WO2000078603A1

WO2000078603A1 - Equipment for storage of a loading hose in a body of water, and method of transferring the hose from the storage position to a position of use

Info

Publication number: WO2000078603A1
Application number: PCT/NO2000/000217
Authority: WO
Inventors: Arild K. Samuelsen
Original assignee: Navion AS
Current assignee: Altera Norway AS
Priority date: 1999-06-23
Filing date: 2000-06-22
Publication date: 2000-12-28
Anticipated expiration: 2001-12-23
Also published as: NO993130L; NO993130D0; NO311295B1; AU5257200A

Abstract

There is provided an equipment for storage of a loading hose (1) in a body of water (2), wherein the hose has a specific gravity which is less than one, wherein the equipment comprises coupling/weight units (3, 4) which are connected to a respective end of the hose (1) and are adapted to rest on the seabed (6), each unit (3 resp. 4) comprising an end piece for connection to a pipe system on a vessel, and a weight means of a sufficient weight to keep the hose end stably in place on the seabed (6), a weight/scrubbing link (5) mounted on the hose (1) at a middle region thereof, and a pair of handling lines (7) connected with one end thereof to a respective one of the coupling/weight units (3, 4), and connected with their other end to a buoy means (8) at or on the water surface (9). In use, the coupling/weight units (3, 4) and the weight/scrubbing link (5) are placed on the seabed (6) at such a mutual distance that the intermediate parts of the hose (1) because of their buoyancy will stand like an arc upwards in the body of water (2). There is also provided a method of transferring such a loading hose (1) from a submerged storage position to a position of use in which the loading hose forms a load-transferring connection between, for example, a pair of tankers.

Description

Equipment for storage of a loading hose in a body of water, and method of transferring the hose from the storage position to a position of use

The invention relates to an equipment for storage of a loading hose in a body of water, wherein the hose has a specific gravity which is less than one. Further, the invention relates to a method for transferring a loading hose from a submerged storage position to a position of use in which the hose forms a load-transferring connection between a loading and an unloading unit, for example two tankers.

In offshore oil production, tanker transport is an alternative to transport via pipe connections. Dependent on the location of the field it may be of interest first to transfer the produced oil to a specially constructed shuttle tanker which thereafter brings the load to a place where it is transferred to a conventional barging vessel transporting the load to a receiver. Since a conventional tanker (the barging vessel) has much lower daily rates than a specially constructed shuttle tanker, together with a larger loading capacity, the transport costs can be reduced significantly if the transport is based on conventional tankers instead of only the use of special ships.

When transferring the load from the shuttle tanker to the barging vessel, there are used loading hoses, typically with a diameter of 20 - 24 inches and a length of 250 - 400 meters. In the periods when the hose is not used, it is necessary to store the hose in a satisfactory manner, so that it is not destroyed by environmental forces (waves and ocean currents), or by vessels which might happen to be in the storage area.

The object of the invention is to provide an equipment enabling a safe and lenient underwater storage of a loading hose of the above-mentioned type, and allowing a safe and rational transfer of oil between a loading and an unloading unit in open sea during changing weather conditions with the highest possible continuity.

Another object of the invention is to provide a method for rational and safe transfer of such a loading hose from the storage position to its position of use. In accordance with the invention there is provided an equipment of the stated type which is characterized by the characterizing features according to claim 1.

Further, there is provided a method which is characterized by the features stated in claim 10.

By means of the equipment according to the invention, a loading hose is kept stored in a body of water without the "soft" floating parts of the hose coming into contact with the sea or ocean floor. Further, the hose is protected in relation to vessels operating in the area. The equipment and the method may be used on all the relevant water depths.

The invention will be further described below in connection with exemplary embodiments with reference to the drawings, wherein Fig. 1 shows a loading hose which is stored on the bottom under a body of water by means of an equipment according to the invention;

Fig. 2 shows a longitudinal section of a hose segment forming part of an embodiment of the loading hose; Fig. 3 shows the detail A in Fig. 1 on an enlarged scale, i.e. a side view of an embodiment of a weight/scrubbing link,

Fig. 4 shows the detail B in Fig. 1 on an enlarged scale, i.e. a side view of a first embodiment of a combined coupling/weight unit;

Fig. 5 shows the detail C in Fig. 1 on an enlarged scale, i.e. a side view of a second embodiment of a combined coupling/weight unit;

