Abandonment and Recovery of Pipelines

Abstract

A method of converting a subsea laying system of a surface vessel from a laying mode to an abandonment or recovery mode Includes clamping at least one tubular sleeve in at least one clamp of the laying system. A winch wire can then run longitudinally through the or each clamped sleeve when suspending an elongate subsea element such as a pipe string during abandonment or recovery operations. The sleeve protects gripping pads of the clamp from damage due to dashing with the wire and so makes it unnecessary to remove the pads in preparation for abandonment or recovery.

Claims

1-45. (canceled)

46. A method of converting a subsea laying system of a surface vessel from a laying mode to an abandonment or recovery mode comprises: clamping at least one tubular sleeve in at least one clamp of the laying system; and running a wire longitudinally through the or each clamped sleeve to suspend an elongate subsea element during abandonment or recovery.

47. The method of claim 46, comprising placing the sleeve onto an upper end of the elongate subsea element before clamping the sleeve.

48. The method of claim 47, comprising self aligning the sleeve with the elongate subsea element along a common longitudinal axis as a consequence of lowering the sleeve onto the elongate subsea element.

49. The method of claim 48, comprising inserting the upper end of the elongate subsea element into a lower end of the sleeve.

50. The method of claim 49, comprising inserting the upper end of the elongate subsea element into a radially enlarged skirt at the lower end of the sleeve.

51. The method of claim 50, wherein the skirt is enlarged relative to a body portion of the sleeve, which body portion has an outer diameter substantially the same as that of the elongate subsea element.

52. The method of claim 50, comprising seating a shoulder at an upper end of the skirt onto the upper end of the elongate subsea element.

53. The method of claim 47, comprising interposing a buffer component at an interface between the sleeve and the upper end of the elongate subsea element.

54. The method of claim 46, comprising lowering the elongate sub, ea element relative to the clamped sleeve.

55. The method of claim 46, comprising effecting relative vertical movement between the sleeve and the clamp before clamping the sleeve in the clamp.

56. The method of claim 55, comprising lowering the clamp into alignment with the sleeve supported by the elongate subsea element.

57. The method of claim 56, wherein the clamp is a traveling clamp of a lay tower, movable vertically along the lay tower.

58. The method of claim 56, comprising lifting the clamped sleeve away from the upper end of the elongate subsea element.

59. The method of claim 46, comprising lowering the sleeve supported by the elongate subsea 59 element into alignment with the clamp.

60. The method of claim 59, wherein the clamp is a stationary clamp of a lay tower, in a substantially fixed vertical position with respect to the lay tower.

61. The method of claim 46, comprising lowering the wire into the sleeve and then coupling the wire to the elongate subsea element.

62. The method of claim 61, comprising coupling the wire to the elongate subsea element within the sleeve.

63. The method of claim 62, comprising accessing or viewing the wire through a wall of the sleeve when coupling the wire to the elongate subsea element.

64. The method of claim 61, comprising coupling the wire to the elongate subsea element underwater.

65. The method of claim 46, preceded by suspending the sleeve and lifting the suspended sleeve into alignment with the clamp.

66. The method of claim 46, comprising: clamping a first tubular sleeve in a first clamp of the laying system; clamping a second tubular sleeve in a second clamp of the laying system; and running the wire longitudinally through the clamped first and second sleeves to suspend the elongate subsea dement fear abandonment or recovery.

67. The method of claim 66, comprising: effecting relative vertical movement between the second sleeve and the second clamp; clamping the second sleeve in the second clamp; effecting relative vertical movement between the first sleeve and the first clamp; and clamping the first sleeve in the first clamp.

68. The method of claim 67, comprising: lowering the second clamp into alignment with the second sleeve before clamping the second sleeve in the second clamp; and lowering the first sleeve into alignment with the first clamp before clamping the first sleeve in the first clamp.

69. The method of claim 68, comprising: placing the first and second sleeves together onto the upper end of the elongate subsea element; and separating the first sleeve from the second sleeve.

