Floating storage vessel with extension sections and offshore terminal
11541973 · 2023-01-03
Assignee
Inventors
Cpc classification
B63B35/44
PERFORMING OPERATIONS; TRANSPORTING
B63B21/50
PERFORMING OPERATIONS; TRANSPORTING
B63B2035/448
PERFORMING OPERATIONS; TRANSPORTING
B63B2035/4486
PERFORMING OPERATIONS; TRANSPORTING
International classification
B63B35/44
PERFORMING OPERATIONS; TRANSPORTING
B63B21/50
PERFORMING OPERATIONS; TRANSPORTING
Abstract
Offshore terminal apparatus which in various examples comprises a floating storage vessel which is spread-moored in fixed heading orientation to a seabed offshore by spread mooring lines, the floating storage vessel comprising a hull having bow and stern ends and which at either or both the bow end and the stern end is fitted with an extension section and includes coupling means on the extension section to couple spread mooring lines to the floating storage vessel.
Claims
1. A floating storage vessel comprising a hull having bow and stern ends and which at either or both the bow and stern ends is an elongated extension section projecting horizontally away from an upper part of the hull, the extension section having at least two couplings spaced apart from one another on the extension section, each coupling engaging a separate spread mooring line.
2. The floating storage vessel as claimed in claim 1, wherein the hull comprises a hull deck, and the extension section is arranged to be aligned in elevation with the hull deck.
3. The floating storage vessel as claimed in claim 1, wherein the extension section comprises a box structure of welded plates and an extension deck on the box structure.
4. The floating storage vessel as claimed in claim 3, wherein the couplings are arranged on or accessible by personnel from the extension deck.
5. The floating storage vessel as claimed in claim 1, wherein the extension section comprises a box structure which extends from a first end to a second end in a horizontal direction, the first end of the box structure connecting to the hull at an upper location on the bow or stern end, wherein the box structure may be supported by at least one bracing member connecting to the box structure at a location between the first and second ends of the box structure, or at the second end of the box structure, and to the hull at a lower location on the bow or stern end, which is near a propeller location if disposed on the stern or near a bulb location if disposed on the bow.
6. The floating storage vessel as claimed in claim 1, wherein the extension section comprises a box structure comprising welded steel plates, wherein the box structure is elongate to extend between first and second ends, the extension section being welded at the first end to connect the box structure to the hull at the bow or stern end, said connection of the first end of the box structure being the only or the only required connection of the structure to the hull.
7. The floating storage vessel as claimed in claim 1, wherein the extension section at either or both the bow and stern ends has first and second ends, the first end of the extension section being connected to the hull at the bow or the stern end, and extending from the first end toward the second end in the longitudinal direction of the hull.
8. The floating storage vessel as claimed in claim 1, wherein the hull has a longitudinal axis, and the extension section at either or both the bow and stern ends is a deviated extension section, wherein the deviated extension section extends from first end, which is connected to the hull at the bow end or the stern end, toward the second end at an angle away from the longitudinal axis.
9. An offshore terminal apparatus comprising: a floating storage vessel which is spread-moored in fixed heading orientation to a seabed offshore by spread mooring lines, the floating storage vessel comprising a hull extending along a longitudinal axis, the hull having bow and stern ends and which at either or both the bow end and the stern end an elongated extension section projects away from the hull so as to be parallel with the longitudinal axis, the extension section having at least four spaced apart couplings disposed along a portion of the length of the extension section, each coupling engaging a separate spread mooring line.
10. The offshore terminal apparatus as claimed in claim 9, further comprising a cargo vessel, the cargo vessel being moored to the floating storage vessel in side-by-side relationship for transferring fluid cargo between the floating storage vessel and the cargo vessel.
11. The offshore terminal apparatus as claimed in claim 10, wherein the cargo vessel is moored in a mooring area between the bow end and stern end spread mooring lines.
12. The offshore terminal apparatus as claimed in claim 10, wherein the floating storage vessel comprises bow and stern extension sections, and the cargo vessel is moored in a mooring area alongside the floating storage vessel between the extension sections, the couplings on the extension sections defining points of departure for the spread mooring lines, so that at least a predetermined distance or gap is maintained horizontally between the nearest spread mooring lines and the moored cargo vessel in the mooring area.
13. The offshore terminal apparatus as claimed in claim 10, wherein the cargo vessel is typically moored so that a mid-ship manifold of the cargo vessel is located opposite a mid-ship manifold of the floating storage vessel.
14. The offshore terminal apparatus as claimed in claim 10, further comprising first tubing for transferring fluid cargo between the floating storage vessel and the cargo vessel.
15. The offshore terminal apparatus as claimed in claim 10, further comprising a platform or a transfer tower supported upon the seabed, and second tubing for transferring fluid cargo between the floating storage vessel and the platform or the transfer tower structure.
16. The offshore terminal apparatus as claimed in claim 15, further comprising the platform and wherein the fluid cargo is liquefied gas, and a regasification facility on the platform for regasifying the liquefied gas.
17. The offshore terminal apparatus as claimed in claim 10, further comprising third tubing for communicating the fluid cargo between the platform or the transfer tower and shore.
18. The offshore terminal apparatus as claimed in claim 15, wherein the platform or transfer tower is arranged on an opposite side of the floating storage vessel to the cargo vessel.
19. An extension section for a floating storage vessel comprising a hull comprising one or more holds or tanks in the hull for storing fluid, the hull extending along a longitudinal axis between a bow end and a stern end, the extension section comprising: an elongated structure which extends parallel with the longitudinal axis between a first end and a second end, the first end of the structure affixed to the stern end or the bow end of the hull with the second end being arranged distally from the stern or bow end; a plurality of couplings spaced apart from one another along the structure for coupling spread mooring lines to the extension section.
20. The extension section as claimed in claim 19, wherein the structure comprises welded steel plates.
21. The extension section as claimed in claim 20, wherein the structure comprises or is an elongated box structure.
22. The extension section as claimed in claim 21, wherein the first end of the box structure is weldable to the bow or stern end of the hull to join the box structure to the hull, the box structure being configured to be sufficiently supported for operational use through only said join of the first end of the box structure to the hull.
23. The extension section as claimed in claim 19, wherein the structure further comprises a deck for crew or personnel access, and the plurality of couplings are disposed along the deck.
24. The extension section as claimed in claim 19, wherein the hull comprises a hull deck, and the structure is configured to be connected to the hull, the structure being aligned with the hull deck.
25. The extension section as claimed in claim 19, wherein the structure extends from the first end to the second end along curve or dog leg.
26. The extension section as claimed in claim 19, where the elongated structure has a first side and a second side extending between the first end and second end, wherein the plurality of couplings comprises at least three couplings longitudinally spaced apart from each other along each of the first and second sides.
27. An offshore fluid cargo handling facility comprising: a marine platform for processing fluid cargo; a floating storage vessel spread moored adjacent the marine platform via a plurality of spread mooring lines, the floating storage vessel comprising a hull extending along a longitudinal axis, the hull having a bow end and a stern end, with an elongated extension section projecting away from the hull at each of the bow and stern end so as to be parallel with the longitudinal axis, each extension section having a first elongated side and a second elongated side with at least three couplings spaced longitudinally apart from one another along each elongated side, wherein one of the plurality of spread mooring lines is attached to each coupling; one or more aerial fluid cargo hoses extending between the marine platform and the floating storage vessel; a fluid cargo vessel having a bow end and a stern end and moored to the floating storage vessel so that the bow end and the stern end of the fluid cargo vessel are spaced apart from the spread mooring lines of the floating storage vessel.
28. The offshore fluid cargo handling facility of claim 27, wherein the fluid cargo vessel has a cargo vessel length defined between the bow end and the stern end of the fluid cargo vessel and the floating storage vessel has a storage vessel length defined between the bow end and the stern end of the floating storage vessel, wherein the cargo vessel length and the storage vessel length are approximately the same.
29. The offshore fluid cargo handling facility of claim 27, wherein the fluid cargo vessel has a cargo vessel length defined between the bow end and the stern end of the fluid cargo vessel and the floating storage vessel has a storage vessel length defined between the bow end and the stern end of the floating storage vessel, wherein the cargo vessel length is longer than the storage vessel length.
30. The offshore terminal apparatus as claimed in claim 9, wherein at both the bow end and the stern end an elongated extension section projects away from the hull so as to be parallel with the longitudinal axis, the extension section having at least four spaced apart couplings disposed along a portion of the length of the extension section, each coupling engaging a separate spread mooring lines.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) There will now be described, by way of example only, embodiments of the invention, with reference to the accompanying drawings, in which:
(2)
(3)
(4)
(5)
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(7)
DETAILED DESCRIPTION
(8) With reference to
(9) The storage vessel 10 is spread-moored by means of spread mooring lines 16a, 16b in fixed heading orientation with respect to the seabed. The bow end spread-mooring lines 16a extend from the bow end extension section 15a to mooring members 18a on the seabed. The stern end spread mooring lines 16b extend from the stern end extension section 15b to mooring members 18b on the seabed. Each spread mooring line 16a, 16b has a first end which is connected to coupling means 86a, 86b on the extension section 15a, 15b and a second end which is connected to the mooring member 18a, 18b. The first end of the spread-mooring line 16a, 16b is connected to the extension section 15a, 15b above sea level, typically at or near a deck level of the hull of the floating storage vessel or the extension section. The second end of the spread mooring line 16a, 16b connects underwater to the seabed mooring member 18a, 18b at or near the seabed. The spread mooring lines 16a, 16b therefore penetrate the water surface on their trajectory from the extension section 15a, 15b toward the seabed mooring member 18a, 18b.
(10) The spread-mooring lines 16a extend away from the floating storage vessel 10 in a direction D forming a spread angle α with respect to a longitudinal axis 19 of the floating storage vessel. The spread-mooring lines 16b extend away from the floating storage vessel 10 in a direction E forming a spread angle β with respect to the longitudinal axis 19 of the floating storage vessel 10, in the opposite sense to the spread angle α.
(11) A mooring area 33 is defined alongside the floating storage vessel between the bow end spread mooring line 16a, and the stern end spread mooring line 16b.
(12) In
(13) In
(14) By virtue of the extension sections 15a, 15b, the mooring lines 16a, 16b are positioned away from cargo vessel 20. Safety gaps 34a, 34b are established between the hull of the moored cargo vessel 20 and the nearest mooring line 16a, 16b at each end of the mooring. Preferably, the extension sections are provided so that the defined safety gap provides clearance of at least 20 m between the mooring lines 16a, 16b to the cargo vessel when moored. The hull of the cargo vessel 20 is typically of the same or similar length as that of the floating storage vessel 10 before fitted with the extension sections 15a, 15b. The mooring area 33 can allow cargo vessels 20 of the same or somewhat larger size than the floating storage vessel to be brought alongside more easily and/or under control in adverse conditions. Tugs 43 which may be required to assist the cargo vessel 20 can be operated at more favorable positions relative to the cargo vessel and may operate in an operating area between bow end and stern end spread mooring lines while maintaining a predefined clearance distance to the nearest mooring line, e.g. the same distance as the safety gap. The tugs can operate in the mooring area 33 before the cargo vessel has fully arrived alongside the floating storage vessel. The spread-moored configuration can therefore be viable for side-to-side transfer of fluid cargo from large tanker ships. Cargo vessels 20, e.g. tankers, for fluid cargo transport and offloading or loading at offshore fluid transfer terminals are typically available “off the shelf” as part of the world fleet, but they are typically of similar size, and variation is limited. When the floating storage vessel 10 is also of the same kind, i.e. an out of service cargo vessel, frequently situations may occur in prior art where the available cargo vessels are unsuited for side-by-side mooring alongside the floating storage vessel. The solution of providing the extension sections 15a, 15b allows spread mooring of the floating storage vessel with greater freedom for safe maneuvering the cargo vessel 20 alongside the floating storage vessel. The cargo vessel 20 can be brought alongside and moored without transgressing the safety gap 34a, 34b toward the spread mooring chains. By fitting the floating storage vessel 10 with extension sections 15a, 15b one may conveniently provide suitable safety gaps in the terminal tailored to specific project requirements and size of the cargo vessels 20, also with due account taken of likely met-ocean conditions.
(15) Still referring to
(16) In use, fluid cargo in the form of liquefied gas is offloaded from the cargo vessel 20 to the floating storage vessel 30 through first tubing in the form of one or more aerial hoses 61 or other loading apparatus which connect between the mid-ship manifolds 12, 22 of the floating storage vessel 10 and cargo vessel 20. The offloaded liquefied gas is stored in the floating storage vessel 30. The liquefied gas is conveyed through second tubing in the form of one or more aerial hoses to the platform 50 and is regasified by the regasification facility. The regasified gas is then transmitted away from the platform 50, typically to shore via a gas pipeline 63.
(17) In variants in which the processing facility on the platform 50 is a liquefaction facility, in use, gas is transmitted typically from shore via gas pipeline 63 to the platform. The gas is liquefied by the liquefaction facility and then conveyed through the second tubing hoses 62 to the floating storage vessel 10 where the liquefied gas is stored. The liquefied gas is loaded onto the cargo vessel 20 from the floating storage vessel 10 through the first tubing hoses 61.
(18) Turning now to
(19) In
(20) The box structure 80 is configured to fit the bow end 73 at a connecting location 73h on the bow end where it is welded to the bow end 73 of the hull 71. The one or more tanks 13 are provided in the hull 71 for storing fluid offloaded from or to be loaded onto the cargo vessel in use. The box structure 80 extends longitudinally away from the connecting location 73h. The box structure 80 may comprise a prismatic structure in other examples.
