5 is installed in the middle of the flexible pipe 4 suspended from the platform 3 to use it as an intermediate point, the movement of the flexible pipe 4 is better than the system using only the flexible pipe 4 without an intermediate point. is stable, but at the connection point with platform 3,
The platform 3 is greatly influenced by the movement of the platform 3 due to wind and waves, and is subject to excessive force and bending.In addition, the lower part of the platform 3 is also directly affected by the force of the tidal current, which is generally higher the closer it is to the water surface W, which reduces the durability of the flexible pipe 4. Lower it.

Next, as shown in FIG. 3, in order to connect the offshore platform 3 that moves due to wind and waves and the base 2 fixed to the seabed 1, the flexible pipe 4 is not used.
A riser pipe similar to that of a drilling ship using a riser pipe 6 made of a metal pipe is also used. This moves the hanging element 10 of the riser pipe 6 to the tower 7 on the platform 3.
The platform is constantly suspended via a pulley 8 attached to the mooring element 11 using a hydraulically driven automatically adjustable tensioning device 9 so that the tension of the suspension element 10 is always within a certain range. The vertical movement of the ohm 3 prevents excessive tension from being applied to the riser tube 6 or buckling due to negative tension. The riser tube 6 is made of metal but is sufficiently elongated so as to follow the elastic deformation of the riser tube 6.

This method is used temporarily, such as on a drilling ship, and when removed to change tools, it is easy to repair or replace parts, and it does not require large-capacity tensioning equipment to disconnect even in rough weather. There is an advantage.

However, if it is to be used semi-permanently and while connected even during stormy weather, long-term durability is required, and the movement of platform 3 becomes extremely large during stormy weather. The tensioning device 9 would have a very large capacity, making it impractical.

If this self-adjusting tensioning device 9 breaks down, it will be destroyed almost instantaneously due to excessive tension or wind. Therefore, it is necessary to have a standby device that has sufficient reliability and can be activated immediately in the event of a failure. The drawback is that it costs a lot of money.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and to prevent excessive force from being applied to a flexible pipe connecting a base on the seabed and a platform on the ocean. It is an object of the present invention to provide a riser tube for a floating platform that makes it possible to increase durability.

That is, the riser tube for a floating platform of the present invention is
In a riser pipe that transports oil from a base on the seabed to a floating platform on the ocean, an intermediate point in the water above the base, which carries oil to the base and has relatively little movement, is provided; The platform is held in the water at a sufficient horizontal distance from the intermediate point, and a trumpet-shaped guide having a sufficiently large radius of curvature is provided at the bottom of the platform below the conduit suspended via the rotary joint. , by connecting the lower part of the conduit, through the trumpet-shaped guide, to the intermediate point in the water with a flexible pipe that maintains sufficient slack; It is also an effective configuration to install a flexible pipe that is connected to the flexible pipe that connects up to the midpoint of the platform, and that extends to the platform side.

Embodiments of the present invention will be described below with reference to the drawings.
Components that are the same as those in the conventional example from the figures to FIG. 3 are indicated by the same part numbers.

First, a method of providing a base 2 on the seabed 1 and an underwater midpoint indicated by an arrow M that passes through the base 2 and is relatively less likely to move due to tidal currents etc. in the water above the base 2 is as follows. Many types can be considered depending on the conditions of use and economic efficiency, and the safest type of pipe is the 4th type.
As shown in Embodiment 1 in the figures, a fixing column 13 fixed to the base 2 is provided, but this type is the most expensive, and if the height is large, problems such as easy to fall occur.

Therefore, in the case of deep water, as shown in Embodiment 2 in FIG. There is a type that stands upright underwater while allowing some inclination to reduce the overturning moment, and the tops of the fixed column 13 in Fig. 4 and the inclined column 14 in Fig. 5 are the intermediate points in the water indicated by arrow M. .

Embodiment 3 of the present invention shown in FIG. 6 is the cheapest type, and instead of the rigid pillars in Embodiments 1 and 2,
Here, too, a flexible pipe is used alone as the riser pipe 16, and at the intermediate point in the water indicated by the arrow M, an underwater pool 17 moored to the seabed 1 with a mooring element 11 and a sinker 21 is used. As the current becomes deeper, the current becomes smaller, so this format may also be possible.

Next, the riser tube for the floating platform of the present invention,
The connection part between the platform 3 moored to the seabed 1 by the mooring element 11 and the sinker 21 and the intermediate point indicated by the arrow M will be explained based on the third embodiment of FIG. This can be similarly applied to each of the first and second embodiments shown in FIGS.

First, a conduit 18 of sufficient length is suspended via a rotary joint 12 from the bottom of a floating platform 3 moored at a sufficient horizontal distance from an intermediate point in the water indicated by an arrow M. The lower part and the intermediate point M in the water are connected by a flexible pipe 4 that maintains sufficient slack, and a trumpet-shaped guide 19 having a sufficiently large radius of curvature is provided at the lower part of the pipe 18. The trumpet-shaped guide 19
By installing a flexible pipe 4 inside the platform 3 and the conduit 1, it is possible to prevent the platform 3 and the conduit 1 from being
8, the flexible pipe 4 is prevented from being excessively bent at the lower part of the conduit 18.

