Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63C—LAUNCHING, HAULING-OUT, OR DRY-DOCKING OF VESSELS; LIFE-SAVING IN WATER; EQUIPMENT FOR DWELLING OR WORKING UNDER WATER; MEANS FOR SALVAGING OR SEARCHING FOR UNDERWATER OBJECTS
  • B63C3/00—Launching or hauling-out by landborne slipways; Slipways
  • B63C3/04—Launching or hauling-out by landborne slipways; Slipways by sideways movement of vessel
• • 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
  • E21B15/00—Supports for the drilling machine, e.g. derricks or masts
  • E21B15/003—Supports for the drilling machine, e.g. derricks or masts adapted to be moved on their substructure, e.g. with skidding means; adapted to drill a plurality of wells
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B77/00—Transporting or installing offshore structures on site using buoyancy forces, e.g. using semi-submersible barges, ballasting the structure or transporting of oil-and-gas platforms
• • 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
  • E21B15/00—Supports for the drilling machine, e.g. derricks or masts
  • E21B15/02—Supports for the drilling machine, e.g. derricks or masts specially adapted for underwater drilling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B73/00—Building or assembling vessels or marine structures, e.g. hulls or offshore platforms
  • B63B73/40—Building or assembling vessels or marine structures, e.g. hulls or offshore platforms characterised by joining methods
  • B63B73/43—Welding, e.g. laser welding

