WO2015104580A2

WO2015104580A2 - Umbilical

Info

Publication number: WO2015104580A2
Application number: PCT/IB2014/003247
Authority: WO
Inventors: Yann PROBYN; Alan Deighton; Daniel Grayson
Original assignee: Technip France
Priority date: 2013-12-23
Filing date: 2014-12-19
Publication date: 2015-07-16
Also published as: WO2015104580A3; GB201322909D0; GB2521622B; GB2521622A

Abstract

An umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath, characterized in that the filler material is crenellated around its circumference to provide crenellations between the filler material and the outer sheath. In this way, the umbilical now includes crenellations or a crenelated portion facing the outer sheath, which can act as a shock absorber against external impact on the umbilical, with no additional manufacturing steps required. This provides the umbilical with increased impact resistance.

Description

Umbilical The present invention relates to an umbilical for use in the offshore production of hydrocarbons, and in particular to an electrical subsea power cable.

An umbilical for use in the offshore production of hydrocarbons generally comprises a group of one or more types of elongated active umbilical components, such as electrical cables, optical fibre cables, steel pipes and/or hoses, cabled together for flexibility, over-sheathed and, when applicable, armoured for mechanical strength. Umbilicals are typically used for transmitting power, signals and/or working fluids (for example for fluid injection, hydraulic power, gas release, etc.) to and from a subsea installation.

The umbilical cross-section is generally circular, the elongated elements being wound together either in a helical or in an S/Z pattern. In order to fill the interstitial voids between the various umbilical elements and to obtain the desired configuration, filler components may be included within the voids.

ISO 13628-5 "Specification for Subsea Umbilicals", provides standards for the design and manufacture of such umbilicals. The main load carrying components in charge of withstanding the tensile loads due to the suspended weight of the umbilical below the laying ship are usually tubes (US6472614, W093/17176, GB2316990), steel rods (US6472614), composite rods (WO2005/124095, US2007/0251694), steel ropes (GB2326177, WO2005/124095), composites ropes (GB2326177) or tensile armour layers (see Figure 1 of US6472614).

WO2008/075965A discloses an umbilical having a plurality of load carrying umbilical components arranged as an outer layer and surrounded by an outer sheath. A filler material between the umbilical components can be configured with longitudinally extending grooves or flutes formed therein such that the material that forms the outer sheath penetrates into these grooves when extruded onto the umbilical bundle. An additional tape strength band can provide a temporary function by being wound circumferentially by a predetermined space between each winding to allow the sheath material to access the grooves. The grooves or flutes assist in resisting rotational movement between the outer sheath and the umbilical bundle.

To reduce installation costs, umbilicals may simply be laid on or next to the seabed between the relevant installations, rather than being buried or otherwise protected by a layer of hardened material such as concrete. But, by only being laid on or next to the seabed, they are susceptible to damage by anything hitting or even 'coming across' the umbilical. This includes chains or anchors used by vessels and tankers, and 'dumping' such as rock dumping of unwanted waste by vessels from another situation or site.

The addition of one or more armour layers is regularly used to increase the umbilical 'protection', but this also adds to material costs and can involve a more complex manufacturing process, and hence not achieve a cost-effective umbilical for some applications.

It is an object of the present invention to provide an umbilical with improved impact resistance.

Thus, according to one aspect of the present invention, there is provided an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath,

characterized in that the filler material is crenellated around its circumference to provide crenellations between the filler material and the outer sheath. In this way, the umbilical now includes crenellations or a crenelated portion under and the outer sheath, and facing the outer sheath, which can act as a shock absorber against external impact on the umbilical, with no additional manufacturing steps required. This provides the umbilical with increased impact resistance.

Preferably, the crenellations are occupied with a shock absorbing material. Such material may be homogeneous or heterogeneous, and may include any suitable solid, fluid and/or gas, or combination of same, but not including the outer sheath. Such materials include 'air', such as the air remaining in the crenellations during manufacture prior to the application of the outer sheath, optionally at ambient pressure or a higher or lower pressure. Such materials also include sea water, and a mixture of air and sea water.

