SUPPORT VESSEL FOR ASSISTING THE LOADING OF FLUIDS HYDROCARBON CARGOES ONTO CARRIERS AND ASSOCIATED SYSTEMS AND METHODS - Patent application

Abstract

A system, method, and support vessel for use in the system are described. The system, in various embodiments, may include a carrier vessel for transporting a fluid hydrocarbon cargo across an ocean, the hydrocarbon cargo being loaded into at least one cargo tank of the vessel, the support vessel, a VOC capture means on board the support vessel for capturing volatile organic compounds (VOCs), the VOCs coming from the cargo tanks, in use, upon loading of the cargo tanks, and at least one hose extending between the carrier vessel and the support vessel for transferring gases including volatile organic compounds (VOCs) from the cargo tanks of the carrier vessel to the VOC capture means on board the support vessel.

Description

[Technical field]

[0001] The present invention relates to marine cargo handling operations, and in particular to the loading of fluid hydrocarbon cargoes onto carriers, for example the loading of crude oil onto oil tankers, and the associated handling of VOC gases. [Background technology]

[0002] Produced hydrocarbon fluids, such as crude oil or other fluid hydrocarbon cargoes, are often transported across the ocean in tanker ships, which are often large capacity carriers intended to transport liquid products long distances.

[0003] To load a fluid cargo onto a tanker ship, a hose is connected to the ship and the fluid cargo is pumped through the hose into the ship's tanks.

[0004] Typically, when crude oil is filled into the tanks of a carrier, gases including volatile organic compounds (VOCs) are released from the oil, e.g., VOC vapors are released from the crude oil due to the prevailing temperature and pressure conditions. VOC gases are often also present in residual amounts in the atmosphere of an "empty" tank. The VOC gases are transferred out of the tank during filling. Traditionally, the VOC gases escape and are released into the Earth's atmosphere.

[0005] The release of VOC gases into the Earth's atmosphere is problematic in that it can cause environmental damage. In some areas, such as the Norwegian Continental Shelf (NCS), conditions have been issued that prohibit the release of VOC gases. The existing solution to this for tankers transporting crude oil in the North Sea is currently to fit the tanker with a VOC treatment plant, where the treatment plant captures the gas and stores components of the gas as liquids that can then be discharged, thereby avoiding the gas being released into the atmosphere. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO 98 / 33026 [Patent Document 2] U.S. Patent No. 6,412,433 Summary of the Invention [Problem to be solved by the invention]

[0007] However, installing a suitable VOC treatment plant can be technically complex and expensive. The inventors have noted that existing solutions can be inconvenient, inefficient and time consuming to scale up and meet the demands for VOC gas treatment for the global tanker fleet. Solutions are needed that can better address these issues.

[0008] Otherwise, at least one object of the present invention is to obviate or mitigate one or more disadvantages of the prior art solutions. [Means for solving the problem]

[0009] According to a first aspect of the invention there is provided a system comprising a carrier vessel for carrying a fluid hydrocarbon cargo across the sea, the hydrocarbon cargo being loaded into at least one cargo tank of the vessel, a support vessel, VOC recovery means on board the support vessel for recovering volatile organic compounds (VOCs), the VOCs, in use, coming from the cargo tanks when the cargo tanks are loaded, and at least one hose extending between the carrier vessel and the support vessel for transferring gases comprising volatile organic compounds (VOCs) from the cargo tanks of the carrier vessel to the VOC recovery means on board the support vessel.

[0010] Preferably, the support vessel comprises a dynamic positioning system, more preferably a DP2 system. The dynamic positioning system allows the support vessel to be positioned relative to the carrier vessel. The support vessel may have propellers or thrusters operable under the control of the dynamic positioning system to obtain a desired heading and / or distance away from the carrier vessel. By dynamic positioning, the support vessel may advantageously be held in a desired position and heading relative to the carrier vessel in the presence of forces exerted on the carrier vessel by waves, wind and currents, or when the carrier vessel is rolling or drifting when moored. In particular, the dynamic positioning system may be operable to maintain the support vessel in a predetermined position relative to the carrier vessel and / or to maintain the support vessel spaced apart from the carrier vessel, for example by at least a predetermined distance or interval, in the water. The support vessel may be kept in a predetermined position by operation of the dynamic positioning system such that the separation distance between the support vessel and the carrier vessel may be kept within a predetermined tolerance distance range.