70. The method of claim 69, comprising separating the first sleeve from the second sleeve by lowering the first sleeve supported by the elongate subsea element into alignment with the first clamp.

71. The method of claim 69, preceded by locking together the first and second sleeves and, after placing the first and second sleeves together onto the upper end of the elongate subsea element, unlocking, the first and second sleeves to permit their separation.

72. The method of claim 69, comprising separating the first sleeve from the second sleeve by telescopic relative movement.

73. The method of claim 69, wherein the second sleeve rests on the first sleeve when placed together onto the upper end of the elongate subsea element.

74. A sleeve for use in protecting gripping elements of a clamp of a subsea laying system, the sleeve comprising: a tubular body portion; a tubular skirt on an end of the body portion, aligned with the body portion along a common longitudinal axis to define a lumen that extends continuously along the sleeve through the body portion and the skirt; and an internal seating formation in the lumen between the body portion and the skirt; wherein the skirt is enlarged radially relative to the body portion and has an internal diameter that is greater than the external diameter of the body portion.

75. The sleeve of claim 74, wherein the seating formation is defined by a narrowing of the lumen.

76. The sleeve of claim 75, wherein the seating formation is frusto-conical and tapers from the skirt to the body portion.

77. The sleeve of claim 74, further comprising a flared guide formation at a free end of the skirt.

78. The sleeve of claim 74, wherein a wall defining the body portion is penetrated by one or more apertures that are offset longitudinally toward a junction between the body portion and the skirt.

79. The sleeve of claim 74, wherein a wall defining the skirt is penetrated ne or more slots that extend longitudinally along the skirt.

80. The sleeve of claim 79, further comprising an auxiliary sleeve mounted on the body portion.

81. The sleeve of claim 80, wherein the auxiliary sleeve is positioned around the body portion or on a free end of the body portion.

82. The sleeve of claim 80, further comprising at least one releasable fastening that acts between the sleeve and the auxiliary sleeve.

83. In combination, the sleeve of claim 74 with an interface cap that has an outer side shaped to complement the internal seating formation and an inner side shaped t receive a pipe end.

84. The combination of claim 83, wherein the outer side of the cap has a chamfered edge whose inclination substantially corresponds to inclination of the seating formation of the sleeve relative to the longitudinal axis.

85. The combination of claim 83, wherein the inner side of the cap is surrounded by a longitudinally extending peripheral formation that is arranged to encircle or embrace a pipe end.

86. The combination of claim 85, wherein the cap further comprises a resilient component on an radially inner side of the peripheral formation.

87. The combination of claim 85, wherein the cap is penetrated by a central opening.

88. The combination of claim 87, wherein the diameter of the central opening is less than the inner diameter of the peripheral formation, defining an annular hearing surface that extends in a plane between the central opening and the peripheral formation.

Description

[0067] To put the invention into context, reference has already been made to FIGS. 1 and 2 of the accompanying drawings. In those drawings:

[0068] FIG. 1 is a simplified schematic side view of a conventional J-lay system of a pipelay vessel, shown here adding a pipe joint to the top of a pipe string suspended from the vessel; and

[0069] FIG. 2 corresponds to FIG. 1 but shows the pipe string being lowered into the sea after the additional pipe joint has been welded to the top of the pipe string.

[0070] In order that the invention may be more readily understood, reference will now be made, by way of example, to the remaining drawings in which:

[0071] FIG. 3 is a perspective view of a protective sleeve of the invention;

[0072] FIG. 4 is a side view of the sleeve shown in FIG. 3;

[0073] FIGS. 5a to 5d are a sequence of part-sectional side views of a workstation of a J-lay system at which pipe joints are welded to the top of a pipe string, showing how the sleeve of FIGS. 3 and 4 may be used to protect a travelling clamp of the system during A&R operations;

[0074] FIGS. 6a to 6c are a sequence of part-sectional side views of the workstation shown in FIGS. 5a to 5d, showing how the sleeve of FIGS. 3 and 4 may be used to protect a stationary clamp of the J-lay system during A&R operations;

[0075] FIG. 7 is a side view of a variant of the sleeve shown in FIGS. 3 and 4;

[0076] FIG. 8 is a part-sectional side view of the sleeve variant shown in FIG. 7;

[0077] FIGS. 9a to 9e are a sequence of schematic part-sectional side views that show how the sleeve variant of FIGS. 7 and 8 may be used to protect both a travelling clamp and a stationary clamp of a J-lay system during A&R operations;

[0078] FIG. 10 is a side view of a further sleeve variant of the invention that may be used to protect both a travelling clamp and a stationary clamp of a J-lay system during A&R operations;

[0079] FIG. 11 is an enlarged sectional side view of an interface between a sleeve of the invention and the top of a pipe string;

[0080] FIG. 12 is a further enlarged sectional side view of a cap of the invention that is interposed between the sleeve and the top of the pipe string at the interface shown in FIG. 11;

[0081] FIG. 13 is a sectional side view of a variant of the cap shown in FIG. 12; and

[0082] FIG. 14 is an enlarged detail view corresponding to Detail XIV of FIG. 13.

[0083] Referring firstly to FIGS. 3 and 4, these drawings show a protective sleeve 44 of the invention. The sleeve 44 could be of any suitable material but is conveniently fabricated from rolled steel plate or from short lengths of pipe.

[0084] The sleeve 44 comprises a tubular body portion 46 and a tubular skirt 48 that is welded to one end of the body portion 46. The body portion 46 and the skirt 48 share a common central longitudinal axis 50. The outer surface of the body portion 46, at least, may be coated, textured or shaped to maximise grip of the friction clamps 26, 30 shown in FIGS. 1 and 2. The body portion 46 also comprises lifting holes 52 into which removable shackles 54 may be fitted for attaching lifting straps to lift and manipulate the sleeve 44.

[0085] The body portion 46 and the skirt 48 are each substantially straight and are each of substantially constant external diameter along their length. The body portion 46 is suitably of a similar outer diameter to a pipe string 20 with which the sleeve 44 will be used during A&R operations, as will be explained. However, the skirt 48 is wider than the body portion 46. Preferably the skirt 48 has an internal diameter that is greater than the outer diameter of the body portion 46.

[0086] A frusto-conical step or shoulder 56 effects a transition in the width of the sleeve 44 between the narrower body portion 46 and the wider skirt 48. A frusto-conical outwardly-flared guide formation 58 surrounds the open end of the skirt 48 opposed to the shoulder 56.

[0087] The body portion 46 is penetrated by a circumferential array of apertures 60. The apertures 60 are angularly spaced around the circumference of the body portion 46 and are offset longitudinally toward the skirt 48, to a position close to the shoulder 56 between the body portion 46 and the skirt 48. The skirt 48 is similarly penetrated by a circumferential array of longitudinally-extending slots 62 that are angularly spaced around the circumference of the skirt 48. The slots 62 and the apertures 60 reduce the weight of the sleeve 44 and provide visual and physical access to the interior of the body portion 46 and the skirt 48.

[0088] A sleeve 44 of the invention may be used in various ways to protect either or both of the friction clamps 26, 30 shown in FIGS. 1 and 2 from damage due to clashing with an A&R wire 40. The A&R wire 40 extends longitudinally within, along and through the sleeve 44. The body portion 46 of the sleeve 44 lies radially inwardly of, and hence protects, the pads or other gripping elements of the clamp 26, 30 in which the sleeve 44 is held. This obviates the need to remove the pads or other gripping elements from the clamp 26, 30 in preparation for A&R operations, which ensures safety and saves time.

[0089] FIGS. 5a to 5d show how the sleeve 44 may be used to protect the travelling clamp 30. In this respect, the travelling clamp 30 is typically at greater risk of damage from an A&R wire 40 than the stationary clamp 26. For example, the pads of the stationary clamp 26 may be retracted radially to a greater extent than the pads of the travelling clamp 30 to allow more clearance around the A&R wire 40. Also, the sides of an opening on the launch axis in an enclosure surrounding the upper workstation 22 may serve to limit deflection of the A&R wire 40 through the stationary clamp 26.

[0090] FIG. 5a shows an upper end portion of a pipe string 20 held by the stationary clamp 26 under the upper workstation 22. Pads 64 of the stationary clamp 26 are shown here extended radially inwardly into clamping engagement with the pipe string 20. The upper extremity of the pipe string 20 extends above the stationary clamp 26 into the upper workstation 22.

[0091] FIG. 5b shows the sleeve 44 lowered onto the protruding upper end of the pipe string 20 in the upper workstation 22. The sleeve 44, shown here suspended from a lifting strap 66, is held in a substantially vertical orientation with the body portion 46 disposed above the skirt 48.

[0092] With the assistance of the flared guide formation 58 shown in FIGS. 3 and 4, the skirt 48 of the sleeve 44 receives the upper end of the pipe string 20. The upper end of the pipe string 20 extends as far into the sleeve 44 as is allowed by the shoulder 56 between the skirt 48 and the body portion 46. This engagement seats the sleeve 44 on the upper end of the pipe string 20 via the tapering shoulder 56, which serves as an internal seating formation that cooperates with the skirt 48 to align the sleeve 44 with the pipe string 20. The lifting strap 66 is then detached from the body portion 46 of the sleeve 44.

[0093] Next, as shown in FIG. 5c, the travelling clamp 30 is lowered to surround the body portion 46 of the sleeve 44 that extends upwardly from the upper end of the pipe string 20. The travelling clamp 30 is then activated to clamp the body portion 46.

[0094] Optionally, after engaging the sleeve 44, the travelling clamp 30 may be lifted away from the upper workstation 22 and the stationary clamp 26. This will pull the sleeve 44, which remains fixed within the travelling clamp 30, off the upper end of the pipe string 20.

[0095] The stationary clamp 26 must continue to support the weight of the pipe string 20, as shown in FIG. 5c, until that load has been transferred to an A&R wire 40 that extends through the sleeve 44 in the travelling clamp 30.

[0096] It can be seen in FIG. 5d that the A&R wire 40 extends through the central lumen of the sleeve 44 in the travelling clamp 30 to a lifting fixing 68 that is locked into, and protrudes from, the open upper end of the pipe string 20. The lifting fixing 68 comprises a shackle 70 for attaching the A&R wire 40.

[0097] In FIG. 5d, the pads 64 of the stationary clamp 26 have been retracted radially outwardly away from the pipe string 20. This releases the pipe string 20 to transfer the suspended weight of the pipe string 20 to the A&R wire 40. The pipe string 20 can then be lowered on the A&R wire 40 through and beyond the stationary clamp 26 for abandonment as shown.

[0098] The lifting fixing 68 may be inserted into the upper end of the pipe string 20 before or after the sleeve 44 is lowered onto the pipe string 20 as shown in FIG. 5b. Additionally, the A&R wire 40 may be attached to the lifting fixing 68 before or after the lifting fixing 68 is engaged with the pipe string 20. The slots 62 and apertures 60 of the sleeve 44 shown in FIGS. 3 and 4 provide access to make and to check the necessary connections.

[0099] FIGS. 6a to 6c show how the sleeve 44 may be used to protect the stationary clamp 26.

[0100] FIG. 6a shows the sleeve 44 mounted on the upper end of the pipe string 20 as in FIG. 5b. An A&R wire 40 extends through the sleeve 44 to the pipe string 20, to which the A&R wire 40 may be secured via a lifting fixing 68 like that shown in FIG. 5d. The pads 64 of the stationary clamp 26 have been retracted to release the pipe string 20, whose weight load has thereby been transferred to the A&R wire 40 to start the abandonment operation.

