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
  • E02B17/02—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
  • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
• • 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
  • E02B2017/0052—Removal or dismantling of offshore structures from their offshore location
• • 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

Definitions

• This invention relates to a multi-functional jack-up for decommissioning offshore platform, such as oil or gas rigs or platforms.
• FIG 1 shows a fixed offshore platform 100 used for drilling and production of oil or gas offshore.
• a platform 100 is the most common offshore structure used for mining oil or gas.
• the fixed offshore platform 100 comprises a superstructure 102 supported by a jacket 04.
• the jacket comprises tubular members interconnected together to form a 3-dimensional frame including a number of jacket legs 106.
• the jacket 104 is anchored to the seabed by driving main piles through the jacket legs 106 to provide stability against overturning moment caused by waves or extreme weather conditions.
• the superstructure 102 normally includes a few levels and as shown in Figure 1 , this includes a production deck 108 and a skid deck 1 0.
• the offshore platform 100 also includes conductor pipes 1 12 set in the seabed to provide the necessary foundations for a wellhead.
• the conductor pipes 112 are configured to provide passage for drilling fluid and drill string to be lowered down into the wells and the fluid and cuttings to flow back to the rig as well as to prevent formations near the well from caving into the wellbore
• the skid deck 110 is configured to support a drilling rig (not shown in Figures 1 and 2).
• the offshore platform 100 would have several well slots in various configurations (i.e. 4 x 6, 5 x 3, etc). These well slots are located between the skid beams.
• the drilling rig is typically equipped with skidding jacks. These skidding jacks are latched onto the skid beams and enable the drilling rig to skid from one well slot to the other well slots.
• the offshore platform 100 includes living quarters 113 and a helicopter pad 1 4 located above the living quarters 113.
• the offshore platform 100 includes a platform crane 1 5 configured for specific lifting operations at the offshore platform 100.
• the platform crane 115 does not have sufficient boom reach and lifting capacity to support all the activities at offshore platform (e.g. decommissioning operation). It is estimated that to-date, more than 4,000 offshore platforms have been built and in operation around the world, with around 150 platforms currently under construction. Typical life period of the offshore platform is approximately 20 to 30 years, but if the oil or gas well is not producing sufficient oil or gas to justify the existence of the offshore platform, it is decommissioned which involves flushing, plugging and cementing the well to make it safe to the environment. In certain cases, the offshore platform may have deteriorated to an extent that it is no longer safe to work on the platform and thus, the platform may have to be decommissioned too.
• Single lift removal method involves a floating crane vessel which is capable of heavy lifts to lift the topside deck in a single lift.
• the topside deck covers everything from the production deck 108 all the way until the highest structure of the platform 100. In other words, topsides are all the things aside from the jacket 104 and the conductors 112.
• Reverse installation method is a method whereby the topsides of the platform are dismantled into modules in the reverse order of how the topsides were assembled during installation. Reverse installation requires a vessel with lower lifting capacity compared to the single lift removal method, according to the heaviest modules which made up the topsides.
• Piecesmall removal method involves cutting and segregating the topsides into small pieces using equipment such as excavators, cranes, etc which are loaded onto containers. The containers are then transported to the decommissioning vessel or to supply vessels for onshore disposal.
• plugging of the offshore wellhead and abandoning of the offshore well are first performed with a drilling/workover rig, i.e. a jack up or a modular rig, or without a drilling/workover rig (rigless), i.e. a well intervention vessel.
• rigless P&A operation is limited to category 1 or 2 wells.
• a category 1 well is a well which requires it to be plugged and abandoned and ready to be picked up after cutting the wellhead off.
• a category 2 well requires slight intervention work, such as removal of mud or perforated annuli.
• a category 3 well requires well control, including the use of tubing.
• a multifunctional jack-up for decommissioning an offshore platform; the jack-up comprising a hull supportable by a number of jack-up legs; a cantilever platform movably mounted to the hull; a first lifting device and a second lifting device mounted to the cantilever platform and arranged to be operable independently from each other.
• Decommissioning an oil rig is an act of removal of the offshore well rig according to regulatory requirements to make the well rig safe to the environment.
• the well rig may be a oil and/or gas rig.
• the decommissioning involves flushing, plugging and cementing wells to make the wells safe.
• the described embodiment aims to introduce flexibility during the well plugging and abandonment by utilizing the multifunctional jack up as a tender assist vessel which supports the offshore platform (e.g. well rig) during the plugging and abandonment operation.
