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US20120128427A1 - Leg ice shields for ice worthy jack-up drilling unit - Google Patents

Leg ice shields for ice worthy jack-up drilling unit Download PDF

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Publication number
US20120128427A1
US20120128427A1 US13/278,480 US201113278480A US2012128427A1 US 20120128427 A1 US20120128427 A1 US 20120128427A1 US 201113278480 A US201113278480 A US 201113278480A US 2012128427 A1 US2012128427 A1 US 2012128427A1
Authority
US
United States
Prior art keywords
ice
hull
rig
water
legs
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.)
Abandoned
Application number
US13/278,480
Other languages
English (en)
Inventor
Peter G. Noble
Randall S. Shafer
Dominique P. Berta
Michael B. Winfree
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.)
ConocoPhillips Co
Original Assignee
ConocoPhillips Co
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
Priority claimed from US13/277,791 external-priority patent/US20120128426A1/en
Application filed by ConocoPhillips Co filed Critical ConocoPhillips Co
Priority to US13/278,480 priority Critical patent/US20120128427A1/en
Assigned to CONOCOPHILLIPS COMPANY reassignment CONOCOPHILLIPS COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BERTA, DOMINIQUE P., NOBLE, PETER G., SHAFER, RANDALL S., WINFREE, MICHAEL B.
Publication of US20120128427A1 publication Critical patent/US20120128427A1/en
Abandoned legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B17/0017—Means for protecting offshore constructions
    • E02B17/0021—Means for protecting offshore constructions against ice-loads
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B17/02—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
    • E02B17/021—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto with relative movement between supporting construction and platform
    • 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
    • B63B35/08—Ice-breakers or other vessels or floating structures for operation in ice-infested waters; Ice-breakers, or other vessels or floating structures having equipment specially adapted therefor
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B2017/0039—Methods for placing the offshore structure
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B2017/0056—Platforms with supporting legs
    • E02B2017/006—Platforms with supporting legs with lattice style supporting legs
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B2017/0056—Platforms with supporting legs
    • E02B2017/0073—Details of sea bottom engaging footing
    • E02B2017/0082—Spudcans, skirts or extended feet

Definitions

  • This invention relates to mobile offshore drilling units, often called “jack-up” drilling units or rigs that are used in shallow water, typically less than 400 feet, for drilling for hydrocarbons.
  • a jack-up or mobile offshore drilling unit can be used for about 45-90 days in the short, open-water summer season. Predicting when the drilling season starts and ends is a game of chance and many efforts are undertaken to determine when the jack-up may be safely towed to the drilling location and drilling may be started. Once started, there is considerable urgency to complete the well to avoid having to disconnect and retreat in the event of ice incursion before the well is complete. Even during the few weeks of open water, ice floes present a significant hazard to jack-up drilling rigs where the drilling rig is on location and legs of the jack-up drilling rig are exposed and quite vulnerable to damage.
  • Jack-up rigs are mobile, self-elevating, offshore drilling and workover platforms equipped with legs that are arranged to be lowered to the sea floor and then to lift the hull out of the water.
  • Jack-up rigs typically include the drilling and/or workover equipment, leg jacking system, crew quarters, loading and unloading facilities, storage areas for bulk and liquid materials, helicopter landing deck and other related facilities and equipment.
  • a jack-up rig is designed to be towed to the drilling site and jacked-up out of the water so that the wave action of the sea only impacts the legs which have a fairly small cross section and thus allows the wave action to pass by without imparting significant movement to the jack-up rig.
  • the legs of a jack-up provide little defense against ice floe collisions and an ice floe of any notable size is capable of causing structural damage to one or more legs and/or pushing the rig off location. If this type of event were to happen before the drilling operations were suspended and suitable secure and abandon had been completed, a hydrocarbon leak would possibly occur. Even a small risk of such a leak is completely unacceptable in the oil and gas industry, to the regulators and to the public.
  • a very large, gravity based production system, or similar structure may be brought in and set on the sea floor for the long process of drilling and producing the hydrocarbons.
  • These gravity based structures are very large and very expensive, but are built to withstand the ice forces year around.
  • the invention more particularly relates to an ice worthy jack up rig for drilling for hydrocarbons in potential ice conditions in offshore areas including a flotation hull having a relatively flat deck at the upper portion thereof.
  • the flotation hull further includes an ice bending shape along the lower portion thereof and extending around the periphery of the hull where the ice bending shape extends from an area of the hull near the level of the deck and extends downwardly near the bottom of the hull along with an ice deflecting portion extending around the perimeter of the bottom of the hull to direct ice around the hull and not under the hull.
  • the rig includes at least three truss form legs that are positioned within the perimeter of the bottom of the hull wherein the legs are arranged to be lifted up off the seafloor so that the rig may be towed through shallow water and also extend to the sea floor and extend further to lift the hull partially or fully out of the water.
  • a jack up device is associated with each leg to both lift the leg from the sea bottom so that the ice worthy jack up rig may float by the buoyancy of the hull and push the legs down to the seafloor and push the hull partially up and out of the water when ice floes threaten the rig and fully out of the water when ice is not present.
  • Leg ice shields are arranged to protect the truss form legs from ice.
  • the invention further relates to a method for drilling wells in ice prone waters.
  • the method includes providing a flotation hull having a relatively flat deck at the upper portion thereof and an ice bending shape along the lower portion thereof where the ice bending shape extends from an area of the hull near the level of the deck and extends downwardly near the bottom of the hull and an ice deflecting portion extending around the perimeter of the bottom of the hull to direct ice around the hull and not under the hull.
  • At least three truss form legs are positioned within the perimeter of the bottom of the hull where each leg comprises a plurality of vertically oriented posts connected by cross members and ice shields are arranged between the posts to protect the cross members from ice.
  • Each leg is jacked down in a manner that feet on the bottom of the legs engages the sea floor and lifts the hull up and fully out of the water when ice is not threatening the rig while the rig is drilling a well on a drill site.
  • the hull is further lowered into the water into an ice defensive configuration so that the ice bending shape extends above and below the sea surface to bend ice that comes against the rig to cause the ice to submerge under the water and endure bending forces that break the ice where the ice flows past the rig.
  • FIG. 1 is an elevation view of a first embodiment of the present invention where the drilling rig is floating in the water and available to be towed to a well drilling site;
  • FIG. 2 is an elevation view of the first embodiment of the present invention where the drilling rig is jacked up out of the water for open water drilling through a moon pool;
  • FIG. 3 is a second elevation view of the first embodiment of the present invention where the drilling rig is partially lowered into the ice/water interface, but still supported by its legs, in a defensive configuration for drilling during potential ice conditions;
  • FIG. 4 is an enlarged fragmentary elevation view showing one end of the first embodiment of the present invention in the FIG. 3 configuration with ice moving against the rig;
  • FIG. 5 is a top view of a leg of the drilling rig with a first embodiment of the leg ice shields in place;
  • FIG. 6 is a top view of a leg of the drilling rig with a second embodiment of the leg ice shields in place;
  • FIG. 7 is an elevation view of the drilling rig with the first embodiment leg ice shields in place.
  • FIG. 8 is an elevation view of the drilling rig with the second embodiment leg ice shields in place.
  • an ice worthy jack-up rig is generally indicated by the arrow 10 .
  • jack-up rig 10 is shown with its hull 20 floating in the sea and legs 25 in a lifted arrangement where much of the length of the legs 25 extend above the deck 21 of the hull 20 .
  • the legs 25 are constructed of long posts with cross members connecting the posts in a truss arrangement.
  • derrick 30 On the deck 21 is derrick 30 which is used to drill wells.
  • the jack-up rig 10 may be towed from one prospect field to another and to and from shore bases for maintenance and other shore service.
  • the legs 25 are lowered through the openings 27 in hull 20 until the feet 26 at the bottom ends of the legs 25 engage the seafloor 15 as shown in FIG. 2 .
  • the feet 26 are connected to spud cans 28 to secure the rig 10 to the seafloor.
  • well drilling operations may commence in the ordinary course while there is no ice in the area.
  • ice begins to form on the sea surface 12
  • the risk of an ice floe contacting and damaging the legs 25 or simply bulldozing the jack-up rig 10 off the drilling site becomes a significant concern for conventional jack-up rigs and such rigs are typically removed from drill sites by the end of the open water season.
  • the ice-worthy jack-up drilling rig 10 is designed to resist ice floes by assuming an ice defensive, hull-in-water configuration as shown in FIG. 3 .
  • ice tends to dampen waves and rough seas, so the sea surface 12 appears less threatening, however, the hazards of the marine environment have only altered, and not lessened.
  • the hull 20 When the ice-worthy jack-up rig 10 assumes its ice defensive, hull-in-water configuration, the hull 20 is lowered into the water to contact same, but not to the extent that the hull 20 would begin to float. A significant portion of the weight of the rig 10 preferably remains on the legs 25 to hold the position of the rig 10 on the drill site against any pressure an ice flow might bring. The rig 10 is lowered so that inwardly sloped, ice-bending surface 41 bridges the sea surface 12 or ice/water interface to engage any floating ice that may come upon the rig 10 .
  • the sloped ice-bending surface 41 runs from shoulder 42 , which is at the edge of the deck 26 , down to neckline 44 . Ice deflector 45 extends downward from neckline 44 .
  • the ice-bending surface 41 causes the leading edge of the ice floe 51 to submerge under the sea surface 12 and apply a significant bending force that breaks large ice floes into smaller, less damaging, less hazardous bits of ice. For example, it is conceivable that an ice floe being hundreds of feet and maybe miles across could come toward the rig 10 . If the ice floe is broken into bits that are less than twenty feet in the longest dimension, such bits are able to pass around the rig 10 with much less concern.
  • Ice has substantial compressive strength being in the range of 4 to 12 MPa, but is much weaker against bending with typical flexure strength in the range of 0.3 to 0.5 MPa.
  • the force of the ice floe 51 moving along the sea surface 12 causes the leading edge to slide under the sea surface 12 and caused section 52 to break off.
  • the ice floe 51 broken into smaller floes, such as section 52 and bit 53 the smaller sections tend to float past and around the rig 10 without applying the impacts or forces of a large floe.
  • the ice deflector 45 is arranged to extend downwardly at a steeper angle than ice-bending surface 41 and will increase the bending forces on the ice floe.
  • an ice deflector is positioned to extend down from the flat of bottom of the hull 20 .
  • the turn of the bilge is the flat of bottom at the bottom end of the ice deflector 45 .
  • the feet 26 of the legs may be arranged to connect to cans 28 set in the sea floor so that when an ice floe comes against the ice-bending surface 41 , the legs 25 actually hold the hull 20 down and force the bending of the ice floe and resist the lifting force of the ice floe which, in an extreme case, may lift the near side of the rig 10 and push the rig over on its side by using the feet 26 on the opposite side of the rig 10 as the fulcrum or pivot.
  • the cans in the sea floor are known for other applications and the feet 26 would include appropriate connections to attach and release from the cans, as desired.
  • the ice-worthy jack-up drill rig 10 is designed to operate like a conventional jack-up rig in open water, but is also designed to settle to the water in an ice defensive position and then re-acquire the conventional stance or configuration when wave action becomes a concern. It is the shape of the hull 20 (as well as its strength) that provides ice bending and breaking capabilities.
  • leg ice shields 32 are attached between vertical posts 31 of the legs.
  • the leg ice shields 32 are bowed to provide a rounded shape to steer any ice around the legs.
  • the leg ice shields 33 are relatively flat.
  • the leg ice shields 32 and 33 are preferably positioned on the legs to extend above, below and across the waterline 12 but not necessarily cover the entire vertical length of each leg 25 .
  • leg ice shields provide some ice protection from the legs
  • the legs 25 and the openings 27 through which they are connected to the hull 20 are within the perimeter of the ice deflector 45 so that the ice floes are less likely to contact the legs 25 while the rig 10 is in its defensive ice condition configuration as shown in FIG. 3 and sometimes called hull-in-water configuration.
  • the rig 10 does not have to handle every ice floe threat to significantly add value to oil and gas companies. If rig 10 can extend the drilling season by as little as a month, that would be a fifty percent improvement in some ice prone areas and therefore provide a very real cost saving benefit to the industry.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Earth Drilling (AREA)
US13/278,480 2010-10-21 2011-10-21 Leg ice shields for ice worthy jack-up drilling unit Abandoned US20120128427A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US13/278,480 US20120128427A1 (en) 2010-10-21 2011-10-21 Leg ice shields for ice worthy jack-up drilling unit

