Abstract
A shallow water seabed terminal for storing and loading or unloading hydrocarbons, such as LNG, oil or gas, includes a removable floatable module and a removable seabed substructure intended to be supported by a seabed. The floatable module is releasably fixed to the seabed substructure so that a harbour terminal is formed. The seabed substructure includes a base structure provided with buoyancy devices, a wall structure extending upwardly from the base structure and arranged along at least a part of the periphery of the base structure. The base structure is also provided with an opening in the wall structure for allowing the floatable module to be berthed in and supported by the seabed substructure. The base structure is provided with a submerged beam or base slab structure which extends laterally out from the vertical wall structure and is configured to support the floatable module.
Claims
1. A shallow water seabed terminal for storing and loading or unloading hydrocarbons, said seabed terminal comprising a removable floatable module, and a removable seabed substructure configured to be supported by a seabed, the floatable module being releasably fixed to the seabed substructure so that a harbour terminal is formed, the seabed substructure including a base structure provided with buoyancy devices, a wall structure extending upwardly from the base structure and arranged along at least a part of a periphery of the base structure, the base structure being provided with an opening in the wall structure for allowing the floatable module to be berthed in and supported by the seabed substructure, wherein the base structure is provided with a submerged beam structure extending along the circumference of the base structure and extending laterally out from the wall structure and configured to support the floatable module, the submerged beam structure being provided with sleeves or ducts extending through the submerged beam structure and being configured to receive piles to be driven down into a soil of the seabed, wherein an upper end of each pile is terminated and rigidly locked or anchored in the submerged beam structure ensuring that the weight of the floatable module when berthed is transferred directly through the submerged beam structure and through the piles into a deeper layer of the seabed soil.
2. The seabed terminal according to claim 1, wherein heads of the piles are configured to be terminated below sea level.
3. The seabed terminal according to claim 1, wherein the sleeves or ducts form an angle with the vertical axis, securing the piles in an inclined position when piled.
4. The seabed terminal according to claim 1, wherein an underside of the base structure has no load bearing contact with the soil of the seabed and variable, operational and environmental loads of the seabed terminal are taken up by the piles.
5. The seabed terminal according to claim 1, wherein the base structure is a jacket frame structure.
6. The seabed terminal according to claim 1, wherein the wall structure is an integrated part of the base structure.
7. The seabed terminal according to claim 1, wherein the seabed substructure is ballasted.
8. The seabed terminal according to claim 1, wherein at least parts of the wall structure extend above a water surface.
9. The seabed terminal according to claim 1, wherein the seabed substructure includes piling of the wall structure extending from a top of the wall structure through a bottom of the wall structure.
10. The seabed terminal according to claim 1, wherein the opening in the wall structure for introducing the floatable module is closable with a closing mechanism forming a closed wall structure at the periphery of the base structure.
11. The seabed terminal according to claim 1, wherein the sleeves or ducts are provided with sealing devices at a lower end, preventing grout to escape downwardly.
12. The seabed terminal according to claim 1, wherein an inner surface of the sleeves or ducts is provided with spacers, configured to prevent the piles from coming into direct contact with the inner surface of the sleeves or ducts, thereby establishing an annulus for filling of grout.
13. The seabed terminal according to claim 1, wherein an inner surface of the sleeves or ducts is provided with a number of shear providing devices, securing proper shear and adhesion between the inner surface of the sleeves or ducts and an external surface of the pile.
14. The seabed terminal according to claim 1, wherein the base structure and the floatable module are divided into the same number of bulkheads and vertical walls of the bulkheads form a structural beam so that vertical forces of the storage module are transferred directly into the structural beam of the base structure.
15. The seabed terminal according to claim 1, wherein the floatable module is locked to the base structure by one of a mechanical locking device and shear force plates welded to the seabed substructure.
16. The seabed terminal according to claim 2, wherein the sleeves or ducts form an angle with the vertical axis, securing the piles in an inclined position when piled.
17. The seabed terminal according to claim 2, wherein an underside of the base structure has no load bearing contact with the soil of the seabed and variable, operational and environmental loads of the seabed terminal are taken up by the piles.
18. The seabed terminal according to claim 3, wherein the wall structure is an integrated part of the base structure.
19. The seabed terminal according to claim 4, wherein the wall structure is an integrated part of the base structure.
20. The seabed terminal according to claim 17, wherein the wall structure is an integrated part of the base structure.
21. The seabed terminal according to claim 1, wherein the hydrocarbons comprise at least one of LNG, oil, and gas.
22. The seabed terminal according to claim 2, wherein the heads of the piles are configured to be flush with an upper surface of the submerged beam structure.
