JPS6027798B2 - Retention device and method for offshore floating container and submarine well - Google Patents

Description

[Detailed description of the invention] The present invention relates to marine floating structures.

More particularly, the present invention relates to floating structures for drilling wells and/or producing oil and gas, and/or similar operations.
From a more specific point of view, the present invention relates to a floating structure having a floating device for floating itself.
The structure is moored by a plurality of essentially parallel and perpendicular pipes, commonly referred to as "riser pipes." More particularly, the present invention relates to such a structure, in which the homogeneous casing of the riser pipe forms an essential part of the mooring device. In recent years, it has become desirable to use floating vessels for drilling wells on the seabed. Many of these structures are held in place by conventional extensive catenary mooring lines or propulsion thruster systems. One device is a vertically moored platform, such as that described in U.S. Pat. An important feature of this vertically moored platform is that the floating platform is connected to the seabed mooring device only by elongated parallel members, preferably large diameter pipes and generally It is called "riser pipe". These elongated members or riser pipes are held under tension by the excess buoyancy of the platform. The present invention is disclosed in the above-mentioned U.S. Pat.
This is an improvement on the mooring device described in No. 648,638.

Although said patent is considered the most recent prior art, as stated above, the present invention is an improvement thereon. Other patents dealing with vertically moored platforms include:
US Patent No. 3559410, US Patent No. 3559411, US Patent No. 3572272, US Patent No. 3976021, US Patent No. 39788
04, same No. 3 macular spot 28, same No. 3993273, same No. 40
There are No. 62313 and No. 3154039. There are prior patents and prior art that teach having a homogeneous casing extending from an underwater wellbore to an above-water platform. In this regard, U.S. Patent No. 39715
76 should be noted. Although U.S. Pat. No. 3,705,623 shows D-pipes 33, 17 connected to floating member 19, these D-pipes do not constitute any part of the mooring system. None of these patents or techniques attempt to moor a vertically moored platform with a concentric tensioned casing within an external tensioned riser pipe. There is no known prior art that does this.
The present invention relates to a mooring device and method for connecting an offshore floating vessel and a submarine well, wherein the wellbore includes a first casing fixed in a hole in the seabed, a first casing supported within the first casing, and a first casing supported within the first casing; and a second casing extending deeper than the first casing and fixed within the hole.

A first riser pipe (commonly referred to as a "riser pipe") is sealingly connected to the first casing at its lower end, such that the first riser pipe and the first casing are Forms a pipe without fluid leaks. The upper end of the first riser pipe is supported from the container for tensioning it. A lower end of a second riser pipe or a second rising casing is sealingly connected to said second casing, so that said second
The casing and the second riser pipe form a second fluid-tight pipe. The upper end of the second riser pipe is supported from the upper part of the first riser pipe,
Therefore, when tension is applied to the first riser pipe, tension is also applied to the second riser pipe. The upper and lower ends of the first riser pipe are provided with a stiffener, which is actually a hardened section to distribute the curvature over the entire length or part of the riser pipe. .

For the second riser pipe or inner riser pipe,
A centering device is provided within the terminator of the outer riser pipe or first riser pipe. No terminators are required at the top and bottom ends of the inner casing. A better understanding of the various objects and aspects of the present invention will be gained from reading the following description in conjunction with the accompanying drawings.

Referring first to FIG. 1, a side view of a vertically moored platform is shown.

The figure shows a platform 10 supported on water 12 having a bottom 14 . The structure 10 generally includes a flotation device 16 that supports a work deck 18 above the surface 20 of the water 12. A vertically moored platform is disclosed in the aforementioned U.S. Pat. No. 3,648,638.
is described in detail. For example, the flotation device 16 consists of four bottle-shaped flotation legs 22. Each leg 22 has a plurality of riser pipes 2 to which a baser 26 is attached.
It is moored by 4. The riser pipe 24 is connected to a cemented casing 28 in a hole in the bottom of the water. A template 30 is shown on the bottom 14 through which the wellbore for the casing 28 is guided. The riser pipe 24 is usually made of high quality steel and is typically The riser pipes 24 are parallel and are supported in tension by a vertical force on the flotation device.
The typical length of the vertically moored platform from the bottom of the leg member 22 to the sea bed 14 is 500 feet (
153 m) to several thousand feet (192 m).
Referring now to FIG. 2, an improved mooring coupling arrangement between a vertically moored platform and the seabed is shown.

