This invention relates to modified vessels capable of transporting a segmented wind-turbine to an offshore location, and methods of transporting, storing, and erecting the offshore wind turbine.
Wind-turbine generated electricity is an alternative to oil and gas energy sources. For a number of reasons, including maintenance efficiency, permitting, and general organization, it is often desirable to erect a plurality of wind turbines within close proximity to one another. Such a group is called a wind farm, and is preferably strategically located in an area that receives sustained-high winds.
Wind farms may be located on land or offshore. Because wind turbines are massive—having columns over 70 meters tall, and blades over 40 meters long—transportation of wind turbines to offshore wind farms, often included shipping the wind turbines by derrick barge in several segments. Due to the limited storage capacity of the derrick barges, multiple sailings are generally necessary to complete erection of a wind farm.
Derrick barges are typically fitted with one or more cranes. Such cranes may be mounted atop fixed and solid pedestals. Derrick barges are typically pulled or towed to location. Typically, derrick barges do not jack-up. Accordingly, derrick barges are subject to the pitch and roll of the sea/ocean. Thus, the derrick barge's ability to erect an offshore wind turbine is limited. Moreover, the available deck space of the derrick barge is limited.
Another type of vessel includes a jack-up drilling rig. Jack-up drilling rigs are typically employed for offshore energy exploration and development of offshore oil and gas fields. These drilling rigs generally float on a hull and have three or four extendable legs. In the typical situation, the drilling rig is pulled or towed to a location by one or more tug vessels. At the desired location, the drilling rig's legs are then extended to the ocean/sea floor, and the deck of the drilling rig is raised—or jacked up—out of the water. Preferably, the deck of the drilling rig is raised high enough to avoid any sea swells. The jacked-up deck of the drilling rig may provide a stable structure in an environment from which a crew may perform drilling operations. These drilling rigs can withstand harsh weather conditions and may be deployed for long periods of time. Due to the nature of the work, deck space is limited and valuable.
Yet another type of vessel used to facilitate offshore operations is a lift boat. Lift boats, like jack-up rigs, typically have three or four jack-up legs and may be elevated out of the water. Lift boats are considerably smaller than jack-up rigs, and are intended for short term deployment. These smaller vessels generally cannot withstand harsh weather conditions and are typically designed to move, under their own power and without the need for a tug boat, out of the way of bad weather. Accordingly, a lift boat is limited in its size and ability, and cannot function as a jack-up rig.
Additional features of the three above-identified vessels are illustrated in the following patents:
U.S. Pat. No. 4,483,644 to Johnson describes a cantilever mobile marine rig with hydraulic load equalizers. The rig includes a deck structure and a cantilever assembly skiddingly mounted on the deck structure. The hydraulic load equalizers distribute the stresses between the cantilever assembly and the structure.
U.S. Pat. No. 5,388,930 to McNease describes a method and apparatus for transporting and using a drilling apparatus or a construction crane apparatus from a single moveable vessel. In the McNease disclosure, a drilling apparatus of a construction crane apparatus is skidded onto the deck of a jack-up rig which is then floated to a remote location for use.
U.S. Pat. No. 6,257,165 to Dams, Jr. et al. describes a vessel with a movable deck. The vessel comprises a first and second pontoon, a first catamaran hull attached thereto, and a platform. The pontoons and catamaran hull float on the waters' surface, and cannot be raised. The platform is connected to the catamaran hull using jack-up legs. In this manner, the platform may be raised and lowered relative to the catamaran hull using a jacking mechanism. Dams, Jr. et al. further describes a first thruster nozzle attached to the first pontoon, the first thruster nozzle is attached in a 360 degree phase and a second thruster nozzle attached to the second pontoon, with the second thruster nozzle being movable in a 360 degree phase.