• the multifunctional jack-up is able to perform decommissioning of the offshore platform. Specifically when the jack-up acts as decommissioning vessel and with the first and second lifting devices operable independently, the well plugging and abandonment and platform structural removal of structures (buildings, helicopter pad etc) of the offshore platform may be performed simultaneously and this reduces the overall platform decommissioning duration and cost.
• the described embodiment is preferably used based on either the piece-small removal method or the reverse installation method for platform structure removal.
• the cantilever platform may include a storage compartment for storing equipment for the decommissioning operation. In this way, space at the cantilever platform or jack-up is optimized.
• the cantilever platform may include a skidding mechanism configured to skid the cantilever platform between a first position in which the cantilever platform is within boundaries of the hull, and a second position in which the cantilever platform extends at least partially out of the hull's boundaries.
• the first lifting device is movably mounted to the cantilever platform.
• the second lifting device may be mounted to a corner of the cantilever platform to maximize the reach of the second lifting device.
• the second lifting device is configured to feed tubulars from the jack-up to a drilling rig for plug and abandonment operation of a wellhead of the well rig.
• the multifunctional jack-up may further comprise means for assembling a modular drilling rig on the offshore platform for plugging and abandoning the wellhead.
• a method of decommissioning an offshore well rig using a multi-functional jack-up comprising: extending the cantilever platform; and operating the first lifting device and the second lifting device independently to decommission the offshore platform.
• the method may further comprise operating the first lifting device to perform lifting operations to remove topside structures from the offshore platform; and simultaneously operating the second lifting device to provide tubulars for plugging and abandoning a wellhead of the offshore platform.
• the method may further comprise operating scrapping tools on the offshore platform for removal of topside structural parts of the offshore platform.
• Figure 1 is a perspective view of a known fixed offshore platform for mining oil and/or gas
• Figure 2 is a front view of the fixed offshore platform of Figure 1 ;
• Figure 3 is a perspective view of a multi-functional jack-up having a movable cantilever platform according to a preferred embodiment of this invention with the multifunctional jack-up arranged to decommission the fixed offshore platform of Figure 1 ;
• Figure 4 is a side close-up view of the arrangement of Figure 3;
• Figure 5 is a top view of the arrangement of Figure 3;
• Figure 6 is a perspective close-up view of the cantilever platform of Figure 1 being arranged to support a mobile crane and a tubular handling crane;
• Figure 7 is a side view of the cantilever platform of Figure 6;
• Figure 8 is a perspective close-up view of the tubular handling crane of Figure 6 in operation
• Figure 9 is a perspective close-up view of the tubular-handling crane of Figure 6 in operation illustrating transfer of tubulars from the jack up to the fixed offshore platform of Figure 3;
• Figure 10 illustrates a drilling rig being constructed on the offshore platform of Figure 1 for plug and abandonment operation
• Figures 11 and 12 are different side views of the drilling rig and offshore platform of Figure 10;
• Figure 13 is a typical activity flowchart for plugging and abandoning of offshore wells.
• Figure 3 is a perspective view of a multi-functional jack-up 200 according to a preferred embodiment of the invention and the multi-functional jack-up 200 is arranged to decommission the fixed offshore platform 100 of Figure 1.
• Figure 4 is a side view of the arrangement of Figure 3
• Figure 5 is a top view of the arrangement of Figure 3.
• the multi-functional jack-up 200 comprises a triangular-shaped hull 202 having a main deck 204, three triangular-shaped lattice bracing legs 206 (a first one 206a at the forward side 207, and two legs 206b,2O6c at the aft side 209) arranged to support the hull 202.
• the legs 206 are supported by respective spud cans 205 attached to a jacking system installed in jack cases 217 mounted on the main deck 204 of the hull 202.
• the jack cases 217 enable the hull .202 to be jacked up and down to raise its height in relation to the ends of the legs 206, subject to the operating area i.e. water depth as well as wave height in the area which the jack-up 200 is operating.
• the multi-functional jack-up 200 includes accommodation unit 208 arranged above the first leg 206a at the forward side 207 for providing living quarters for the crew, a helicopter deck 210 cantilevered adjacent to the accommodation unit 208, and two pedestal cranes 212,214 mounted respectively at the port and starboard side of the multi-functional jack up 200.
• the pedestal cranes 212,214 at the port and starboard side of the hull 202 are used for material handling within the jack-up 200 and/or between the jack-up and the supply vessels. The reason that there are two cranes 212,214 on each side of the hull 202 is to be able to cover the whole jack up area during material handling.