Optionally, one or more solid shock absorber materials could be added into the crenellations, such materials being different to the filler material.

In particular, it is noted that the outer sheath does not extend into the core and/or crenellations, and that the crenellations are created, provided or formed to act as a shock absorber layer under the outer sheath.

As mentioned above, an umbilical can consist of a group of one or more types of elongated active umbilical components, including but not limited to electrical cables, optical fibre cables, steel tubes, conduits, hoses, steel rods, composite rods, steel ropes and composite ropes, cabled together for flexibility. Along with the filler material therearound, these elongated components form the core.

The outer sheath may be made from any suitable material, generally being formed from one or more polymers, able to be formed around the core to provide an external protective layer, and optionally also a smooth layer.

To assist the bundling of the umbilical components prior to the addition of the outer sheath, a tape may be applied around the outer layer of umbilical components. Such tape can be simply wound around the core in a known manner, generally in a helical lay. The tape can be termed a "closure tape" or "strength band", and provides closure and/or strength to the collocation of the umbilical components prior to the addition, generally extrusion, of the outer sheath therearound.

The filler material may be made from any suitable material or materials. The filler material is preferably made from a polymer material.

Optionally, the filler material and the crenellations may be formed by extrusion. Extruded filler material relies on a die to shape a moving polymer melt followed by shaping and cooling devices downstream to form an extrudate into the final desired shape and size. An extrusion process makes it possible to manufacture directly crenellated portions, the shape of the crenellation being dependent upon the shape of the extrusion die. When the crenellations are formed directly by extrusion, the longitudinal axis of the crenellations is parallel to the longitudinal axis of the extruded elongated portions.

Additionally or alternatively, the filler material and the crenellations may be formed by providing, such as by extruding, smooth pieces without crenellations and then machining to form the crenellations in the smooth pieces.

Additionally or alternatively, the filler material and the crenellations may be formed by extrusion of filler material around the umbilical components as a single unit or piece comprising crenellations therewith.

The skilled man is not limited by the methods of providing the filler material and crenellations. Preforming directly crenellated pieces for subsequent use in the umbilical manufacturing process may provide a simpler manufacturing process, although the skilled man can see different reasons and advantages in using one or more of the above processes.

According to a preferred embodiment, the filler material comprises a plurality of elongate portions in the form of circular segments, for example 3 elongate portions or more, and each elongate portion is made from an extruded elongated profile comprising crenellations along an arcuate side. These elongated portions can be extruded separately, (optionally in or as a single process line), and with lines of the portions then assembled together around and/or with the umbilical components in a helical or S/Z pattern to form the final or combined filler material around the core.

The crenellations may extend partly, substantially or wholly around the circumference of the filler material, may be regularly or irregularly spaced, and may have the same of different cross-sectional shapes, or any combination of these.

One embodiment of the present invention is for the crenellations to be evenly shaped and evenly distributed all around the circumference of the umbilical.

The shape of the crenellations (or alternatively 'grooves' or 'depressions' or 'crenels') is preferably rectangular, rounded rectangular, trapezoidal (isosceles trapezium) or rounded trapezoidal.

The depth of the crenellations (or alternatively depth of the grooves etc.) is not limiting, and may depend on the size of the umbilical. Optionally, the depth of the crenellations is between 5mm and 25mm. The width of the crenellations (or alternatively width of the grooves etc.) is again not limiting, and may depend on the size of the umbilical. Optionally, the width of the crenellations is between 5mm and 25mm. The spacing between adjacent grooves, depressions or crenels is also not limiting, and may depend on the size of the umbilical. Optionally, the spacing of the crenellations is between 10mm and 50mm.

