GB2429730A

GB2429730A - Riser guide with damping device

Info

Publication number: GB2429730A
Application number: GB0617085A
Authority: GB
Inventors: Malcolm Duell
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-09-01
Filing date: 2006-08-31
Publication date: 2007-03-07
Anticipated expiration: 2026-08-31
Also published as: WO2007026149A1; GB2429730B; GB0617085D0

Abstract

The present invention relates to sub-surface recovery or exploration apparatus. In an embodiment, the apparatus comprises a conductor guide 12 and a conductor tube 14 received through a guide space defined by the conductor guide 12. A damping device 29 is disposed in the guide space between the conductor guide 12 and the conductor tube 14. The damping device comprises a plurality of resilient bodies 28, which may be spherical elastic bodies disposed along the conductor tube 14.

Description

1 Damping Device 3 The present invention relates to sub-surface recovery

or 4 exploration apparatus having a damping device and a method of damping movement in sub-surface recovery or 6 exploration apparatus.

8 In a number of industries, subsurface wells are drilled 9 to provide for recovery of raw materials. After a fresh well has been drilled, it is usual to install a conductor :.:::* 11 pipe in the top of the weilbore. S.. * S

*... 12 *:::: 13 The conductor tube (or conductor casing as it is also * 14 known) is cemented in place at the top of the weilbore *0S and secures the open hole to prevent collapse. The bore 16 of the conductor tube provides access to the well and 17 equipment to be used in the well is introduced via the 18 conductor tube. The tube typically comprises thick19 walled casing and thus can also provide support for valve tree equipment, which is used in controlling operational 21 conditions of the weilbore.

1 In offshore applications, the conductor tube usually 2 extends from the top of the welibore at the seabed to 3 above the sea surface. In such applications, the 4 conductor tube is often installed and supported from a welihead platform on or above the water surface. The 6 conductor tube may then be guided to the welibore from 7 the welihead platform through a series of conductor guide 8 tubes fitted to the platform.

The conductor guide tubes have a greater diameter than 11 the conductor tube to accommodate protrusions on the 12 conductor tube, for example between adjacent conductor 13 tube sections. The conductor guide tubes are usually 14 cylindrical and have a funnel-shaped mouth to provide for ease of reception of a conductor tube in the conductor 16 guide tube.

18 When a conductor tube is installed, the conductor tube is 19 typically located passively within the conductor guide tube. The larger diameter conductor guide tube allows 21 for limited lateral movement of the conductor tube within

. 22 the conductor guide tube.

24 There are problems associated with this arrangement.

25 More specifically, the conductor tube is subject to 26 movement caused by wind and sea, which can lead to . 27 impacts between the conductor guide tube and the S...

28 conductor tube, resulting in damage to the conductor 29 tube.

31 In order to prevent impacts, existing techniques involve 32 use of a clamp arrangement attached to a support member 33 of the platform. In such a case, the clamp typically 1 grips the conductor tube above the guide tube to rigidly 2 secure the conductor tube to the platform in a near- 3 central position within the guide tube.

However, such clamp arrangements are susceptible to 6 damage due to vibrations of the conductor tube caused by 7 the motion of the sea. In addition, installation of such 8 clamp arrangements may require removal of components of 9 the guide tube to secure the clamp in place. For example, the funnel- shaped mouth of the guide tube or 11 tundish" may need to be removed. Accordingly, 12 installation operations can be time consuming and costly.

14 In other cases, shims are located in the conductor guide tubes to prevent movement of the conductor tube within 16 the conductor guide tube. However, vibrations and 17 movements of the conductor tube caused by the motion of 18 the sea can be transmitted by way of the shims to the 19 conductor guide tube, thereby causing damage to the : 20 conductor guide tube and associated equipment.

22 Moreover, wave induced movement of the conductor tube can **, 23 cause large end movements if the conductor tube and the 24 conductor guide tube are rigidly coupled. This can lead S..

to local overstressing of the conductor tube near the :.s* 26 rigid coupling points, or for example, in locations where . 27 the conductor tube flexes. S...

29 It is an aim of the invention to obviate or at least mitigate the drawbacks and deficiencies of existing sub- 31 surface recovery or exploration apparatus.

1 Other aims and objects will become apparent from the

2 description below.

4 According to a first aspect of the present invention, there is provided sub-surface recovery or exploration 6 apparatus comprising: a conductor guide defining a guide 7 space; a conductor tube received within the guide space 8 and spaced apart from the conductor guide; and a damping 9 device disposed in the space between the conductor guide and the conductor tube, the damping device being 11 configured to damp movement of the conductor tube 12 laterally of the conductor guide, the damping device 13 comprising a plurality of resilient bodies disposed along 14 the conductor tube.

16 In use, the plurality of resilient bodies damp movement 17 of the conductor tube laterally of the conductor guide.

18 This reduces the likelihood of the conductor tube 19 striking the conductor guide.

:.:::. 21 More specifically, the damping device may comprise a 22 plurality of resilient bodies disposed around the 23 conductor tube. Thus, the damping device may comprise a : 24 mass of resilient bodies in the space between the I..

conductor guide and the conductor tube. The space 26 containing the mass of bodies between the conductor guide ". 27 and the conductor tube may be substantially annular.