Above the coupling device is shown a leg 22 which is one of the four flotation devices of the vertical mooring platform shown in FIG. For simplicity and ease of understanding, only one of the riser pipes extending between the leg 22 and the seabed 14 is shown.
The lower part or enlarged portion of the leg 22 is connected to a vertical pipe 32.
is penetrated. A riser pipe upper terminator 34 is provided at the upper end of the riser pipe 24.
To put it simply, it is known that if a tubular member is held under tension and subjected to bending forces, stress will be concentrated at the ends.One way to address this problem is to , the end portion may be made sufficiently strong so that the bending deformation concentrated in this portion is distributed over a longer length. This is what is being done here.
The reinforced part of the terminator is referred to here as the riser pipe upper terminator 34. Accordingly, terminators here refer to stiffened portions of the riser pipe for distributing the curvature over selected portions of the riser pipe. Between the wall of the upper horizontal bearing 36 and the lower horizontal bearing 38
and is provided.

Above the horizontal bearing 36 is a vertical bearing 40.
is provided. Details of this vertical bearing 40 are shown in FIGS. 17 and 18 of US Pat. No. 3,976,021. It mainly consists of the jack 42, the bracket turtle 4, the engagement shoulder 46 of the riser pipe upper terminator 34, and the shim and bearing 48. The vertical force of tension in the riser pipe 24 is transmitted to the vertically moored platform leg 22 via the vertical bearing 40. The lower end of the riser pipe 24 is connected to a lower terminator 501 that passes through the drive pipe 52 in the template 30.

From the drive pipe 52, the Mazda Line suspension 5
6 hangs a 20 inch (50.8 skin) diameter pipe casing 54, said suspension actually being connected to an upwardly facing shoulder 58 on drive tube 52 and said 20 inch diameter pipe casing 54.
It consists of a downward facing shoulder 60 attached to the outer wall of a pipe casing 54 having a diameter of 50.8 inches.

If the seabed 14 is sufficiently soft, the drive tube 52 can be dug to the required depth within the seabed 14.
Alternatively, a hole can be drilled through the guide tube. A hole can be drilled through the drive pipe 52 and a 20 inch diameter pipe casing 54 can be installed and cemented in place using a conventional subsea drilling rig. Once the 20 inch (50.8) diameter casing is cemented in place, a 4-inch hole is then drilled through its bottom through which a smaller sized casing can be passed. The casing is a 13 inch diameter casing, shown as casing 62, which is supported by a mudline suspension 64 similar to the mudline suspension 56 described above. The second casing or 13 inch 5/8 diameter casing 62 is then lowered and cemented in place. Then 13 inches 5'8 (34.6 arc)
The riser pipe casing 78 is lowered and connected to the casing 62. Thereafter, a hole is drilled for passing the casing of smaller size, for example 9 inches 5'8 (24.4 mm) in diameter. The innermost casing 66 is then also cemented in place and supported by a mudline suspension 68. Such casing may be suspended in the drilled hole in the known manner described above. Any desired number of said casings 54, 6 can be installed in a given location.
The upper ends of 2,66 are provided with locking devices such as J-shaped slots 70,72,74. The lower end of the riser pipe 24 is connected to the pipe casing 5 by a J-shaped lug 76 mounted in the J-shaped slot 70.
It is connected to the upper end of 4.

A sealing device is also provided, so that a fluid-tight pipe is formed upwardly from the pipe or outer casing 54 to the floating structure exemplified by the legs 22. Although not shown, a latching device may be installed between the casing 54 and the drive tube 52 to restrain vertical movement between the casing 54 and the drive tube 52. Similar arrangements can be installed for subsequent pairs of casings, such as casings 62, 66. Inside the riser pipe 24, two identical D-shaped casings are shown, namely an intermediate casing 78 and an inner casing 80.

Of course, any suitable number of inner casings may be used. The lower end of the intermediate casing 78 is connected via a J-shaped slot 72 to the casing 62 cemented into the borehole, and similarly the lower end of the inner casing 80 is shown as the smaller casing in the drawings. It is connected to a cemented casing 66. Therefore, the casing 62 and the intermediate casing 78 form a fluid-tight pipe extending from the bottom of the casing 62 to the top of the intermediate casing 78, and similarly, from the lower end of the inner fixed casing 66 to the casing 80. A smaller, fluid-tight pipe is formed extending through the platform to the top of the platform. If desired, the intermediate casing 78 can be lowered before the hole for the inner casing 66 is drilled. FIG. 4 shows the connection mechanism between the riser pipe and the casing in the wellbore.

