US3470838A - Buoyant wellhead structure - Google Patents

Buoyant wellhead structure Download PDF

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Publication number
US3470838A
US3470838A US723013A US3470838DA US3470838A US 3470838 A US3470838 A US 3470838A US 723013 A US723013 A US 723013A US 3470838D A US3470838D A US 3470838DA US 3470838 A US3470838 A US 3470838A
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US
United States
Prior art keywords
well
wellhead
hull
buoyant
bell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US723013A
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English (en)
Inventor
Alan F Daniell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cammell Laird & Co Shipbuilder
Cammell Laird & Co Shipbuilders & Eng Ltd
Original Assignee
Cammell Laird & Co Shipbuilder
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Publication of US3470838A publication Critical patent/US3470838A/en
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Expired - Lifetime legal-status Critical Current

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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
    • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
    • E21B41/06—Work chambers for underwater operations, e.g. temporarily connected to well heads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B35/4413—Floating drilling platforms, e.g. carrying water-oil separating devices
    • 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
    • E21B33/00—Sealing or packing boreholes or wells
    • E21B33/02—Surface sealing or packing
    • E21B33/03—Well heads; Setting-up thereof
    • E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
    • E21B33/037—Protective housings therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/04—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with single hull
    • B63B2001/044—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with single hull with a small waterline area compared to total displacement, e.g. of semi-submersible type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B2035/442—Spar-type semi-submersible structures, i.e. shaped as single slender, e.g. substantially cylindrical or trussed vertical bodies

