GB2585481A

GB2585481A - Load sharing bearing

Info

Publication number: GB2585481A
Application number: GB2007021.5A
Authority: GB
Inventors: Fernandes Martins Miguel; P Cruse Gregory
Original assignee: Oil States Industries UK Ltd
Current assignee: Oil States Industries UK Ltd
Priority date: 2019-05-13
Filing date: 2020-05-13
Publication date: 2021-01-13
Also published as: WO2020229817A1; GB201906737D0; GB202007021D0

Abstract

A load sharing component 200 is for mounting between an auxiliary line component such as a choke line 125 or kill line 130 and a tubular such as a riser or landing string to reduce the self-weight loading on the tubular allowing reductions in wall thickness and weight with associated handling benefits. The load sharing component comprises a resilient bearing member 201 which may be of steel plates alternating or embedded in an elastomer or may be a concertina walled ring. The component may encircle the, or each, auxiliary line and transfer load between a tubular flange 150 and an auxiliary line loading flange 70 or may encircle the whole tubular. The load sharing component is configured to afford limited resilient deformation in an axial direction of the tubular and to resist deformation in a radial direction of the tubular. To account for fabrication tolerance loading there may be a pre-tensioning element 202 comprising an elastomeric member 95 of lower stiffness than the main component between first and second clamping elements 205, 206 which come together when assembled.

Description

LOAD SHARING BEARING

This invention relates to load sharing between components in a riser, and particularly load sharing between components in a marine riser for use in the exploration of and recovery of hydrocarbons such as oil and gas, particularly from subsea reservoirs.

The invention is primarily focussed on the sharing of loads between the main riser barrel and auxiliary lines connected to the main riser barrel, such as choke and kill lines.

A riser may be used in the exploration for or production of hydrocarbons to provide a pathway for drilling and evaluation tools and equipment to be lowered into the well, and for hydrocarbons to travel between a subsea reservoir and a surface production vessel such as a floating production storage and offloading vessel (FPSO) or a floating or semi-submersible platform. The riser is formed of a plurality or string of riser joints connected end to end and extending between the sea bed and the surface.

Typically, each riser joint will comprise means for securely connecting it to a subsequent riser joint. This may be a pin and box screw thread arrangement or alternatively each riser joint may be provided with a radially projecting flange at each end of the joint. The flange will typically include apertures to allow fixing means to pass through the cooperating flange of an adjacent riser section to secure the riser sections together i.e. thus forming the riser string.

As the platform or floating production vessel is floating at the surface, the position of the platform is affected by local conditions such as wind, sea swell and the like. Any movement of the floating platform (i.e. pitch, roll, heave, sway or surge) may affect the distance between the two points at which is riser string is fixed -i.e. at both ends of the riser string. In this regard, the riser string must be able to accommodate changes in its own length. Flex joints may be provided between adjacent riser sections in order to accommodate the change in length of the riser string as the platform moves in any direction on the surface of the sea. Furthermore, a telescopic section may be provided between the platform and the top of the riser string which allows the effective length of the riser string to change with changes to the position of the platform. In addition to being able to supress the effects of the changes in length of the riser string, the riser string must also be able to support its own weight and carry large loads through the string, particularly in deep-water operations.

Each riser section must resist the pressure of the material within the riser (i.e. returning drilling mud or flowing hydrocarbons for example) but also the tensile load which is caused by the suspension of riser sections from that section. This tensile load is typically high and requires that each tubular riser section has thick metal walls and substantial flanges at each end to accommodate the tensile induced loads.

Thick walled tubulars are highly undesirable for a number of reasons. Primarily, they are costly to manufacture, heavy to transport and lift, and their weight further adds to the weight which must be carried by riser sections higher in the string. In deep-water operations (generally considered water depths of 1000ft (305m) or more) and particularly in ultra deep-water operations (around 5000ft (1524m) or more), the cumulative weight build-up is significant over the whole length of the riser string.

The riser string is subject to tensile loads due to the hanging of the riser string from the vessel. However, it can also be subject to compressive loads, particularly when the riser string lands out on the connection to the wellhead at the seabed. It must therefore be designed to be able to withstand high tensile and high compressive loads.

