1. Technical Field
Embodiments of the invention relate generally to offshore systems and methods in liquefied gas production, storage and offloading, and more particularly to limiting structural damage to an affected offshore platform and preventing damage spread from the affected offshore platform to another platform during accidents or emergency conditions, e.g. collision, fire or explosion.
2. Description of Related Art
There has been considerable publicity over accidents at offshore oil or gas platforms. Collision of a vessel with an offshore platform potentially results in damage to structural integrity of the platform and economic losses due to high capital investments in construction of the offshore platform. Fires and explosion blowouts threaten personnel safety and environment well-being. Due to the volume of flammable materials on offshore platforms, fires on offshore platforms are known to burn for long periods of time resulting in severe and possibly irreparable damage to the offshore platforms. Even if fires may be eventually put out, the potential pollution due to oil spills may result in an environmental disaster.
In view of the above and other problems, limiting structural damage to an affected offshore platform and preventing damage spread from the affected offshore platform to another platform are highly desirable.
Embodiments of the invention relate to systems and methods for limiting structural damage to an affected offshore platform and preventing damage spread from the affected offshore platform to another platform during accidents or emergency conditions, e.g. a fire or an explosion. According to one embodiment of the invention, an offshore platform arrangement may include a mobile storage platform having a storage facility for storing a hydrocarbon fluid, e.g. liquefied natural gas (LNG), a mobile offloading platform disposed at a first clearance distance from the mobile storage platform and having an offloading system for facilitating transfer of hydrocarbon fluid from the storage facility to a carrier vessel which is positioned at the mobile offloading platform; and at least a first pipe connecting the mobile storage platform to the mobile offloading platform for allowing fluid communication of hydrocarbon fluid therebetween, wherein the first pipe is adapted to cease fluid communication of hydrocarbon fluid between the mobile storage platform and the mobile offloading platform.
According to another embodiment of the invention, the offshore platform arrangement may further include a mobile offshore production unit (MOPU) which is disposed at a second clearance distance from the mobile storage platform; and at least a second pipe connecting the mobile offshore production unit to the mobile storage platform for allowing fluid communication of hydrocarbon fluid therebetween, wherein the second pipe is adapted to cease fluid communication of hydrocarbon fluid between the mobile offshore production unit and the mobile storage platform.
According to another embodiment of the invention, an offloading system for facilitating hydrocarbon fluid transfer between a mobile platform and a carrier vessel may include a transfer skid and a lifting system operable to move the transfer skid from the mobile platform to a carrier vessel for installation thereon to provide fluid communication between the mobile platform and the carrier vessel. The lifting system is also operable to return the transfer skid to the mobile offloading platform after an offloading operation. The transfer skid may include a skid frame; a plurality of pipes which are rigidly attached to the skid frame, a plurality of jack screw mechanisms for independently adjusting the pipes relative to the skid frame, each of the pipes having a first end and a second distal end; a coupler provided at the first end of the each of the pipes to connect to the carrier vessel after installing the transfer skid on the carrier vessel; an emergency release coupling provided at the second end of the each of the pipes; and a transfer hose connected between the emergency release coupling and the mobile offloading platform. The lifting system may include an extendable lifting arm; a spreader frame attachment which includes at least a lifting device to support the transfer skid, wherein the spreader frame attachment is rotatably coupled to the lifting arm to allow angular adjustment of the transfer skid in a horizontal plane.
Embodiments of the invention are disclosed hereinafter with reference to the drawings, in which:
In the following description, numerous specific details are set forth in order to provide a thorough understanding of various illustrative embodiments of the invention. It will be understood, however, to one skilled in the art, that embodiments of the invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure pertinent aspects of embodiments being described. In the drawings, like reference numerals refer to same or similar functionalities or features throughout the several views.
Reference is made to
The MOPU 40 may include a production facility e.g. a liquefaction facility for liquefying gaseous hydrocarbon fluid such as natural gas. The MOPU 40 may be connected by pipelines 42 to at least one oil and/or gas well which supplies the gaseous hydrocarbon fluid and other hydrocarbon products to the MOPU 40. The MOPU 40 may include other facilities, e.g. accommodation facility 44 for personnel.
The mobile storage platform 30 is spaced at a clearance distance from the MOPU 40. The mobile storage platform 30 may include storage tanks for storing hydrocarbon fluid, e.g. liquefied natural gas (LNG), produced from the MOPU 40. One or more pipes 32 connect the MOPU 40 to the mobile storage platform 30 to facilitate transfer of hydrocarbon fluid from the MOPU 40 to the mobile storage platform 30.
