[0001] Embodiments of the present invention relate to apparatus and methods for installing one or more longitudinally extensive protection apparatus on an offshore structure. The longitudinally extensive protection apparatus can, in a final use condition, have disposed therein one or more longitudinally extensive service members.

[0002] In some embodiments, the offshore structure can be a structure associated with offshore electricity generation, such as a wind turbine generator or a substation or collecting station associated with a field or group of wind turbine generators (WTGs). In some embodiments of the invention, the offshore structure can include a foundation to which the longitudinally extensive protection apparatus can be mounted.

[0003] In further embodiments, the offshore structure can be an installation associated with the oil and gas extraction industries, such as an oil or gas rig. Such offshore structures can also include a foundation to which the longitudinally extensive protection apparatus can be mounted.

[0004] In some embodiments of the invention the longitudinally extensive service member can comprise one or more cables. The cables can be configured for the transmission of electricity such as electricity generated by a wind turbine generator, or such as electricity for consumption on the offshore structure. The one or more cables can also be used for information or data transmission, such as for control or monitoring of equipment or apparatus on, or which is part of, the offshore structure. Such cable can include fibre optic cables.

[0005] For oil and gas installations, the longitudinally extensive service member can include one of more pipes for the transmission of fluids such as water, production fluids including oil and gas or downhole fluids.

BACKGROUND

[0006] Installation of apparatus and equipment on offshore structures is inherently expensive and a large element of that expense arises from factors associated with sea and weather conditions. For example, apparatus and equipment mounted on structures located offshore must be constructed in a manner which allows such apparatus and equipment to withstand, during their anticipated working life, the rigours of a harsh environment such as high winds, wave impacts, currents, corrosion due to salt water, water ingress and the like. In addition, for construction and maintenance of apparatus and equipment on an offshore structure weather and sea conditions can provide a very significant constraint on access to the offshore structure. Days when weather and sea conditions prevent access can mean that workers and equipment are held on standby until conditions improve, which is also expensive.

[0007] Further, in terms of both cost and safe working practices, it is advantageous to minimise the time and frequency which offshore workers must spend on offshore structures for construction or maintenance of the structure and its associated apparatus and equipment. For example, transfer of personnel from and to a service vessel to and from an offshore structure carries inherent risks which must be minimised.

[0008] Still further, any operations on an offshore structure which require work to be carried out beneath the water surface require the presence of divers and/or remotely controlled submersible vehicle (ROV). Both are expensive to provide and restricted in their use to suitably advantageous periods of weather and sea conditions.

[0009] In some embodiments the present disclosure relates to methods, apparatus and equipment for, or associated with, the provision of longitudinally extensive protection apparatus to an offshore structure such as wind turbine generators or an offshore structure associated with the oil and gas extraction industries. The longitudinally extensive protection apparatus can contain a longitudinally extensive service member. Methods according to embodiments of the invention can include installing the longitudinally extensive service member in the longitudinally extensive protection apparatus.

[0010] In some preferred embodiments, the offshore structure can be a foundation of a wind turbine generator and the longitudinally extensive service member can be a cable for electricity and/or a fibre optic cable.

[0011] As used herein, unless the context requires otherwise, "cable" includes both cables for transmission of electricity and fibre optic cables.

[0012] As is well known in the art, power is collected from an offshore WTG by way of a cable. Often, an array of WTGs is provided in a given location and power from the various WTGs may be collected by means of electrical cables which connect, in some

embodiments, to a collection station from which power can be taken ashore by means of a further cable.

[0013] Typically, each WTG is connected to a first end of a cable and the cable then runs along the sea bed to its next connection point (such as a collection station). In order to avoid damage to the cable, the cable may be buried beneath the sea bed for at least some of its length. A given WTG may have more than one cable connected thereto.

[0014] Proximate the WTG, the cable must rise away from the seabed for connection to the WTG. In some constructions, the WTG can be mounted on a foundation. The foundation can be mounted at the seabed. Floating foundations for offshore structures are also known and used. The cable can therefore be attached to or within the foundation at points on the upward path of the cable from the seabed to the WTG.

[0015] In typical prior art constructions the foundation may be provided with a J-tube or an l-tube which is secured to the foundation. I tubes and J-tubes are well known in the art and typically comprise a rigid tube of painted steel attached to the foundation. The l-tube or J-tube may be arranged generally vertically (in at least one plane). The cable enters the l-tube or J-tube at a lowermost end thereof proximate the seabed, passes through the I- tube or J-tube and emerges from the l-tube or J-tube at an upper end thereof, for connection, directly or indirectly to the WTG.

[0016] GB2496257A discloses one such arrangement whereby two mating connector parts are used to connect an offshore first electrical plant to a second electrical plant. The apparatus and method disclosed in this document enables electrical connector parts within a watertight housing to be brought together and form an electrical connection in an underwater environment. The device disclosed therein does not provide a means of feeding a longitudinally extensive service member such as an electrical cable into a protective apparatus prior to positioning the cable in its location of use proximate the sea bed.