In this connection, marine riser tensioners are known and provide a near constant upward force on the riser string independent of the upward and downward movement of the floating vessel. A marine riser tensioner is typically connected to the wellhead on the seabed and must manage the differential movement between the riser and the vessel. A lack of upward tensioning when the vessel moves downward would cause the riser to buckle, which is highly undesirable for many operational and safety reasons, and is widely accepted in the industry as a highly undesirable event.

Marine riser tensioners typically use hydraulic systems, usually consisting of hydraulic cylinders, sheaves and strong wire rope, however alternative riser tensioning systems have been developed which use elastomeric elements instead of hydraulics. One such example is described in US patent 4,729,694 which describes a tension leg platform marine riser tensioner. In the system disclosed in US4,729,694, the riser tensioner includes an elastomeric assembly interconnecting the tension leg platform and the riser to maintain tension in the riser as the tension leg platform moves relative to the riser. The elastomeric assembly includes a first plate assembly which is secured to the tension leg platform and a second plate assembly which is secured to the riser. An elastomeric pad assembly is bonded between the first and second plate assemblies to be put in shear to tension the riser. The elastomeric pad assembly includes elastomeric pads separated by rigid plates.

In a typical subsea system, the riser string connects to a blowout preventer which is located at the top of a well being drilled, or to a Christmas tree in a producing well. Blowout preventers and Christmas trees are arrangements of large valves which are operated to close the well, should control of the well be lost, usually due to a kick (an increase in pressure caused by the formation). The BOP and Christmas trees have choke valves which are used to safely release high pressure from the well, and kill valves which are used to deliver dense drilling mud to the well to balance the high pressure. Choke and kill lines run from the choke valve and kill valve on the BOP or Christmas tree to the vessel at the surface, typically along the outside of the riser.

By coupling one or more of the auxiliary lines to the main riser, a certain amount of load sharing may be achieved, reducing the loads that the main riser has to bear. This will however be governed by the cross-section of the main barrel and choke and kill lines. Existing arrangements for coupling the riser and auxiliary components together hence have limited functionality in terms of optimising the distribution of loads between the components.

The present invention seeks to provide a load sharing component and assembly that optimises performance compared with known arrangements.

According to an aspect of the invention, there is provided a load sharing component for mounting between an auxiliary line component and a tubular, the load sharing component comprising a resilient bearing member. The use of a resilient bearing member allows loads to be transferred between the auxiliary line and the tubular, thereby reducing the load carrying requirements of the tubular.

Conveniently, the tubular may be a riser or landing string. Risers and landing strings can be costly to manufacture, heavy to transport and lift, their weight adding to the weight which must be carried by riser sections higher in the string. It is advantageous therefore to share the load applied to a riser or landing string by way of a load sharing bearing to an auxiliary component. Advantageously, this can allow the riser or landing string to be made from thinner walled tubulars which has many advantages, including for example, reduced cost of manufacture, safer handling and lower weight rated handling tools.

Preferably, when in use, the resilient bearing member may be configured to afford limited resilient deformation in an axial direction of the tubular and to resist deformation in a radial direction of the tubular. In this way, the resilient bearing member will resist radial deformation that may urge it to buckle radially outwards rather than carry the axial load axially, resulting in a non-linear deformation.

Preferably, the load sharing component may be configured for mounting at the interface between an auxiliary load sharing member of an auxiliary line component, such as a rod, choke or kill line, and a flange of a tubular section. This arrangement allows an axial load transferred through the tubular to be shared, such that the total axial load through the tubular is reduced. The resulting tubular can be cheaper to manufacture and easier to handle as it can be lighter due to the reduced wall thickness required, as it does not need to carry such high loads.

Where a number of auxiliary line components are disposed around the tubular, one or more of them may each be provided with such a load sharing component.

Alternatively, the load sharing component may be provided as a single entity surrounding the tubular and having a resilient bearing member for coupling one or more of the auxiliary line components.

Optionally, the resilient bearing member may be profiled to afford axial compressibility and radial stiffness. As such, the resilient bearing member may be formed of a ring whose wall has an undulating concertina-like profile. The resilient bearing member may as such be formed from a single material.

Preferably, the resilient bearing member may be formed of at least one rigid element and at least one elastomeric element. This provides a resilient bearing member which is able to resiliently deform in the axial direction, but resist deformation in the radial direction. This allows the resilient bearing member to be able to carry loads in the axial direction without buckling or deforming in the radial direction, and thus the resilient bearing member is able to share the load applied to the tubular.

