CA2439788A1 - Compliant stem buoyancy can and guide - Google Patents
Compliant stem buoyancy can and guide Download PDFInfo
- Publication number
- CA2439788A1 CA2439788A1 CA 2439788 CA2439788A CA2439788A1 CA 2439788 A1 CA2439788 A1 CA 2439788A1 CA 2439788 CA2439788 CA 2439788 CA 2439788 A CA2439788 A CA 2439788A CA 2439788 A1 CA2439788 A1 CA 2439788A1
- Authority
- CA
- Canada
- Prior art keywords
- buoyancy
- stem
- compliant
- hull
- vessel
- 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.)
- Abandoned
Links
- 230000007613 environmental effect Effects 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 12
- 230000010355 oscillation Effects 0.000 abstract description 3
- 238000006073 displacement reaction Methods 0.000 abstract description 2
- 238000013459 approach Methods 0.000 description 7
- 230000001133 acceleration Effects 0.000 description 3
- 238000005553 drilling Methods 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013013 elastic material Substances 0.000 description 1
- 230000005021 gait Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
- B63B35/4406—Articulated towers, i.e. substantially floating structures comprising a slender tower-like hull anchored relative to the marine bed by means of a single articulation, e.g. using an articulated bearing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B22/00—Buoys
- B63B22/02—Buoys specially adapted for mooring a vessel
- B63B22/021—Buoys specially adapted for mooring a vessel and for transferring fluids, e.g. liquids
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
- E21B17/01—Risers
- E21B17/012—Risers with buoyancy elements
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Combustion & Propulsion (AREA)
- Chemical & Material Sciences (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Fluid Mechanics (AREA)
- Environmental & Geological Engineering (AREA)
- Physics & Mathematics (AREA)
- Earth Drilling (AREA)
- Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
- Vibration Prevention Devices (AREA)
Abstract
A compliant stem buoyancy can and guide for a floating offshore structure or vessel. The buoyancy can is supported at the upper stop and the various heave plates by a slip ring that allows axial displacement but constrains any radial motion.
The buoyancy can behaves as a complaint beam with a dynamic response like a spring/mass/damper. The stiffness and mass acts to govern the amplitude and frequency of the motion. The water in the well bay reacts to the relative speed of the vessel motion and the buoyancy can. The water thus acts as a damper. The vessel, stem, and buoyancy can are designed so the clearance between the buoyancy can and hull is larger than the maximum amplitude of the oscillation. Therefore, the can will not impact the hull. The kinetic energy is dissipated by the compliant response of the buoyancy can and stem structure.
Because the buoyancy can never hits the hull there are no impact loads or fatigue associated with impacts.
The buoyancy can behaves as a complaint beam with a dynamic response like a spring/mass/damper. The stiffness and mass acts to govern the amplitude and frequency of the motion. The water in the well bay reacts to the relative speed of the vessel motion and the buoyancy can. The water thus acts as a damper. The vessel, stem, and buoyancy can are designed so the clearance between the buoyancy can and hull is larger than the maximum amplitude of the oscillation. Therefore, the can will not impact the hull. The kinetic energy is dissipated by the compliant response of the buoyancy can and stem structure.
Because the buoyancy can never hits the hull there are no impact loads or fatigue associated with impacts.
Description
a COMPLIANT STEM BUOY~~N'CY GAIT AND GUIDE
BACKGROUND OF THE INVENTTON
1. Field of the Invention The invention is generally related to risers in offshore floating structures and more particularly to buoyancy can guides for risers.
BACKGROUND OF THE INVENTTON
1. Field of the Invention The invention is generally related to risers in offshore floating structures and more particularly to buoyancy can guides for risers.
2. General Background In offshore floating structures or vessels used to drill for and produce oil and gas, such as spar type structures and TLP's, buoyancy cans are used to support the weight of drilling and production risers. Buoyancy can guides are placed in the body of the vessel. Environmental forces such as wind, waves, and currents cause the buoyancy cans to move and impact wear plates against the guides ir~ the hull.. Two design. approaches have typically been followed to address the wear associated with the impacts. One approach is compliant guides. In this approach an elastic material such as rubber that deforms under load is used to absorb the impact energy. This approach does not present a long-term solution because the rubber guides are unable to withstand the loads over a long period of repeated impacts before they fall apart. A second approach is to provide a near zero gap between the buoyancy guides and the vessel. In this approach the tolerances are kept to a minimum to impede the acceleration of the buoyancy can, therefore reducing the impact load. The hull and buoyancy cans are designed to withstand the impact loads. 'The problem with this approach is that construction tolerances make it very difficult to achieve the small gaps that are required to impede the acceleration of the buoyancy can to an acceptable level.