Definitions

  • ALAN F2 DAN/ELL BY Q f vM men's.
  • a structure for mooring over a marine oil well comprises a buoyant chamber which is ballasted to float upright.
  • a riser pipe from the well extends up through the structure to means maintaining the pipe in tension such as a float in an open well of the structure.
  • the structure can contain processing equipment which leaks gas into the structure to keep it buoyant.
  • Both (a) and (b) involve expensive construction work at sea and method (a) can constitute a hazard to shipping, whilst method (b) involves the use of divers working externally of the well in their cumbersome diving equipment and for necessarily limited periods 0 time.
  • Method (c) using a caisson technique, involves the use of deep sea divers and diving equipment and if based on a remote control and observation system can be complex and expensive.
  • the present invention provides a buoyant wellhead structure to which divers can readily obtain access and in which they can work to a large extent unimpeded by equipment and the conditions which would hamper their activities it working from the outside of the wellhead structure.
  • a buoyant wellhead structure adapted to be moored over an oifshore oil well or the like installation, comprising a buoyant chamber or bell at the upper part of the structure, means for maintaining said chamber or hell under pressure so as to depress the water level therein, ballasting means at the lower part of the structure so that it is caused to float upright and an air lock providing access to said chamber or bell from below the water line.
  • the chamber or bell forms an enclosure in which personnel can adjust or service the wellhead equipment in comparative safety and freedom for long periods.
  • the required super atmospheric pressure may be maintained in the chamber or bell by permitting an escape or controlled leakage of gas from natural oil or gas processing equipment installed in the chamber or bell or in an associated part of the structure.
  • a riser pipe from the well to the wellhead extends up through the buoyant wellhead structure and the arrangement is such that this pipe is maintained in tension.
  • FIGURE 1 is a sectional elevation of the upper and lower parts of the structure
  • FIGURE 2 shows the structure in use
  • FIGURES 3 and 4 show stages in towing the wellhead structure to the well location and anchoring it thereover.
  • the wellhead structure shown on the drawings comprises a hull 1 of elongated cylindrical bell-like form, constructed with inner and outer skins or shells forming toroidal watertight compartments.
  • the upper part of the hull forms a bell-shaped enclosure 2, and the lower part is increased in both its external and internal diameters.
  • At the bottom the space between the inner and outer skins is filled with heavy fixed ballast 3.
  • the hull (see FIGURE 2) is moored by at least three mooring ropes or chains 4, disposed symmetrically in plan, and connected to mooring anchors or heavy sinkers 5.
  • the mooring ropes or chains are passed through cylindrical trunks 6 attached externally to the hull, and of divergent form at the bottom 7.
  • the upper ends of the mooring ropes or chains are attached at the upper part of the hull to windlasses or Winches 8.
  • the top of the hull is filled with a removable hatch or cover 9, and part of the way down the hull an air lock 10 is provided, for the entry and exit of personnel.
  • a riser pipe 11 from the oil well 12 passes through a hollow toroidal float 13, and is attached thereto.
  • the riser pipe 11 terminates with a valve assembly 14, which is connected by flexible pipes 15 to pipes 16 which are rigidly attached to the hull.
  • the pipes 16 connect to the internal spaces between the inner and outer skins of the hull 1, and these spaces may be utilised for processing of the product of the well and in particular for separation of gas from oil, or of liquid from gas.
  • Pipes 18, communicating with the internal spaces of the hull, are connected to flow lines 17 which carry away the products of the well.
  • the flow lines 17 pass from the sea bed into trunks 6a attached externally to the hull.
  • the trunks 6a are of divergent form at the bottom 7a.
  • a vent 19 connects the bell 2 with the external sea.
  • Certain of the compartments between the inner and outer skins of the hull are provided with sea cocks and vents (not shown) to permit the admission of a controlled amount of water ballast.
  • the hull is maintained in a slightly buoyant condition, with the centre of gravity below the centre of buoyancy, so that it will take up a vertical attitude straining against the mooring chains.
  • the length of these chains is adjusted so that the top of the hull is maintained at a depth adequate to give submergence at all states of tide and sea, and if necessary adequate to avoid dangers to navigation, but yet not so deep as to be beyond the practical limit of normal diving operations.
  • Adjustment of the valves 14 and other equipment at the wellhead may be carried out by divers entering through the lock 10. Once within the bell 2, the divers will be working in dry conditions but will require breathing apparatus if the atmosphere within the bell consists of the leakage gas from the well together with any residual gas from the atmosphere at the time of installation. To avoid explosion hazard, the bell may be purged with nitrogen or other inert gas at the time of installation.
  • a floor or the like is provided in the bell over which the personnel can walk.
  • the anchors 5 (see FIGURE 4) are first laid in a symmetrical disposition around the wellhead, and to each anchor there is attached a length of chain cable 4, the end of which is supported by a buoy B.
  • the hull 1 containing the float 13, temporarily clampel at the upper end of the well or compartment 20, is fitted with an extension tube 21, see FIGURES 3 and 4.
  • Messenger ropes, in the form of continuous loops, are passed through each of the trunks 6, and a further similar loop is passed through the tube 21, and through the whole length of the well 20 via the hole or tunnel in the float 13.
  • the outer part of the messenger rope, passing through the centre of the hull, is attached to buoyed guide lines previously fixed at the oil well template, and these guide lines are hauled through the centre of the hull, the float 13, and the extension tube 21.
  • the riser pipe 11 is lowered through the extension tube 21 and latched t0 the well at the sea bed.
  • the extension tube is then removed, the hatch cover 9 fixed in position, and the level of water within the bell 2 lowered by the admission of gas under pressure.
  • the float 13 is then disconnected from the wall of the well 20 and attached to the riser pipe .11, and the valves and control equipment 14 and flexible pipes 15 installed.
  • the oil or gas outflow lines 17 are then connected.
  • the wellhead structure is preferably installed as previously described before the well is drilled.
  • the extension tube 21 may be connected to the top of the hull by a flexible joint and the top of the extension tube flexibly connected to the mobile drilling ship.
  • the well is then drilled through the central well 20 in the buoyant wellhead before the float 13 and pipe 11 are installed.
  • the bell 2 can be flooded, and the hatch 9 removed and the extension tube 21 reconnected by divers.
  • workover operations can then be carried out from the surface, and on completion the extension tube can be removed, the hatch replaced, and the structure reinstated in its previous form.
  • the air lock 10 may be provided with doors as shown in FIGURE 1 but this not essential.
  • a buoyant wellhead structure adapted to be moored over an offshore well comprising a chamber at the upper part of the structure, means for maintaining said chamber under pressure so as to depress the water level therein when the wellhead structure is moored over an offshore well, ballasting means at the lower part of the structure so that it is caused to float upright, an air lock providing access to said chamber from below the water line, a riser pipe for connection to the well and which extends up through the wellhead structure, and means for attaching said riser pipe to the wellhead structure to maintain said riser pipe in tension when said pipe is connected to the well.
  • a wellhead structure as claimed in claim 1 wherein said riser pipe attaching means comprises a float positioned within an open well of the wellhead structure whereby said riser pipe is maintained in tension.
  • a wellhead structure as claimed in claim 1 including a hull comprising inner and outer skins which provide watertight compartments, the lower part of the space between said inner and outer skins containing heavy ballast.
  • valve means is provided in said connection between the riser pipe and internal spaces of the wellhead structure.

