SUBSEA WELLBORE OPERATIONS VESSEL

Abstract

A vessel is adapted to perform subsea wellbore related operations involving a riser string between the subsea wellbore and the vessel, e.g. drilling and/or wellbore intervention. The vessel includes a hull having a deck, and a riser storage hold present within the hull below the deck. The riser storage hold includes storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation. The vessel has an elongated riser transfer opening between the deck and the roof, the riser transfer opening extending in a direction parallel to the storage racks, the riser transfer opening having a length and a width so as to allow for transfer of a single riser section or a single riser stand in horizontal orientation via the riser transfer opening out of and into the riser storage hold, wherein the risers' handling system is suitable to work at the same time with two different lengths.

Claims

1.-24. (canceled)

25. A vessel adapted to perform subsea wellbore related operations involving a riser string between the subsea wellbore and the vessel, said vessel comprising: a hull having a deck; a riser storage hold present within said hull below said deck, said riser storage hold comprising storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in a horizontal orientation, and said riser storage hold having a floor, side walls, and a roof; an elongated riser transfer opening between said deck and said roof, said riser transfer opening extending in a direction parallel to said storage racks, said riser transfer opening having a length and a width so as to allow for transfer of a single riser section or a single riser stand in said horizontal orientation thereof via said riser transfer opening out of and into the riser storage hold; a riser transfer station arranged within said riser storage hold below said riser transfer opening and provided with a transfer elevator that is adapted to raise and lower a single riser section or a single riser stand in said horizontal orientation thereof so as to pass the riser section or a riser stand through the riser transfer opening; and a first overhead travelling beam crane arranged within the riser storage hold, said first overhead travelling beam crane being adapted to lift and lower a single riser section or a single riser stand at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section or a single riser stand into a storage rack respectively, and said first crane being adapted for transverse transportation of a single riser section or a single riser stand at least between said transfer station and a position above a storage rack, wherein said first overhead travelling beam crane comprises: a travelling beam extending in a direction parallel to said storage racks and supported at each end thereof on a crane rail extending perpendicular to said storage racks; a winch trolley provided with one or more winches and displaceable along said travelling beam; and an elongated gripper frame suspended by one or more winch driven cables from said winch trolley, said gripper frame being provided with multiple riser grippers adapted to engage on a single riser section or a single riser stand at spaced gripping locations thereof, wherein the riser storage hold is provided with first length storage racks adapted to store therein single first length riser sections and/or pre-assembled riser stands each having a length of at least 100 ft. (30.48 m), wherein the riser storage hold is provided with second length storage racks adapted to store therein single second length riser sections each having a length of between 50 ft. (15.24 meters) and 90 ft. (27.43 meters), and wherein the first overhead travelling beam crane is adapted to transfer a second length riser section between each of said second length storage racks and the transfer station, and to transfer a first length riser section or riser stand between each of said first length storage racks and the transfer station.

26. The vessel according to claim 25, wherein the transfer elevator comprises a first elevator unit and a second elevator unit that are spaced apart in direction parallel to said storage racks, wherein each of said first and second elevator units are adapted to selectively operate stand-alone or in unison, wherein, for operating stand-alone, each elevator unit is adapted to raise and lower a second length riser section, and wherein, for operating in unison, said first and second elevator units are further adapted to raise and lower a first length riser section or single riser stand.

27. The vessel according to claim 26, wherein each elevator unit comprises a vertical guide structure which is stationary mounted in said storage hold, and a telescoping member which is guided by said vertical guide structure, wherein the elevator unit further comprises a winch and a winch driven cable connected to said telescoping member to cause vertical motion thereof, and wherein a riser support member is mounted on said telescoping member and is adapted to support a riser section or riser stand.

28. The vessel according to claim 25, wherein a first group of first length storage racks is arranged adjacent one side of the transfer station and a second group of first length storage racks is arranged adjacent another side of the transfer station, and wherein a first group of second length storage racks is arranged along said first group of first length storage racks and wherein a second group of second length storage racks is arranged along said second group of first length storage racks.