Optionally, the umbilical includes one or armour layers between the filler material and the outer sheath. Each armour layer may comprise metal wires or metal tapes wound around the filler material in a helical or S/Z pattern. One or more of the armour layers may comprise one or more steel tapes, such as in the range 4-25 steel tapes, optionally applied at a low pitch angle such as comprised between 10^Q to 55°, preferably comprised between 10° and 30° Preferably, the umbilical includes at least one steel tape armour layer between the filler material and the outer sheath. In many situations, the use of a steel tape layer for tensile strength may avoid the need for additional armour layers, thereby reducing the complexity and number of steps of the umbilical manufacturing process, and thus the overall umbilical cost.

In particular, a steel tape layer can provide better protection against impact, such as rock dumping. A steel tape layer also improve the electromagnetic behavior of any electrical cables in the core, by providing an improved metallic shield around electrical cables compared to round armour layers such as those comprising metal wires.

In an embodiment of the present invention, the umbilical comprises one (inner) armour layer of steel tapes wound around the filler material at a pitch of between 10^Q and 55^Q, and a further (outer) armour layer therearound. In this embodiment, the inner armour layer of steel tapes has two functions. First, it cooperates with the crenellated filler material to improve the impact resistance of the umbilical. Second, it takes a part of the tensile load applied onto the umbilical, the remaining part being taken by the further armour layer. The further armour layer is preferably cross wound with the inner armour of steel tapes (with opposite pitch angles) to provide a torque balance structure (i.e. to prevent the umbilical from twisting under tensile loading). The double function of the inner armour layer of steel tapes provides a particularly economically advantageous final umbilical.

The width of the steel tapes of any inner armour layer is preferably larger than the width of the crenellations of the material filler, so that the tape can 'cover' the grooves, even if the helix angle of the tape is close to the helix angle of the crenellations. This adds to the stability of the final umbilical. Preferably, the width of such steel tapes is at least twice the width of the crenellations of the filler material, more preferably at least three times the width of the crenellations of the filler material. For the same reason (stable seating of the tapes on or around or over the crenellations), when the crenellated filler material is arranged in a helical pattern around the umbilical components, the inner armour layer of steel tape is preferably helically wound in the opposite direction; (for example, if the crenellated filler material is wound clockwise, the inner armour layer of steel tapes is wound anticlockwise).

The outer sheath can be applied around the core in a manner known in the art, commonly by the application of an extruded polymer or a polymer braid along the umbilical in a regular and constant manner.

The filler material may be provided as a single unit or piece. Optionally, and as described hereinbefore, the filler material comprises a plurality of elongate circular segment portions, more optionally 2-4 portions such as 3 portions. Thus, the filler material can be applied around the umbilical components by being supplied along a travelling longitudinal process line from one or more different angles, in a manner known in the art.

During manufacturing, the crenellations may be filled with any one or more shock absorbing materials, including a suitable fluid or combinations of fluids, such materials being different to the filler material and outer sheath. In an alternative, the crenellations remain occupied with the air remaining in the crenellations prior to application of the outer sheath, or optionally one or more armour layers.

After manufacturing, the crenellations may be filled with any one or more shock absorbing materials, any suitable fluid or combinations of fluid. When the umbilical is installed subsea, the filler material may be 'flooded', such that the crenellations are then filled partly, substantially or wholly with sea water, e.g an air and sea water mixture.

The umbilical is preferably an electrical subsea power cable, more preferably comprising one or more copper or aluminium conductor cores, and optionally one or more fibre optic cables.

According to a second aspect of the present invention, there is provided a method of manufacturing an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components, and a crenellated filler material as described herein and located between the umbilical components and the outer sheath, comprising at least the steps of:

(a) locating the plurality of umbilical components together to form the core;

(b) locating the crenellated filler material around the core; and

(c) locating the outer sheath around the crenellated filler material.

In this way, crenellations are formed under the outer sheath to act as a shock absorber.

Preferably, the method of manufacturing further comprises the step of occupying the crenellations provided between the filler material and the outer sheath with a shock-absorbing material, which may be more than one material, and such as described herein above.

