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GB2280214A - Offshore structure with oil storage tank - Google Patents

Offshore structure with oil storage tank Download PDF

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Publication number
GB2280214A
GB2280214A GB9413761A GB9413761A GB2280214A GB 2280214 A GB2280214 A GB 2280214A GB 9413761 A GB9413761 A GB 9413761A GB 9413761 A GB9413761 A GB 9413761A GB 2280214 A GB2280214 A GB 2280214A
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GB
United Kingdom
Prior art keywords
tank
leg
platform
oil
pile
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9413761A
Other versions
GB9413761D0 (en
Inventor
David William Haley
Michael Timothy Smith
John William Waddell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kvaerner Earl and Wright
Original Assignee
Kvaerner Earl and Wright
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kvaerner Earl and Wright filed Critical Kvaerner Earl and Wright
Publication of GB9413761D0 publication Critical patent/GB9413761D0/en
Publication of GB2280214A publication Critical patent/GB2280214A/en
Withdrawn legal-status Critical Current

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Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/01Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02BHYDRAULIC ENGINEERING
    • E02B17/00Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B17/02Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Foundations (AREA)

Abstract

An oil storage tank, comprising an elongate tank (42) configured to fit in or on a footing (18) for an offshore platform with the axis of the tank generally aligned with the axis of a leg (11) of that platform, in combination with at least one oil transfer coupling arranged to transfer fluid into and out of the tank, and an oil transmission line running down the leg from an upper part of the platform, whereby oil can be transferred into or out of the tank in a controlled manner. The tank may be installed either in an enlarged lower part of a tubular leg (Fig. 3); between pile sleeves 15 which are spaced more widely to accommodate it; or on top of a foundation pile or pile guide cone (Fig. 7). A method of installation involves attracting the tank to a leg at a higher position, so that it may serve as a buoyancy tank during installation of the platform, then lowering it to proximity with the footing. <IMAGE>