29 Alternatively or in addition, the damping device may consist exclusively of the plurality of resilient bodies.

32 Alternatively or in addition, the plurality of resilient 33 bodies may be disposed within the space such that they 1 are movable in relation to at least one of the conductor 2 guide and the conductor tube. In use, this can provide 3 for ease of movement of the conductor guide and the 4 conductor tube in relation to each other axially of the conductor tube. This provides for accommodation of 6 movement that arises, for example, from tidal currents 7 where the apparatus is used in offshore applications.

9 Alternatively or in addition, each of the plurality of resilient bodies may be of regular shape.

12 Alternatively or in addition, the plurality of resilient 13 bodies may comprise bodies of different shape.

More specifically, the plurality of resilient bodies may 16 comprise one or more of the following shapes: a prism, a 17 sphere, a cube, a cylinder and a tetrahedron.

19 Alternatively or in addition, the conductor guide may comprise a substantially cylindrical body having a flared :.:::* 21 portion defining a mouth of the conductor guide. In use, *. 22 the flared portion can provide for ease of reception of 23 the conductor tube in the conductor guide.

* 25 More specifically, the damping device may be disposed at 26 least in part in the space between the conductor guide **" 27 and the conductor tube defined in part by the flared *.*.

28 portion. Thus, the damping device can be disposed in the 29 space to provide for a damping effect at or around the mouth of the conductor guide.

32 Alternatively or in addition, the sub-surface recovery or 33 exploration apparatus may be configured to contain the 1 damping device within a portion of the space between the 2 conductor guide and the conductor tube. Configuration of 3 the apparatus to contain the damping device can be of use 4 when the damping device comprises a plurality of bodies that are themselves disposed in an unrestrained fashion 6 in the space between the conductor guide and the 7 conductor tube.

9 More specifically, the apparatus may comprise a containment apparatus configured to keep the damping 11 means located in the portion of the space.

13 Preferably, the containment apparatus comprises at least 14 one containment member configured to occlude the space between the space between the conductor guide and the 16 conductor tube from passage of at least part of the 17 damping device. In use, the containment member can 18 obstruct movement of the damping device along the space 19 between the conductor guide and the conductor tube.

Thus, the damping device may be configured for disposal :.:::. 21 in the space between a mouth of the conductor guide and 22 the containment member. S...

: 24 More specifically, the containment member may be * 25 configured to occlude the space below an open end of the 26 conductor guide opposing a mouth of the conductor guide.

Se.. 27 * S S...

28 Alternatively or in addition, the containment member may 29 be configured to so as to leave the conductor tube unobstructed.

32 More specifically, the containment member may be 33 configured to fit around the conductor tube.

2 More specifically, the containment member may comprise a 3 clamp arrangement for clamping the containment member 4 around the conductor tube.

6 Alternatively or in addition, the containment apparatus 7 may comprise a second containment member configured to 8 occlude the space defined by a mouth of the conductor 9 guide. In use, the second containment member may prevent escape of resilient bodies of the damping device from the 11 mouth of the conductor guide.

13 More specifically, the second containment member may be 14 configured to be received in a flared end portion of the conductor guide defining a mouth of the conductor guide.

17 Alternatively or in addition, the second containment 18 member may be configured so as to leave the conductor 19 tube unobstructed. Thus, for example, the second containment member may be configured to fit around the 21 conductor tube. 22

23 Alternatively or in addition, the containment apparatus 24 may be adapted to permit relative movement between the S. a * 25 conductor guide and the conductor tube. The relative 26 movement may be at least one of lateral and longitudinal s.-. 27 movement. a P

29 Preferably, the containment apparatus comprises a containment sleeve configured to occlude a space between 31 an end of the conductor guide tube, which opposes an end 32 configured to receive the conductor tube, and the 33 conductor tube. More preferably, the containment sleeve 1 is fitted to allow axial movement of the sleeve relative 2 to the guide tube. The containment sleeve may be axially 3 slidable relative to the conductor guide tube. The 4 containment sleeve may be fitted around an outer surface of the conductor guide tube. AlternatIvely, the 6 containment sleeve is slidably fitted on an inside 7 surface of the conductor guide tube.

9 Preferably, the apparatus is operable to damp movement of the pipe relative to the guide tube of a magnitude 11 similar to that produced during offshore operations.

13 Preferably, the apparatus is operable to damp movement of 14 the pipe relative to the guide tube in multiple directions.

17 Preferably, the plurality of resilient bodies comprises 18 at least one resilient body that is movable within the 19 plurality of resilient bodies.

:.::. 21 Preferably, the apparatus is configured to permit the at ". 22 least one resilient body to be movable in relation to the S..

23 conductor guide and the conductor tube for facilitating 24 movement, and damping of movement, of the conductor tube S..

* 25 laterally and longitudinally relative to the conductor 26 guide. In use, the resilient nature of the plurality of * 27 bodies can provide for absorption of sudden movement of 28 the conductor guide and the conductor tube in relation to 29 each other, which is liable to cause damage, whilst moveability of the at least one resilient body provides 31 for slower movement of the conductor guide and the 32 conductor tube in relation to each other, slow movement 33 being less liable to cause damage.