[0017] A cable protection system (CPS) may be used in conjunction with an l-tube or J- tube. Conventionally a CPS can be formed from a plurality of individual conjoined sections. The CPS can have a bell mouth or dynamic bend stiffener at the vessel end (that is, the trailing end into which the cable passes when paid out from a vessel) of the CPS. In one procedure a cable can be pulled into a preinstalled CPS. In another procedure the CPS can be latched into the foundation on the seabed, with a leading end of the cable having a cable pull-in already part way inserted into the CPS, thereby protecting the cable end. A twin weak link system can then used to locate the CPS into the l-tube or J-tube, such as with a mechanical spring latch. With the CPS located to the foundation, the tension in a puling cable can be increased until the weak link is broken and then the load path changes from the CPS to the cable pull-in to allow it (and consequently the cable) to be pulled through the CPS and into the foundation. This too can be problematic since rigging inside the CPS can get caught as the internal surfaces of the CPS which are normally a series of corrugations, ribs, voids or the like.

[0018] If the CPS is pre-installed into foundation at sea there can be issues with damage to bell mouths or the bell mouth being obscured by sand waves. Typically a minimum of 2m clearance height is required to achieve a suitably large bend radius for the cable from the horizontal seabed to the vertical foundation, so that the minimum bend radius of the cable is not passed. [0019] The l-tube or J-tube thus provides protection for the cable and provides a defined path for the cable during at least a part of the transition of the cable from the seabed to the WTG.

[0020] In some conventional arrangements, a collection station or substation may require connection of multiple cables. Substations can have a foundation which is similar in construction to the foundation for a WTG. Thus the substation foundation can be required to carry a multiplicity of l-tubes or J-tubes in which the respective cables are routed. This can result in complex arrangements with difficulties in accessing individual l/J-tubes and associated cables.

[0021] Typically (but not essentially) an l/J-tube is attached to a foundation during an onshore manufacturing process of the foundation. The foundation with the attached l/J tube is transported from its onshore location of manufacture to its offshore location of use and mounted on the sea bed. Usually a portion of the foundation is arranged below the water surface and a portion thereof is arranged above the water surface. In some cases, the l-tube or J-tube can be present on a foundation in an offshore location for a

considerable period of time (such as several weeks or months or even years) before the cable is installed in the l-tube or J-tube. During this time the l-tube or J-tube can be subject to damage or decay or the ingress of foreign material which can hinder or prevent the passage of the cable through the l-tube of J-tube and which can necessitate a potentially expensive and time consuming repair.

[0022] Further, during the working life of an l/J tube corrosion or other damage may occur with the consequence that the useful lifetime of the l/J-tube may become less than that of the cable which it contains and/or less than that of the foundation on which the l/J- tube is mounted. For example, it is generally not possible to coat or paint the inside of the l/J-tube with a protective layer and so internal corrosion can lead to a shortening of the useful working life of the l/J-tube. It can thus be necessary to replace the l/J-tube which, in an offshore environment can be an inherently difficult and expensive operation.

[0023] Also, arrangements must be made by which the cable can be directed into the lowermost end of the l-tube or J-tube and subsequently be drawn through the l-tube or J- tube. Since the lowermost end of the l-tube or J-tube is beneath the water surface, underwater equipment is required for this operation.

[0024] In one typical arrangement, the l-tube or J-tube is provided with a messenger line which passes through the l-tube or J-tube. The messenger line is used to pull a cable (and a CPS) into and through the l/J-tube. An upper end of the messenger line can initially be secured proximate the upper end of the l-tube of J-tube. A lower end of the messenger line can pass through a closure bung at the lower end of the l/J-tube which bung is intended to prevent ingress of foreign material into the l/J-tube. The lower end of the messenger line is, when required, connected to the cable (and CPS) which is to be pulled into the l/J-tube. Often, the lower end of the messenger line is connected to a surface buoy until such time as it is required for pulling of the cable. In order to draw the cable through the l-tube or J-tube, the lower end of the messenger line must be retrieved and a connection made to the cable, this operation typically being carried out on a cable installation vessel (CIV). The upper end of the messenger line can be connected directly or indirectly to a high capacity winch provided on the WTG foundation which is used to draw the cable through the l-tube or J-tube. The provision of a high capacity winch on the WTG foundation, and its removal after cable installation, are difficult operations which may require multiple stages and several days of suitable weather and sea conditions.

[0025] A further problem with the installation of cables in l/J-tubes is control of the minimum bend radius in particular at the point of entry of the cable into the l/J-tube. The cable is paid out from the cable laying vessel and forms a catenary in the water, between the vessel and the point of entry of the cable into the l/J-tube. Careful control of the paying out of the cable and of the winch used for pulling the messenger line is required in order to ensure that the catenary curve is appropriate and that the minimum bend radius of the cable is not passed. Exceeding the minimum bend radius can cause significant damage to the cable, rendering a replacement necessary.

[0026] In some embodiments, the present invention seeks to provide an enhanced method and apparatus for securing a cable or other longitudinally extensive member to a foundation of an offshore structure such as a WTG foundation or an offshore substation foundation.

