BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view illustrating a riser constructed in accordance with this invention.
FIG. 2 is a sectional view of a connection system for a riser joint with a latch segment in the open position.
FIG. 3 is a sectional view of the connection system of FIG. 1 with the latch segment in the closed position.
FIG. 4 is a schematic view illustrating a riser constructed in accordance with this invention, including the actuation lock.
FIG. 5 is a schematic view illustrating the actuation lock in the open position.
FIG. 6 is a schematic view illustrating the actuation lock in the locked position.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a riser 11 is schematically shown extending from a floating platform 13. Platform 13 is illustrated schematically and can be any type, such as a spar, tension leg platform, mobile offshore drilling unit, or the like. Riser 11 is a drilling riser used to drill offshore wells and is particularly for use in applications where the blowout preventer is located at the surface. The drilling riser may be submerged for several years at a time, such as for use on a spar platform. The drilling riser may also be recovered after drilling each well, such as on a tension leg platform.
Riser 11 is made up of a plurality of high pressure riser joints 15, each approximately 60 feet in length. A blowout preventer 17 is shown schematically at the upper end of riser 11. A subsea tieback assembly 19 is shown schematically at the lower end of riser 11 although blowout preventer 17 can also be at the lower end. Locating blowout preventer 17 at the platform or near the surface has significant advantages but in such a case riser 11 has to be able to withstand high internal pressure. Subsea tieback assembly 19 may incorporate a quick disconnect mechanism as well as a hydraulic connector on its lower end that connects it to a subsea wellhead assembly. Subsea tieback assembly 19 is not normally equipped to seal around drill pipe.
Referring to FIG. 2, a first high pressure drilling riser joint 21 is fitted with a housing assembly 23, referred to as a box, and a second high pressure drilling riser joint 25 is fitted with a pin assembly 27. Box 23 slides over pin 27. Box 23 contains an internal split pivoting latch segment assembly. Preferably the latch ring assembly combines a plurality of separate segments 29, for example twelve, spaced around box 23. One end of each latch segment 29 contains a grooved profile 31 that mates with a corresponding profile 33 on pin assembly 27. Profiles 31 and 33 may have a saw tooth pattern or an alternative pattern. A second end 35 of latch segment 29 engages a shoulder 37 of box 23. Second end 35 is a curved, convex surface and shoulder 37 is a curved concave shoulder. This arrangement allows latch segment 29 to rock between the open position of FIG. 2 and the engaged position of FIG. 3.
Turning to FIG. 3, in order to secure riser 21 to riser 25, a split actuation ring 41 is repositioned inside cavity 39 of box 23, forcing profile 31 of latch segment 29 into engagement with profile 33 of pin 27 by rotating latch segment 29 about end 35. Actuation ring 41 has a curved convex inner side that slides along the convex outer surface of latch segment 29 as can be seen by comparing FIGS. 2 and 3. Actuation ring 41 may be fabricated in multiple segments that are then mated to create a full ring around the inner concave surface of cavity 39. The curvature of the convex inner surface of actuation ring 41 and the curvature of convex outer surface of latch segment 29 are such that as actuation ring 41 slides along the outer surface of latch segment 29, contact between the convex inner surface of actuation ring 41 and the convex outer surface of latch segment 29 is maintained. As latch segment 29 rotates about end 35, the relative angle between the outer surface of latch segment 29 and the inner surface of actuation ring 41 will change. The design of the curvature of both the inner surface of actuation ring 41 and outer surface of latch segment 29 must take this relative change into account to allow the surfaces to remain in contact.