23. The seabed terminal according to claim 12, wherein the spacers are provided at an upper and lower end of the sleeves or ducts.
24. The seabed terminal according to claim 1, wherein the floatable module is supported above the sea level by providing the floatable module with fixation devices extending sideways out from the floatable module and configured to be fixed to the top surface of the walls, all above the sea level.
25. The seabed terminal according to claim 1, wherein the sleeves or ducts form an angle with the vertical axis, securing the piles in an inclined position when piled, wherein an underside of the base structure has no load bearing contact with the soil of the seabed and variable, operational and environmental loads of the seabed terminal are taken up by the piles, wherein the seabed substructure includes piling of the wall structure extending from a top of the wall structure through a bottom of the wall structure, wherein the sleeves or ducts are provided with sealing devices at a lower end, preventing grout to escape downwardly and wherein the floatable module is supported above the sea level by providing the floatable module with fixation devices extending sideways out from the floatable module and configured to be fixed to the top surface of the walls, all above the sea level.
26. The seabed terminal according to claim 1, further comprising a grid system, wherein the upper end of each pile is terminated and rigidly locked or anchored in at least one of the submerged beam structure and the grid system below sea level, ensuring that the weight of the floatable module when berthed is transferred directly through the at least one of the submerged beam structure and the grid system through the piles into the deeper layer of the seabed soil.
Description
SHORT DESCRIPTION OF THE DRAWINGS
(1) The device according to the invention can be explained in more detail in the following description with reference to the enclosed figures, wherein:
(2) FIG. 1 shows schematically a view seen from above of a seabed substructure comprising a base structure, a wall structure and channels;
(3) FIG. 2 shows schematically a view seen from above of the storage module towed to the site for mating with the seabed substructure;
(4) FIG. 3 shows schematically a view of five substructures mated with five respective storage modules together forming a shallow seabed terminal according to the invention;
(5) FIG. 4 shows schematically a vertical section through a side wall and a part of a bottom structure of the sea bed substructure, showing the duct for a pile and the upper end of the pile, both duct and pile being vertically arranged and with the substructure resting with its bottom part on the sea bed;
(6) FIG. 5 showing schematically and in an enlarged scale a lower spacer and grout packer, arranged at the lower end of the duct intended to receive the pile, the pile being omitted;
(7) FIG. 6 shows schematically and in an enlarged scale the upper spacer in the pile duct, where the pile is omitted;
(8) FIG. 7 shows schematically a horizontal section through the line A-A in FIG. 5, showing the output end of the grout filling line;
(9) FIG. 8 shows a second embodiment of the invention, provided with 50 pile sleeves arranged around the periphery area of the substructure;
(10) FIG. 9 shows schematically a vertical section through a first embodiment of a side wall of the substructure according to the invention, indicating use of inclined pile sleeves and piles;
(11) FIG. 10 shows schematically a vertical section through a second embodiment of a side wall of the substructure according to the invention, indicating use of inclined pile sleeves and piles, skewed in opposite direction compared to the embodiment disclosed in FIG. 9;
(12) FIG. 11 shows schematically a view in perspective of another embodiment of the invention, showing the assembly placed on a sloped seabed; and
(13) FIG. 12 showing schematically in perspective one proposed solution for fixing the module to the seabed superstructure.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS
(14) It should be noted that in the following description of the embodiments shown in the Figures, the same reference numbers are used for identical or similar structures and features.
(15) FIG. 1 shows schematically a view seen from above of an embodiment of the seabed substructure 10 according to the invention. The seabed substructure 10 comprises a base structure 11 with an upward extending wall structure 12 arranged along at least a part of the periphery of the base structure 11. The wall structure 12 being an integrated part of the base structure 11, together forming a seabed substructure 10. Both the base structure 11 and wall structure 12 are provided with buoyancy devices (not shown). Such buoyancy means may be in the form of tanks and compartments in the base structure 11 and in the upwards extending wall structure 12. The embodiment of the seabed substructure 10 shown in FIG. 1 is provided with a bottom beam structure 15 in longitudinal and transverse direction, forming upwards open compartments 13 in the base structure. The compartments 13 may be closed at the lower end by a bottom slab or the compartments may be open downwards, providing access to the piles 22 in case the base structure 11 is in an elevated position more or less above the seabed. Said longitudinal and transverse beams or walls 15 serve as a supporting, strengthen surface for supporting a floatable storage module to be floated in between the upwards extending wall structure 12, over the base structure and ballasted to rest on said surface. Upwards extending walls 12 extend along three sides of the base structure 12 and is provided with an opening 18 in the wall structure for introducing a floatable storage module 20 in over the base structure 12. The storage module 20 being removable arranged on top of the base structure 11 within the wall structure 12, together forming a seabed unit 30. At least one seabed unit 30 constitutes a seabed terminal 40.
