An offshore fluid transfer system

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

An offshore fluid transfer systemTechnical Field

[0001] The present invention relates to an offshore fluid transfer system, comprising a floating vessel, a subsea flowline, a free-standing pipeline interface station, a flexible pipeline, a balcony and a submerse-restraining means.Background

[0002] As the world moves towards the use of cleaner and greener energy sources, there is an increased need for transportation of liquefied gases such as CO2, chemical gases, LNG or LPG. Typically, these products will be transported on large seagoing vessels. This form of transportation requires the establishment of import and export terminals to transfer the product on- or offshore.

[0003] Such terminals are often located some distance from shore in order to accommodate the transportation vessels. Previously, these terminals have required extensive infrastructure leading to long lead times and heavy expenditure before delivery of the products is possible. With the ever increasing demand for cleaner energy, it has therefore been necessary to find solutions that are more cost- effective and quicker to install.

[0004] In recent years, alternative solutions to the traditional terminals have been proposed. Some such solutions propose the use of a balcony on the side of a vessel, from which a flexible pipeline is connected to an onshore terminal. See for example Norwegian patent no. 346025. These solutions require an emergency release coupling (ERG) which ensures that the flexible pipeline is protected from unintended drift-off of the vessel.

[0005] NO'025 aims to protect the decoupled end of the flexible pipeline from seabed interaction by providing a buoyant element around the decoupled end. However, this leaves the decoupled end of the flexible pipeline at the mercy of the elements as it floats in the waterline.

[0006] The invention aims to improve, mitigate or significantly alleviate upon the shortcomings of the prior art.Summary of the Invention

[0007] In a first aspect of the invention, the offshore fluid transfer system comprises: a floating vessel comprising a fluid manifold system; a subsea flowline, fluidly connected to a pipeline end terminal at a first end of the subsea flowline; a pipeline interface station, wherein a supporting structure of the pipeline interface station is free-standing in a body of water, and fluidly connected to a second end of the subsea flowline; a flexible pipeline, fluidly connected to the subsea flowline via the pipeline interface station at a first end of the flexible pipeline, and wherein a lower half of an emergency release coupling is arranged at a second end of the flexible pipeline; a balcony arranged on a side of the floating vessel, wherein the balcony comprises: interface piping fluidly connected to the fluid manifold system at a second end of the interface piping, and fluidly connectable to the second end of the flexible pipeline at a first end of the interface piping, wherein an upper half of the emergency release coupling is arranged at the first end of the interface piping a submerse-restraining means arranged at the lower half (53) of the emergency release coupling (50).

[0008] Thus according to the first aspect of the invention, a system is provided where the risk of damage to the lower half of the emergency release coupling when decoupled from the interface piping, is significantly lowered. By providing a pipeline interface station, the invention facilitates a shorter flexible pipeline, thereby minimising the effect of waves, winds and currents on the flexible pipeline.Consequently, the cumulative force acting on the flexible pipeline will be smaller, reducing the chance of erratic or large uncontrolled movement of the second end ofthe flexible pipeline and thus the bottom half of the emergency release coupling in a decoupled state.

[0009] Additionally, the entire length of the flexible pipeline will experience less environmental forces, thereby minimising risk of high tension loads along the length of the pipeline and high loads acting on the first end of the flexible pipeline both when the second end is coupled and when it is decoupled.

[0010] Decoupling can be a sensitive operation. As the second end of the flexible pipeline is released from the balcony by means of the emergency release coupling, it is undesirable for the lower half of the emergency release coupling to impact other structures. For example, currents, winds and waves acting on the flexible pipeline during decoupling will tend to make the fall of the second end of the flexible pipeline less controllable. Therefore the lower half of the emergency release coupling may be more prone to damage as the pipeline may undesirably come into contact with other structures. The present invention also alleviates this problem.[Oil] A particular advantage of the invention is minimising the forces acting on the submerse-restraining means arranged at the lower half of the emergency release coupling. Since the submerse-restraining means is configured to keep the lower half of the emergency release coupling above the waterline, the coupling may be exposed to environmental elements. By facilitating a shorter flexible pipeline extending to a free-standing pipeline interface station, this exposure is reduced whilst infrastructure costs are minimised in relation to traditional jetty terminals.

[0012] The submerse-restraining means may typically be connected to the lower half of the emergency release coupling with shackles arranged on said coupling. In certain embodiments, the submerse-restraining means may be arranged at the lower half of the emergency release coupling and connected to the second end of the flexible pipeline with a lug arranged on a flange at said end, or with a clamp to the flexible pipeline body. The submerse-restraining means may be a submerse- restraining assembly.

[0013] By free-standing, it is meant that the pipeline interface station does not comprise structural support connected to shore or the vessel. This is in contrast to for example a jetty, which cannot be considered free-standing in this context, because it by definition is connected with structural support to shore.

