WO2010012895A1

WO2010012895A1 - Method of installing a tubular pipe on the sea bed

Info

Publication number: WO2010012895A1
Application number: PCT/FR2009/000929
Authority: WO
Inventors: Jeroen Hugo Remery; René Antoine MALOBERTI; Roberto Jourdan De Aquino
Original assignee: Technip France
Priority date: 2008-07-29
Filing date: 2009-07-27
Publication date: 2010-02-04
Also published as: FR2934663A1; FR2934663B1

Abstract

The invention relates to a method and to an assembly for installing a subsea pipe (16) on a sea bed (15). According to the method, there are provided: a surface installation (12, 14); a tubular pipe (16; 44) having two opposite ends (24, 32; 56, 58); and retaining means (20) for retaining the said tubular pipe (16; 44). Next, the said tubular pipe (16; 44) is immersed from one of its ends (24; 56) up to the other of its ends (32) while at the same time retaining it. According to the invention, support means (26, 30, 31; 52, 53, 54) are also provided for securing the said one of the said ends (24; 56) while the said tubular pipe hangs in a U between the said support means (26, 30, 31; 52, 53, 54) and the said retaining means (20); and the said ends (24, 32; 56, 58) are guided towards the said sea bed (15).

Description

Method of installing a tubular pipe on the seabed

The present invention relates to a method of installing an underwater tubular pipe on a deep seabed for the transport of hydrocarbons.

In the field of offshore oil exploitation, flexible pipes and rigid pipes are installed according to the applications and constraints encountered. Refer to the API 17B and 17J specifications of the American Petroleum Institute for the definition of flexible pipes and the API 17A specification for the definition of rigid pipes.

It is recalled that the flexible pipes have a minimum bending radius without damage (often called a "minimum bending radius"), for example a few meters, in comparison with rigid pipes whose minimum radius of curvature without plastic deformation is relatively large, for example several tens of meters.

In addition, for a flexible pipe the MBR corresponds to a limit before irreversible damage whereas in the case of a rigid pipe, the minimum bending radius corresponds to the appearance of a plastic deformation which is reversible by straightening. The flexible pipes are previously wound on reels, which are installed on a laying ship. Once the laying ship arrived on the installation area, on the high seas, the flexible pipe is dropped by gradually unrolling the drum and it leaves the ship through a gutter (in English "stinger"). During the unwinding, the support means of the drum and the gutter are means for retaining the submerged pipe and they support at least the weight of the pipe portion which extends between the bottom and the surface of the marine environment. Alternatively, the flexible pipe is unwound by means of a laying tower provided with tracks in which case, the crawler conveyors of the tower, consituent the essential means of retaining the flexible pipe. Laying systems for rigid pipes are described in the API 17 A specification and two types of laying are distinguished, depending on whether the pipe sections are welded at sea ("stove piping") or welded on the ground ("reeled pipe"). ). According to the first type of laying in deep sea preferentially used the so-called "J" pose. According to this laying technique, pipe sections are assembled on the laying boat to form portions of pipe, which are successively installed on a tilting laying tower of the laying ship. The laying tower provided with a pipe portion is inclined in the vicinity of the vertical, and is welded to the previous portion which has been immersed and one end of which is retained emerging through retaining means on the laying boat. The pipe portions are thus welded successively to each other and immersed to gradually form the immersed rigid tubular pipe. Reference is made to US 5,464,307 to illustrate this laying technique.

A second type of laying rigid pipes, welded sections on the ground, called the "rigid unrolled" (known as "reeled pipe system"), is known for example from GB 2 025 566 A, where the pipe, which was welded into long lengths at the wharf, is then wound with plastic deformation around a coil of horizontal axis, which can reach 15 to 20 meters in diameter and which is located on the ship docked at the wharf. After the laying ship has rejoined the laying area, the pipe is unwound from the reel with plastic deformation and passes into a rectifier-trancancer before being taken up by the crawler conveyors of a tilting laying ramp provided in a driving immersion zone at the rear of the ship and whose inclination is chosen according to the depth of laying. The rectifier-trancaneur and the crawler conveyors, integral with the laying ship, constitute means for retaining the submerged pipe. Whatever the types of pipe and laying techniques to install rigid pipes on the seabed, hydrocarbons are extracted from deep seabed deeper, so that the portion of pipe that extends between the bottom and the surface and which is suspended from the holding means of the laying ship is relatively important. However, the larger this portion is important and the retaining means of the pipes adapted to retain the pipe during immersion must be resistant. In addition, the laying vessels originally planned for seabed of modest depth, are equipped with retaining means in relation to the length of the pipes installed so far.