Preferably, the method of manufacturing further comprises one or more of the steps in the group comprising:

(i) locating the plurality of umbilical components together in a helical manner to form the core;

(ii) locating the crenellated filler material around the core in a helical manner; (iii) providing the crenellated filler material in a plurality of elongate circular segment portions, optionally 2-4 portions such as 3 portions; and

(iv) providing one or armour layers between the crenellated filler material and the outer sheath, with any such armour layers optionally comprising metal wires or metal tapes, and further optionally wound around the crenellated filler material in a helical or S/Z pattern.

In one embodiment of the present invention, the method of manufacturing an umbilical comprises the steps of:

(a) locating the plurality of umbilical components together in a helical manner to form the core;

(b) providing the crenellated filler material in 2-4 preformed extruded elongate portions;

(c) locating the crenellated filler material portions around the core in a helical manner to form a combined filler material that is crenellated around its circumference;

(d) providing two armour layers as inner and outer armour layers around the combined crenellated filler material portions in the form of metal tapes having at least twice the width of the width of the crenellations of the filler material;

(e) locating the inner layer of metal tapes in a helical manner in the opposite direction as the helical winding direction of the crenellated filler material; and

(f) locating the outer sheath around the outer armour layer to form the umbilical. According to a third aspect of the present invention, there is provided a method of improving the impact resistance of an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath, the method characterized in forming crenellations in the circumference of filler material. In this way, crenellations are formed under the outer sheath to act as a shock absorber.

Preferably, the method further comprises occupying the crenellations with a shock- absorbing material, which may be more than one material, and such as described herein above.

According to a fourth aspect of the present invention, there is provided a method of forming a crenellated filler material portion comprising extruding a polymer melt of filler material through a die with a die-shape able to form an extrudate as a circular segment having a cross-section with a crenellated arcuate edge.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying Figure 1 showing a cross sectional view of an umbilical according to one embodiment of the present invention.

Figure 1 shows an electrical subsea power cable umbilical 1, which could be for use in the offshore production of hydrocarbons or as part of a subsea electrical network, or as part of an offshore renewable energy generation facility such as a wind farm.

The umbilical 1 includes three central power cables 3, an optical fiber cable 4, a central polymer filler rod 5, and three filler material portions 6-8, which together form a core, all of which is then enclosed by an outer sheath 10. In addition, there are two steel tape armour layers 12 between the outer sheath 10 and the core.

The crenellations in the three filler material portions 6-8 are preferably formed by extrusion to provide crenellations having a general rounded rectangular shape, i.e. a rectangular cross-section, with rounded corners or cornering, to provide a continuously smooth contoured surface. For this, the three filler material portions 6-8 can either be formed in a single extrusion process and then divided into three lengths (for simultaneous combination around the umbilical core), or formed from one manufacturing line at different times, to provide the three filler material portions 6-8 required in the subsequent umbilical manufacturing process. To provide the example portions 6-8 shown in Figure 1, the filler material extruder has a die with the cross-sectional shape as shown in Figure 1. That is, the filler material portions 6-8 are 'crenellated' along their longest edge or arc, which forms part of the overall 'circumference' of the filler material when the portions 6-8 are brought together. The crenellations 14 are symmetrically and regularly spaced around these arcuate edges, such that the crenellations in the combined circumference the combined filler material portions 6-8 are symmetrically and regularly spaced.

It is noted that the crenellations may also be termed 'crenels', 'grooves' or 'indentations'. The overall intention is to provide the overall circumference of the filler material with 'crenellations', or 'to be crenellated' with indentations.

The umbilical 1 shown in figure 1 can be formed in 3 steps. The first step forms a core by winding, in a helical pattern and around the central polymer filler rod 5, the three central power cables 3, and the optical fiber cable 4. The three filler material portions 6-8 can then be added as part of the continuation of the first winding step. The second step forms the steel tape armour layers 12 by winding two sets of steel tapes around the filler material portions 6-8 in a helical pattern, and in an opposite direction compared to the winding direction of the core (e.g. clockwise - anticlockwise as described herein above). The last step is extruding the outer sheath 10 around the armour layer 12.