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US40549710P 2010-10-21 2010-10-21
US13/277,791 US20120128426A1 (en) 2010-10-21 2011-10-20 Ice worthy jack-up drilling unit
US13/278,480 US20120128427A1 (en) 2010-10-21 2011-10-21 Leg ice shields for ice worthy jack-up drilling unit
PCT/US2011/057228 WO2012054808A1 (en) 2010-10-21 2011-10-21 Leg ice shields for ice worthy jack-up drilling unit

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US13/277,791 Continuation-In-Part US20120128426A1 (en) 2010-10-21 2011-10-20 Ice worthy jack-up drilling unit

Publications (1)

Publication Number Publication Date
US20120128427A1 true US20120128427A1 (en) 2012-05-24

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Application Number Title Priority Date Filing Date
US13/278,480 Abandoned US20120128427A1 (en) 2010-10-21 2011-10-21 Leg ice shields for ice worthy jack-up drilling unit

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US (1) US20120128427A1 (no)
CA (1) CA2804898A1 (no)
NO (1) NO20130547A1 (no)
RU (1) RU2013123039A (no)
WO (1) WO2012054808A1 (no)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9121155B2 (en) 2012-09-24 2015-09-01 Keppel Offshore & Marine Technology Centre Pte Ltd Ice resistant jackup leg