Also, a problem that arises and that aims to solve the present invention is then to provide a method for installing a subsea tubular pipe in deep water, which allows to install tubular pipes on seabed large. depth, through usual surface installations, without risking damage to the holding means of the laying vessels.

In order to solve this problem, the present invention proposes a method of installing an underwater tubular pipe on a deep seabed for the transport of hydrocarbons, said method being of the type according to which: surface installation capable of floating on the surface of the water of a marine environment and a tubular pipe intended to be extended longitudinally between two opposite ends; providing restraint means on said surface installation for retaining said tubular duct; and progressively immersing said underwater tubular conduit in said marine environment from one end to the other end thereof by retaining it with said retaining means during immersion; then said tubular pipe is guided to said seabed to rest against said seabed; according to the invention, there is further provided support means bearing on said surface installation; one hangs said one of said an end to said support means for retaining said one of said ends during immersion of said tubular conduit, while said tubular conduit extends U-shaped between said support means and said retaining means; and, said ends are progressively guided towards said seabed to support said tubular pipe on said seabed.

Thus, a characteristic of the invention resides in the implementation of support means to which the tubular pipe is hooked during its immersion, which makes it possible to suspend it between the retaining means and the support means, and thus to divide substantially by two the weight supported by the retaining means during the immersion. Indeed, according to the prior art, the pipe is unwound from the surface installation and it extends between the seabed on which it bears and the retaining means located on the surface installation. Thus, the retaining means supports the weight of the pipe portion that extends between the bottom and the surface. When the depth is modest, this weight is bearable for the retaining means, but when it reaches 3000 meters for example, the traditional retaining means are no longer sufficiently resistant. However, these retaining means equip the current installation facilities, and it is expensive to change. Thus, thanks to the object of the present invention, current installations are used by adding support means for installing the tubular pipes at great depth, which is less expensive.

Advantageously, said one of said ends is hooked to said support means with a traction cable, which may be installed on a winch to drive said one of said ends towards the surface or conversely, to guide it towards the bottom for deposit the tubular pipe.

According to a particular embodiment of the invention, a pre-wound tubular duct is provided, for example on a reel or a reel, and this duct is installed on the surface installation and then unrolled and installed. on the seabed, as will be explained below in more detail. Preferably, immersion means are provided comprising unwinding means of said pre-wound tubular conduit, which include means for driving in rotation the aforementioned coil or drum as well as crawler elements which make it possible to drive and guide the driving in translation while retaining it.

According to a first variant embodiment, a pre-rolled flexible tubular pipe is provided, which can be wound with a small radius of curvature and consequently on coils of small diameter, which is less cumbersome on the surface installation. In addition, said installation comprises a laying boat and installing said retaining means and said support means on said laying boat, precisely when the expanded pipe is a flexible pipe. Indeed, since it has a possibility of large curvature, with a small radius of curvature, it is quite possible to provide the retaining means and the support means on the same building, and on which they are spaced apart. distance of about 100 meters. Preferably, this variant embodiment will be implemented for the laying of flexible pipe of short length corresponding for example to 1 or 1.5 times the depth of the seabed.

According to a second alternative embodiment of the invention, a pre-wound rigid tubular pipe is provided on large drums where the pipe is plastically deformed and the radius of curvature of the pipe is greater than that of the pipe. flexible. Such rigid pipe requires special recovery and training means that will be detailed in the following description. According to this second variant, implementation of rigid pipe, and according to a particular embodiment, said sections are assembled on said surface installation to form said rigid tubular pipe. This embodiment makes it possible to form the rigid tubular pipe in situ, and to adjust its length as a function of the bottom installation and the circumstances. In addition, and particularly for the installation of rigid pipes but not exclusively, there is provided a surface installation comprising a laying ship and a support vessel, and installing said retaining means on said laying ship and said support means on said support ship. In this way, after having been straightened in the case of pre-rolled rigid pipes, or formed for pipes assembled in situ, they are immersed progressively and they are held at their end by the support means located on the support vessel. The latter can then be carried away from the laying ship, for example 300 meters, which makes it possible to respect the limit of elastic and plastic deformation of the rigid pipe during immersion.