When the so-formed umbilical 1 is installed subsea, the crenellations 14 can be wholly or partly flooded to become sea water 'pockets'. These sea water pockets provide impact resistance against impacts and shocks, in particular shocks from items or apparatus hitting the umbilical 1 on the seabed, or material being dumped on the seabed such as rock dumping. The sea water pockets, by being filled with sea water and therefore having the compressive resistance of water, allow the umbilical manufacturer to consider reduction in the number and/or depth of any armour layers otherwise required, thereby reducing the manufacturing process and overall manufacturing cost for such an umbilical.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.

Claims

1. An umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath,

characterized in that the filler material is crenellated around its circumference to provide crenellations between the filler material and the outer sheath.

2 An umbilical as claimed in claim 1 wherein the crenellations are occupied with a shock-absorbing material.

3. An umbilical as claimed in claim 1 or claim 2 wherein the crenellations are regularly spaced around the circumference.

4. An umbilical as claimed in any one of the preceding claims wherein the umbilical includes one or more armour layers between the filler material and the outer sheath.

5. An umbilical as claimed in claim 4 wherein at least one armour layer comprises steel tapes wound around the filler material in a helical or S/Z pattern.

6. An umbilical as claimed in claim 5 wherein the width of the steel tapes is larger than the width of the crenellations of the material filler, preferably at least twice the width of the crenellations of the material filler.

7. An umbilical as claimed in any one of claims 4 to 6 comprising an armour layer of steel tapes wound around the filler material at a pitch of between 10^Q and 55° and a further armour layer therearound.

8. An umbilical as claimed in any one of the preceding claims wherein the filler material comprises a plurality of elongate portions, optionally 2-4 portions.

9. An umbilical as claimed in any one of the preceding claims wherein the crenellations are filled with air, or sea water, or a mixture of air and sea water.

10. An umbilical as claimed in any one of the preceding claims wherein the umbilical is an electrical subsea power cable.

11. A method of manufacturing an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components, and a crenellated filler material as defined in any one of claims 1 to 10 located between the core and the outer sheath, comprising at least the steps of:

(a) locating the plurality of umbilical components together to form the core;

(b) locating the crenellated filler material around the core; and

(c) locating the outer sheath around the crenellated filler material.

12. A method of manufacturing an umbilical as claimed in claim 11 further comprising the step of occupying the crenellations provided between the filler material and the outer sheath with a shock-absorbing material.

13. A method of manufacturing an umbilical as claimed in claim 11 or claim 12 further comprising one or more of the steps in the group comprising:

(ii) locating the crenellated filler material around the core in a helical manner;

(iii) providing the crenellated filler material in a plurality of elongate portions, optionally 2-4 portions such as 3 portions; and

14. A method of manufacturing an umbilical as claimed in any one of claims 11 to 13 comprising the steps of: (a) locating the plurality of umbilical components together in a helical manner to form the core;

(e) locating the inner layer of metal tapes in a helical manner in the opposite direction as the helical winding direction of the crenellated filler material; and (f) locating the outer sheath around the outer armour layer to form the umbilical.

15. A method of improving the impact resistance of an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath, the method characterized in forming crenellations in the circumference of the filler material.

16. A method as claimed in claim 15 further comprising occupying the crenellations with a shock-absorbing material.

17. A method of forming a crenellated filler material portion for use in an umbilical comprising an outer sheath and a core enclosed by the outer sheath, the core comprising a plurality of umbilical components and filler material between the umbilical components and the outer sheath, the method comprising extruding a polymer melt of filler material through a die with a die-shape able to form an extrudate as a circular segment having a cross-section with a crenellated arcuate edge.