29. The vessel according to claim 25, wherein the riser storage hold is provided with at least one elongated riser workshop having a floor and walls and a roof, said riser workshop being arranged parallel to the storage racks and the workshop being adapted to accommodate at least one riser section or riser stand in horizontal orientation, the workshop providing an enclosure for personnel performing work on the riser section or riser stand, and wherein the first overhead travelling beam crane is adapted to place a riser in the workshop and remove a riser from the workshop.

30. The vessel according to claim 29, wherein a first elongated riser workshop and a second elongated riser workshop are arranged in the riser storage hold, along opposite sides of the storage racks, with the transfer station centrally between storage racks.

31. The vessel according to claim 25, wherein the riser storage hold is provided with a second overhead travelling beam crane arranged within the riser storage hold, said second overhead travelling beam crane being adapted to lift and lower a single riser section or a single riser stand at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section or a single riser stand into a storage rack respectively, and said second overhead travelling beam crane being adapted for transverse transportation of a single riser section or a single riser stand at least between said transfer elevator and a position above a storage rack, wherein said second overhead travelling beam crane comprises: a second travelling beam extending in a direction parallel to said storage racks and supported at each end thereof on the same crane rail as the first overhead travelling beam crane; a second winch trolley provided with one or more winches and displaceable along said travelling beam; and an elongated gripper frame suspended by one or more winch driven cables from said winch trolley, said gripper frame being provided with multiple riser grippers adapted to engage on a single riser section or a single riser stand at spaced gripping locations thereof.

32. The vessel according to claim 31, wherein a first elongated riser workshop and a second elongated riser workshop are arranged in the riser storage hold, at least one of said first and second riser workshops being arranged along a side of the riser storage hold, and wherein the second travelling beam crane has a parking position above said workshop along the side of the riser storage hold.

33. The vessel according to claim 25, wherein the gripper frame is provided with two riser grippers that are adapted and arranged to engage on the end portions of second length riser section.

34. The vessel according to claim 25, wherein the gripper frame is provided, at each end thereof, with a telescoping extender having an extender end, which extender is extensible so that the extender end is adjacent an end of a first length riser section or riser stand, wherein each first length storage rack comprises at ends thereof a pair of adjacent riser end support columns that form a vertical slot which is adapted to receive therein an end portion of a riser section or riser stand, and wherein the extender end is adapted to be slidingly received between said riser end support columns.

35. The vessel according to claim 25, wherein substantially horizontal rails extend along opposite longitudinal sides of the riser transfer opening, and wherein the vessel comprises a riser horizontal transport device that is mounted on said horizontal rails and is adapted to receive and hold a riser section or riser stand that has been raised through said transfer opening by the riser elevator and to horizontally transport the riser section or riser stand so that a leading end thereof is connectable to a riser string lifting tool that is adapted to support the weight of a riser string in a firing line of the vessel.

36. The vessel according to claim 35, wherein the riser horizontal transport device comprises a catwalk machine having a mobile catwalk machine frame that is movable over said horizontal rails, wherein the catwalk machine frame has a rear end and a front end, and is movable over the horizontal rails at least in a loading position and in a riser upending position, wherein the catwalk machine frame has two parallel and horizontal frame beams, and wherein a skate is supported by said frame beams and travels over said frame beams, wherein the skate comprises a riser end support to support thereon a rearward end of a riser section or riser stand that are each supported on a respective horizontal rails, wherein the horizontal frame beams of the catwalk machine frame define between them an opening having a width so as to allow for the vertical passing of a single riser section or a single riser stand in said horizontal orientation thereof through said opening by means of the transfer elevator, and wherein the catwalk machine, in addition to the skate, comprises one or more additional riser support members that are movable between an inactive position allowing for said vertical passage of the single riser section or single riser stand and an active position wherein the riser section or riser stand is supported on said riser support member.

37. The vessel according to claim 36, wherein the frame beams are rigidly interconnected by a transverse beam near a rear end of the catwalk machine frame, and wherein the frame beams are interconnected by one or more mobile transverse connectors that are each movable between an inactive position allowing for said vertical passage of the single riser section or single riser stand and an active position wherein the transverse connector interconnects the frame beams.