Definitions

• This invention generally relates to construction of offshore structures and more particularly to a method of building two (or more) semi-submersible drilling rigs simultaneously in a shipyard using a dry dock mating process.
• the mating operation is subsequently carried out by floating up the lower hull in the dry dock until it meets and supports the upper hull.
• the welding of the upper and lower hulls' joint is finally performed. In doing so, the complete mating operation is conducted in a controllable condition, which ensures the safety as well as the quality of the operation.
• This method allows building and assembling only one semi-submersible rig at a time.
• the upper hull will have to be erected and assembled on the slddding truss and therefore the second load-out and mating operation may only be carried out several months later.
• the present invention contemplates elimination of some drawbacks associated with prior methods and provision of a method of contemporaneous construction of two or more semi-submersible vessels.
• an object of the present invention to provide a method of constructing two (or more) semi-submersible rigs simultaneously in a safe, secure manner at a relatively low cost.
• the upper hull of the first rig is completely erected at land side near the end of a dry dock on a skidding truss and supporting towers, while that of the second rig is completely erected at land side and positioned on a skid way oriented transversely to the skidding truss holding the first upper hull.
• the lower hull of the first rig is constructed in a dry dock adjacent to the slddding truss, whilst that of the second rig is constructed at another location in the yard.
• a supporting truss is installed in the dry dock to support a plurality of skidding beams extending from the upper hull construction site at land side to the mating position above the lower hull in the dry dock.
• the first upper hull is loaded out to the mating position by skidding on the skidding beams using a hydraulic jacking system.
• the mating operation is subsequently carried out by floating up the lower hull in the dry dock until it meets and supports the upper hull.
• the welding of the upper and lower hulls' joint is finally performed for the first rig.
• the upper hull of the second rig is moved from its erection location to the load-out location by slddding transversely on a skid way.
• the second upper hull is subsequently jacked up to a height so that the skidding truss can be retrieved from the mating location in the dry dock and positioned underneath the second upper hull.
• the upper hull is then lowered down and eventually rested on the skidding truss.
• the completed rig is pulled out of the dry dock and the lower hull of the second rig is towed into the mating location in the dry dock.
• the second rig's load-out and mating operation is then carried out in exactly the same way as that of the first rig.
• FIG. 1 is the plan view of the load-out, mating and transverse skidding operation arrangement.
• FIG. 2 is a longitudinal profile view showing the first upper hull supported on the skidding truss and the load-out structures and equipment (such as longitudinal skidding beam and shoes, supporting truss in dry dock, tie bars, barges, jacking system, strand wire).
• the load-out structures and equipment such as longitudinal skidding beam and shoes, supporting truss in dry dock, tie bars, barges, jacking system, strand wire.
• FIG. 3 is a transverse profile view showing the second upper hull supported on temporary blocks.
• FIG. 4 is a detail view showing the transverse slcidding-and-pushing-up shoes positioned under the upper hull and taking over the weight of the upper hull.
• FIG. 5 shows the step of load-out and mating operation of the first rig in dry dock.
• FIG. 6 shows a step of skidding the second upper hull transversally from its erection location to load-out location.
• FIG. 7 shows the step of jacking up the second upper hull at the load-out location.
• FIG. 8 illustrates the retrieval of skidding truss from mating location back to load-out location underneath the second upper hull.
• FIG. 9 illustrates the operations of pulling completed first rig out and positioning the second rig lower hull in mating location.
• FIG. 10 illustrates the steps of the load-out and mating of the second rig.
• Figures 1 - 3 show the general arrangement of the shipyard area including the dry dock 4, where the two -submersible rigs of the present invention are constructed and mated.
• the first semi-submersible rig comprises a first upper hull Ia and a first lower hull 2a.
• the first upper hull Ia is supported by a skidding truss 3 located on land adjacent to the dry dock 4.
• the truss 3 is designed to skid the completed upper hull Ia on longitudinal skidding beams 5 using longitudinal skidding shoes 6 during the load-out operation.
• the longitudinal skidding beams 5 extend in parallel to a longitudinal axis of the skidding truss 3.
• a detailed configuration of the structures required for load-out and mating operation is disclosed in further detail in the earlier application entitled "A Method of Constructing a Semi-submersible Vessel Using Dry Dock Mating” (International Publication No. WO 2005/035354 Al).
• the second upper hull Ib is being constructed next to the first upper hull 1 a on a transverse skid way with a pair of stationary transverse skid beams 9.
• the second upper hull is supported on the skid beams 9 by temporary support blocks 7 (Fig. 3).
• the transverse skid beams 9 each have a longitudinal axis, which is oriented transversely to the longitudinal axis of the skidding truss 3.
• the temporary blocks 7 are stationary and are located at a level considerably lower than the skidding truss 3, which supports the first upper hull Ia.
• transverse- skidding- and-pushing-up shoes 8 are positioned underneath the second upper hull Ib on the transverse skid way 9 (Fig. 4). The shoes 8 are then pushed up to take over the weight of the second upper hull Ib from the temporary support blocks 7.
• FIG. 5 illustrates the steps of load-out and mating of the first rig.
• the first upper hull Ia is pulled from the load-out location to the mating location above the dry dock 4.
• the first lower hull is floated by flooding the dry dock 4, and position of the lower hull is adjusted using the ballast tanks of the first lower hull 2a.
• the first lower hull 2a is floated up until the column tops of the first lower hull 2a touch the bottom of the first upper hull Ia. Then, the temporary guide pieces at the upper and lower hulls joints are welded. Meanwhile, the first lower hull 2a is continuously floated until it supports the weight of the first upper hull Ia and the gap between the first upper hull Ia and the first lower hull 2a is closed. Sufficient welding at upper and lower hulls joints permanently attaches the first lower hull 2a to the first upper hull Ia.
• the next step in the process involves skidding the second upper hull Ib transversally from its erection location to load-out location near the end of dry dock 4 (FIG. 6).
• the skidding operation is performed by a plurality of skidding-and-pushing-up shoes 8 positioned on the transverse skid way beams 9.
• the second upper hull Ib is pushed up by the skidding-and-pushing-up shoes 8 to a height sufficient to accommodate the skidding truss 3 (to be pulled back in next step) underneath with acceptable clearance in between (FIG. 7).
• the second upper hull Ib is pulled from the load-out location along the skidding truss 3 to the mating location above the dry dock 4.
• the second lower hull 2b is ballasted and floated up until the column tops of the second lower hull 2b touch the bottom of the first upper hull Ia. Similar to the construction process of the first rig, the temporary guide pieces at the upper and lower hulls joints are welded.
• the second lower hull 2b is continuously floated until it supports the weight of the second upper hull Ib and the gap between the second upper hull Ia and the second lower hull 2b is closed.
• the second upper hull Ib and the second lower hull 2b are then permanently joined together by welding.
• Figure 10 illustrates the second rig's load-out and mating operation which generally repeats the load-out and mating operation for the first rig.
• the method of the present invention provides the advantages of allowing to construct two (or more) semi-submersible rigs substantially contemporaneously employing the steps of sequential longitudinal load-out and mating operations in dry dock and the transverse skidding operation at land side of dock end. By doing so, the overall construction period for two rigs is substantially shortened. In effect, two rigs can be fabricated at the same time using conventional shipyard facilities.
• more than two rigs can be constructed contemporaneously in a conventional shipyard, with one of the upper hulls Ia being erected on the skidding truss 3, while other upper hulls 2a are being constructed in close vicinity thereto.
• the second upper hull Ib can be elevated above the skidding truss 3 and transferred to the skidding truss 3.
• the skidding truss 3 becomes free again (following transfer of the second upper hull 2a to a mating position in the dock), the next upper hull is transferred to the skidding truss and so on. All final mating operations are conducted in the same dry dock.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Geology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Ocean & Marine Engineering (AREA)
• Fluid Mechanics (AREA)
• Combustion & Propulsion (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Physics & Mathematics (AREA)
• Transportation (AREA)
• Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Conveying And Assembling Of Building Elements In Situ (AREA)
• Automatic Assembly (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Working Measures On Existing Buildindgs (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Drying Of Solid Materials (AREA)
• Earth Drilling (AREA)

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Publications (1)

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• 2006
  • 2006-09-25 SG SG200606560-1A patent/SG141277A1/en unknown
• 2007
  • 2007-09-24 CN CN2007800027727A patent/CN101370708B/zh active Active
  • 2007-09-24 KR KR1020087015432A patent/KR101395773B1/ko active IP Right Grant
  • 2007-09-24 WO PCT/SG2007/000321 patent/WO2008039155A1/en active Application Filing
  • 2007-09-26 TW TW096135741A patent/TWI380932B/zh active
• 2008
  • 2008-07-04 NO NO20082967A patent/NO338374B1/no unknown

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