EP0916006A1 - Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension - Google Patents

Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension

Info

Publication number
EP0916006A1
EP0916006A1 EP96928044A EP96928044A EP0916006A1 EP 0916006 A1 EP0916006 A1 EP 0916006A1 EP 96928044 A EP96928044 A EP 96928044A EP 96928044 A EP96928044 A EP 96928044A EP 0916006 A1 EP0916006 A1 EP 0916006A1
Authority
EP
European Patent Office
Prior art keywords
platform
risers
tendons
buoyancy
seafloor
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.)
Granted
Application number
EP96928044A
Other languages
German (de)
English (en)
Other versions
EP0916006B1 (fr
EP0916006A4 (fr
Inventor
Jack Pollack
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.)
Imodco Inc
Original Assignee
Imodco Inc
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
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=22255546&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0916006(A1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Imodco Inc filed Critical Imodco Inc
Priority claimed from PCT/US1996/012639 external-priority patent/WO1998005825A1/fr
Publication of EP0916006A1 publication Critical patent/EP0916006A1/fr
Publication of EP0916006A4 publication Critical patent/EP0916006A4/fr
Application granted granted Critical
Publication of EP0916006B1 publication Critical patent/EP0916006B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Definitions

  • One method for developing and producing hydrocarbons from deep water oil fields is to provide a fixed platform.
  • Such fixed platforms may have drilling equipment as well as hydrocarbon processing equipment (e.g. to separate stones, sand, etc. from hydrocarbons, separate gas from oil, and burn or reinject gas).
  • hydrocarbon processing equipment e.g. to separate stones, sand, etc. from hydrocarbons, separate gas from oil, and burn or reinject gas.
  • TLP tension leg platform
  • a large platform floats at the sea surface and is anchored by a group of tendons that extend vertically to the seafloor. The tendons are under high tension, produced by the large buoyant platform, which results in very little drift of the platform.
  • Such large TLP's carry substantially the same type of equipment as a fixed platform, including hydrocarbon processing equipment and permanent quarters for a crew to service the various equipment.
  • Such TLP systems may include perhaps twenty wells, and perhaps twenty corresponding fluid -carrying risers which must be tensioned.
  • a complement of 20 risers results in an additional downward force of perhaps 2,000 tons (1800 MT) on the platform of the TLP system, which is no more than 10% of the platform displacement.
  • a TLP (tension leg platform) system and method for installing risers in such system are provided, which enables the use of a TLP system of low cost.
  • the platform has a relatively small displacement such as 6,000 tons (5500 MT), and is anchored with correspondingly lightweight tendons which apply a load such as 1 ,200 tons (1100 MT).
  • a full complement (e.g. 20) of risers is significant, as it may amount to perhaps
  • Each riser may apply a load such as 100 tons (91 MT), which is more than 1% of the total platform displacement.
  • Applicant compensates for the load applied by each additional riser, by initially establishing the platform with flooded buoyancy chambers, and by adding buoyancy when each riser is attached, to compensate for the riser- added load.
  • the platform may carry a drill/workover rig that can be moved to different locations. Buoyancy can be added to where the rig is moved and reduced from where the rig was moved, to avoid over and under tensioning of tendons and risers.
  • FIG. 1 is an isometric view of a TLP (tension leg platform) of the present invention, showing one of the risers being installed, and also showing a maintenance boat.
  • TLP tension leg platform
  • FIG. 2 is an isometric view of the platform of the system of FIG. 1.
  • FIG. 3 is a partial section side view of the system of FIG. 1 , showing how the buoyancy of the platform is changed.
  • FIG. 4 is an enlarged view of a portion of FIG. 3, showing a hydrocarbon production tree thereof.
  • FIG. 5 is a sectional view of a tendon and of a riser of the system of FIG. 1.
  • FIG. 6 is a side elevation view of an oil production complex which includes the system of FIG. 1.
  • FIG. 1 illustrates a TLP (tension leg platform) system 10 which includes a platform 12 that floats at the sea surface 14 and which is anchored largely by groups of tendons 16.
  • the tendons extend substantially vertically from each of four corners 21 - 24 of the platform down to the seafloor 26.
  • the tendons are connected to a template 30 that is anchored to the seafloor.
  • the particular system includes twelve tendons arranged in groups of three at each of the corners of the platform and of the template.
  • the template has wellhead couplings 32 arranged at the sides of the square template 30, to which risers such as 34 are connected.
  • the system is initially setup as shown in FIG. 1 , with only the tendons 16 extending down to the seafloor.
  • Wells 31 may be drilled in the seafloor through the wellhead couplings 32, and risers such as riser 34 are then installed, which have lower ends 36 connected to the seafloor at the template 30, and upper ends 38 coupled to the platform.
  • risers such as riser 34 are then installed, which have lower ends 36 connected to the seafloor at the template 30, and upper ends 38 coupled to the platform.
  • Both the platform and template are of substantially rectangular shape as seen in a plan view.