[0011] Typically the support vessel is a platform supply vessel PSV. Alternatively, the support vessel may be, for example, a gas carrier that is newly built and equipped with a dynamic positioning system.

[0012] The system may further comprise a marine mooring, and the carrier vessel may be moored to the mooring. The mooring may constitute a single point mooring. The vessel may be arranged to drift around the mooring. The vessel may be bow moored to the mooring. Alternatively, the mooring may comprise, for example, an island or a conventional anchorage.

[0013] The carrier may typically be a crude oil carrier, such as a tanker, in which case the fluid hydrocarbon cargo may typically include crude oil.

[0014] The VOC recovery means may generally comprise a VOC treatment facility on board the support vessel for treating VOCs from the supplied gas. The VOC recovery means may further comprise at least one storage tank for storing a liquid comprising VOCs. The VOC treatment facility is configured to liquefy the VOCs from the gas to obtain a liquefied liquid comprising VOCs. In this way, the support vessel may be certified for the transport of the liquid in the storage tanks and may conveniently navigate to shore for discharging the VOCs from the tanks.

[0015] According to a second aspect of the present invention there is provided a support vessel for assisting in the loading of a fluid hydrocarbon cargo into at least one cargo tank of a carrier vessel, the carrier vessel transporting the loaded fluid hydrocarbon cargo across an ocean, the support vessel comprising on-board VOC recovery means for recovering volatile organic compounds (VOCs) from the cargo tanks upon loading of the cargo tanks of the carrier vessel.

[0016] The support vessel may further comprise at least one hose extending between the carrier vessel and the support vessel for transferring gases containing VOCs from the cargo tanks of the carrier vessel to treatment facilities on board the support vessel.

[0017] The support vessel may further comprise a dynamic positioning system, for example for positioning and controlling the heading of the support vessel relative to the carrier vessel. The support vessel may further comprise propulsion and / or thruster means, for example for steering or positioning the vessel at a desired heading or distance from the carrier vessel, under control of the dynamic positioning system. The dynamic positioning system may be as described in relation to the first aspect of the invention.

[0018] According to a third aspect of the present invention, there is provided a method comprising the steps of loading a fluid hydrocarbon cargo into at least one cargo tank of a carrier vessel; providing at least one support vessel for facilitating the loading step, the support vessel comprising VOC capture means on board; recovering volatile organic compounds (VOCs) which VOCs come from the cargo tanks in the loading step of the cargo tanks; and supplying gas comprising volatile organic compounds (VOCs) from the cargo tanks of the carrier vessel to the VOC capture means on board the support vessel via at least one hose extending between the carrier vessel and the support vessel.

[0019] The method may further include one or more of the steps of disconnecting the support vessel from the carrier vessel by disconnecting connecting hoses from either or both of the support vessel and the carrier vessel, transporting the loaded fluid hydrocarbon cargo across the ocean with the carrier vessel, and using the support vessel to facilitate loading of another carrier vessel moored at the same mooring or at a different mooring.

[0020] Suitably the support vessel is not moored, more particularly preferably the support vessel is not moored to the carrier vessel and there are no mooring lines between the two vessels, even if for example hoses are connected and in use between the support vessel and the carrier vessel.

[0021] The method may further include storing the VOC-containing liquid from the recovery means in at least one storage tank on board the support vessel, discharging at least a portion of the liquid from the storage tank of the support vessel, and delivering the discharged liquid via a tube to at least one onshore receptor.

[0022] The recovery means may comprise a treatment facility on board the support vessel, and the method may in this case further comprise either or both of operating the treatment facility to liquefy VOCs from the gas supplied to the treatment facility and storing the liquefied VOC-containing liquid in at least one storage tank on board the support vessel. The method may further comprise liquefying the VOCs of the gas in the treatment facility by cooling and condensing the gas to obtain a VOC condensate.

[0023] Any of the various aspects may have one or more features set out in any one or more of the independent claims attached hereto or elsewhere herein.

[0024] Various advantages of different aspects and examples of the present invention will become apparent throughout this specification.

[0025] Various aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic overhead view of an example of a system for loading crude oil onto a crude oil carrier. [Diagram 2] FIG. 1 is a block diagram of a method for loading a crude oil carrier for transportation. [Diagram 3] FIG. 1 is a schematic overhead view of an example in which a carrier ship is moored to an island. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The system 1 in FIG. 1 comprises a crude oil carrier 10 (constituting a carrier), which in this example is moored to an offshore mooring 5 by mooring chains 6 .