The mobile offloading platform 10 is spaced at a clearance distance from the mobile storage platform 30. The mobile offloading platform 10 may include an offloading system as described in subsequent paragraphs and
As illustrated, the MOPU 40, mobile storage platform 30 and mobile offloading platform 10 are separated and spaced apart from one another. However, the various platforms may be fluidly connected by a piping bridge or pipes to allow transfer of hydrocarbon fluid from one platform to another. Particularly, at least a first pipe 32 connecting between the MOPU 40 and mobile storage platform 30 allows hydrocarbon fluid to be transferred from the MOPU 40 to the mobile storage platform 30 to be stored. Further, at least a second pipe 12 connecting between the mobile storage platform 30 and mobile offloading platform 10 allows hydrocarbon fluid to be transferred out from storage to be offloaded onto a carrier vessel 20.
The piping bridges or pipes allow fluid communication between each of the MOPU 40, mobile storage platform 30 and mobile offloading platform 10 to be ceased or blocked as and when required. Particularly, the pipes 12, 32 may be provided with block valves or emergency shut-down valves to cease fluid communication between the platforms 10, 30, 40 during an accident or an emergency condition, e.g. collision, fire or explosion. For example, block or shut-down valves may be provided at each end of each pipe and adapted to block fluid flow in the pipes 12, 32 as and when required. A substantial portion of the pipes may be located above the sea level.
Although
Also, although
As safety and space efficiency are of paramount concern in the offshore industry, the arrangements of
(1) Arrangement of production, storage and offloading facilities on separate platforms increases safety as compared to combining these facilities on a single platform. Hydrocarbon fluid communication between various platforms may be quickly blocked during emergency conditions by shutting down piping bridges to cease hydrocarbon fluid flow between the platforms. This way, if a collision occurs which may break the piping bridges, the risk of a hydrocarbon fluid spill is minimized once hydrocarbon fluid flow is blocked between platforms. Also, the risk of a fire or explosion spread is also minimized with the blockage of hydrocarbon fluid flow between platforms.
(2) Providing a mobile offloading platform as a separate platform from production and storage facilities also serves as a barrier to protect the production and storage facilities from collision risk by a carrier vessel. Since a carrier vessel is positioned at the mobile offloading platform, the potential risk of the carrier vessel colliding with the mobile offloading platform is significantly higher than with the production or storage platforms which are located further and separated from the mobile offloading platform. Hence, if a collision does occur, the damage to the mobile offloading platform results in much lower economic losses than if a collision occurs at a platform which houses production, storage and offloading facilities.
(3) As offshore platforms, e.g. MOPU, are fixed bodies which are not affected by wave motion, onshore technology and process equipment for production and storage may be easily adapted.
(4) The use of mobile platforms allows for relocation of the production and storage facilities without the need for expensive installation and uninstallation of fixed offshore platforms. If the production capacity of an oil or gas field needs to be increased, mobile production and storage platforms may be installed more quickly as compared to employing fixed offshore platforms. Hence, production, storage and offloading facilities can be added over a large offshore area at lower capital investments. Separately, if an oil or gas field approaches depletion, the mobile platforms may be more easily redeployed to other locations.
Reference is now made to
The pipes 204 may be rigidly attached to the skid frame 202 to prevent load unbalance and swaying movements due to wind. However, jack screws may be provided at each pipe 204 to allow independent adjustment of each pipe 204 relative to the skid frame 202 in one or more directions, e.g. x, y and z directions (see
The ERC 216 may be formed of a pair of mating parts or connectors (hereinafter ERC1216a and ERC2216b respectively) which are normally securely engaged to each other when the transfer skid 200 is disposed in a parked position and during offloading operation. The mating parts may be activated to disconnect from each other within a predetermined time during an emergency release operation. ERC1216a connects to a transfer or flexible hose 250 which is to connect, directly or via other connectors or pipes 204, to a mobile offloading platform 10. ERC2216b is interposed or connected between ERC1216a and the pipe 204, directly or indirectly through a swivel 215. A slack ERC hoist sling 222 attaches each ERC1216a to a common spreader beam 210.