(21) At an upper part of the hull 71, the hull has a hull deck 79 comprising walkways and/or areas for personnel or crew access. Other decks (not shown) may be provided as part of the superstructure upon the hull. The hull deck 79 may be equipped with handling equipment to be operated, accessed, and/or inspected by personnel onboard the vessel, the equipment including for example lifting and handling equipment, or mooring devices for facilitating in mooring the cargo vessel 20 alongside. Personnel standing on the hull deck 79 may also access the mid-ship manifold 12 for facilitating connection of one or more fluid cargo transfer hoses 61 for loading or offloading fluid cargo into the holds or tanks 13 in the hull. The hull 71 in an intermediate section between the stern and bow ends defines a maximum width of the hull 71. The width of the hull 71 from certain locations along the hull 71 typically tapers away from the full width of the intermediate section toward the bow end 73 and toward the stern end respectively.
(22) The box structure 80 of the extension section 15a preferably comprises welded steel plates. The box structure 80 preferably has a height H less than the topsides height F of the hull 71 above the waterline 36, and preferably has a width less than the maximum width of the hull at the intermediate section, e.g. typically less than half the maximum width or less than a quarter of the maximum width of the hull at the intermediate section.
(23) The box structure 80 extends from a first end 81 to a second end 82. The first end 81 of the box structure 80 is located against and welded to the bow end 73 at the connection location 73h to connect the box structure 80 to the hull 71. The box structure 80 is elongate and extends longitudinally from the first end 81 at the connection location 73h toward the second end 82 in the longitudinal direction of the hull. Thus, the box structure 80 provides a longitudinal extension from the hull at the bow end. The structure protrudes longitudinally toward the second end 82 from an outer surface of the bow end at the connection location 73h, the second end 82 distally disposed with respect to the first end 81.
(24) The box structure 80 is further arranged to be welded to the connection location 73h on the bow end 73 at or near the top of the hull so that the box structure 80 is aligned with the hull deck 79. In this way, the hull 71 can support the box structure 80 with the coupling means 86a on the box structure for the spread mooring lines 16a located high up upon the hull yet benefit from the inherent strength of the hull 71 at or near the deck level of the hull, through the welding of the first end 81 to the bow end 73, so that necessary mooring loads can be handled.
(25) The extension section 15a also includes an extension section deck 89 on an upper portion of the box structure 80. When the extension section 15a is affixed to the hull 71 as seen in
(26) In the example of
(27) The extension section 15a comprises typically a prefabricated welded steel plate structure 80 that can be fabricated at a yard in due time before the tanker ship arrives the yard. The coupling means 86a for the mooring chains will typically be installed on the prefabricated extension section 15a before the ship arrives so everything is ready when the ship arrives the yard. In this way, the extension section 15a can be “added onto” the ship, i.e. welded on, quickly and the ship can stay at a limited time at the yard.
(28) In practice, the box structure 80 or other welded plate structure for example has a height of 5 m or more. The length of the extension section 15a may be determined from project to project depending upon the size of the cargo vessels 20 planned to be moored in a side-by-side mooring arrangement to the floating storage vessel 10.
(29) The coupling means 86a are fitted to the extension section 15a for coupling the mooring lines 16a, typically in the form of mooring chains, to the extension section 15a. There are typically 6-10 chains per extension section where each chain can be connected to an individual coupling means 16a, although six mooring lines per extension section are illustrated in the drawings. The coupling means 86a in certain examples are of “adjustable type”, so that after the chain has been pulled in, chain tension can be adjusted by pulling in more of the chain or slackening out the chain by use of the adjustable coupling means. The adjustable means is for example used after the vessel 10 has been in operation for some time to re-tension the mooring lines 16a, if needed. In some examples, the coupling means 86a is equipped with a load monitoring device to monitor the mooring chain loads continuously during operation. This can ensure that the mooring tension is evenly distributed between all the chains. Load monitoring can be particularly beneficial during operations in inclement weather to make sure that the mooring tension is within acceptable level. In some examples, the coupling means 86a are of releasable type, that is the coupling means 86a have release mechanisms so that the mooring lines 16a can be released from the extension section 15a if the vessel 10 must leave location (e.g., during exceptionally bad weather). Such release mechanisms can be remotely operated for instance by hydraulics or other means. The coupling means 86a are supported on the deck 89 of the extension section 15a, typically at or near the extension deck level. The coupling means 86a on the extension section 15a are sufficient and carry the coupling means necessary for the bow end coupling of the spread-mooring lines 16a to the vessel without requiring any coupling of mooring lines 16a to the hull between the extension sections. The same applies correspondingly to the stern with use of the extension section 15b. In this way, the mooring area for the cargo vessel 20 can be defined alongside the floating storage vessel 10 between the extension sections 15a, 15b.
(30) The offshore terminal apparatus 201 of
(31) The floating storage vessel can in any example described herein be a floating storage unit (FSU) and in particular examples the floating storage unit may be a floating storage and regasification unit (FSRU).