JPS60253616A - Jack-up type single leg drilling system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure and installation method of an offshore platform that can be used year-round in the Arctic or in less severe conditions, and particularly relates to a structure and installation method for an offshore platform that can be used throughout the year in the Arctic or in less severe conditions. A support pylon that is attached to the base and passes through a center hole of the deck unit that can be lifted relative to the mat base along the shirt king legs configured to engage with the base, and that supports the lifted deck unit. The floating gravity jack-up offshore platform structure is capable of retracting the shirt king leg into the deck unit after being connected to the deck unit.

Permanent Arctic ice floes, circum-Arctic open oceans, bays and inlets outside the region are expected to exist on these seafloors.

or pose extremely difficult problems for those wishing to explore and develop confirmed oil and gas wells. These waters are often extremely shallow, with areas ranging from 25 miles offshore to 1
The water is only 0.00 feet deep. Additionally, these waters are extremely remote from commercial and industrial centers. Usually from November to 5
It is covered by ice fields until the moon, and covered by floating ice from June to August.

Temperature changes are extreme.

Offshore drilling and production platforms that can be used at these depths have already been developed with milder natural conditions in mind. Judging from a combination of the above factors, existing platform structures are either completely unusable in the Arctic or can only be used for short periods of the year when the sea is ice-free. If an existing platform were to be used, it would either have to be transported from a remote location to the site, used, and transported away again between May and November, or there would be significant costs since there would be very little natural radicals. The platform must be stored during the ice season in a protected local port, which will be constructed over a period of time.

For these reasons, existing offshore platforms of known construction have not been used in the Arctic, and are unlikely to ever be used in the Arctic.

In view of the special challenges posed by the natural conditions of the Arctic, various new approaches to offshore operations have been proposed or implemented. The proposed approach involves using a suitable platform and rig structure in floating conditions during the Arctic ice-free season, and using the same structure on land for ice-free and de-icing operations, where the ice is strong enough to support the structure. The periods include the use of the same structure on an ice field (with or without allowing ice movement). That is,
This is the proposal disclosed in US Pat. No. 3,664,437. Some proposals have been made to adapt warm-water platforms to arctic conditions by incorporating ice cutters into the pylons of the vehicle landing structure or the jacking legs of the jack-up structure.

For example, U.S. Patent Nos. 3,669,052 and 3,693
, No. 360, No. 3,696,624 and No. 3,871
, No. 187 is the proposal. Furthermore, it has also been proposed to moor a strong floating bracket home in the form of a cone or bell, which is able to break up and resist incoming ice by buoyancy. It has also been proposed to use a strong, integrally fixed platform that forms a cone or hourglass shape near the water surface so that approaching ice can ride on top of the structure and break it. Such is US Pat. No. 3,972,199. Combinations and variations of the above-mentioned proposals are also known.

However, to date, none of the above-mentioned proposals has facilitated offshore operations in the Arctic.

The reasons are diverse. The proposal may not be suitable for the shallow waters in question, or the cost of manufacturing, installing and using the proposed structure may be a drawback. It may also be the case that the proposed structure is not sufficiently adaptable to a variety of use sites to warrant the necessary investment.

A new idea that has traditionally been adopted to enable long-term operations in the Arctic Ocean is artificial islands. Artificial islands are constructed in shallow waters from rocks and gravel as workshops capable of withstanding the extreme forces of polar nature, especially those of moving ice fields and floating ice. While this can be fruitful and economically possible in some situations, there are practical limits to the extent to which artificial islands can be used. That is, they are immovable and expensive to construct, and this cost increases rapidly as water depth increases. In many cases, rocks and gravel cannot be procured locally, and if a system is in place to provide a sufficient supply of these materials at any time, the cost of constructing an artificial island will be increased. The proposal to overcome these limitations of artificial islands by using man-made year-round ice islands has its own limitations and has not yet been adopted.

That is why a structure and usage system that can serve as a drilling work platform or production platform for oil and gas wells in the Arctic Ocean is highly desired. Such a platform must be flexible, ie, capable of being used in bodies of water of different depths, either as is or without substantial or costly modifications. It must also be an easily transportable platform so that it can be used in a variety of locations during its long service life. It must be adaptable to various seabed geological conditions so that preliminary work on the dredge and seabed pond bed is minimized. It must be usable all year round in the face of forces, especially those generated from ice, which tend to dislodge the platform from its place of use. It can be easily and economically manufactured in existing manufacturing facilities located far from the Arctic, it can be effectively, efficiently and safely transported to the Arctic Ocean, and it can be immediately installed without the need for costly specialized equipment or methods. There must be. The basic structure of the platform can be used by a variety of owners and operators with different preferences for the types and combinations of equipment used, and a wide variety of superstructures are available for use for a variety of purposes, including exploratory drilling, mining, and production from completed wells. It must be compatible with Furthermore, the construction and installation methods of the platform must be protective for the maritime life inherent in the Arctic Ocean and must comply with relevant environmental standards, which are particularly stringent in the Arctic Ocean.

For several years, the platform has been used in the waters of Tuck Inlet near Anchorage, Alaska, where ice floes are present. This platform interposes a smooth-faced tubular viron between a mat base and an elevated decking unit, and provides subsea operations from the decking unit through the vilon and the base. The Tuck Inlet platform does not encounter the thick ice fields and high waves experienced around the Beaufort Sea off the coasts of Alaska and Canada. In addition, the Tuck Cove platform does not use the jack-up method, but is a permanently installed production platform designed to be used in a specific location by assembling each part on-site. Tuck Cove's structure uses multiple permanent piles to secure the platform, rather than a monolithic structure.