BRIEF SUM MARY OF THE DISCLOSURE

[0027] In accordance with a first aspect of the present invention there is provided an apparatus for installing and/or protectively securing a longitudinally extensive service member to an offshore structure, the apparatus comprising a flexible polymeric pipe or tube having a through bore configured to receive said longitudinally extensive service member, a first end and a second end, at least one securing device configured to secure a first portion of the polymeric pipe or tube including said first end to said offshore structure such that said first end is retained, when the offshore structure is in its position of use in use, above the water surface and at least one releasable securing device configured to releasably secure a second portion of the polymeric pipe or tube including said second end to said offshore structure such that said second end is releasably retained, when the offshore structure is in its position of use, above the water surface, said flexible polymeric pipe or tube having a length such that, on release of said second end from the releasable securing device, at least a part of said second portion including said second end can rest proximate or on the seabed.

[0028] In accordance with a second aspect of the present invention there is provided an offshore structure having mounted thereon an apparatus for installing and/or protectively securing a longitudinally extensive service member to said offshore structure the apparatus comprising a flexible polymeric pipe or tube having a through bore configured to receive said longitudinally extensive service member, a first end and a second end, at least one securing device by means of which a first portion of the polymeric pipe or tube including said first end is secured to said offshore structure such that said first end is retained, when the offshore structure is in its position of use in use, above the water surface and at least one releasable securing device by means of which a second portion of the polymeric pipe or tube including said second end is releasably secured to said offshore structure such that said second end is releasably retained, when the offshore structure is in its position of use, above the water surface, said flexible polymeric pipe or tube having a length such that, on release of said second end from the releasable securing device, at least a part of said second portion including said second end can rest proximate or on the seabed.

[0029] In accordance with a third aspect of the present invention there is provided an offshore structure having mounted thereon an apparatus which protectively secures a longitudinally extensive service member to said offshore structure, the apparatus comprising a flexible polymeric pipe or tube having a through bore in which said longitudinally extensive service member is received, a first end and a second end, at least one securing device by means of which a first portion of the polymeric pipe or tube including said first end is secured to said offshore structure such that said first end is retained above the water surface and wherein said flexible polymeric pipe or tube has a length such that, at least a part of said second portion including said second end rests proximate or on the seabed, the longitudinally extensive service member extending from said second end.

[0030] In some preferred embodiments said longitudinally extensive service member can be a cable for electricity transmission and/or a fibre optic cable.

[0031] In some preferred embodiments the offshore structure can be a foundation mounted to the seabed.

[0032] In some preferred embodiments the foundation can be a foundation of an offshore wind turbine generator or an offshore substation. [0033] In some preferred embodiments the foundation can be a jacket of lattice type construction.

[0034] In some preferred embodiments the flexible polymeric pipe or tube can be formed from a polymeric material selected from high density polyethylene (HDPE), high density polyethylene (HDPE) reinforced with fibres, cross-linked polyethylene (XLPE),

polypropylene and polyvinyl chloride or combinations thereof.

[0035] In some preferred embodiments the second portion of the polymeric pipe or tube can comprise a first portion and a second portion wherein the first portion has a greater axial stiffness and/or bending stiffness than the second portion.

[0036] In some preferred embodiments the flexible polymeric pipe or tube can be modular, comprising a plurality of conjoined pipe or tube sections.

[0037] According to a fourth aspect of the present invention there is provided an offshore structure comprising at least one releasable securing device in the form of an anchor assembly to releasably secure an end portion of a flexible pipe or tube to said offshore structure at a location above the water surface, said flexible pipe or tube having a length such that, on release of said end portion from the offshore structure, said end portion can rest proximate or on the seabed

wherein said anchor assembly comprises

a receiving portion attached to said offshore structure and a retaining pin configured to co- operate with the receiving portion thereby retaining said end portion of the flexible pipe or tube at its location above the water surface.

[0038] In some preferred embodiments of the fourth aspect of the invention, the offshore structure can comprise any feature or any permitted combination of features of the offshore structure described above in relation to the second aspect of the invention or the third aspect of the invention.

[0039] In some preferred embodiments said retaining pin can be substantially U-shaped and the receiving portion can comprise first and second sleeves to receive the retaining pin.

[0040] In some preferred embodiments of the fourth aspect of the invention, the offshore structure can be a foundation mounted to the seabed.

[0041] In some preferred embodiments of the fourth aspect of the invention, the foundation can be a foundation of an offshore wind turbine generator or an offshore substation. [0042] According to a fifth aspect of the present invention there is provided a method for installing a longitudinally extensive service member on an offshore structure including the steps of:

providing a flexible polymeric pipe or tube having a through bore configured to receive said longitudinally extensive service member;

securing a first end of said pipe or tube to the offshore structure at a location above the water surface;

releasably securing a second end of the pipe or tube to the offshore structure at a location above the water surface;

subsequently retrieving said second end and transferring said second end to a vessel, said pipe or tube thus extending from the offshore structure to the vessel; and

feeding the longitudinally extensive service member into the pipe or tube via said second end.

[0043] In some preferred embodiments said longitudinally extensive service member can be a cable for electricity transmission and/or a fibre optic cable.

[0044] In some preferred embodiments the offshore structure can be a foundation mounted to the seabed.

[0045] In some preferred embodiments the foundation can be a foundation of an offshore wind turbine generator or an offshore substation.

[0046] In some preferred embodiments the foundation can be a jacket of lattice type construction.

[0047] In some preferred embodiments the flexible polymeric pipe or tube can be formed from a polymeric material selected from high density polyethylene (HDPE), high density polyethylene (HDPE) reinforced with fibres, cross-linked polyethylene (XLPE),

polypropylene and polyvinyl chloride or combinations thereof.

[0048] In some preferred embodiments of the method the flexible polymeric pipe or tube can comprise a first portion and a second portion wherein the second portion includes said second end and wherein the first portion has a greater axial stiffness and/or bending stiffness than the second portion.

[0049] In some preferred embodiments the flexible polymeric pipe or tube can be modular, comprising a plurality of conjoined pipe or tube sections.

[0050] In some preferred embodiments the method can further include the step of providing a messenger line extending through the flexible polymeric pipe or tube. [0051] In some preferred embodiments the method can further comprise the steps of attaching a first end of the messenger line extending from the first end of the pipe or tube to a pulling apparatus mounted on the vessel or on the offshore structure, attaching a second end of the messenger line extending from the second end of the pipe or tube to the longitudinally extensive service member and using the pulling device to draw the longitudinally extensive service member through the pipe or tube.

[0052] In some preferred embodiments the method can further comprise the step of securing an end of the longitudinally extensive service member proximate said first end of the pipe or tube to the offshore structure and lowering said second end of the pipe or tube from the vessel to the seabed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Embodiments of the invention are further described hereinafter, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic side view of a typical offshore foundation including an apparatus according to the invention;

Figure 2 is a perspective view of the foundation and apparatus according to

Figure 1 ;

Figure 3 is a view of a foundation and apparatus similar to that of Figure 1 ;

Figure 4 shows the pipe or tube of an apparatus according to embodiments of the invention with the second portion in its first configuration;

Figure 5 shows an example of a suitable clamp arrangement for attaching a pipe or tube of the invention to an offshore foundation;

Figure 6 shows an offshore structure and an apparatus according to embodiments of the invention, with a cable installation vessel at an initial stage of a cable installation procedure;

Figure 7 shows the offshore structure, apparatus and vessel of Figure 6 during a process of insertion of a cable into the tube or pipe;

Figure 8 shows the offshore structure, apparatus and vessel of Figure 6 after a process of insertion of a cable into the tube or pipe;

Figure 9 shows the offshore structure and apparatus of Figure 6 with pipe or tube in its ultimate use condition; Figure 10A, 10B, 10C and 10D respectively show a first side view, second side view, plan view and a perspective view of an offshore structure according to another embodiment of the invention; and

Figure 11 shows the embodiment as illustrated in Figure 10D with a flexible polymeric pipe or tube passing therethrough and secured to its exterior.

DETAILED DESCRIPTION

[0054] Referring to the drawings, a typical offshore structure 200 is a foundation for a wind turbine generator, shown in part at 300. As illustrated, the foundation 202 can be a lattice type structure consisting of upright legs 204A, 204B, 204C and 204D and interconnecting braces or spars 206. Other types of foundation can alternatively be provided, such as a monopile or a gravity foundation.

[0055] The foundation 202 can mounted to the seabed 20 and can extend upwardly from the seabed 20 so that a portion of the foundation 202 is disposed above the water surface (indicated at 22). An uppermost part of the foundation 202 can define a platform region 208 onto which the wind turbine generator 300 can be mounted and which can provide an access location for operators required from time to time to work on the foundation 202.

[0056] Offshore foundations such as the foundation 202 are conventionally manufactured onshore and transported to and installed at their offshore site of use.

[0057] Figure 3 shows, for comparison only, two conventional J-tubes 400 arranged on the foundation 202 in an arrangement typical of an oil or gas installation.

[0058] Figures 1 to 3 illustrate schematically an apparatus 100 according to

embodiments of the invention. Figure 3 shows a foundation 202 having a first apparatus 100A and a second apparatus 100B. Multiple apparatus 100 may be provided on the same foundation 202 if required.

[0059] Apparatus 100 can include a longitudinally extensive protection apparatus in the form of a flexible pipe or tube 102 which can advantageously be formed from a polymeric material such as high density polyethylene (HDPE), polypropylene or polyvinyl chloride. Polymeric composite materials can also be used along with HDPE reinforced with fibres or thermoset materials such as cross-linked polyethylene (XPLE). In further embodiments the flexible pipe or tube 102 can be formed from two or more of any of the above-noted polymeric materials. Other polymeric materials such as polyurethane can be suitable, provided that the requirements flexibility and durability in an offshore environment are met. In some preferred arrangements the polymeric flexible pipe or tube can be formed by extrusion. [0060] Pipe or tube 102 can be provided as a single unitary component or can be of modular construction. Pipe or tube of modular construction can comprise multiple pipe sections joined by appropriate joining components to form a continuous pipe or tube 102. Modular construction can be advantageous where the larger diameter pipe or tube 102 is required, such as for diameters in excess of about 160 mm.

