JPS5948279B2 - flexible riser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible riser device used in offshore oil and natural gas production facilities.

Floating platforms in undersea oil and natural gas production facilities transport oil and natural gas produced from the seabed from a riser base fixed on the seabed to a floating platform on the ocean via a flexible riser device. Generally, mooring is carried out at multiple points using multiple catenary-shaped mooring lines or mooring chains that extend radially, but it can move vertically, horizontally, tilt, and rotate around a vertical axis due to the force of wind and waves. It moves in the downstream direction due to the force of .

On the other hand, the underwater riser base receives not only the force from the movement of the plano I form, but also the force from the current.

The mechanism that connects a floating floating platform on the ocean and a fixed point on the ocean floor that moves in this way is generally called a riser device, but this riser device must follow the movement of the platform, so a flexible riser device is used. equipment is required.

Similar riser equipment is also required for cargo handling equipment from submarine pipelines to floating oil storage tanks and tankers.

Additionally, one type of such flexible riser device includes:
Conventionally, flexible pipes are available, but they have drawbacks in durability and strength, and are therefore unreliable.

Another type of riser device is a riser device that is often used on drilling ships.In this case, the riser device is always suspended from the drilling ship and kept under tension, and is adjusted by an auto-tensioner as the drilling ship moves up and down. However, horizontal movement is followed by elastic deformation of the riser.

However, if it is to be used for a long period of time, it is impractical because it must be able to withstand extremely rough weather and requires a fairly large-capacity auto-tensioner and the power to drive it. , we try not to excavate in rough weather.

As mentioned above, there are problems with the two types currently in use, so a new type of riser device is an articulated type in which the rigid parts are connected with a flexible joint such as a universal joint. Two to two have already been put into practical use.

Therefore, in order to provide even more flexibility, we installed three flexible joints.
It is conceivable to have four or more risers, but on the other hand, if there are four or more degrees of freedom, the movement of the riser becomes unstable, making it impractical except under special constraints.

If we consider a riser device connected by three flexible joints, the riser device bends toward the downstream side of the tidal current, and in that state follows the movement of the platform on the ocean.

In this case, if the angle of inclination of the flexible joint is made to be able to respond to changes in the tidal current in any direction, it will be relatively large, 70°.
In some cases, it can reach .

A universal joint will no longer function as a universal joint when the angle of inclination approaches 90°, but at 70°, problems such as interference are likely to occur, even if there is no mechanical problem.

Therefore, if the universal joint stops following all changes in the tidal current, the angle of inclination of the universal joint can be made relatively small.

Another problem is that riser devices with mechanical parts such as universal joints need to be able to be recovered at sea for maintenance, inspection, and repair, and for this purpose a connecting device is installed under the bottom universal joint. It is necessary to provide it so that it can be separated from the riser base side.

In this case, the connecting device is hidden under the platform, making it difficult to operate from the ocean, making it difficult to approach and connect the connecting device.

Therefore, the present invention was made to eliminate the drawbacks of conventional riser devices, and in a riser device that is connected by three universal joints, the angle of inclination of the universal joints becomes large and the connection is difficult. The purpose of this invention is to provide a special flexible riser device that can solve this problem.

That is, in the flexible riser device of the present invention, the flexible riser that connects the riser base on the seabed and the floating platform on the sea is a vertical riser.

The platform and the vertical riser are suspended via a vertical bearing and a first universal joint, and the vertical riser and the horizontal riser are suspended by a second universal joint. suspended via a universal joint,
The horizontal riser and the upright portion are connected to a third universal joint having two axes, a horizontal axis and a vertical axis perpendicular to the longitudinal direction of the horizontal riser, and a third universal joint that is vertically connected to the third universal joint in a separated state. A lifting device that can be connected via a connecting device that hangs down from the water, has a weight distribution that prevents any part from floating when the connecting device is disconnected underwater, and can lift the vicinity of the third universal joint from the sea side. The connecting device is brought close to the upright part and can be connected, but the horizontal riser is always faced with its upper side facing the upper side and its lower side always facing the lower side. It is desirable that the horizontal riser be formed with a weight distribution that allows the vertical riser to bend upwardly at the end that is suspended from the vertical riser; In addition to running pipes and electric wires, a vertical bearing, a first universal joint, a second universal joint, and a third universal joint are installed.
At each rotating part of the universal joint, connect the pipes and wires with flexible pipes, etc., and at the connection between the connecting device and the upright part, connect the pipes and wires with pipe joints and wire joints, respectively. Accordingly, a more preferable flexible riser device is constructed.