• the multi-functional jack-up 200 further includes a cantilever platform 216 provided near the aft side 209 of the main deck 204 and this is shown more clearly in Figure 4 and also Figures 6 and 7 which are close-up views of the cantilever platform 216.
• the cantilever platform 216 is coupled a set of skidding system (not shown) mounted on the main deck 204 so that the cantilever platform 216 is skiddable (or extendable) beyond the aft side 209 of the main deck 204.
• the skidding system comprises four hydraulic cylinders, each fitted with a clamp at its end and fixed to the main deck 204 at its other end. The clamp fitted to the cylinders is used to grip the skidding beams/tracks of the cantilever platform 216.
• the cantilever platform 216 includes a cantilever housing 218, a top deck 220 arranged on top of the cantilever housing 218 and two elongate engagement shoes 222,224 arranged to support the cantilever housing 218, The elongate engagement shoes 222,224 are arranged to engage tracks of the skidding system provided on the main deck 204 to enable the cantilever platform 216 to skid longitudinally.
• the top deck 220 of the cantilever platform 216 is arranged with two parallel crane skidding beams 226,228 (see Figures 5 and 6) and is arranged to cooperate with a skidding base 230 (see Figure 6) of a mobile crane 232 to enable the mobile crane 232 to travel along the top deck 220 of the cantilever platform 216.
• the cantilever platform 216 includes two long edges 234,236 and shorter front and rear edges 238,240, and the skidding beams 226,228 extends along the length of the long edges 234,236 from near the front edge 238 to near the rear edge 240 so that the skidding beams 226,228 provide a guided movement for the mobile crane 232.
• An example of the skidding beams 226,228 and the skidding base 230 may be understood from US 2008/0237174.
• Figure 5 shows the cantilever platform 216 in an extended position (i.e. with the cantilever platform 216 extended belong the aft side 209 of the main deck 204) and the mobile crane 232 moved to one end of the skidding beams 226,228 adjacent to the front edge 238 of the cantilever platform to maximize the reach of the mobile crane 232.
• FIGs 6 and 7 are close-up views of the mobile crane 232 of Figure 3 and the mobile crane 232 includes the skidding base 230, a slew bearing 242 mounted to the skidding base 230, a control cabin 244 for a crane operator and a lattice boom 246 hinged to the boom pivot joint.
• the mobile crane 232 is configured to assist with removal of parts of the superstructure 102 of the offshore platform 100 by lifting loads between the offshore platform 100 and the multifunctional jack-up 200 or a supply vessel (not shown).
• the cantilever platform 216 includes a second lifting device and this is in the form of a tubular-handling crane 248 arranged at a corner common to the front edge 238 and one of the sides 234 of the cantilever platform 216.
• the tubular-handling crane 248 is configured to support the drilling or plug and abandonment activity of the well of the offshore platform 100 and operates independently and separately from the mobile crane 232. It is preferred to position the tubular-handling crane 248 at a tip or corner of the cantilever 216 in order to maximize the crane's reach.
• the top deck 220 of the cantilever platform 216 is arranged with pipe rack as well as loading/unloading area, through which the transfer of material between the jack up 200 and the offshore platform 100 occurs. Sufficient reinforcements on the top deck 220 of the cantilever platform 216 are required to enable the cantilever platform 216 to withstand the load and activities on the top deck 220.
• FIG 8 is a close-up view of the tubular handling crane 248 of Figure 3.
• the cantilever platform 216 includes a crane pedestal 249 located at the corner of the cantilever platform 216 as explained above.
• the crane pedestal 249 includes crane slew bearings to which the tubular handling crane 248 is mounted.
• the crane slew bearings allow the tubular handling crane 248 to rotate 360 degrees about a slewing axis, which is a vertical central axis of the crane slew.
• the tubular handling crane 248 comprises a main boom 250 and a jib 251 connected to the main boom 250 via a boom pin joint 256.
• the main boom 250 is pivotably coupled to a crane mover house 259 via a boom pivot joint 257.
• the tip of the jib 251 is fitted with a pipe gripper 252 and the gripper 252 is interchangeable with a conventional hook block (not shown).
• the pipe gripper 252 or the hook block is configured for transferring tubulars 253 between the jack-up 200 and the offshore platform 100.
• the boom 250 and jib 251 are able to be knuckled by extending or retracting hydraulic cylinders 254 connected to the boom 250 and the jib 251.
• a control cabin 255 is located adjacent to the crane mover house 259.
• a winch 258 is installed on top of the crane mover house 259 and used when the jib 251 is fitted with the hook block.