[0014] A floating vessel may typically be a ship, but may also comprise a tanker vessel and / or a floating storage unit and / or carrier vessel. A pipeline end terminal may typically be an onshore terminal and / or a connection to a gas distribution grid, but may be in the form of an offshore rig for ammonia production or an offshore well for carbon dioxide injection.

[0015] The flexible pipeline may typically be a transfer pipeline such as a duct, pipe, hose, flexible pipe, flexible hose or conduit suitable for the medium to be transferred. Preferably, the flexibility of the pipeline is configured to transfer a liquefied gas between a floating vessel and a bottom-fixed structure. Such flexible pipelines are known in the art and the skilled person will be familiar with the term flexible and its meaning within the context of the invention.

[0016] The subsea flowline may typically comprise a conduit made of steel or thermoplastic composite material. The subsea flowline may preferably comprise a different material than the flexible pipeline. The subsea flowline may be arranged on the sea floor, partially or fully buried beneath a protective mound or ditch. Because the subsea flowline is arranged to be statically placed, and not transfer products such as liquefied gas between a floating vessel and another unit, it does not require the same flexibility as the flexible pipeline. Instead, the subsea flowline may be made of relatively inexpensive piping material, well known to the skilled person as being differentiated from the material required for the flexible pipeline.

[0017] In embodiments of the invention, the submerse-restraining means may comprise a connection via a sling to a hang-off support structure arranged freestanding and external to the floating vessel. The hang-off support structure may comprise a hang-off arm arranged at the top of said structure, wherein the hang-off arm may extend above and in a cantilever configuration away from the hang-off support structure. At the end of the hang-off arm, the sling may be connected to the arm in a position above the body of water.

[0018] Preferably, a plurality of hang-off support structures may be interconnected with railings, walkways, gangways or similar structures. A hang-off arm may be arranged on a railing, walkway, gangways or similar between two hang-off support structures. Thus, the lower half of the emergency release coupling will be less likely to hit the hang-off support structure as it falls from the balcony.

[0019] The hang-off support structure may be a bottom-fixed pillar, a bottom- fixed truss structure or a moored floating structure. The bottom-fixed structures may additionally act as mooring structures for the floating vessel. For example, a series of bottom-fixed pillars may form a dolphin mooring for the floating vessel. A moored floating hang-off support structure may be moored by any conventional means such as lines extending to anchors on the seabed or through the use of dynamic positioning means.

[0020] The sling connection may be in the form of a harness, line or wire connected to hooks, shackles or similar devices on the lower half of the emergency release coupling. Alternatively and / or in addition, sling may be connected to the second end of the flexible pipeline with a lug arranged on a flange at said end, or with a clamp to the flexible pipeline body. The second end of the flexible pipeline may therefore hang-off the hang-off support structure when the lower half of the ERC is decoupled from the emergency release coupling. The sling connection and hang-off support structure may preferably be configured such that the second end of the flexible pipeline and lower half of the emergency release coupling falls in a controlled manner. By controlled manner, it is meant that the sling connection is configured to avoid that the second end of the flexible pipeline, and lower half of the emergency release coupling, falls against any structures that may damage the pipeline, and the lower half of the emergency release coupling, and preferably avoiding that the lower half of the emergency release coupling falls into a body of water. For example, this may be achieved by the positioning of the hang-off support structure and hang-off arm.

[0021] Thus, for embodiments with a hang-off support structure, the invention provides a lower risk of damage to the second end of the flexible pipeline and lower half of the emergency release coupling, since there will be less environmental forces acting on the flexible pipeline. For example, in a situation with strong winds or currents there will be less forces acting on the sling connection to the hang-off support structure, and thus the invention lessens the risk of the sling connection or other parts of the hang-off support structure failing due to high tension loads.

[0022] In certain embodiments of the invention, the submerse-restraining means may comprise a buoyancy element. The buoyancy element may be arranged around the second end of the flexible pipeline, and / or at the lower half of the emergency release coupling. The buoyancy element may comprise enough buoyant material to counteract the weight of the second end of the flexible pipeline andlower half of the emergency release coupling, thereby keeping the lower half of the emergency release coupling afloat after having decoupled and fallen to the water. It will be understood that the amount of buoyant material may be enough to keep lower half of the emergency release coupling afloat and preferably above the waterline, although the lower half of the emergency release coupling may be momentarily submerged after decoupling when it has fallen and hits the water at some speed. The buoyancy element may also serve as mechanical protection for the lower half of the emergency release coupling, since it may dampen impact from colliding structures.

[0023] Thus, for embodiments where the submerse-restraining means comprises a buoyancy element, the invention facilitates a lower risk of damage due to widespread movement of the second end of the pipeline and lower half of the emergency release coupling in the water surface. The second end of the flexible pipeline will have a radius of movement limited by its length and distance to the pipeline interface station, instead of a prior art solution where the length extends to the shore. Since the length of the flexible pipeline may be shorter, the sum of environmental forces are lower and the second end of the flexible pipeline and lower half of the emergency release coupling will be less prone to rapid and uncontrolled movement potentially colliding and being damaged by contact with external structures. The invention will for similar reasons also facilitate retrieval of the second end of the flexible pipeline and lower half of the emergency release coupling in embodiments where it comprise a buoyancy element.