  • the upper end 38 of the riser 34 extends through an aperture 40 in the lower portion 42 of the platform, through the water line or sea surface 14, and to an upper part 44 of the platform which lies above the sea surface.
  • a hydrocarbon production tree 50 is mounted on the upper portion 44 of the platform to lie above the sea surface. As shown in applicant's FIG. 4, the tree 50 has various valves such as 52, 54 and pipe couplings, where well effluent can be removed for processing, and through which gas might be reinjected, control signals (in the form of fluid pulses) can be delivered to downhole equipment to operate a valve thereat, etc.
  • risers 34 and tendons 16 be kept under a substantial tension, so they cannot whip about and strike one another.
  • Tension in the risers is established by a rig 150 (FIG. 1). After a riser is tensioned, a stopper 56 (FIG. 4) thereafter maintains the tension.
  • the tendons are tensioned by deballasting the TLP (by pumping air into water- filled chambers) when the TLP system is initially installed.
  • working displacement means the weight of water that is displaced by the platform in use.
  • Applicant uses tendons 16 which are of relative low tension capacity, with their preferred tension under quiescent conditions being about 150 tons (140 MT) each. The result is that the total quiescent downward force of the twelve tendons is about 1 ,800 tons (1600 MT).
  • the riser tension is considerable as compared to platform displacement and tendon total tension, in that total riser tension (of twenty risers) is more than 20% of platform displacement, and more than 20% of total tendon tensions, so the tension in each riser is at least 1% of platform displacement and total tendon tension.
  • the total tension applied by all twenty risers would be about 2,000 tons (1800 MT), which is a very significant portion (about one-third) of the total downward force of 6,000 tons (5500 MT) on the platform 12.
  • the total downward force of 6,000 tons on the platform may include a total weight of the platform in air, of 2,200 tons, plus 1 ,800 tons in tendon tension, plus 2,000 tons of riser tension (when all 20 risers are installed).
  • the downward force that would be applied by all risers (of 2000 tons) is at least about equal to the downward force (of 1800 tons) applied by all of the tendons.
  • the platform may have a width, length, and height, that are each about 30 meters, and is designed for installation in a deep sea (usually a plurality of hundreds of meters) that may have a depth on the order of 1 ,000 meters. Under severe storm conditions, the tendon tension may more than double to 300 tons or more per tendon.
  • the system shown in FIG. 1 can produce from up to twenty wells, it is common to drill and install only one or a few wells at a time, and to operate the system for an extended period before additional wells are added (if ever, depending on production rates achieved and other matters).
  • the additional downward load on the platform 12, that is added when each riser is installed is substantial (over 1% of total platform displacement). If a group of risers are added, which each apply a load of
  • the tendons would have to be initially set at a tension of 287 tons each (a total of about 3,440 tons which is 91% over the ideal) and would be overtensioned in event of a storm.
  • the tendons could be initially tensioned at 11 ,000 tons (10% over ideal).
  • the net tendon tension would fall to only 9,000 tons (10% below ideal). 90% of ideal tension does not substantially affect performance.
  • applicant changes the buoyancy of the platform 12 whenever a group of risers are added.
  • the TLP is provided with multiple buoyancy chambers such as 90, 92, and 94, which may be initially flooded with water, so that an imaginary water line 96 on the platform lies at sea level 14 when all tendons are attached and properly tensioned, but no riser has been installed.
  • a group of risers which includes one or more risers
  • the platform tends to move down in the water (and the tendon tension tends to decrease) applicant adds buoyancy to the platform.
  • An air pump 100 pumps air (or other gas such as nitrogen) through a valve and pipe 102 to one of the compartments or buoyancy chambers 94.
  • the compressed air at 103 in the chamber causes water 104 in the chamber to be expelled through a vertical pipe 106 into the sea.
  • the level of platform submersion will remain constant and the tension in the tendons will remain constant.
  • no retensioning of the tendons is required and the platform remains at a constant desired level of submersion which will keep the trees 50 above water (for easy servicing) while maintaining only a moderate profile for low wave response.
  • the pump 100 is preferably brought to the platform on a relatively small boat by a crew that is not quartered on the platform (although a temporary emergency shelter can be provided).
  • the boat also can bring the rig to the platform.
  • the platform can be made relatively small and cheap. Since one or a few risers may be added to only one side of the platform, applicant prefers to add buoyancy to only that side of the platform to maintain a more constant tendon tension. Accordingly, applicant may add buoyancy to a pair of chambers 94, 110 which lie at opposite ends of the same side 82 of the platform.
  • the platform includes numerous chamber spaced about the axis 109 of the platform, including a plurality of completely underwater chambers stacked one on another. This facilitates compensation for riser tension that avoids tilt of the platform.