U.S. Pat. No. 6,200,069 to Miller describes a jack-up work platform. The work platform of Miller comprises a hovercraft vessel outfitted with several jack up legs. Miller states that the hovercraft can traverse environmentally sensitive terrain such as brackish and freshwater marshes without the need to dig canals that may cause or exacerbate salt water instruction. Once the drilling or exploration site is reached, the jack up legs may be lowered, lifting the work platform above the surface.
U.S. Pat. No. 6,607,331 to Sanders et al. describes a support structure for a lift crane, and in particular, to a lift crane jack-up structure, wherein the lift crane is positioned about a leg of the jack-up structure without relying upon the leg for structural support. The structure includes an above deck portion and a substructure situated below deck such that the jack-house is structurally integrated into the vessel.
U.S. Pat. No. 6,926,097 to Blake describes an offshore jack-up workover rig, which is detachably mounted on an extensible cantilevered frame. The cantilevered frame comprises a pair of parallel support beams mounted to the vessel. A pair of cantilever skid beams rests on the support beam. And, at least one hydraulic ram and cylinder is provided to drive the cantilever skid beam over the support beam.
U.S. Pat. No. 7,131,388 to Moise, II et al. describes a lift boat having recesses in the hull that receive the pads of the legs when the boat is underway. Moise, II et al. states that preferably, the total bottom surface area of the pads is preferably at least 30% of the surface area of the deck of the lift boat. Moreover, Moise describes that the total bottom surface area of the pad is large enough such that, when the boat is loaded and jacked up, the pads exert less than 7 psi on the sea floor. Moise further describes propelling the boat using two rear propellers and rudders.
A vessel preferably has the capability of storing, transporting, and installing between one and ten wind turbines. Such a vessel may include a hull having a hull periphery, wherein the hull periphery has a bow, a center section, a transom, an extended transom, a bow sloped section between the bow and the center section, and a transom sloped section between the transom and the center section, and the transom is wider, along the vertical axis, than the bow, and the bow and transom are at least half as deep as the center section. The vessel may further include at least two rear jack-up legs, and at least one forward jack-up leg, movably attached to the hull, as well as a jacking mechanism connected to each of the jack-up legs for elevating and lowering each jack up leg relative to the hull between elevated and lowered positions. The vessel may also include at least two rear azimuthing thrusters affixed to a lower side of the transom; and at least one front azimuthing thruster affixed to a lower side of the bow. The vessel optionally includes a crane support having at least two vertical members with each vertical member having a first and second end, the first end of the first vertical member is affixed to a first track, the first end of the second vertical member is affixed to a second track, the first and second tracks are affixed to a deck of the vessel, the second end of the first vertical member is affixed to a first side of a platform, the second end of the second vertical member is affixed to a second side of the platform; and a column having a proximate and distal end, the proximate end is affixed to the platform, and the crane is rotatably affixed to the distal end of the column, the platform has a lower side disposed at least about 2 meters above the deck, the crane support apparatus is movable along the track. The vessel also may include at least four, preferably at least six, wind-turbine-column foundations, and at least two wind-turbine-blade brackets individually mounted to the side of the transport vessel.
A method of transporting a wind turbine via a transport vessel may include separately securing at least one wind-turbine column to a wind-turbine foundation, and at least one wind-turbine nacelle to the deck of the transport vessel. The method may further include securing at least one wind-turbine blade to at least two wind-turbine-blade brackets, wherein each wind-turbine-blade brackets is individually mounted to the side of the transport vessel. Preferably, between four and six wind turbines may be transported in a single sailing.
Another method of erecting a wind turbine offshore may include lifting a wind-turbine column from a wind-turbine foundation affixed to the deck of a vessel using a crane disposed on the vessel, wherein the crane includes a crane support having at least two vertical members with each vertical member having a first and second end, the first end of the first vertical member is affixed to a first track, the first end of the second vertical member is affixed to a second track, the first and second tracks are affixed to a deck of the vessel, the second end of the first vertical member is affixed to a first side of a platform, the second end of the second vertical member is affixed to a second side of the platform; and a column having a proximate and distal end, the proximate end is affixed to the platform, and the crane is rotatably affixed to the distal end of the column, the platform has a lower side disposed at least about 2 meters above the deck, the crane support apparatus is movable along the track. The crane may be used to secure the wind-turbine column to an offshore wind-turbine base. The crane may be used to lift a nacelle from the deck of the vessel and secure it to the wind-turbine column. The crane may be used to lift at least one blade from the vessel and secure it to the wind-turbine nacelle.