The figure also shows the J-shaped slot 70 above the upper end extension of the casing 54 and the J-shaped lug 76 on the lower end of the riser pipe 24. A sealing device 82 is provided between the riser pipe 24 and the upper end expanded portion of the casing 54. a connecting portion 72 between the intermediate casing 78 and the cemented casing 62;
Inner casing 80 and cemented casing 6
The connecting portion 74 with 6 may be as shown in FIG. The upper ends of the intermediate casing 78 and inner casing 80 are then supported against the upper end of the riser pipe so that these inner riser casings 78 and 80 can form part of the mooring system. Let's focus on the equipment.

This is clearly shown in FIG. A flange 81 is provided at the upper end of the riser pipe extension 24A.
A spool 84 for suspending the casing is provided at the top of the flange 81. A device is provided for connecting the intermediate casing 78 with the spool 84 on which the casing is suspended. This device consists of a sliding device 86.
A screw 88 is used to seal the annular portion between the casing 78 and the spool 84 from which it hangs. Thus, the upper end of the casing 78 is connected to the riser pipe extension 24 via a spool 84 that suspends the casing.
Supported by A. The casing suspension spool 84 has an upper flange 92 for supporting a casing suspension spool 94 such that the inner casing 80 is connected to the casing suspension spool 84,
94 and is supported by the riser pipe extension 24A. Bolt 10 that has undergone appropriate machining and has sealing properties
0, 102, 104 are provided and the annular space 1 between the riser pipe extension 24A and the rising casing 78
06 and the annular space 108 between the two inner casings 78 and 80 are made into an annular space without fluid leakage. Plugs 110 and 112 can be removed and pressure gauges installed to measure the pressure within these annular spaces. Follower type valves and other devices may be placed on the extensions 114 to drill wells through these casings. The preferred installation procedure is as follows.

First, riser pipe 24 is pretensioned to a predetermined value by jack 42, and then it is bonded into position on bearing 48. Drill a hole for the casing 62. The casing 62 is lowered and fixed with cement. The rising casing 78 is lowered and the casing 6 is lowered in the J-shaped slot 72.
2 and then a drilling rig pulling operation tensions the lift casing 78 to a predetermined value, which value is a function of the tension applied to the riser pipe 24. A locking device 86 is installed to lock the upper end of the rising casing 78 to the suburr 84 that suspends the casing. Other internal casings are installed using similar procedures. Inside the riser pipe 24 and riser pipe terminators 34, 50, a centering device 35 between the riser pipe 24 and riser pipe terminators 34, 50 and the first casing or intermediate casing 78, and a casing 78 are provided.
A centering device 37 between and 80 is provided.

By doing so, the wear caused by the relative movement between the two said casings is controlled. Also, the casing inside the riser pipe does not require a terminator. According to the device so far described, a significant portion of the mooring mechanism is located within the internal casings 78 and 8.
0.

This provides a stronger mooring for a riser pipe of a given size and will provide better protection during very severe storms. inner casing 78,
80 etc., the strength of the mooring by the external riser pipe 24 is a function of its cross-sectional area, or more precisely, its maneuverability in the respective ball directions. The degree of mooring provided by the riser casing varies from as low as about 25% of the total mooring force to about 70%.
An example where the riser casing bears 27% of the mooring force in still water is as follows.

Here lkips = 1000 pounds (454&). Riser casing provides 45% of mooring force in still water
An example where is negative is as follows. An example where the wither casing bears 60% of the mooring force in still water is as follows. An example where the rising casing bears 67% of the mooring force in still water is as follows. These distributions are determined by the axial flexibility of the rising casing and the expected temperature and pressure effects. If the temperature and pressure distribution between each casing changes, this distribution will also change. This distribution will also change as the total mooring force changes due to wind, wave, and current influences. Although the embodiments described above have been described in great detail, changes may be made without departing from the spirit and scope of the invention.