Preferably, the resilient bearing member may be formed of a plurality of rigid elements and at least one elastomeric element. A plurality of rigid elements provides rigidity in the radial direction, whilst the at least one elastomeric element allows deformation and flexibility in the axial direction. Thus the resilient bearing member is adapted to carry the axial load and resist radial deformation.

Optionally, the resilient bearing member may be made up of stacked and bonded alternated layers of rigid elements and elastomer elements. Alternatively, the rigid elements may be embedded in elastomeric material.

Preferably, where multiple rigid elements are present, they are separated along the axial direction by elastomeric material of the at least one elastomeric element. The separation of the plurality of rigid elements by elastomeric material of the elastomeric element allows the resilient bearing member to have a very high stiffness in the radial direction, and a lower stiffness in the axial direction. This allows the resilient bearing member to deform axially when a load is applied to it in the axial direction, whilst resisting radial deformation.

Preferably, the elastomeric element is provided in the form of elastomeric discs bonded to the rigid elements.

Conveniently, the resilient bearing member has an annular form, with the plurality of rigid elements taking the form of a plurality of shims, spaced from one another by elastomeric material. Preferably, the elastomeric material is in the form of a plurality of elastomeric shims This provides the preferably stacked configuration which has the advantage of a high radial stiffness and a lower axial stiffness.

Preferably, the load sharing component further comprises a pre-tensioning element. Conveniently, the pre-tensioning element is disposed between the resilient bearing member and the tubular. The pre-tensioning element may further be positioned directly adjacent the resilient bearing member. Alternatively, the pre-tensioning element may be provided between the auxiliary line component and the resilient bearing member.

The pre-tensioning element provides the ability to preload the assembly comprising the tubular, auxiliary components and load sharing component during assembly.

Preferably, the pre-tensioning element may comprise an elastomeric member. This allows the pre-tensioning element to absorb first, lower, axial loads which are applied to take up the fabrication tolerances in the tubulars during make-up of the tubular from tubular sections. Furthermore, this allows the establishment of a controlled and tuneable load sharing path through the flanges of the tubular and thereafter through the resilient bearing member, as the stiffness of the elastomer can be selected accordingly, and furthermore the fabrication tolerances in the tubular can be taken up gradually as required.

Preferably, the pre-tensioning element has a lower axial stiffness than the resilient bearing member. This means that the elastomeric member absorbs the load applied when the fabrication tolerances are taken up during the make-up of the tubular. It also ensures that the force needed to take up the fabrication tolerances is sufficiently small such that it can be applied externally during make-up.

Preferably, the elastomeric member is arranged between a first clamp member of the pre-tensioning element and a second clamp member of the pre-tensioning element. This provides a system whereby the first and second clamp members can be brought together in a controlled manner to deform the elastomeric member.

Preferably, the pre-tensioning element and resilient bearing member may be arranged such that in use the elastomeric member in the pre-tensioning element can be compressed axially, a pre-determined distance, until the first clamp member and second clamp member touch. Furthermore, in use an axial load may cause deformation of the elastomeric member until the first clamp member and second clamp member touch. This allows the pre-determined distance to be set for the particular application of the invention.

Preferably, after the first and second clamp members touch, the application of further axial load is transferred to the resilient bearing member, with the elastomeric member inside the pre-tensioning element receiving no further axial load, thus ensuring that the higher stiffness element is receiving the axial load.

Preferably, the resilient bearing member is annular or ring shaped to allow an auxiliary component to pass there-through. This allows a convenient mounting of the resilient bearing member, as it can be mounted around already existing tubular components such as rods, or choke and kill lines which typically pass up the sides of a subsea riser.

Preferably, the at least one rigid element may comprise steel. Steel is a suitable material for a rigid element as it has a high stiffness compared to the elastomer. Conveniently, in contrast, the elastomeric element and elastomeric member may comprise nitrile and/or natural rubber and/or polyurethane, which provides the required flexibility for these elements.

Conveniently, the resilient bearing member may surround the tubular, rather than surrounding an auxiliary line. In this regard, the resilient bearing member may surround the tubular entirely or partially, and this may be easier to manufacture or install.

According to a further aspect of the present invention there is provided a pre-tensioning element for use in the load sharing component as defined above, the pre-tensioning element comprising a pair of annular clamp members housing an elastomeric annular member there-between.

