US3921557A

US3921557A - Floating storage unit

Info

Publication number: US3921557A
Application number: US443541A
Authority: US
Inventors: Steven A T Kapteijn; John H Raynes
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1973-03-01
Filing date: 1974-02-19
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: FR2230544B1; JPS49116837A; FR2230544A1; CA976812A; NO141321B; GB1422416A; NO141321C; NL171881C; DE2360213A1; DE2360213C2; JPS5643955B2; IT999877B; NL171881B; ES421090A1; NL7316501A; SE390011B; AU6314173A

Abstract

A floating oil storage unit of the water-displacement type, provided in the upper portion with a water separator, and being provided with a central pipe riser adapted to be connected by a flexible pipe to an ocean floor pipeline or manifold.

Description

' United States Patent Kapteijn et al.

[ Nov. 25, 1975 FLOATING STORAGE UNIT Inventors: Steven A. T. Kapteijn; John H.

Raynes, both of The Hague, Netherlands Assignee: Shell Oil Company, Houston, Tex.

Filed: Feb. 19, 1974 Appl. No.: 443,541

Foreign Application Priority Data Mar. 1, 1973 United Kingdom. 9932/73 US. Cl. 114/.5 T; 9/8 P; 141/387 Int. Cl. B63B 35/44 Field of Search 114/.5 T; 9/8 P; 61/46,

References Cited UNITED STATES PATENTS 1/1960 Sheiry 141/388 3,434,442 3/1969 Manning 9/8 P 3,540,397 1/1969 Burns 114/.5 T

3,602,175 8/1971 Morgan r 9/8 P 3,675,680 10/1970 Frohlich et a1.. 141/387 3,677,310 7/1972 Dobler 141/388 3,753,494 8/1973 Hirata 114/.5 T

Primary Examiner-Trygve M. Blix Assistant ExaminerSherman D. Basinger [57] ABSTRACT A floating oil storage unit of the water-displacement type, provided in the upper portion with a water separator, and being provided with a central pipe riser adapted to be connected by a flexible pipe to an ocean floor pipeline or manifold.

4 Claims, 7 Drawing Figures UuS Patant Nov. 25, 1975 Sheet20f2 3,921,557

FLOATING STORAGE UNIT BACKGROUND OF THE INVENTION The invention relates to a storage unit adapted to float in water, in particular for storing crude oil produced from an oil field in the seabottom.

The invention relates in particular to a storage unit of the displacement type as described in applicants U.S. Pat. No. 3,360,810, which was published on July 20, 1966.

The above mentioned known storage unit is of the displacement type which means that if storage liquid, for example oil, is introduced into the liquid storage vessel of the storage unit, water, present in the liquid storage vessel will be displaced by the oil so that the water will leave the liquid storage vessel and flow into the water in which the storage unit is floating. Conversely, when oil is removed from the liquid storage vessel, water in which the storage unit is floating will enter the liquid storage vessel and will occupy the place originally occupied by the oil.

Since direct contact exists between the storage liquid, normally oil, and the water in the storage unit, there is some risk of water pollution.

SUMMARY OF THE INVENTION In order to exclude any such risk, a storage unit of the above kind is proposed, according to the invention, comprising a liquid storage vessel of the water displacement type and a separator for separating traces of the storage liquid from water leaving the liquid storage vessel.

In a suitable embodiment of the storage unit, accord ing to the invention, the separator is arranged in the upper part of the storage unit, the separator being cnnected by a conduit to the lower part of the interior of the liquid storage vessel. This conduit serves for supplya ing the water leaving the liquid storage vessel to the separator.

The invention relates furthermore to a method and means for creating a fluid communication between the liquid storage vessel of the floating storage unit and a submarine pipeline.

The said method comprises according to the invention the following steps:

a. lowering a riser conduit carrying a hose at its lower end, the free end of said hose being provided with a hose connector, the riser conduit being guided along a riser guide track and the hose connector being guided along a hose connector guide track, both tracks extending vertically along or through the storage unit;

b. after the hose connector has reached the lower end of the hose connector guide track, further lowering the riser conduit together with the hose and guiding the hose connector further downwardly along a wire line extending vertically between the lower part of the hose connector guide track and a manifold on the seabottom which is in communication with a submarine pipeline;

c. continuing the lowering of the riser conduit and the hose until the hose connector has reached the manifold;

d. coupling the hose connector to the manifold;

e. further continuing the lowering of the riser conduit until the hose has assumed a lateral curvature.

BRIEF DESCRIPTION OF DRAWING The invention will be further explained with reference to the drawings, wherein:

FIG. 1 shows very schematically a side view of the storage unit;

FIG. 2 shows the lower part of the storage unit before the installation of the riser conduit and the hose;

FIG. 3 shows the hose while being lowered;

FIG. 4 shows the hose at the moment that the hose connector has reached the level of the bottom of the storage unit;

FIG. 5 shows the hose and the riser conduit at the moment that the hose connector is guided along the wire line;

FIG. 6 shows the hose and the riser conduit after the hose connector has been coupled to the manifold;

FIG. 7 shows the riser conduit and the hose after these elements have reached the desired positions.

In FIG. 1 the storage unit is generally indicated by the reference numeral 4. It comprises essentially an elon gated liquid storage vessel 5, and a superstructure 7. The storage unit 4 is provided with buoyancy tanks 6 and with solid ballast (not shown) so arranged that the unit can be kept floating in the water 1 with its major axis disposed in a vertical plane.

The superstructure 7, which extends above the watersurface 2, carries a platform 8. On top of the platform 8 a circular rail 12 is present. The rail 12 carries a turntable 9 by means of supports 13, provided with wheels 14, running along the rail 12. A helicopter deck 10 and a crane 15 are arranged on the turntable 9.

A loading boom 16 is present on the turntable 9, comprising a pipe 17 and a steel supporting structure 18. The inboard end of the loading boom 16 is connected to the turntable 9 by means of a hinge 19, in such a manner that it can swing in a vertical plane.

A crane boom 20 is arranged in the same vertical plane as the loading boom 16. The crane boom 20 is secured with its inboard end to the turntable 9 by means of a hinge 21 in such a manner that it can swing in said vertical plane. A cable 22 serves for topping the crane boom 20. A further cable 23, led along the crane boom 20, is secured to the outboard end of the loading boom 16.

To the outboard end of the loading boom 16, a hose 24 is secured by means of a swivel 25 for making a fluid communication between a tanker 26 and the loading boom 16.

A fluid conduit is furthermore present for making a fluid communication between the inboard end of the loading boom 16 and the upper part of the interior of the elongated liquid storage vessel 5. The last mentioned fluid communication comprises a pipe 27, a pipe-swivel 28 allowing rotation around a vertical axis, two

parallel pipes

29 and 30, two

pipes

31 and 32,

pumps

33 and 34 and

pipes

35 and 36. Each of the

pipes

35 and 36 debauches into the upper part of the interior of the liquid storage vessel 5. The pipe 27 is connected by means ofa pipe swivel (not shown) to the inboard end of the pipe 17 in such a manner that the fluid communication between pipe 17 and pipe 27 is maintained when the loading boom 16 swings in a vertical plane.

The turntable 9 is furthermore provided with a mooring cable or chain 37 for connecting the bow of the tanker 26 to the storage unit as shown.

On the water bottom 3 a submarine pipeline 38 is present. The pipeline 38 is connected to a manifold 39 arranged on the bottom 3. The manifold 39 is connected by means of a pair of

hoses

40 and 41, respectively to a pair of

riser conduits

42 and 43 respectively. The said

riser conduits

42 and 43 run upwardly through a central hole 44 extending axially through the storage unit 4.

For the sake of clarity only the lower part of the

riser conduits

42 and 43 are shown in the drawings. However, said riser conduits run upwardly through the hole 44 and debouch into the upper part of the interior of the liquid storage vessel 5.