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3628336A (en) * 1969-04-28 1971-12-21 Offshore Co Drilling platform
US3696624A (en) * 1970-10-02 1972-10-10 Sun Oil Co Delaware Bucket wheel ice cutter
US3807179A (en) * 1972-10-02 1974-04-30 Gulf Oil Corp Deicing systems
US3972199A (en) * 1972-06-26 1976-08-03 Chevron Research Company Low adhesional arctic offshore platform
US4048943A (en) * 1976-05-27 1977-09-20 Exxon Production Research Company Arctic caisson
US4063428A (en) * 1975-08-26 1977-12-20 Heinrich Waas Method of deflecting ice at upright columns submerged in water of stationary or floating structures in marine areas in which the occurence of ice may be expected, and ice deflector assembly therefor
US4511288A (en) * 1981-11-30 1985-04-16 Global Marine Inc. Modular island drilling system
US4578000A (en) * 1982-06-15 1986-03-25 Oy Wartsila Ab Method of protection
US4987846A (en) * 1987-08-21 1991-01-29 Ishikawajima-Harima Jukogyo Kabushiki Kaisha Floating structure
US20070243024A1 (en) * 2004-09-07 2007-10-18 Offshore Technology Development Pte Ltd Jackup Oil Rig And Similar Platforms
US20080237173A1 (en) * 2007-03-30 2008-10-02 Remedial (Cyprus) Pcl Arm assembly and methods of passing a pipe from a first vessel to a second vessel using the arm assembly

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3669052A (en) * 1970-06-15 1972-06-13 Air Logistics Corp Method and apparatus for preventing ice damage to marine structures
NL7705518A (en) * 1977-05-18 1978-11-21 Rijn Schelde Verolme Maschf En Deicing equipment for vulnerable components on offshore installations - comprises automatically inflatable and deflatable flexible bodies secured detachably
US4102144A (en) * 1977-05-31 1978-07-25 Global Marine, Inc. Method and apparatus for protecting offshore structures against forces from moving ice sheets
FR2486562A1 (fr) * 1980-07-09 1982-01-15 Coyne Bellier Bureau Ingenieur Dispositif de fondation pour structure, telle qu'une plate-forme, notamment auto-elevatrice, reposant sur un fond sous-marin, et plates-formes de ce type
US4434741A (en) * 1982-03-22 1984-03-06 Gulf Canada Limited Arctic barge drilling unit
FI822158A7 (fi) * 1982-06-15 1983-12-16 Waertsilae Oy Ab Poraustasanne.
SU1661050A1 (ru) * 1986-12-15 1991-07-07 Предприятие П/Я Р-6109 Плавуча бурова установка
NL1000585C2 (nl) * 1995-06-16 1996-12-17 Marine Structure Consul Bodemsteunconstructie voor een pootuiteinde van een verplaatsbaar hefplatform.

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3628336A (en) * 1969-04-28 1971-12-21 Offshore Co Drilling platform
US3696624A (en) * 1970-10-02 1972-10-10 Sun Oil Co Delaware Bucket wheel ice cutter
US3972199A (en) * 1972-06-26 1976-08-03 Chevron Research Company Low adhesional arctic offshore platform
US3807179A (en) * 1972-10-02 1974-04-30 Gulf Oil Corp Deicing systems
US4063428A (en) * 1975-08-26 1977-12-20 Heinrich Waas Method of deflecting ice at upright columns submerged in water of stationary or floating structures in marine areas in which the occurence of ice may be expected, and ice deflector assembly therefor
US4048943A (en) * 1976-05-27 1977-09-20 Exxon Production Research Company Arctic caisson
US4511288A (en) * 1981-11-30 1985-04-16 Global Marine Inc. Modular island drilling system
US4578000A (en) * 1982-06-15 1986-03-25 Oy Wartsila Ab Method of protection
US4987846A (en) * 1987-08-21 1991-01-29 Ishikawajima-Harima Jukogyo Kabushiki Kaisha Floating structure
US20070243024A1 (en) * 2004-09-07 2007-10-18 Offshore Technology Development Pte Ltd Jackup Oil Rig And Similar Platforms
US20080237173A1 (en) * 2007-03-30 2008-10-02 Remedial (Cyprus) Pcl Arm assembly and methods of passing a pipe from a first vessel to a second vessel using the arm assembly

Also Published As

Publication number Publication date
NO20130547A1 (no) 2013-04-19
WO2012054808A1 (en) 2012-04-26
CA2804898A1 (en) 2012-04-26
RU2013123039A (ru) 2014-11-27

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AS Assignment

Owner name: CONOCOPHILLIPS COMPANY, TEXAS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:NOBLE, PETER G.;SHAFER, RANDALL S.;BERTA, DOMINIQUE P.;AND OTHERS;SIGNING DATES FROM 20120117 TO 20120118;REEL/FRAME:027652/0131

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION