GB1581326A

GB1581326A - Oil storage vessel and method of delivering oil

Info

Publication number: GB1581326A
Application number: GB4225179A
Authority: GB
Original assignee: SEA TERMINALS Ltd
Current assignee: SEA TERMINALS Ltd
Priority date: 1977-03-31
Filing date: 1977-03-31
Publication date: 1980-12-10

Description

(54) OIL STORAGE VESSEL AND METHOD OF DELIVERING OIL (71) We, SEA TERMINALS LI MITED, a company organised under the laws of the Cayman Islands of 4th Floor West Wind Buildings, P.O. Box 156, Grand Cayman, Cayman Islands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the storage and transfer of oil.

At present, offshore oil wells generally feed their output into a crude oil pipeline which stretches along the sea bed to a suitable point on the shore. Oil from the pipeline is then generally stored in large capacity storage facilities at or near the coast. The construction of land-based oil storage facilities and, more particularly, the construction of submerged crude oil pipelines involves very large capital expenditure.

An aim of the present invention is to provide means for delivering oil from an offshore well or wells (field) which do not require the construction of large sea bed pipelines to shore and which may obviate, or at least reduce, the requirement for construction of land based storage facilities.

According to one aspect of the present invention, there is provided an oil storage vessel which is provided with (a) a flexible hose for delivery of oil, one end of said hose being adapted for connection to the oil storage capacity of the vessel; and (b) a hose guide system which is constructed so as to receive and support said flexible hose, and which comprises (i) a travelling sheave adapted to allow the flexible hose to pass around it, the sheave being mounted on guide means for travel along a track extending generally parallel to the longitudinal axis of the vessel; (ii) a first hose support channel positioned on one side of said track, for supporting the flexible hose between its connection with the oil storage capacity of the vessel and the travelling sheave; and (iii) a second hose support channel, positioned on the opposite side of said track to said first hose support channel for supporting the flexible hose between the travelling sheave and one end of the vessel, whereby the flexible hose can be supported in a generally U-shaped course defined by the first hose support channel, the travelling sheave and the second hose support channel between its connection with the oil storage capacity of the vessel and said one end of the vessel.

According to another aspect of the invention, there is provided a method of delivering oil from an off-shore well to the shore, which comprises the steps of (a) supplying oil from the well, or from a production facility associated with the well, to a floating storage vessel moored close to the well or production facility; (b) ferrying a service tanker from the shore towards the oil storage vessel; (c) tethering said service tanker to the oil storage vessel; (d) transferring oil from the oil storage vessel to said service tanker by means of a flexible hose connected at one end thereof to the coil storage capacity of said oil storage vessel and the other end of which extends directly or via hose extensions to the service tanker; (e) causing said flexible hose to travel in a generally U-shaped course before it leaves the oil storage vessel, said course being defined by a first hose support channel, a travelling sheave around which the flexible hose passes, and a second hose support channel, said travelling sheave being mounted on guide means for travel along a track extending generally parallel to the longitudinal axis of the vessel, and being attached to a constant tension device whereby relative movement between the oil storage vessel and the service tanker can be accommodated through travel of the sheave along its track, thereby paying out a greater or lesser length of flexible hose in accordance with the separation at any given time between the oil storage vessel and the service tanker; (f) disconnecting the supply of oil when a predetermined quantity has been transferred to the service tanker; and (g) ferrying said service tanker back to the shore.

A single point mooring which may be used for mooring an oil storage vessel in accordance with this invention is described and claimed in our co-pending patent application No. 49120/75 (Specification No.

1581325).

Oil is preferably supplied continuously to the oil storage vessel and removed therefrom in batches (by way of the service tanker). The oil is preferably supplied directly to the oil storage vessel from a submarine well head; it may, however, be supplied to the vessel from an oil production platform.

The floating storage vessel will generally be moored to a location on the sea bed or near the wells by means permitting the vessel to adopt a position in accordance with prevailing weather conditions; the mooring may be effected by chain or by other bottom-linking systems. It is preferred to use a submerged mooring arrangement of the type described in our co-pending parent application No. 49120/75 (Specification No.

1581325).