[0061] Longitudinally extensive protection apparatus 102 (that is, pipe or tube 102) can include a single through bore or a plurality of through bores contained within an outer bore. For example, a discrete through bore may be provided to accommodate a fibre optic cable.

[0062] The pipe or tube 102 can have a first end 104 and a second end 106. Further, the pipe or tube 102 can have a first portion 108 including the first end 104 which first portion 108 is secured in use to the foundation 202. In one preferred configuration, the first portion 108 extends along a linear path from an area proximate the top of the foundation 202 to an area proximate the seabed 20. The first end 104 of the first portion 108 can be disposed proximate the top of the platform 202, such as at or near to the platform region 208. The first end 104 can be disposed in a position which is above the water surface 22.

[0063] The first portion 108 is secured to the foundation 202 by one or more suitable securing devices 112 (not shown in Figure 1 and 2) such as clamps which attach to both the foundation 202 and the first portion 108 of the pipe or tube 102. The first portion 108 can be permanently secured to the foundation 202, in the sense that the first section 108 is intended to remain attached to the foundation 202 throughout the normal working life of the apparatus 100. Such permanent attachment can, if necessary, not preclude detaching the first section 108 from the foundation for maintenance of the foundation 202, the securing devices or the pipe or tube 102, with subsequent reattachment.

[0064] Figure 5 illustrates one example of a suitable clamping device 500 for securing the pipe or tube 102 to the foundation 202. Clamping device 500 can include a central section 501 which can cooperate with a second section 502 to define a passageway 504 which can accommodate a brace or spar 206 of foundation 202. Passageway 504 can be shaped and sized to conform to the shape and size of spar 206 and in the illustrated embodiment is generally cylindrical. Central section 501 and second section 502 can be secured together by bolts 507 or other suitable means which allow the respective sections 501 , 502 to be tightened (clamped) onto the spar 206. Clamping device 500 can further include a third section 503 which can cooperate with the central section 501 to define a further passageway 506 which can accommodate the pipe or tube 102. Passageway 506 can be shaped and sized to conform to the shape and size of pipe or tube 102 and in the illustrated embodiment is generally cylindrical. Central section 501 and third section 503 can be secured together by bolts 507 or other suitable means which allow the respective sections 501 , 502 to be tightened (clamped) onto the pipe or tube 102 sufficiently to secure the pipe or tube 102 in its desired position. In the illustrated embodiment of Figure 5, the axes of the passageways 504 and 506 are arranged orthogonally. Other respective orientations of the passageways 504, 506 can be selected in accordance with the respective orientations of the spar 206 to which the clamping device 500 is to be attached and of the pipe or tubel 02.

[0065] The pipe or tube 102 can have a second portion 110 extending from the second end 106 towards the first portion 108. The second portion 1 10 of the pipe or tube 102 can adopt different configurations at different times, in accordance with use requirements. Figures 1 to 4 show a second portion 1 10 of the same pipe or tube 102 in two such configurations.

[0066] In a first configuration, indicated generally at 110U, the second end 106 is disposed at a position above the water surface 22. In some preferred embodiments, the second portion 110U may be releasably secured to the foundation 202 at least at or near said second end 106. Suitable securing devices 114 such as releasable clamping arrangements can be used to releasably secure the second portion 110U at or proximate said second end 106 to the foundation 202. The second portion 110U can be releasably secured to the foundation in the sense that it can be securely attached to and retained on the foundation 202 for a period or weeks, months or more and can subsequently be detached from the foundation without significant difficulty.

[0067] In a second configuration, indicated generally at 1 10S, the second end 106 and at least a part of the second portion 110 can rest on, or proximate the seabed 20. If required, part of the second portion 1 10S may be buried in the seabed, for example to protect the second portion 11 OS from damage.

[0068] In its ultimately intended use condition, the pipe or tube 102, the second portion 110 adopts the second configuration as indicated by 1 1 OS. The pipe or tube 102 in the final use condition can thus extend from the seabed 20 to an upper part of the foundation 202, such as the platform region 208. The pipe or tube 102 contains in the final intended use condition a longitudinally extensive service member and provides protection from damage for the longitudinally extensive service member as the longitudinally extensive service member transitions from the seabed 20 to the top of the foundation 202. Thus the longitudinally extensive service member can extend through the whole length of the pipe or tube 102.

[0069] Alternative embodiments of the offshore structure are shown in Figures 10A, 10B, 10C, 10D and Figure 1 1. In these embodiments, the foundation for the offshore structure 600 can comprise a gravity foundation. A gravity foundation typically comprises a large mass of heavy material which is stably arranged in position on the seabed by virtue of its own weight. The gravity foundation 301 as illustrated in Figure 10A comprises a solid, massive block of material 336 which includes a through bore or passageway shown generally at 338. The passageway 338 can extend upwardly and internally within a portion of an apparatus 302 mounted on the gravity foundation 301. The apparatus 302 can be a wind turbine generator to which a longitudinally extensive service member is ultimately to be connected. A lower end 338L of the passageway 338 can open at a location proximate the seabed 20. A single foundation for the offshore structure 600 can include a plurality of passageways 338 (two such passageways are thus visible in Figures 10A, 10D and 11).