In another aspect, the present invention relates to an installation assembly of a subsea tubular pipe on a deep seabed for the transport of hydrocarbons, said assembly comprising: a surface installation capable of floating on the surface water from a marine environment; a tubular pipe intended to be extended longitudinally between two opposite ends; retaining means installed on said surface installation for retaining said tubular duct; means for progressively immersing said underwater tubular pipe in said marine environment, from one of its ends to the other of its ends by retaining it with said retaining means during immersion; and, means for guiding said tubular pipe towards said seabed and pressing it on said seabed; according to the invention, the assembly further comprises support means bearing on said surface installation for hooking said one of said end to said support means so as to hold said one of said ends during the immersion of said tubular conduit, while said tubular duct extends forming a U between said support means and said retaining means; and these ends are progressively guided to said seabed to support said tubular pipe on said seabed.

Other features and advantages of the invention will emerge on reading the following description of a particular embodiment of the invention, given by way of indication but not limitation, with reference to the accompanying drawings in which:

- Figure 1 is a schematic view illustrating the method of laying an installation according to the invention according to a preliminary phase and according to an alternative embodiment; - Figure 2 is a schematic view illustrating the laying method at the end of the preliminary phase;

- Figure 3 a schematic view illustrating the method of laying according to an immersion phase;

- Figure 4 a schematic view illustrating the method of laying according to a support phase on a seabed;

- Figure 5 is a schematic view illustrating the method of installation of an installation according to the invention according to another embodiment and in a preliminary phase; and,

- Figure 6 a schematic view illustrating the method of installation according to said other variant and according to an immersion phase.

FIG. 1 illustrates according to a first variant embodiment of the invention, a surface installation 10 comprising a laying ship 12 and a support ship 14, the two floating elements spaced from one another, at the surface 11 of a marine environment 13 and overhanging a seabed 15. The laying ship 12 is provided with a tubular pipe 16 pre-wound on a drum 18 adapted for this purpose. The tubular pipe 16 may be a flexible pipe or a rigid pipe. If it is a flexible pipe, it is wound on the drum 18 with a relatively small radius of curvature and requires no straightening during unwinding. When rigid, the tubular pipe 16 is wound with a larger radius of curvature and is adapted to be unwound from the drum 18 and then plastically deformed by passing through a straightener-rectifier not shown here, before being taken up by crawler conveyors 20 of a laying ramp inclined. The latter is provided in line with an immersion well 22 formed vertically through the laying vessel 12. In the case of a rigid pipe, the straightener and the crawler conveyors 20 together form, means retaining the rigid tubular pipe 16 unwinding when it hangs under the effect of its own weight, immersed in the marine environment 13 through the immersion pit 22. In the case of a flexible pipe, in the absence of a rectifier-trancancer, only the crawler conveyors 20 constitute the essential means of restraint. In addition, the laying ship 12 is equipped with a first winch 23 adapted to receive a coiled cable and whose function will be explained below. The tubular pipe 16 is a long pipe, here a length of 3750 meters, for example, and it is intended to be extended on the seabed 15 located at 3600 meters for example also. Thus, the weight of the submerged pipe is greater than 120 tons and the retaining means, the crawler conveyors and / or the straightener-rectifier, can not bear this weight alone without risk of deterioration. Therefore, the support vessel 14 is implemented during installation to take back part of this weight and then relieve the retaining means of the laying ship 12 during the unwinding of the tubular pipe 16.

Thus, the tubular pipe 16 has a first end 24 which, according to a preliminary step of the method of implementation of the installation method according to the invention, is first immersed under the laying vessel 12 by unwinding a length tubular pipe data 16. In addition, according to this preliminary step, this first end 24 of tubular conduit 16 is connected to support means and more specifically, to a jib crane 26, located on the support vessel 14, by means of a sling or a first cable 28. In addition, the support vessel 14 is equipped with a second winch 30 and guide means gutter 31, located under the bracket 26 and for unwinding the first cable 28 or on the contrary to wind to pull on the first end 24 of the tubular conduit 16.