Dynamic assist propulsion may be employed if necessary by the oil storage vessel to ease inordinant strain on the mooring and to keep the vessel in the most accommodating attitude relative to a complex sea where wind wave and current create difficult circumstances. Three reference means are preferably available to keep the storage vessel, e.g. a ship, in position relative to the mooring. Where chain is used for mooring, crude oil can be supplied to the floating storage vessel by means of one or more risers, from the sea bed to the storage vessel, the riser(s) and its or their connection(s) with the storage vessel being arranged so that they can accommodate the heave of the vessel.For application in relatively shallow water as well as in deep sea (over 200' water depth) application, the turning attitude of the ship (whether adjusting heading for weather when multiple chain moorings are used or "hunting" off the direct line from the ideal longitudinal keel line to the mooring point on a submerged single anchor leg mooring) is preferably accommodated in the hose connections at the storage vessel. This can be done in the case of a single riser or single submarine hose by a rotating seal or as described below. Where multiple risers or hoses are used, a rotating plate built into the ship above the water line can be employed. The risers or submarine hoses are connected to suitable connecting ports on the underside of the rotating plate. Flexible helically coiled hoses are attached to connecting ports on the topside of the rotating plate.

These flexible hoses form a regular helical array located along an arcuate course.

There will be enough flexibility in the curvature and bending of the hoses to allow the ship to turn in disorientation from the rotating plate 90" to starboard and 90" to port. Where deep sea mooring facilities are used (generally with over 300 feet water depth) oil may pass from the well to a fluid swivel built into the mooring facility itself.

The flexible hose or pipeline for conveying oil from the storage vessel to a service tanker is fed out via the sheave (crosshead) which is constructed so that it can move in a fixed path forward and aft along a selected length of the floating storage vessel, and preferably under the influence of a self-tensioning device, for example a self-tensioning winch. Preferably, the track for the sheave is in the form of a pair of parallel rails mounted on the deck of the vessel. The guide means for the sheave is advantageously a sled to which the sheave is attached by a ball and race arrangement.

Brake shoes can be provided in association with the sheave to assist in controlling its movement. The sheave is advantageously provided with hose guide apparatus to control the run of the hose around the sheave. Two or more piplines each with a sheave and associated facilities may be provided on the floating storage vessel so as to increase the rate of delivery of oil therefrom or to use one hose to pass oil to the service tanker and the other to pass dirty ballast water from the service tanker to the floating storage tanker.

Hose guide tongues are preferably provided adjacent the or each sheave so as to guide the flexible hose between the sheave and the first and second hose support channels. The flexible hose can be fixed at one end thereof to a fixed manifold which is in communication with the oil storage capacity of the vessel and is located adjacent one end of the first hose support channel.

Because of the relative movement between the flexible hose and the walls of the second hose support channel when the travelling sheave is moving, it is preferred to provide bearing elements in the second hose support channel. Each of the first and second hose support channels can take the form of an elongate trough on the deck of the vessel.

The vessel advantageously also comprises a further support system over which said flexible hose or a hose extension connected to said flexible hose may be carried so as to extend from the stern of the oil storage vessel towards another vessel stationed behind the oil storage vessel. In addition, hose delivery means (e.g. in the form of a plurality of horizontal and vertical guide members) will generally be provided for conveying the hose from the hose guide system to the further support system. The further support system itself, which is involved in supporting the hose at the stern of the vessel where the hose is conveyed towards a service tanker, can take the form of an extensible framework in the form of an "A" frame which, in its extended condition, is adapted to hold the flexible hose above the stern of the vessel.When extended, the "A" frame can pass upwardly at an oblique angle over the stern of the vessel; when collapsed, the "A" frame can rest on the deck in a relatively flat condition. A curved hose guide is preferably located at the outward end of the "A" frame.

The vessel can include a self-tensioning or manually controlled mooring line arrangement for use when transferring oil from the floating storage vessel to a service tanker.

The mooring line is preferably provided with a "colour coding" so that the length of mooring paid out at any given time can be seen from the colour(s) visible. In one of two presently preferred methods, the mooring line supports the oil hose. In the other, the hose passes over the "A" frame just described and hangs in a catenary between the "A" frame apex and the bows of the service tanker. Other arrangements may be employed if desired.

The vessel is advantageously provided with a spindle cylinder including a mooring tube by means of which the vessel can be held in position on a mooring. Such a mooring tube is preferably located in the forward part of the vessel. It is preferred to have the mooring tube as part of a spindle arrangement which is also adapted to have submarine hose-handling equipment. A preferred spindle arrangement is that of a cylinder built into the vessel which cylinder houses the mooring equipment, submarine hose-handling equipment and diving equip ment. The spindle cylinder is emplaced at an optimum position, generally somewhere between the bow and 1/3 aft. The vessel will then be capable of rotating, or "weather cocking", about a mooring pipe in the spindle cylinder in response to changing weather conditions.