While the invention will be described in connection with the preferred illustrative embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
For a further understanding of the nature and objects of the present inventions, reference should be made to the following detailed disclosure, taken in conjunction with the accompanying drawing, in which like parts are given like reference numerals. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness, wherein:
In an embodiment, the terms “horizontal axis” or “horizontal” mean a direction along the length of a vessel from the transom of the vessel to the bow of the vessel.
In an embodiment, the terms “vertical axis” or “vertical” mean a direction along the width of a vessel from the port of the vessel to the starboard of the vessel.
In an embodiment, the terms “depth axis”, “depth”, or “deep” mean a direction along the depth of a vessel from the bottom of the vessel to the top of the vessel.
In an embodiment, the term “still water line” means the level of the water without wind or other disturbances which artificially impacts the level of the water, such as the wake from another vessel.
In an embodiment, the term “air gap” means the distance from the lowest portion of the hull of a vessel to the still water line.
In an embodiment, the term “self propelled” or “self propelled vessel” means a vessel that is capable of navigating open waters without the assistance of any other vessel, such as a tug boat.
In an embodiment, the term “hold station” or the term “holding a vessel in station” means that the vessel has the ability to remain within a 3 meter radius of its position during flotation.
In an embodiment, the term “Elevating Support Vessel” is defined as any vessel having at least a hull and deck, at least three jack-up legs capable of extending through the hull and deck, and at least three azimuthing thrusters, wherein the vessel is self propelled.
In an embodiment, the term “light ship” means the weight of the ship including its fixed components such as cranes, engines, and the like apparatus permanently affixed to the vessel.
In an embodiment, the term “full displacement” means the light ship weight plus the weight of variable loads and consumables such as fuel, water, deck cargo, personnel and the like objects.
In an embodiment, wherein a measurement of distance, length, or thickness is discussed the mean distance, length, or thickness is implied, unless otherwise indicated or unless would be otherwise understood by one of ordinary skill in the art. For example, wherein thickness of a section is discussed the mean thickness across the section is implied.
In an embodiment, all measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise.
The hull 103 of the Elevating Support Vessel 100 may be thought of as subdivided into six sections: a transom section 142, a sloped transom section 145, a center section 147, a sloped bow section 150, a bow section 153, and an extended transom section 230. In an embodiment, the transom section 142 and the extended transom section 230 may be thought of as a single section.
Preferably, at least a portion of the lower side of the transom section 142 is flat. Likewise, preferably at least a portion of the lower side of the bow section 153 is flat. In this manner, thrusters 124, 127, and 130 may be mounted, respectively, to the flat lower sides of the transom section 142 and bow section 153. The transom section 142 and the bow section 153 are of a relatively thinner depth than the center section 147. In one embodiment of the Elevating Support Vessel 100, the transom section 142 and the bow section 153 are at least half as deep as the center section 147. The center section 147 may be of a uniform curvature or generally flat. Preferably, the center section 147 has additional slopes (not shown) to accommodate the spud cans 134, 137, and 140.
The sloped transom section 145 and the sloped bow section 150 are of a length along the depth and horizontal axes and angle sufficient such that the thrusters 124, 127, and 130 may be mounted with the necessary. Preferably, the angle of the sloped transom section 145 and the sloped bow section 150 with respect to the bottom of the hull is sufficient to allow efficient flow of water through the thrusters. In one embodiment, the angle of the sloped transom section 145 and the sloped bow section 150 with respect to the bottom of the hull will vary depending on the requirements of the thrusters. For example, the angle of the sloped transom section 145 and the sloped bow section 150 with respect to the bottom of the hull is preferably between about 15 and about 30 degrees, alternatively between about 17 and about 25 degrees, alternatively between 18 and 22 degrees, and alternatively about 20 degrees.