Thus, reference will now be made to FIG. 2, illustrating all the elements shown in FIG. 1 and in which, precisely, the second winch 30 has been rotated to wind up the first cable 28 and thus to drive the first end 24 of tubular conduit 16 to the second support vessel 14, while in parallel the tubular conduit 16 has been unwound from the first laying vessel 12. In this way, the tubular pipe 16 sketches a U-shape. a rigid tubular pipe, the tubular pipe bends to its elastic limit. Thus, it is able to find a longitudinal shape then in a rest position as will be explained below. To do this, the laying ship 12 and the second support vessel 14 must be sufficiently distant from each other, for example from a distance of between 50 and 500 meters and more precisely between 70 and 300 meters. In addition, the total weight of the tubular pipe portion 16 immersed and forming a U is substantially evenly distributed on the two vessels 12, 14 and more particularly on the retaining means of the laying ship 12 and on the stem, in this step preliminary implementation of the method of laying.

Then, according to an immersion step, the entire tubular pipe 16 is unwound and immersed to its second end 32, which appears in Figure 3 held under the laying vessel 12, by a second cable 34 through the well 22 and wound on the first winch 13. In this way, during the immersion of the tubular pipe 16, which is then retained by the crawler conveyors 20 especially to its second end 32, its total weight then divides substantially in two, between the first laying ship 12 and the support ship 14, which relieves the crawler conveyor 20 in particular, which in this case should have borne the total weight of the tubular pipe 16 by absence of support vessel. Then, the second cable 34 is retained by means, and in particular the first winch 13, able to take up the half-weight of the tubular pipe 16.

In addition, the first cable 28 is directly connected to the second winch 30 and has been slightly unwound in order to completely immerse the first end 24 of the tubular conduit 16. In this way, the latter forms a U fully immersed in the marine environment 13 and is suspended by its two ends 24, 32 respectively to the laying ship 12 and the support vessel 14. The tubular pipe 16 thus immersed U has a middle portion 36 forming the bottom of the U.

In a bearing step, the two ends 24, 32 of the tubular conduit 16, located substantially at the same level, will then be lowered to the seabed 15 simultaneously so as to support first, the middle portion 36 on the bottom 15 as shown in Figure 4. This figure shows all the elements described in the previous figures. In this way by continuing the descent of the two ends 24, 32, releasing respectively and simultaneously the first and second cables 28, 34, the tubular conduit 16 is supported on the seabed 15 and then extends substantially longitudinally in a rest position. Then, the connections of the two ends 24, 32 are made using submarine robots, with bottom facilities. Thus, such installed pipe allows to convey a hydrocarbon on the seabed, from one installation to another.

According to another embodiment of the invention, not shown, which is specifically adapted to rigid pipes, the pipe is installed by assembling rigid pipe sections directly on the pipe. laying boat for constituting portions of pipe, which are successively installed on a tilting laying tower of the laying ship. This laying tower is adapted to be adjusted vertically in line with a laying shaft formed through the laying boat to allow the passage of the pipe. The laying tower with a pipe portion is inclined in the vicinity of the vertical, and is welded to the previous portion which has been immersed and one end of which is retained emerging through clamping jaws on the laying boat. The pipe portions are then welded successively to each other and immersed to gradually form the immersed rigid tubular pipe. In this way, unlike the previous technique, the tubular pipe 16 is immersed sequentially at the rate of completion of the pipe portions. However, the installation method is identical and a support vessel allows to take back part of the weight of the rigid tubular pipe, while the two ends are lowered simultaneously to support the rigid tubular pipe on the seabed.

According to a second variant embodiment of the invention, it is conceivable to install support means on the laying boat and to overcome the need for a second support boat. This variant embodiment is suitable only for the laying of flexible pipes which can be deformed during the laying, with a minimum radius of curvature, without damage, much less than the radius of curvature of the rigid pipes. Preferably, this method will advantageously be adapted for the short lengths of flexible pipe. Referring to Figure 5 which shows a mixed laying boat 40 equipped with a coil 42 on which is wound a flexible pipe 44 of great length, for example 3760 meters. This flexible pipe 44 is driven in translation through a laying shaft 46 via a track train 48. In addition, the mixed laying boat 40 is equipped at one of its ends 50 with a third winch 52 and second guide means 53. A third cable 54 is wound around the third winch 52 and extends into the second guide means 53 to join under the boat a first end 56 of flexible pipe 44. This first end 56, has been immersed through the laying shaft 46 and is suspended from the laying boat 40.

In this way, as the flexible pipe 44 is unwound through the laying shaft 46, its weight divides substantially in two and is distributed between, on the one hand, the support means constituted by the third winch 52 and the second guide means 53 and secondly, the track train 48 which retains the flexible pipe 44 during its immersion. The track train 48 also makes it possible to control the speed of immersion of the flexible pipe 44.

