MXPA06005035A - Method and apparatus for laying a pipeline - Google Patents

Abstract

A method and apparatus for laying an underwater pipeline. The method includes the steps of constructing lengths of pipeline by endwise connection of a plurality ofpipe segments (12) and securing bend restriction means (18) along the length of said lengths of pipeline. The bend restriction means (18) is arranged to prevent the lengths of pipeline from bending by more than a predetermined maximum amount. Flotation means (28) are secured to the lengths of pipeline such that the lengths of pipeline are held adjacent the surface of the ocean and the lengths of pipeline are towed to the desired location. Each length of pipeline is connected to an adjacent length of pipeline and the flotation means (28) are released from each length of pipeline so that the length of pipeline sinks to the ocean floor.

Description

METHOD AND APPARATUS FOR TENDERING A PIPE BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for the installation of pipelines offshore.

FIELD OF THE INVENTION The installation of offshore pipelines for hydrocarbon transportation from an offshore location generally involves the use of specialized pipe laying vessels to lay the pipe segments in the ocean floor. A common method for laying the pipeline involves the use of pipe laying vessels that carry short lengths of pipe, for example, 12 meters, which are welded end to end along the length of the pipeline in the laying vessel. pipeline. This method requires that the vessels be equipped in a special way, both to transport the segments of pipe and to weld and tend the segments. It is common for such pipe laying vessels to require crews of around 200 people from various technical experiences to perform the operation. It is normal for such operations to be able to lay about 1 to 2 kilometers of pipe per day at a cost (based on current figures) of around 0.3 to 0.5 million US dollars per day. The present invention relates to a method for installing offshore pipe, which does not require the use of the specialized pipe laying vessels mentioned above, thus reducing the cost of pipe laying operations and which allows to install a longer span. of tubing per day.

BRIEF DESCRIPTION OF THE INVENTION In accordance with one aspect of the present invention, there is provided a method for laying a submarine pipe comprising the water passages: constructing pipe stretches by connecting at the ends of a plurality of pipe segments; securing fold restriction means to said sections of pipe, the bend restriction means are arranged to prevent the pipe sections from bending by more than a predetermined maximum amount; securing the flotation means to the pipe sections, so that the pipe sections are supported adjacent to the surface of the ocean; haul the pipe sections to the desired location; and connecting each section of pipe to an adjacent section of pipe and altering the buoyancy of the flotation entries or releasing the flotation means from each section of pipe, so that the section of pipe is submerged to the floor of the ocean. According to another aspect of the present invention, there is provided an apparatus for laying a subsea pipeline comprising: bending restriction means arranged to be secured to sections of pipe formed by connecting at the ends of a plurality of pipe segments, the bending restriction means being arranged to prevent the pipe sections from bending by more than a predetermined maximum amount; and flotation means arranged to be secured to the pipe sections, so that the pipe sections are supported adjacent to the surface of the ocean; wherein the flotation means are releasable from the pipe section or may have their buoyancy altered, so that the pipe sections may be hauled to a desired location and submerged to the ocean floor by releasing the flotation means or altering the buoyancy of the means of flotation.

DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a section of pipe prepared for laying in accordance with the present invention; Figure 2 is a side view of the bend restriction means of Figure 1; Figure 3 is a side view of a segment of the bend restriction means of Figure 1; Figure 4 is a side view of a section of pipe ready to be laid according to an alternative embodiment of the present invention; Figure 5 is a side view of the bend restriction means of Figure 4; Figure 6a is a side view of a segment of the bend restriction means of Figure 4; Figure 6b is a side view of an alternative embodiment of a segment of the bend restriction means of Figure 4; Figure 6c is a side view of a further alternative embodiment of a segment of the bend restriction means of Figure 4; Figure 7a is a side view of tubing location means for use with the method of the present invention; Figure 7b is a top view of the pipe location means of Figure 7a; Figure 8 is a side view of the pipe of Figure 1 during the laying of a length of pipe; Figure 9 is a side view of the connection of adjacent sections of pipe; and Figure 10 is a side view of the release of the fold restriction means.