[0070] In some preferred embodiments passageway 338 can contain the first portion 108 of the polymeric pipe or tube 102. Passageway 338 can be formed from pipe or tube 102 which is shaped at least approximately to conform to the profile of the surface of the passageway 338. Pipe or tube 102 can be first secured in place (e.g. to the internal metalwork of the apparatus 302 by an appropriate clamping arrangement or the like) and its profile then cast into the apparatus. Typically, the first portion 108 of the pipe or tube 102 is thus permanently secured to the foundation 600 with its first end 104 positioned at an upper part of the foundation which part will, in use, be above the water surface. In one convenient arrangement, the polymeric pipe or tube 102 can be constrained at a given bend radius which is not less than a minimum bend radius and then concrete or other suitable material can be poured around the constrained pipe or tube 102 to form the foundation. In certain embodiments the minimum bend radius can be about 5m. The shape of the pipe or tube 102 thus becomes fixed in its desired position within the foundation. The second portion 110 of the pipe or tube 102 extends outwardly from an end 338L of the passageway 338.

[0071] In further embodiments the offshore structure 600 can comprise one or more anchor assemblies to releasably secure the second portion 110 of the pipe or tube 102 to the offshore structure 600. In preferred embodiments said one or more anchor assemblies releasably secure the second portion 1 10 including the second end 106 of the pipe or tube 102 to the offshore structure 600 such that said second end 106 is retained, when the offshore structure 600 is in its position of use, above the water surface. Thus in some embodiments the apparatus 302 mounted on the gravity foundation 301 can comprise said one or more anchor assemblies.

[0072] In further embodiments, the gravity foundation 301 can comprise said one or more anchor assemblies. In such embodiments said one or more anchors assemblies can be located at an external surface of the gravity foundation 301. In yet further preferred embodiments of the offshore structure 600, the gravity foundation 301 and the apparatus 302 can comprise said one or more anchor assemblies.

[0073] The inclusion of said anchor assemblies enable the second portion 1 10 of the flexible pipe or tube 102 to conveniently be secured or tethered to one or more portions of the foundation 600 so that the installation and/or protection system can remain in a pre- installed state indefinitely prior to receiving the longitudinally extensive service member for installation proximate or on the seabed.

[0074] The Figures illustrate a first anchor assembly 380A attached to an external surface of the apparatus 302 and a second anchor assembly 380B extending from an upper surface of the gravity foundation 301. Detail D of Figure 10D depicts an enlarged image of the anchor assembly 380A attached to the apparatus 302. The anchor assembly 380B located on the gravity foundation 301 is constructionally equivalent to 380A and thus will not be described further. The assembly 380A can comprise a retaining pin 384 and a receiving portion 382 configured to receive retaining pin 384. In some embodiments the retaining pin 384 is substantially U shaped. The retaining pin 384 can thus comprise first and second projections, 384A, 384B that can respectively enter and be retained within corresponding first and second sleeves, 383A, 383B of the receiving portion 382. In some embodiments the sleeves 383A, 383B and projections of the retaining pin 384A, 384B can be cylindrical.

[0075] The receiving portion 382 can conveniently be attached to the offshore structure 600 by one or more connecting members. Thus in Detail D of Figure 10D, the first sleeve 383A is attached to the apparatus 302 by a first connecting member 381A and the second sleeve 383B is attached to the apparatus 302 by a second connecting member 381 B. In some arrangements portions of the anchor assemblies 380A, and particularly the receiving portions 382, can be cast into the offshore structure 600. Thus anchor assembly 380A can be cast into a portion of the apparatus 302 and anchor assembly 380B can be cast into a portion of the gravity foundation 301.

[0076] The anchor assemblies 380A, 380B can comprise any material sufficiently strong to retain the second portion 1 10 of the pipe or tube 102 without damaging the pipe or tube 102. In some embodiments the receiving portion 382 and/or retaining pin 384 can be coated with polyurethane in order to reduce friction between the respective components. In other embodiments the receiving portion 382 and/or retaining pin 384 can be galvanised. In these embodiments the receiving portion 382 and/or retaining pin 384 can be subject to hot dip galvanisation. In further embodiments the receiving portion 382 and/or retaining pin 384 can be coated with a protective paint suitable for the marine environment. Appropriate coatings to meet these criteria are well known to those skilled in the art and include, for example, the NORSOK marine protection system.

[0077] Figure 11 shows the offshore structure 600 with the second portion 1 10 of the pipe or tube 102 secured thereto. The second portion 110 of the pipe or tube 102 can be secured in position by first placing the pipe or tube between the two sleeves 383A, 383B and then appropriately seating the retaining pin 384 in the sleeves 383A, 383B. As shown in Figure 11 , a first, lower portion of the second portion 110 of the pipe or tube is secured to the gravity foundation 301 and a second, upper portion of the second portion 1 10 of the pipe or tube including second end 106 is secured to the apparatus 302.

[0078] In some embodiments of the invention the length of the pipe or tube 102 can be at least 10m. The maximum length may not be constrained, however, in embodiments of the invention wherein the foundation is of lattice type, the maximum length of the pipe or tube 102 is typically up to 150m.

[0079] The internal diameter of the pipe or tube 102 is selected in accordance with the diameter of the longitudinally extensive service member, that is, to enable feeding of the longitudinally extensive service member through the pipe or tube 102. In some

embodiments, the internal diameter of the pipe or tube 102 is at least 150mm. In further embodiments the internal diameter of the pipe or tube 102 is not greater than 500mm. In some embodiments the pipe or tube 102 can comprise walls having a thickness of from 10mm up to 100mm.

[0080] In some embodiments the second portion 1 10 of the pipe or tube 102 can comprise a first portion and a second portion wherein the first portion has a greater axial stiffness and/or bending stiffness than the second portion. The first portion of greater axial stiffness and/or bending stiffness can include regions of the pipe or tube 102 at or proximate the surface wave zone (i.e. regions at or near to the water surface 22 as shown in Figure 1). In these embodiments said first portion can exhibit axial stiffness and/or bending stiffness typically 20 to 50 times the axial stiffness and/or bending stiffness of the longitudinally extensive service member. Such embodiments can provide fatigue protection over a 25 year period (a typical period for which the longitudinally service member may be in use). The second portion of lesser axial stiffness and/or bending stiffness than the first portion can include regions of the pipe or tube 102 below the surface wave zone. Comparatively, said second portion can exhibit axial stiffness and/or bending stiffness typically in the range of 10 to 20 times the axial stiffness and/or bending stiffness of the longitudinally extensive service member. Thus, as the first portion will typically be subjected to enhanced wave action and increased transverse forces when compared to the second portion, the axial stiffness and/or bending stiffness of the first portion can advantageously be increased to resist such stresses. The properties of the second portion provide suitable fatigue protection over the 25 year period and are appropriate for the ultimate limit state during the installation and operation of the longitudinally extensive service member.

[0081] The above-mentioned first portion and second portions of the second portion 110 of the pipe or tube 102 can thus respectively be formed from different polymeric materials to provide the requisite axial stiffness and/or bending stiffness. For example, the first portion of the second portion 1 10 of the pipe or tube 102 can be formed from a polymeric composite such as HDPE reinforced with fibres or a thermosetting material such as XLPE. The second portion of the second portion 110 of the pipe or tube 102 can be formed from a thermoplastic polymer such as HDPE or a material with similar properties to HDPE. In some embodiments butt welding can be used to join the first and second portions to form a continuous tube or pipe. Alternatively, pre-determined lengths of the tube or pipe can be connected together to form the aforementioned first and second portions and ultimately construct the second portion 1 10 of the pipe or tube 102 using mechanical fixings such as bolts and flanges.

[0082] In some preferred embodiments the longitudinally extensive service member which extends through the longitudinally extensive protection apparatus (pipe or tube 102) can be a cable such as an electricity transmission cable and/or a fibre optic cable. In some preferred embodiments, the foundation is a foundation of a wind turbine generator or an offshore substation and the cable connects at one end to the wind turbine generator or substation.

[0083] In other embodiments the longitudinally extensive service member can be a cable which connects to an offshore oil or gas installation.

[0084] In other embodiments the longitudinally extensive service member can be a pipe for transmission of fluid such as oil, gas or other production fluids associated with offshore oil and gas extraction processes.

[0085] In some preferred embodiments, the pipe or tube 102 can be fitted to or attached to the offshore foundation 202 as a part of the process of onshore manufacture of the offshore foundation. The fitting of the pipe or tube 102 is such that it adopts the first configuration, that is, with a first portion 108 permanently secured to the foundation 202 with the first end 104 positioned at an upper part of the foundation 202 which part will, in use, be above the water surface 22 and the second portion 110 releasably secured to the foundation 202 with the second end 106 releasably positioned at an upper part of the foundation 202 which part will, in use, be above the water surface 22. A messenger line 116 may be disposed within the pipe or tube 102 before, or at the time of, manufacture of the foundation 202 and fitting of the pipe or tube 102 to the foundation 202. [0086] Thus, in some preferred embodiments of the invention, the foundation 202 can be transported to its offshore site of use and mounted at that site in its use position with the apparatus 100 mounted thereon, the second portion 110 of the pipe or tube 102 being in the first configuration 110U. The apparatus 100 can maintain this state in the offshore location for a considerable period of time, such as weeks, months or even years before its next stage of use. For example after placing of the foundation 202 in its use position, there may be a delay before equipment (such as a wind turbine generator) is mounted to the foundation. During this time, the respective ends of the pipe or tube 102 may be closed by suitable removeable closure devices to prevent or minimise the ingress of seawater or other foreign material into the interior bore or passageway of the pipe or tube 102. Of course, the location of the respective ends 104, 106 above the water surface level is advantageous in preventing ingress of sea water or other foreign material to the interior of the pipe or tube 102.