Means are preferably included on the vessel to assist in holding the vessel on station.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accom panying drawings, in which: Figures 1 and 2 show respectively a schematic plan view of a floating oil storage vessel in accordance with the invention, and an isometric view of part of the vessel; Figure 3 illustrates an embodiment of oil storage vessel and its connection to an underwater oil pipeline; and Figure 4 illustrates part of the structure shown in Figure 3.

Referring first to Figures 1 and 2 of the drawings, the oil storage vessel which is preferably of 210,000 to 255,000 tons is provided with a manifold 1 which is the outlet for oil from the vessel's tanks via the pump room. An oil hose H is attached to the manifold 1, and passes through or about a number of structures before passing over the stern of the vessel. The manifold 1 is built to a height so the hose H can lie directly from it in a first hose support channel or trough 3 (only partial section shown in Figure 2). The trough 3 is termed a static trough because the parts of the hose lying therein are stationary; the trough is deep enough to hold whatever diameter hose is being used. Thehose H passes out of the trough 3 and around a sheave 5 which is mounted on a guide sled 7.A hose guide tongue 4 is provided to enable the hose to be guided out of the static trough 3 and onto the sheave 5, or vice versa. The hose guide tongue can take the form of concave spindle bearings along. which the hose can slide, the bearing being held to a foot which slides in the bottom of the static trough 3. A similar hose guide tongue 4' is provided on the other side of the sheave 5, and serves to let the oil hose into a second hose support channel or trough called an active trough 12.

Both troughs 3 and 12 are formed on the deck of the vessel.

The hose sheave 5 can be mounted upon the guide sled by means of a ball and race arrangement 8. The diameter of the hose sheave 5 is generally determined by the most severe bending radius that can be accommodated by the oil hose. The tangential edge of the sheave circumference is positioned as close as possible to the hose troughs 3 and 12 so as to minimise distortion and wear of the hose. When the sheave is not in use, it may be mechanically secured to the structure of the vessel.

The guide sled 7 comprises a frame mounted on wheels which are guided by two rails 50 which lap over the top of the wheels.

The hose guide tongues 4 and 4' are attached to the guide sled 7. Additionally, brake shoes 6 are attached to the guide sled and serve firstly to prevent the hose from jumping out of the sheave 5, and secondly to act as an emergency braking system in the event of an operational failure, for example loss of tension in the constant tensioning devices to be described hereafter, or fracture of the oil hose.

A self-tensioning winch 10 is provided on the vessel, and is connected via a wire or wires 10' to the guide sled 7 when oil is being delivered through the hose H. The winch 10 ensures that the sheave 5 is held at substantially constant tension when oil is being delivered through the hose H, and also provides the motive power for movement of the sheave 5 along the rail track 50 when oil delivery via the hose H is complete, and the hose is being drawn in from the service tanker. An auxiliary winch may be provided to assit movement of the sheave 5 in the opposite direction if required.

An axle 9 passes through the sheave 5 and the guide sled 7, and acts to lessen the stress on the ball and race 8 as pressure is exerted on the sheave 5.

The brake shoes 6 may be operated by any convenient mechanism. In one embodiment, a hydraulic line 11 which is fed out from a further winch (not shown) is used to actuate the brake shoes 6. The hydraulic line is not self-tensioning, and the further winch is operated so that it cannot pull tight, thus preventing a danger of breaking the hydraulic line, this being made possible because of its low overload rating.