SUMMARY OF THE TNVENTION
The invention addresses the above needs. What is provided is a compliant stem buoyancy can and guide . The buoyancy can is supported at the upper stop and the various heave plates by a slip ring that allows axial displacement but constrains any radial motion. The buoyancy can behaves as a complaint beam with a dynamic response like a spring/mass/damper. The stiffness and mass acts to govern the amplitude and frequency of the motion. The water in the well bay reacts to the relative speed of the vessel motion anc-.~ the buoyancy can. The water thus acts as a damper. The apparatus is designed so the clearance between the buoyancy can and hull is larger than the maximum amplitude of the oscillation. Therefore, the can will not impact the hull. T'ne kinetic energy is dissipated by the compliant response of the buoyancy can and stem structure.
Because the buoyancy can never hits the hull there are no impact loads and no fatigue associated with impacts.
BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the nature and objects of the present invention reference should be made to the following description, taken in conjunction with the accompanying drawing in which like parts are given like reference numerals, and wherein:
The sole drawing is a s;de section view of the invention in a spar type structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
SUMMARY OF THE TNVENTION
The invention addresses the above needs. What is provided is a compliant stem buoyancy can and guide . The buoyancy can is supported at the upper stop and the various heave plates by a slip ring that allows axial displacement but constrains any radial motion. The buoyancy can behaves as a complaint beam with a dynamic response like a spring/mass/damper. The stiffness and mass acts to govern the amplitude and frequency of the motion. The water in the well bay reacts to the relative speed of the vessel motion anc-.~ the buoyancy can. The water thus acts as a damper. The apparatus is designed so the clearance between the buoyancy can and hull is larger than the maximum amplitude of the oscillation. Therefore, the can will not impact the hull. T'ne kinetic energy is dissipated by the compliant response of the buoyancy can and stem structure.
Because the buoyancy can never hits the hull there are no impact loads and no fatigue associated with impacts.
BRIEF DESCRIPTION OF THE DRAWINGS
For a further understanding of the nature and objects of the present invention reference should be made to the following description, taken in conjunction with the accompanying drawing in which like parts are given like reference numerals, and wherein:
The sole drawing is a s;de section view of the invention in a spar type structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawing, it is seen that the invention is generally indicated by the numeral 10. Oompliant stem buoyancy can and guide 10 are comprised of a buoyancy can 12, a stem 14, and a plurality of slip rings 16.
The drawing generally illustrates a floating offshore structure 1$, such as a spar type structure, that is provided with a center well 20 sized to receive drilling and/or production risers G2.
The buoyancy can Z2 is attached to the upper portion of the stem 14 and provides buoyant support to the stem 14 and risers 22. The stem 14 extends upward from the buoyancy can I2 to controls 24 on t'ne top of the offshore structure ~.8.
A plurality of slip rings 16 are sized to closely receive the stem 14 and are spaced along the length of the stem. One slip ring 16A is preferably positioned around each stem 14 at the upper end of the offshore structure 18. The remaining slip rings 16 are positioned below the buoyancy can 12 and are attached at the lower end of the center well 20 and to heave plates 26 that are attached to the offshore structure 18.
The stiffness of the buoyancy can 12, stem 14, and riser 22 axe designed to work in conjunction with the slip rings 16 to prevent the buoyancy can 12 from contacting the offshore str~~:.cture 18 during normal movement in response to environmental forces.
The stiffness of the buoyancy can 12, stem, 14, and riser 22 is selected to control the compliant dynamic response of these structures. The slip rings 16 closely receive the stem 14 and riser 22 to allow vertical movement as indicated by arrows 28 but limit radial movement.
The combination of the slip rings 1~ and the predetermined compliant dynamic response limit the radial movement of the buoyancy can 12 to a range that is less than the inner diameter of the center well 20, as indicated by arrows 30. Thus, the buoyancy can 12 behaves as a compliant beam with a dynamic response like a springfmass/damper system. The stiffness and mass of the configuration governs the amplitude and frequency of the motion. The water in the center well reacts to the relative speed of the offshore structure and the can, thus acting as a damper. The drag of the buoyancy can 12 is a function of VZ (velocity squared). Also, the acceleration of the water in the center well induces buoyancy that damps the motion. The configuration is designed so that the clearance between the buoyancy can and inner wall of the center well is larger than the maximum amplitude of the oscillation of the buoyancy can. Therefore, the buoyancy can will not impact the hull of the offshore structure. The kinetic energy is dissipated by the compliant response of the buoyancy can and stern structure.
The configuration will depend upon a variety of factors.