Actuation ring 41 moves axially between the upper unlocked position of FIG. 2 and the lower locked position of FIG. 3. In this embodiment, actuation ring 41 is moved vertically by a series of load transfer blocks 43 that are moved axially by a drive sleeve 47, which resides on the outside of box 23. Drive sleeve 47 forms a complete ring around box 23, with the inner cylindrical surface of drive sleeve 47 matching the outer cylindrical surface of box 23. The number of load transfer blocks 43 corresponds to the number of latch segments 29 in this embodiment. The load transfer blocks 43 travel in slots or windows 44 that are milled into box 23. Actuation ring retainer 55 secures actuation ring 41 to load transfer block 43. Actuation ring retainer 55 is a split ring. A retaining screw 53 attaches actuation ring retainer 55 and the actuation ring 41 to each load transfer block 43. In an alternate configuration, transfer blocks 43 directly engage latch segments 29, and there is no need for the actuating ring or retainer. The drive sleeve 47 may be moved axially by an actuation device 85 built in to a riser spider system such as spider system 80 shown in FIG. 4. Spider system 80 is mounted on platform 13 and moves horizontally towards riser pipe 25 until upward facing surface 75 of vertical member 77 of spider system 80 is positioned such that it can support downward facing surface 79 of pin assembly 27. A handling tool has piston assembly 83 which is supported by spider system 80, and threaded adapter 87, which is located on top of piston assembly 83. Threaded adapter 87 contains actuation devise 85 which engages drive sleeve 47 and moves drive sleeve 47 axially by the action of piston assembly 83.
Returning to FIG. 3, when connected, conical seal face 48 of joint 21 and seal face 49 of joint 25 are pressed against either side of gasket 51. Gasket 51 prevents leakage of fluid between the interior of the riser and the surrounding environment. Seals 54 and 56 between box 23 and pin 27 seal cavity 39 against the entry of sea water. Seals 52, 54 additionally prevent high pressure bore fluid from passing into cavity 39. Seals 58 and 60 between drive sleeve 47 and box 23 prevent the entry of sea water into seal cavity 39 via the space between drive sleeve 47 and box 23. Box 23 contains a port 62 for testing seals 52 and 54, and for allowing leakage of high pressure bore fluids to vent before passing into cavity 39.
A plurality of retraction segments or links 45 are carried on pin 27 above profile 33. Each retraction link 45 has an upward facing curved concave surface which engages a curved convex surface 46 depending from box 23. This engagement allows retraction link 45 to pivot about the curved convex surface 46 of box 23. A lower side of retraction link 45 contains a lip 50 which engages an upper edge of latch segment 29. Actuation ring retainer 55 has a convex curved surface that engages the concave outer surface of each retraction link 45.
Referring again to FIG. 2, in order to release the first riser 21 from second riser pipe 25, actuation ring 41 is moved to the lower position by the load transfer blocks 43 that are moved axially by a drive sleeve 47. When actuation ring retainer 55 makes contact with retraction link 45, it causes retraction link 45 to rotate or pivot about convex surface 46. Lip 50 engages the upper edge of latch segment 29, pivoting latch segment 29 into the open position. As a result, profile 31 of latch segment 29 disengages from profile 33 of pin 27. Box 23 contains a sufficiently large cavity 39 to allow latch segment 29 to pivot into the open position and fully disengage from pin 27. In an alternative configuration, load transfer blocks 43 contact actuation rings 55 directly.
The curvature of the convex surface of actuation ring retainer 55 and the curvature of concave outer surface of retraction link 45 are such that as actuation ring retainer 55 slides along the outer surface of retraction link 45, contact between the surfaces is maintained. As retraction link 45 rocks or pivots about convex surface 46, the relative angle between the convex surface of actuation ring retainer 55 and the curvature of concave outer surface of retraction link 45 will change. The design of the curvature of both the convex surface of actuation ring retainer 55 and concave outer surface of retraction link 45 must take this relative change into account to allow the surfaces to remain in contact.
The connection is compressively preloaded by providing a relatively shallow load flank angle to profile 31 of latch segment 29 and to the corresponding profile 33 of pin 27. The magnitude of preloading should be sufficient such that if the maximum projected tensile load is applied to riser joint 21 and 25, face 48 of joint 21 and face 49 of joint 25 do not separate from gasket 51. The preload would thus be sufficient to maintain the contact between faces 48 and 49 and gasket 51 under expected working loads of the joint sections. The preloading forces are transmitted from joint 21 through box 23 and transferred to pin assembly 27 of joint 25 via the profiles 31 and 33.
In operation, when making up riser 11 for lowering into the sea, the operator makes sure that latch segment 29 is in the open position as shown in FIG. 2. The operator lowers a first riser joint 25 with the end of riser joint 25 containing pin assembly 27 pointed upwards and holds this riser joint in place with the riser spider system of platform 13. The operator then lowers a second riser joint 21, with box 23 pointed downward, landing box 23 of riser 21 over the pin assembly 27 of riser joint 25. The operator then actuates drive sleeve 47 by an actuation device built into the riser spider of platform 13, which moves load transfer blocks 43 downward, which in turn repositions actuation ring 41, forcing profile 31 of latch segment 29 into engagement with profile 33 of pin 27. When the operator is ready to install the next riser joint, he repeats this cycle. The operator can break out the riser joint of riser 11 by reversing the procedure.
Turning to FIG. 4, one embodiment of the present invention may also include an automatic connector actuation lock 64. Actuation lock 64 ensures that drive sleeve 47 does not move unexpectedly during operations. Actuation lock 64 can lock drive sleeve 47 in both the open or engaged position. In particular, the actuation lock will ensure that drive sleeve 47 remains in the engaged position during working conditions, and the open position while bringing the joints together during installation.
Actuation lock 64 is composed of two concentric split rings, comprising a smaller diameter ratchet ring 66 and a larger diameter back-up ring 68, both located within cavity 70 in drive sleeve 47, as can be seen in FIG. 5. A threaded ring 71 secures to drive ring 47 to define the upper end of cavity 70. Ratchet ring 66 has a groove profile 72 on its inner diameter that corresponds to groove profile 74 on the outside diameter of box 23. Ratchet ring 66 is biased inward to engage profile 74. Ratchet ring 66 has groove profile 76 on its outer diameter that corresponds to groove profile 78 on the inner diameter of back-up ring 68. Back-up ring 68 is outwardly biased.
When riser actuation device 85 engages drive sleeve 47 (FIG. 4), engagement member 81 of threaded adapter 87 engages peg member 89 of threaded adapter 87 depresses a plurality of pins 82 spaced radially around and carried on drive sleeve 47, which force back-up ring 68 to reduce in diameter. Cavity 70 of drive sleeve 47 has a downward sloping shoulder 84 which remains in contact with the upward sloping surface 86 of back-up ring 68 such that as back-up ring 68 reduces in diameter, it also moves upward along downward facing shoulder 84. The upward movement of back-up ring 68 aligns outer profile 76 with profile 78 on the inner diameter of back-up ring 68 such that the upward facing flanks 88 of profile 76 of ratchet ring 66 do not interfere with the downward facing flanks 90 of profile 78 of back-up ring 68. This alignment of profiles 76 and 78 allows ratchet ring 68 to expand and contract and move axially over threads 74 of the outer diameter of box 23 as drive sleeve 47 is moved either upwards or downwards.
Groove profile 72 on ratchet ring 66 engages groove profile 74 on the outside diameter of box 23 when drive sleeve 47 is in the locked position (FIG. 6). When drive sleeve 47 is in the unlocked position (FIG. 5), groove profile 72 on ratchet ring 66 engages a profile 92 (FIG. 4) on the outside diameter of box 23 spaced above profile 72. While engaging profile 92, ratchet ring 66 holds drive sleeve 47 in the unlocked position.
When threaded adapter 87 is removed, turning now to FIG. 6, pins 82 retract from cavity 70 causing back-up ring 68 to expand and take on a larger diameter. As back-up ring 68 moves outward, downward sloping shoulder 84 of cavity 70 remains in contact with the upward sloping surface 86 of back-up ring 68, forcing back-up ring 68 to move downward. When back-up ring 68 is in the outer and lower position, face 94 of profile 78 lines up with face 96 of profile 76 and ratchet ring 66 is unable to expand. As a result, profile 74 of box 23 engages profile 72 of ratchet ring 66 and ratchet ring 66 unable to move axially, locking drive sleeve 47 in place.
The invention has significant advantages. The coupling provides a high preload which is necessary for long, high pressure riser strings. The coupling can be quickly made-up and broken out with an automated handling tool. Personnel are not placed in exposed positions while the riser is being made-up or broken out. The assembly and retrieval of a riser is less time consuming than in the prior art.
The present invention has been described with reference to several embodiments thereof. Those skilled in the art will appreciate that the invention is thus not limited, but is susceptible to variation and modification without departure from the scope and spirit thereof For example, box 23 and pin 27 could be connected with the pin facing upward or downward. The lock could be used with connectors other than one using a pivoting latch assembly.
Patent Application
20070267197