  • FIG. 2 shows that the particular platform 12 has six apertures such as 40A - 40F at each side such as 82. A maximum of five is used, with the sixth used if one of the others cannot be used.
  • the platform has three apertures such as 116A - 116C at each corner such as 22, where tendons will lie.
  • FIG. 5 is a sectional view of one tendon 16 and of one riser 34.
  • a common tendon size has an outside diameter D of 13 inches while a common riser size has an outside diameter of 9% inch.
  • One or several fluid- carrying pipes such as 112, 114 may lie within the riser 34 to actually carry fluid.
  • the rest of the inside of the riser normally contains air or nitrogen, as does the inside of the tendon 16, to provide buoyancy that counteracts the weight of the steel.
  • prior risers might be of the same diameter as riser 34, prior tendons used in TLP systems were typically of greater diameter than risers 16 and/or more of them were used.
  • the riser 34 bends about the bottom of the tree for up to 0.8° of platform deviation from its quiescent position.
  • an upper crossload bearing 111 presses against the walls of aperture 40, and riser bending occurs immediately below bearing 111. Between 5° and maximum deviation (perhaps 8° in a severe storm), riser bending occurs at a lower crossload bearing 113.
  • the tendons each bend about a joint 115 that is also at the bottom of the platform, so the tendons and risers remain parallel for large platform drift.
  • the tendon 16 of FIG. 5 of diameter D of 13 inches (33cm) has a cross-sectional area of steel of 17.3 inches 2 (112cm 2 ), while the riser 34 of 9% inch (24.4cm) diameter has a cross-sectional area of steel of 11.45 inches 2 (74cm 2 ). It is desirable to maintain the steel in each tendon and riser at the same unit tension stress level, of about 19,200 psi (132 MPa). For a sea depth of 1 ,000 meters, such equal stress (per unit cross-sectional area) results in an elongation of 2.2 feet (0.67 meter) for each.
  • the platform 12 includes four vertically extending corner columns 116, 117, 118 and 119 lying at the corners of an imaginary rectangle (which is preferably substantially a square).
  • Four horizontal beams 121 , 122, 123 and 124 each connect the lower ends 125 of a different pair of columns.
  • Each of the columns and beams 116-119 and 121-124 has an average width W of a plurality of feet (e.g.
  • a beam structure 126 comprising multiple steel beams (none forms a hollow water-filled chamber), connects the upper ends 127 of the columns.
  • Each column such as column 116 shown in FIG. 3 has a plurality of vertically spaced chambers with a horizontal separating wall 128. The separating wall is part of the column structure. The use of a plurality of vertically-spaced columns avoids large platform tilt if one of the chambers develops a leak.
  • FIG. 6 shows an oil production complex 130 which includes the system 10 of FIG. 1. Oil passing up through the risers 34 and into the trees on the platform 12, is gathered and passed through pipes lying within a conduit 132 that extends to a large vessel 134.
  • the large vessel 134 may be a tanker with large oil-storing capacity, and which also has hydrocarbon processing equipment 136, permanent (nonemergency crew quarters where personnel stay for many days under normal operating conditions), offloading equipment for transferring oil to other tankers, life boats, etc. If the platform has any hydrocarbon processing equipment, it is minimal in that the mass of processing equipment on the vessel is at last 5 times as great.
  • the vessel supports a turret 140 that can remain stationary (not rotate much, but only drift) while the vessel weathervanes around it, and the vessel is moored by catenary anchor chains 142.
  • the anchor chains allow the vessel to drift only a moderate amount such as 300 meters.
  • the platform 12 lies in water having a depth of 1 ,000 meters and the space between the vessel 134 and platform is at least 500 meters. It is noted that the fluid conduit 132 includes two sections, with a buoy 144 connecting them.
  • a tender assisted workover rig 150 which can carry out well completion, workover and redrilling.
  • the rig 150 can be shifted around the TLP on skids, which is well known to the industry. For some systems, it is possible to remove the rig when a storm approaches.
  • the conduit 134 can extend to shore and the crew is quartered on shore.
  • Applicant compensates for the change in center of gravity (and center of buoyancy) caused by such movement by reducing buoyancy at the previous rig location (by admitting water into buoyancy chambers near the previous rig location) and/or by adding buoyancy at the new rig location (by removing water from buoyancy chambers near the new rig location). This is because tension elements (tendons and any already-installed risers) are spaced about the platform axis 152, and such compensation minimizes changes in tension of such tension elements due to such rig movement.
  • the platform is provided with buoyancy adjusting means in the form of chambers which are initially flooded but which can be partially or completely filled with gas instead of water to increase platform buoyancy.
  • buoyancy adjusting means in the form of chambers which are initially flooded but which can be partially or completely filled with gas instead of water to increase platform buoyancy.
  • Such ability to increase platform buoyancy in steps allows applicant to easily adjust for the additional tension produced by the addition of each riser.
  • the light weight platform preferably has only minimal equipment, including a tree for each riser, possibly a mount for holding a derrick, and minimal couplings and piping.

Landscapes

  • Earth Drilling (AREA)

Abstract

Cette invention concerne un système de plate-forme à jambes de tension comportant une plate-forme de dimension relativement faible (12) et des câbles de précontrainte (16) de capacité relativement faible bien que suffisants pour mettre en tension des tubes prolongateurs (34) conçus pour le transport d'hydrocarbures en provenance de puits des fonds océaniques jusqu'à la plate-forme. La plate-forme qui flotte à la surface de la mer étant maintenue par les câbles de précontrainte, il est possible de relier par des tubes prolongateurs les puits des fonds océaniques à un côté de la plate-forme du fait que la tension de chaque tube prolongateur est compensée par un apport de flottabilité du côté correspondant de la plate-forme, ainsi que par une évacuation de l'eau d'un compartiment (94) de la plate-forme effectuée au moyen d'air comprimé (en 100).
EP96928044A 1996-08-02 1996-08-02 Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension Expired - Lifetime EP0916006B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1996/012639 WO1998005825A1 (fr) 1994-12-14 1996-08-02 Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension

Publications (3)

Publication Number Publication Date
EP0916006A1 true EP0916006A1 (fr) 1999-05-19
EP0916006A4 EP0916006A4 (fr) 2001-10-17
EP0916006B1 EP0916006B1 (fr) 2003-10-29

Family

ID=22255546

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96928044A Expired - Lifetime EP0916006B1 (fr) 1996-08-02 1996-08-02 Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension

Country Status (2)

Country Link
EP (1) EP0916006B1 (fr)
BR (1) BR9612701A (fr)

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
No further relevant documents disclosed *
See also references of WO9805825A1 *

Also Published As

Publication number Publication date
BR9612701A (pt) 1999-08-03
EP0916006B1 (fr) 2003-10-29
EP0916006A4 (fr) 2001-10-17

Similar Documents

Publication Publication Date Title
US6227137B1 (en) Spar platform with spaced buoyancy
US5433273A (en) Method and apparatus for production of subsea hydrocarbon formations
US6309141B1 (en) Gap spar with ducking risers
US5575592A (en) TLP tension adjust system
US6170424B1 (en) Production/platform mooring configuration
US4468157A (en) Tension-leg off shore platform
WO1987001748A1 (fr) Caisson de forage, de production et de stockage de petrole pour eaux profondes
US6336421B1 (en) Floating spar for supporting production risers
US20060056918A1 (en) Riser system connecting two fixed underwater installations to a floating surface unit
US5381865A (en) Method and apparatus for production of subsea hydrocarbon formations
EP1540127B1 (fr) Plateforme offshore comprenant un systeme de flottabilite et un pont de coffre a mouvement limite verticalement
US4620820A (en) Tension leg platform anchoring method and apparatus
US6106198A (en) Method for installation of tension-leg platforms and flexible tendon
US6688250B2 (en) Method and apparatus for reducing tension variations in mono-column TLP systems
US5997218A (en) Method of and apparatus for stabilizing a tension-leg platform in deep water operations
US6007275A (en) Method and apparatus for employing stopper chain locking mechanism for tension-leg platform tendons
EP0916006B1 (fr) Systeme de reglage de la mise en tension d'une plate-forme a jambes de tension
WO2006136960A2 (fr) Tour de colonne montante hybride et procedes d'installation
Wanvik et al. Deep water moored semisubmersible with dry wellheads and top tensioned well risers
RU2773250C2 (ru) Плавучая система и способ с плавучей надставкой и направляющей трубой
Murray et al. A Large Deck Extendable Draft Platform Design for Ultra-Deepwater in the Gulf of Mexico
NO321832B1 (no) System strekkstagplattform og fremgangsmate for operasjon av en strekkstagplattform
EP0750717A1 (fr) Procede et appareil d'exploitation de formations d'hydrocarbures sous-marins
GB2329205A (en) Riser installation method
GB2346842A (en) Floating substructure with ballasting system

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19990219

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): FR GB NL

A4 Supplementary search report drawn up and despatched

Effective date: 20010831

AK Designated contracting states

Kind code of ref document: A4

Designated state(s): FR GB NL

17Q First examination report despatched

Effective date: 20020715

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): FR GB NL

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed

Effective date: 20040730

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20130826

Year of fee payment: 18

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20130827

Year of fee payment: 18

REG Reference to a national code

Ref country code: NL

Ref legal event code: V1

Effective date: 20150301

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20140802

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20150301

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 20

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20140802

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20150727

Year of fee payment: 20