(16) The seabed substructure 10 are floating and has means for ballasting (not shown) and is intended to be placed on or just above the seabed 19, supported by a number of piles 22 or optionally, also resting on the seabed 19 due to gravity, fixed by means of piles. The upward extending wall structure 12 of the substructure 10 has perforations or ducts/sleeves through the wall structure for optional and/or additional piling, and also there are perforations in the base structure 11 for receipt of piles 22. The ducts and accessories for receiving the piles 22 will be described in further details below. A vessel 16 with machines and tools for piling are moored next to the wall structure 12 to perform the piling operations. As indicated in FIG. 1, piles 22 are arranged both in longitudinal and transverse direction along the foot of the three walls along the submerged front beam beneath the opening of the base structure 11, and along the internal walls 25 forming the upwards open compartments 13. In such way the entire footprint or at least parts of the footprint may be provided with piles for supporting the base structure 11 properly. The number of piles 22 used and their position, diameter and length depend on the weight to be supported and on the seabed soil condition.
(17) An advantage according to the present invention is that the seabed substructure 10, constituting a part of the seabed unit 30 for floating modules, such as a floatable LNG storage unit or barge according to the invention, can be lowered down to installed offshore or near shore, be removed, be moved and be replaced to form new individual configurations as required using known techniques.
(18) FIG. 2 shows schematically a view seen in perspective from above, showing a storage module 20 being towed by a towing vessel 16 to the site to mate with the partly submerged, pre-installed seabed substructure 10. The storage module 20 is floating and has means for ballasting (not shown) and is preferably made from steel, although also other materials can also be used such as concrete. It should be appreciated that the storage module 20 according to the present invention also may be provided with means, such as loading systems, cranes, winches etc. on top of the storage module. When the storage module 20 arrives at the site, it is mated with the seabed substructure 10 placed at the seabed 19. During this mating operation, the floating module 20 is manoeuvred in through the opening 18 and in between the two parallel upwards extending side wall structures 12. The wall structure 12 of the seabed substructure 10 is extending up above the water surface 19 (as seen in FIG. 2) until the floating storage module 20 is guided on top of the base structure 11, within the wall structure 12. The module 20 is the ballasted so that module 20 rests stably on the base of the seabed substructure 10, forming a seabed an assembled unit 30.
(19) An advantage according to the present invention is that the storage module 20 easily may be converted to store different oil related products and bunkering and/or serve different functions. The storage module 20 can be lowered on the seabed substructure 10, be removed, be moved and be replaced to form new individual configurations as required using known techniques.
(20) FIG. 3 shows schematically a view in perspective, seen from above of a seabed terminal 40 comprising five seabed units or assemblies 30 placed in a pre-designed manner. It is an advantage of the present invention to arrange the seabed units or assemblies 30 in a way that waves are dampened efficiently by breaking and cancellation effects. The seabed units 30 according to the invention, forming the seabed terminal 40, are placed apart at a required distance. The distance between the units 30 is decided by the wave prevailing frequencies intended to be dampened and the frequencies allowed passing between the units 30. This distance can be calculated with known methods or be found by means of basic experiments. The orientation of the units or assemblies 30 is choses such as to establishing a required shelter, preventing waves coming from a direction more or less perpendicular to the longitudinal direction of the terminal 40. It should be appreciated that the mooring lines, mooring points etc. for mooring the vessel are not shown. The bridges, gangways etc. between the seabed units 10 are shown in FIG. 3.
(21) FIG. 4 shows schematically a vertical section through a side wall 12 and a part of a base structure 11 of the sea bed substructure, showing the ducts 21 for a pile 22 and the upper end of the pile 22, both duct 21 and pile 22 being vertically arranged and with the substructure 11 resting with its bottom plate 23 directly on the sea bed 19. Once a pile 22 is driven into its intended depth in the seabed 19 soil, a annulus 25 between the external surface of the pile 22 and the surface of the duct wall 21 is grouted by injecting grout from a grout producing plant (not shown) through a grout supply line 24. Said grout supply line 24 has its outlet 25 at the lower end of the duct 21. As a consequence of such outlet position, injected grout from the supply line 24 will be pressed upwards through the annulus 25 until the injected grout exits at the top of the duct 21. In order to prevent the grout from being forced downwards and oy of the annulus 25 and into the interface between the lower surface of the bottom plate 23 of the base structure 11 and the seabed 19, a ring formed stopping seal 26 is arranged, having contact surface against the outer surface of the pile 22 around its entire circumference. The stopping seal 26 may be in the form of a circular hose with cylindrical cross section, or as a semi-circular body, both free ends of the semi-circular body being sealing fixed to the surface of the duct 21, extending around the entire circumference of the duct 21, providing a fluid tight seal. The interior void of the seal 26 is fluid contact with a pressurized source (not shown) through a fluid supply line 27, securing supply of a pressurized fluid to the interior of the seal at the start-up of the grouting process, causing the stopping seal to expand, and possibly relieving the fluid pressure upon completed grouting process. The seal 26 will be described in larger details below in connection with FIG. 5.
(22) As indicated in the FIG. 4, the upper entrance of the duct 21 may be provided with section having a lager diameter than the remaining part of the duct 21, having a downwards conical transition part in order to ease entering the lower end or bottom end of the pile 22 into the duct 21 at the initial phase of the piling process. Both at the top and the bottom of the duct 21, spacers 34 are arranged in order to secure a minimum distance between the outer surface of the pile 22 and the duct 21 wall, enabling proper grouting of the annulus around the pile 22. The entrance surface of the spacers may be a skewed to ease passage of the pile through the duct 22 past the spacers 34.
(23) FIG. 5 showing schematically and in an enlarged scale a lower spacer and grout packer 28, arranged at the lower end of the duct 21, intended to receive the pile 22 (not shown). As shown in FIG. 5, a grout distribution channel 29 is arranged at the outlet end of the grout supply line 24, for example extending sideways in circumferentially direction of the duct 21. The channel 29 may extend around the entire circumference of the duct. Alternatively, several supply lines 24, each with an enlarged channel may be provided. Moreover, the embodiment shown of the annular seal or inflatable grout packing body 26 is in the form of a semi-cylindrical body of an inflatable material, fixed to the circumference surface of the duct 21 in a sealing manner, for example by means of bolts 31 or glued, or the like. The interior of the void of the seal or packer body 28 communicates with the end of the fluid line 27 for supply of a pressurized fluid to the void, At the extreme point or top of the packer body 28, the packer body is provided with circumferentially arranged fins 32, enhancing the sealing contact surface of the packer body 28.
(24) As also indicated both in FIGS. 4 and 5, shear keys 33 are arranged on the wall of the duct 21 facing the pile 22 to be installed. The shear keys 33 are evenly distributed around the entire circumference of the duct 22 at different height.
(25) FIG. 6 shows schematically and in an enlarged scale the upper end of the duct 22, disclosing use of spacers 34 arranged around the in exposed surface of the pile duct 21. The spacers 34 may be made of vertical metal strips fixed to the duct 21 wall, providing space between adjacent spacers to allow for complete filling of grout in the annulus 25.
(26) FIG. 7 shows schematically a horizontal section through the line A-A shown in FIG. 5, showing a row of ducts 21 intended for receipt of piles 22 and the output end of the grout filling line 24 and the exit of the fluid supply line 27 to the interior of the stopping seal 26. The inner surface of the ducts is provided with vertical spacers, distanced apart around the circumference of the duct 21. The spacers 34 may have a limited width, extending vertically a certain limited length at the lower end of the duct 21. The section shown in the Figure discloses three ducts 21, of which a pile 22 is positioned in the duct 21. As shown an annulus 25 is established between the duct 21 wall and the pile 22. Because of the spacers 34 a void is established around the entire annulus 25.
(27) FIG. 8 shows a second embodiment of the base structure 11, provided vertical walls 12 arranged on three sides and intended to extend up above sea level 37 when installed on the seabed 19. Moreover, the disclosed embodiment is provided with an open front without a vertical wall intended to extend up above sea surface, leaving an opening 18 for entry of the floating module 20 to be towed in and over the base structure 11. The base structure 11 is provided with fifty pile ducts 22 arranged around the periphery area of the substructure. As indicated, the ducts 22 are arranged along all four sides of the seabed substructure 10.