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  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Fluid Mechanics (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Earth Drilling (AREA)
US723013A 1967-04-27 1968-04-22 Buoyant wellhead structure Expired - Lifetime US3470838A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB09417/67A GB1172558A (en) 1967-04-27 1967-04-27 Improvements in or relating to Buoyant Well-Head Structures for Offshores Wells

Publications (1)

Publication Number Publication Date
US3470838A true US3470838A (en) 1969-10-07

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ID=10129013

Family Applications (1)

Application Number Title Priority Date Filing Date
US723013A Expired - Lifetime US3470838A (en) 1967-04-27 1968-04-22 Buoyant wellhead structure

Country Status (3)

Country Link
US (1) US3470838A (enrdf_load_stackoverflow)
GB (1) GB1172558A (enrdf_load_stackoverflow)
NL (1) NL6805977A (enrdf_load_stackoverflow)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3667240A (en) * 1968-11-21 1972-06-06 Metalliques Entrepr Cie Fse Installations for submarine work
US3709307A (en) * 1970-10-05 1973-01-09 Phillips Petroleum Co Underwater drilling and production vessel
US3921558A (en) * 1974-09-16 1975-11-25 Vickers Ltd Floatable vessel
US4004531A (en) * 1974-05-16 1977-01-25 Texaco Inc. Drilling system for deep water offshore locations
US4702321A (en) * 1985-09-20 1987-10-27 Horton Edward E Drilling, production and oil storage caisson for deep water
US5558467A (en) * 1994-11-08 1996-09-24 Deep Oil Technology, Inc. Deep water offshore apparatus
US6244347B1 (en) 1999-07-29 2001-06-12 Dril-Quip, Inc. Subsea well drilling and/or completion apparatus
US6402431B1 (en) 2000-07-21 2002-06-11 Edo Corporation, Fiber Science Division Composite buoyancy module with foam core
US6435775B1 (en) 2000-05-22 2002-08-20 Edo Corporation, Fiber Science Division Buoyancy system with buoyancy module seal
US6439810B1 (en) 2000-05-19 2002-08-27 Edo Corporation, Fiber Science Division Buoyancy module with pressure gradient walls
US6488447B1 (en) 2000-05-15 2002-12-03 Edo Corporation Composite buoyancy module
US20030150618A1 (en) * 2002-01-31 2003-08-14 Edo Corporation, Fiber Science Division Internal beam buoyancy system for offshore platforms
US6632112B2 (en) 2000-11-30 2003-10-14 Edo Corporation, Fiber Science Division Buoyancy module with external frame
US20040126192A1 (en) * 2002-01-31 2004-07-01 Edo Corporation, Fiber Science Division Internal beam buoyancy system for offshore platforms
US20050241832A1 (en) * 2004-05-03 2005-11-03 Edo Corporation Integrated buoyancy joint
US20060162933A1 (en) * 2004-09-01 2006-07-27 Millheim Keith K System and method of installing and maintaining an offshore exploration and production system having an adjustable buoyancy chamber
US20120217016A1 (en) * 2009-09-15 2012-08-30 National Oilwell Norway As Riser tensioner