These factors include the depth of the structure, the minimum natural period of the structure and the buoyancy can, the buoyancy required, the diameter of the cen'~er well, the diameter of the buoyancy can, the diameter of the stem, and the diameter of the riser. fin example of one possible configuration follows. The controls, buoyancy can, and stem that run through a spar structure such as that described in .. S -U.S. Patent No. 5,558,467 may have a total length of approximately seven hundred fifty-four feet. The controls and stem would extend approximately one hundred sixty-eight feet above the normal water line. The buoyancy can would begin at approximately five feet below the normal water line and extend downward to approximately one hundred sixty-three feet below the normal water line. The stem extends the remainder of the distance through the structure and the riser extends beyond the keel of the structure to the sea floor. For such a structure having a center well with a diameter of thirteen feet, a required tension (buoyancy) of one thousand kips is preferred for a water depth of approximately five thousand six hundred ten feet (one thousand seven hundred ten meters) . Seven slip rings, as indicated, would be spaced along the length of the center well. An example of one spacing arrangement is as follows. The slip rings may be placed at intervals of fifty and twenty-one feet above the mean water level and at five, two hundred five, two hundred sixty-two, three hundred forty, four hundred eighteen, and five hundred thirty-six feet below the mean water level. It is preferable that a slip ring be positioned at or near the keel joint of the offshore structure.
The invention provides several advantages. There are no impact loads to the walls of the buoyancy can. Therefore; the wall thickness and other structural steel can be reduced. This provides a positive cost impact and increases the net buoyancy.
The slip rings are placed around the stem and the riser instead of the buoyancy can. Because the diameter of the slip ring is substantially smaller than if it were placed around the buoyancy can, this allows the use of more sophisticated devices and materials to control the gap and the wear.
Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
The drawing generally illustrates a floating offshore structure 1$, such as a spar type structure, that is provided with a center well 20 sized to receive drilling and/or production risers G2.
The buoyancy can Z2 is attached to the upper portion of the stem 14 and provides buoyant support to the stem 14 and risers 22. The stem 14 extends upward from the buoyancy can I2 to controls 24 on t'ne top of the offshore structure ~.8.
A plurality of slip rings 16 are sized to closely receive the stem 14 and are spaced along the length of the stem. One slip ring 16A is preferably positioned around each stem 14 at the upper end of the offshore structure 18. The remaining slip rings 16 are positioned below the buoyancy can 12 and are attached at the lower end of the center well 20 and to heave plates 26 that are attached to the offshore structure 18.
The stiffness of the buoyancy can 12, stem 14, and riser 22 axe designed to work in conjunction with the slip rings 16 to prevent the buoyancy can 12 from contacting the offshore str~~:.cture 18 during normal movement in response to environmental forces.
The stiffness of the buoyancy can 12, stem, 14, and riser 22 is selected to control the compliant dynamic response of these structures. The slip rings 16 closely receive the stem 14 and riser 22 to allow vertical movement as indicated by arrows 28 but limit radial movement.
The combination of the slip rings 1~ and the predetermined compliant dynamic response limit the radial movement of the buoyancy can 12 to a range that is less than the inner diameter of the center well 20, as indicated by arrows 30. Thus, the buoyancy can 12 behaves as a compliant beam with a dynamic response like a springfmass/damper system. The stiffness and mass of the configuration governs the amplitude and frequency of the motion. The water in the center well reacts to the relative speed of the offshore structure and the can, thus acting as a damper. The drag of the buoyancy can 12 is a function of VZ (velocity squared). Also, the acceleration of the water in the center well induces buoyancy that damps the motion. The configuration is designed so that the clearance between the buoyancy can and inner wall of the center well is larger than the maximum amplitude of the oscillation of the buoyancy can. Therefore, the buoyancy can will not impact the hull of the offshore structure. The kinetic energy is dissipated by the compliant response of the buoyancy can and stern structure.
The configuration will depend upon a variety of factors.
These factors include the depth of the structure, the minimum natural period of the structure and the buoyancy can, the buoyancy required, the diameter of the cen'~er well, the diameter of the buoyancy can, the diameter of the stem, and the diameter of the riser. fin example of one possible configuration follows. The controls, buoyancy can, and stem that run through a spar structure such as that described in .. S -U.S. Patent No. 5,558,467 may have a total length of approximately seven hundred fifty-four feet. The controls and stem would extend approximately one hundred sixty-eight feet above the normal water line. The buoyancy can would begin at approximately five feet below the normal water line and extend downward to approximately one hundred sixty-three feet below the normal water line. The stem extends the remainder of the distance through the structure and the riser extends beyond the keel of the structure to the sea floor. For such a structure having a center well with a diameter of thirteen feet, a required tension (buoyancy) of one thousand kips is preferred for a water depth of approximately five thousand six hundred ten feet (one thousand seven hundred ten meters) . Seven slip rings, as indicated, would be spaced along the length of the center well. An example of one spacing arrangement is as follows. The slip rings may be placed at intervals of fifty and twenty-one feet above the mean water level and at five, two hundred five, two hundred sixty-two, three hundred forty, four hundred eighteen, and five hundred thirty-six feet below the mean water level. It is preferable that a slip ring be positioned at or near the keel joint of the offshore structure.
