Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
  • E21B43/0107—Connecting of flow lines to offshore structures
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
  • E21B43/013—Connecting a production flow line to an underwater well head

Definitions

• This invention relates to the connection of a hydrocarbon flowline to subsea production apparatus and particularly to a method of making such a connection suitable for performance by remotely operated submersible vessels. It is known to pass hydrocarbons from a subsea well through various control and safety valves arranged in a so-called Christmas tree structure at the well head and into a flowline at, or embedded in, the sea bed for transport to some other location. The valve tree is usually lowered onto, and if necessary removable from, a support bed and the connection of a flowline thereto is not without difficulty.
• Another approach uses techniques employed also in replacing damaged sections of flowlines and comprises lowering the flowline so that it terminates some distance apart from the support bed and upon lowering of the production apparatus valve tree inserting a flowline spool or link between and connecting the respective parts.
• Connecting links or spools are in practice provided with joints which permit axial extension and angular offset, or swivel, of different sections or end coupling parts, examples of such being given by patent specification EP 210714A and EP 207582A respectively.
• Connecting links incorporating such joints in the dimensions used as hydrocarbon flowlines are also provided.
• SUBSTITUTE SHEET usually configured and installed with the help of lifting machinery by divers who ensure the configurations each connecting link is tailored to the particular disposition of valve tree structure and flowline. It will be understood that even when the end of the flowline is brought a nominally predetermined position with respect to production apparatus the accumulation of dimensional and positional tolerances with structures of this size and nature still requires individually tailored connecting pieces. It will be further understood that in wells which are too deep for direct diver action such a connecting piece has to be assembled by the use of submersible vehicles with the limitations imposed by their lack of dexterity and size. This latter factor may be a matter for consideration where the production apparatus and flowline termination is contained within a protective framework and the protective framework constrains the manoeuvrability and access of such a submersible vehicle.
• a method of making a flowline connection between an outlet of subsea hydrocarbon production apparatus lowered onto a subsea support bed and a subsea flowline comprises assembling on the apparatus prior to submerging and lowering to the support bed a flowline link comprising first and second U-shaped flowline pieces, each having limbs extending from a bight portion and terminating substantially parallel to each other, with one limb of each flowline piece joined end-to-end to the other piece by way of an axially rotatable connecting piece, the other limb of the first flowline piece pivotally mounted on said apparatus with the limb axis in a predetermined attitude with respect to operational disposition of the apparatus for rotation about the limb axis and the other limb of the second flowline piece fitted with a first part of a two part termination coupling cooperable with that of a second part, disposing the flowline pieces of the link with respect to each other and the apparatus so that the flowline pieces are folded against the apparatus, providing said
• a linkage arrangement between an outlet of a subsea hydrocarbon production apparatus lowered onto a support bed and a subsea flowline comprises
• a flowline link arranged to be lowered as a unitary structure with apparatus to the support bed, said flowline link comprising first and second U-shaped flowline pieces each having limbs extending from a bight portion and terminating substantially parallel to each other, one limb of each piece being joined end-to-end to the other piece by way of an axially rotatable connecting piece, the other limb of the first flowline piece being pivotally mounted on said lowered apparatus with the limb axis in a predetermined attitude for rotation about the limb axis and the other limb of the second flowline piece carrying at its end a first part of a two part termination coupling,
• (iii) means operable to rotate the flowline pieces with respect to each other and the submerged apparatus to align the two parts of the termination coupling and effect coupling thereof.
• FIG. 1 is a perspective view of a first form of subsea hydrocarbon production apparatus and a flowline with a flowline link between them made of pivotally connected flowline pieces in accordance with the present invention
• Figure 2 is a side elevation of a portion of the hydrocarbon production apparatus of Figure 1 showing the flowline pieces connection assembled thereon for deployment with the production apparatus,
• Figure 3 is a plan view of the production apparatus of Figure 1 and flowline piece assembled thereon after submerging the apparatus, the relative disposition of the flowline and the attachment of a submersible vehicle to the flowline pieces to perform the connection method,
• Figure 4 is a plan view similar to Figure 3 showing relative rotation between the flowline pieces by the submersible vehicle
• Figure 5 is a plan view similar to Figure 4 but showing relative rotation between the flowline pieces and production apparatus displacing the remote end of the flowline pieces towards the flowline termination for connection thereto
• Figure 6 is a perspective view of a second form of subsea hydrocarbon production apparatus in which the flowline link is carried by and deployed from apparatus submerged before a valve tree having a production outlet to the flowline link.
• a subsea hydrocarbon production apparatus 11 comprises a series of control and safety valves which deliver liquid or gaseous hydrocarbon products to an outlet port 12 which, as shown, extends downwardly at the side of the apparatus. Because of the stacked nature of the valves comprising a large part of the apparatus it is often referred to as a Christmas tree or valve tree.
