U.S. patent number 3,654,951 [Application Number 05/051,426] was granted by the patent office on 1972-04-11 for liquid storage facility including self-actuating discharge conduit.
This patent grant is currently assigned to Texaco Inc.. Invention is credited to Paul D. Carmichael, Ivo C. Pogonowski.
United States Patent |
3,654,951 |
Pogonowski , et al. |
April 11, 1972 |
LIQUID STORAGE FACILITY INCLUDING SELF-ACTUATING DISCHARGE
CONDUIT
Abstract
The invention relates to an underwater storage facility
particularly adapted for holding a hydrocarbon liquid having a
specific gravity less than the specific gravity of water. The
facility includes a liquid storage tank fixedly positioned beneath
the water's surface usually at the ocean floor. A network of
conductors communicates the storage tank with one or more offshore
wells whose production is delivered to the tank. A discharge
conduit communicated with said tank, when in operating position
extends to the water's surface. When in a non-operating position,
the conduit is coiled into a compact bundle at the tank whereby to
be beyond the reach of floating vessels, and yet not subject to
abrasive wear at the ocean's floor.
Inventors: |
Pogonowski; Ivo C. (Houston,
TX), Carmichael; Paul D. (Houston, TX) |
Assignee: |
Texaco Inc. (New York,
NY)
|
Family
ID: |
21971239 |
Appl.
No.: |
05/051,426 |
Filed: |
July 1, 1970 |
Current U.S.
Class: |
137/355.16;
138/119; 137/236.1; 141/279 |
Current CPC
Class: |
B65D
88/78 (20130101); B65D 88/54 (20130101); Y10T
137/6918 (20150401); Y10T 137/402 (20150401) |
Current International
Class: |
B65D
88/78 (20060101); B65D 88/54 (20060101); B65D
88/00 (20060101); B65h 075/38 () |
Field of
Search: |
;141/387,388
;138/103,118,119,178 ;291/294 ;137/355.16-355.28,615,236 ;9/8
;141/279,284 ;61/46,46.5 ;166/.5 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
2970646 |
February 1961 |
Knapp et al. |
2648201 |
August 1953 |
Marancik et al. |
|
Primary Examiner: Bell, Jr.; Houston S.
Claims
We claim:
1. In an underwater facility for storing a hydrocarbon liquid
having a specific gravity not exceeding the specific gravity of
water, and being immersed at an offshore location, said facility
including;
a liquid holding storage tank positioned beneath the water's
surface at said offshore location and being fixed to the ocean
floor,
piping means communicating said liquid holding storage tank with at
least one source of said hydrocarbon liquid,
conductor means having opposed upper and lower ends for directing
said liquid from said liquid holding storage tank to a floating
vessel, said conductor means including,
an elongated resilient discharge conduit having said lower end
communicated with said storage tank and being of sufficient length
to dispose the upper end thereof beyond the water's surface, and
said discharge conduit being adjustable between an extended
position with said upper end disposed beyond the water's surface,
and a retracted position, wherein said upper end is immersed
beneath said surface,
flow control means carried on said conduit and being operable to
regulate the liquid flow therethrough, and
means for controllably adjusting said conduit between said
retracted and extended positions and comprising, valve means
disposed at said discharge conduit lower end and being actuatable
to selectively deliver a stream of crude oil or water to said
discharge conduit lower end.
2. In an underwater facility as defined in claim 1 including;
control means connected to said valve means and being operable to
regulate said valve means from the water's surface to remotely
regulate the disposition of said discharge conduit between said
extended and retracted positions.
3. In an underwater facility as defined in claim 1 wherein said
discharge conduit includes; a flexible walled cylindrical member
having longitudinally extending retracting means incorporated
therein.
4. In an underwater facility as defined in claim 3 wherein said
retracting means includes; an elongated spring member imbedded
longitudinally in a wall of said conduit.
5. In an underwater facility as defined in claim 3 wherein said
elongated spring member includes; a metallic strip imbedded along
one wall of said conduit and being prestressed to normally urge the
spring into a coiled disposition.
6. In an underwater facility as defined in claim 3 wherein; said
discharge conduit is formed of a non-metallic resilient
material.
7. In an underwater facility as defined in claim 6 wherein; said
material is nylon.
Description
BACKGROUND OF THE INVENTION
In the continuing search for new crude oil sources in offshore
water, the depth of the latter is progressingly increasing as the
search goes further offshore. With the increased water depth,
usually the distance from a refinery or other land based storage
terminal or refinery increases. It has been found expedient,
particularly in the instance of remotely positioned offshore oil
fields, to at least partially process and store the field's
production until it can be removed by tanker, barge or other
vessel.