The active hose trough 12 includes concave spindle bearings in the base of the trough and cylindrical roller bearings along the side walls of the trough. These are provided to lessen friction between the hose and the trough 12, but arse not required in the case of the static hose trough 3 because there is not relative movement between the hose H and the surfaces of the trough 3. The trough 12 extends along the vessel from the location of the sheave 5 and its associated track to that part of the vessel from which the flexible oil hose is paid out. The end of the trough 12 remote from the sheave 5 is provided either with a flared hose exit 17 at deck level (see Figure 1) or with an "A" frame over the apex of which the hose passes (see Figures 3 and 4).Such an "A" frame facilitates passage of the hose and allows for a disorientation of more than 30 degrees between the floating storage vessel and a service tanker to which oil is to be supplied. The "A" frame 22 illustrated in Figure 4 is constructed so that half of it 23 can fold back on the base section through the use of a hinge which can be locked and the use of two hydraulic cylinders (not shown) which will allow the top section to be gently lowered on the base section. In the folded over position as at 25 in Figure 4 the equipment can be considered stowed and maintenance can be performed on the top section. At the top of the "A" frame, the radius of curvature accommodates the bend ing radius of the hose and this section is flared to allow the hose to move laterally within limits off the apex centre without constricting or binding the hose.This accommodates excursion of the service tanker T. The length of the extended and locked "A" frame is dependent on the space available at the aft end of the ship and the amount of overhang permitted of the folded "A" frame over the stern of the ship. A horizontal bollard 13 (see Figure 1) is positioned over the hose and trough at a location forward of the flared hose exit 17 and serves to keep the oil hose in the trough 12. A similar bollard will be provided forward of the base of the "A" frame 22 shown in Figure 4. Mooring equipment including a self-tensioning or a manually controlled device for a mooring line, for example a winch, is provided on the vessel.

Where the hose is passed to a service tanker by the use of the mooring line as a guide, a plurality of blocks are provided each with an associated clamp, the blocks riding along the mooring hawser in use, and the clamps serving to fasten the oil hose, through the blocks, to the mooring hawser. The blocks and clamps can be stored in any suitable position when not in use; this is indicated for convenience as 15 in Figure 1 of the drawings.

In the embodiment shown in Figure 1, the hose passes through one or several pairs of vertical hose bollards 16, which may be located in the region of the flared hose exit 17. These bollards 16 can take the form of vertical rolling cylinders which apply a light compression on the hose. It is envisaged that the bollards will be about six feet high.

The bollards should be fabricated from a material which is able to grip the hose material adequately without damaging the hose. Instead of rolling cylinder bollards, concave spindles may be provided in order to give a firmer grip on the hose and thereby to prevent vertical movement.

Before passing from the floating storage vessel, the oil hose H passes over one or more roller(s) 18 which serve(s) to protect the hose from hitting the gunwale of the ship and to avoid abrasion and undue stressing of the hose when there is considerable movement in rough weather. Similar rollers may be located at the apex of the "A" frame if this arrangement is used instead of the flared exit 17.

In Figure 1 of the drawings, the mooring hawser is indicated generally as 19, and a single block and clamp 20 is shown. The blocks are lightweight structures attached to run freely on the mooring hawser. The clamps may be attached to their respective blocks by a rod with a limited action pivot at the block. The clamps can be of the quickfit adjustable type which grips the oil hose. The material on the inside of the clamp should be such that adequate grip of the hose takes place without wear.

In the embodiment of oil storage vessel shown in Figures 3 and 4, the hose H is freely suspended from the apex of the "A" frame 22 and across to the service tanker T.

An alternative arrangement (not illustrated) is for the oil transfer hose H to be totally submerged between the oil storage vessel and the service tanker. Other arrangements may also be adopted where desired - e.g. involving the use of cranes.

The floating storage vessel also includes strayline equipment indicated diagrammatically at 21 and means for either streaming the lines on the sea surface astern of the storage vessel or projecting the line in the air astern of the storage vessel, for example by a telescopic jib. The strayline may be thrown by a gun. A cage may be provided to protect the strayline throw position.

One preferred mooring system for use with the invention is illustrated in Figure 3.

The mooring system, which is described and claimed in our co-pending patent application No. 49120/75 (Specification No.

1581325),. comprises a base 30 located on the sea bed, to which a riser tube 22 is attached by means of a universal joint 31.

An oil pipeline 33 located on the sea bed is connected, via manifold 34 and flexible bottom hose 35, to oil line 36 which is located aside the riser 32. At the top of the riser there is a platform 37 located about a coupling 38 on top of which is a fluid swivel 39 which is coupled to a universal joint 40.

A spacer buoy 41 is attached to the universal joint 40, and a mooring chain or hawser 42 extends from the spacer buoy to the oil storage vessel. The shape of the spacer buoy can be varied from the generally cylindrical structure shown in Figure 3. For example, it may have a generally flat surface portion extending downwardly from the point at which mooring chain 42 is connected thereto. A hose guide tray 43 is attached to the fluid swivel 39 and provides a channel through which oil hose 44 is conveyed. This hose serves to supply oil from oil line 36 to the storage tank in the storage vessel. The spacer buoy is located sufficiently deep to be free from severe wave action.