Fig. 6 shows an end view of the coupling/weight unit in Fig. 5; Fig. 7 shows picking-up of a loading hose directly from a shuttle tanker; Fig. 8 shows picking-up of the loading hose by means of a tender; Fig. 9 shows raising of the loading hose from the seabed by the use of tender and shuttle tanker;

Fig. 10 shows the hose hanging between shuttle tanker and tender; Fig. 11 shows a barging vessel and a shuttle tanker coupled to each other via the loading hose;

Fig. 12 illustrates the rotary circle of the barging vessel in relation to the position of me shuttle tanker during load transfer;

Fig. 13 shows disconnection of the loading hose from the shuttle tanker and lowering of the hose after completed load transfer; and

Fig. 14 shows picking-up of the loading hose directly from a shuttle tanker, wherein the hose is in an intermediate storage position. Fig. 1 shows a hose 1 which is stored in an underwater position in a body of water 2 by means of an equipment according to the invention. The equipment comprises, inter alia, a pair of combined coupling and weight units 3 and 4, respectively, which are connected to a respective end of the hose 1 and which are further shown in Fig. 4 and Figs. 5-6, respectively. Further, the equipment comprises a weight/scrubbing link 5 which is mounted on the hose 1 at a middle portion thereof, and which is further shown in Fig. 3. In the storage position of the hose, each of the coupling/weigh units 3, 4 rest on the seabed 6, and the same is the case with the weight/scrubbing link 5.

Each of the coupling/weight units 3, 4 is connected to one or a lower end of a respective handling line 7, the other or upper end of each handling line being connected to a buoy means 8 having a suitable buoyancy to keep itself floating on the surface 9 of the water or at a chosen distance below the surface. In the illustrated embodiment, each of the buoy means 8 comprises a pair of buoyancy buoys 10 which, through a shackle/swivel unit 11, are connected to a marking buoy (e.g. a light buoy) 12 floating on the water surface, and to which there is fixed one end of a floating line 13 which, at its opposite end, and possibly also at an intermediate place, is connected to a smaller marking buoy 14.

The used loading hose 1 suitably consists of a plurality of segments. An embodiment of such a segment 20 is shown in Fig. 1. The segment is provided with end flanges 21, e.g. bolt flanges, for interconnection of adjoining segments, and is formed from an inner hose wall 22 which is covered by an outer layer 23 of the buoyancy material. The hose wall for example may consist of rubber, and the outer layer may consist of a suitable plastic material, e.g. polyester. The buoyancy is determined by the relevant water depth, the length of the hose and the utilized anchoring weights. Each segment may have a length of 12 meters.

Fig. 3 shows the detail A in Fig. 1 on an enlarged scale and shows a side view of the weight/scrubbing link 5. As shown, this link or element consists of an arcuate pipe piece 24 which is provided with end flanges 25 for connection to corresponding end flanges 21 on adjoining ends of the hose 1. The pipe piece 24 may consist of a steel tube having a reinforced wall, to stand scrubbing and other influence from the environment. It may suitably have an internal diameter corresponding to the hose diameter, typically 20 - 24 inches, and may then suitably have an internal radius of curvature of about 6 m. As shown, a weight element 26 in the form of a chain is attached to the pipe piece. Several weight elements may be attached to the pipe piece, according to requirement. Further, a hydroacoustic transponder or position transmitter 27 is fixed to the pipe element. The purpose of this position transmitter will be further described below.

Fig. 4 shows the detail B in Fig. 1 on an enlarged scale and shows a side view of the coupling/weight unit 3. The unit comprises an end piece in the form of a distance and coupling piece 28 having a suitable flange 29 for connection to a pipe system on a vessel. To the flange 29 there is fixed a blind flange 30 to which there is fixed a chain length 31 for connection to the handling line 7 according to Fig. 1. The chain length possibly may be replaced by a lifting bridle, as shown in Figs. 5 and 6. Between the coupling piece 28 and the adjoining end of the hose 1, there is arranged a valve unit 32 in the form of a manually operated ball valve which may be opened and closed by means of a detachable handwheel 33.

If desired, with a view to a larger through-put or from other practical considerations, at this end of the hose there may be used two coupling/weight units instead of the single unit 3 in Fig. 4. The hose then will be branched off via a branch pipe to two end portions, for example having an internal diameter of 12 - 16 inches when it is the question of a hose having a diameter of 20 - 24 inches, whereby these end portions will be connected to associated end pieces and valves having detachable handwheels, in a corresponding manner as shown in Fig. 4. As shown in Fig. 4, the unit 3 is also provided with a hydroacoustic transponder or position transmitter 34 of a corresponding type and for a corresponding purpose as the position transmitter 27 for the weight/scrubbing link 5.

The illustrated embodiment of the coupling/weight unit 3 is intended for connection of the hose to a conventional tanker. In the present embodiment, the coupling piece 28 will be designed as, or be provided with, a weight means having a sufficient weight to keep the hose end in question stably in place at the seabed when the hose is in the storage position according to Fig. 1. Possibly, the coupling piece 28 may be provided with a weight unit in the form of an outer protecting casing, in a corresponding manner as in the embodiment according to Figs. 5-6.

Figs. 5 and 6 show the detail C in Fig. 1 on an enlarged scale and show a side view and a front view, respectively, of the coupling/weight unit 4. This unit comprises a hose end piece 38 which is intended for connection to a shuttle tanker. As shown, the end piece is provided with a protecting casing 39 which partly encloses the end piece, and which has a sufficient weight to keep the hose end stably in place on the seabed in the storage position according to Fig. 1. For safety reasons the casing 39 will be provided with a sparkless surface.

The end piece 38 is connected to the adjoining end of the hose 1 via a swivel unit 40. Further, to the end piece there are attached a pair of oppositely directed arms 41 to which there is attached a lifting bridle 42 for connection to the handling line 7 in question in Fig. 1 via a shackle 43.

As shown, the unit 4 is also provided with a hydroacoustic transponder or position transmitter 44 of a corresponding type and for a corresponding purpose as the transponders 27 and 34. The coupling/weight units 3 and 4 attached at each end of the hose and the middle weight link 5 ensure that the hose 1 is kept in place in its storage position at the seabed. The distance between these three anchor points 3, 4, 5 takes part in determining the geometry of the hose under water. In the stored position the hose will be liquid-filled, so that it is not squeezed by the water pressure. Because of its buoyancy, the hose between the end couplings and the weight link will assume a curved shape upwards in the body of water, so that it assumes a sinus-like shape in the storage position. This arrangement ensures that the "soft" parts of the hose do not come into contact with the bottom, something which means that the hose will be little exposed to damages and abrasion in the periods when it is stored. Thereby the hose is allowed to be lowered and stored without one having to examine the bottom conditions at the site in advance, which will be of great practical importance when using the equipment.

The method for transferring the loading hose from the storage position to a position of use in which the hose is connected between a loading and an unloading unit, will be described in the following with reference to Figs. 7-14. In this case it is supposed that the loading and unloading units consist of two tankers, more specifically a loading unit in form of a conventional barging vessel or tanker, and an unloading unit in the form of a shuttle tanker, the shuttle tanker coming from the field with a load which is to be transferred to the tanker. The first step of the method consists in that the upper end of one of the two handling lines is hoisted up and brought on board the shuttle tanker, whereafter the handling line is winched in and the hose end coupling connected to the line is coupled to the pipe system of the shuttle tanker. This step may be carried out either with or without the use of a tender. These alternatives are shown in Figs. 7 and 8. Fig. 7 shows a shuttle tanker 46 carrying out picking-up of the loading hose 1 directly, without the use of a tender. Such an operation presupposes good weather conditions. In this case, a grapnel with a shooting line is shot over the floating line 13, as illustrated with the arrow A_]? and the floating line 13 and the buoys 12 and 14 are lifted on board the shuttle tanker. Thereafter the handling line 7 is winched in, and the end coupling of the hose, i.e. the coupling/weight unit 4, is connected to the bow coupling of the shuttle tanker which is connected to the pipe system for loading/unloading.

In Fig. 8 there is used a tender 47 when picking up the loading hose 1. In this case the floating line 13 and the buoys 12 and 14 are picked up by the tender, and the buoys are released and placed on the deck of the tender, to be able to be transferred to the shuttle tanker later if this wants to have the possibility to disconnect itself from the buoy without assistance of the tender (see Fig. 13). Thereafter the tender moves to the side of the shuttle tanker 46 and "shoots" the handling line 7 over to the shuttle tanker by means of an airgun, as illustrated with the arrow A₂. Thereafter the handling line is winched in, and the hose end coupling is connected to the bow coupling of the shuttle tanker. As a next step in the method, the end of the other handling line 7 is taken on board the tender 47, in a manner corresponding to that described above. The tender thereafter uses the handling line to lift the hose end coupling 3 and the weight link 5 up from the sea or ocean bed. The hose 1 then hangs between the shuttle tanker and the tender, clear of the ocean bed. This situation is shown in Fig. 9. Thereafter the hose 1 is towed by means of the tender 47 to the place of the other tanker, the shuttle tanker 46 following at a suitable distance from the tender. This situation is shown in Fig. 10 wherein the tender approaches the other tank ship 48 which is presupposed to be a conventional tanker. The tender winches in the hose end piece 3 by means of the handling line, so that the chain or wire bridle 31 of the end piece can be reached from the deck of the tender. The end piece 3 then is located just aft of the stern of the tender. A messenger line from a midship crane 49 on the tanker 48 is received on board the tender, and the crane hook is lowered down so that the wire bridle of the end piece may be attached thereto. By means of the crane wire of the tanker 48, the hose is thereafter lifted onto the deck of the tanker and coupled to one or two of the manifold pipes 50 of the ship. This situation is shown in Fig. 11. The topical load can now be transferred from one vessel to the other.

A pair of stabilizing lines 51 suitably may be attached to the hose 1 at a distance of about 10 - 12 m from the hose end piece, and these are attached in a suitable manner to the deck of the tanker 48 on each side of the hose when this is attached to the manifold pipe 50, as suggested in Fig. 11. In this manner the hose is secured, inter alia, against unintended, horizontal and vertical movements because of the influence of the sea, both in the critical connecting phase and during the load transfer operation.

As suggested in Fig. 11, the tanker 48 is anchored by means of an anchor system 52 which is connected to the bow of the tanker. The anchoring system normally will be arranged so that the vessel can turn freely with the bow against the weather, so that its stern will follow a rotary circle C, as shown in Fig. 12.

When the hose 1 is connected as described above, the shuttle tanker, by the use of its dynamic positioning system (DP), will position itself at a distance and in a direction from the tanker agreed to in advance, so that the hose lies in a best possible and suitable depth and direction between the two vessels. The DP system then will see to it that the shuttle tanker at any time keeps itself at a definite distance and direction from the tanker during the transfer of the load from the shuttle tanker, as shown in Fig. 12. By means of the used weight link 5, the hose will hang approximately vertically in the sea, and consequently will not be so exposed to wind and waves as a hose floating at the surface.

Possibly uncontrolled excursions of the hind part of the tanker ("fishtailing") therefore will not imply that the hose may come into the propeller, etc. The hose will always be well clear of the main propeller, so that propeller propulsion (affward thrust) will be allowed during load transfer. The weight link will also have an acceleration-damping influence on the hose movements during choppy/heavy sea conditions.

As mentioned above, both the weight line 5 and the coupling/weight units 3 and 4 are equipped with respective position-giving transponders 27, 34 and 44. The purpose of these is to "communicate" with the shuttle tanker 46 and the tender 47, so that these may have indicated the accurate position of the hose and the hose end pieces. Also the tanker 48, when required, may get information about the position of the hose during a load transfer operation. The position indication of the hose will be a vital information in connection with picking-up of the hose, and also for other marine traffic (trawlers etc.).

After terminated load transfer and in anticipation of a new shuttle tanker, the shuttle tanker 46 disconnects itself from the hose, and while the shuttle tanker goes slowly aftwards, it lays the hose carefully down onto the seabed 6 by means of the handling line 7, as shown in Fig. 13.

The hose 1 will now lie connected to the tanker 48 with the weight/scrubbing link 5 and the coupling/weight unit 4 laying on the seabed at a mutual distance causing the intermediate part of the hose 1 to assume an arcuate shape upwards in the body of water. This situation is shown in Fig. 14. At arrival of the next shuttle tanker this can, if allowed by the weather, shoot a grapnel (not shown) over the floating line 13 (as illustrated with the arrow A₃) and haul this up on the deck so that the handling line 7 may be used to winch in the hose end piece and couple this to the bow coupling of the shuttle tanker. If the weather does not allow the shuttle tanker itself to pick up the floating line and the handling line, this operation will be carried out means of the tender 47.

When the tanker 48 is fully loaded, the hose handling sequences are reversed, and the hose is brought back to its storage position according to Fig. 1. After the load transfer operation has been accomplished and the two vessels have been disconnected from each other, the shuttle tanker will return to the field to fetch a new load, whereas the tanker will go to the destination for the load.

It is to be remarked that even if the method according to the invention has been described above in connection with hose connection between a tanker and a shuttle tanker, the invention of course may also find application in other offshore loading operations. For example, the hose arrangement will be able to be used for the transfer of oil directly from an oil-producing platform to a shuttle tanker.

Claims

P a t e n t C l a i m s

1. Equipment for storage of a loading hose (1) in a body of water (2), wherein the hose (1) has a specific gravity which is less than one, characterized in that it comprises a pair of combined coupling and weight units (3, 4) which are coupled to a respective end of the hose (1) and are adapted to rest on the seabed (6), each unit (3 resp. 4) comprising an end piece (28, 38) for connection to a pipe system on a vessel, and a weight means (39) of a sufficient weight to keep the hose end stably in place on the seabed (6), a weight/scrubbing link (5) mounted on the hose (1) at a middle region thereof, and a pair of handling lines (7) connected at one end to a respective one of the coupling/weight units (3, 4), and connected at their other end to a buoy means (8) at or on the water surface (9), the coupling/weight units (3, 4) and the weight/scrubbing link (5) in use being placed on the seabed (6) at such a mutual distance that the intermediate parts of the hose (1) because of their buoyancy will stand like an arc upwards in the body of water (2).

2. Equipment according to claim 1, characterized in that the weight means for at least one of the coupling/weight units (3, 4) is constituted by a protective casing (39) which partly encloses the associated end piece (38).

3. Equipment according to claim 2, characterized in that a swivel unit (40) is arranged between the end piece (38) and the appurtenant end of the hose (1).

4. Equipment according to one of the preceding claims, characterized in that one of the coupling/weight units (3) is provided with a manually operable closing valve (32).

5. Equipment according to one of the preceding claims, characterized in that the weight/scrubbing link (5) is formed from an arcuate pipe piece (24) which, at its ends, is provided with flanges (25) for connection to corresponding end flanges (21) on adjoining ends of the hose (1), and to which there is attached one or more weight elements (26).

6. Equipment according to claim 5, characterized in that the hose (1) consists of a plurality of segments (20) having end flanges (21) for mutual interconnection, and which are formed from an inner hose wall (22) which is covered by an outer layer (23) of a buoyancy material.

7. Equipment according to claim 6, characterized in that the inner hose wall (22) consists of rubber and the outer layer (23) consists of a suitable plastic material, such as polyester.

8. Equipment according to one of the preceding claims, characterized in that the weight/scrubbing link (5) is provided with a transponder (27) for depth and position indication.

9. Equipment according to claim 8, characterized in that also at least one of the coupling/weight units (3 resp. 4) is provided with a transponder (34 resp. 44) for depth and position indication.

10. A method of transferring a loading hose (1) from a storage position in a body of water (2) to a position of use in which the hose is connected between a loading and an unloading unit, e.g. two tankers (46, 48), the ends of the hose (1) in the storage position being connected to respective coupling/weight units (3, 4) resting on the seabed (6) and being connected to the lower ends of respective handling lines (7) of which the upper ends are connected to buoy means (8) at the water surface, and a weight link (5) also resting on the seabed being arranged at the middle of the hose, characterized by the steps that the upper end of one of the two handling lines (7) is hoisted up and brought on board one (46) of the two tankers, whereafter the handling line is winched in and the hose end coupling (3; 4) connected to the line is coupled to the pipe system of the vessel (46), s that the upper end of the other handling line (7) is taken on board a tender (47) so that the hose end coupling (3; 4) connected to the line and the weight link (5) are lifted up from the seabed and the hose (1) hangs between the first tanker (46) and the tender (47), that the hose (1) by means of the tender (47) is towed to the place of the second tanker (48), the first tanker (46) following at a suitable distance from the tender, o that the second handling line (7) is winched on board the tender (47) and the hose end coupling (3; 4) in question is connected to a line from a lifting crane (47) on the second tanker (48), and that the hose end coupling (3; 4) and the hose (1) are hoisted on board the second tanker (48) and the end coupling is coupled to the pipe system (50) of the vessel, so that 5 the topical load can be transferred from one vessel to the other.