[0087] In some circumstances, it can be desirable to retro-fit an apparatus 100 to a foundation 202, that is, to mount the apparatus on the foundation 202 when the foundation 202 is in its offshore location of use. For example, the apparatus 100 can be used to replace an existing l-tube or J-tube which is no longer serviceable. In such embodiments the pipe or tube 102 can be fitted, where necessary with the assistance of divers or (more preferably) an ROV, so that the first portion 108 is permanently secured to the foundation 202 with first end 104 above the sea level 22, with the first portion extending downwardly towards the seabed 20 and with the second portion 1 10 in the first configuration 1 10U. Again, the apparatus 100 can maintain this state in the offshore location for a considerable period of time, such as weeks, months or even years before its next stage of use.

[0088] Fitting or insertion of the longitudinally extensive service member into the pipe or tube 102 is described with particular reference to Figures 6 to 9.

[0089] Thus, for insertion of a cable or other longitudinally extensive service member into the pipe or tube 102, the first portion 108 can be secured to the foundation 202 with the first end maintained above the water surface 22 and the first portion extending towards the seabed. The second portion 108 can be releasably secured to the foundation 202 and the second end can be releasably held attached to the foundation 202 at a location above the water surface 22. The pipe or tube 102 can have provided therein (on manufacture of the offshore structure or subsequently) a messenger line 116, first and second ends of which can be retrieved from the respective first and second ends 104, 106 of the of the pipe or tube 102.

[0090] For installation of the cable 602, a cable installation vessel (CIV) 604 can approach the foundation 202. A first portion 1 16A of the messenger line 116 can be retrieved from the first end 104 of the pipe or tube 102 and taken on board the CIV 604. A first end of the messenger line 1 16 can be attached to a winch or other suitable pulling device 606 mounted on the CIV 604.

[0091] In a variation, the winch or other suitable pulling device can be located on the offshore foundation 202. This is possible because the pulling force required to pull the longitudinally extensive service member through the apparatus 100 is significantly smaller than required in the prior art where l-and J-tubes are used. Hence a smaller winch or pulling device can be accommodated on the offshore structure, in contrast to the high power pulling device previously required.

[0092] A second portion 116B of the messenger line 116 can be retrieved from the second end 106 of the pipe or tube 102 (Figure 6). The second portion 110 of the pipe or tube 102, including the second end 106 can be released from its securing to the foundation 202 and taken on board the CIV (Figure 7). A second end of the messenger 1 16 line can be attached to a cable (or other longitudinally extensive service member as appropriate) for installation of the cable 602 into the pipe or tube 102 of the apparatus 100. The cable 602 can in some preferred embodiments include a pulling head (not illustrated) to which the messenger line is attached.

[0093] The winch 606 on the CIV 604 can be used to draw in the messenger line 1 16. Since the messenger line 116 is attached at its second end to the cable 602, the cable is paid out from the CIV and pulled by the winch 606 (by virtue of the messenger line 1 16) into and through the pipe or tube 102. Pulling of the cable 602 can continue until the leading end of the cable (which can be the pulling head) reaches a desired predetermined location at which it is secured. The predetermined location can be, for example, proximate a platform region 208 of the foundation 202.

[0094] Messenger line 116 can then be detached from the leading end (or pulling head) of the cable 602 and can be taken aboard the CIV. Paying out of the cable 602 from the CIV can continue as the CIV moves away from the foundation 202 (Figure 8). The second portion 1 10 of the pipe or tube 102 can then adopt its second configuration 11 OS in which it lies on (or may be buried under) the seabed 20 (Figure 9). In some embodiments weights of suitable construction can be placed over the pipe or tube 102 or over the cable 602 extending from the pipe or tube 102 to hold the same in a desired location.

[0095] A particular advantage of the apparatus of the present invention is that the pipe or tube 102 offers significantly less resistance to the pulling through of the cable 602 than would a comparable l-tube or J-tube. Consequently, a relatively low capacity winch onboard the CIV or on the offshore structure can be used for pulling of the cable, in contrast to the high capacity winch which must be mounted on the foundation which is required when using an l-tube or J-tube. The pipe or tube 102 presents a smooth and entirely unobstructed internal surface which reduces the pulling resistance for passage of the longitudinally extensive service member through the pipe or tube 102, as compared with prior art apparatus, and also prevents snagging of the longitudinally extensive service member on any interior part. Snagging is a significant disadvantage of prior art techniques, potentially requiring provision of a replacement cable.

[0096] Further advantageously, the danger of bending the cable 602 beyond its minimum bend radius is significantly reduced or eliminated. The pinch point at the mouth of an I- tube or J-tube is no longer present and the flexible nature of the pipe or tube 102 means that the pipe or tube can bend to accommodate the line of approach to the mouth of the pipe or tube 102 of the cable 602.

[0097] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0098] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0099] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.