At two ends of the skid frame 202, shock absorbers or hydraulic dampeners 206 and guide funnels 208 may be provided. The shock absorbers 206 are constructed and arranged to dampen impact on the transfer skid 200 upon landing of the guide funnels 208 during installation of the transfer skid 200 on a carrier vessel. The guide funnels 208 are constructed and arranged to guide the transfer skid 200, in cooperation with guide wires 220, to a desired position during installation.
The skid frame 202 may have opposed sides which are supported by lifting devices or winches which may be capable of exerting independent control. Particularly, one side of the skid frame 202, which is proximate to the QC/DCs 212, may be supported by hoist wires 211a which are in turn supported by a first lifting device 430 (see
Quick release connectors may be provided at the hoist wires 211a, 211b to allow disconnection of the transfer skid 200 from the spreader beam 210 and lifting devices.
As would be appreciated from the above, the functions of the transfer skid 200 include, but are not limited to, providing a connection interface for hydrocarbon fluid transfer between two bodies 10, 20 and allowing simultaneous transfer of multiple transfer hoses 250 with a single lift.
Reference is now made to
The mobile offloading platform 10, as illustrated, has at least a deck supported by jack-up legs which are jacked down or installed into the sea floor. An extendable structure, e.g. a cantilever 602 is provided on the deck of the mobile offloading platform 10. The cantilever 602 is arranged to be movable relative to the deck such as by skidding movements. The cantilever 602 may be arranged to move along one or more linear directions (e.g. x and y directions) in a horizontal plane (e.g. over a deck of the mobile offloading platform), or in a pivotal or rotational direction (e.g. pivot about one end of the cantilever 602) in a horizontal plane, or both. The cantilever 602 is arranged to move between a fully retracted position and a fully extended position and various intermediate positions therebetween. In a retracted position, the cantilever 602 may be largely disposed over the deck. In an extended position, the cantilever 602 projects outward from the deck and over the sea. This way, an adjustable horizontal clearance distance from the edge of the deck is created. This outward projection from the deck and over the sea, due to the extended cantilever 602, creates an adjustable horizontal clearance distance from the edge of the deck and jack-up legs to allow safe clearance distance conditions between the mobile offloading platform 10 and a carrier vessel 20 to prevent collision. Further, since the telescopic crane arm of the lifting system 400 is extendable, the crane arm is capable of creating an additional adjustable horizontal clearance distance from the edge of the deck and jack-up legs to allow safe clearance distance conditions between the mobile offloading platform 10 and a carrier vessel 20.
The lifting system 400 as described with reference to
The pipe deck 500 may be installed at a deck level of the carrier vessel 20 so that the pipe deck 500 is accessible to personnel without having to operate at heights.
A sequence for connecting a transfer skid 200 to a carrier vessel 20 in preparation for offloading operation is described with reference to
The sequence proceeds to move or load the transfer skid 200 onto the carrier vessel 20. The lifting system 400 lifts the transfer skid 200 and the spreader beam 210 from the cantilever 602 (see
After the transfer skid 200 is appropriately positioned as desired, guide wires 220, which pass through funnels 208 of the transfer skid 200, may be reeled out from guide winches 426 and connected to guide posts 506 on the carrier vessel 20 (see
The transfer skid 200 is then landed onto the carrier vessel 20. During landing, funnels 208 of the transfer skid 200 may collide with the deck of the carrier vessel 20 (see
At this stage, the hoist wires 211 a, 211 b supporting the transfer skid 200 may be disconnected from the lifting system 400 (see
Although the transfer skid 200 is landed onto the carrier vessel 20, there may exist gaps between the QCDCs 212 of the transfer skid 200 and the flanges of the flexible expansion joint 504. Adjustments to the alignment of the QCDCs 212 to engage with the flanges of the flexible expansion joints 504 may be performed by jack screw mechanisms provided in the transfer skid 200. Particularly, jack screw mechanism of each pipe 204 of the transfer skid 200 may be controlled to move the pipe 204 in vertical, horizontal and/or transverse directions. Thereafter, fine adjustments to the alignment of the QCDCs 212 to engage with the flanges of the flexible expansion joints 504 may be compensated by the flexible expansion joints 504 provided at the pipe extensions (see
At this stage, the transfer skid 200 is installed at the carrier vessel 20 and is ready to commence an offloading operation. The QCDCs 212 are disposed inboard the carrier vessel 20, e.g. above the main deck of the carrier vessel 20, while the ERCs 216 are disposed outboard of the carrier vessel 20, e.g. exterior of the carrier vessel 20 and over the sea. This is possible as each QCDC 212 is spaced apart from an ERC 216 by a pipe 204 interposed or connected therebetween.