2 Preferably, the plurality of resilient bodies comprises 3 at least two resilient bodies that contact each other.

The resilient bodies may be configured to deform 6 elastically. The resilient bodies may be formed at least 7 in part of at least one of the following materials: 8 rubber; neoprene; polyethylene; and foam.

Alternatively or in addition, the plurality of resilient 11 bodies may comprise at least two resilient bodies sized 12 to fit in the guide space laterally adjacent to each 13 other. The at least two resilient bodies may fit in the 14 guide space when the conductor guide and the conductor tube are disposed coaxially.

17 Alternatively or in addition, a resilient body may have a 18 maximum cross-sectional dimension of between about 1 in 19 and 10 in.

21 The sub-surface recovery or exploration apparatus may be 22 configured for mineral recovery or exploration, such as 23 of oil or gas. *c. * 1S

The sub-surface recovery or exploration apparatus may be * 26 configured for at least one of on-shore operation and U..... * S

27 off-shore operation. * S 4SS*

29 According to a second aspect of the present invention there is provided a seabed installation comprising sub- 31 surface recovery or exploration apparatus according to 32 the first aspect of the present invention.

1 Embodiments of the second aspect of the present invention 2 may comprise at least one feature of the first aspect of 3 the invention.

According to a third aspect of the present invention, 6 there is provided an offshore platform comprising a 7 seabed installation according to the second aspect of the 8 invention.

According to a fourth aspect of the present invention, 11 there is provided a method of damping movement in sub- 12 surface recovery or exploration apparatus, the method 13 comprising: receiving a conductor tube within a guide 14 space defined by a conductor guide such that the conductor tube is spaced apart from the conductor guide; 16 and disposing a damping device in the space between the 17 conductor guide and the conductor tube, the damping 18 device being configured such that it is operative to damp 19 movement of the conductor tube laterally of the conductor guide, the damping device comprising a plurality of 21 resilient bodies disposed along the conductor tube.

: *** 22 23 Embodiments of the fourth aspect of the present invention * *.

24 may comprise at least one feature of the first to third S...

: 25 aspects of the invention.

27 According to a further aspect of the present invention, a.....

28 there is provided sub-surface recovery or exploration 29 apparatus comprising: a conductor guide defining an enclosed guide space; a conductor tube received within 31 the guide space and spaced apart from the conductor 32 guide; and a damping device disposed in the space between 33 the conductor guide and the conductor tube, the damping 1 device being configured to damp movement of the conductor 2 tube laterally of the conductor guide.

4 There will now be described, by way of example only, embodiments of the invention, with reference to the 6 following drawings, of which: 8 Figure 1 is a schematic cross-sectional view of oil or 9 gas recovery or exploration apparatus according to an embodiment of the invention; 12 Figure 2A is a schematic cross-sectional view of a 13 containment bracket for the apparatus of Figure 1.

Figure 2B is a schematic cross-sectional view, 16 perpendicular to the view of Figure 2A, of the 17 containment bracket of Figure 2A.

19 Figure 2C is a plan view of a first half of the containment bracket of Figure 2A; : *.* 22 Figure 2D is a cross-sectional view of the containment *.... 23 sleeve for the apparatus of Figure 1; S... S...

: 25 Figure 2E is a cross-sectional view, perpendicular to the 26 view of Figure 2D, of the containment sleeve of Figure 27 2D; S..... * 28 *..S *

29 Figure 2F is a plan view of a first half of the containment sleeve of Figure 2D; 1 Figures 3A to 3D represent in cross-sectional views, the 2 apparatus of Figure 1 during successive stages of 3 installation; Figure 4 is a cross-sectional view of oil or gas recovery 6 or exploration apparatus according to a further 7 embodiment of the invention; and 9 Figure 5 is a cross-sectional view of oil or gas recovery or exploration apparatus in operation according to a 11 further embodiment of the invention.

13 With reference firstly to Figure 1, there is generally 14 depicted apparatus 10 for use in oil or gas recovery or exploration. The apparatus 10 comprises a conductor 16 guide tube 12 (which constitutes a conductor guide). An 17 inner surface of the conductor guide tube 12 defines a 18 cylindrical volume (which constitutes a guide space) 19 through which a conductor tube 14 is received.

Furthermore, the tube defines a longitudinal axis 2 arid 21 latitudinal axis 4, and upper and lower ends 6,8 of the : 22 apparatus. S...

*... 23 * . 24 In addition, the conductor guide tube 12 comprises a S...

: 25 flared section 13 and a tubular main section 15. The 26 flared section is known in the art as a tundish' and the 27 main tubular section 15 is known as a barrel'. The S. ***: 28 flared section is shaped to facilitate the introduction 29 of the conductor tube through the conductor guide tube, i.e., the wider diameter provides a larger target and 31 makes it easier to locate the conductor tube through the 32 conductor guide tube. The diameter of the flared section 33 13 decreases progressively from top end 6 toward the 1 bottom end 8 of the apparatus until the flared section 2 meets the main tubular section 15. In the tubular 3 section 15, the diameter remains substantially constant.

Damping material 29 (constituting a damping device) is 6 located in the space between the inner surface of the 7 conductor guide tube 12 and an outer surface of the 8 conductor tube 14. The damping material 29 consists of a 9 mass of resilient balls 28. The damping material acts to damp movement of the conductor tube 14 relative to the 11 conductor guide tube 12.

13 Toward the lower end 8 of the conductor guide tube 12, 14 there is located a containment member 16. The containment member 16 can be seen in more detail with 16 further reference to Figures 2A to 2F, and comprises a 17 bracket 20 that is clamped to the conductor tube 14. The 18 bracket 20 in turn comprises a body of two semi-tubular 19 halves 201a,b, which can be clamped together. In this embodiment, the two halves of the bracket body are 21 clamped together by means of bolts 18 located through : .. 22 holes in protruding and opposing surfaces 38 of the body * 23 halves. A neoprene lining is provided between the *S** 24 conductor tube 14 and surfaces of the bracket 20 that act U...

*..* : 25 against the conductor tube 14 to avoid a metal-to-metal 26 contact of the tube and the clamp. The neoprene lining 27 helps to protect the pipe from damage due to clamping of 28 the bracket 20.

The bracket 20 further comprises a containment plate 22 31 protruding radially at the top of the bracket body. When 32 the bracket is clamped, the containment plate provides a 33 top plate surface 35 that is substantially perpendicular 1 to a longitudinal axis of the conductor tube and is 2 substantially continuous around the circumference of the 3 conductor tube 14.

The containment plate 22 functions to support the damping 6 material 29 near the bottom of the guide tube 12. The 7 containment plate 22 thereby helps to prevent the 8 resilient balls 28 from escaping from the guide space.

9 The guide tube 12 and the containment apparatus 16 acts to contain the damping material in place.

12 The containment apparatus 16 also comprises a containment 13 sleeve 24 which rests on the top surface 35 of the plate 14 22 and is partially located around the bottom end of the guide tube 12. The containment sleeve 24 may slide 16 across the surface 35 as the conductor tube moves 17 laterally relative to the guide tube. The containment 18 sleeve 24 is formed from two semi-tubular sleeve halves 19 241a,b clamped together via bolts 37 in a manner similar to that described above with reference to the bracket 20.

21 When clamped, the containment sleeve 24 comprises a * 22 tubular main body 26 with an internal diameter that is , 23 similar to the outer diameter of the guide tube 12 at its * S..

24 bottom end to provide a clearance fit around the bottom ***.

: 25 portion of the main tubular section of the guide tube. 26

27 The containment sleeve 24 assists in preventing the **. S.. * S

*** 28 resilient balls 28 from escaping the guide space.

In the present configuration, the containment apparatus 31 16 is arranged with the bracket 20 clamped to the 32 conductor tube 14 in a position near the bottom end 8 of 33 the guide tube 12 such that the bottom end of the guide 1 tube is received within a space defined by inner surfaces 2 of the sleeve 24.

4 The present arrangement provides a plate gap 32 between a bottom edge of the guide tube 12 and the top surface 35 6 of the containment plate 22. The plate gap 32 is 7 provided to accommodate axial movement of the conductor 8 tube as indicated by the arrow 39. The axial movement of 9 the conductor tube typically results from flexure of the conductor tube, for example, due to horizontal currents 11 acting on the conductor tube. The plate gap can 12 accommodate a range of relative axial movement of the 13 conductor tube and the guide tube up to around 4 inches.

As the sleeve 24 rests on the containment plate and is 16 movable axially with respect to the guide tube, the 17 sleeve is able to function to provide the required 18 obstruction to the balls at various offsets of the 19 conductor tube relative to the guide tube, i.e., offsets within the range provided for by the plate gap.

: 22 It will however be appreciated that in other embodiments, **..

23 the apparatus could be configured with a gap to 24 accommodate a greater or lesser range of axial movement. s..

: 25 In such cases, the axial length of the sleeve may be 26 different, but suitable for preventing escape of the 27 balls.

*U*I..

29 The apparatus 10 is also provided with a cover arrangement 40 (which constitutes a second containment 31 member) at the top end 6 of the guide tube 12. The cover 32 arrangement 40 comprises a second bracket 44 provided 33 with a second containment plate 42 in a similar manner to 1 the bracket 20 at the opposite end of the guide tube 12.

2 However, in this case, the second containment plate 42 3 rests on the top edge of the flared section, and the 4 second bracket 44 is merely fitted around the conductor tube 14.

7 The bracket cover arrangement is formed in two semi- 8 tubular halves and clamped together using bolts to 9 provide a clearance fit around the conductor tube. This allows the conductor tube to move axially relative to the 11 guide tube, while the second containment plate 42 can 12 remain in position on the flared section to prevent 13 dislodgement of the damping material 29 and resilient 14 balls 28 from the top of the guide tube 12.

16 The damping material 29 comprises discrete balls 28 with 17 resilient properties. The damping material 29 acts to 18 damp relative movement of the conductor tube 14 and the 19 conductor guide tube 12. The mass of balls 28 located within the guide tube function together to resiliently 21 damp the relative movement. * S.

* * * 22 *...

*. 23 The resilient balls 28 are of similar dimensions and are *...

24 sized to fit in the guide space between the conductor *. * S S

* 25 tube and the tubular main section 15 of the conductor 26 guide tube. In other embodiments of the invention the 27 balls may have an maximum dimension of between 1 and 7 S.....

28 inches. It will be appreciated however, that balls with *...

29 maximum dimensions outside this range could be used.

Between the individual resilient balls, there exist 31 pockets 46 of the guide space. Upon the exertion of a 32 force (i.e. from a moving conductor tube), for example 33 due to movement of the conductor pipe within the 1 conductor guide tube, the resilient balls 28 may 2 displace, deform and move relative to each other within 3 the guide space, into and around the pockets 46. This 4 allows the conductor tube 14 to move laterally and axially within the conductor guide tube whilst preventing 6 the conductor tube from touching the conductor guide tube 7 sides. The mass of resilient balls 28 behave 8 elastically, i.e. the material of the bodies allows the 9 conductor tube to displace relative to the conductor guide tube before tending to return the conductor tube to 11 its original or equilibrium position within the conductor 12 guide tube.

14 In this case, the balls are formed of neoprene material.

In other embodiments however, the balls could be formed 16 from plastic or rubber materials. More specifically, the 17 balls may be formed from materials such as nylon, 18 Teflon , Keviar , aranilds, polyethylenes, or any other 19 suitable resilient material. In addition, the damping material 29 could comprise spheres, cubes, cylinders or 21 any other appropriately sized prismatic body. * **

* * * 22 23 The mass of balls 28 displaces as the conductor tube 24 moves within the conductor guide tube, and surrounds the * * S * 25 conductor tube as it moves within the conductor guide **S * 26 tube to thereby provide support. This helps to prevent 27 damage to the apparatus which could otherwise arise from *... 28 sudden movement of the conductor tube. * * S...

A sub-set of balls located in the guide space of the 31 flared section of the guide tube can also act as a back- 32 up reservoir of balls that can replace and fill the space 33 left by any balls that for any reason become removed from 1 the guide space, e.g., under extreme or irregular 2 operating conditions.

4 In another embodiment of the invention, the damping apparatus 100 of Figure 4 shows a conductor guide tube 6 102 is fitted to an offshore platform. In this case, the 7 guide tube 102 is, as known in the art, attached and 8 fixed to tubular members 114 of a platform, and the 9 tubular members 114 are in turn fixed to and supported from a support structure 112 of the platform.

12 In this configuration, a conductor tube 104 extends from 13 a well at the seabed through the conductor guide tube 102 14 fixed to the platform structure. The ocean environment causes vertical and horizontal components of movement of 16 conductor tubing. For example, waves, wind and tides can 17 cause the conductor tube to move within the conductor 18 guide tube, and the present damping apparatus 100 is 19 adapted to accommodate such movement in both latitudinal and longitudinal directions, whilst damping sudden 21 movements that could cause damage. * S. S...

23 The apparatus 100 is otherwise configured in a similar 24 manner to the apparatus 10 described above, although the * 25 apparatus 100 is provided with a sleeve 108 that is * 26 located on the inside of the guide tube 102. The sleeve 27 108 comprises two semi-tubular halves, which can be 28 clamped together in a similar manner to the sleeve 55*S 29 described above. However, in this case, bolted opposed surfaces protruding radially from the clamp are provided 31 toward the bottom end of the sleeve. An outer surface of 32 the sleeve is slidably located against the inside surface 33 of the guide tube 102. The sleeve axially slidable 1 relative to the guide tube 102, and provides a similar 2 function as the sleeve 24 of apparatus 10 in preventing 3 balls 28 from exiting the guide space from the bottom end 4 of the guide tube 104. The containment plate is located on the conductor tube such that the protruding surfaces 6 of the sleeve when resting on the containment surface, do 7 not interfere with or prevent slidable axial movement of 8 the conductor tube and sleeve relative to the guide tube.

In use, the present sub-surface recovery or exploration 11 damping apparatus may be installed on an offshore 12 platform near a well to which access is required from the 13 platform.

A conductor guide tube is fitted to the platform and a 16 conductor tube is introduced into the flared section of 17 the conductor guide tube and inserted through the 18 conductor guide tube and into the top portion of the 19 well. The lower end of the conductor tube is secured in place at the top of the well. The top end of the 21 conductor tube is accessible at the platform. * 22 23 The bracket 20 is clamped to the conductor tube near the 24 bottom end

of the conductor guide tube and the : 25 containment sleeve 24 is movably located around the * 26 bottom end of the conductor guide tube. This sleeve 24 27 is positioned so that it rests on the top surface of the 28 containment plate of the bracket 20. The sleeve is **** 29 slidably located on the top surface in order that it can move across the surface and accommodate lateral movement 31 of the conductor guide tube relative to the conductor 32 tube. Furthermore, the sleeve is sized and the bracket 33 attached to the conductor tube, such that the top edge of 1 the sleeve body, when resting on the plate top surface, 2 overlaps the bottom edge of the conductor guide tube.

3 Furthermore, the bracket is positioned such that there is 4 provided a gap between the bottom edge of the conductor guide tube and the top surface of the plate to 6 accommodate vertical components of motion of the 7 conductor tube relative to the conductor guide tube.

9 The damping device, which consists of a plurality of resilient balls 28, is introduced into the guide space 11 between the guide tube and the conductor tube. With 12 reference to Figures 3A to 3D, the conductor tube 14 is 13 in Figure 3A located through the guide tube 12 defining a 14 guide space 301 for introduction of damping material. In Figure 3B an initial set of the balls 281 are introduced 16 in a first accessible portion of the guide space 301 17 while the conductor tube 14 is located off-centre in the 18 guide space. The conductor tube moves to another of f- 19 centre position, in the case of Figure 3C forcing the first set of balls 281 into a squashed position, and a 21 further set of balls 282 is introduced into the guide :.:.. 22 space 301 at a second accessible portion of the guide *S..

* 23 space. As the conductor tube moves away from the of f- *, 24 centre position, for example, due to external influences or by deliberately moving the tube, the balls 281 and 282 * 26 tend to settle around the conductor tube, providing : 27 damping and tending centralise the conductor tube within * . **, 28 the guide tube as shown in Figure 3D.

The bracket 20 and sleeve 24 act to keep the plurality of 31 balls 28 in location in the guide space and prevent the 32 bodies from escaping. The plate supports the resilient 1 bodies near the bottom of the conductor guide tube and 2 corresponding guide space.

4 Furthermore1 a top cover arrangement (which constitutes a second containment member) is located over the top end of 6 the conductor guide tube to prevent the resilient balls 7 28 from escaping out of the top of the apparatus.

9 Movement of the water at the offshore locality produces forces acting against the platform and/or conductor tube 11 that may cause movement of the conductor tube relative to 12 the conductor guide tube. This movement will in general 13 comprise vertical and horizontal components, and the 14 present apparatus damps such movement by means of the resilient balls 28.

17 With reference to Figure 5, example sub-surface recovery 18 or exploration damping apparatus according to a further 19 embodiment is depicted generally at 600. The apparatus 600 comprises a conductor guide tube 601, through which a 21 conductor tube 604 is received. The apparatus has a mass * S. 22 of balls 606 contained in the guide space between inner I...

, 23 surfaces of the guide tube and an outer surface of the 24 conductor, in a manner similar to other embodiments : 25 described above.

*...: 27 Figure 5 further provides an illustration of the * S ** 28 apparatus 600 during operation after forces acting on the S..

29 conductor tube 604 have caused the tube to move into an off-centre position within and relative to the guide tube 31 602 as indicated by arrows 610. The centre axis of the 32 guide tube is indicated by reference numeral 605. The 33 mass of resilient balls 606 act to accommodate the 1 lateral displacement of the conductor tube. In this 2 case, a first set of balls 608a become compressed against 3 the inner surface of the guide tube facing the direction 4 of movement of the conductor tube. This set of balls 608a tends to absorb movement of the conductor tube and 6 tends to resiliently oppose the movement of the conductor 7 tube, pushing it toward an equilibrium position in the 8 centre of the guide tube.

A second set of balls 608b fall from a reservoir of balls 11 in the funnel portion, according to arrows 612, into the 12 guide space behind the conductor tube as it travels 13 laterally, thus keeping the space filled with resilient 14 balls. In this case, a number of balls fit laterally adjacent to each other in the guide space.

17 When the conductor tube returns to its equilibrium 18 position, the balls 608b will then compress and/or 19 displace relative to each other in response to the return motion, while supporting the conductor tube.

.:.: 22 In general, the balls will move up and down, in and *1* .,.. 23 around the guide space to fill the space, and move into

, 24 and out of gaps according to the motion of the conductor tube, whether including lateral and/or longitudinal e..

26 components of motion. *

28 Accordingly, the balls allow the conductor tube to be 29 fully supported and "caressed" as it moves, in a manner similar to a "bean bag", and then moved back into an 31 equilibrium position. As the conductor tube moves from 32 side to side, the motion of the conductor tube is damped 33 without damaging impacts occurring.

2 The present invention is advantageous as it is able to 3 efficiently damp motion of a conductor pipe induced in a 4 vertical and horizontal direction. This can reduce damage to conductor tube and conductor guide tube *6 equipment as typically used in harsh offshore 7 environments and can help to prevent damage of other 8 equipment, such as welihead valve tree piping, that is 9 typically supported by the conductor tube.

11 In addition, the present apparatus can be installed 12 relatively easily and non-destructively, e.g., without 13 having to remove components of existing guide tube 14 equipment.

16 Various modifications and improvements may be made 17 without departing from the invention herein described. * S. s *

S I... * *

S

S S.... * a *5*S a S.S

Claims

1 CLAIMS 3 1. Sub-surface recovery or exploration apparatus 4 comprising:

- a conductor guide defining a guide space; 6 - a conductor tube received within the guide space 7 and spaced apart from the conductor guide; and 8 - a damping device disposed in the space between the 9 conductor guide and the conductor tube, the damping device being configured to damp movement 11 of the conductor tube laterally of the conductor 12 guide, the damping device comprising a plurality 13 of resilient bodies disposed along the conductor 14 tube.