• the pipe gripper 252 is able to rotate about the slew axis 340 degrees in order to provide flexibility in aligning the tubulars to the unloading area.
• tubular handling crane 248 of this embodiment has an advantage of both options as the pipe gripper 252 and the hook block is interchangeable.
• the mobile crane 232 includes the lattice boom 246 whereas the tubular handling crane 248 includes a knuckled boom (i.e. formed by the boom 250 and the jib 251 pivotably coupled to each other). As a result, both cranes 232,248 are able to complement each other's lifting operations.
• the tubular handling crane 248 is mounted at the corner of the cantilever platform 216 to maximize its reach. As for the mobile crane 232, this is usually much heavier and due to the type of lifting operations, locating the mobile crane 232 near the centre of the cantilever platform 216 is advantageous to avoid any excessive bending on the cantilever lateral ends.
• the cantilever housing 218 is configured as a storage compartment for storing a majority of equipment required for the decommissioning operation and this saves space which is a constraint at the multi-functional jack-up 200 and even the offshore platform 100.
• the cantilever housing 218 includes a hatch (not shown) between the two parallel crane skidding beams 226,228 for access to the storage compartment.
• the cantilever housing 218 is arranged with internal compartments which houses the following, but not limited to mud processing equipment and mud processing tanks, cementing unit, cement mixing equipment, cement tanks, hydraulic power unit (HPU), local electrical room (LER) complete with variable frequency drives (VFDs) and motor control centres (MCCs) for a drilling rig 300, coiled tubing unit, room for BOP control unit and stores for drilling equipment spare parts.
• the equipment is installed in the cantilever during construction phase.
• Figures 10 to 12 show the drilling rig 300 more clearly and the drilling rig 300 or a workover rig is a modular drilling rig having a mast 302, drawworks 304, top drive (not shown) for providing rotation motion to a drill string when performing the drilling operation, blowout preventer (BOP) 306 and other required drilling apparatus.
• the drilling rig 300 may be equipped with offline standbuilding equipment to enable faster operation.
• the drilling rig 300 includes a support frame 308 for supporting the mast 302 and the other parts on the offshore platform 100.
• the support frame 308 enables the mast 304 to skid in two directions by the use of skidding units mounted either on the support frame 308, or on both the support frame 308 and drill floor 3 0, in order to accommodate various wellheads arrangement on the offshore platform 100.
• the drilling rig is configured for well plug and abandonment activities.
• the drilling rig 300 is used to perform well plugging and abandonment, special attention is to be placed on the top drive, whereby the top drive is required to produce a high torque rating for casing milling during the plugging and abandonment of the offshore wells.
• the drilling rig 300 is modularized and stored in several rig containers during transit, and assembled on the platform upon the jack up's 200 arrival.
• FIG. 13 is a flow chart which illustrates the steps for the plug and abandonment operation performed with assistance of the modular drilling rig 300.
• the tubular handling crane 248 performs lifting operation of tubulars for the drilling rig 300 to lower downhole tools required for various operations. Examples of such operations are setting up the plug or doing perforations.
• the drilling rig 300 is configured to support the tubulars (as lifted by the tubular lifting crane 248) so that the tubulars lower the plug until it reaches the required depth.
• the cantilever platform 216 Prior to launching the multi-functional jack-up 200 to the location of the offshore platform 100, the cantilever platform 216 is in its retracted position within the boundaries of the main deck 204 and the mobile crane 232 skidded to its rest position which is at the end of the beams 226,228 nearest to the rear edge 240 of the cantilever platform 216.
• the required equipment and stores are also loaded up to the jack-up 200.
• the modularized rig containers are stored on the jack up main deck 204.
• Required tubulars to perform well plug & abandonment and use by the drilling rig 300, excavators, crawler cranes and other required equipment for platform decommissioning are stored on the main deck 204 of the jack up 200.
• the rig containers, tubulars, excavators, crawler cranes and other required equipment may be delivered to location by the use of supply vessels.
• the multi-functional jack-up 200 is then towed with its legs 206 up and the hull 202 floating on the water to the location of the offshore platform 100.
• the jack up 200 Upon arrival on location, the jack up 200 is jacked to a level by lowering the legs 206 to anchor the jack-up 200 to the seabed. The jack-up 200 is jacked until the main deck 204 of the hull 204 is approximately at a same elevation with the skid deck 110 of the offshore platform 00 while still maintaining an air gap requirement for operation at the offshore platform 100. Next, the cantilever platform 216 is skidded to its maximum longitudinal reach and extends beyond the aft side 209 of the main deck 204.