The invention provides several advantages. There are no impact loads to the walls of the buoyancy can. Therefore; the wall thickness and other structural steel can be reduced. This provides a positive cost impact and increases the net buoyancy.
The slip rings are placed around the stem and the riser instead of the buoyancy can. Because the diameter of the slip ring is substantially smaller than if it were placed around the buoyancy can, this allows the use of more sophisticated devices and materials to control the gap and the wear.
Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
Claims
1. In a floating offshore structure having a center well and a riser received in the center cell, a compliant stem buoyancy can and guide, comprising:
a. a buoyancy can attached to the upper portion of the riser, said buoyancy can having a predetermined compliant dynamic radial response to environmental forces;
b. a stem attached to said buoyancy can and extending through the offshore structure, said stem receiving the riser inside the stem and having a predetermined compliant dynamic radial response to environmental forces; and c. a plurality of slip rings attached along the length of said stem to the offshore structure, said slip rings closely receiving said stem and allowing vertical movement of said stem and the riser.
a. a buoyancy can attached to the upper portion of the riser, said buoyancy can having a predetermined compliant dynamic radial response to environmental forces;
b. a stem attached to said buoyancy can and extending through the offshore structure, said stem receiving the riser inside the stem and having a predetermined compliant dynamic radial response to environmental forces; and c. a plurality of slip rings attached along the length of said stem to the offshore structure, said slip rings closely receiving said stem and allowing vertical movement of said stem and the riser.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24160702A | 2002-09-11 | 2002-09-11 | |
| US10/241,607 | 2002-09-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2439788A1 true CA2439788A1 (en) | 2004-03-11 |
Family
ID=29250254
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2439788 Abandoned CA2439788A1 (en) | 2002-09-11 | 2003-09-08 | Compliant stem buoyancy can and guide |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP1398267A1 (en) |
| BR (1) | BR0302593B1 (en) |
| CA (1) | CA2439788A1 (en) |
| NO (1) | NO20033999L (en) |
| ZA (1) | ZA200306196B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102434130A (en) * | 2011-12-24 | 2012-05-02 | 大连理工大学 | System and method for locating ultra-deepwater underwater stand pipe supporting pontoon |
| CN106080976B (en) * | 2016-06-15 | 2020-09-08 | 中国船舶工业集团公司第七○八研究所 | Air bag type buoyancy tank supporting device of SPAR platform and using method thereof |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4634314A (en) * | 1984-06-26 | 1987-01-06 | Vetco Offshore Inc. | Composite marine riser system |
| US5558467A (en) | 1994-11-08 | 1996-09-24 | Deep Oil Technology, Inc. | Deep water offshore apparatus |
| US6161620A (en) * | 1996-12-31 | 2000-12-19 | Shell Oil Company | Deepwater riser system |
| US6309141B1 (en) * | 1997-12-23 | 2001-10-30 | Shell Oil Company | Gap spar with ducking risers |
| US6176646B1 (en) * | 1998-10-23 | 2001-01-23 | Deep Oil Technology, Incorporated | Riser guide and support mechanism |
| US7008141B2 (en) * | 1999-12-07 | 2006-03-07 | Fmc Technologies, Inc. | Collapsible buoyancy device for risers on offshore structures |
| US6488447B1 (en) * | 2000-05-15 | 2002-12-03 | Edo Corporation | Composite buoyancy module |
-
2003
- 2003-07-25 BR BR0302593A patent/BR0302593B1/en not_active IP Right Cessation
- 2003-07-28 EP EP20030254719 patent/EP1398267A1/en not_active Withdrawn
- 2003-08-11 ZA ZA200306196A patent/ZA200306196B/en unknown
- 2003-09-08 CA CA 2439788 patent/CA2439788A1/en not_active Abandoned
- 2003-09-10 NO NO20033999A patent/NO20033999L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| BR0302593A (en) | 2004-08-24 |
| EP1398267A1 (en) | 2004-03-17 |
| NO20033999L (en) | 2004-03-12 |
| NO20033999D0 (en) | 2003-09-10 |
| BR0302593B1 (en) | 2011-08-09 |
| ZA200306196B (en) | 2004-03-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |