Multiple-tube flexible pipe having high compressive strength

Details Multiple-tube flexible pipe having high compressive strength Multiple-tube flexible pipe having high compressive strength

1998-05-26

2000-08-15

Kashnikow, Andres

Pipes and tubular conduits

Plural duct

Longitudinally extending common wall

138148, F16L 1100, F16L 914

Patent

active

06102077&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a flexible pipeline intended to connect, for example, a subsea oil well head to a subsea or floating oil production facility.
A subsea oil well head is usually connected to a subsea or floating oil production facility via several pipelines, including: liquid hydrocarbons; for conveying gaseous hydrocarbons, on degassing, or compressed gas for forcing up liquid hydrocarbons; pipes and/or electrical and/or optical cables for power and/or information transmission.
The flexible pipes used for serving production and service lines have a high mechanical strength, in particular a high resistance to internal pressure, a high tensile strength and a high compressive resistance, and are usually laid by means of tensioning devices comprising caterpillar tracks provided with pads which grip the pipe and move translationally over a given path in order to jointly entrain it.
The tensile loads applied by these caterpillar-track tensioning devices to a flexible pipe may be considerable when laying at great depth, and the compressive forces exerted by the pads on the pipe must be high enough to avoid any relative slippage between the pads and the pipe.
The control umbilicals have a lower resistance to compressive loads than the flexible pipes serving as production or service lines, because of the presence of compression-sensitive pipes, and they cannot be laid by means of caterpillar-track tensioning devices.
The umbilicals are generally laid using winches, the tensile loads being transferred by at least one metal armouring layer located in the pipe's outer jacket.
Moreover, the electrical and/or optical cables present in the umbilicals have a low tensile strength.
Now, the tensile stresses to which the various layers of a cable bundle under bending may be subjected increase as one goes further away from the central axis (or neutral fiber).
It is therefore preferred to place the electrical and/or optical cables of a control umbilical as close as possible to the central axis. If the control umbilical has a central pipe, the latter cannot exceed a certain diameter in order to avoid subjecting the electrical and/or optical cables wound around the latter to excessively high stresses liable to break them.
In practice, the external diameter of umbilicals therefore does not exceed 200 mm.
The current trend is to increase the number of subsea well heads connected to a single production facility.
The Applicant proposed, at the Offshore Technology Conference in Houston, Tex., in 1987, simplifying the operations of laying and handling the production and service lines and control umbilicals by combining them into multipipe pipelines which are more compact and easier to handle and lay.
However, these multipipe pipelines must: or when they pass between the pads of a caterpillar-track laying or handling device; and mechanical stresses due to swell.
The pipelines as described in the aforementioned conference, which comprise compression-sensitive peripheral pipes, are incapable of withstanding the passage through caterpillar-track tensioning devices.
DE-A-1 918 575 relates to a multi-tube flexible pipe, but not comprising a flexible compressive-load-transferring member arranged in an annular space provided in said multiple-tube flexible pipe.
The subjet of the present invention is a novel multipipe flexible pipeline making it possible to simplify the laying and handling operations, of the type comprising a central flexible element with a high tensile strength and a high compressive strength and a plurality of peripheral pipes wound around the said central flexible element in at least one ply in an annular space lying between the said central flexible element and a jacket, at least one of the said peripheral pipes being a compression- and/or tension-sensitive pipe.
The central flexible element is typically a flexible tubular pipe of the type used for serving production lines and is manufactured in long lengths by the Applicant.
As a variant, the central flexible element comprises

REFERENCES:
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patent: 3872893 (1975-03-01), Roberts
patent: 4098333 (1978-07-01), Wells et al.
patent: 4162865 (1979-07-01), Aubet
patent: 4332509 (1982-06-01), Reynard et al.
patent: 4974408 (1990-12-01), Karhu
patent: 5202076 (1993-04-01), Carlstrom
patent: 5362921 (1994-11-01), Birkelund et al.

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