Other jack-up or similar undercarriage offshore platform structures have been proposed.

For example, U.S. Patent Nos. 3,996,754 and 4,007
, 598 and 4,265,568. The single support legs or villons of these known constructions are open truss constructions and cannot be used in the presence of ice, especially since ice accumulates within the truss construction.

These known vehicle undercarriage platform structures do not meet the above needs.

The present invention approaches these needs in a manner that satisfies various practical, economic, and environmental considerations and, in particular, problems of the prior art.

The present invention safely, efficiently, effectively and economically accommodates operations in harsh conditions such as the Arctic Ocean and the many competing and often seemingly irreconcilable factors inherent in such installations. A novel structure and method sequence are provided.

In summary, from a structural perspective, the present invention resides in a gravity mobile offshore platform structure. The structure is buoyantly movable to and from a site of use on the seabed located at a given depth range. The platform structure consists of two main elements: a mat base and a liftable deck unit.

The base interlocks with the surface of the seabed formation and is supported by this formation. The pylon has a hollow cylindrical structure, with its lower end fixed at the center of the base and ending at its upper end, which maintains a distance from the base.

The decking unit has a hole in its center for inserting the pylon. In order to fix the decking unit to the pylon while maintaining a distance from the base, a fixing means is removably engaged between the decking unit and the vicinity of the upper end of the pylon. Deck/unit Deck/unit that maintains a distance from the center hole
Attach multiple jacking legs to the unit location. The jacking means cooperates between the shirt king leg and the jacking unit. The jacking means raises the decking unit relative to the base in response to the engagement of the lower end of the shirtking leg with the base, and also lifts the shirtking leg to a raised position on the decking unit side.

The pylon has a smooth surface between the base and a position near the top of the pylon, which makes the pylon's resistance to the movement of ice extremely small when the platform structure is used in ice fields or oceans obscured by floating ice.

The pylon is preferably hollow and has an open top end defining a passage through the pylon and the base, through which the required subsea operations can be carried out from a drilling rig mounted on a suitable working equipment, e.g. a decking unit. be able to.

If any part of the work equipment is movably attached to the deck unit when the deck unit is fixed to the upper end of the pylon, it can be moved from a location on the center hole side of the deck unit to a location on the pylon. good.

The base and deck unit can levitate and float,
It is preferable that ballast control can be performed using seawater.

The preferred method of installing the platform structure at the desired location is to attach the decking unit to the base, insert the pylon into the decking unit, and engage the lower ends of the shirt king legs attached to the decking unit with the base to complete the platform structure. Move it near the place of use. A platform structure is floated near the place of use and moved above the place of use in a floating state. The base is brought into a negative buoyancy state by ballast control, and the shirt king legs are lowered from the floating deck unit to lower the base until it is in an occlusal and fixed relationship with the seabed strata at the location of use. The deck unit is then lifted above the water along the shirtking legs until it reaches the top of the pylon, where it is secured to the pylon.

The shirtking leg is separated from the base, lifted from the base, and the lower end of the shirtking leg is positioned above the water surface at or near the decking unit.

If necessary, a reinforcing collar may be installed around the pylon at the waterline of the installed platform structure. Preferably, this collar is movable along the pylon and the installation can be fixed to the pylon at the waterline.

If a reinforced collar is used, the center hole of the decking unit should be made so that the pylon and collar can be inserted when the decking unit is attached to the base, for example when moving the platform structure from the assembly location to the vicinity of the use location. It is preferable to set the dimensions. In this case, by widening the cross-sectional area of the upper end of the pylon, the deck and
Preferably, the decking unit closely cooperates with the center hole as the unit is raised to the top of the pylon.

These and other features and advantages of the invention will be described in detail below with reference to preferred embodiments illustrated in the accompanying drawings.

It should be noted that some dimensions and other physical and design characteristics of the platform are illustrated for the purpose of providing complete information to those skilled in the art upon reading this specification, and are not intended to limit or constrain the invention. The platform of the present invention can be constructed in various sizes, in various arrangements and features, and can be constructed to accommodate environments of use other than those described herein. Although the invention is described for use in the Arctic Valley, it is clear that platforms embodying the invention can be used with great success in other regions of the world.

A gravity jack-up platform 10, particularly suitable for use in waters periodically covered by ice fields 11, is shown in perspective view in FIG. 1 of the accompanying drawings.

The main structural elements of the platform 10 are a large mat base 12, a central pylon 13 fixed at its lower end to the base and extending at right angles to the base, and a decking unit 14 that can be moved along the pylon and fixed to it above the base. , and four tubular jacking legs 15 mounted near the corners of the decking unit.

The base 12, which is also shown in plan view in FIG. 3 with some of its internal components shown in phantom, is a large fabricated steel structure. In the preferred embodiment of platform 10, the barge base is 25 feet high, 255 feet long, and 212 feet wide. It has a flattened bottom surface 16, a flattened top surface 17, and a vertical portion 18 extending approximately 10 feet above the bottom of the base and sloping inwardly at an angle of 35° relative to the horizontal to the top of the base at portion 19. It has a side wall. The internal structure of the base is defined by a plurality of partition walls 20, a web frame 21 and local reinforcements, these elements forming a plurality of watertight compartments within the base.