• the production apparatus including the valve tree 11 and outlet 12 is a unitary structure assembled and lowered from the surface to rest on a submerged support bed 13, the tree furthermore being susceptible to hauling back to the surface for maintenance or replacement.
• the support bed 13 is surrounded by a substantial framework 14, into which the apparatus is lowered, which serves to protect it from damage by large objects moving through the water and permits limited access by a remotely operated submersible vehicle (ROV) 15.
• ROV submersible vehicle
• At least one flowline 16 by which well products are removed is laid on, or buried in, the sea bed and terminates at the framework 14 in an upstanding portion 16' and displaced from the operational position of the production apparatus, that is, from the support bed 13.
• a flowline link 18 extends between the tree outlet port 12 and flowline 16 comprising first and second U-shaped flowline pieces 19, 20.
• the flowline pieces 19 and 20 have limbs 19', 19" and 20', 20" respectively extending from bight portions 19'" and 20"' respectively, which limbs terminate substantially parallel to each other. As shown the limbs are straight and the axis of the limb where it terminates thus extends for the whole limb, making it convenient to refer to the limb axes as being parallel.
• One limb of each piece, say 19' and 20' is joined end-to-end to the other piece by way of an axially rotatable connecting piece 21.
• the connecting piece permits the limbs 19' and 20' to rotate relative to each other about a common limb axis and may be of the type shown in the aforementioned EP 207582 which permits such relative rotation when supplied with a pressurised fluid and also permits limbs 19' and 20' to axially misalign or swivel to a limited extent about an axis transversely to the axis of the limb to which fitted.
• the other limb 19" of the first flowline piece is connected by way of a further connecting piece 22 of similar form to the downwardly extending outlet port 12.
• Such connecting piece provides a mounting for the flowline link on the apparatus by which the limb 19", and the remainder of the link 18, is able to pivot about the axis of the limb.
• the outlet port 12 and connected limb are arranged such that the limb axis extends in a predetermined direction when the apparatus is operationally disposed on the support bed and conveniently this predetermined operational attitude is vertical, defining also the axis attitudes for the other limbs.
• the other limb 20" of the second flowline piece is connected to a first part 23 of a two part termination coupling which is adapted to co-operate with a second part 17 carried on the upstanding flowline portion 16' which also extends substantially in the .predetermined vertical direction and is likewise vertically directed.
• the limb 20" of the flowline link is thereby securable to the upstanding portion 16' to provide a flow path between the outlet 12 and flowline 16 by way of the flowline pieces.
• a guidance funnel 24 in the form of a tapered wall, vertically inclined ramp adjacent the second part 17 of the termination coupling facilitates alignment of the two termination coupling parts 17 and 23 as will become clear.
• the flowline link is thus composed of flowline pieces connected by the known adjustable joints but it will be appreciated that the formation and coupling of the link in situ is difficult if not impossible to effect using normal assembly techniques without the aid of divers.
• the flowline connection shown in Figure 1 is made by assembling on the production apparatus before submerging to the support bed the flowline link 18, comprising flowline pieces 19, 20, connecting pieces 21 and 22, and termination coupling part 23, and orientating the flowline pieces of the link with respect to each other and the apparatus so that the pieces are folded flat against the apparatus, as shown in the elevation and plan views of Figures 2 and 3 respectively.
• the two flowline pieces 19, 20 conveniently have limbs which extend orthogonally to straight bight portions and are assembled so that with all the limbs extending in a vertical direction the bight portions are horizontal, permitting the termination coupling part 23 to move to and from the apparatus by relative rotation between the flowline pieces and/or apparatus about a vertical axis common to the limbs and connecting pieces 21 and 22.
• Formation of the connecting piece 21 and/or 22, as a swivel joint pivotable about an axis in a horizontal plane transversely to the nominally vertical connecting axes of the flowline pieces permits the limb 20" and the first part 23 of the termination coupling to be movable substantially in the direction of the limb 20" axis, that is, vertically, by a limited amount.
• the flowline . link is maintained in the shown disposition folded flat against the apparatus by the clamping property of the connecting pieces 21 and 22 whilst they are not energised with pressurised fluid, but pins or clips 25 may be inserted in addition to ensure no unwanted rotation can take place at the connecting pieces.
• the flowline 16 with its terminal portion 16' and termination coupling part is disposed conveniently adjacent the framework 14, and protected thereby, with the flow axis of the portion 16 substantially vertical to agree with the predetermined nominally vertical direction of the limb 20" of the second flowline piece.
• the apparatus 11 Either before or after the flowline is lowered the apparatus 11 is submerged and lowered onto the structure bed when both are in place the ROV 15 approaches the production apparatus, removes any rotation inhibiting pins or clips from the connecting piece, attaches itself to the second flowline piece 20 at a convenient docking point 26, as shown in Figure 3, and connects a fluid pressure supply to the connecting piece 21 and, possibly, connecting piece 22 by hose 27.
• the ROV retracts from the apparatus structure 11 and moves the first part 23 of termination coupling horizontally as illustrated by Figures 3 and 4 until it is disposed in axial alignment with the cooperable second part 17 at which time the parts are brought together to cooperate and are secured to each other in suitable form, automatically or with the aid of the ROV.
• first part 23 of the termination coupling is directed into axial alignment with the second part 17 by the taper of the guidance funnel 24 whereas, by virtue of the limited vertical swivel of the second flow piece permitted by one or both connecting pieces, abutment between the first part 23 of the coupling and the vertically inclined ramp of the funnel permits the first coupling part 23 to be raised in the vertical axial direction with respect to the flowline to clear and align with the part 17 as a result of the ROV guiding the flowline pieces only in a horizontal direction.
• the ROV removes fluid pressure from connecting piece 21 and/or 22 thereby fixing the relative dispositions of the flowline pieces with respect to each other, that is fixing the configuration of the flowline link, before unlocking from the point 26 and withdrawing from the apparatus.
• the precise positional relationship between the submerged production apparatus 11 and flowline termination 16' is immaterial as the variable length and height provided by the two rotatable U-shaped flowline pieces and the connecting pieces permits the required link to be assembled with the aid only of simple manoeuvres and operations on the part of a ROV.
• rotation of the first flowline piece with respect to the apparatus may be performed by a ram 28 extending between the first flowline piece and the apparatus.
• the ram may also be powered by fluid pressure from the ROV or from the apparatus or some equivalent form of motor may be incorporated. Also to ease the burden on the ROV the flowline piece
• connection method although described above with reference to a ROV is not dependent upon the use of such a vehicle or indeed any vehicle and the flowline pieces may be moved manually in shallow seas providing suitable arrangements are made to energise, that is, pressurise, the connecting piece 21 and/or 22 to permit rotation.
• the connecting pieces need not be of a form which requires pressurised fluid from an external source to permit rotation.
• Such connecting pieces are preferred but the energising fluid may be obtained from sources other than the attendant mover of the flowline pieces and may, for instance, be provided by a line extending from a source in the production apparatus or from the surface.
• connection method described hereinbefore is in relation to apparatus in which the flowline link is carried by a single-piece production apparatus with the arm 19" of the first flowline piece connected prior to submerging to the production outlet 12 by means of a connecting piece 22 which permits rotation of the link about the predetermined vertical axis with respect to the apparatus.
• this shows another form of production apparatus in which apparatus 30 carrying the flowline link 18 is assembled above water and lowered to the submerged support bed 13 separately from the part of the production apparatus comprising the valve tree 31 and production outlet 12.
• the flowline link 18 is mounted on the apparatus 30 by means of a support 32 which permits the limb 19" to pivot with respect to the apparatus about the predetermined (vertical) axis, the end of the limb not being connected, and the flowline pieces of the link to be folded flat against the apparatus.
• the apparatus 30 carrying the flowline link assembly is lowered to the support bed with the flowline pieces folded flat against its side and thereafter drawn out by ROV or other means, including a ram if desired, to couple with the flowline 16.
• the valve tree 31 is then lowered onto the apparatus 30 so as to mate with the well and with the production outlet 12 aligned with and into coupling engagement with the end of limb 19". It will be appreciated that rotation of the flowline pieces relative to the apparatus may be completed before the outlet 12 is coupled to the first flowline piece so that the coupling therebetween need not be axially rotatable as described above for connecting piece 22.
• all swivel motion about a horizontal axis that is, to permit movement of the termination coupling part 23 in a vertical direction may be provided by the pivot support between limb 19" and the apparatus rather than connecting piece 21.
• such vertical motion of the termination coupling 23 may be provided by axial telescoping of one of the limbs rather than rotation at one of the connecting pieces or mounts.
• the guidance funnel 24 is not essential but provides a convenient way of ensuring axial alignment between flowline piece limb 20" and flowline 16' for the parts of the termination coupling.
• the ramp function which enables a vertical axial separation of the coupling parts as they are brought into alignment is not essential, the separation being effected by lifting of the flowline piece 20 by the ROV or attached buoyancy with the ROV thereafter forcing the aligned coupling parts into engagement.
• the vertical motion of the limb 20" may not be necessary to clear the flowline termination for alignment of coupling parts if arrangements are made for the first coupling part 23 to move only in a horizontal plane above that of part 17 which is mounted on a subsequently raisable portion of flowline to effect coupling.
• the predetermined direction in which the limbs extend and about which they pivot need not be vertical provided the terminal portion 16' of the flowline has a corresponding attitude but such a non-vertical direction may place a greater burden on the ROV or equivalent in moving the flowline pieces in other than horizontal, and possibly vertical, directions.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Invalid Beds And Related Equipment (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (3)

Citations (3)

• 1988
  • 1988-09-22 GB GB888822268A patent/GB8822268D0/en active Pending
• 1989
  • 1989-09-21 WO PCT/GB1989/001107 patent/WO1990003492A1/en not_active Application Discontinuation
  • 1989-09-21 BR BR898907670A patent/BR8907670A/pt unknown
  • 1989-09-21 EP EP19890910892 patent/EP0436605A1/en not_active Withdrawn

Patent Citations (3)

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