With respect to
Continuing with reference to
The hull 103 of the Elevating Support Vessel 100 is preferably made of 355 MPa steel. In an embodiment, the hull 103 of the Elevating Support Vessel 100 is from about 5 to about 15 meters deep, and preferably about 7.5 meters deep from the lowest point until the deck 106 of the Elevating Support Vessel 100. At full displacement the air gap is preferably about 11 meters, alternatively about 12.5 meters, alternatively about 13.5 meters, and alternatively about 15.5 meters.
In an embodiment, the Elevating Support Vessel 100 weighs about 6,800 metric tons at light ship. In this embodiment, the Elevating Support Vessel exerts a minimum of about 345 kilopascals per leg on the sea floor. The Elevating Support Vessel 100 may vary in weight from about 4,500 metric tons to about 11,000 metric tons at light ship. Alternatively, the Elevating Support Vessel 100 may vary in weight from about 6,800 metric tons to about 15,500 metric tons at full ship, and preferably from about 9,000 metric tons to about 13,500 metric tons.
The three jack-up legs 133, 136, and 139 may have a lattice, truss, or tubular configuration. Preferably, the jack-up legs 133, 136, and 139 may withstand greater than about 5 meter waves, alternatively greater than about 10 meter waves, and more preferably, greater than about 15 meter waves. The jack-up legs 133, 136, and 139 may withstand greater than about 50 knot winds, preferably greater than about 75 knot winds, and most preferably greater than about 100 knot winds. The jack-up legs 133, 136, and 139 may be able to withstand a wave period of about 13.5 seconds. The dimensions of the jack-up legs 133, 136, and 139 may vary depending on many factors, including the location of the platform or wells to be serviced. In an embodiment, the jack-up legs 133, 136, and 139 have an overall leg length of at least 100 meters, alternatively about 127 meters, an about 2.7 meter safety zone, a 7.5 meter leg tower, and an estimated sea bed penetration of about 3 to about 8.3 meters. This embodiment may yield a working water depth of from about 60 meters to about 90 meters, and alternatively a working water depth of from about 60 meters to about 75 meters.
With reference to
Continuing with reference to
In an alternative embodiment (not shown), there are two front azimuthing thrusters. In this embodiment, the bow of the Elevating Support Vessel 100 is widened—with respect to the configuration shown in FIG. 2—along the vertical axis to such that two front azimuthing thrusters may be mounted parallel along the vertical axis. The bow is also widened such that each of the front azimuthing thrusters may be mounted to the bow of the Elevating Support Vessel 100, along the vertical axis, such that their exhaust straddles the front jack-up leg 139. The two front azimuthing thrusters are preferably mounted to the bow of the Elevating Support Vessel 100, along the horizontal, at a generally front-most location.
The azimuthing thrusters 124, 127, and 130 may be any commercially available azimuthing thruster, which may be affixed to the Elevating Support Vessel 100 and provide sufficient horsepower and maneuverability such that the Elevating Support Vessel 100 is self-propelled. Preferably the azimuthing thrusters 124, 127, and 130 are capable of producing between 500 and 4,000 kilo-watts of power, alternatively about 2,500 kilo-watts of power. For example, the thrusters may be SP 35 azimuthing thrusters having a ducted propeller, available from Steerporp Ltd., located in Rauma, Finland. The Elevating Support Vessel 100 may have a maximum speed of from about 5 knots to about 10 knots, or greater than about 7 knots.
The crane-support legs 159 may be triangular shaped with the top end of the leg being thicker than the bottom end of the leg. The crane-support legs 159 may be made of double girder steel, alternatively an I shaped steel beam may be used. The crane-support platform 162 may be generally rectangular or square shape, and is preferably a lattice of support beams designed to be light-weight yet strong.