The base can be optionally ballasted with seawater between an unballasted floating condition (FIG. 8) and a ballasted condition in which the buoyancy of the base is substantially negative. The base is used for the ballast/venting system for seawater ballast, the seawater supply system, treated wastewater and bilge discharge systems, and for the release of the base from the seabed formations with which it engages when the platform is desired to be moved to another location. For this purpose, it contains four piping systems (not shown) consisting of a seawater injection system that injects water from nozzles on the bottom surface 16. The ballast system is operated by a submersible pump that passes through the pylon 13 and is lowered from the top of the pylon.

Base armor varies depending on base location.

The top armor is 1-'/2 inch thick around pylon 13, 1-'/4 inch thick at the base edge, and 1 inch elsewhere. The bottom armor is 2 inches around the base hole 23, 1 inch around the edges, and 12/4 inch everywhere else. The sidewall armor of the base is 1-"/4" to withstand locally applied ice loads. The parts of the platform 10 that are exposed to ambient (arctic) temperatures are constructed of cold-resistant steel; The submersible structure is formed of ordinary steel.

When the platform is used, the base is injected with a large amount of ballast to give it the properties necessary to keep it anchored to the seabed formation at the site of use. The ability of the base to remain stationary at the point of use when subjected to large lateral ice loads depends on the mass of the platform and the coefficient of friction between the base and the strata in contact with it. This coefficient of friction is maximized by attaching a Watsuful-like structure to the bottom of the base. The structure consists of 3" x -1/2" flat bar edges attached to the base bottom surface 16 in a 12" square repeating pattern. This provides a sufficient interface between the base and the ground surface.

Coating the sides and top of the base and the surfaces of the pylons with a low friction polyurethane coating minimizes the coefficient of friction between the ice and the base and prevents ice from adhering to the structure. This structural requirement, together with the slope of the base side walls, facilitates ice climbing onto the base and reduces the ice load acting on the base from the sides.

As shown in FIG. 3, the base 12 is open at a position 23 through which the pylon 13 passes, and the vertical passage formed by the pylon extends into the base.

Preferably, the pylon 13 is cylindrical. It is hollow and open at the top and bottom. In the preferred platform embodiment, the pylon is 30 feet in diameter and 90 feet in height.

The lower end of the pylon is secured around the opening 23 in the base 12. The pylon is perpendicular to the base. The pylon has a smooth closed exterior surface 24. Transient part top structure 25
is the 785.000,0 that works while using the platform
The pylon and base are structurally rigidly coupled to provide a pylon/base connection sufficient to withstand bending moments on the order of 1,000 foot-pounds. Pylons have extremely high structural strength. Its outer armor is 2 inches thick. Thirty-two flanged reinforcing elements, each two feet deep, extend vertically and evenly spaced circumferentially along the inner surface of the pylon armor. Flanged reinforcement rings, each five feet deep, are arranged inside the pylon armor at five foot intervals along the height of the pylon. The pylon therefore defines a 20 foot diameter free passage along its entire length, with the base hole 23 defining the in-base extension of this passage. Subsea operations are carried out from deck unit 14 via this passage when platform 10 is in use.

The pylon shell has sufficient local strength to withstand the 1200 psi concentrated load exerted by perennial water pressing against the pylon.

The pylon may be tapered if desired.

If it is known that the platform will be used in areas where ice movement occurs primarily or often in one direction along known lines, the pylon cross-section should be oval in shape, with its long axis Just align it with the water flow line.

Deck unit 14 is the main positively buoyant component of platform 10. The deck unit has a height of 26 feet from top surface 27 to bottom surface 28 and is square in shape with truncated or chamfered corners 29 in plan view.

The deck unit has a rectangular hole 30 in the center that passes through it in the vertical direction through which the pylon 13 is inserted. The hole 30 cooperates in a loose fit relationship with the outer circumference of the pylon 13, thus allowing the platform to move up and down along the pylon. The plan view of the deck unit, which is approximately square, is 170 feet between opposite major sides of the platform and 200 feet between opposite corner faces 29 of the platform.

As shown in FIG. 5, two pairs of primary structural bulkheads 32 and 33 extend along the diagonals of the deck between opposing corners, with bulkheads 32 perpendicular to bulkheads 33. These bulkheads, together with the top and bottom armor of the deck unit, form two extremely heavy orthogonal box-shaped girders that support the deck unit and protect the deck during use of the platform.
Supports variable excavation loads applied to the unit. These box-shaped girders have a decking unit with one jacking leg.
5 (sagging condition) or by pylon 13 (hogging condition).
Maintain the structural integrity of the unit. The main source of consumable liquid is housed in a box-shaped girder. A 5-foot deep double bottom 34 (FIG. 2) is fitted over the four triangular machinery spaces 35 (FIG. 5) formed by the intersection of the box-shaped girders. This configuration results in a total of 15,400 square feet of deck interior space. The triangular interior spaces of the deck are respectively equipped as a main power generation/distribution equipment room 35, an auxiliary machine room 36, a slurry pump room 37, and a slurry mixing/storage room 38. These rooms are 21 feet tall, making them suitable for installing intermediate or mezzanine decks if additional storage space is needed. A double bottom 34 extending below all machine spaces can be filled with seawater ballast to maintain the gravity load of the platform on the seabed formation at the desired level even as consumables on the deck unit are consumed. .