[0024] In certain embodiments of the invention, the balcony may comprise a fallarrest system, connected at the lower half of the emergency release coupling .Alternatively and / or in addition, the fall-arrest system may be connected to the second end of the flexible pipeline with a lug arranged on a flange at said end, or with a clamp to the flexible pipeline body. A fall-arrest system may limit a fall velocity of the flexible pipeline when the emergency release coupling is activated. The fall-arrest system may also contribute to controlling the fall of the lower half of the emergency release coupling such that it does not come into contact with external structures, and / or is submerged into the body of water.

[0025] The fall-arrest system may comprise a harness connected at the lower half of the emergency release coupling, and a spool arranged on the balcony onto which the harness may be reeled. The spool may be arranged to reel out the harness at a certain speed, thereby braking a fall of the flexible pipeline, this may be achievedby friction means such as a calliper gripping a disc or by a drive unit holding the spool through exertion of hydraulic or electric force. Other means for braking the flexible pipeline may be provided such as pulleys or guiding units retarding the payout of the harness for example by friction means. The harness may comprise wires, cables or bands which are connected to harness connection points such as hooks or shackles at the lower half of the emergency release coupling.

[0026] In certain embodiments of the invention, the balcony may comprise a flexible pipeline retrieval system. The flexible pipeline retrieval system may be used to lift the second end of the flexible pipeline and the lower half of the emergency release coupling to the emergency release coupling, and comprise a lifting unit, such as a winch, arranged on the balcony, the hang-off support structure or on a deck of the floating vessel.

[0027] In certain embodiments of the invention, the fall-arrest system and the flexible pipeline retrieval system may be part of a dual-function fall-arrest and retrieval system. Thus, space on the balcony may be saved, providing a more compact and modular balcony unit that facilitates retrofitting and pre-assembly onto a vessel.

[0028] In certain embodiments of the invention, the dual-function fall-arrest and retrieval system may comprise a winch. In such embodiments, the winch may comprise a drive unit configured to slow down reeling after the emergency release coupling has been activated, and also configured to supply lifting power thereby lifting or lowering the second end of the flexible pipeline and the lower half of the ERC to recouple it or otherwise move it to a desired vertical position.

[0029] In certain embodiments of the invention, the length of the flexible pipeline is less than half the length of the subsea flowline. In a preferred embodiment, the length of the flexible pipeline is less than 20% the length of the subsea flowline. In yet more preferred embodiments, the length of the flexible pipeline is less than 10% the length of the subsea flowline.

[0030] In certain embodiments of the invention, the pipeline interface station may be a subsea pipeline end manifold or a riser tower.

[0031] In embodiments where the pipeline interface station may be a riser tower, the hang-off support structure may form part of the riser tower.

[0032] In certain embodiments, the pipeline interface station may comprise a flanged connection between the subsea flowline and the flexible pipeline. Alternatively, the pipeline interface station may comprise a spool piece with cross over pipes.

[0033] In certain embodiments, the pipeline interface station may comprise any of: valves, sensors, booster pumps, compressors, sample points, knock-out drums or other known processing units.

[0034] The riser tower may be a truss structure, monopile, jack-up type structure or other free-standing bottom-fixed structure known in the art. The riser tower may comprise a spool piece arranged extending from a first end at the seafloor to a second end at the top of the riser tower. The subsea flow line may terminate against a first end of a spool piece and the flexible pipeline may be fluidly connected to a second end of a spool piece at the top of the riser tower.

[0035] Alternatively the subsea flowline may be bent and / or guided to reach the top of the riser tower to connect to the first end of the spool piece above water.

[0036] In certain embodiments of the invention, the subsea flowline, pipeline interface station and balcony interface piping are arranged with two or more parallel conduits allowing one conduit to be isolated whilst the other conduit continues operating. Thus, the system will still retain 50% or more capacity even though one conduit is shutdown for maintenance or repair reasons.

[0037] In certain embodiments of the invention, the balcony may be modular and configured to be retrofitted on the floating vessel. The floating vessel may comprise at least one balcony foundation at a side of the vessel, where a balcony supporting structure may be fixed. At least one balcony supporting structure is arranged to extend from a deck of the vessel and out over a side of the ship's hull extending above a body of water. The balcony supporting structure may comprise a balcony beam, balcony tension rod and / combinations of such elements. The balcony may comprise a lattice structure.

[0038] The balcony foundation may comprise pre-arranged fixing means on a deck of the vessel, such as bolts, that are ready to engage with holes in the balcony supporting structure. Preferably at least two balcony foundations are arranged on the floating vessel. Preferably at least two balcony supporting structures, extendingfrom different points on the balcony are connected to each balcony foundation. The balcony foundations may be arranged to take up tension and / or compression, depending on their configuration.

[0039] The balcony may comprise at least two levels, preferably three, where at least one of the following components may be arranged on two separate levels; an emergency release coupling, comprising an upper half of the emergency release coupling, and an interface piping with a connection to a pipe spool. The levels of the balcony may also herein be referred to as decks of the balcony. The interface piping may extend over several levels of the balcony, extending from an emergency release coupling at one level, to the connection to a pipe spool at another level. Thus it may be seen that the footprint of the balcony remains minimal, as the various components are arranged vertically in relation to each other. This allows for easier pre-fabrication and installation of the balcony, such that it is modular and may be used for a variety of vessels.

[0040] Preferably, a fall-arrest and / or retrieval system may be arranged on a third level. In particular, the winch of a fall-arrest and / or retrieval system may be arranged on a third level, with a harness of the system extending through the levels to the lower half of the emergency release coupling when it is in a coupled state.

[0041] In certain embodiments of the invention, the modular balcony may comprise a local blow-down system. A local blow-down system may comprise valves arranged on the emergency release coupling configured to shut down fluid flow in response to a signal activating the emergency release coupling, but before the coupling disconnects the flexible pipeline from the interface piping. Thus the local blow-down system may comprise a pipeline extending from the cavity between the two shutdown valves in the emergency release coupling, enabling the trapped fluid to be ventilated before the flexible pipeline is released.

[0042] The emergency release coupling may comprise valves configured to shut down fluid flow, also in embodiments where there is no local blow-down system.

[0043] In certain embodiments of the invention, an emergency shutdown valve may be provided to further fluidly isolate the volume inside the subsea flowline from the environment in case of an emergency decoupling of the emergency release coupling. The emergency shutdown valve(s) may be arranged on thepipeline interface station and / or between the emergency release coupling and the second end of the flexible pipeline.

[0044] In certain embodiments of the invention, a positioning sensor may be arranged on the floating vessel configured to detect the position of the vessel. The positioning sensor may be signally connected to a processing unit, wherein the processing unit may be arranged on the vessel or the balcony. The processing unit may be configured to determine whether the floating vessel is drifting off, or will drift off from its moored position and thereby require an activation of the emergency release coupling. The processing unit may be signally connected to the emergency release coupling in order to activate a release of the coupling. The processing unit may be signally connected to the shutdown valves in order to activate the local blow-down system upon activation of the emergency release coupling. The processing unit may be signally connected to the fall-arrest system in order to activate a fall-arrest state upon activation of the emergency release coupling, although the fall-arrest system may preferably be passively activated.

[0045] The harness and its connection to the spool may be configured such that when the harness is fully reeled out from the spool it drops from the spool and into the body of water. Thus, when the floating vessel drifts off, the emergency release coupling is activated and the second end of the flexible pipeline is supported by the submerse-restraining means, the spool may fully reel out the spool.

[0046] In the following description, numerous specific details are introduced by way of example only to provide a thorough understanding of embodiments of the claimed system. One skilled in the relevant art, however, will recognize that these embodiments can be practiced without one or more of the specific details, or with other components, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the disclosed embodiments.Brief Description of the Figures

[0047] The following drawings are appended to facilitate the understanding of the invention. The drawings show embodiments of the invention, which will now be described by way of example only, where:

[0048] Fig. 1 is a schematic illustration of an exemplary embodiment of the invention where the pipeline interface station comprises a riser tower.

[0049] Fig. 2 is a schematic illustration of an exemplary embodiment of the invention where the pipeline interface station comprises subsea pipeline end manifold.

[0050] Fig. 3 is a schematic illustration of an exemplary embodiment of the invention where the pipeline interface station comprises subsea pipeline end manifold, and wherein the submerse-restraining means comprises a connection via a sling to a hang-off support structure.

[0051] Fig. 4 is a schematic illustration of an exemplary embodiment of the invention where the pipeline interface station comprises subsea pipeline end manifold, and wherein the submerse-restraining means comprises a buoyancy element

[0052] Fig. 5 is a schematic illustration of an exemplary embodiment of the invention, showing details of the balcony and the components arranged thereon.

[0053] Fig. 6 is a schematic illustration of an exemplary embodiment of the invention, where two parallel conduits are arranged in certain parts of the transfer system.Detailed Description of the Figures

[0054] In the following, general embodiments as well as particular exemplary embodiments of the invention will be described. References will be made to the accompanying drawings. It shall be noted, however, that the drawings are exemplary embodiments only, and that other features and embodiments may well be within the scope of the invention as claimed. Further, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality.

[0055] Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. Certain terms of art, notations, and other scientific terms or terminology may, however, be defined specifically as indicated below.

[0056] Fig. 1 illustrates an overview of the offshore fluid transfer system 10 according to one embodiment. In this embodiment, the flexible pipeline 30 is connected to a pipeline interface station 70 having a riser tower 72 as a supporting structure 71. As shown in the Figure, the flexible pipeline 30 extends from a balcony 22 arranged on a side of the floating vessel 20 across to the upper part of the riser tower 72. The riser tower 72 is shown as a free-standing structure in the body of water 1, it thus not connected to any supporting structure extending to the shoreline. At a lower end of the riser tower 72, a subsea flowline 60 is shown connected at a second end 63 and extending towards a pipeline end terminal 61. The pipeline end terminal has not been illustrated in Fig. 1.

[0057] The details of the submerse-restraining means 35 are not illustrated in Fig. 1, but in the illustrated embodiment it can for example comprise a buoyancy element 36 on the second end 31 of the flexible pipeline 30. Thus, there is no need for a hang-off system in this embodiment. When the emergency release coupling 50 is activated, the second end 31 of the flexible pipeline 30 and the lower half 53 of the emergency release coupling 50 descends towards and into the body of water 1. This activation is caused by the floating vessel 20 drifting off from a moored position. The buoyancy element 36 will keep the lower half 53 of the emergency release coupling 50 above the waterline after the preliminary fall into the body of water 1. The forces acting on the length of the flexible pipeline 30 will therefore be relatively limited, since the flexible pipeline 30 does not extend all the way to a pipeline end terminal 61 as in the prior art solutions. The weight of the flexible pipeline, the stiffness of the flexible pipeline and the buoyancy of the buoyancy element 36 will together ensure a catenary shape of the pipeline after decoupling. This will reduce the risk of damage on the flexible pipeline 30.

[0058] Furthermore, the second end 31 of the flexible pipeline 30 and the lower half 53 of the emergency release coupling 50 will be limited to moving in a radius surrounding the riser tower 72. Thus, retrieval of the second end 31 of the flexible pipeline 30 and lower half 53 of the emergency release coupling 50 will be facilitated since it can be found in a limited area and the force required to retrieve it will be more manageable compared to the prior art solutions. Furthermore, the lower half 53 of the emergency release coupling 50 does not come into contact with the sea floor, which could potentially cause damage to the coupling 53.

[0059] Turning to Fig. 2, another exemplary embodiment is illustrated where the pipeline interface station 70 comprises a subsea pipeline end manifold 73. Thus, theflexible pipeline 30 is shown extending from its second end 21 on a balcony 22 arranged on the side of the floating vessel 20 and down towards the subsea pipeline end manifold 73. The subsea pipeline end manifold 73 comprises a supporting structure 71, comprising a base on the sea floor 2. The base 71 is illustrated as a free-standing structure in the body of water 1. It can be seen that the supporting structure 71 does not have any extensions of its structure to the shoreline.

[0060] As described for Fig. 1, the submerse-restraining means 35 in Fig. 2 can for example be a buoyant element 36 arranged at the lower half 53 of the emergency release coupling 50. Although the subsea pipeline end manifold 73 is arranged on the sea floor 2, the same benefits will apply in terms of reduced potential damage to the flexible pipeline 30 and ease of retrieval. In the Figure, the flexible pipeline is exemplified with a catenary shape, but it will be understood that it may be arranged in different configurations where applicable, such as but not limited to lazy-S, steep-S, lazy-wave and so on.

[0061] Turning to Fig. 3, another exemplary embodiment is illustrated showing more details of the system 10 extending from a subsea pipeline end manifold 73 to the balcony 22 of a floating vessel 20. Furthermore, Fig. 3 illustrates the flexible pipeline 30 in two different states, coupled 30 and decoupled 30'.

[0062] A cross-section of a portion of a floating vessel 20 is shown in the body of water 1. The vessel 20 comprises a balcony 22 arranged at a side of the vessel 20, the balcony 22 extending out from a side of the vessel 20. Fig. 3 does not illustrate all the components or details of the balcony 22, but it will be understood that the emergency release coupling 50, interface piping 40, fall-arrest system 23 and flexible pipeline retrieval system 24 may all be arranged on the balcony 22. In particular, the components may all be arranged such that the majority of them are on the part of the balcony 22 extending past the side of the vessel 20 and over the body of water 1.

[0063] In particular, the emergency release coupling 50 is arranged on the part of the balcony 22 extending past the side of the vessel 20 such that the second end 31 of the flexible pipeline 30, when decoupled, will fall down towards the body of water 1. An embodiment of the balcony 22 and its components will be described in further detail with reference to Fig. 5.

[0064] The floating vessel 20 is supported against a spacer element 122 to a side of the vessel 20. The spacer element 122 forms part of a hang-off support structure 120 and ensures that the floating vessel 20 is kept at a distance to said structure 120. This distance ensures that when the emergency release coupling 50 is activated, the second end 31 of the flexible pipeline 30 and lower half 53 of the emergency release coupling 50 will fall towards the body of water 1 and is unlikely to come into contact with the vessel 20 or hang-off support structure 120 as it falls.

[0065] The hang-off support structure 120 is exemplified as a pillar construction, fixedly installed to the sea floor 2 and in the form of a free-standing structure, i.e. it does not have any physical supporting structures connecting it to the shore. Although not illustrated, there may be a plurality of pillar structures, interconnected by railings or other structures, in order to provide a plurality of intermittently arranged spacers to keep the vessel in a position with clearance to the hang-off support structure 120.

[0066] The hang-off support structure 120 is illustrated in Fig. 3 as comprising a hang-off support arm 123 at its top end. In this exemplary embodiment, the hang- off support arm 123 extends a distance above the top of the hang-off support structure 120 and provides clearance from the structure 120 to a sling 121 connected at the end of the hang-off support arm 123. In the embodiment of Fig.3, the submerse-restraining means 35 comprises these aforementioned components. The skilled person will recognise the difference of the submerse- restraining means 35 from this embodiment to that of Fig. 1 and Fig. 2, but it will be understood that a combination of the two are possible with a hang-off support structure 120 and a buoyancy element 36.

[0067] Although not disclosed from the angle shown in Fig. 3, the hang-off support arm 123 may be arranged on a beam, gangway, railing or truss structure interconnecting the top of at least two hang-off support structures 120. Thus, the second end 31 of the flexible pipeline 30' and lower half 53 of the emergency release coupling 50 will hang between two pillars 120 when it is in the decoupled state.

[0068] The sling 121 at the end of the hang-off support arm 123 is shown connected at the lower half 53 of the emergency release coupling 50in two different states, coupled 121 and decoupled 121'. In the coupled state, the sling 121 extends towards the lower half 53 of the emergency release coupling 50 when it is coupledtogether with the upper half 52 of the emergency release coupling 50 on the balcony 22. Upon activation of the emergency release coupling 50, the lower half 53 of the emergency release coupling 50 together with the second end 31 of the flexible pipeline 30 falls towards the body of water 1 but is prevented from being submerged by the restraining action of the sling 121'.

[0069] Fig. 3 also illustrates the lower half 53 of the emergency release coupling 50 in the decoupled state 31'. Here, the sling 121' is shown extending vertically downwards from the end of the hang-off support arm 123. The lower half 53 of the emergency release coupling 50 and the second end 31' of the flexible pipeline 30' is thus hanging between the balcony 22 and the body of water 1, and between two pillars of the hang-off support structure 120.

[0070] For the coupled and decoupled states of the flexible pipeline 30,30', Fig. 3 illustrates the different positions as it extends towards a subsea pipeline end manifold 73. The subsea flowline 60 is not shown in Fig. 3, but it will be understood that it extends from the subsea pipeline end manifold 73 towards a subsea pipeline end terminal 61. The subsea pipeline end manifold 73 is furthermore illustrated as being supported on a supporting structure 71 resting on the sea floor 2. Such supporting structures will be familiar to the skilled person.

[0071] Moving to the exemplary embodiment illustrated in Fig. 4, a similar overview of the system 10 is presented as in Fig. 3. However, the embodiment in Fig. 4 illustrates the submerse-restraining means 35 comprising a buoyancy element 36 at the lower half 53 of the emergency release coupling 50. Thus, it can be seen that the elements from the Fig. 3 embodiment relating to the hang-off support structure 120 and sling 121 are not present in Fig. 4. Otherwise, the same components, such as the balcony 22, subsea pipeline end manifold 73 and vessel 20 are illustrated in both these Figures and therefore reference is made to the description of these in Fig. 3.

[0072] The lower half 53 of the emergency release coupling 50 and the second end 31 of the flexible pipeline 30 is illustrated in two different states, coupled 30 and decoupled 30'. In the coupled state, the lower half 53 of the emergency release coupling 50is coupled to the upper half 52 of the emergency release coupling 50 located on the balcony 22. The buoyancy element 36 is arranged at the second end 31, for example extending around the pipeline 31 and at some distance along the length of the pipeline, just below the lower half 53 of the emergency releasecoupling 50such that the buoyancy element 36 does not interfere with the coupling. Upon activation of the emergency release coupling 50, the lower half 53 of the emergency release coupling 50 and the second end 31' of the flexible pipeline 30 falls into the body of water 1 below. The buoyancy element 36 ensures that the lower half 53 of the emergency release coupling 50 is submerged only for a brief period of time and does not come into contact with the sea floor 2. Furthermore, the buoyancy element is illustrated with a design such that it floats with the lower half of the ERC as the highest point. This is achieved by buoyancy element shape and / or weight distribution to ensure desired floater stability.

[0073] After the preliminary impact with the body of water 1, the second end 31' of the flexible pipeline 30 and in particular, the lower half 53 of the emergency release coupling 50, are kept above the water line 3 by the buoyancy element. This is illustrated in Fig. 4.

[0074] Turning to Fig. 5, an exemplary embodiment of a balcony 22 is illustrated at the side of a floating vessel 20. The balcony 22 comprises three decks 26a, 26b, 26c each having a similar footprint and arranged at three vertically spaced apart levels. A balcony beam 27 is shown extending from the first lower deck 26a of the balcony 22 and to a first deck 28 of the floating vessel 20. The balcony beam 27 is shown reinforced with a triangular truss structure extending along the height of the first lower deck 26a of the balcony 22. On the first deck 28 of the floating vessel 20, the balcony beam 27 is connected to a balcony beam foundation 27a.The balcony beam foundation 27a is typically installed to the vessel 20 in a drydock as it may require reinforcement of the vessel 20 structure. Preferably, the balcony beam foundation 27a is arranged with means for providing rapid connection between the balcony beam 27 and balcony beam foundation 27a such as bolts that connect into bolt holes on the beam 27.

[0075] Towards the upper end of the balcony's 22 second deck 26b, Fig. 5 illustrates a balcony tension rod 29 extending towards the floating vessel 20. The tension rod 29 is exemplified as being connected to a tension rod foundation 29a on a side plating above the first deck 28. It will be understood that the tension rod foundation 29a may be arranged on any superstructure or other suitable structure above the first deck 28. The tension rod foundation 29a is typically installed during drydocking of the vessel 20, in order to fix it with the necessary reinforcements to the underlying structure on the vessel 20.

[0076] Together, the balcony tension rod 29 and balcony beam 27 support the balcony's 22 weight and moment, whilst allowing for rapid connection to the floating vessel 20. The construction of the balcony 22 can therefore be modular, allowing pre-fabrication with the necessary components before installation to the floating vessel 20 in diverse locations thereby avoiding costly downtime at drydock. Additional structures are illustrated allowing ease of access for personnel to the different decks 26, these can be seen arranged on the balcony 22 and from the floating vessel to the balcony, including stairs, protection- and handrails.

[0077] The exemplary embodiment of Fig. 5 furthermore illustrates three different components arranged mainly at each of the three decks 26a, 26b, 26c. On the third upper deck 26c, a fall-arrest system 23 comprising a winch 23a is illustrated. The winch 23a has a harness 23b extending down toward a decoupled lower half 53 of the emergency release coupling 50 and second end 31' of the flexible pipeline 30', shown hanging below the balcony 22. Thus, the winch 23a may ensure that the falling velocity of the lower half 53 of the emergency release coupling 50 and second end 31' of the flexible pipeline 30' is restrained upon activation of the emergency release coupling 50. The winch 23a may also function as a flexible pipeline retrieval system 24, being capable of reeling in the flexible pipeline 30' after it has decoupled in order to recouple the emergency release coupling 50.

[0078] On the first lower deck 26a of the balcony 22, the emergency release coupling 50 is illustrated in decoupled state. The emergency release coupling 50 has thus been activated in order to release the lower half 53 of the emergency release coupling 50 and second end 31' of the flexible pipeline 30. Hanging below the first lower deck 26a of the balcony 22, attached to the harness 23b of the fallarrest system 23, the second end 31' of the flexible pipeline 30' is shown with the lower half 53 of the emergency release coupling 50arranged at the very end of the second end 31'. In a coupled state, the lower half 53 of the emergency release coupling 50wil I engage with the upper half 52 of the emergency release coupling 50 ensuring a fluid tight connection.

[0079] The emergency release coupling 50 may comprise a hydraulically or mechanically activated solution. One solution, illustrated in the exemplary embodiment of Fig. 5 comprises hydraulically activated clamps 51 arranged to hold the lower half 53 of the emergency release coupling 50 and upper half 52 of the emergency release coupling 50 in a coupled state . Upon activation of the emergency release coupling 50, a hydraulic actuator is arranged to rotate a ringwhich acts on a hinge of the clamps 51 which releases the upper 52 and lower 53 halves from a coupled position. Other solutions known in the art include providing a mechanically activated collar as an emergency release coupling 50, which holds the lower half 53 to the upper half 52 of the emergency release coupling 50 together.

[0080] Interface piping 40 is shown extending from the emergency release coupling 50, where the first end 42 of the interface piping 40 fluidly connects to said coupling 50. The interface piping 40 extends up towards and through the second middle deck 26b of the balcony 22. At the second middle deck 26b, the interface piping 40 makes a junction and connects to a pipe spool 43 extending out towards the floating vessel 20and over the side of the balcony decks 26. The pipe spool 43 ends at a position above the first deck 28 of the vessel 20, where it will be connected to a fluid manifold system 21 of the vessel 20. Although not illustrated in the Figure, shut down and isolation valves may be arranged on the second middle deck 26b.

[0081] Thus, it can be seen in the embodiment of Fig. 5 that the footprint of the balcony 22 remains minimal, as the interface piping 40, emergency release coupling 50 and fall-arrest system 23 are all arranged vertically in relation to each other. This allows for easier pre-fabrication and installation of the balcony 22, such that it may be modular and may be used for a variety of vessels 20.