A crane-support column 165 is connected at one end to the crane-support platform 162. Preferably, the crane-support column 165 is welded into the center of the crane-support platform 162. In this manner, the weight of the crane 112 is distributed as evenly as possible across the crane-support structure 109. The crane 112 is rotatably affixed to the other end of the crane-support column 165. By rotatably affixed it is meant that the connection between the crane 112 and the crane-support column 165 permits the crane 112 to rotate about the radius of the crane-support column 165 from a first location to a second location.
The crane support 109, and its components, may weigh from about 150 metric tons to about 300 metric tons, and more preferably about 170 metric tons. The crane support 109, and its components, are preferably made of steel, and are more preferably 355 MPa medium strength steel.
The crane 112 may vary generally in size, and preferably has a 280 metric ton capacity at 20 meters. Alternatively, the crane has at least a 50 metric ton capacity at 20 meters, alternatively at least a 100 metric ton capacity at 20 meters, alternatively at least a 200 metric ton capacity at 20 meters, alternatively at least a 300 metric ton capacity at 20 meters, alternatively at least a 350 metric ton capacity at 20 meters, and alternatively at least a 500 metric ton capacity at 20 meters. A suitable crane 112 is a PC 250HD crane, which is commercially available from Australia Favelle Favco Cranes Pty. Ltd., located in Australia.
The tracks 156 may vary in length, but preferably run along the horizontal axis from the rear of the transom to a location generally behind the rear jack-up legs 124 and 127. In an embodiment, the tracks run along the horizontal axis from the rear of the transom to a length of about 20 meters, alternatively about 15 meters, alternatively about 10 meters. The tracks 156 are spaced apart from one another, along the vertical axis, at a distance such that the crane-support platform 162 may be large enough to evenly and safely distribute the weight of the crane 112 under load. Additionally, the tracks 156 are spaced apart from one another, along the vertical axis, at a distance such that there is room to store a variety of equipment and things beneath the crane-support platform 162 and between the tracks 156. The tracks 156 may be about 10 meters apart, along the vertical axis, alternatively about 15 meters apart, alternatively about 20 meters apart, alternatively about 25 meters apart. The tracks 156 must be sturdy to carry the weight of the crane-support 109, crane 112, and load. Accordingly, the tracks 156 preferably extend through the entire depth of the transom and are integral with the Elevating Support Vessel 100. Applicants believe, without wishing to be bound by the theory, that the tracks 156 absorb little to no dynamic moments or forces. Instead, the connection between the crane-support legs 159 and the track 156 permits the forces to be distributed in simple static directions.
The connection between the track 156 and the crane-support legs 159 is described with reference to
In an embodiment, the track 156 includes at one end, alternatively at either end, a stop 157. The stop 157 prevents the crane-leg shoe 168 from sliding off the track 156. The stop 157 is preferably from about two to three times as wide as the track 156, and in an embodiment about 1 meter. Preferably the stop 157 is from about 40 centimeters to about 80 centimeters in length, and preferably about 60 centimeters. The stop 157 may run the depth from the deck 106 to the top of the T-shaped portion of the track 156, alternatively the stop 157 may extend below the deck 106, or be shallower than the depth from the deck 106 to the top of the T-shaped portion of the track 156. The stop 157 may have protrusions 158 extending in the depth axis about eight to about 20 centimeters, preferably about 10 centimeters. The protrusions 158 preferably extend straight up along the depth axis, may be sloped away from each other, or extend up some distance and then slope away from each other.