Description

OIL STORAGE TANK The invention relates to an oil storage tank system for an offshore platform, and to a method of installing such a tank.
Production of oil from offshore oil fields normally involves crude oil from subsea wells flowing up conductors or risers, through primary processing facilities on a well head platform, and then away from that platform via one or more flowlines for further processing. The flowlines may be fixed seabed pipelines leading to shore, or may be interfield pipelines leading to loading arrangements incorporating flexible hoses for shuttle tankers. In some cases, particularly with shuttle tankers, it may be advantageous to have some buffer storage for oil at the site of the platform. The buffer storage is available to smooth out the flow of oil, and to allow production of crude oil to continue in the event of short interruptions to the flow of partially processed oil through the flowlines for further processing.
Heretofore, buffer storage for crude oil has been provided in concrete gravity based substructures, where discrete cells have been formed in the structure base, inter alia to give sufficient reserves of buoyancy for float-out to site. These cells have subsequently been used for crude oil storage.
Some tubular steel structures (e.g. Module Support Frames supporting primary processing facilities above sea level) have incorporated internal storage tanks within tubular members, to contain diesel fuel to be used on the platform.
In one particular substructure, where large diameter tubular steel legs were used as integral pontoons on which the substructure was floated out to site, the interiors of the large diameter legs have subsequently been used to contain diesel fuel to be used during the operational life of the platform.
However, offshore oil production platforms may include supporting substructures fabricated as three-dimensional lattices made of tubular steel members. Platforms based on such substructures have not in general had provision for buffer storage of crude or partially processed oil.
The invention provides an oil storage tank, comprising an elongate tank configured to fit in or on a footing for an offshore platform with the axis of the tank generally aligned with the axis of a leg of that platform, in combination with at least one oil transfer coupling arranged to transfer fluid into and out of the tank, and an oil transmission line running down the leg from an upper part of the platform, whereby oil can be transferred into or out of the tank in a controlled manner.
Preferably, when installed, the weight of the tank rests on a conventional structural component of the footing.
In one form the tank fits within an enlarged portion of the leg at the lower end of that leg.
In a second form the conventional structural component is a mudmat/yoke plate.
In this second form it is preferred that the tank fits between the leg and one or more pile sleeves connected to that leg by a shear plate, so that lateral support to the tank is provided by the leg and/or pile sleeve(s) and/or shear plate.
In a third form the conventional structural component is the top of a foundation pile or a sleeve for such a pile.
In this third form the tank fits on top of one of the pile sleeves and bears on a foundation pile driven through that sleeve, and is restrained against lateral movement by a locating device (e.g. guide ring or pin) attached to the leg of the jacket above the said one pile sleeve.
In accordance with a preferred feature of the invention the tank is adapted to be attached to the platform in another location (e.g. higher up on the aforesaid leg) so. that, prior to its use as an oil storage tank, it can be used as a buoyancy tank during installation of the platform.
The invention also provides a method of installing an oil storage tank at or close to the footing of an offshore oil production platform, which comprises the steps of lowering an elongate storage tank to a location close to the footing of the platform and adjacent to a leg of the platform, resting a base of that tank on a conventional structural component of the footing, providing lateral support to that tank from a pile sleeve or locating device attached to the leg, and connecting an oil transmission line between the tank and an upper part of the platform.
In accordance with a preferred feature of the invention the tank is initially attached to the aforesaid leg at a different position (e.g. higher up on the leg) such that it may be used as a buoyancy tank during installation of the platform, and is subsequently lowered into the location close to the footing.
Three specific embodiments of the invention (together with an example of prior art) will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevational view of part of a footing of an offshore oil production platform, showing a conventional leg and pile sleeve arrangement; Figure 2 is a section on the arrows II - II in Figure 1; Figure 3 is a view generally corresponding to Figure 1 and showing a first embodiment of the invention; Figure 4 is a section on the arrows IV - IV in Figure 3; Figure 5 is a view generally corresponding to Figure 1 and showing a second embodiment of the invention; Figure 6 is a section on the arrows VI - VI in Figure 5; Figure 7 is a view generally corresponding to Figure 1 and showing a third embodiment of the invention; Figure 8 is a section on the arrows VIII - VIII in Figure 7;; Figure 9 is a diagrammatic side elevational view of a lower part of the platform showing a dual use for the invention; and Figure 10 is an illustration to show the disposition of the other figures in relation to a complete oil production platform.
Offshore oil production platforms may include supporting substructures fabricated as three-dimensional lattices made of tubular steel members.
Such substructures are known within the offshore industry as 'jackets'. A jacket is conventionally fixed to the seabed with tubular steel foundation piles, which extend down into the seabed strata. The upper ends of the tubular foundation piles are secured to the jacket in pile sleeves at the feet of the legs of the jacket.
Figure 1 shows diagrammatically a conventional arrangement at the foot of one leg of a jacket for an offshore oil production platform.
The jacket (resting on seabed 10) has a tubular leg 11, tubular plan bracing 12 and tubular face bracing 14. A pile sleeve 15 has a pile guide cone 16 at its upper end. The pile sleeve 15 is attached to the leg 11 by a yoke plate 19 just below the guide cone 16 by a shear plate 17, and by a mudmat/yoke plate 18 at its lower end.
As may be seen from Figure 2, the footing has two pile sleeves 15 approximately equidistant from the leg 11. Foundation piles may be driven through respective pile sleeves into the subsea strata to fix the jacket to the seabed. The number of pile sleeves will be dependant upon the number of foundation piles required to provide a firm foundation. In some cases only a single pile sleeve will be required; in others up to seven or more pile sleeves may be necessary. When the piles have been driven (or drilled and grouted) into the subsea strata, their upper ends are fixed to their respective pile sleeves.
To provide oil storage capacity within the jacket, it is proposed (according to a first embodiment of the invention) to enlarge the diameter of the lowest part of the tubular leg (i.e. that part below the node where the brace 14 joins the leg 11). As shown in Figures 3 and 4, a modified enlarged leg portion 31 is adapted to form or to enclose a pressure tank 32.
Oil can be transferred into or out of the tank 32 using transfer pipework (not shown) which extends up the interior of the leg 11.
A second embodiment of the invention is shown in Figures 5 and 6. In this case the pile sleeves 15 are arranged at a wider angle apart and are spaced at a greater distance from the tubular leg 11 (as compared with the angle and spacing shown in Figure 1). The mudmat/yoke plate 18 is larger than the mudmat shown in Figure 2. To provide oil storage capacity, an external pressure tank 42 is arranged to fit between the pile sleeves 15 and to overlie (and rest upon) the mudmat/yoke plate 18. Oil can be transferred into or out of the tank 42 using transfer pipework (not shown) which extends up the leg 11, either internally or externally.
In this case the tank 42 can be attached to the leg 11 and/or pile sleeves 15 and/or mudmat/yoke plate 18 prior to installation of the jacket, or can be post installed after the jacket has been founded on the seabed.
In the latter case the transfer pipework must be connected to pre fitted couplings (not shown) to permit the transfer of oil to and from the tank 42.
The tank 42 is easily inspectable and readily replaceable.
A third embodiment of the invention is shown in Figures 7 and 8. In this case the pile sleeves 15 are arranged generally as shown in Figures 1 and 2. To provide oil storage capacity, an external pressure tank 52 is arranged to rest with its base on top of the pile guide cone 16; or (as shown in Figure 7) on a foundation pile 54 driven through the guide cone 16 and the pile sleeve 15, and grouted to that pile sleeve. The upper part of the tank 52 is confined within a guide ring 55 attached to the leg 11.
In this case the tank 52 can only be fitted after the pile 54 has been driven through the sleeve 15, and so the tank 52 must be post installed after the jacket has been founded and piled onto the seabed. Consequently the transfer pipework to access the tank must be connected to prefitted couplings (not shown) after installation, to permit the transfer of oil to and from the tank 52. With the tank 52 supported on the cone 16 or directly on the pile 54, a suitable latching mechanism may be necessary to facilitate stabbing, buoyancy loads and provision for removal. The tank 52 is easily inspectable and readily replaceable.
Figure 9 illustrates another aspect of the invention, in which a storage tank 62 (generally similar to the tank 42 in Figures 5 and 6) is used for two different purposes at different phases in the life of the platform.
Installation is a transitory stage in the life of an offshore platform.
A jacket can be floated from its fabrication yard to its offshore site on a transportation barge, and then launched into the sea. The jacket will have some self buoyancy due to the displacement in water of its structural members, but extra buoyancy may be necessary in order that the launch, upending and setting down onto site can be done safely and accurately. To this end, particularly with light weight jackets for minimal facilities platforms, additional buoyancy is needed for the launch and upending procedures.
According to a feature of the invention, a tank is temporarily attached to the leg 11 at an intermediate height on that leg, designated as position A. The tank can be attached to the leg at the fabrication yard, or on a transportation barge just before installation of the jacket. In the position A the tank (initially in an empty condition) can be used as additional buoyancy to aid a launch and upending procedure used to install the jacket. The tank may be flooded as a later part of that procedure, to assist in providing initial on-bottom stability.
Subsequently the tank 62 can be lowered into its permanent location, designated as position B. In this permanent location it can be used for oil storage as' described with reference to Figures 5 and 6. Because position B is close to the seabed, only self weight and seabed current loads are applied to the tank. Wave loads are not applicable at this depth.
The technique of using a single tank for two different purposes at different phases in the life of the platform can also be applied with the third embodiment of the invention, as described with reference to Figures 7 and 8.
In Figure 10, zone 'x' shows the general location of Figures 1 and 2, 3 and 4, 5 and 6 and 7 and 8, and zone 'y' shows the general location of Figure 9.