Preferably, the clamp members each comprise an annular groove for seating the elastomeric member, the groove being profiled to accommodate deformation of the elastomeric member.

The accompanying drawings illustrate presently exemplary embodiments of the disclosure and together with the general description given above and the detailed description of the embodiments given below, serve to explain, by way of example, the principles of the disclosure.

The drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments of the present invention are shown in the drawings and herein will be described in detail, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognised that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce the desired results.

Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention.

Features and advantages of the present invention are readily apparent from the entire description thereof, including the figures, which illustrates a number of exemplary embodiments and implementations. The invention is also capable of other and different embodiments and aspects and its several details can be modified in various respects, all without departing from the scope of the present invention.

Accordingly, the drawings and descriptions are to be regarded as illustrative in nature and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including", "comprising", "having", "containing" or "involving" and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents and additional subject matter not recited and is not intended to exclude other additives, components, integers or steps. In this disclosure, whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition, element or group of elements with transitional phrases "consisting essentially of', "consisting", "selected from the group of consisting of', "including" or "is" preceding the recitation of the composition, element or group of elements and vice versa. In this disclosure, the words "typically" or "optionally" are to be understood as being intended to indicate optional or non-essential features of the invention which are present in certain examples but which can be omitted in others without departing from the scope of the invention.

All numerical values in this disclosure are understood as being modified by "about". All singular forms of elements, or any other components described herein including (without limitations) components of the assembly are understood to include plural forms thereof and vice.

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a prior art riser system comprising a lower riser section and an upper riser section, together making a riser main barrel, and further comprising a choke line and a kill line; Figure 2a shows a lower riser section assembled with a load sharing component comprising a resilient bearing member and a pre-tensioning element in accordance with the present invention; Figure 2b shows an upper riser section for assembly with the lower riser section and load sharing component shown in Figure 2a; Figure 2c shows a riser system comprising the lower riser section and load sharing component shown in Figure 2a connected to the upper riser section shown in Figure 2b; Figure 3 shows a cross-sectional view of a riser system comprising a lower riser section, an upper riser section, radially projecting flanges from the upper and lower riser sections, choke and kill lines and load sharing components in accordance with the present invention; Figure 4 shows one of the load sharing components shown in Figure 3 and comprises a pre-tensioning element and a load bearing member in accordance with the present invention; Figure 5 shows a Force versus Displacement curve produced by finite element analysis modelling of a load bearing member according to the present invention positioned between a choke and kill line and the riser main barrel; and Figure 6 shows a further embodiment of a resilient bearing member according to the present invention.

Turning now to the drawings, there is shown in Figure 1 a prior art riser system connection 5 (developed by Oil States Industries and branded OR-6C Connector) comprising a lower riser section 10 and an upper riser section 15 together making a riser main barrel 20, a choke line 25 and a kill line 30. Direction A is upward towards the surface and B is downwards towards the seabed.

The lower riser section 10 has an upstanding pin end 35 which mates with a box end 40 of the upper riser section 15. The upper riser section 15 has a first radially projecting flange 45 and the lower riser section 10 has a second radially projecting flange 50. The first and second radially projecting flanges 45, 50 aid handling of the lower and upper riser sections 10, 15 and provide lateral stability to the choke and kill lines 25, 30 as they connect the vessel on the surface to the wellhead located at the seabed. In this prior art example, the riser main barrel 20 must be of a sufficient thickness such that it can carry the applied tensile and compressive loads.

Figures 2a, 2b and 2c show an embodiment of a riser system 105 in accordance with the present invention. The riser system 105 is for transferring fluids to and from a well, with the additional advantage of a load sharing capability, wherein loads are shared across components of the system 105, as will now be described. Figure 2a and Figure 2b show a lower riser section 110 and an upper riser section 115, which can be assembled to form the riser system 105 shown in Figure 2c.

The riser system 105 includes a choke line 125, a kill line 130, and a riser main barrel 120. The riser main barrel 120 is made up of the lower riser section 110 and the upper riser section 115. The riser main barrel 120 is configured to securely attach to additional riser sections positioned above and below the upper riser section and lower riser section 110, respectively, in the known manner of assembling a riser string.

In this regard, the lower riser section 110 has a first box connection 140 at its upper end and a first pin connection (not shown) at its lower end. Similarly, the upper riser section 115 has a box connection (not shown) at its upper end, and a pin connection 135 at its lower end. Furthermore, the upper riser section 115 comprises a first radially projecting flange 145 and the lower riser section 110 comprises a second radially projecting flange 150. Flanges 145, 150 each comprise an aperture through which the choke line 125 passes, and an aperture through which the kill line 130 passes. The choke line 125 is fixedly attached to the first radially projecting flange 145 by a first fixation. Similarly, the kill line 130 is fixedly attached to the first radially projecting flange 145 by a second fixation. The choke line 125 and kill line 130 carry fluids at higher pressures to those experienced by the fluid within the riser main barrel 120.

Whilst the pin and box connections are shown in a particular orientation in relation to the orientation of the riser in use, their orientation may equally be reversed.

Referring to Figures 3 and 4, the riser system 105 further comprises a number of load sharing components 200. Each load sharing component is provided in the form of a resilient bearing member 201 and a pre-tensioner 202.

One of said load sharing components 200 is located between a first loading flange 70 of the choke line 125 and the second radially projecting flange 150. The riser system 105 further comprises a further load sharing component 200 located between a loading flange 80 of the kill line 130 and the second radially projecting flange 150.

The load sharing components 200 will now be described further.

Figure 4 shows the load sharing bearing 201 and pre-tensioner 202 of the load sharing component in greater detail. The load sharing bearing 201 and pre-tensioner 202 are toroidal with a central passageway through which one of the choke or kill lines passes. The first load sharing bearing 201 comprises a series of shims 85 set within an elastomeric element 90. The shims 85 are rigid steel washers which are arranged in a stacked configuration, with the elastomeric material 90 separating each shim 85. To maximise the radial rigidity, the shims 85 are each arranged to lie normal to the axial direction. This arrangement provides the required flexibility in the axial direction whilst maintaining rigidity in the radial direction. Having some flexibility in the axial direction allows the first load sharing bearing 201 to absorb an applied load by resiliently deforming in the axial direction. Although steel shims 85 are used, any suitable material which is sufficiently rigid may be used.

In this regard, rather than comprising a series of parallel metal shims set in elastomeric material, the resilient bearing can in this connection take the form of a stack of alternating metal shims and elastomeric shims, bonded together at their interface.

As shown in Figure 4, the load sharing bearing 201 is fixedly attached to the pre-tensioner 202. In this connection, the pre-tensioner 202 comprises an elastomeric member 95 arranged between a first clamping element 205 and a second clamping element 206. The elastomeric member 95 is resiliently deformable and of a lower stiffness than the elastomeric element 85. The elastomeric member 95 can be compressed such that the first and second clamping elements come together. The advantages of this arrangement will now be shown through a summary of the main stages of assembly of the first load sharing component 200 within the riser system 105.

During make-up of the riser system 105, one of the load sharing components 200 is located between the first loading flange 70 of the choke line 125 and the first radially projecting flange 150. The choke line can be pre-tensioned by closing the gap between the first clamping element 205 and the second clamping element 206, to thereby compress the elastomeric member 95. Once the first clamping element 205 and second clamping element 206 are touching, further applied load is transferred to the resilient bearing member 201. The resilient bearing member 201 will deform axially in a limited fashion, but radial deformation will be resisted by the rigid shims 85 disposed in the elastomeric element 90.

The load sharing component 200 is hence capable of sharing an axial tensile load or axial compressive load applied to the riser main barrel 120. Whilst in the described embodiments choke and kill lines are used, it will be appreciated that any auxiliary lines or components could be used with the present invention. Furthermore, the invention has been described in the context of a subsea riser system, however other applications are within the scope of the invention, including, but not limited to, landing strings.

Furthermore, whilst in the above embodiment the resilient bearing comprises a formation having a laminated array of rigid and elastomeric elements, in an alternative configuration shown in Figure 6, the bearing 201 may comprise a ring 300 having an undulating concertina-like cross-sectional wall profile to provide the required stiffness variation. The concertina-like ring may be formed of one material, relying on the profile rather than different materials, to provide the different radial and axial stiffness.

Furthermore, the invention has been described above in the context of each resilient bearing member surrounding an auxiliary line. However, it will be appreciated that the load sharing component may comprise a single resilient bearing member that surrounds or is distributed around the tubular and be configured to interface with one or more of the auxiliary lines.