The present invention will be described in detail below with reference to the drawings.

First, the flexible riser device according to the first embodiment of the present invention shown in FIG. 5. A device consisting of a horizontal riser 6 and an upright part 7 provided on the riser base 2. This platform 4 is moored at multiple points by a mooring chain 25 or mooring line, and has a vertical bearing 8 at its bottom.
A vertical riser 5 is suspended via an upper connection device 20 and a first universal joint 9 provided at the lower part of the vertical riser 5, and a horizontal riser 6 is suspended from the lower part of the vertical riser 5 via a second universal joint 10. One end of the horizontal riser 6 is suspended, and a horizontal fork 27 at the other end of the horizontal riser 6 has a third axis consisting of two axes, a horizontal axis 11 and a vertical axis 12 perpendicular to the longitudinal direction of the riser 6, as shown in the enlarged view of FIG. A connecting device 14 is suspended via a third universal joint 13, and this connecting device 14 hangs vertically from the third universal joint 13 in a disconnected state. It can be connected to the top portion 7A of the upright portion 7.

In addition, each part except the platform 4 and the riser base 2 which does not move has a weight distribution that does not allow any part to float when the connection device 14 is connected or disconnected underwater. From 10 and 13, it is suspended like a pendulum.

In addition, a hanging fitting 16 and a hanging rope 17 provided on the upper part of the lower fork 15 of the third universal joint 13, and an underwater buoy 18,
A lifting device from the sea, such as a buoy 19 on the sea surface, is used to bring the connecting device 14 close to the upright portion 7 and enable it to be connected.

Furthermore, by providing a buoyant body 21 on the upper surface side of the horizontal riser 6 and a weight 22 on the lower surface thereof, the upper surface side of the horizontal riser 6 is always opposed to the upper side and the lower surface side is always opposed to the lower side. The horizontal riser 6 is shaped to have a weight distribution, and the end of the horizontal riser 6 which is suspended from the vertical riser 5 is bent upward as shown in FIG.

Furthermore, the flexible riser device having such a configuration is used for production or transportation of oil and natural gas on the seabed 1,
For example, a vertical riser 5. Along the horizontal riser 6 and upright part 7, or
or vertical riser 5, horizontal riser 6 and riser base 2
The vertical bearing 8 and the respective universal joints 9, 10 and 13 are connected to each other by fixed pipes and fixed electric wires on the upright part 7, and for the rotation of the vertical bearing 8 and the respective universal joints 9, 10, 13, swivel pipe joints, slip rings, etc. They are directly connected to each other by pipe joints and wire joints.

In the flexible riser device of the present invention having the above-described configuration, when the force of the seawater current acts from the platform 4 toward the riser base 2, a force acts to bend the horizontal riser 6 in the direction that it floats, causing the riser to become unstable. For stability, the platform 4 needs to be located downstream of the riser base 2.

Platform 4 mooring line or mooring chain 25
From this point of view, it makes sense because the platform 4 is moved to the downstream side of the tidal current to counterbalance the effects of wind and waves.

There, at the bottom of the platform 4 there is a vertical bearing 8, a third universal joint 1 at the top 7A of the upright part 7 of the riser base 2.
The vertical axis 12 of 3 allows the platform 4 to move directionally downstream of the riser base 2 for changes in the direction of the current over a certain angular range.

Here, a certain range of angle means that in the third universal joint 13 having a special shape as shown in FIG.
The rotation of the horizontal riser 6 about the vertical axis 12 of the universal joint 13 will be less than 180°, with a maximum of about 150° being considered appropriate.

Moreover, if the lower fork 15 is provided only on one side, as in the flexible riser device according to the second embodiment of the present invention shown in FIG. 3, a maximum rotation of nearly 300 degrees is possible.

Furthermore, instead of using the third universal joint 13 as a universal joint as shown in FIG. 2 or 3, as shown in the flexible riser device of the third embodiment of the present invention in FIG. The vertical bearing 24 attached to the vertical bearing 24 and the horizontal riser 6 attached to the top
The platform 4 can be disassembled into a horizontal bearing 23 connected to a horizontal fork 27 perpendicularly to the longitudinal direction of the platform 4, in which case the platform 4 can rotate 360° around the riser base 2.

Note that in place of the specially shaped third universal joint 13 in Embodiment 1 of the present invention in FIG. 2, Embodiment 4 of the present invention in FIG.
By using a universal joint as shown in
The same effect as the third universal joint 13 shown in the figure can be expected.

In this case, the hanging rope 17 is attached to a hanging piece 29 at the top of a hanging spool 28 that is rotatably supported on the upper part of the lower fork 15, and is lifted by a lifting device from a support vessel at sea. .

Since the flexible riser device with this structure has a vertical riser 5 and a horizontal riser 6, the vertical movement of the platform 4 is mainly affected by the inclination of the horizontal riser 6, and the horizontal movement except for that caused by tidal currents is This can be followed mainly by the inclination of the vertical riser 5.

Also, regarding the inclination of the platform 4, mainly the first
Due to the inclination of the universal joint 9 and the vertical riser 5, the plano 1~
The rotation of the platform 4 around the vertical axis can be mainly followed by the vertical bearing 8 at the bottom of the platform 4.

The features of the flexible riser device of the present invention are as follows:
When no external force is applied, except for the third universal joint 13,
The inclination of the first and second universal joints 9, 10 is, in principle, O.

This is effective in reducing the maximum value of the inclination angle of each universal joint 9, 10, making interference less likely to occur, and facilitating the design of each universal joint 9, 10.

In the flexible riser device with this structure, the platform 4
Since the horizontal positions of the riser base 2 and the riser base 2 are deviated, the connection device 1 connected to the top 7A of the upright portion 7 of the riser base 2
4 will be removed from directly below the platform 4, and by lifting and operating the vicinity of the third universal joint 13 from a support vessel on the ocean, the connecting device 14 will be removed from the top 7A of the upright portion 7 of the riser base 2. The connection to the connection device 14 can be accessed and connected.

For this purpose, a hanging fitting 16 is provided above the extension line of the vertical axis 12 of the third universal joint 13 or on the upper surface of the end of the horizontal riser 6 connected to the third universal joint 13, and a hanging cable 17 is attached thereto. It is installed and operated from a support vessel, etc. at sea.

The suspension rope 17 can be attached at all times by connecting the upper end to the buoy 19, but it can be cut remotely using an ultrasonic cutting device and recovered at sea, and when necessary, it can be re-routed using a recall buoy, a dipper, a submersible, etc. It can also be installed.

In addition, since the connecting device 14 approaches the top 7A of the upright portion 7 of the riser base 2 from the vertical direction, the portion of the third universal joint 13 below the lower fork 15, including the connecting device 14, is connected to the connecting device even before connection. The mounting position and angle are determined by considering the weight distribution so that the 14 vertical shafts hang vertically.

Therefore, if the lower fork 15 is on one side as shown in Fig. 3, unless the counterweight 26 is attached to the opposite side, the portion including the connecting device 14 below the third universal joint 13 will be exposed to the tidal current before connection. It tilts under the force, making it difficult to connect.

Furthermore, since the upstream end of the horizontal riser 6 becomes free with respect to the tidal current, it becomes unstable and a force acts to change the direction of the horizontal riser 6.

However, as the water depth increases, the current becomes weaker, so the force acting on the horizontal riser 6 and the connection device 14 becomes smaller.
Since the connecting device 14 is sufficiently heavy, it can be attached to the hanging rope 17.
When suspended from the ocean, the third universal joint 1
If the slope is less than 3, the connecting device 14 will connect, so it will fall within the tolerance angle, and the orientation of the horizontal riser 6 can also be prevented from changing.

Even if the vertical axis 12 or the horizontal axis 11 of the third universal joint 13 is tilted, the connection device 14 will no longer be able to maintain its verticality. It is installed on the extension of the vertical shaft 12 of the universal joint 13.

In order to prevent the horizontal riser 6 from rotating around its longitudinal centerline, if necessary, attach a weight 22 to the upper surface side of the buoyancy body 21° at an appropriate location in the length direction of the horizontal riser 6, or It is also possible to have a structure that incorporates such a function.

first and second universal joints 9 at the upper and lower ends of the vertical riser 5;
10 is a universal joint having two orthogonal horizontal axes.

Therefore, the end of the horizontal riser 6 on the side connected to the vertical riser 5 may be bent upward to facilitate connection to the second universal joint 10.

If the flexible riser device of the present invention as described above is adopted,
The movement of the floating platform 4 can be absorbed within a length range in which the vertical riser 5 and the horizontal riser 6 do not become excessively large.

In addition, in order to completely recover this flexible riser device at sea, an upper connecting device 20 is provided at the bottom of the platform 4, and after being cut off from the upright portion 7 of the riser base 2, the upper connecting device 20 is attached to the bottom of the platform 4. Cut it up and collect it.

Many methods can be considered for the structure of the upper connection device 20, the method of accessing it, or the method of cutting it off and recovering it at sea, but in any case, the water depth is small, a dipper etc. can be used, and a platform Since it is also possible to operate from 4, there are no particular difficulties, so we will not discuss the details here.

Therefore, if the flexible riser device of the present invention is applied, the vertical riser movement of the platform will be mainly affected by the inclination of the horizontal riser, and the horizontal movement other than that caused by tidal current will be mainly affected by the inclination of the vertical riser. Furthermore, the tilt of the platform can be followed mainly by the tilt of the first universal joint and the vertical riser, and the rotation of the Plan I form about the vertical axis can be followed mainly by the tilt of the platform. It has the advantage of being able to follow each other with the vertical bearings at the bottom, and also being able to follow changes in tidal currents and the like in all directions.

Furthermore, the present invention has the effect that the maximum value of the inclination angle of each universal joint can be made small, making interference less likely to occur and making the design of each universal joint easier.

Additionally, the present invention has the advantage that the platform does not overlap the riser base, making it easier for the connection device to access and connect to the top of the riser base upright.

[Brief explanation of the drawing]

FIG. 1 is an overall side view of a flexible riser device according to Embodiment 1 of the present invention, FIG. 2 is an enlarged perspective view of the main part of the third universal joint in FIG. 1, and FIG. 3 is an embodiment of the present invention. A side view of the main part of the third universal joint of the flexible riser device in Example 2, the fourth
The figure is a side view of a main part of a third universal joint consisting of a horizontal bearing and a vertical bearing of a flexible riser device according to Embodiment 3 of the present invention, and FIG. FIG. 7 is an enlarged perspective view of the main parts of the third universal joint. 1...Undersea, 2...Riser Base, 3
...Sea surface, 4...Platform,
5... Vertical riser, 6... Horizontal riser, 7... Upright part, 8... Vertical bearing, 9
...First universal joint, 10...Second universal joint, 11...Horizontal axis, 12...
Vertical axis, 13...Third universal joint, 14...
...Connection device, 16...Hanging fitting, ]7...
... Suspension rope, 18... Underwater buoy, 19...
... Buoy, 21 ... Buoyant body, 22 ...
... Weight, 28 ... Hanging spool, 29 ...
...A hanging piece.

Claims (1)

[Scope of Claims] 1. A flexible riser that connects a riser base on the seabed and a floating platform on the sea, comprising a vertical riser, a horizontal riser, and an upright part provided on the riser base, and a flexible riser that connects a riser base on the seabed and a floating platform on the sea. The vertical riser is suspended via a vertical bearing and a first universal joint, the vertical riser and the horizontal riser are suspended via a second universal joint, and
The horizontal riser and the upright portion include a third universal joint having two axes, a horizontal axis and a vertical axis, perpendicular to the longitudinal direction of the horizontal riser, and a connecting device that hangs vertically from the third universal joint in a separated state. The connecting device can be connected via a lifting device that has a weight distribution that prevents any part from floating when the connecting device is disconnected underwater, and that can lift the vicinity of the third universal joint from the sea side. A flexible riser device that can be accessed and connected to the upright section. 2. The flexible riser device according to claim 1, which has a horizontal riser formed in a weight distribution such that its upper surface side always faces the upper side and its lower surface side always faces the lower side. 3. The flexible riser device according to claim 1 or 2, which has a horizontal riser with an upwardly bent end suspended from the vertical riser. 4 In addition to the vertical riser, the horizontal riser, and the vertical riser, and the vertical riser, and the vertical riser, and the vertical riser, the flexible riser, and the vertical bearing, the first universal joint, the second universal joint, and the third
A patent that flexibly connects the pipes and wires in each rotating part of the universal joint, and further connects the pipes and wires with a pipe joint and a wire joint at the connection between the connecting device and the upright part. A flexible riser device according to claim 1, 2 or 3.