Claims (9)

1. An oil storage tank, comprising an elongate tank configured to fit in or on a footing for an offshore platform with the axis of the tank generally aligned with the axis of a leg of that platform, in combination with at least one oil transfer coupling arranged to transfer fluid into and out of the tank, and an oil transmission line running down the leg from an upper part of the platform, whereby oil can be transferred into or out of the tank in a controlled manner.
2. A tank as claimed in Claim 1 in which, when installed, the weight of the tank rests on a conventional structural component of the footing.
3. A tank as claimed in Claim 1 or Claim 2 in which the tank fits within an enlarged portion of the leg at the lower end of that leg.
4. A tank as claimed in Claim 1 or Claim 2 in which the conventional structural component is a mudmat/yoke plate.
5. A tank as claimed in Claim 4 in which the tank fits between the leg and one or more pile sleeves connected to that leg by a shear plate, so that lateral support to the tank is provided by the leg and/or pile sleeve(s) and/or shear plate.
6. A tank as claimed in Claim 1 or Claim 2 in which the conventional structural component is the top of a foundation pile or a sleeve for such a pile.
7. A tank as claimed in Claim 6 in which the tank fits on top of one of the pile sleeves and bears on a foundation pile driven through that sleeve, and is restrained against lateral movement by a locating device (e.g.
guide ring or pin) attached to the leg of the jacket above the said one pile sleeve.
8. A tank as claimed in any one of Claims 1, 2 and 4 to 7 in which the tank is adapted to be attached to the platform in another location (e.g.
higher up on the aforesaid leg) so that, prior to its use as an oil storage tank, it can be used as a buoyancy tank during installation of the platform.
9. A method of installing an oil storage tank substantially as hereinbefore described with reference to Figures 5 and 6 or Figures 7 and 8 and Figure 9 of the accompanying drawings.
9. A method of installing an oil storage tank at or close to the footing of an offshore oil production platform, which comprises the steps of lowering an elongate storage tank to a location close to the footing of the platform and adjacent to a leg of the platform, resting a base of that tank on a conventional structural component of the footing, providing lateral support to that tank from a pile sleeve or locating device attached to the leg, and connecting an oil transmission line between the tank and an upper part of the platform.
10. A method of installation of an oil storage tank as claimed in Claim 9, in which the tank is initially attached to the aforesaid leg at a different position (e.g. higher up on the leg) such that it may be used as a buoyancy tank during installation of the platform, and is subsequently lowered into the location close to the footing.
11. An oil storage tank substantially as hereinbefore described with reference to and as shown in Figures 3 and 4, or Figures 5 and 6, or Figures 7 and 8, or in Figure 9 of the accompanying drawings.
12. A method of installing an oil storage tank substantially as hereinbefore described with reference to Figures 5 and 6 or Figures 7 and 8, or as a modified method described with reference to Figure 9 of the accompanying drawings.
Amendments to the claims have been filed as follows 1. An oil storage tank, comprising an elongate tank configured to fit on a footing for an offshore platform with the axis of the tank generally aligned with the axis of a leg of that platform, in combination with at least one oil transfer coupling arranged to transfer fluid into and out of the tank, and an oil transmission line running down the leg from an upper part of the platform, whereby oil can be transferred into or out of the tank in a controlled manner; in which the tank is adapted to be attached to the platform in another location (e.g. higher up on the aforesaid leg) so that, prior to its use as an oil storage tank, it can be used as a buoyancy tank during installation of the platform.
2. A tank as claimed in Claim 1 in which, when installed, the weight of the tank rests on a conventional structural component of the footing.
3. A tank as claimed in Claim 1 or Claim 2 in which the conventional structural component is a mudmat/yoke plate.
4. A tank as claimed in Claim 3 in which the tank fits between the leg and one or more pile sleeves connected to that leg by a shear plate, so that lateral support to the tank is provided by the leg and/or pile sleeve(s) and/or shear plate.
5. A tank as claimed in Claim 1 or Claim 2 in which the conventional structural component is the top of a foundation pile or a sleeve for such a pile.
6. A tank as claimed in Claim 5 in which the tank fits on top of one of the pile sleeves and bears on a foundation pile driven through that sleeve, and is restrained against lateral movement by a locating device (e.g.
guide ring or pin) attached to the leg of the jacket above the said one pile sleeve.
7. A method of installing an oil storage tank at or close to the footing of an offshore oil production platform, in which an elongate storage tank is initially attached to a leg of the platform at a first position such that it may be used as a buoyancy tank during installation of the platform, and is subsequently lowered into a location close to the footing of the platform and adjacent to the leg of the platform, resting a base of that tank on a conventional structural component of the footing, providing lateral support to that tank from a pile sleeve or locating device attached to the leg, and connecting an oil transmission line between the tank and an upper part of the platform.
8. An oil storage tank substantially as hereinbefore described with reference to and as shown in Figures 5 and 6, or Figures 7 and 8, or in Figure 9 of the accompanying drawings.
GB9413761A 1993-07-07 1994-07-07 Offshore structure with oil storage tank Withdrawn GB2280214A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB939314018A GB9314018D0 (en) 1993-07-07 1993-07-07 Oil storage tank

Publications (2)

Publication Number Publication Date
GB9413761D0 GB9413761D0 (en) 1994-08-24
GB2280214A true GB2280214A (en) 1995-01-25

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GB939314018A Pending GB9314018D0 (en) 1993-07-07 1993-07-07 Oil storage tank
GB9413761A Withdrawn GB2280214A (en) 1993-07-07 1994-07-07 Offshore structure with oil storage tank

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB939314018A Pending GB9314018D0 (en) 1993-07-07 1993-07-07 Oil storage tank

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009131543A1 (en) * 2008-04-25 2009-10-29 National University Of Singapore Offshore fuel storage facility
WO2014047926A1 (en) * 2012-09-29 2014-04-03 Wu Zhirong Offshore liquid depot
US20170183835A1 (en) * 2015-12-27 2017-06-29 William Wei Lee Submerged oil storage, loading and offloading system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2528679A1 (en) * 1975-06-27 1977-01-13 Salzgitter Maschinen Ag Offshore drilling platform - with splayed legs resting on foundation tanks used for crude oil storage
GB1464612A (en) * 1975-05-16 1977-02-16 Wimpey M E C Ltd G Submersible petroleum storage tanks
GB1522897A (en) * 1975-11-17 1978-08-31 Liautaud J Marine platform for offshore submarine drilling operations and the like

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1464612A (en) * 1975-05-16 1977-02-16 Wimpey M E C Ltd G Submersible petroleum storage tanks
DE2528679A1 (en) * 1975-06-27 1977-01-13 Salzgitter Maschinen Ag Offshore drilling platform - with splayed legs resting on foundation tanks used for crude oil storage
GB1522897A (en) * 1975-11-17 1978-08-31 Liautaud J Marine platform for offshore submarine drilling operations and the like

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009131543A1 (en) * 2008-04-25 2009-10-29 National University Of Singapore Offshore fuel storage facility
WO2014047926A1 (en) * 2012-09-29 2014-04-03 Wu Zhirong Offshore liquid depot
US20170183835A1 (en) * 2015-12-27 2017-06-29 William Wei Lee Submerged oil storage, loading and offloading system
US9783947B2 (en) * 2015-12-27 2017-10-10 William Wei Lee Submerged oil storage, loading and offloading system

Also Published As

Publication number Publication date
GB9314018D0 (en) 1993-08-18
GB9413761D0 (en) 1994-08-24

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