[0082] Turning to Fig. 6, a schematic overview of the offshore fluid transfer system 10 according to an exemplary embodiment is provided. Starting from the left of the figure, the pipeline end terminal 61 is shown with one conduit being split into two parallel conduits 11,12. Right after each split, the conduits 11,12 are illustrated each with a double block and bleed valve 13,14 for isolating the conduit. These two parallel conduits 11,12 are then connected to the first end 62 subsea flowline 60, where two conduits 11,12 continue until their connection at the second end 61 of the subsea flowline 60 to the pipeline interface station 70.

[0083] At the pipeline interface station 70, the two conduits 11,12 continue extending towards a first end 32 of the flexible pipeline 30. The flexible pipeline 30 extends the two conduits 11,12 from a first end 32 connected to the pipeline interface station 70 to a second end 31 where they are connected to the emergency release coupling50. The emergency release coupler 50 is connected to a first end 42 of the interface piping 40 which brings the two parallel conduits 11,12 back into a main conduit that connects at a second end 41 of the interface piping 40 to thevessel manifold system 21. Right before the conduits 11,12 are reunited, Fig. 6 illustrates each with a double block and bleed valve 13,14 for isolating each conduit together with the valves 13,14 on the left hand side of the Figure.

[0084] Although schematic, Fig. 6 illustrates that the length B of the subsea flowline 60 is significantly longer than the length A of the flexible pipeline. Typically, the flexible pipeline 30 may be in the range of 40-80 metres, whilst the subsea flowline 60 may be in the range of 400-4000 metres. By arranging the pipeline interface station 70 as a free-standing structure between the pipeline end terminal 61 and the emergency release coupling 50, a shorter length of the flexible pipeline can be achieved whilst avoiding potential risks to damaging the flexible pipeline 30. In particular when the second end 31' of the flexible pipeline 30' is in a decoupled state and reliant on the submerse-restraining means 35 to keep it from interacting with the sea floor 2. Yet the invention also avoids heavy expenditure and time spent on building infrastructure.In the preceding description, various aspects of the system 10 according to the invention have been described with reference to the illustrative embodiments. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the system and its workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the system, which are apparent to persons skilled in the art to which the disclosed subject matter pertains, are deemed to lie within the scope of the present invention.List of Reference Numbers

Claims

Claims1. An offshore fluid transfer system (10) comprising: a floating vessel (20) comprising a fluid manifold system (21); a subsea flowline (60), fluidly connected to a pipeline end terminal (61) at a first end (62) of the subsea flowline (60); a pipeline interface station (70), wherein a supporting structure (71) of the pipeline interface station (70) is free-standing in a body of water (1), and fluidly connected to a second end (63) of the subsea flowline (60); a flexible pipeline (30), fluidly connected to the subsea flowline (60) via the pipeline interface station (70) at a first end (32) of the flexible pipeline (30), and wherein a lower half (53) of an emergency release coupling (50) is arranged at a second end (31) of the flexible pipeline (30); a balcony (22) arranged on a side of the floating vessel (20), wherein the balcony (22) comprises: interface piping (40) fluidly connected to the fluid manifold system (21) at a second end (41) of the interface piping (40), and fluidly connectable to the second end (31) of the flexible pipeline (30) at a first end (42) of the interface piping (40), wherein an upper half (52) of the emergency release coupling (50) is arranged at the first end (42) of the interface piping (40), a submerse-restraining means (35) arranged at the lower half (53) of the emergency release coupling (50). The offshore fluid transfer system (10) according to claim 1, wherein the submerse-restraining means (35) comprises a connection via a sling (121) to a hang-off support structure (120) arranged free-standing and external to the floating vessel (10).claims, wherein the submerse-restraining means (35) comprises a buoyancy element (36).

3. The offshore fluid transfer system (10) according to any of the preceding claims, wherein the balcony (22) comprises a fall-arrest system (23), connected at the lower half (53) of the emergency release coupling (50).

4. The offshore fluid transfer system (10) according to any of the preceding claims, wherein the balcony (22) comprises a flexible pipeline retrieval system (24).

5. The offshore fluid transfer system (10) according to claims 4 and 5, wherein the fall-arrest system (23) and the flexible pipeline retrieval system (24) are part of a dual-function fall-arrest and retrieval system (23,24).

6. The offshore fluid transfer system (10) according to claim 6, wherein the dual-function fall-arrest and retrieval system (23,24) comprises a winch (25).

7. The offshore fluid transfer system (10) according to any of the preceding claims, wherein the length (A) of the flexible pipeline (30) is less than half the length (B) of the subsea flowline (60).

8. The offshore fluid transfer system (10) according to any of the preceding claims, wherein the pipeline interface station (70) comprises a subsea pipeline end manifold or a riser tower.

9. The offshore fluid transfer system (10) according to any of the preceding claims, wherein the subsea flowline (60), pipeline interface station (70) and balcony interface piping (40) are arranged with two parallel conduits (11,12) allowing one conduit (11,12) to be isolated whilst the other conduit (11,12) continues operating.