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
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02B—HYDRAULIC ENGINEERING
  • E02B1/00—Equipment or apparatus for, or methods of, general hydraulic engineering, e.g. protection of constructions against ice-strains
• • 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
• • 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
• • 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
  • E21B7/00—Special methods or apparatus for drilling
  • E21B7/008—Drilling ice or a formation covered by ice
• • 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.
• 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 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.
• the rig further includes a moon pool in the deck and positioned within the perimeter of the bottom of the hull and inside the ice deflecting portion.
• 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 legs are positioned within the perimeter of the bottom of the hull.
• 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.
• the method includes drilling through a moon pool in the deck that is positioned within the perimeter of the bottom of the hull and inside the ice deflecting portion.
• Figure 1 is an elevation view of the present invention where the drilling rig is floating in the water and available to be towed to a well drilling site;
• Figure 2 is an elevation view of the present invention where the drilling rig is jacked up out of the water;
• Figure 3 is an 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;
• Figure 4 is an enlarged fragmentary elevation view showing one end of the first embodiment of the present invention in the Figure 3 configuration with ice moving against the rig;
• Figure 5 A is an elevation view showing the derrick is in a cantilevered position drilling over the side of the deck in the conventional manner of a conventional jack-up drilling rig;
• Figure 5B is a partially fragmentary elevation view where a moon pool is shown included in the hull so that the drill string benefits from the ice protection of the ice worthy hull configuration;
• Figure 6A is a top view of the first embodiment of the present invention where a cantilever derrick is positioned to drill through the moon pool;
• Figure 6B is a top view of the first embodiment of the present invention where a cantilever derrick is positioned to drill over the edge of the deck.
• 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.
• 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 Figure 2.
• the feet 26 are connected to spud cans 28 to secure the rig 10 to the seafloor.
• jacking rigs within openings 27 push the legs 25 down and therefore, the hull 20 is lifted out of the water. With the hull 20 fully jacked-up and out of the water, any wave action and heavy seas more easily break past the legs 25 as compared to the effect of waves against a large buoyant object like the hull 20.
• the ice-worthy jack-up drilling rig 10 of the present invention is designed to resist ice floes by assuming an ice defensive, hull-in- water configuration as shown in Figure 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 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.
• the cantilevered derrick 30 is positioned to drill over the side of the deck 20 in accordance with conventional jack-up drilling rigs.
• Rig 10 of course includes the ice worthy hull 20, so the system illustrated in Figure 4A is not entirely conventional.
• 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.
• ice not be forced under the flat of bottom of the hull 20 and the ice deflector 45 turns ice to flow around the side of the hull 20.
• 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.
• the hull (as viewed from above) may have a circular or oval configuration so as to present a shape that is conducive to steering the broken bits and sections of ice around the periphery of the rig 10 regardless of the direction of origin or path of travel.
• the ice tends to flow with the wind and sea currents, which tend not to be co-linear, or some path reflecting influences of both sea and air.
• the hull 20 preferably has a faceted or multisided shape that provides the advantages of a circular or oval shape, and may be less expensive to construct.
• the plates that make up the hull would likely be formed of flat sheets and so that the entire structure comprises segments of flat material such as steel would likely require less complication.
• the ice-breaking surface would preferably extend at least about five meters above the water level, recognizing that water levels shift up and down with tides and storms and perhaps other influences. The height above the water level accommodates ice floes that are quite thick or having ridges that extend well above the sea surface 12, but since the height of the shoulder 42 is well above the sea surface 12, the tall ice floes will be forced down as they come into contact with the rig 10.
• the deck 21 at the top of the hull 20 should be far enough above the water line so that waves are not able to wash across the deck.
• the deck 25 is preferred to be at least 7 to 8 meters above the sea surface 12.
• the neckline 42 is preferred to be at least 4 to 8 meters below the sea surface 12 to adequately bend the ice floes to break them up into more harmless bits.
• the hull 20 is preferably in the range of 5-16 meters in height from the flat of bottom to the deck 20, more preferably 8- 16 meters or 11-16 meters.
• 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 while the rig 10 is in its defensive ice condition configuration as shown in Figure 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.
• the derrick 30 may be positioned to drill through a moon pool that is within the perimeter of the ice deflector 45 as shown in Figure 5 a or may be arranged to drill over the side of the deck 21 in a cantilevered fashion as shown in Figure 5b.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Life Sciences & Earth Sciences (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)
• Earth Drilling (AREA)

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• 2011
  • 2011-10-21 EP EP11779047.7A patent/EP2630302A1/en not_active Withdrawn
  • 2011-10-21 KR KR1020137009996A patent/KR20130120460A/ko not_active Application Discontinuation
  • 2011-10-21 CA CA2811943A patent/CA2811943A1/en not_active Abandoned
  • 2011-10-21 RU RU2013123031/03A patent/RU2013123031A/ru unknown
  • 2011-10-21 WO PCT/US2011/057366 patent/WO2012054883A1/en active Application Filing
  • 2011-10-21 US US13/279,084 patent/US20120128432A1/en not_active Abandoned
  • 2011-10-21 SG SG2013022322A patent/SG189100A1/en unknown
  • 2011-10-21 CN CN2011800504385A patent/CN103168133A/zh active Pending

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