[0101] The pipe string 20 and the sleeve 44 are shown in FIG. 6a being lowered together through the stationary clamp 26. Lowering continues until the body portion 46 of the sleeve 44 aligns with the pads 64 of the stationary clamp 26. Then, as shown in FIG. 6b, the stationary clamp 26 is closed again by extending its pads 64 to grip the body portion 46 of the sleeve 44.

[0102] In FIG. 6c, the pipe string 20 has been lowered further away from the sleeve 44 that remains fixed in the stationary clamp 26. The sleeve 44 protects the pads 64 of the stationary clamp 26 from clashing with the A&R wire 40 that supports the pipe string 20, as the A&R wire 40 continues to run through the sleeve 44 while abandonment continues.

[0103] FIGS. 7 and 8 show a variant of the invention in the form of a sleeve assembly 72, in which a sleeve 44 like that shown in FIGS. 3 and 4 is supplemented by an auxiliary sleeve 74. As will be explained, the auxiliary sleeve 74 can be held by the travelling clamp 30 and the sleeve 44 can be held by the stationary clamp 26. This variant therefore enables both clamps 26, 30 to be protected from an A&R wire 40 that runs through them during A&R operations.

[0104] In this example, the auxiliary sleeve 74 is a straight tube that surrounds the body portion 46 of the sleeve 44 in concentric and telescopic relation. Releasable fastenings 76 such as bolts secure the auxiliary sleeve 74 to the body portion 46.

[0105] FIGS. 9a to 9e show how the sleeve assembly 72 of FIGS. 7 and 8 may be used to protect both clamps 26, 30.

[0106] FIG. 9a shows the upper end of the pipe string 20 held by, and extending upwardly from, the stationary clamp 26. It will be noted that the pads 64 of the stationary clamp 26 are extended radially inwardly to grip the pipe string 20.

[0107] FIG. 9b shows the sleeve assembly 72 in an upright orientation mounted on the upper end of the pipe string 20. The skirt 48 of the sleeve 44 receives the upper end of the pipe string 20 in the same manner as shown in FIG. 4a. At this stage, the fastenings 76 secure the auxiliary sleeve 74 to the body portion 46 of the sleeve 44 as shown in FIG. 8. As before, an A&R wire 40 extends through the sleeve assembly 72 to the pipe string 20, to which the A&R wire 40 may be secured via a lifting fixing 68 like that shown in FIG. 5d.

[0108] In FIG. 9c, the fastenings 76 have been removed or released to free the auxiliary sleeve 74 from the body portion 46 of the sleeve 44. However, the auxiliary sleeve 74 remains securely supported on the shoulder 56 between the body portion 46 and the skirt 48 of the sleeve 44, as will be appreciated from FIG. 8.

[0109] FIG. 9c also shows the travelling clamp 30 lowered around the sleeve assembly 72. The pads 64 of the travelling clamp 30, shown here retracted, are then extended into engagement with the auxiliary sleeve 74. The auxiliary sleeve 74 thereby protects the pads 64 of the travelling clamp 30 from clashing with the A&R wire 40 that supports the pipe string 20 and runs through the auxiliary sleeve 74.

[0110] FIG. 9d shows the pads 64 of the stationary clamp 26 retracted to release the pipe string 20, whose weight load is thereby transferred to the A&R wire 40 to start the abandonment operation. The pipe string 20 is shown in FIG. 9d being lowered through the stationary clamp 26. This pulls the sleeve 44 mounted on the pipe string 20 down and out of engagement with the auxiliary sleeve 74, which remains fixed relative to the travelling clamp 30. Lowering continues until the body portion 46 of the sleeve 44 aligns with the pads 64 of the stationary clamp 26. Then, as shown in FIG. 9e, the stationary clamp 26 is closed again by extending its pads 64 to grip the body portion 46 of the sleeve 44.

[0111] FIG. 9e shows the pipe string 20 having been lowered further away from the sleeve 44 that remains fixed in the stationary clamp 26. The sleeve 44 protects the pads 64 of the stationary clamp 26 from clashing with the A&R wire 40 as abandonment continues.

[0112] FIG. 10 shows a further variant of a sleeve assembly 78 of the invention. In this example, releasable fastenings 76 mount the auxiliary sleeve 74 on the free end of the body portion 46 of the sleeve 44. This arrangement allows the auxiliary sleeve 74 to have a similar outer diameter to that of the body portion 46. It will be apparent to the skilled reader that the sleeve assembly 78 shown in FIG. 10 can be used in the same way as the sleeve assembly 72 shown in FIGS. 9a to 9e to protect both of the clamps 26, 30 from an A&R wire 40 running within them.

[0113] Turning finally to FIGS. 11 to 14, these drawings show a cap 80 that may be mounted on the upper end of the pipe string 20 as a buffer to provide a resilient interface between the pipe string 20 and the sleeve 44.

[0114] The cap 80 shown in FIGS. 11 to 14 is an annular, ring-shaped structure that is rotationally symmetrical around a central longitudinal axis 50. A circular central opening 82 provides access to the interior of the pipe string 20 for a lifting fixing 68 as shown in preceding drawings.

[0115] A skirt-like flange 84 is a longitudinally-extending peripheral formation that surrounds the cap 80 to receive the upper end of the pipe string 20 as shown in FIG. 11. The diameter of the central opening 82 is less than the inner diameter of the flange 84, hence defining a flat annular bearing surface 86 around the central opening 82 that sits on the upper end of the pipe string 20 as shown in FIG. 11. The bearing surface 86 is in a plane that is substantially orthogonal to the central longitudinal axis 50.

[0116] The upper side of the cap 80 has a chamfered circumferential edge 88. The inclination of the chamfer with respect to the central longitudinal axis 50 substantially matches that of the shoulder 56 between the body portion 46 and the skirt 48 of the sleeve 44. Thus, as will be appreciated from FIG. 11, the chamfered edge 88 complements and bears against the shoulder 56 to seat the sleeve 44 securely onto the upper end of the upright pipe string 20.

[0117] The cap 80 shown in FIGS. 11 and 12 is of a dense, solid plastics material such as ultra-high molecular weight polyethylene, or UHMWPE.

[0118] The variant of the cap 80 shown in FIGS. 12 and 14 has a layered construction of polymer materials supported by a metal core. Specifically, the central opening 82 is defined by an annular metallic top plate 90 that is sandwiched by annular layers or rings 92 of a dense, solid plastics material such as UHMWPE. The flange 84 comprises a metallic outer ring 94 welded to the top plate 90 and an inner ring 96 of a resilient material such as neoprene. The dense rings 92 that sandwich the top plate 90 bear the weight of the sleeve 44 while the resilience of the inner ring 96 of the flange 84 helps to retain the cap 80 on the upper end of the pipe string 20.

[0119] Many variations are possible within the inventive concept. For example, the sleeve and/or the auxiliary sleeve may have convex-curved, radiused or flared ends or a convex-curved internal profile to facilitate smooth running of the A&R wire within.

[0120] In preparation for a recovery operation, a sleeve and/or an auxiliary sleeve may be brought level with a travelling clamp and/or a stationary clamp and then clamped there before running an A&R wire through the sleeve or auxiliary sleeve. For example, the sleeve or auxiliary sleeve may be raised or lowered to the level of the clamp by a winch or crane, and/or the travelling clamp may be raised or lowered to the level of the sleeve or auxiliary sleeve.

[0121] In principle, the invention could be used when laying subsea pipes other than rigid pipes, such as flexible pipes or composite pipes, or indeed elongate subsea elements other than pipes, such as cables or umbilicals. The invention could also be used with hang-off clamp systems that do not rely upon friction.