(28) FIGS. 9 and 10 show schematically a vertical section through an embodiment of a side wall 12 of the substructure 11 according to the invention, indicating use of inclined pile sleeves or ducts 21 and piles 22 installed and driven into the seabed 19. As indicated the sideways displacement of the lower end of the pile in the seabed. The sideways displacement of the pile 22 depends on the angle of inclination a and the length of the pile 22. As indicated in FIGS. 9 and 10, the upper end of the pile 22 is fixed to a sideways extending bottom slab 35 forming an integral part of the vertical wall 12 and extending along at least three sides the substructure 11, possibly also the forth side, i.e. a transverse beam, interconnecting the two free ends of the substructure 11 at its bottom part 11.
(29) FIG. 11 shows schematically a view in perspective of another embodiment of the invention, showing the assembly 10,20 placed on a sloped seabed 19. The embodiment shown in FIG. 11 has a base structure 11 without the bottom beam structure 15. Moreover, there are no structures in the form of the sea bed structure interconnecting the two sidewalls 12. As shown the floating module 20 is resting on the bottom slab 35 extending laterally out from the wall structure 12, such bottom slab 35 extending preferably along the three walls 12 at their lower ends. Moreover, as disclosed the pile heads are terminated below the sea level 37, more or less coinciding with the upper surface of the bottom slab 35.
(30) The seabed substructure 10 and the storage module 20 may be constructed at the harbour site, build at a remote construction site, towed and placed at site. The seabed units 30 and the seabed terminal 40 are formed according to the local environmental conditions such as depth of water, type of ocean bottom, wave formations and where possible, negative effects from environmental forces such as waves, wind and current are minimised. Dependent on desired mooring direction and position for the LNG ship, the seabed substructures are placed on the ocean bottom in a desired configuration such that the desired loading conditions for the LNG ship are the best possible according to operative and safety considerations.
(31) According to the embodiment disclosed in FIG. 11, only the one side or part of the one side is in contact with the seabed, while the remaining parts are only supported by the files 22. It should be appreciated that the entire bottom of the seabed structure, with or without the base slab 35, also may rest on the seabed, or the seabed structure may be positioned such that none part of the base structure, with or without the base slab 35 is in contact with the seabed, all forces appearing being taken by the piles.
(32) FIG. 12 shows schematically in perspective a view of floatable structure 20 in a position where the floatable structure is fixed to the base structure 11 by means of a number of fixation devices 38, each in the form of a steel plate intended to be fixed to the surface of the floating structure 20 and a corresponding steel plate intended to be fixed to the top surface of the vertical walls 12 of the base structure 11. A vertical shear plate is fixed to both plates the vertical shear plate being arranged perpendicular with respect to said two plates on the base structure 11 and floating structure 20 respectively and also vertical with respect to the surface of the two structures 11,20. If the base structure 11 and the wall are made of steel, the two plates are welded to the said structures. If the two structures are made of concrete, the steel plates are welded to steel plates embedded in the respective concrete walls. Such configuration of the fixation devices provides access to the fixation devices for maintenance etc.
(33) According to one embodiment of the invention, sixty one piles having a diameter of 2.2 m and e length of 50 m are required in order to sustain the maximum environmental design loads. These piles are inclined with a 5 angle from the vertical in order to reduce the ground effect. In this context, it should be appreciated that where piles supporting the base structure are positioned close to each other a simple and conservative approach mat be to reduce the oiling capacity to approximately of a single pile capacity, when considering load cases.
(34) It should be appreciated that the piles may extend vertically down into the seabed or, they may be arranged inclined with respect to the vertical, either in same direction, inwards or outwards, or a combination of the same.
(35) The seabed substructure may also be provided with a harbour section 36, configured for allowing vessels to moor alongside the harbour section 36. The construction material may be concrete or steel or a combination of both. The harbour section 36 is fixed to and built into at least one of the vertically extending walls 12, so that all forces and loads is taken by the seabed substructure 10 and transferred to the piles. Moreover, the harbour section may preferably be arranged on the opposite side(s) of the prevailing direction of wind and/or waves, providing a shelter for the vessel(s) moored along the harbour section 36.
(36) In addition to or in lieu of use of gravity for supporting the floating structure 20 to the seabed structure 11, one way of fixing the floatable module 29 to the seabed structure may be to provide the floatable structure with a number of fixing devices configured in such way that fixing points between the floatable structure and the seabed structure are above sea level 37, preferably arranged on top of the vertically extending walls. In such case the fixing points may easily be accessed for inspection and maintenance and possibly also for releasing the floatable unit from the seabed structure. Although the embodiments shown are provided with laterally extending beams extending into the U-shaped base structure, it should be appreciated that such laterally extending beams also may extend outwards from the vertical walls, allowing for corresponding types of piling also on the opposite side of the vertical walls.