DESCRIPTION OF THE INVENTION Referring to the Figures, a method of and an apparatus for laying a submarine pipe 10 comprising a plurality of pipe segments 12 is shown. The pipe segments 12 are connected end to end on the beach by a means known, such as welding, to form one or more lengths of pipe 14. The lengths of pipe 14 are manufactured in the total length desired for pipe 10 or in multiples of a length that would, in total, form the desired length of the pipe. pipe 10. For example, pipe lengths 14 may be in the order of 5 to 10 kilometers. The use of such lengths of pipe 14 will allow large sections of pipe 10 to be installed in a single operation. Following the construction of each of the pipe sections 14, a bend restriction means 16 is secured along the length of pipe 14. The bend restriction means 16 comprises a plurality of connected bend restriction segments 18. Figures 2 and 3 show an embodiment of the fold restriction segments 18 and the bend restriction means 16 shown in Figure 1. The bend restriction segments 18 each comprise a cylindrical member 20 having longitudinally opposite hemispherical ends 22. Each cylindrical member 20 is secured to adjacent cylindrical elements 20 by a flexible elongated member 24, such as a chain or cable, which is connected between the points centrally located at the hemispherical ends 22. The length of each flexible elongated member 24 and the dimensions of the cylindrical elements 20 are arranged so that when a cylindrical element 20 is such that the longitudinal axis of the cylindrical element 20 has moved. of being coaxial with the longitudinal axis of a cylindrical element 20 connected by a predetermined angle, the hemispherical ends 22 of those connected cylindrical elements 20 come into contact with each other preventing further movement. By fixing the maximum allowed angle between the longitudinal axes of the adjacent cylindrical elements 20 for the cylindrical elements 20 of known length, the bending restriction means 16 will only be bent to a limited degree, as shown in Figure 3. The means of bending restriction 16, when it is secured along the length of pipe 14, would thereby prevent excessive bending of pipe section 14 and would allow a minimum bending radius to be fixed for pipe section 14. As shown in Figure 1 , the bend restriction means 16 is disposed adjacent the pipe section 12 and connected along the length by connections between each bend restriction segment 18 and the pipe section 14. The method and apparatus for laying the pipe 10 also involves the use of flotation means 26 attached to the length of pipe 12 along the length. In the embodiment shown in Figure 1, the floatation means 26 comprises a plurality of floatation modules 28, each flotation module 28 being connected to a respective bending restriction segment 18. The floatation means 26 is arranged so that the length of pipe 14 will float adjacent to the surface of the ocean. The length of pipe 14 can then be secured to a towing or towing vessel 29 and hauled to the desired location. It is noted that the required towing or towing vessel 29 does not need to be of the specialized type conventionally used in pipe laying operations, thereby saving costs.

Figure 4 shows an alternative embodiment of the invention as shown in Figure 1. In this embodiment, the bend restriction means 16 comprises fold restriction segments 16 comprising fold restriction segments 18 as shown in Figures 6a, 6b and 6c. The bend restriction segments 18 are secured by flexible elongated members 24 and function to restrict the bend of the pipe sections 14 generally as previously described. Although the bend restriction segments 18 do not have the hemispherical ends 22 of the fold restriction segments 18 shown in Figures 2 and 3, the longitudinally opposite ends 31 perform the same function. The bend restriction segments 1 8 each comprise a frame 30 supporting an internal float module 32. The frame 30 comprises a cylinder or a prism having a cross section of any suitable shape. For example, the frame 30 of Figure 5b comprises a hexagonal prism and the frame 30 of Figure 5c comprises a rectangular prism. The flotation modules 32 are located within the frame 30 along the longitudinal axis of the fold restriction segment 18. Each of the fold restriction segments 18 is connected to adjacent bend restriction segments 18 by flexible elongate members 24. connected between the adjacent ends of the flotation modules 32. In this embodiment, therefore, separate flotation modules are not required. The pipe sections 14 are hauled to the desired location, which preferably will have been marked before based on inspections of the ocean floor. The markers 34 are shown in Figures 7a and 7b and can be used to mark the location of the desired route of the pipe 10. As shown in Figure 8, using the embodiment of the invention shown in Figure 1, the stretch of pipe 14 is then simply laid down when the flotation modules 28 are disengaged from the bending restriction means 16, thereby allowing the section of pipe 14 to be submerged to the ocean floor. The bend restriction means 16 prevents excessive bending of the pipe section 14 both during the hauling operation and as the pipe section 14 sinks to the ocean floor, thus preventing damage. Alternatively, using the embodiment in Figure 4, the buoyancy of the flotation modules 28 can be altered by filling with seawater to allow the pipe section 14 to sink to the ocean floor. Once on the ocean floor, the bending restriction means 16 is removed from each section of pipe 14 with the exception of a portion of the bending restriction means 16 adjacent to the ends of the pipe section 14. The ends of sections Adjacent pipes 14 are then raised to the surface, as shown in Figure 9, by a davit elevator and connected in a known manner. The portions of the bending restriction means 16 adjacent the ends of the pipe sections 14 prevent damage to the pipe sections 14 during the mooring operation. The connected pipe sections 14 are then placed back on the ocean floor and the portions of the bending restriction means 16 adjacent to the ends of the pipe section 14 are removed. The bend restriction means 16 can be released from the pipe sections 14 by any suitable means, such as a hook block or a diver assisted operation. Modifications and variations as would be apparent to an expert are considered within the scope of the present invention.

Claims (12)

1 . A method for laying a subsea pipeline comprising the steps of: (i) constructing pipe sections by connecting at the ends of a plurality of pipe segments; (ii) securing bending restriction means to said section of pipe, said bending restriction means comprises a plurality of bending restriction segments, each bending restriction segment is connected to an adjacent bending restriction segment by a member elongate flexible, so as to prevent the pipe section from being bent by more than a predetermined maximum amount; (iii) securing flotation means to the pipe sections, so that the pipe sections are supported adjacent to the surface of the ocean; (iv) hauling the pipe sections to a desired location; and (v) connecting each section of pipe to an adjacent pipe section and altering the buoyancy of the flotation means or releasing the flotation means from each section of pipe, so that the pipe section sinks to the floor of the ocean. A method for laying a submarine pipeline according to claim 1, wherein the floatation means comprises a plurality of floatation modules connected in series, the method includes the steps of securing each of the floatation modules to a segment of respective bending restriction.

3. A method for laying a subsea pipeline according to any of claims 1 or 2, including the step of removing the bending restriction means from each of the pipe sections, with the exception of a portion of the restriction means. of bending adjacent to one end of the length of pipe after each length of pipe has descended to the ocean floor.

A method for laying an underwater pipeline according to claim 3, including the step of raising the ends of pipe sections adjacent to the surface of the ocean, connecting said adjacent ends together and lowering the adjacent ends connected to the ocean floor.

A method for laying an underwater pipeline according to claim 4, which includes the step of removing the portions of the bending restriction means from the ends of the pipe sections once the adjacent pipe sections have been connected. and down to the ocean floor.

6. A method for laying a submarine pipeline according to any of claims 1 to 5, wherein altering the buoyancy of the flotation means comprises at least partially filling the flotation means with seawater.

A method for laying an underwater pipeline according to any of claims 1 to 6, including the step of placing a plurality of insured buoyancy markers at locations on the ocean floor along the proposed route of the underwater pipeline .

8. An apparatus for laying a submarine pipeline comprising: bending restriction means comprising a plurality of fold restriction segments connected in series arranged to be secured to lengths of pipe formed by connecting at the ends of a plurality of pipe segments, each bend restriction segment is connected to adjacent bend restriction segments by a flexible elongate member, the length of the flexible elongate member and the dimensions of the bend restriction segments are arranged so that the bend restriction means will be bent no more than a predetermined minimum bend radius; and flotation means arranged to be secured to the pipe sections, so that the pipe sections are supported adjacent to the surface of the ocean; wherein the flotation means are releasable from the pipe section or may have their buoyancy altered, so that the pipe sections may be hauled to a desired location and sunk to the ocean floor by releasing the flotation means or altering the buoyancy of flotation means.

An apparatus for laying a subsea pipeline according to claim 8, wherein the floatation means comprises a plurality of floatation modules connected in series, each float module being connected to a respective bending restriction segment.

10. An apparatus for laying a submarine pipeline according to claim 8 or 9, wherein each of the fold restriction segments comprises a solid cylindrical element having longitudinally opposite hemispherical ends, the flexible elongate members being connected between adjacent cylindrical elements at points located centrally on adjacent hemispheric ends. eleven .

An apparatus for laying an underwater pipeline according to claim 8 or 9, wherein each of the bend restriction segments comprises a frame having one of the flotation modules mounted therein.

12. An apparatus for laying an underwater pipeline according to claim 1, wherein the frame is constructed as a cylinder or prism and the flotation module is located along a central longitudinal axis of the frame. An apparatus for laying an underwater pipeline according to claim 12, wherein the flexible elongate members are connected between adjacent ends of the float modules of adjacent bend restriction segments.