In the embodiment shown in Figure 4, the spacer buoy is modified and extended up to the surface by means of a cylindrical element 45. This is connected above the waterline by a mooring 46 to the bows of the oil storage vessel or of a ferrying service tanker.

The storage capacity of the floating stor age vessel may be as large as required, the aim generally being to allow constant input of oil from the oil wells to the floating storage tanker while allowing batch delivery of oil from the floating storage vessel to service tankers. It is envisaged that the service tankers will have a capacity of from 80,000 to 100,000 tons, though smaller vessels, for example of 60,000 ton capacity, may be more useful in certain instances.

It is envisaged that the floating storage vessel will ordinarily have about 26,000 to 28,000 horsepower capacity in its main propulsion plant. The vessel may be provided with "dynamic assist" propulsion in order to ease mooring stresses built up by its motion and to keep the vessel in the best position.

In addition to acting as the main oil storage vessel, the floating storage vessel may also be used as the crude production facilities in cases where subsea well completions are used. Facilities for scrubbing the oil before trans-shipment to a refinery may be included on the floating storage vessel.

Use of a storage vessel as described may possibly allow oil production without the use of a production platform self-supporting or floating structure.

The presently envisaged procedure for supplying oil from the floating storage vessel to a service tanker will now be described.

Firstly, a service tanker will steam from the shore to within 200 feet of the storage tanker. The service tanker has already picked up the floating strayline thrown out from portion 21; alternatively, the strayline may be passed at this stage by a telescoping jib mounted under one of the "A" frames (see Figure 3). The mooring hawser 19 from the floating storage vessel, attached to the strayline, is hauled across to the service tanker. At this stage, the sheave 5 and guide sled 7 together with the oil hose H will be in the forward position towards amidships as shown in Figure 3. When the mooring hawser is secured, the service tanker will stay in a position approximately 150-300 feet astern of the floating storage tanker, depending on weather conditions, for safety.

Once a suitable distance between the floating storage vessel and the service tanker is attained, the service tanker, where propeller control is fine enough, operates its reverse power to provide a given mooring line tension and thus avoid snatch loadings.

A strayline attached to the mooring hawser and attached to the delivery end of the oil hose H is then pulled across slowly by the service tanker, carrying with it and oil hose H. During this process, the sheave 5 moves from the midships area of the floating storage vessel in the general direction aft towards the storage tanker stern. As the oil hose is paid out from the trough 12 and is passed by suspending it on the mooring line, clamps 20 are fitted about its circumference at regular intervals, the clamps then being carried along by their associated blocks which ride freely along the mooring hawser.

Once the oil hose is aboard the service tanker, a quick release coupling is stabbed into a receiving port in the service tanker to complete the oil flow line. Where an "A" frame is used the hose passes from the trough 12 over the "A" frame which has a built-in continuation of trough 12 and a suitable radius of curvature over the "A" frame apex. Like the suspended hose method the oil hose is hauled aboard the service tanker and a quick release coupling is stabbed into a receiving port. The sheave 5 is then tensioned by the winch 10 so that the oil hose is prevented from moving due solely to the weight of the suspended portion of the hose and of the catenary between the vessel and the service tanker. Under these conditions, the connection between the floating storage vessel and the service tanker is resilient, and may allow for an extra 150 feet separation movement between the vessels.Lateral drifting of one vessel relative to the other is tolerable as far as the hose is concerned where the bow of the service tanker does not move laterally from the longitudinal axis of the storage vessel more than one hundred feet to port or one hundred feet to starboard. Oil is pumped through the oil hose from the tanks of the floating storage vessel to those of the service tanker. Once delivery of a predetermined quantity of oil is complete the sequence of events just described is reversed so that the oil hose is withdrawn from the service tanker which is ferried back to shore and its length, which may be up to 1000 feet, is accommodated by movement of the sheave 5 along its track in a direction away from the service tanker.

For more rapid delivery of oil, the floating storage vessel is provided with a double delivery system as shown in the drawings.

The oil hose may advantageously be 20 or 24 inches in diameter, which allows a high rate of oil transfer.