Since a pipeline to such a field usually involves great expense and
is non-salvageable, economic factors demand that such a facility be
practical both from an operating point of view, and be mobile to
insure an extended life.
At least one problem associated with all equipment used in offshore
oil operations is the exposure of such equipment to the elements.
Further, the equipment is frequently located at the water's surface
and thereby constitutes a navigational hazard.
As the water depth increases, such underwater facilities become
increasingly difficult to operate. This is due primarily to the
present sparsity of technology related to great water depths, and
the inability to provide personnel to maintain and operate such a
facility. Notably, when the water depth exceeds convenient diver
access depth, the entire unit must be operated remotely or with the
aid of submersible vessels.
Of further consideration, surface based facilities are not only
exposed to weather conditions such as wind and turbulent waters,
but such exposure increases the possibility of accidental pollution
of the surrounding environment. When however, a storage and/or
processing facility is submerged and positioned at or near the
ocean floor, a wear problem is introduced by movement of the
facility such as connecting lines and pipes across the ocean floor,
which movement tends to abrade the latter through constant rubbing
against the floor. When the floor is primarily sandy, it can be
appreciated that abrasive wear will be quite severe.
Toward overcoming the above delineated problems and operating
conditions in offshore waters, there is here provided a novel
storage facility adapted to be submerged beneath the ocean's
surface and preferably anchored to the floor thereof. The facility
includes at least one storage tank having a base adapted to be
fixedly positioned at the ocean floor by piling, anchoring or other
means. The tank is communicated with the water's surface by an
elongated conductor means comprising a resilient, or flexible
discharge conduit. The latter not only extends toward the surface,
for discharging crude oil, but when not being used is coiled into a
compact convenient bundle for convenient storage above the ocean
floor beyond reach of abrasive and wearing elements.
DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 illustrates a facility of the type contemplated including a
storage tank communicated with a surfaced vessel by means of a
resilient discharge conduit.
FIG. 2 is similar to FIG. 1, showing the flexible conduit in the
contracted position.
FIG. 3 is similar to FIGS. 1 and 2, illustrating the flexible
conduit in a state of partial erection.
FIG. 4 is a segmentary view on an enlarged scale and in
cross-section showing the top portion of the storage tank.
FIG. 5 is a segmentary view in partial cross-section and on an
enlarged scale showing the upper end of the flexible conduit.
FIG. 6 is a cross-section taken along the line 6--6 in FIG. 4.
FIG. 7 is a cross-sectional view along line 7--7 in FIG. 6.
Referring to FIG. 1, the contemplated underwater storage facility
10 is shown in the preferred operating position whereby a stream of
hydrocarbon liquid such as crude oil is delivered through a
flexible discharge conduit 15 to a surface based tanker 11. A
storage tank 12 is mounted to a foundation pad 13 which in turn is
fixed to the ocean floor by peripherally disposed piles 14. The
latter are at least partially imbedded into the substratum and
connected at the upper end thereof to pad 13. In any event, tank 12
is rigidly held to avoid being buoyed upwardly, or displaced
laterally.
Storage tank 12 is communicated by a distribution network of
conductors 16 and 17 that extend from the tank lower end to
remotely positioned well heads 18 and 19. The latter, in the manner
of such wells, extend into the substratum and are provided at the
upper ends with the usual control equipment to choke down the
pressurized flow of liquid and gases being emitted from the wells.
While not presently shown, the distribution network further
includes means for separating gas from the liquid product whereby
the separate streams can be passed to appropriate facilities.
As shown in FIG. 1, the interior of liquid storage tank 12 is
communicated with the surrounding water whereby to stabilize
internal pressure. Further, said arrangement facilitates the
creation of a water-oil interface within the tank whereby solids
will tend to separate by gravity flow from the crude oil and fall
to the tank floor. The liquid distribution system further includes
one or more internal manifolds such as lead in pipes 21 that
introduce flows of crude oil to the upper end of the tank whereby
to displace water and form a pool at the tank top. At the oil pool
increases in volume the resulting water-oil interface will be
depressed further toward the tank floor.
The unit functions on the presumption, as is normally the instance,
that the hydrocarbon fluid or crude oil passing from the various
wells will have a specific gravity less than the surrounding
environment, which is normally sea water. Further, and as
previously mentioned, hydrocarbon product removed from the
respective wells 18 and 19 will be preseparated into liquid and
gaseous phases whereby substantially the entire content of tank 12
will be in liquid form.
The storage facility is usable at virtually any depth of water.
However, its most desirable features are accentuated in the
instance of relatively deep waters of 300 feet and deeper, which
depth exceeds normal diver access depth.
Base member 13 comprises a relatively rigid foundation pad formed
of steel or reinforced concrete, which is prefabricated at the
water's surface and floated into position. To facilitate use and
subsequent salvage of tank 12, base 13 can be provided with
buoyancy means such as internal buoyancy tanks communicated with a
suitable pumping system for controllably regulating the buoyancy of
the unit.
The periphery of foundation pad 13 includes means such as funnel
piece 23 to guide the respective piles 14 into the substratum
wherein the tank will be retained. Such piles are in the normal
manner positioned about the tank and subsequently driven into the
substratum by pile driving means at the water's surface. The piles
are then cemented or otherwise fastened to the foundation pad.
Tank 12 is supportably positioned on the foundation pad 13 and
connected to the latter in such manner as to prohibit movement
therebetween. As shown, the tank 12 may comprise in essence a rigid
steel or reinforced concrete hemispherical shell having openings 24
spaced about the lower end thereof to communicate the shell
interior with the surrounding water. Since the stored crude oil
will exert a substantial buoying effect on the tank 12 top wall,
the latter must be of sufficient strength and thickness to
withstand tensional stresses introduced into the tank walls.
Tank 12 can be fabricated of a non-rigid material such as a
reinforced resilient plastic or the like. The latter however would
limit the size of a tank in view of the upward force exerted by
stored oil particularly when the tank is in a full condition.
Tank 12 can also be fabricated of a rigid material such as
reinforced concrete in the form of a hemisphere as presently shown,
or an appropriate geometric shape best adapted to withstand the
pressures at the subsea location as well as the internal pressures
exerted by the upward lift of the stored crude oil. The upper end
of tank 12 is provided with cap means 26 to accommodate flexible
discharge conduit 15 which is extendable to the water's
surface.
Referring to Figure 4, the upper end of tank 12 is provided with a
cap 26 having a central body from which a peripheral rim 27 extends
upwardly. Said rim 27 is adapted to receive and form a fluid tight
annular seal with the wall of flexible conduit 15. As shown,
conduit 15 is closely fitted against the rim outer edge and held in
place by a peripheral clamping means 28 such as a circular,
contractable ring having intermittent means to tighten the ring
into sealing contact with conduit 15.
A central passage means 29 formed in said cap 26, communicates the
interior of tank 12 with the upper positioned conduit 15. Flow
control valve means disposed in said passage means 29 includes in
the instant arrangement, an actuatable closure element 31 having a
lateral valve actuator 32 extending therefrom to the cap exterior.
The actuator is provided with transmission means communicated with
the water's surface whereby said control valve 31 can be remotely
controlled through a hydraulic, electrical or mechanical medium.
Preferably, and from a safety point of view, actuation of control
valve 31 embodies at least two optionally usable systems whereby
the unit can still be operated in the event that one of the control
facilities should become inoperable.
A second valve 33 disposed within cap 26 includes an inlet opening
34 communicated with the surrounding water such that the outlet is
communicated with the conduit 15 interior. Thus, conduit 15 can be
communicated with an external source of water by actuation of said
valve 33 to open position. The latter functions primarily for
flushing or purging conduit 15 of crude oil at such time as the
latter is to be returned to its retracted position at the ocean
floor.
Third valve means embodied in the cap 26 includes a pressure
sensitive safety valve 36. Said valve is arranged such that an
undue build-up of pressure within the tank 12 will automatically
actuate the normally closed valve 36 to open position. Thus, with
the excessive build-up of pressure within tank 12, safety valve 36
will be automatically opened to pass a flow of crude oil into
conduit 15 rather than have the tank filling beyond its capacity
with the undesired consequence of prompting a water polluting
situation.
Conduit 15 as mentioned herein, is constructed as to permit said
member to assume either an extended or retracted position. In the
retracted position as shown in FIG. 2, conduit 15 is in essence
coiled upon itself and supported at the upper side of the tank 12.
When so positioned, conduit 15 is submerged well below the surface
of the water and consequently will not constitute a navigational
hazard.
Said conduit structurally comprises an elongated flexible member
having walls which define one or more closed passages. The conduit
is fabricated of a material such as nylon or other non-corrosive
material and can be of a diameter appropriate to the size and
capacity of tank 12. Conduit 15 lower end as mentioned is
communicated with the tank cap 26 and sealably fastened to the
latter by ring 28. As shown in FIG. 5, the conduit upper end is
provided with a head 41 adapted to connect to a corresponding
fitting on tanker 11, barge or other floating facility whereby to
permit a flow of crude oil from tank 12 to said tanker.
Head 41 as shown, includes a metallic body incorporating a flange
42 having means therein to engage connecting lugs or bolts carried
on a mating tanker loading flange. One or more control valves
within head 41 are manually operable by control means 43 extending
externally to the head. Normally, with conduit 15 in the closed or
contracted position, the respective control valve or valves are set
to a closed position. Thus, there will be no flow of oil from tank
12 to the conduit head 41, thereby precluding the inadvertent
passage of oil from the conduit into the surrounding waters.
Said head control valve or valves will remain in closed condition
until such time as head 41 is connected to a loading flange on a
tanker at the water's surface. Thereafter, the control valves 43
are opened to allow a controlled flow of crude oil to pass upwardly
through conduit 15 and into tanks on the floating vessel.
Conduit 15 as mentioned, is fabricated of a relatively heavy walled
non-rigid material such as nylon. Since conduit 15 will at all
times be filled with liquid, either water, oil, or a mixture
thereof, there will be no appreciable external pressure exerted on
said walls regardless of water depth.
Referring to FIGS. 6 and 7, to facilitate the back coiling of
conduit 15 into its retracted position, a self-coiling mechanism is
incorporated into the conduit wall. One embodiment of said element
includes an elongated, prestressed metal strip 44. Tensional stress
induced into said strip 44 will normally urge conduit 15 into the
above noted coiled or retracted position above the floor of the
ocean. To further strengthen the conduit, whereby to maintain a
predesired cross-sectional configuration thereof, the conduit walls
are provided with a reinforcing element such as a helically formed
spring member 46, imbedded therein to provide the desired
rigidizing characteristic.
Operationally, with conduit 15 in the retracted or coiled position,
the conduit head 41 is centrally located with the entire conduit
wound about said head in a substantially vertically oriented
disposition. In such a position conduit 15 will be filled with
water.
As the storage area within tank 12 becomes at least progressively
filled with crude oil, the water-oil interface will be depressed
toward the tank 12 lower end. Sensor means is provided within tank
12 to monitor the position of the interface whereby the tank can be
unloaded at a predetermined maximum point of loading. Such
monitoring means can include any one of several known systems such
as a remotely positioned indicator at the water's surface, or
transmitting means such as a shortwave transmitter adapted to
deliver a signal to a shore based location indicating the condition
of the storage tank.
At such time as it becomes expedient to unload all or a part of the
stored liquid, tanker 11 is anchored above the storage facility.
The respective control valves 31 and 33 at the tank 12 are
connected to a remote control cable 48 extending to the water's
surface, which in turn is buoyed by float 47. Thus, with the tanker
11 in position, the respective control valves are opened to
communicate the tank interior with the water filled conduit 15.
Because of the density differential existing between the oil and
the water, the crude liquid will gradually rise into the conduit 15
thereby displacing the water which will in turn pass to the bottom
of tank 12. As the buoying force within the conduit 15 is increased
by the presence of the oil, said force will overcome the coiling or
retracting force of the strip element 44, whereby to progressively
straighten the conduit 15 until head 41 is at the water's
surface.
With conduit head 41 above the surface, it can be sealably
connected to a loading connection on the tanker 11. Thereafter, by
opening the flow control valve 43 in the conduit head 41, crude
liquid can be transferred from the storage tank 12 into the tanker
11 as required.
The loading operation is terminated by substantially discontinuing
flow from the storage tank 12 into the conduit 15 by choking down
the control valve 31. Simultaneously, purging valve 33 communicated
with the surrounding sea water is opened.
Continued upward movement of the crude oil column through the
conduit 15 will permit the sea water to enter and likewise rise
through conduit 15. At such time as said conduit 15 is evacuated of
oil and filled with water, control valve 43 at the head 41 is
closed. At this point the conduit 15, being filled with water, will
consequently lack the previously noted buoying force exerted by the
contained crude oil. Thus, as the head 41 is released from tanker
11, the recoiling action of the spring element 44 will cause the
conduit head to be slowly submerged beneath the water and the
entire conduit to be self-coiled about the head at the storage
tank.
While conduit 15 is herein disclosed as being coiled closely upon
itself when contracted, the essential purpose of such a disposition
is to submerge the conduit beneath the water's surface and yet
maintain it above the ocean floor. Thus the conduit will not
interfere with floating vessels, nor will it suffer abrasive wear
by moving about said floor.
Further, the conduit is disclosed as normally maintained full of
either water or crude product. However, for optimum operation, the
conduit can, by regulation of the various control valves, be
buoyantly adjusted to hold a desired position in the water.
Obviously many modifications and variations of the invention, as
hereinafter set forth, may be made without departing from the
spirit and scope thereof, and therefore, only such limitations
should be imposed as are indicated in the appended claims.
* * * * *