38. The vessel according to claim 36, wherein the vessel is provided with one or more movable hatches which in a closed position thereof close the transfer opening and in an opened position thereof open the transfer opening, wherein a first set of pivotal hatches is arranged along one longitudinal side of the transfer opening and a second set of pivotal hatches is arranged along an opposed longitudinal side of the transfer opening, so that with said hatches in horizontal position the transfer opening is closed and with said hatches in an upward pivoted position the transfer opening is open, and wherein, in upward pivoted position, said hatches are to the outside of the horizontal rails at a spacing allowing for the travel of the catwalk machine over said horizontal rails between said upward pivoted hatches.

39. A vessel adapted to perform subsea wellbore related operations involving a riser string between a subsea wellbore and the vessel, said vessel comprising: a hull having a deck; and a riser storage hold present within said hull below said deck, said riser storage hold comprising storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation, and said riser storage hold having a floor, side walls, and a roof, wherein the riser storage hold is provided with first length storage racks adapted to store therein single first length riser section and/or pre-assembled riser stands each having a length of at least 100 ft. (30.48 m), wherein the riser storage hold is provided with second length storage racks adapted to store therein single second length riser sections each having a length of between 50 ft. (15.24 meters) and 90 ft. (27.43 meters), and wherein two second length storage racks are arranged in line with each other, parallel to said first length storage racks.

40. A vessel adapted to perform subsea wellbore related operations involving a riser string between a subsea wellbore and the vessel, said vessel comprising: a hull having a deck; a riser storage hold present within said hull below said deck, said riser storage hold comprising storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation, and said riser storage hold having a floor, side walls, and a roof; and a first overhead travelling beam crane arranged within the riser storage hold, said first crane being adapted to lift and lower a single riser section or a single riser stand at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section or a single riser stand into a storage rack respectively, and said crane being adapted for transverse transportation of a single riser section or a single riser stand at least between said transfer elevator and a position above a storage rack, wherein said first overhead travelling beam crane comprises: a travelling beam extending in a direction parallel to said storage racks and supported at each end thereof on a crane rail perpendicular to said storage racks; a winch trolley provided with one or more winches and displaceable along said travelling beam; and an elongated gripper frame suspended by one or more winch driven cables from said winch trolley, said gripper frame being provided with multiple riser grippers adapted to engage on a single riser section or a single riser stand at spaced gripping locations thereof, wherein the riser storage hold is provided with a second overhead travelling beam crane arranged within the riser storage hold, said second overhead travelling beam crane being adapted to lift and lower a single riser section or a single riser stand at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section or a single riser stand into a storage rack respectively, and said second overhead travelling beam crane being adapted for transverse transportation of a single riser section or a single riser stand at least between said transfer elevator and a position above a storage rack, and wherein said second overhead travelling beam crane comprises: a second travelling beam extending in a direction parallel to said storage racks and supported at each end thereof on the same crane rail as the first overhead travelling beam crane; a second winch trolley provided with one or more winches and displaceable along said travelling beam; and an elongated gripper frame suspended by one or more winch driven cables from said winch trolley, said gripper frame being provided with multiple riser grippers adapted to engage on a single riser section or a single riser stand at spaced gripping locations thereof.

41. A vessel adapted to perform subsea wellbore related operations involving a riser string between a subsea wellbore and the vessel, said vessel comprising: a hull having a deck; a riser storage hold present within said hull below said deck, said riser storage hold comprising storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation, and said riser storage hold having a floor, side walls, and a roof; an elongated riser transfer opening between said deck and said roof, said elongated riser transfer opening extending in a direction parallel to said storage racks, and said elongated riser transfer opening having a length and a width so as to allow for transfer of a single riser section or a single riser stand in a horizontal orientation via said riser transfer opening out of and into the riser storage hold; a riser transfer station arranged within said riser storage hold and provided with a transfer elevator that is adapted to raise and lower a single riser section or a single riser stand in said horizontal orientation thereof so as to pass the single riser section or a single riser stand through the riser transfer opening; and a crane arranged within the riser storage hold, said crane being adapted to lift and lower a single riser section or a single riser stand at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section or a single riser stand into a storage rack respectively, and said crane being adapted for transverse transportation of a single riser section or a single riser stand at least between said transfer elevator and a position above a storage rack, wherein the riser storage hold is adapted to store therein single first length riser section and/or pre-assembled riser stands each having a length of at least 100 ft. (30.48 m), wherein the riser storage hold is adapted to store therein single second length riser sections each having a length of between 50 ft. (15.24 meters) and 90 ft. (27.43 meters), and wherein the transfer elevator comprises a first elevator unit and a second elevator unit that are spaced apart in a direction parallel to said storage racks, wherein each of said first and second elevator units are adapted to selectively operate stand-alone or in unison, wherein, for operating stand-alone, each elevator unit is adapted to raise and lower a second length riser section, and wherein, for operating in unison, said first and second elevator units are further adapted to raise and lower a first length riser section or single riser stand.

42. A vessel adapted to perform subsea wellbore related operations involving a riser string between a subsea wellbore and the vessel, said vessel comprising: a hull having a deck; a riser storage hold present within said hull below said deck, said riser storage hold comprising storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation, and said riser storage hold having a floor, side walls, and a roof; an elongated riser transfer opening extending between said deck and said roof, said elongated riser transfer opening being a parallel to said storage racks, and said elongated riser transfer opening having a length and a width so as to allow for transfer of a single riser section or a single riser stand in horizontal orientation via said riser transfer opening out of and into the riser storage hold; and a riser transfer station arranged within said riser storage hold and provided with a transfer elevator that is adapted to raise and lower a single riser section or a single riser stand in horizontal orientation thereof so as to pass the single riser section or a single riser stand through the riser transfer opening, wherein a first elongated riser workshop and a second elongated riser workshop are arranged in the riser storage hold, the first and second workshop each being arranged along a side of the storage hold, the storage racks being positioned between said first and second workshops, and wherein each riser workshop is arranged parallel to the storage racks and the workshop is adapted to accommodate at least one riser section or riser stand in horizontal orientation, the workshop providing a space for personnel performing work on a riser section or a riser stand, wherein the vessel comprises a crane is adapted to place a riser in the workshop and remove a riser from the workshop.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0141] In the drawings:

[0142] FIG. 1 shows in longitudinal view a vessel according to the invention,

[0143] FIG. 2 shows a plan view of the aft part of the vessel of FIG. 1,

[0144] FIG. 3 shows schematically a step in a riser upending process of the vessel of FIG. 1,

[0145] FIG. 4 shows a transverse section of the vessel of FIG. 1 showing the riser storage hold, the riser transfer elevator, the overhead cranes,

[0146] FIG. 5 shows a horizontal section of the riser storage hold of the vessel of FIG. 1,

[0147] FIG. 6 shows on a larger scale a portion of FIG. 5,

[0148] FIG. 7a illustrates a transfer elevator unit holding a riser section in raised condition,

[0149] FIG. 7b illustrates the transfer elevator unit in inoperative condition,

[0150] FIG. 8 illustrates the use of two transfer elevator units in unison for handling a first length riser section,

[0151] FIG. 9 shows a portion of FIG. 8 on a larger scale,

[0152] FIG. 10 illustrates the use of a single transfer elevator unit in stand-alone mode for handling a second length riser section,

[0153] FIG. 11 illustrates the provision of a hook as gripper engageable portion on a first length riser section,

[0154] FIG. 12 illustrates the provision of a hook as gripper engageable portion at the end of a second length riser section,

[0155] FIG. 13 illustrates an overhead crane handling a first length riser section in the storage hold of the vessel of FIG. 1,

[0156] FIG. 14 shows the overhead crane of FIG. 13 from above,

[0157] FIG. 15a shows the winch trolley and gripper frame of the crane of FIG. 13 when handling a second length riser section,

[0158] FIG. 15b shows the gripper frame of FIG. 15a from above,

[0159] FIG. 16a shows the winch trolley and gripper frame of the crane of FIG. 13 when handling a first length riser section with the extenders in extended position,

[0160] FIG. 16b shows the gripper frame of FIG. 16a from above,

[0161] FIG. 17 illustrates the handling of second length riser sections in the storage hold by means of the crane of FIG. 13,

[0162] FIG. 18 illustrates the catwalk machine, transfer opening and associated hatches of the vessel of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

[0163] FIG. 1 shows a mono-hull vessel 1 having a hull 2 with a bow 3, a stern 4, and a moonpool 5 that extends through the hull 1.