The spaces 40 between bulkheads 33 at the bulkhead ends between chambers 37 and 38 and the spaces 41 between bulkheads 32 at the bulkhead ends between chambers 36 and 37 define four 900 barrel capacity drilling slurry bits. An access path is provided from the slurry pump chamber 31 to the slurry bit area. The slurry mixing/storage chamber 38 is also accessible from the slurry pump 37 through a slurry pit space 40 . The main power generation room 35 and the auxiliary machine room 36 are connected to each other by a tunnel passage in a box-shaped girder that connects these two rooms 35,36.

The main or top deck of the deck unit 14 includes a three-story building 43 housing 80 people.

Other structures installed on the main deck of the deck unit include a tubular material storage shed for storing drill pipe and casing needed for subsea drilling operations carried out from the deck unit, and a drilling slurry processing house 45. and so on. As shown in the plan view in FIG. 4, three structures 43.
44 and 45 are placed. Helicopter deck 46 is linked with residential buildings.

In particular, as is clear from FIG. 1, the derrick base structure 49
An excavation derrick 47 is attached to an excavation floor 48 supported above. Derrick base structure is deck unit hole 3
It is movably attached to the main deck of the deck unit via a pair of rails 50 that are substantially aligned with the box-shaped girder bulkhead 32 near the fourth side of the deck. With this configuration, the derrick 47 can be moved between the excavation position above the hole 30 and the retracted position in which the derrick base has moved sufficiently to allow the derrick base to protrude laterally from the hole 30 and the pylon 13 to protrude upwardly from the derrick unit. Supported by deck units so that they can move. Hydraulics similar to those used on modern cantilever jack-up drilling platforms and exploration platforms are used to move the derrick base along the rails 50. The base is configured so that storage, handling, and maintenance of the drilling BOP assembly and drilling slurry diverter occurs in an area below the derrick floor 48 that is protected from the environment.

As shown in FIGS. 1 and 2, the main deck of the deck unit 14 is equipped with two remote-controlled 50-ton rotary cranes 51 with pedestals. These cranes are arranged in such a way that the jacking legs 15 do not interfere with crane operation when in a raised position relative to the deck unit.

Pipe storage 44 occupies 2900 square feet of deck space. The storage is a fully enclosed hangar structure with an overhead pipe handling frame and hydraulic pipe handling positions. Install a 40-foot long roll-up door at one end of the storage area near the open pipe storage and crane installation area.

The shirt king leg 15 is of tubular construction and is equipped with two-sided racks 53 at diametrically opposed positions along its length. Each shirtking leg is driven up and down relative to the decking unit by a pair of six-binion jacking mechanisms 52 in which three jacking pinions are mounted on adjacent jacking legs of a two-sided rack. cooperating with each of the two rows of rack teeth in each. Unlike the case with truss-shaped legs, tubular jacking legs 1
5 requires relatively little deck space at the edge of the deck unit. The main deck usable area of the deck unit, excluding the shirt king leg zone and residential zone, is 18,500 square feet.

A male component 54 of the jacking leg structure is attached to the lower end of each jacking leg, and a female component 55 of the launch structure is provided on the base 12 so as to be located in a straight line with each jacking leg. I'm here. The position of the several female components of the shirt king leg latch mechanism on the base is shown in FIG. By remotely controlling this latch mechanism, the male and female components can be positively engaged with each other. As will be described in detail later, after positioning the platform above the seabed stratum that engages with the base, the shirt king leg can be attached to the decking unit. The base/pylon assembly can be lowered from the floating deck unit by optionally lowering the base/pylon assembly from the floating deck unit.

The operating position of the deck unit is near the top of the pylon 13. That is, the upper end of the pylon is located approximately at the same height or slightly below the upper deck of the deck unit. The deck unit is secured to the upper end of the pylon by retractable support bins 57, which are elements of a twenty-four support bin assembly 58, one of which is shown in FIG. The support bin 57 is mounted in a housing 59 which is fixed to the deck unit and opens into a central hole 30 passing through a corresponding one of the eight walls defining the circumference of the rectangular hole. The bottle 57 is driven between a fully retracted position within the housing 59 and an extended position in which the bottle protrudes from the housing (FIG. 15). The hydraulic drive mechanism 60 drives the bin in this way.
It is. The cross-sectional area of each bin 57 is approximately 12 inches square and cooperates with a recess 61 defined by a cast socket 62 in the extended state. The cast socket 62 has a recess 6
1 is fixed to the pylon 13 so as to open to the outside of the pylon. The support bin assemblies 58 are arranged in three tiers of eight pieces around the deck unit hole 30.

Similarly, the cast sockets are arranged in three stages of eight sockets each as shown in FIG.

The lower surface of each bottle-fitting recess 61 is defined by a soft bronze shim 63. This shim allows each bin to cooperate with its corresponding socket in the same manner that all other bins cooperate with their respective sockets, so that the load on the decking unit is reduced to the extent that all 24 bin/socket pairs Evenly distributed across the assembly.

The position of the decking unit 14 relative to the pylon 13 cannot be adjusted along the height of the pylon. Rather, in view of the geometry of the support bin assemblies described above, the decking unit has a predetermined operating position at the upper end of the pylon. The decking unit is movable between a transport position in which the decking unit is placed on the base 12 and an operating position at the top of the pylon.