Before commencing an offloading operation, the lifting system 400 may retract and the ERC hoist slings 222 connected to the spreader beam 210 may be allowed to slack (see
After the offloading operation is completed, various checks and procedures may take place to ensure that the hydrocarbon fluid transfer is ceased and it is safe to disconnect the transfer skid 200. The lifting system 400 may be deployed to connect to the transfer skid 200 in preparation to return the transfer skid 200 to the offshore platform 10 after the transfer skid 200 is disconnected from the carrier vessel 20. In one embodiment where the ERCs 216 has a dual function of a double block valve, after transfer pumps are stopped, the valves in the ERCs 216 may be closed and hydrocarbon fluid in the pipes 204 of the transfer skid 200 may be drained and purged towards the carrier vessel 20. After purging, the transfer skid 200 may be disconnected from the pipe deck 500. The transfer skid 200, supported by the lifting system 400, may be lifted away from the carrier vessel 20 and the carrier vessel 20 may then move off as and when required without waiting for hydrocarbon fluid remaining in the transfer hoses 250 to boil off and to be purged as required in conventional systems. Embodiments of the invention thus allow faster disconnection of the transfer skid 200 after an offloading operation is completed, and without waiting for hydrocarbon fluid in the transfer hoses 250 to boil off and to be purged before disconnecting the transfer skid 200 from the carrier vessel 20. In certain embodiments, the separate double block valves may be provided in the pipes 204 and may also be similarly utilized as described above.
The transfer skid 200, supported by the lifting system 400, is lifted to allow hydrocarbon fluid drain by gravity towards the mobile offloading platform 10 (see
During an offloading operation, an emergency situation may occur which requires the transfer hoses 250 to separate or disconnect from the carrier vessel 20 safely and quickly. Examples of an emergency situation include, but are not limited to, extreme weather, environmental conditions, failure of dynamic positioning system, failure of mooring lines, which cause the carrier vessel 20 to deviate from the desired position. Other examples include fire breakouts and explosion.
Once the operating conditions are ascertained to have exceeded certain safe operating threshold, an Emergency Shut Down situation may be triggered in which transfer pumps are stopped and an Emergency Release System may be subsequently triggered to disconnect the transfer hoses 250 from the transfer skid 200 installed at the carrier vessel 20. Particularly, the ERCs 216 are activated to detach the connector parts 216a, 216b forming the ERC 216 (see
However, the fall of the detached part 216a of the ERC 216 may be limited by the second lifting device 440 of the lifting system 400, which supports the detached part 216a of the ERC. Particularly, as illustrated in
During the emergency release of the ERCs 216, the transfer skid 200, including pipes 204, QCDCs 212 and the other part 216b of the ERCs 216 which remains coupled to the QCDCs 212, will remain installed at the carrier vessel 20 until the emergency situation is brought under control or is resolved. Subsequently, a separate operation may be initiated to uninstall or disconnect the transfer skid 200 from the carrier vessel 20 and move or return the transfer skid 200 to the mobile offloading platform 10. Suitable procedures may take place to re-assemble the detached ERC parts 216a, 216b to prepare the transfer skid 200 for the next offloading operation.
Embodiments of the invention achieve various advantages such as but not limited to the following:
(1) During an offloading operation, the ERCs would be disposed outboard. If emergency release is required, the disconnected ERCs would free fall towards the sea and therefore would not result in hydrocarbon spill on the carrier vessel or collision with the carrier vessel.
(2) Although the transfer skid allow simultaneous transport of the multiple pipes and transfer hoses from a mobile offloading platform to a carrier vessel, each pipe of the transfer skid may be independently positioned and connected to the flanges of flexible expansion joints on the carrier vessel. This improves mating connection even if there is misalignment which may be due to various reasons, e.g. a deck of the carrier vessel supporting the pipe deck is uneven or tilted.
(3) The transfer skid supports multiple transfer devices so that transport of the transfer hoses together with the QCDCs and ERCs between two bodies is simultaneous and therefore efficient.
Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention. Furthermore, certain terminology has been used for the purposes of descriptive clarity, and not to limit the disclosed embodiments of the invention. The embodiments and features described above should be considered exemplary, with the invention being defined by the appended claims.
Number | Date | Country | |
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61451710 | Mar 2011 | US |