[0164] The vessel 1 is adapted to perform subsea wellbore related operations involving a riser string between the subsea wellbore and the vessel, in particular drilling operations, e.g. for exploratory drilling. The vessel can also perform other subsea wellbore related operations, e.g. wellbore intervention.

[0165] In this example, the vessel 1 has an accommodation topside 6 at the bow 3, including crew quarters and a bridge.

[0166] The vessel 1 has an engine room 7, generally below the accommodation topside, with exhausts 7a extending at the rear of the topside 6, above the topside 6.

[0167] The moonpool 5 has, as is preferred, a rectangular shape with opposed lateral sides, a front side and a rear side.

[0168] A front main deck 8 extends between the moonpool 5 and the topsides.

[0169] A rear main deck 9 extends between the moonpool 5 and the stern of the vessel 4.

[0170] The vessel is equipped with a tower 10, which is, as is preferred, embodied as a hollow construction mast having a top 11 and having a base 12 that is integral with the hull 2. The base 12 extends between sections of the hull on opposed lateral sides of the moonpool 5 and the base 12 is spaced from each of the front side and the rear side of the moonpool, thereby forming a front moonpool area 5a forward of the mast 10 and a rear moonpool area 5b rearward of the mast 10.

[0171] The mast 10 has a front side and an opposed rear side 10b as well as opposed lateral sides.

[0172] In this example, drill pipe racks, here embodied as carrousel type racks 14, are located adjacent the lateral sides of the mast 10, as is known in the art.

[0173] At the rear moonpool area, the vessel is provided with a working deck 15 arranged above the rear moonpool area 5b. As is preferred the working deck 15 is a mobile working deck, here liftable along the mast 10 to such a height that a blow-out preventer can be brought and held underneath the working deck 15 in raised position thereof at an elevated position relative to the mast 10. In a lowered, operative position, the working deck 15 preferably, as here, is level with the adjacent main deck area.

[0174] In view of assembly and disassembly of a riser string along a firing line 20 through the rear moonpool area 5b the vessel is equipped with a riser string assembly hanger 17 that is adapted to suspended therefrom a riser string in the firing line 20 into the sea during the riser assembly and disassembly process. As preferred, this hanger 17 is mounted on the working deck 15, e.g. embodied as a riser spider, e.g. provided with a gimballing support so as to allow for angular variation between the riser string and the working deck, e.g. due to sea motion of the vessel.

[0175] The vessel 1 has a riser string handling capacity hoisting device including a riser string lifting tool 25 which is movable up and down relative to the mast 10 and that is adapted to connect to an end of a riser section, preferably of a pre-assembled riser stand as will be explained below, and is embodied to support the weight of a riser string in the firing line 20 when released from the riser string assembly hanger 17.

[0176] The riser string lifting tool 25 here is suspended from a travelling hanger device 26 that is movable up and down along the rear side of the mast 10 along one or more vertical rails 27.

[0177] The hanger device 26 is suspended by one or more cables 28 from a sheave arrangement 29 at the top of the mast, which one or more cables 28 are connected to one or more winches 29a, e.g. arranged within the mast 10.

[0178] It is noted that the firing line 20 is outside of the rear side 10b of the mast 10 so that the firing line 20 can be reached without hindrance in the process of upending a riser section or riser stand from the rear of the vessel.

[0179] In an alternative embodiment, the mast 10 is replaced by a derrick type tower having a latticed frame with corner posts that forms a frame extending over the moonpool. It is then envisaged that the riser storage is outside of the derrick type tower and the derrick is provided with a V-door or similar to allow passage of a riser section or riser stand into and out of the derrick.

[0180] The vessel also has a second hoisting device having a load attachment device 30 which is movable up and down relative to the mast at a side opposed from the riser firing line 20, so as to allow for handling of items passing through the other moonpool area along a second firing line 21 distinct and spaced from the first firing line 20 where the riser string assembly takes place.

[0181] The second firing line 21 extends through the front moonpool area 5a. Along this firing line 21 primarily drilling operations are performed.

[0182] The second hoisting device is embodied as a drilling drawworks, and is provided with a topdrive 31 suspended from the load attachment device 30 to perform drilling operations. The load attachment device 30 is preferably embodied similar as the travelling hanger device 26.

[0183] A working deck 32 is arranged above the moonpool area 5a and may include a rotary table, iron roughneck machine, etc.

[0184] The vessel 1 is thus capable of assembly of a riser string in firing line 20. For transfer of the riser string to the other firing line 21 a riser string support cart 35 is provided that is displaceable within the moonpool, e.g. skiddable over rails along the lateral sides of the moonpool 5.

[0185] The vessel has a riser storage hold 40, here as is preferred, within the hull 2 aft of the moonpool 5.

[0186] The riser storage hold 40 comprises storage racks adapted to store therein parallel stacks of multiple riser sections and/or pre-assembled riser stands in horizontal orientation.

[0187] The riser storage hold is provided with first length storage racks 80 adapted to store therein single first length riser sections 85 and/or pre-assembled riser stands each having a length of at least 100 ft. (30.48 m), e.g. of 120 ft. (36.57 m) or 150 ft. (45.72 m). In the example depicted in the figures the first length is 150 ft.

[0188] The riser storage hold is provided with second length storage racks 90 adapted to store therein single second length riser sections 95 each having a length of between 50 ft. (15.24 meters) and 90 ft. (27.43 meters), e.g. of 75 ft. (22.86 meters). In the example depicted in the figures the second length is 75 ft.

[0189] The second length storage racks 90 are arranged in sets of two arranged, with the two racks 90 being in line with one another and parallel to the adjacent longer first length storage racks 80.

[0190] A first group of first length storage racks 80 is arranged adjacent one side of the transfer station 50 and a second group of first length storage racks 80 is arranged adjacent another side of the transfer station 50.

[0191] A first group of second length storage racks 90 is arranged along the first group of first length storage racks and a second group of second length storage racks 90 is arranged along said second group of first length storage racks.

[0192] Each storage rack 80, 90 comprises at ends thereof a pair of adjacent riser end support columns that form a vertical slot which is adapted to receive therein an end portion, e.g. a flange, of a riser section 85, 95.

[0193] The riser storage hold has a floor 40a, port and starboard side walls 40b,c, and a roof 41.

[0194] An elongated riser transfer opening 45 is present between the deck 9 and the roof 41.

[0195] The riser transfer opening 45 extends in a direction parallel to the storage racks and has a length, here of at least 150 ft., and a width so as to allow for transfer of a single riser section or a single riser stand in horizontal orientation via the riser transfer opening out of and into the riser storage hold.

[0196] Within the storage 40 a riser transfer station 50 is arranged below the riser transfer opening 45. The station is provided with a transfer elevator that is adapted to raise and lower a single riser section or a single riser stand in horizontal orientation thereof so as to pass the riser section or a riser stand through the riser transfer opening 45.

[0197] In the storage hold 40 a first overhead travelling beam crane 60 is arranged.

[0198] The crane 60 is capable of lifting and lowering a single riser section 85,95, either of first length or of second length as described herein, as well as a single pre-assembled first length riser stand as described herein, at least allowing for removal of a single riser section or a single riser stand riser stand from a storage rack and for placing a single riser section 85, 95 or a single riser stand into a storage rack respectively. The crane 60 is also capable of transverse transportation of a single riser section 85, 95 or a single riser stand at least between the transfer station 50 and a position above each of the storage racks 80, 90 in the storage 40.