In this manner, the crane 112 may be used in a number of ways. The crane 112 may be moved by skidding the crane support 109 across the tracks 159. The crane 112 may pick up a load from any point along the track 159. Thus, the crane 112 may pick up a load of the deck 106 of the Elevating Support Vessel 100, or from a location outside of the Elevating Support Vessel 100. The crane 112 may also be rotated 360° about the crane-support column 165 while under full load. The crane 112 may also be skidded along the tracks 159 while under load. Accordingly, the crane 112 may transport load or erect load in a self-contained manner, without need for any additional support vessels. The crane 112 has the additional benefit of allowing for the storage of equipment and things beneath the crane support 109. Because of the high clearance of the crane-support platform 162, the storage of equipment and things will not obstruct the movement of the crane 112. Additional uses of the crane 112 are discussed below.
A wind turbine (not shown assembled) may be segmented, towed, and transported by the Elevating Support Vessel 100. Preferably, the Elevating Support Vessel 100 is also capable of erecting the wind turbine offshore. In an embodiment, the Elevating Support Vessel 100 is also capable of erecting the wind turbine offshore without assistance from other vessels or equipment located not contained within the Elevating Support Vessel 100.
Suitable offshore wind turbines may include the 2.3 mega-watt wind-turbine generator, SWT-2.3-107, available from Siemens Wind Power A/S located in Brande, Demark. Other suitable wind turbines include the 3.6 mega-watt wind-turbine generator, SWT-3.6-107, capable of being planted in up to about 40 meters of water. For the purposes of this disclosure, and by way of example, the Elevating Support Vessel 100 should be assumed to be stowing, transporting, and erecting 3.6 mega-watt wind-turbine generators, unless otherwise stated. Such wind turbines may be segmented in at least three parts before being transported: a wind-turbine column (205
The wind-turbine columns 205 may be stowed as a group toward the transom of the Elevating Support Vessel 100 and behind either rear jack-up legs 133 and 136. Preferably, the wind-turbine columns 205 are stowed outside of the tracks 156 so not to impede the movement of the crane support 109 along the tracks 156. In an embodiment, the wind-turbine columns 205 are seated and secured within respective wind-turbine foundations 225 (shown in
The wind-turbine nacelles 210 may be stowed on the deck 106 of the Elevating Support Vessel 100. In an embodiment, at least one, two, or three wind-turbine nacelles 210 are stowed toward the rear of the transom of the Elevating Support Vessel 100 and behind either rear jack-up legs 133 and 136. In an embodiment, if wind-turbine columns 205 are stowed behind the rear jack-up leg 133, then wind-turbine nacelles 210 are stowed behind the other rear jack-up leg 136, and vice versa. In an embodiment, at least one, two, three, or four of the wind-turbine nacelles 210 are stowed between the tracks 156 and beneath the path of the elevated crane support 109. The wind-turbine nacelles 210, and any supporting packaging, may be of a size such that its height does not impede the movement of the elevated crane support 109 along the tracks 156. In an embodiment, the wind-turbine nacelles 210 may rest directly on the deck 106 of the Elevating Support Vessel 100. Alternatively, the wind-turbine nacelles 210 may rest within packaging, which may rest directly on the deck 106 of the Elevating Support Vessel 100. In any event, it is preferable that either the wind-turbine nacelles 210 or any supporting packaging is secured to the deck 106 of the Elevating Support Vessel 100 by suitable means including nylon straps or wire ropes.
The wind-turbine blades 215 are preferably stowed resting on shipping racks (not shown). These shipping racks preferably each contain three wind-turbine blades 215 stacked in a single vertical column. The shipping racks may be secured by nylon straps or wire ropes to a row, along the horizontal H axis as shown in
Near location, the Elevating Support Vessel 100 may hold station, moor, and/or select a jack-up location by any of the below-described methods. Secured to location, the crane 112 of the Elevating Support Vessel 100 may be used to assist in the erection of the wind turbines. In an embodiment, the crane 112 is used to lift a wind-turbine column 205, and secure the wind-turbine column 205 to an offshore wind-turbine base (not shown). The crane 112 may then be used to lift a wind-turbine nacelle 210, and secure the wind-turbine nacelle 210 to the installed wind-turbine column 205. The crane 112 may then be used to lift a wind-turbine blade 215, and secure the wind-turbine blade 215 to the hub of the installed wind-turbine nacelle 210. The crane 112 may be used to deconstruct the installed wind-turbine by the reverse process.