As mentioned above, pylon 13 is hollow, providing a 2° diameter free passage through the pylon and base 12 from the open top. This passageway is similar to a moonpool on a drilling ship and provides a passageway from the platform 10 into the underlying geology to carry out subsea operations, such as exploration or production drilling operations, when the platform is in use.

FIG. 6 shows a preferred example of the manufacturing process of the platform 1o. Platform 1, focusing on the size of the main ingredients
0 is preferably assembled in a location remote from the Arctic Ocean where it is suitable for use. The base 12 and deck unit 14, both buoyant and ballasted, are manufactured separately at a suitable location, such as a shipyard. The base is manufactured to define the pylon stamp 65, and the remainder of the pylon is manufactured as a subassembly 66.

manufacturing the base and equipping it with the required permanent ballast;
Then, after manufacturing the deck unit, but before equipping the deck unit with a superstructure such as a deck house, the base is floated at a suitable depth in a safe body of water, such as a cove. At this point, the base is arbitrarily ballast controlled to create a negative buoyancy state, and the base is sunk to the bottom of the cove. Next, the positively floating deck unit is floated above the sunken base, the pylon stamp 65 and the deck unit hole 30 are in a substantially coaxial relationship, and the female latch component is configured such that the jacking leg 15 extends over the top of the base. Position it so that it lines up with 55. Lower the shirt king legs so that the male and female latch components s4.55 interlock with each other.

Next, remove the ballast from the base to create positive buoyancy. Next, the deck unit is lowered along the jacking legs 15 to the lower limit position corresponding to the top surface of the floating base or slightly above it.

The bay and deck unit is then returned to the manufacturing site where the pylon subassembly 66 is lowered into engagement with the upper end of the pylon stud 65 and secured thereto. The deck house and superstructure of the deck unit will be installed, and the final exterior of the platform will be completed. Suitable fixtures such as tubular materials and other equipment used in offshore drilling operations may be loaded onto the deck unit at sea as part of the sheathing operations. Once the manufacturer and owner tests are completed and the owner receives the platform from the manufacturer's factory, the platform can be moved to the Arctic Ocean immediately.

A preferred method of transporting platform 10 to a site of use and installing it at the site is illustrated in step-by-step fashion in FIGS. 7-11. As a preparatory step for moving the platform to the site, the platform is loaded onto a submersible barge 68, connected to an ocean tugboat 69 during a short period when there is no ice on the intended route, and towed along with the cargo to the Arctic Ocean. (Submersible barges 68 are used for long towing trips. For short towing distances, e.g. between locations in the same body of water, the platform can be towed while floating above the deck unit or base. Near the intended site of use (Figure 8), the submersible barge is ballast-controlled and lowered away from the platform, leaving the platform floating freely on the base). To tow the platform to its intended use at sea level, a tugboat 69 is attached to the floating platform. At the site of use, the base 12 is ballast-controlled to a slightly negative buoyancy state as shown in FIG. At this time, the negative buoyancy of the base is smaller than the positive buoyancy provided by the deck-type unit 14. Therefore, the entire platform becomes buoyant due to its weight and floats above the deck unit. The base is then appropriately lowered from the deck unit by operating the jacking mechanism 52 to lower the jacking legs 15 that are engaged with the base. The base is lowered until it engages the seabed bed 70. The base is then fully ballasted and tightly interlocked with the formation 71 immediately below the ocean floor bed 70.

Operation of the jacking mechanism 52 continues without disengaging the jacking legs from the base, thereby raising the deck unit along the pylon 13 until all of the deck unit support bins 57 engage the pylon recesses 61. The decking unit is attached to the pylon 13 by operating the drive mechanisms of the several sets of support bin assemblies to firmly engage the several sets of support bin assemblies with the recesses 61.
fixed in the working position at the upper end of the By moving the derrick base structure 49 along the rail 50, the derrick base is positioned above the top of the pylon, where the first
Fix the base as shown in Figure 0. In this way, the derrick base and all structures attached to it are connected to the pylon 13.
When moved to a position above the deck unit, the center of gravity of the deck unit is approximately aligned with the pylon axis. That is, the eccentric load on the decking unit is significantly reduced, although not completely eliminated. The shirtking leg is then disengaged from the base 12 and raised to the retracted position shown in FIG. 11 in which the lower end of the shirtking leg is substantially or completely contained within the decking unit. At this point, the platform is ready for use as a mobile-leg gravity mat jack-up offshore drilling platform, and all that remains is to transport materials and personnel to the platform from a suitable supply vessel or helicopter.

The weight and capacity of the preferred embodiment of the platform 10 described above is as follows.

106 lbs 106 lbs Decking Unit: Weight of Steel 8.35 Fitting 5.65 Variable Load Total Lifting Load 27.6 27.6 Base and Pylon Steel Loads 16.1 Permanent Ballast (Wet) 12.4 Total Steel and Ballast 28.5 28.5 total 56
．． 1 (28,05OS, T, ) As is clear from the data in the table above, platform 1
0 has sufficient submerged weight between its own mass and the mass added by ballast, storage materials, and other supplies to cover the 54,000 square feet of seabed floor that intersects with the landing base. As a result, a large lateral load due to ice is applied to the pylon and base, causing damage to the pylon, deck unit, and its upper part. =
1-S↓Fl\Kenkyo-JJ
(within the formation load limit).