[0199] The first crane 60 comprises: [0200] a travelling beam 61 extending in a direction parallel to the storage racks and supported at each end thereof on a crane rail 62, 63 perpendicular to the storage racks, here transverse to the hull 2, [0201] a winch trolley 65 provided with one or more winches 66, 67 and displaceable along the travelling beam 61, [0202] an elongated gripper frame 68 suspended by one or more winch driven cables 69a, 69b from the winch trolley, 65. The gripper frame 68 is provided with multiple riser grippers 70a, b that are each adapted to engage on a single riser section 85, 95 or a single riser stand at spaced gripping locations thereof.

[0203] The gripper frame 68 is provided with two riser grippers 70a, b that are adapted and arranged to engage on the end portions of second length riser section 95, here on end portions of a 75 ft. riser section.

[0204] The first length riser sections 85 are provided at intermediate locations along the length thereof with two riser gripper engageable portions, here hooks 140, having a spacing the same as the spacing between end portions of a second length riser section 95 so as to allow said two riser grippers 70a, b to engage on said gripper engageable portions 140 of the first length riser section 85.

[0205] The gripper frame 68 is provided, at each end thereof, with a telescoping extender 68a, b having an extender end. Each extender 68a, b is extensible so that the extender end is adjacent the end of a first length riser section 85 or riser stand. The end is dimensioned to be slidable received between two columns of a storage rack in order to guide the gripper frame and riser during vertical travel.

[0206] The crane 60 is adapted to transfer a second length riser section 95 between each of the second length storage racks 80 and the transfer station 50, and to transfer a first length riser section 85 or riser stand between each of the first length storage racks 90 and the transfer station 50.

[0207] The transfer elevator comprises a first elevator unit 55 and a second elevator unit 55, as is preferred of the same design. These units 55 are spaced apart in direction parallel to the storage racks.

[0208] Each of the elevator units 55 is adapted to selectively operate stand-alone or in unison. In stand-alone mode each elevator unit 55 is adapted to raise and lower a second length riser section (FIG. 10). When operating in unison the elevator units 55 raise and lower a first length riser section or single riser stand together (FIGS. 8,9).

[0209] Each elevator unit 55 comprises a vertical guide structure 56, stationary mounted in the storage hold 40. Further a telescoping member 57 is provided, which is guided by the vertical guide structure 56. The elevator unit further comprises a winch 58 and winch driven cable 59 connected to the telescoping member 57 to cause vertical motion thereof. A riser support member 55a is mounted on the telescoping member 57 and is adapted to support a riser section 85, 95 or riser stand.

[0210] The riser support member is a riser support table 55a having a length of between 20 and 50 ft.

[0211] The riser support member 55a is pivotally connected to the telescoping member 57 and is tiltable, her by hydraulic cylinder, between a horizontal operation position wherein a riser section or riser stand can rest on said riser support member and a vertical inoperative storage position (see FIGS. 7a, 7b).

[0212] The riser storage hold 40 is provided with a first elongated riser workshop 110 and a second elongated riser workshop 120, each having a length at least sufficient to receive therein a first length riser section or stand. Each riser workshop has a floor, and, as is preferred also walls and a roof.

[0213] Each riser workshop 110, 120 is arranged parallel to the storage racks and the workshop is adapted to accommodate at least one riser section 85, 95 or riser stand in horizontal orientation. The workshop provides an enclosure for personnel performing work on the riser section, e.g. maintenance and/or inspection of the riser section and/or interconnecting sections to form a pre-assembled stand.

[0214] The overhead travelling beam crane 60 is adapted to place a riser section 85, 95 in each of the workshops 110, 120 and remove a riser section from the workshop. In this example it is envisaged that the workshops 110, 120 have a roof with a riser transfer opening therein, preferably said opening being provided with a mobile roof cover, e.g. one or more hatches or a tarpaulin.

[0215] As can be seen the workshops 110, 120 are arranged along the port and starboard sides of the hold 40, along opposite sides of the storage racks 80, 90. The transfer station 50 is arranged centrally between storage racks 80, 90.