In FIG. 6, oil produced on the seabed is transferred from a submarine pipeline 20 to a platform via a conduit 18 and a rotary joint 12 by a flexible pipe 4 passing through a base 2, an underwater intermediate point M, and a trumpet-shaped guide 19. Oil is sent to 3.

Here, the rotary joints 12 provided between the platform 3 and the conduit 18 in FIG. 6 and between the base 2 of the seabed 1 and the inclined column 14 in FIG. 5 are ball joints or universal joints. be able to.

In addition, if the ball joint is a single pipe, it is possible to use the inside of the joint as a conduit, but since it is necessary to pass a pig through, etc.
It is inappropriate if the cross-sectional shape of the pipe is made uniform and the minimum radius of curvature is given.

In the case of multiple pipes or a universal joint, the flexible pipe 4 is used to pass through the center or the periphery of the pipe, and in the case of a universal joint, each pipe is placed on the axis of the two orthogonal axes of the cross pin. It is also possible to perform piping without using the flexible pipe 4 via two arranged swivel pipe joints. Furthermore, in the case of deep water, the conduit for the rotary joint 12 on the base 2 on the seabed 1 is connected to the four pillars by a spirally wound metal pipe in order to save the trouble of repair and inspection.
It is also possible to connect while allowing a small angle inclination.

On the other hand, in the riser pipe for a floating platform of the present invention, the inside of the conduit 18 is also connected to the flexible pipe 4 connected from the lower part of the conduit 18 to the intermediate point M in the water,
In addition, a flexible pipe that fits on the platform 3 side may be used, and in this case, the conduit 18 is not necessarily of a closed type, but may have a structure that simply supports the flexible pipe 4.

Next, the action of the flexible pipe 4 connecting the lower part of the conduit 18 and the intermediate point M in the water to follow the movement of the conduit 18 will be explained with reference to FIGS. 7 and 8. 19, the movement of the conduit 18 due to the movement of the platform 3 is attenuated, and the tidal current force acting directly on the conduit 18 is averaged, so that only the movement of the lower part of the conduit 18 is caused between the lower end of the conduit 18 and the midpoint in the water. It acts on the flexible pipe 4 connecting between M and the flexible pipe 4 in that part maintains sufficient slack,
Since it has a U-shape with a large radius of curvature, the movement of the conduit 18 suspended from the platform 3 and acting like a pendulum can be easily absorbed as shown in FIGS. 7 and 8.

Further, since the U-shaped flexible pipe 4 is located in a sufficiently deep sea, the force of the tidal current is small, and the force acting on the flexible pipe 4 is also small. Furthermore, a trumpet-shaped guide 19 provided at the lower part of the conduit 18 serves to prevent excessive bending in the trailing portion of the flexible pipe 4 forming a U-shape with the conduit 18.

Therefore, in the riser pipe for a floating platform of the present invention, the connection part with the platform which moves while being exposed to the harshest conditions for a flexible pipe, and the part below it which is close to the water surface and receives the force of fast tidal currents. However, since the flexible pipe is protected or supported by the conduit and the trumpet-shaped guide, it has the advantage that excessive force is not applied to the flexible pipe and its durability is not impaired.As a result, the reliability of the riser pipe is improved. can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1, 2 and 3 are schematic layout diagrams of different conventional examples of equipment for transporting oil from a base on the seabed to an offshore platform;
5 and 6 are schematic layout diagrams of riser tubes for a floating platform in different embodiments of the present invention, FIG. 4 is the first embodiment, FIG. 5 is the second embodiment, and FIG.
Figure 6 shows the third embodiment, and Figures 7 and 8 show the 6th embodiment.
FIG. 3 is a schematic layout diagram of main parts showing the movement of the conduit and the following action of the flexible pipe in the riser pipe shown in the figure.

1...Undersea, 2...Base, 3...
... Platform, 4 ... Flexible hose, 11 ... Mooring element, 12 ... Rotating joint, 18 ... Conduit, 19 ... ...Trumpet-shaped guide, M...Midway point in the water, W...Water surface.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. In a riser pipe that transports oil from a base installed on the seabed to a platform floating on the ocean, a riser pipe that communicates with the base and has relatively little movement is placed in the water above the base. An intermediate point in the water is provided, the platform is moored in the water at a sufficient horizontal distance from the intermediate point, and a sufficiently large vessel is attached to the lower part of the conduit suspended via a rotating joint at the bottom of the platform. A floating device characterized in that a truss-shaped guide having a radius of curvature is provided, and a flexible pipe with sufficient slack is connected from the lower part of the conduit through the ridge-shaped guide to the intermediate point in the water. Riser tube for type platform. 2. A flexible pipe is provided inside the conduit and is connected to a flexible pipe connecting the lower part of the conduit to an intermediate point in the water, and communicates with the platform side, as stated in claim 1. Riser tube for floating platform.