A pair of

separators

50 and 51 are arranged within the superstructure 7. These separators are conventional oil/water separators, for example the well-known parallel-plate separators or the well-known corrugated plate separators.

Each separator 50, respectively 51, is connected by means of a conduit 52, respectively 53, to the lower part of the interior of the liquid storage vessel 5. Furthermore each separator 50, respectively 51, is connected by means ofa conduit 54, respectively 55, to the upper part of the interior of the liquid storage vessel 5. Finally each separator 50, respectively 51, is provided with a conduit 56, respectively 57, leading to the surrounding water 1, which is present as well within axial hole 44. Each of the conduits 56, respectively 57, is provided with a pump 58, respectively 59.

OPERATION OF THE DEVICE The operation of the storage unit 4 will be explained below.

The storage unit 4, which is ballasted in a suitable manner so as to keep it floating with its major axis in a vertical plane in the manner as shown in FIG. 1, is anchored by means of anchor cables and anchors (not shown). When oil is not yet stored in the unit, the liquid storage vessel 5 is completely filled with water. Oil produced from an offshore oil field in the neighborhood flows through submarine pipeline 38 and manifold 39 through one of the

hoses

40 or 41 to one of the

riser conduits

42 or 43. Normally only one of the

hoses

40 or 41 and only one of the

corresponding riser conduits

42 or 43 is used at a time, the other service as a spare. However, if desired, both

conduits

42 and 43 could be used at the same time. The oil flows upwardly through the riser conduit 42 and/or 43 and to the upper part of the interior of the liquid storage vessel 5. The oil entering the upper part of the interior of the liquid storage vessel 5 will displace the water present in the liquid storage vessel 5. The water, displaced by the oil entering the liquid storage vessel 5, will flow through conduit 52, respectively 53 upwardly to oil/water separator 50, respectively 51. Of course the oil in the vessel 5 will float on top of the water present in vessel 5, since oil has a lower density than water. Since the displaced water leaves the vessel 5 near the bottom 60 of the vessel 5, the chance that the water leaving the vessel 5 contains some oil is small, but it is not impossible. Therefore the water leaving the vessel 5 is passed through the oil/water separators 50, respectively 51. In the separators any oil present is separated from the water. The oil separated is led through a conduit 54, respectively 55, to the upper part of the interior of the liquid storage vessel 5 to be stored therein. Clean water leaves separator 50, respectively 51, via conduit 56, respectively 57. A pump 58 respectively 59, pumps the clean water to the water 1 in which the storage unit 4 is floating.

The storage unit 4 is used for temporarily storing therein crude oil produced from an offshore oilfield in the neighborhood. When the liquid storage vessel 5 is completely filled, or nearly completely filled, with oil, an export-tanker will moor to the storage unit 4, in order to be loaded with oil from the storage vessel 5. For this purpose the mooring cable or chain 37 is connected to the bow of the tanker 26 as shown in FIG. 1. Then the loading boom 16 is brought in the right position and the hose 24 is connected to a manifold (not shown) on the tanker 26.

Then valves (not shown) in the conduits 56, respectively 57 are opened and valves (not shown) in the con duits 54, respectively 55, are closed. so that surrounding water 1 can enter the lower part of the interior of the liquid storage vessel 5 via conduit 56, pump 58, separator 50 and conduit 52, respectively via conduit 57, pump 59, separator 51 and conduit 53.

Pump 33, respectively pump 34, pumps the oil through

conduits

35 and 29, respectively

conduits

36 and 30, the pipe swivel 28, conduit 27, pipe 17 of loading boom 16, pipe swivel 25 and finally through hose 24 to the tanker 26. When oil is removed from the storage vessel 5, water will enter it following the path as mentioned earlier.

When the tanker 26 has loaded the desired quantity of oil, the hose 24 is disconnected from the tanker 26, the loading boom 16 is raised by means of the crane boom 20 and the

cables

22 and 23, so that the hose 24 will not contact the water 1. Thereafter the mooring cable 37 is disconnected from the tanker 26 and the tanker is ready to sail away.

Preferably a control system (not shown) is present for paying out or hauling in the cable 23 led along the crane boom 20 in dependence of the tension measured in the cable 23, so that the movements of the ship 26 are automatically followed and overstressing or damage to the hose 24 because of movements of the ship 26 is prevented.

The storage unit 4 is provided with

riser conduits

42 and 43 as described. The special way of installing the said riser conduits and the manner of making a fluid connection between these riser conduits and the submarine pipeline 38 will be explained below.

In the axial central hole 44 of the storage unit a guide track is present for each riser 42 respectively 43. In FIGS. 2 through 7 only the riser guide track 65 of riser 42 is shown. This riser guide track is indicated schematically by a dotted line. Furthermore in the axial central hole 44 a guide track is present for the connector of each hose 40 respectively 41. In FIGS. 2 through 7 only the hose connector guide track 66 of the hose 40 is shown. This hose connector guide track 66 is indicated schematically by a dotted line.

For making the fluid connection the hose 40 is lowered through the central hole 44. At its lower end the hose 40 is provided with a hose connector 67. The hose connector 67 is guided along the hose connector guide track 66 when the hose 40 is lowered. FIG. 3 shows the hose connector 67 and hose 40 while being lowered. FIG. 4 shows the hose connector 67 at the moment that it has reached the level of the bottom of the storage unit. After the hose connector 67 has reached the said level it will leave the hose connector guide track 67, when lowered further and it will be guided further by a guideline 68 arranged between the storage unit 4 and the manifold 39. In FIG. 5 the hose connector 67 is shown at the moment that it has reached an intermediate position between the manifold 39 and the bottom 60 of the storage unit 4. The hose connector 67, hose 40, and riser 42, which is secured to the top end of hose 40, is lowered further until it reaches connector element 69 on the manifold 39. Then hose connector 67 and connector element 69 are interconnected and a fluid communication is made between the hose 40 and the manifold 39. The riser 42, which is lowered together with the hose 40, follows the riser guide track 65. As shown in the drawings 2 through 6, the lower part of the riser guide track 65 is inclined somewhat so that the riser 42 can be finally displaced laterally in the manner as shown in FIG. 6. This is also made possible by a flexible joint 70 present in the riser 42. This lateral displacement of the riser 42 causes lateral curvature of the hose 40 as shown in- FIG. 6. When the riser 42 is lowered further until the lower end of riser 42 reaches the level of the bottom 60 of the storage unit 4 the hose 40 will be curved as shown in FIG. 7. FIG. 7 shows the final position of riser 42 and of hose 40. Now the riser 42 and the hose 40 are ready for use. It will be clear that the second riser 43 and the second hose 41 can be installed in the same manner.

Since the

hoses

40 and 41 are laterally curved, as clearly shown in FIG. 1, the storage unit 40 can freely move upwardly, downwardly and laterally without risk of damage to the said hoses.

We claim as our invention:

1. A storage unit adapted to float in water with a major portion thereof positioned below the waterline, in particular for storing crude oil, comprising a riser guide track extending vertically through the storage unit, a riser conduit which is axially displaceable along said riser guide track extending axially through the storage unit, a flexible hose secured to the lower end of the riser conduit and extending to the ocean floor, a hose connector guide track extending axially through the storage unit and a hose connector securedto said hose and extendable along said hose connector guide track through said storage unit.

2. The storage unit as claimed in claim 1, wherein the lower end of the riser conduit is connected by the hose to a submarine pipeline and the upper end of the riser conduit is connected by a conduit to the upper part of 6 the interior of the liquid storage vessel, said hose having a lateral curvature.

3. A storage unit adapted to float in water, in particular for storing crude oil. comprising a verticallyelongated closed-bottom liquid storage vessel of the dis placement type having a major portion of its height submerged in the water, and an oil and water separator contained within said vessel for separating traces ofthe storage liquid from all of the displaced water leaving the liquid storage vessel, said storage unit including a superstructure extending above the level of the water in which the storage unit is floating during normal use, a turntable on top of the superstructure, a loading boom secured with its inboard end to the turntable in such a manner that it can swing in a vertical plane, a hose secured to the outboard end of the loading boom for making a fluid communication between a ship and the loading boom, and a fluid conduit for making a fluid communication between the inboard end of the loading boom and the upper part of the interior of the liquid storage vessel.