Delivery of oil (e.g. from line 33 on the sea bed) into the oil storage vessel takes place continuously; thus, problems associated with sudden changes of pressure in the oil lines are eliminated.

The connection between the storage vessel and the service tanker is, by virtue of the travelling sheave 5, resilient and allows for considerable movement between the vessels to occur. This is valuable, especially in an emergency such as parting of the mooring line between the vessels: under such conditions, the crew will have time to effect an orderly shutdown and/or disconnection of the oil hose H.

WHAT WE CLAIM IS: 1. An oil storage vessel which is provided with (a) a flexible hose for delivery of oil, one end of said hose being adapted for connection to the oil storage capacity of the vessel; and (b) a hose guide system which is constructed so as to receive and support said flexible hose, and which comprises (i) a travelling sheave adapted to allow the flexi ble hose to pass around it, the sheave being mounted on guide means for travel along a track extending generally parallel to the longitudinal axis of the vessel; (ii) a first hose support channel positioned on one side of said track, for supporting the flexible hose between its connection with the oil storage capacity of the vessel and the travelling sheave; and (iii) a second hose support channel, positioned on the opposite side of said track to said first hose support channel, for supporting the flexible hose between the travelling sheave and one end of the vessel, whereby the flexible hose can be supported in a generally U-shaped course defined by the first hose support channel, the travelling sheave and the second hose support channel between its connection with the oil storage capacity of the vessel and said one end of the vessel.

2. A vessel as claimed in claim 1, where in said sheave is attached to a constant tension device.

3. A vessel as claimed in claim 2, where in the constant tension device is a self tensioning winch.

4. A vessel as claimed in claim 1, 2 or 3, wherein the guide means for said travelling sheave are in the form of a sled which is adapted to travel on said track.

5. A vessel as claimed in claim 4, where in the sheave is supported on the sled by a ball and race arrangement.

6. A vessel as claimed in any preceding claim, which further includes hose guide tongues adjacent the sheave which are adapted to guide the flexible hose between the sheave and the first and second hose support channels.

7. A vessel as claimed in any preceding claim, wherein said track is formed by a pair of parallel rails.

8. A vessel as claimed in any preceding claim, wherein the flexible hose is con nected at one end thereof to a fixed man ifold in communication with the oil storage capacity of the vessel, said manifold being adjacent one end of the first hose support channel.

9. A vessel as claimed in any preceding claim, wherein bearing elements are pro vided in said second hose support channel against which bearing elements the flexible hose can slide when the travelling sheave moves.

10. A vessel as claimed in any preceding claim, wherein each of the first and second hose support channels is formed as an elongate trough on the deck of the vessel.

11. A vessel as claimed in any preceding claim, wherein brake shoes are provided in association with the travelling sheave.

12. A vessel as claimed in any preceding

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. into a receiving port in the service tanker to complete the oil flow line. Where an "A" frame is used the hose passes from the trough 12 over the "A" frame which has a built-in continuation of trough 12 and a suitable radius of curvature over the "A" frame apex. Like the suspended hose method the oil hose is hauled aboard the service tanker and a quick release coupling is stabbed into a receiving port. The sheave 5 is then tensioned by the winch 10 so that the oil hose is prevented from moving due solely to the weight of the suspended portion of the hose and of the catenary between the vessel and the service tanker. Under these conditions, the connection between the floating storage vessel and the service tanker is resilient, and may allow for an extra 150 feet separation movement between the vessels.Lateral drifting of one vessel relative to the other is tolerable as far as the hose is concerned where the bow of the service tanker does not move laterally from the longitudinal axis of the storage vessel more than one hundred feet to port or one hundred feet to starboard. Oil is pumped through the oil hose from the tanks of the floating storage vessel to those of the service tanker. Once delivery of a predetermined quantity of oil is complete the sequence of events just described is reversed so that the oil hose is withdrawn from the service tanker which is ferried back to shore and its length, which may be up to 1000 feet, is accommodated by movement of the sheave 5 along its track in a direction away from the service tanker. For more rapid delivery of oil, the floating storage vessel is provided with a double delivery system as shown in the drawings. The oil hose may advantageously be 20 or 24 inches in diameter, which allows a high rate of oil transfer. Delivery of oil (e.g. from line 33 on the sea bed) into the oil storage vessel takes place continuously; thus, problems associated with sudden changes of pressure in the oil lines are eliminated. The connection between the storage vessel and the service tanker is, by virtue of the travelling sheave 5, resilient and allows for considerable movement between the vessels to occur. This is valuable, especially in an emergency such as parting of the mooring line between the vessels: under such conditions, the crew will have time to effect an orderly shutdown and/or disconnection of the oil hose H. WHAT WE CLAIM IS:

1. An oil storage vessel which is provided with (a) a flexible hose for delivery of oil, one end of said hose being adapted for connection to the oil storage capacity of the vessel; and (b) a hose guide system which is constructed so as to receive and support said flexible hose, and which comprises (i) a travelling sheave adapted to allow the flexi ble hose to pass around it, the sheave being mounted on guide means for travel along a track extending generally parallel to the longitudinal axis of the vessel; (ii) a first hose support channel positioned on one side of said track, for supporting the flexible hose between its connection with the oil storage capacity of the vessel and the travelling sheave; and (iii) a second hose support channel, positioned on the opposite side of said track to said first hose support channel, for supporting the flexible hose between the travelling sheave and one end of the vessel, whereby the flexible hose can be supported in a generally U-shaped course defined by the first hose support channel, the travelling sheave and the second hose support channel between its connection with the oil storage capacity of the vessel and said one end of the vessel.

12. A vessel as claimed in any preceding

claim, which also comprises a further support system over which said flexible hose or a hose extension connected to said flexible hose may be carried so as to extend from the stern of the oil storage vessel towards another vessel stationed behind the oil storage vessel.

13. A vessel as claimed in claim 12, which further comprises hose delivery means for conveying said hose from the hose guide system to said further support system.

14. A vessel as claimed in claim 13, wherein the hose delivery means comprise a plurality of horizontal and vertical guide members.

15. A vessel as claimed in claim 12 or 13, wherein said further support system comprises an extensible framework in the form of an "A" frame which, in its extended condition, is adapted to hold said flexible hose above the level of the stern of the vessel.

16. A vessel as claimed in claim 15, wherein the "A" frame, in its extended condition, extends upwardly at an oblique angle over and above the stern of the vessel, and, in its collapsed condition, rests in a relatively flat condition on the deck of the ship.

17. a vessel as claimed in claim 16, in which the outward end of said "A" frame is provided with a curved hose guide.

18. A vessel as claimed in claim 16 or 17, wherein the extensible framework is foldable at least at one lockable joint which enables the extensible framework to be moved from its collapsed condition into its extended condition.

19. A vessel as claimed in any preceding claim. which is further provided with a spindle cylinder including a mooring tube whereby the vessel can be held in position on a mooring.

20. A vessel as claimed in claim 19, wherein said mooring tube is located in the forward part of the vessel.

21. A vessel as claimed in claim 19 or 20. wherein the spindle arrangement is also adapted to house submarine hose-handling equipment.

22. A vessel as claimed in claim 21, wherein said spindle is constructed so as to house diving equipment.

23. A vessel as claimed in any preceding claim, which is further provided with means for assisting in holding the vessel on station.

24. A method of delivering oil from an off-shore well to the shore, which comprises the steps of (a) supplying oil from the well, or from a production facility associated with the well, to a floating storage vessel moored close to the well or production facility; (b) ferrying a service tanker from the shore towards the oil storage vessel; (c) tethering said service tanker to the oil storage vessel; (d) transferring oil from the oil storage vessel to said service tanker by means of a flexible hose connected at one end thereof to the oil storage capacity of said oil storage vessel and the other end of which extends directly or via hose extensions to the service tanker; (e) causing said flexible hose to travel in a generally U-shaped course before it leaves the oil storage vessel, said course being defined by a first hose support channel, a travelling sheave around which the flexible hose passes, and a second hose support channel, said travelling sheave being mounted on guide means for travel along a track extending generally parallel to the longitudinal axis of the vessel, and being attached to a constant tension device whereby relative movement between the oil storage vessel and the service tanker can be accommodated through travel of the sheave along its track, thereby paying out a greater or lesser length of flexible hose in accordance with the separation at any given time between the oil storage vessel and the service tanker; (f) disconnecting the supply of oil when a predetermined quantity has been transferred to the service tanker; and (g) ferrying said service tanker back to the shore.

25. A method of delivering oil from an off-shore well to the shore, substantially as hereinbefore described with reference to the accompanying drawings.

26. An oil storage vessel substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.