It will be appreciated that whilst the load sharing component has been described in relation particularly to the coupling with the choke line 125, the arrangement will be highly similar in relation to coupling with the kill line 130, though elements may be altered to accommodate different characteristics of the choke and kill lines.

The expected operations parameters are now discussed with reference to Figure 5, which shows a Force versus Displacement curve produced by finite element analysis modelling of one load bearing member positioned between the choke and kill line and the riser main barrel. It can be seen in Figure 5 that around 200,000lb (900000 N) of force produces around 1" (2.54cm) displacement (compression), and around 1,000,000lb of force produces around 1.5" (3.81cm) of displacement (compression). This displacement is acceptable considering the length changes that occur when the main riser and auxiliary lines are subject to pre-tension, top tension, temperature differences and internal pressure.

Similarly, it has been calculated from analysis of a drilling riser that the gap between the first clamp element and the second clamp element could be around 0.6" (1.52cm), for example. These figures are purely for example, and may vary greatly across various applications.

Modifications and improvements may be made to the embodiments herein before described without departing from the scope of the invention.

Additional components and equipment can be added to embodiments of the invention as required such as landing strings, riser tensioners, heave compensation systems etc. without departing from the present invention.

Claims

Claims 1. A load sharing component for mounting between an auxiliary line component and a tubular, the load sharing component comprising a resilient bearing member.
2. The load sharing component of claim 1, wherein the tubular is a riser or landing string.
3. The load sharing component of claim 1 or 2, wherein the resilient bearing member in use is configured to afford limited resilient deformation in an axial direction of the tubular and to resist deformation in a radial direction of the tubular.
4. The load sharing component of any preceding claim, wherein the load sharing component is configured for mounting at the interface between an auxiliary load sharing member of an auxiliary line component, selected from one or more of a rod, choke or kill line, and a flange of a tubular section.
5. The load sharing component of any preceding claim, wherein the resilient bearing member is formed of at least one rigid element and at least one elastomeric element.
6. The load sharing component of claim 5, wherein the resilient bearing member is formed of a plurality of rigid elements separated along the axial direction by elastomeric material of the at least one elastomeric element.
7. The load sharing component of claim 6, comprising a stack of alternating rigid element shims and elastomeric shims bonded together.
8. The load sharing component of any one of claims 6 or 7, wherein the plurality of rigid elements are arranged to lie normally relative to the tubular axis.
9. The load sharing component of any one of claims 6 to 8, wherein the resilient bearing member has an annular form.
10. The load sharing component of claims 7, wherein the rigid element and elastomeric shims have a common inner and outer diameter.
11. The load sharing component of any preceding claim, wherein a dedicated resilient bearing member is provided to each auxiliary line component.
12. The load sharing component of any one of claims 1 to 10, wherein the resilient bearing member is shared between a number of auxiliary line components.
13. The load sharing component of any preceding claim, further comprising a pre-tensioning element.
14. The load sharing component of claim 13, wherein the pre-tensioning element is disposed between the resilient bearing member and the auxiliary line component.
15. The load sharing component of any one of claims 13 or 14, wherein the pre-tensioning element is positioned directly adjacent to the resilient bearing member.
16. The load sharing component of claims 13 to 15, wherein the pre-tensioning element comprises an elastomeric member.
17. The load sharing component of claims 13 to 16, wherein the elastomeric member of the pre-tensioning element has a lower axial stiffness than that of the resilient bearing member.
18. The load sharing component of claim 16 or 17 wherein the elastomeric member is arranged between first and second clamp members of the pre-tensioning element.
19. The load sharing component of claim 18 wherein the pre-tensioning element and resilient bearing member are arranged such that in use the elastomeric member can be compressed axially a pre-determined distance, until the first clamp member and second clamp member touch.
20. The load sharing component of any preceding claim wherein the resilient bearing member is annular to allow one of an auxiliary line component, a tubular, a riser or a landing string to pass there-through.
21. The load sharing component of any preceding claim, wherein the resilient bearing comprises a ring, whose wall has an undulating profile.
22. A pre-tensioning element for use in the load sharing component of any preceding claim, the pre-tensioning element comprising a pair of annular clamp members housing an elastomeric annular member there-between.
23. A pretensioing element of claim 22, wherein the clamp members each comprise an annular groove for seating the elastomeric member and accommodating deformation of the elastomeric member.