4. A storage unit adapted to float in water, in particular for storing crude oil, comprising a vertically-elongated closed-bottom liquid storage vessel of the displacement type having a major portion of its height submerged in the water, and an oil and water separator contained within said vessel for separating traces of the storage liquid from all of the displaced water leaving the liquid storage vessel, said storage unit including a superstructure extending above the level of the water in which the storage unit is floating during normal use, a turntable on top of the superstructure, a loading boom secured with its inboard end to the turntable in such a manner that it can swing in a vertical plane, a hose secured to the outboard end of the loading boom for making a fluid communication between a ship and the loading boom, and a fluid conduit for making a fluid communication between the inboard end of the loading boom and the upper part of the interior of the liquid storage vessel, said loading boom being supported by a crane boom and a cable led along the crane boom, the crane boom being arranged in the same vertical plane as the loading boom, and the cable led along the crane boom secured to the outboard end of the loading

Claims

1. A STORAGE UNIT ADAPTED TO FLOAT IN WATER WITH A MAJOR PORTION THEREOF POSITIONED BELOW THE WATERLINE, IN PARTICULAR FOR STORING CURDE OIL, COMPRISING A RISER GUIDE TRACK EXTENDING VERTICALLY THROUGH THE STORAGE UNIT, A RISER CONDUIT WHICH IS AXIALLY DISPLACED ALONG SAID RISER GUIDE TRACK EXTENDING AXIALLY THROUGH THE STORAGE UNTIL, A FLEXIBLE HOSE SECURED TO THE LOWER END OF THE RISER CONDUIT AND EXTENDING TO THE OCEAN FLOOR A HOSE CONNECTOR GUIDE TRACK EXTENDING AXIALLY THROUGH THE STORAGE UNIT AND A HOSE CONNECTOR SECURED TO SAID HOSE AND

2. The storage unit as claimed in claim 1, wherein the lower end of the riser conduit is connected by the hose to a submarine pipeline and the upper end of the riser conduit is connected by a conduit to the upper part of the interior of the liquid storage vessel, said hose having a lateral curvature.

3. A storage unit adapted to float in water, in particular for storing crude oil, comprising a vertically-elongated closed-bottom liquid storage vessel of the displacement type having a major portion of its height submerged in the water, and an oil and water separator contained within said vessel for separating traces of the storage liquid from all of the displaced water leaving the liquid storage vessel, said storage unit including a superstructure extending above the level of the water in which the storage unit is floating during normal use, a turntable on top of the superstructure, a loading boom secured with its inboard end to the turntable in such a manner that it can swing in a vertical plane, a hose secured to the outboard end of the loading boom for making a fluid communication between a ship and the loading boom, and a fluid conduit for making a fluid communication between the inboard end of the loading boom and the upper part of the interior of the liquid storage vessel.

4. A storage unit adapted to float in water, in particular for storing crude oil, comprising a vertically-elongated closed-bottom liquid storage vessel of the displacement type having a major portion of its height submerged in the water, and an oil and water separator contained within said vessel for separating traces of the storage liquid from all of the displaced water leaving the liquid storage vessel, said storage unit including a superstructure extending above the level of the water in which the storage unit is floating during normal use, a turntable on top of the superstructure, a loading boom secured with its inboard end to the turntable in such a manner that it can swing in a vertical plane, a hose secured to the outboard end of the loading boom for making a fluid communication between a ship and the loading boom, and a fluid conduit for making a fluid communication between the inboard end of the loading boom and the upper part of the interior of the liquid storage vessel, said loading boom being supported by a crane boom and a cable led along the crane boom, the crane boom being arranged in the same vertical plane as the loading boom, and the cable led along the crane boom secured to the outboard end of the loading boom.