The Elevating Support Vessel 100 preferably has the ability to hold station. In an embodiment, the Elevating Support Vessel 100 holds station using the azimuthing thrusters. In this embodiment, a set point is determined. A GPS device, preferably in combination with a gyroscope and other attitude measuring devices, provide digital signals to a computer informing the computer how far off from the set point the Elevating Support Vessel 100 has traveled. The computer sends a signal to the azimuthing thrusters, which engages the azimuthing thrusters to correct for the error. Thus, in an embodiment, the azimuthing thrusters of the Elevating Support Vessel 100 are in signal communication with a computer. In an alternative embodiment, any number of the azimuthing thrusters may be in signal communication with a computer, and any number of the azimuthing thrusters may be in signal communication with each other and/or the computer. In these embodiments, the Elevating Support Vessel 100 may remain within about a three meter radius from the set point. The ability to hold station is especially important while the legs are being lowered to the sea/ocean floor until the Elevating Support Vessel 100 is supported by its jack-up legs. Preferably, the Elevating Support Vessel 100 can hold station, using only the azimuthing thrusters, in a current of between 0 to about 3 knots. In the embodiment wherein the Elevating Support Vessel 100 holds station during deployment of the jack-up legs, there may be forces acting on the jack-up legs, such as undercurrents. In such situations, the net forces acting on the Elevating Support Vessel 100 is called the effective current, and the Elevating Support Vessel 100 can preferably hold station in an effective current of between 0 to about 3 knots. In these embodiments, the surface current may or may not be above about 3 knots.
In another embodiment, the Elevating Support Vessel 100 may hold station using the azimuthing thrusters in combination with a mooring system. This embodiment is especially preferable if the current, or effective current, is greater than about 3 knots. The mooring system is preferably either a two or four-point mooring system, and a four-point mooring system is preferred in effective currents over about 3 knots.
In a two-point mooring system, a first anchor is connected to one end of the Elevating Support Vessel's 100 transom, and a second anchor is connected to the opposite end of the Elevating Support Vessel's 100 transom. In an alternative two-point mooring system, a first anchor is connected to one end of the Elevating Support Vessel's 100 bow, and a second anchor is connected to the opposite end of the Elevating Support Vessel's 100 bow. In a four-point mooring system, a first anchor is connected to one end of the Elevating Support Vessel's 100 bow, a second anchor is connected to the opposite end of the Elevating Support Vessel's 100 bow, a third anchor is connected to one end of the Elevating Support Vessel's 100 transom, and a fourth anchor is connected to the opposite end of the Elevating Support Vessel's 100 transom. Preferably, the azimuthing thrusters are used to correct for any deviation should the Elevating Support Vessel 100 deviate from its set point. The azimuthing thrusters are put to greater use in a two-point mooring system than in a four-point mooring system. The use of one, three, and greater than four anchors is also contemplated.
In an embodiment, the anchors each weight from about 4.5 megagrams to about 9 megagrams, and preferably about 6.8 megagrams. The anchors are preferably connected to the Elevating Support Vessel 100 by an about 3.8 centimeter thick wire rope, which is from about 760 meter to about 915 meters in length. Alternatively the anchors are connected to the Elevating Support Vessel 100 by a chain, or a combination of a wire rope and chain, which is from about 760 meter to about 915 meters in length.
In an embodiment, the crane 112 is used to retract the anchor. In this embodiment, once the first anchor is released from the sea/ocean floor the azimuthing thrusters will be used to correct for the deviation that the Elevating Support Vessel 100 undergoes from the set point. The azimuthing thrusters continue to correct for any deviation from the set point as the additional anchor(s) are retracted. Alternatively, after the first anchor is released from the sea/ocean floor, the azimuthing thrusters serve to hold tension against the other anchors such that the vessel holds station.