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO153938C (no) 1979-11-02 1986-06-18 Ostlund As Fremgangsmaate ved oppfangning og separasjon av olje, vann og gass fra en oljebroenn og en utligningskolonne for utfoerelse av fremgangsmaaten.
GB2326655B (en) * 1997-06-27 2001-11-28 Amerada Hess Ltd Offshore production of hydrocarbon fluids

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US962019A (en) * 1909-09-30 1910-06-21 John Garnar Flood Diving-bell apparatus for submarine work.
US2519453A (en) * 1947-01-13 1950-08-22 Goodman Charles Traveling underwater compressed air working chamber
US3036438A (en) * 1958-04-04 1962-05-29 Jersey Prod Res Co Caisson with float releasably attached

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US962019A (en) * 1909-09-30 1910-06-21 John Garnar Flood Diving-bell apparatus for submarine work.
US2519453A (en) * 1947-01-13 1950-08-22 Goodman Charles Traveling underwater compressed air working chamber
US3036438A (en) * 1958-04-04 1962-05-29 Jersey Prod Res Co Caisson with float releasably attached

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3667240A (en) * 1968-11-21 1972-06-06 Metalliques Entrepr Cie Fse Installations for submarine work
US3709307A (en) * 1970-10-05 1973-01-09 Phillips Petroleum Co Underwater drilling and production vessel
US4004531A (en) * 1974-05-16 1977-01-25 Texaco Inc. Drilling system for deep water offshore locations
US3921558A (en) * 1974-09-16 1975-11-25 Vickers Ltd Floatable vessel
US4702321A (en) * 1985-09-20 1987-10-27 Horton Edward E Drilling, production and oil storage caisson for deep water
US5558467A (en) * 1994-11-08 1996-09-24 Deep Oil Technology, Inc. Deep water offshore apparatus
US6244347B1 (en) 1999-07-29 2001-06-12 Dril-Quip, Inc. Subsea well drilling and/or completion apparatus
US6488447B1 (en) 2000-05-15 2002-12-03 Edo Corporation Composite buoyancy module
US6439810B1 (en) 2000-05-19 2002-08-27 Edo Corporation, Fiber Science Division Buoyancy module with pressure gradient walls
US6435775B1 (en) 2000-05-22 2002-08-20 Edo Corporation, Fiber Science Division Buoyancy system with buoyancy module seal
US6402431B1 (en) 2000-07-21 2002-06-11 Edo Corporation, Fiber Science Division Composite buoyancy module with foam core
US6632112B2 (en) 2000-11-30 2003-10-14 Edo Corporation, Fiber Science Division Buoyancy module with external frame
US6805201B2 (en) 2002-01-31 2004-10-19 Edo Corporation, Fiber Science Division Internal beam buoyancy system for offshore platforms
US20040126192A1 (en) * 2002-01-31 2004-07-01 Edo Corporation, Fiber Science Division Internal beam buoyancy system for offshore platforms
US20030150618A1 (en) * 2002-01-31 2003-08-14 Edo Corporation, Fiber Science Division Internal beam buoyancy system for offshore platforms
US7096957B2 (en) 2002-01-31 2006-08-29 Technip Offshore, Inc. Internal beam buoyancy system for offshore platforms
US20050241832A1 (en) * 2004-05-03 2005-11-03 Edo Corporation Integrated buoyancy joint
US7328747B2 (en) 2004-05-03 2008-02-12 Edo Corporation, Fiber Science Division Integrated buoyancy joint
US20080213048A1 (en) * 2004-05-03 2008-09-04 Jones Randy A Method for fabricating and transporting an integrated buoyancy system
US20060162933A1 (en) * 2004-09-01 2006-07-27 Millheim Keith K System and method of installing and maintaining an offshore exploration and production system having an adjustable buoyancy chamber
US20120217016A1 (en) * 2009-09-15 2012-08-30 National Oilwell Norway As Riser tensioner
US9051784B2 (en) * 2009-09-15 2015-06-09 National Oilwell Varco Norway As Riser tensioner

Also Published As

Publication number Publication date
GB1172558A (en) 1969-12-03
NL6805977A (enrdf_load_stackoverflow) 1968-10-28

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