Then, and in the same way as for the aforementioned rigid pipe, the entire flexible pipe 44 is unwound to a second end 58 of flexible pipe 44. Reference is made to FIG. 6 where the second pipe end 58 appears. flexible 44, held under the laying boat 40, by a fourth cable 60 passing through the laying well and wound on a fourth winch 62, similar to the second winch 13 of the laying ship 12 mentioned above.

Thus, the fourth cable 60 is retained by the fourth winch 62, able to take up part of the weight of the flexible pipe 44; the other part is taken up by the third cable 54 which is retained by the third winch 52 and the guide means 53.

Thus, similarly to the first embodiment of the invention, the flexible pipe 44 forms a U immersed in the marine environment 13 and is suspended by its two ends 56, 58. It has a middle portion

64 flexible pipe 44, which is supported on the seabed by unwinding the third and fourth cables 54, 60, to descend gradually.

Claims

1. Method of installing an underwater flexible tubular pipe (16; 44) on a deep seabed (15) for the transport of hydrocarbons, said method being of the type according to which:

providing a surface installation (12, 14; 40) able to float on the surface of the water of a marine environment (13);

a flexible tubular conduit (16; 44) is provided to be extended longitudinally between two opposite ends (24, 32; 56, 58); - retaining means (20; 48) are provided on said surface installation to retain said flexible tubular conduit (16; 44);

progressively immersing said flexible tubular duct (16; 44) in said marine medium, from one of its ends (24; 56) to the other of its ends (32; 58) by retaining it with said means restraint during immersion;

said flexible tubular duct (16; 44) is guided towards said seabed (15) in order to bear against said seabed; characterized in that it further comprises the following steps:

- Supporting means (26, 30, 31; 52, 53, 54) are further provided in abutment on said surface installation (12, 14; 40);

said one end (24; 56) is hooked to said support means (26, 30, 31; 52, 53, 54) to retain said one of said ends during immersion of said flexible tubular conduit (16; said flexible tubular duct extends U-shaped between said support means (26, 30, 31; 52, 53, 54) and said retaining means (20; 48); and,

said ends (24, 32, 56, 58) are progressively guided towards said seabed (15) so as to support said flexible tubular duct (16; 44) on said seabed.

2. Installation method according to claim 1, characterized in that one hooks said one end (24; 56) to said support means (26, 30, 31; 52, 53, 54) with a traction cable (28). 54).

3. Installation method according to claim 1 or 2, characterized in that provides a flexible tubular pipe (16; 44) pre-wound.

4. Installation method according to claim 3, characterized in that it provides immersion means comprising unwinding means of said flexible tubular pipe (16; 44) pre-wound.

5. Installation method according to claim 3 or 4, characterized in that said installation comprises a laying boat (40) and in that one installs said retaining means (48) and said support means (52, 53, 54 ) on said laying boat.

6. Installation method according to any one of claims 1 to 5, characterized in that provides a surface installation comprising a laying ship (12) and a support vessel (14), and in that installs said retaining means (20) on said laying ship (12) and said support means (26, 30, 31) on said support vessel (14).

7. A set of flexible underwater tubular pipe (16; 44) installation on a deep seabed (15) for the transport of hydrocarbons, said assembly comprising:

- a surface installation (12, 14; 40) capable of floating on the surface of the water of a marine environment (13);

a flexible tubular duct (16; 44) intended to be extended longitudinally between two opposite ends (24, 32; 56, 58); - retaining means (20; 48) installed on said surface installation (12, 14) for retaining said flexible tubular conduit;

means for progressively immersing said flexible underwater tubular pipe in said marine environment, at one of its ends (24; 56) to the other of its ends (32; 58) retaining it with said retaining means (20; 48) during immersion;

- means (28, 34; 54, 60) for guiding said flexible tubular conduit to said seabed (15) to press against said seabed; characterized in that it further comprises support means (26, 30,

31; 52, 53, 54) resting on said surface installation (12, 14) for hooking said one end (24, 56) to said support means so as to retain said one of said ends during immersion of said flexible tubular conduit (16; 44), while said flexible tubular duct extends U-shaped between said support means (26, 30, 31; 52, 53, 54) and said retaining means (20); and in that said ends (24, 32; 56, 58) are progressively guided towards said seabed to support said flexible tubular pipe (16; 44) on said seabed (15).