[Brief explanation of the drawing]

1 is a view of a vertically moored platform; FIG. 2 is a partial cross-sectional view of one riser pipe in one leg of the vertically moored platform shown in FIG. 1; FIG.
The figure is an enlarged cross-sectional view of the device in Figure 2 connecting the top end of the inner casing to the riser pipe, and Figure 4 is an enlarged sectional view of the device in Figure 2 connecting the riser pipe to the casing moored in the wellbore.
One device is shown. In the figure, 24...first riser pipe, 54...first casing, 62...second casing, 66...third casing, 78...second riser pipe, 80...third riser pipe. FIG. 3 FIG. 4 FIG. l FIG. 2

Claims (1)

[Scope of Claims] 1. A method for mooring an offshore floating vessel and a submarine well, wherein the submarine well has a first casing fixed in a hole in the seabed, and a mooring method within the first casing. and a second casing extending deeper than the first casing and fixed in the hole, the first riser pipe being connected to the first casing at its lower end. connecting the first riser pipe and the first casing in a sealing manner to form a fluid-tight pipe;
supporting an upper end of the first riser pipe from the container to apply tension to the pipe; and coupling a lower end of the second riser pipe in a sealing relationship to the second casing to connect the second riser pipe to the second riser pipe. The casing and the second riser pipe are connected to form a second fluid-tight pipe, and the upper end of the second riser pipe is supported from the container so that the second riser pipe is connected to the second riser pipe. A method for mooring a marine vessel and a submarine well, the method comprising: applying tension from the buoyancy of the vessel. 2. In the method for mooring a marine container and a submarine well according to claim 1, at a position above a height above the first riser pipe supporting the first riser pipe from the container, A method for mooring a marine vessel and a submarine well, comprising supporting the second riser pipe from an upper end of the first riser pipe. 3. In the method for mooring a marine vessel and a submarine well according to claim 1, the axial tension applied to all the tensioned pipes in the first riser pipe is from about 25% to about 70% of the total axial tension exerted by the pipe and all tensioned pipes in the first riser pipe.
Mooring method between offshore vessels and submarine wells within the range of %. 4. In a device for mooring a marine floating container to a plurality of concentric casings moored to the seabed, a tensioned first riser pipe and an upper end portion of the first riser pipe are connected to the container. a vertical support bearing for coupling, a horizontal bearing for transmitting horizontal forces between the upper end portion of the first riser pipe and the container; and a horizontal bearing for transmitting a horizontal force between the upper end portion of the first riser pipe and the container; 1. A method for mooring an offshore floating vessel and a submarine well, comprising: a riser casing under tension; and a support device for supporting the riser casing from the vessel. 5. A mooring device for a marine floating container and a submarine well according to claim 4, wherein the upper end portion of the riser pipe passing through the horizontal bearing is a terminator. . 6. The mooring device for a marine floating vessel and a submarine well according to claim 4, which includes a centering device on the riser casing in the terminator, and the wall of the riser casing is configured to extend over its entire length. A mooring device between a floating vessel on the sea and a submarine well, which has a nearly uniform thickness. 7 In a device for mooring a marine floating container to a plurality of concentric casings moored to the seabed, a tensioned first riser pipe and an upper end portion of the first riser pipe are connected to the container. a vertical support bearing for coupling, a horizontal bearing for transmitting horizontal forces between the upper end portion of the first riser pipe and the container; and a horizontal bearing for transmitting a horizontal force between the upper end portion of the first riser pipe and the container; an offshore floating vessel and a subsea wellbore mooring system comprising: a riser casing tensioned at the bottom; and a support arrangement for supporting the riser casing from the first riser pipe at a position above the vertical support bearing. . 8. A method for mooring a floating vessel on the sea and a submarine well, in which the submarine well has a first casing fixed in a hole in the seabed, and a first casing supported within the first casing; a second casing supported within the second casing, extending deeper than the second casing and fixed within the hole; In the mooring method, a first riser pipe is connected in a sealing relationship to the first casing at a lower end thereof, and the first riser pipe and the first casing are connected to each other in a sealing relationship. connecting the first riser pipe to form a fluid-tight pipe; supporting the upper end of the first riser pipe from the container to apply tension to the pipe; and connecting the lower end of the second riser pipe to the second riser pipe. applying tension to the second riser pipe from a tensioning device supported by the vessel and connected to an upper end of the second casing; fixing the upper end of the second riser pipe under tension with respect to the upper part of the third riser pipe; removing the second riser pipe from the tensioning device; applying tension to the third riser pipe from a tensioning device supported by the container and connected to an upper end of the third casing;
The method includes fixing the upper end of the third riser pipe under tension to the upper part of the first riser pipe, and removing the third riser pipe from the tensioning device. A method of mooring a floating vessel on the sea and a submarine well.