A method of selecting a location to jack-up an Elevating Support Vessel 100 is now described. In an embodiment of the method, an Elevating Support Vessel 100 is moved within proximity to an offshore structure, preferably, an oil and gas facility. The Elevating Support Vessel is preferably moved within about 30 meters from the edge of the platform, alternatively within about 20 meters, alternatively within about 10 meters. The Elevating Support Vessel 100 is moved around the platform to obtain a map of the sea floor. Alternatively, or in addition to the map obtained by the Elevating Support Vessel 100, a remote operated vehicle (“ROY”) (not shown) is deployed from the Elevating Support Vessel 100, and images the sea floor. The map of the sea floor is then used to determine a suitable location to lower the jack-up legs. Preferably, the location selected does not contain pits caused by previous jack-up vessels, commonly referred to as “can holes”, debris, pipe ties, or other obstructions. Once in location, the legs of the Elevating. Support Vessel 100 are jacked-up, and the Elevating Support Vessel 100 is raised out of the water.
The ROV may be an unmanned submersible. Preferably, the ROV can dive below the surface of the water and obtain detailed images of the sea floor using a side acoustic scanner and/or bottom contour sonar, and the like equipment. The ROV may have a range of from about 30 meters to about 300 meters, or more, which may permit the Elevating Support Vessel 100 to remain at a distance further away from the platform such as at least about 30 meters, alternatively at least about 50 meters, alternatively at least about 100 meters. In an embodiment, the ROV has an umbilical cord that carries power to it, as well as electrical signals and data to and from the Elevating Support Vessel 100. Alternatively, the ROV can be remotely controlled.
The sea floor may be mapped using any depth finding device and method, and is preferably mapped using side acoustic scanning and/or multi-beam echo scanning. Side acoustic scanning is similar to sonar, in that sound waves are transmitted out to a target area, i.e., the sea floor. The time for the sound waves to travel out to the target area and back to receiver of the side acoustic scanning device is used to determine the range to the target. The distance that the Elevating Support Vessel 100 is from the platform when mapping the sea floor will depend on the optimum range of the mapping device, i.e., side acoustic scanner. The Elevating Support Vessel 100 is preferably far enough from the platform's edge to ensure safe movement, yet close enough to the platform's edge to obtain a map of the sea floor. A preferred depth finding device and method is the use of a SeaBeam 1185 in conjunction with HYPACK™ software. Such a system is available from L-3 Communications Corporation located in New York, N.Y. HYPACK™ is a registered trademark of Coastal Oceanographics, Inc., located in Middlefield, Conn.
The reach of the Elevating Support Vessel's 100 onboard skiddable crane permits the Elevating Support Vessel 100 to select a position further away from the platform than previously possible. In an embodiment, the Elevating Support Vessel 100 is located and jacked-up between about 7 and about 14 meters from the edge of the platform, alternatively from about 15 meters to about 20 meters, and alternative at most about 23 meters from the edge of the platform.
While specific alternatives to steps of the invention have been described herein, additional alternatives not specifically disclosed but known in the art are intended to fall within the scope of the invention. Thus, it is understood that other applications of the present invention will be apparent to those skilled in the art upon reading the described embodiment and after consideration of the appended claims and drawings.
This application is a continuation in part of U.S. application Ser. No. 12/079,309 filed Mar. 26, 2008, which claims the benefit of U.S. Provisional Application No. 60/920,965 filed Mar. 30, 2007 and U.S. Provisional Application No. 61/030,815 filed Feb. 22, 2008, this application also claims the benefit and priority of U.S. Provisional Application No. 61/094,269 filed Sep. 4, 2008.
Number | Date | Country | |
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60920965 | Mar 2007 | US | |
61030815 | Feb 2008 | US |
Number | Date | Country | |
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Parent | 12079309 | Mar 2008 | US |
Child | 12554651 | US |