[0216] The riser storage hold is provided with a second overhead travelling beam crane 60′ which is provided to obtain a redundant crane system for handling riser sections 85, 95. The crane 60′ is preferably of the same design as the crane 60. The travelling beam of crane 60′ preferably travels on the same crane rails 62, 63 as the first overhead travelling beam crane 60.

[0217] The second travelling beam crane 60′ here has a parking position above one of the workshops, here at 120, which workshop 120 preferably is located along a side of the riser storage hold.

[0218] FIG. 4 shows that a further parking position is available for the crane 60 above the other workshop 110, e.g. allowing to park crane 60 there when servicing is required and crane 60′ then has full access to all riser sections stored in the storage racks.

[0219] The vessel is provided with movable hatches which in a closed position thereof close the transfer opening 45 and in an opened position thereof open the transfer opening. e.g. pivotal hatches 130a, 130b.

[0220] Substantially horizontal rails 150 extend along opposite longitudinal sides of the riser transfer opening 45.

[0221] The vessel comprises a riser horizontal transport device 200 that is mounted on horizontal rails 150 and is adapted to receive and hold a riser section 85, 95 or riser stand that has been raised through said transfer opening 45 by the riser elevator unit or units 55 and to horizontally transport the riser section 85, 95 or riser stand so that a leading end thereof is connectable to a riser string lifting tool that is adapted to support the weight of a riser string in the firing line 20 of the vessel.

[0222] The riser horizontal transport device comprises a catwalk machine having a mobile catwalk machine frame that is movable over the horizontal rails 150. The catwalk machine frame has a rear end and a front end and is movable over the horizontal rails 150 at least in a loading position generally above the opening 45 and in a riser upending position closer to the firing line 20.

[0223] The catwalk machine frame has two parallel and horizontal frame beams 201, 202. At the rear end the beams 201, 202 are rigidly and permanently interconnected by a transverse beam 203. The beams 201, 202 are less long than the transfer opening 45 and the first length riser section or stand that is stored in the hold 40. In order to obtain a sturdy frame during transportation of the riser section it is envisaged that, here only at the front end, the frame beams 201, 202 are interconnected by a mobile transverse connector 204 that is movable between an inactive position allowing for vertical passage of the single riser section or single riser stand and an active position wherein the transverse connector 204 interconnects the frame beams 201, 202. When lifting and lowering a section of first length the connector 204 is inactive or opened. A shorter second length may be handled with the connector remaining closed as the opening in the frame of the machine is then large enough.

[0224] A skate 205 is supported by the frame beams 201, 202 and travels over the frame beams. As is known in the art the skate 205 comprises a riser end support to support thereon a rearward end of a riser section 85, 95 or riser stand.

[0225] As will be appreciated the horizontal frame beams 201, 202 of the catwalk machine frame define between them an opening having a width so as to allow for the vertical passing of a single riser section 85, 95 (equipped with buoyancy members) or a single riser stand in horizontal orientation through said opening, preferably by means of the transfer elevator unit or units 55.

[0226] The catwalk machine, in addition to the skate 205, comprises one or more additional riser support members 206 that are movable between an inactive position allowing for said vertical passage of the single riser section 85, 95 or single riser stand and an active position wherein the riser section or riser stand is supported on said riser support member 206.

[0227] If desired the catwalk machine 200 is provided with a tailing-in arm device, e.g. with one tailing arm fitted to the front end of each beam 201, 202.

[0228] As can be seen in FIG. 18 a first set of pivotal hatches 130a,b is arranged along one longitudinal side of the transfer opening 45 and a second set of pivotal hatches 130a, b is arranged along the opposed longitudinal side of the transfer opening 45, so that with said hatches 130a, b in horizontal position the transfer opening 45 is closed and with said hatches in upward pivoted position the transfer opening 45 is open.

[0229] As can be seen—in upward pivoted position—these hatches 130a, b are to the outside of the horizontal rails 150 at a spacing allowing for the travel of the catwalk machine 200 over said horizontal rails 150 between said upward pivoted hatches.