16 2. Sub-surface recovery or exploration apparatus as 17 claimed in Claim 1, wherein the damping device 18 comprises a plurality of resilient bodies disposed 19 around the conductor tube.

21 3. Sub-surface recovery or exploration apparatus as 22 claimed in Claim 2, wherein the damping device 23 comprises a mass of resilient bodies in the space * ** *:s* 24 between the conductor guide and the conductor tube. **** * *

:::. 26 4. Sub-surface recovery or exploration apparatus as 27 claimed in Claim 3, wherein the space containing the 28 mass of bodies between the conductor guide and the 29 conductor tube is substantially annular. **.*

* * 30 S...

31 5. Sub-surface recovery or exploration apparatus as 32 claimed in any one of Claims 1 to 4, wherein the 1 damping device consists exclusively of the plurality 2 of resilient bodies.

4 6. Sub-surface recovery or exploration apparatus as claimed in any one of Claims 1 to 5, wherein the 6 plurality of resilient bodies is disposed within the 7 space such that they are movable in relation to at 8 least one of the conductor guide and the conductor 9 tube.

11 7. Sub-surface recovery or exploration apparatus as 12 claimed in any one of Claims 1 to 6, wherein each of 13 the plurality of resilient bodies is of regular 14 shape.

16 8. Sub-surface recovery or exploration apparatus as 17 claimed in any one of Claims 1 to 7, wherein the 18 plurality of resilient bodies comprises bodies of 19 different shape.

21 9. Sub-surface recovery or exploration apparatus as 22 claimed in any one of Claims 1 to 8, wherein the * 23 plurality of resilient bodies comprises one or more 24 of the following shapes: a prism, a sphere, a cube, a cylinder and a tetrahedron. * e *

*:. 27 10. Sub-surface recovery or exploration apparatus as 28 claimed in any one of the preceding claims, wherein :w: 29 the conductor guide may comprise a substantially S...

,..* 30 cylindrical body having a flared portion defining a 31 mouth of the conductor guide.

1 11. Sub-surface recovery or exploration apparatus as 2 claimed in any one of the preceding claims, wherein 3 the damping device is disposed at least in part in 4 the space between the conductor guide and the conductor tube defined in part by the flared 6 portion.

8 12. Sub-surface recovery or exploration apparatus as 9 claimed in any one of the preceding claims, wherein the sub-surface recovery or exploration apparatus is 11 configured to contain the damping device within a 12 portion of the space between the conductor guide and 13 the conductor tube.

13. Sub-surface recovery or exploration apparatus as 16 claimed in any one of the preceding claims, wherein 17 the apparatus comprises a containment apparatus 18 configured to keep the damping means located in the 19 portion of the space.

21 14. Sub-surface recovery or exploration apparatus as 22 claimed in Claim 13, wherein the containment * * 23 apparatus comprises at least one containment member ::f::: 24 configured to occlude the space between the space 25 between the conductor guide and the conductor tube *:. 26 from passage of at least part of the damping device. ** S :. 27

28 15. Sub-surface recovery or exploration apparatus as :: 29 claimed in Claim 14, wherein the damping device is S...

configured for disposal in the space between a mouth 31 of the conductor guide and the containment member.

1 16. Sub-surface recovery or exploration apparatus as 2 claimed in Claim 14 or Claim 15, wherein the 3 containment member is configured to occlude the 4 space below an open end of the conductor guide opposing a mouth of the conductor guide.

7 17. Sub-surface recovery or exploration apparatus as 8 claimed in any one of Claims 14 to 16, wherein the 9 containment member is configured to so as to leave the conductor tube unobstructed.

12 18. Sub-surface recovery or exploration apparatus as 13 claimed in any one of Claims 14 to 17, wherein the 14 containment member is configured to fit around the conductor tube.

17 19. Sub-surface recovery or exploration apparatus as 18 claimed in any one of Claims 14 to 18, wherein the 19 containment member comprises a clamp arrangement for clamping the containment member around the conductor 21 tube.

* *, 23 20. Sub-surface recovery or exploration apparatus as 24 claimed in Claim 13 or Claim 14, or any of Claims 15 25 to 19 when in dependence on Claim 14, wherein the *:. 26 containment apparatus comprises a second containment ** S *:. 27 member configured to occlude the space defined by a 28 mouth of the conductor guide.

S.....

* . 29 S...

21. Sub-surface recovery or exploration apparatus as 31 claimed in Claim 20, wherein the second containment 32 member is configured to be received in a flared end 1 portion of the conductor guide defining a mouth of 2 the conductor guide.

4 22. Sub-surface recovery or exploration apparatus as claimed in Claim 20 or Claim 21, wherein the second 6 containment member is configured so as to leave the 7 conductor tube unobstructed.

9 23. Sub-surface recovery or exploration apparatus as claimed in Claim 22, wherein the second containment 11 member is configured to fit around the conductor 12 tube.

14 24. Sub-surface recovery or exploration apparatus as claimed in any one of the preceding claims, wherein 16 the containment apparatus is adapted to permit 17 relative movement between the conductor guide and 18 the conductor tube.

25. Sub-surface recovery or exploration apparatus as 21 claimed in Claim 24, wherein the relative movement 22 is at least one of lateral and longitudinal * , 23 movement. * U S U... *S.*

25 26. Sub-surface recovery or exploration apparatus as . 26 claimed in any one of the preceding claims, wherein S. 5 * 27 the containment apparatus comprises a containment 28 sleeve configured to occlude a space between an end :: 29 of the conductor guide tube, which opposes an end 5S55 configured to receive the conductor tube, and the 31 conductor tube.

1 27. Sub-surface recovery or exploration apparatus as 2 claimed in Claim 26, wherein the containment sleeve 3 is fitted to allow axial movement of the sleeve 4 relative to the guide tube.

6 28. Sub-surface recovery or exploration apparatus as 7 claimed in Claim 26 or Claim 27, wherein the 8 containment sleeve is axially slidable relative to 9 the conductor guide tube.

11 29. Sub-surface recovery or exploration apparatus as 12 claimed in any one of Claims 26 to 28, wherein the 13 containment sleeve is fitted around an outer surface 14 of the conductor guide tube.

16 30. Sub-surface recovery or exploration apparatus as 17 claimed in any one of Claims 26 to 28, wherein the 18 containment sleeve is slidably fitted on an inside 19 surface of the conductor guide tube.

21 31. Sub-surface recovery or exploration apparatus as 22 claimed in any one of the preceding claims, wherein * *. 23 the apparatus is operable to damp movement of the 24 pipe relative to the guide tube of a magnitude similar to that produced during offshore operations. * * * S. *

*, 27 32. Sub-surface recovery or exploration apparatus as 28 claimed in any one of the preceding claims, wherein *SS*..

* * 29 the apparatus is operable to damp movement of the S...

pipe relative to the guide tube in multiple 31 directions.

1 33. Sub-surface recovery or exploration apparatus as 2 claimed in any one of Claims 1 to 32, wherein the 3 plurality of resilient bodies comprises at least one 4 resilient body that is movable within the plurality of resilient bodies.

7 34. Sub-surface recovery or exploration apparatus as 8 claimed in any one of the preceding claims, wherein 9 the apparatus is configured to permit the at least one resilient body to be movable in relation to the 11 conductor guide and the conductor tube for 12 facilitating movement, and damping of movement, of 13 the conductor tube laterally and longitudinally 14 relative to the conductor guide.

16 35. Sub-surface recovery or exploration apparatus as 17 claimed in any one of the preceding claims, wherein 18 the plurality of resilient bodies comprises at least 19 two resilient bodies that contact each other.

21 36. Sub-surface recovery or exploration apparatus as 22 claimed in any one of the preceding claims, wherein : ** 23 the resilient bodies are configured to deform 24 elastically. * * *..* ***.

: 26 37. Sub-surface recovery or exploration apparatus as *. 27 claimed in any one of the preceding claims, wherein 28 the resilient bodies are formed at least in part of *.**** * 29 at least one of the following materials: rubber; **** neoprene; polyethylene; and foam.

32 38. Sub-surface recovery or exploration apparatus as 33 claimed in any one of the preceding claims, wherein 1 the plurality of resilient bodies comprises at least 2 two resilient bodies sized to fit in the guide space 3 laterally adjacent to each other.

39. Sub-surface recovery or exploration apparatus as 6 claimed in any one of the preceding claims, wherein 7 a resilient body has a maximum cross-sectional 8 dimension of between about 1 in and 10 in.

40. Sub-surface recovery or exploration apparatus as 11 claimed in any one of the preceding claims, wherein 12 the sub-surface recovery or exploration apparatus is 13 configured for mineral recovery or exploration.

41. Sub-surface recovery or exploration apparatus as 16 claimed in any one of the preceding claims, wherein 17 the sub-surface recovery or exploration apparatus is 18 configured for at least one of on-shore operation 19 and off-shore operation.

21 42. A seabed installation comprising sub-surface 22 recovery or exploration apparatus as claimed in any : *** 23 one of Claims 1 to 41. *... *

43. An offshore platform comprising a seabed **II : 26 installation as claimed in Claim 42. *. 27

28 44. A method of damping movement in sub-surface recovery * *. S. 29 or exploration apparatus, the method comprising: - receiving a conductor tube within a guide space 31 defined by a conductor guide such that the 32 conductor tube is spaced apart from the conductor 33 guide; and 1 disposing a damping device in the space between 2 the conductor guide and the conductor tube, the 3 damping device being configured such that it is 4 operative to damp movement of the conductor tube laterally of the conductor guide, the damping 6 device comprising a plurality of resilient bodies 7 disposed along the conductor tube.

9 45. A method as claimed in Claim 44, wherein the sub- surface recovery or exploration apparatus is an sub- 11 surface recovery or exploration apparatus as claimed 12 in any one of Claims 1 to 41. * ** * * S * * S... * SS *S * IS.

S

I * I* * S IS..

S S S...