Depending on the extent of post-manufacturing loading and rigging that occurs in the empty space of the platform, the platform can be as low as 15 feet. That is, if the water depth is 15 feet, the platform can be towed to the site of use. This depth of 15 feet is the platform's minimum operating depth.

In the case of the preferred embodiment described above, this minimum operating depth is 35
ft. or more. Therefore, if you wish to use this platform in a nominal 15-foot water depth location, you must prepare the site for use by digging a 350-foot diameter hole deep enough to place the top of the base 10 feet below water before installing the platform. Must be. That is, the distance from the bottom of this borehole to the sea surface is 35 feet. The base top surface 17 is located at least 10 feet below sea level so that the ice fields expected in the Arctic Ocean at such depths will have a distance of 3 to 4 feet from the base.

Mei er. The platform 10 is positioned so that its bottom surface is 3 to 4 feet above the top surface of the base on which it is installed.

If the platform base height is 25 feet and the pylon height is 90 feet, the platform can be used in water depths of 15 to 90 feet with at least 30 feet of separation between the sea level and the bottom of the decking unit 14. is obtained. By increasing the height of the pylon, platform 10 can be used at greater depths.

Those familiar with drilling operations in the Beaufort Sea off the coasts of northern Alaska and northwestern Canada will be aware that these depths correspond to the marginal waters of the Arctic Ocean beyond the southern limits of the Polar Ice pack. During the freezing season, most of the sea surface in this area is covered by annual ice, that is, ice fields that are made up of ice that has been formed over a period of one year. The ice this past year has been 6 to 7 feet thick. However, in this area, floating ice of multi-year ice drifting from polar ice floes can also be seen. Additionally, pressure ridges occur in this area due to the movement of annual ice due to a variety of influences, including wind and tidal action. This pressure bulge extends to a height of about 25 feet above the normal thickness of annual ice and extends to considerable depths beneath the ice field. Multi-year ice and pressure ridges have much greater ice strength than single-year ice fields. However, the mass and strength of platform 10 are limited by the ice field of one-year ice, the ice pack of multi-year ice, and the pressure ridges of pylon 13 and base 12.
It can withstand the load sufficiently even if it is interlocked.

Platform 10 is designed to take advantage of the loads applied by pressure ridges. That is, the platform is shaped so that a pressure ridge approaching the pylon 13 rides up on the base 12 so that a portion of the weight of the pressure ridge is supported by the base. the result,
Since the effective load of the base on the formation 71 increases and therefore the effective load of the platform on the formation increases,
The ability of the platform to hold its position in the face of ice loads is further enhanced. As will be obvious to those skilled in the art, in extreme cases conventional waterproofing methods may be employed to keep the lateral loads imposed on the platform by ice within permissible limits.

The use of a cooperative jacking mechanism between deck unit 14 and pylon 13 is particularly avoided in platform 10. If the jacking legs 15 and jacking mechanism 52 are used to raise and lower the decking unit along the pylon with respect to the base 12, the pylon can be defined by a smooth outer surface.

The situation is different when mating a pylon with a protruding or recessed shirt king rack. The presence of Shirtking Rack structure projections or indentations on the bylon surface act as ice catchers, significantly increasing the forces exerted on the pylon by ice attempting to pass through the pylon; Significantly increases lateral loads and moments on the pylon and pylon-to-base connection. Detach the pylon
When utilized as part of the unit's jacking mechanism, its diameter must be significantly increased to withstand increased water loads. However, if the diameter of the pylon is large, the pylon will appear like a wall to the adjacent ice. However, the pylon 13 has a relatively small diameter and therefore has a very small surface area to the approaching ice field. Because of their small diameter, the pylons act as teeth on approaching ice, breaking it up and making it easier for it to pass around the pylon.

Another advantage of the shirt king legs 15 is that the machinery necessary to raise and lower the jacking legs 15 relative to the decking unit is located in a space directly below the rig floor that is allocated for the intended operation from the platform. Don't concentrate and get bored
It can be easily stored if placed near the corner of the unit. Furthermore, if the jacking legs 15 are provided closer to the side, it becomes easier to maintain the level of the platform that moves up and down along the pylon.

Furthermore, by avoiding utilizing the pylon 13 as part of the jacking mechanism of the decking unit, the pylon can be manufactured using conventional manufacturing methods, thus resulting in increased platform economy. Another advantage of having the shirt king leg closer to the side is that it helps absorb eccentric loads acting on the deck unit as it moves up and down along the pylon. That is, the platform may be manufactured and rigged according to the intended application, rather than taking into account the constraints imposed by eccentric load considerations during shirtking operations.

In some sea areas near the North Pole, the local ice load acting on the pylon of the vehicle-pedal jack-up platform of the present invention may exceed the local strength of the pylon if the pylon is configured as described above. obtain. One advantage of the platform according to the invention is that a predetermined water depth range;
It can be used repeatedly at different depths depending on the location, for example within a range of 15 to 90 feet. If the pylon were manufactured to have increased local strength over at least a large portion of its height for this depth range, the pylon would be too heavy for any use situation. 1st
Figures 2.13 and 14 illustrate the construction of another platform 80 and its installation method according to the invention to meet this situation and the problems posed thereby.

Platform 80 differs from platform 10 primarily in three ways. 1) The upper end of the pylon 13 has an enlarged diameter head 81 within which the deck unit support bin recess 61 is defined. 2) Deck unit 1
4 has an enlarged central hole 82, which preferably has a helical shape, and is similar to the deck unit hole 3 of the platform 10.
0 cooperates with the top of the pylon in the same manner as
It is dimensioned to cooperate with head 81. 3)
A movable anti-icing collar 83 is installed around the pylon 13 so that it can be moved along the pylon between the base 12 and the pylon base 81 and fixed to the pylon at any position within the movement range.
This is provided.

The outside diameter of collar 83 is smaller than the free effective diameter of deck unit hole 82. The collar 83 has a smooth cylindrical outer surface. The collar 83 is virtually located on the platform 8 at its intended use location.
This is a movable pylon reinforcing belt that can be raised from the base 12 together with the deck unit 14 as the deck unit is lifted relative to the base during the installation process. Please refer to FIG. The outside diameter of the collar is less than or equal to the diameter of the pylon head 81.

The platform installation described above is similar to the method described above.
is fixed to the deck unit 14, and as the base in a negative buoyancy state descends from the deck unit in a positive buoyancy state to the seabed floor at the location of use, the collar 83 moves together with the deck unit onto the pylon. Allow it to rise along the way. When the base engages with the seabed stratum 70, the deck and
The unit will be installed in a position on the pylon corresponding to the platform water line in the state. Before raising the deck unit further along the pylon, the deck unit may be raised further along the pylon, for example by utilizing a cooperating bin/socket mechanism between the collar and the pylon, similar to the deck unit bin/socket support assembly shown in FIG. 83 to the pylon appropriately. In this case, even if there is a small dent on the outer surface of the pylon over a part of the height of the pylon, the socket, which could prevent ice from passing through the pylon, is located near the platform waterline, and the reinforced collar provided on the pylon This is not a problem because it is obscured by After the collar 83 is connected to the pylon, the collar and deck unit 14 are uncoupled. The decking unit is then raised along jacking legs 15 to engage the decking unit hole 82 with the pylon head 81 while simultaneously moving the decking unit support bin 57 into a cooperating recess defined within the pylon head. 61 and interlock. In this manner, the deck unit is secured to the pylon of platform 80 in much the same manner as the deck unit is secured to the upper end of the pylon of platform 10.

If the anti-icing rack 83 is adopted for the platform 80, the pylon 13 can be designed with the bending and shear loads that must be withstood as the main consideration, without considering local ice loads.

The platform of the present invention has several important features and advantages. Since the platform is configured as a jack-up type, it can be used over a wide range of water depths. It is structurally simple because it uses gravity loads to maintain its position. The chassis (single support leg) structure provides a platform that is as passive as possible. Because the platform is mobile and reusable, and all necessary operating systems are incorporated into the structure, the cost per oil or gas well is reduced over the long service life of the platform. Since the landing area is wide, it can be used even in soft strata. The vehicle leg structure is also advantageous in that it minimizes the ice force acting on the platform and allows a portion of the ice force to be used to increase position fixing ability. The platform's large storage capacity reduces the dependence of the platform and its personnel on supply vessels. The platform utilizes only seawater ballast to supplement the permanent ballast within the base. Platforms are inherently lightweight in their unballasted state and therefore have a very shallow waterline when used in shallow water.

The invention has been described with reference to specific dimensions, weights, and relationships of preferred embodiments of the invention. This description is presented by way of example of the principles, features, and relationships characterizing the invention, and is not intended to limit the structure and method sequence in which the invention may be practiced. As will be readily understood by those skilled in the art, various changes and improvements can be made to the above structures and methods without departing from the scope of the present invention. Accordingly, the above description should be read as supplementary to the claims.

[Brief explanation of drawings]

1 is a perspective view of an offshore platform equipped as a drilling platform according to a preferred embodiment of the present invention; FIG. 2 is an elevational view of the platform of FIG. 1; and FIG.
Figure 4 is a plan view of the decking unit of the platform in Figure 1, and Figure 5 shows the internal structure and main compartments of the decking unit. Figure 6 is an elevational view showing the preferred configuration of the platform of Figure 1; Figure 7 shows the preferred initial stage of installing the platform at the site of use - when it is connected to a barge. FIG. 8 is an elevational view showing the platform of FIG. Figure 10 is an elevation view showing another stage of the platform installation process, Figure 11 is an elevation view showing another stage of the platform installation process, and Figure 12 is an elevation view of the platform installation at an early stage in the installation process. 13 is an elevation view of the platform of FIG. 12 during installation at another stage in the process; FIG. 14 is an elevation view of the platform of FIG. 12 at another stage in the installation process; FIG. The elevational view, FIG. 15, is a partial cross-sectional view of one of several identical mechanisms used in the platforms of FIGS. 1 and 12 to secure the deck unit to the top of the pylon. 10...Platform 11...Ice field 12...
・Mat base 13...Central pylon 14...
・Deck unit 15...Jacking leg 23
...Base hole 50...Rail 58...Support bin assembly 65...Pylon tap 66
...Subassembly 68...Barge 69..., Tugboat 10...Seafloor floor 80...Engraving of platform drawing (no changes in content 1-) Procedural amendment (26 "Masturbation") July 1982 July 27th, Manabu Shiga, Commissioner of the Japan Patent Office, 1, Indication of the case, Patent Application No. 109301, filed in 1982, 2
, Title of invention Jack-up type vehicle leg excavation system 3,
Relationship with the person making the amendment Patent applicant address 811 West Seventh Street, Los Angeles, California, 90017, United States of America Name Global Marine Incorporated Representative John Gee, Ryan 4, Agent 2-14 Shimoai, Shinjuku-ku, Tokyo No. 1 No. 5, Date of amendment order Voluntary amendment 6, Subject of amendment Column of inventor and patent applicant in application, power of attorney, specification, drawing 7, Contents of amendment As attached, Me, power of attorney and the same translation,
We will supplement the engraving of the specification (no change in content) and the engraving of drawings 5 (no change in content).

Claims (4)

[Claims] (1) A mat base that engages with the i-plane of the seabed stratum and is supported by the seabed stratum, a closed-face viron whose lower end is fixed at the center of the base and extends to an upper end at a distance from the base, and a mat base for inserting the viron. a liftable deck unit having a center hole; and a detachably engaged part between the deck unit and a portion near the upper end of the byron for fixing the deck unit to the byron while maintaining a distance from the base. A plurality of shirt king legs are attached to the deck unit at intervals from the center hole, and the deck unit is attached to the base along Byron in response to the lower end of the shirt king legs engaging with the base. and jacking means for lifting the shirt king legs to the raised position of the decking unit. (2) The platform of claim 1, wherein the villons are hollow and define a portion of the open end passage through the villons and the base. (3) A patent claim characterized in that the deck unit includes a derrick that is movable between a first position above the center hole of the deck unit and a second position laterally offset from the center hole. Scope No. (Platforms described in Section Z. (4) The deck unit has a rectangular plan shape,
The platform according to claim 1, wherein the jacking legs are arranged near the corners of the deck unit. ■ Claim (4) characterized in that the deck unit is configured to define a substantially box-shaped girder structure connecting two corners of the deck unit that face each other in a diagonal direction. Platforms listed. (■ Claim No. 1 characterized in that the base can be arbitrarily ballast-controlled with seawater between a substantially positive buoyancy state sufficient to levitate the platform and a substantially negative buoyancy state) Platforms listed in section ). ω °The deck unit is at the gate of a positive buoyancy state where the base is in a slightly negative buoyancy state and the deck unit has enough buoyancy to stand on its own, and a ballasted state when the deck unit is fixed to Byron. The platform according to claim 0, characterized in that the ballast can be controlled arbitrarily. ■ The base has a top surface, a bottom surface, and a side surface between the top surface and the bottom surface, and the side surface is inclined inward toward the top surface. Platforms listed in section ). (2) The platform according to claim 0, characterized in that a low-friction coating is applied to the Byron, the top surface of the base, and the inclined surface of the base. Cω Cooperatively operable latch means between the lower end of the jacking leg and the base to fixedly but relatably connect the leg end to the base. ) The plant home described in section ). The platform according to claim 1, wherein the shirt king leg can be forcibly moved up and down with respect to the decking unit by operating the jacking means. (I21) The platform according to claim (1), characterized in that the shirt king legs are tubular. (b) The platform according to claim (1), characterized in that the byron is cylindrical. ■ Byron an upper head portion having a horizontal dimension larger than the lower portion and configured to mate with the deck unit center hole; and an upper head portion movable between the head portion and the base along at least a predetermined portion of the villon. , Detsuki・
an annular collar of any height formed and dimensioned to fit into the unit center hole; means cooperating between the byron and the collar to secure the collar to said predetermined portion of the byron; 2. A platform according to claim 1, further comprising means for moving the collar along the platform. (to) A platform according to claim 1, characterized in that the means for moving the collar along the byrons includes means for cooperating between the collar and the decking unit. 071. A platform according to claim 2, wherein the means for securing the collar to the virons include retractable bin means. Phase: Platform according to claim 1, characterized in that the securing means comprises retractable bin means. 0va) a buoyant base that can be ballasted to a substantially negative buoyancy state; b) a viron whose lower end is fixed to the center of the base and extends upwardly from the base; and C) a buoyant base that is located above the base and that is movable. d) a buoyant, ballasted deck unit having a central hole for insertion into the deck; A method for installing an offshore drilling platform having a structure consisting of a plurality of vertical shirtking legs driveable from the base comprises: 1) raising the platform attached to the base by at least an amount above the height of the base and Byron; 2) Connect the lower ends of the Shirtking legs to the base and lock the Shirtking legs to the deck unit; 3) Ballast control the base to a slightly negative buoyancy state and use the deck unit.
levitating the platform on the unit; 4) lowering the base from the decking unit via the shirtking legs to engage the base with the formation below the decking unit; and 5) lowering the decking along the byron via the jacking legs. Lift the unit above the water surface so that the center hole of the deck unit engages with the upper end of the pylon, 6) fix the deck unit to the upper end of the pylon, 7) remove the shirt king leg from the base, and 8) remove the jacking leg. An installation method characterized by raising the deck unit to the retracted position. - Minerals such as crude or refined hydrocarbons produced from seabed deposits by utilizing the platform structure described in claim 0. (2. Minerals such as hydrocarbons in a crude or refined state produced from a seabed deposit by using a platform installed above the seabed deposit according to the method set forth in claim 1.