[0028] A flexible hose 2 connects between the mooring 5 and a mid-hull manifold 15b of the carrier 10. The hose 2 is buoyant and floats over part of its length in water. Oil to be loaded onto the carrier 10 is delivered from a supply pipeline 3 via the hose 2 to a cargo tank 12 within the hull 13 of the carrier 10.

[0029] The system 1 further includes a support vessel 20. The support vessel 20 is positioned alongside the moored carrier vessel 10. The support vessel 20 is spaced a distance D from one side of the carrier vessel 10 and is controlled to have a heading parallel to the heading of the carrier vessel 10 through use of a dynamic positioning system of the vessel 20.

[0030] The support vessel 20 has a VOC recovery means 21 including an on-board treatment facility 22 for recovering volatile organic compounds (VOCs). To facilitate this, the system includes a supply hose 24 for delivering gas including VOCs from the carrier vessel's cargo tanks 12 to the recovery means 21 on the support vessel. The supply hose 24 extends between the carrier vessel 10 and the support vessel 20. One end of the supply hose 24 in this example is connected to the mid-hull manifold 15a of the carrier vessel 10 and the other end of the supply hose 24 in this example is connected to an inlet pipe 25 of the treatment facility 22. The hose 24 is flexible and stored on a reel 26 on the support vessel 20.

[0031] The treatment facility 22 is operable to receive the gas and liquefy the VOCs to a liquid, for example by compressing and condensing various VOC components of the gas. To this end, the support vessel 22 may be equipped with VOC recovery technology, for example available from Wartsila. The VOC recovery means 21 includes a storage tank 23 for storing the produced liquid, which allows the liquid to be transported on board the vessel and onward across the sea.

[0032] The liquid is temporarily stored in tanks 23 on board the support vessel 20. The liquid may later be discharged and, for example, transported and offloaded ashore when in port, or transferred to the next transhipment facility.

[0033] In this manner, VOCs evolved from the cargo tanks 12 during loading onto the carrier vessel 10 are captured without releasing VOC gases into the atmosphere. The liquefied VOC-containing liquid may be stored on board the support vessel 20 and later safely discharged at a suitable facility on shore or elsewhere.

[0034] Providing the VOC recovery means 21 on the support vessel 20 allows the equipment 22 to be used for the required time during loading, after which the equipment 22 can be easily disconnected for use on another arriving crude oil carrier by simply disconnecting the end of the hose 24. The hose 24 is preferably stored on a reel 26 on the support vessel 20, in which case the end of the hose attached to the midship manifold 15a may be disconnected. Meanwhile the crude oil carrier 10 can depart across the sea for the desired destination of the crude oil. The support vessel 20 can then remain on standby or move to a port for discharging liquid VOCs, for example near the location of the mooring 5 waiting for another crude oil carrier to arrive at the mooring 5. As soon as another crude oil carrier is moored, the support vessel 20 can be utilized again for recovery of VOC gases when the next crude oil carrier is being loaded. Thus the VOC treatment equipment 22 can be preferably put into operation again before the original carrier 10 arrives at its destination. In this manner, the VOC recovery means 21 is conveniently available for repeated operation with new carriers.

[0035] The crude oil carrier 10 is moored at its bow to a mooring 5. The carrier 10 is rotatably moored to the mooring 5. Mooring chains 6 extend from the carrier's bow to the mooring 5. As a result, the carrier 10 can rotatably move, i.e. "float", around the mooring 5 according to the forces imposed by the environment. The crude oil carrier 10 can then be floated so that its bow is positioned towards the direction W of the environmental forces, e.g. the cumulative forces of wind, waves and currents acting on the vessel, and aligned parallel to this direction W. However, any other mooring suitable for a crude oil carrier can be used.

[0036] The support vessel 20 has a dynamic positioning system, preferably a DP2 positioning system, which allows it to maintain a substantially constant position and heading relative to the crude oil carrier vessel 10. The support vessel 20 has thrusters and steering which operate under the control of the dynamic positioning system to maintain its position and heading. If pushed away from the desired position by environmental forces, the dynamic positioning system operates to return the support vessel 20 to its intended, e.g., pre-programmed, original position and heading relative to the carrier vessel 10. If the carrier vessel moves during loading operations, e.g., when drifting, the support vessel 20 can move correspondingly by operation of the dynamic positioning system.

[0037] This may facilitate positioning the support vessel 20 a safe distance away from the carrier vessel 10, but close enough to connect the hose 24. Additionally, the support vessel 20 is mobile and can be easily moved away once the hose 24 has been disconnected and removed, leaving the support vessel 20 ready for future use.

[0038] Conveniently, support vessel 20 is a platform supply vessel (PSV).

[0039] The support vessel 20 is not moored to the carrier vessel 10. The necessary positioning is achieved by a dynamic positioning system and the maneuverability of steering thrusters to steer the support vessel. No mooring lines are used or required between the support vessel and the carrier vessel.

[0040] The only connection between the carrier vessel 10 and the support vessel is a hose 24. This hose can be quickly released in the event of an emergency, such as fire or other reason, such as if the weather suddenly worsens to the point that loading and recovery of released VOC gases cannot continue, allowing the support vessel 20 to be quickly separated from the carrier vessel 10. However, this arrangement can facilitate continued operation even when weather conditions are severe that might otherwise preclude the use of mooring lines.

[0041] In this example, the oil to be loaded is transported through an undersea pipeline 3 to a mooring 5. The mooring 5 has a conduit arranged to carry the fluid from the pipeline 3 to a hose 2 which connects to a mid-hull manifold 15b of the carrier 10 for loading onto the carrier 10.

[0042] Referring to FIG. 2, the method comprises various steps as follows, with steps S1 to S7 numbered the same as shown:

[0043] S1. The crude oil carrier 10 is moored. The loading tube 2 is connected to the carrier 10.

[0044] S2. The support vessel 20 is moved into position alongside the carrier 10 and the supply hose 24 is connected to the carrier.

[0045] S3. Loading of the crude oil occurs. Once loaded, VOC gases or vapors from the carrier's cargo tanks are released from the tanks and transported via connected hoses 24 to a treatment facility 22 on the support vessel 20 where the VOCs are treated. The VOC components of the gas or vapor are converted to a liquid, e.g., condensed, and the liquid is stored in one or more tanks 23 on board the support vessel.

[0046] S4. Once loading is complete, the support vessel 20 and the piping 24 are detached from the carrier vessel 10. The carrier vessel 10 is detached from the moorings and travels out to sea to transport the loaded crude oil to its destination.

[0047] S5. Liquids are generally discharged from the support vessel when full or when a larger volume is required prior to further operation of the support vessel. For example, the support vessel 20 moves to port and the tanks of stored liquid are discharged by transferring the liquid from the tanks 23 to another facility or receiver. The discharged liquids, including VOCs, are generally re-injected into the crude oil or utilized for other purposes onshore or transshipped. The support vessel 20 may then be returned to be located near the mooring or near another mooring and then used in connection with loading another carrier vessel. If the tanks 23 of the support vessel 20 have sufficient volume to accommodate the expected liquids generated in its further use, the support vessel 20 may remain near the mooring or anchorage where it was emptied and / or may move to another nearby mooring ready for further use without discharging the tanks of liquid.

[0048] S6 and S7. Another crude oil carrier is moored at the same or another mooring or anchorage. The support vessel 20 is moved into position alongside the other carrier, the hose 24 is connected, and steps S1-S5 are then repeated with the other carrier, utilizing the support vessel 20 to recover VOCs as the crude oil is loaded onto the carrier.

[0049] In Figure 3, the support vessel 20 is used in conjunction with a crude oil carrier 10 moored at an island 105 from which offloading occurs via a pipeline 102. The island is a fixed structure, typically connected to a pier extending from shore. VOC gases are recovered by treatment equipment 22 on board the support vessel 20 in a corresponding manner with respect to the other moorings of the carrier 10.

[0050] The use of a support vessel 20 with on-board VOC recovery means 21 may facilitate efficient and regular loading of multiple large crude oil tankers 10, each of which may take up to two days, where it is generally desired to fully treat VOCs 4-6 times per week. This system allows VOC service to multiple tankers from one support vessel, making VOC capture a fast and convenient employment, which is particularly suitable for production regions where large volumes of produced oil need to be transported long distances at sea. As the support vessel 20 only needs to be connected to a mid-hull manifold with a hose 24, tankers can advantageously be filled with sufficient standard equipment without any modification to the vessel. Operation using the aforementioned support vessel and system allows large quantities of VOCs to be recovered, and it is estimated that with a fleet of 50 vessels, this solution could reduce annual emissions to the atmosphere by up to 30% CO2 equivalent compared to conventional operations of current daily emissions from mainland Norway.

[0051] Various changes and modifications can be made without departing from the scope of the invention as set forth herein.

Claims

1. a carrier for transporting a fluid hydrocarbon cargo across the ocean, said fluid hydrocarbon cargo being loaded into at least one cargo tank of said carrier; and a support vessel having a dynamic positioning system for positioning the support vessel relative to the carrier vessel; a volatile organic compound recovery means on board the support vessel for recovering volatile organic compounds, the volatile organic compounds being, in use, derived from the cargo tanks as they are loaded into the cargo tanks; and at least one hose extending between the carrier vessel and the support vessel for transferring gas containing volatile organic compounds from the cargo tanks of the carrier vessel to the volatile organic compound recovery means on board the support vessel; A system comprising:

2. 2. The system of claim 1, wherein the support vessel is a platform supply vessel.

3. 3. The system of claim 1 or 2, further comprising an offshore mooring, the carrier vessel being moored to the offshore mooring.

4. 4. The system of claim 1, wherein the carrier is a crude oil carrier and the fluid hydrocarbon cargo comprises crude oil.

5. 5. A system according to claim 1, wherein the volatile organic compound recovery means comprises a volatile organic compound treatment facility for treating the volatile organic compounds from the supplied gas.

6. 6. The system of claim 5, wherein the volatile organic compound recovery means further comprises at least one storage tank for storing liquid containing volatile organic compounds.

7. 7. The system according to claim 5 or 6, characterized in that the volatile organic compound treatment facility is configured to liquefy the volatile organic compounds from the gas to obtain a liquid containing the liquefied volatile organic compounds.

8. a support vessel for assisting in the loading of a fluid hydrocarbon cargo into at least one cargo tank of a carrier vessel, said carrier vessel transporting said loaded fluid hydrocarbon cargo across an ocean; The support vessel: an on-board volatile organic compound recovery means for recovering volatile organic compounds from the cargo tanks of the carrier upon loading of the cargo tanks; and a dynamic positioning system for positioning said support vessel relative to said carrier vessel.

9. 9. The support vessel of claim 8, further comprising at least one hose extending between the carrier vessel and the support vessel for transferring gases containing volatile organic compounds from the cargo tanks of the carrier vessel to a treatment facility on board the support vessel.

10. loading a fluid hydrocarbon cargo into at least one cargo tank of a carrier vessel; Providing at least one support vessel according to claim 8 or 9; recovering volatile organic compounds from the cargo tank of the carrier during the loading of the cargo tank; supplying gas containing volatile organic compounds from the cargo tank of the carrier vessel to the volatile organic compound capture means on board the support vessel via at least one hose extending between the carrier vessel and the support vessel; The method according to claim 1, further comprising:

11. 11. The method of claim 10, decoupling the support vessel from the carrier vessel by disconnecting connecting hoses from either or both of the support vessel and the carrier vessel; transporting the loaded fluid hydrocarbon cargo across the ocean on said carrier vessel; loading the fluid hydrocarbon cargo into at least one cargo tank of another carrier vessel moored at the same mooring or at a different mooring of the carrier vessel; recovering volatile organic compounds from the cargo tank of the other carrier during the step of loading the cargo tank of the other carrier; supplying gas containing volatile organic compounds from the cargo tank of the other carrier vessel to the volatile organic compound capture means on the support vessel via at least one hose extending between the other carrier vessel and the support vessel; The method further comprising:

12. 12. The method according to claim 10 or 11, storing liquid containing volatile organic compounds from the volatile organic compound recovery means in at least one storage tank on board the support vessel; draining at least a portion of the liquid from the storage tank of the support vessel; delivering the discharged liquid through a tube to at least one land-based receptor; The method further comprising:

13. 13. The method of any one of claims 10 to 12, wherein the volatile organic compound recovery means comprises a treatment facility on board the support vessel, the method comprising: operating the treatment facility to liquefy volatile organic compounds from the gas provided to the treatment facility; storing the liquefied liquid containing volatile organic compounds in at least one storage tank on board the support vessel; The method further comprising:

14. 14. The method of claim 13, further comprising the step of liquefying the volatile organic compounds of the gas by cooling and condensing the gas to obtain a volatile organic compound condensate.

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