• the mobile crane 232 With the cantilever platform 216 in its extended position, the mobile crane 232 is moved or guided to move along the beams 226,228 to position the mobile crane 232 as close to the front edge 238 of the cantilever platform 216 as possible to maximize the mobile crane's reach.
• the rig containers containing the modular parts of the drilling rig 300 are then lifted from the jackup 200 onto the skid deck 1 0 of the offshore platform 100by the mobile crane 232 and assembled again with the assistance of the mobile crane 232. Connections for power cable, mud , water, cement, air and other utilities are made once the drilling rig 300 has been completely assembled and the drilling rig 300 is ready to perform the well plug and abandonment operation.
• Typical platform removal or decommissioning activity involves the following phases:
• the present embodiment may be used to perform the first 3 phases; 1 ) offshore preparation, 2) well plugging & abandonment, and 3) topsides removal.
• the removal activity may require additional equipment, such as excavators with cutting tool attached at its boom tip, cherry picker and/or crawler cranes.
• the excavators, cherry pickers and/or crawler cranes are lifted by the mobile crane 232 from the jack up 200 onto the working area of the offshore platform 100 to begin the offshore preparation phase, which includes "frontrunning".
• Frontrunning includes removal of all light material and/or equipment, removal of hazardous waste, removal of cables and electrical apparatus as well as drainage and sniffing. The removal of the light material and/equipment is performed by the excavators with cutting tools and crawler cranes. Basically, "frontrunning” removes all the material/equipment/portion of the platform which does not interfere with the structural integrity of the platform 100 (i.e. when they are removed, the platform 100 is still able to stay standing). For example, air handling unit (AHU) may be removed during "frontrunning” because even if the AHU is removed, the platform 100 can still stand.
• AHU air handling unit
• Structural removal or top sides removal (i.e. phase 3) follows upon completion of "frontrunning".
• Excavators with cutting tool perform the cold cutting works on the structural members of the offshore platform 100.
• the structural members are basically any structure which made up the platform 100 and this may include deck plating, stiffeners, beams, columns, etc.
• the production deck 108 and skid deck 1 10 are part of platform structural members. Scraped parts from the structural members are then loaded into containers, and the mobile crane 232 is arranged to lift these containers from the offshore platform 100 to the jack- up main deck 204.
• the boom of 246 of the mobile crane 232 provides a much wider working area and reach (covering all possible working area on the platform 100) and thus, the multifunctional jack-up 200 need not be positioned too close to the offshore platform 100 and yet the decommissioning operation may still be performed effectively. If required, additional processing, such as hot works, on the scraped parts may be done at the jack up 200 thus, alleviating the space constraints of the offshore platform 100.
• the containers containing the scraped parts are then transported to supply vessels by using the jack up pedestal cranes 212,214 for disposal which frees up the mobile crane 232 to focus on the decommissioning of the platform 100.
• the platform structure may be removed using the reverse installation method.
• the offshore platform 100 is dismantled in the reverse order of how the topsides were assembled during installation and the mobile crane 232 is used to lift the dismantled modules of the offshore platform 100 to the jack up 200 or directly to supply vessels.
• the "dismantled modules" are similar to the "scraped parts" of the piece-small removal method.
• the yard will construct module by module (i.e. living quarter module, storage tank module, etc). These modules are then joined together to form the platform 100.
• Reverse installation basically dismantles the platform 100 in the reverse order to how the modules are assembled together during construction phase.
• the ability to perform the removal operation and the well-plug and abandonment operation simultaneously results in substantial time savings and thus, cost savings.
• the combination of the cantilever platform 200, the mobile crane 232 and tubular-handling crane 248 enables the jack up 200 to perform simultaneous operations, well plug and abandonment or tender assist drilling and offshore platform 100 decommissioning.
• the described embodiment is not to be construed as limitative.
• the embodiment describes the decommissioning of the fixed offshore platform 100 but the present invention may be used for decommissioning other oil or gas rigs such as floating offshore platforms or semi-submersible platforms.
• the multifunctional jack-up 200 in the described embodiment includes two pedestal cranes 2 2,2 4, but these may not be necessary and the mobile crane 232 may be used for lifting operations at the jack-up 200, although this may not be preferred.

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Cited By (16)

Citations (7)

• 2011
  • 2011-07-12 WO PCT/SG2011/000251 patent/WO2012144952A1/en active Application Filing

Patent Citations (7)

Non-Patent Citations (1)

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