Claims
- 1. A deepwater riser assembly for use with a spar platform, comprising:
- a riser connecting subsea equipment to a surface wellhead of the spar platform;
- a buoyancy can assembly, comprising:
- an open ended buoyancy can tube surrounding the upper end of the riser;
- an upper seal effectively closing the annulus between the riser and the buoyancy can tube; and
- a load transfer connection between the buoyancy can tube and the riser;
- a pressure charging system communicating with the annulus between the riser and the buoyancy can tube at a location below the upper seal;
- a bottom centralizer connected to the riser at a level corresponding with the lower end of the buoyancy can tube and securing the alignment of the riser within the buoyancy can tube; and
- a plurality of buoyancy can guides mounted on the spar platform and slidingly receiving the exterior of the buoyancy can tubes to secure against relative transverse motion, but to permit relative axial motion.
- 2. A deepwater riser assembly in accordance with claim 1 wherein the upper seal comprises a low pressure packer.
- 3. A deepwater riser assembly in accordance with claim 1 wherein the upper seal comprises a hanger seal assembly which also comprises the load transfer connection.
- 4. A deepwater riser assembly in accordance with claim 1 further comprising a fixed buoyancy module connected to the buoyancy can tube and contributing buoyancy thereto.
- 5. A deepwater riser assembly in accordance with claim 4, wherein the fixed buoyancy module is a hard tank mounted about the circumference of the buoyancy can tube.
- 6. A deepwater riser assembly in accordance with claim 5, wherein the centralizer further comprises an elastomeric flexjoint.
- 7. A deepwater riser assembly in accordance with claim 6 further comprising a stress joint on the riser where the centralizer is attached.
- 8. A deepwater riser system for an offshore platform, the riser system comprising:
- a riser running from a tieback connector near the seafloor to
- a surface wellhead;
- a buoyancy can assembly, comprising:
- an open ended buoyancy can tube surrounding the upper end of the riser;
- a hard tank connected to the buoyancy can tube and contributing buoyancy thereto;
- an upper seal effectively closing the annulus between the riser and the buoyancy can tube; and
- a load transfer connection between the buoyancy can tube and the riser;
- a pressure charging system connected to the interior of the buoyancy can tube below the upper seal;
- a bottom centralizer connected between the riser and the buoyancy can tube at a level corresponding with the lower end of the buoyancy can tube and securing the alignment of the riser within the buoyancy can tube, the bottom centralizer comprising an elastomeric flexjoint;
- a stress joint in the riser at the connection of the riser and the buoyancy tube can;
- a plurality of buoyancy can guides secured to the offshore platform and slidingly receiving the buoyancy can tube so as to resist lateral deflection but permit vertical relative motion.
- 9. A deepwater riser system in accordance with claim 8 wherein the upper seal comprises a low pressure packer.
- 10. A deepwater riser system in accordance with claim 8 wherein the upper seal comprises a multiple seal hanger seal assembly.
- 11. A deepwater riser system in accordance with claim 8, wherein the pressure charging system connected to the interior of the buoyancy can tube below the upper seal comprises a pressure controlled air supply.
Parent Case Info
This application claims the benefit of U.S. Provisional Application No. 60/034,465, filed Dec. 31, 1996, the entire disclosure of which is hereby incorporated by reference.
US Referenced Citations (24)
Non-Patent Literature Citations (2)
Entry |
J. A. van Santen and K. de Werk, "On the Typical Qualities of SPAR Type Structures for Initial or Permanent Field Development." OTC 2716, Paper presented at the Eighth Annual Offshore Technology Conference, Houston, Tex., May 3-6, 1976, 14 pp. |
EPO Search Report, mailed May 13, 1998. |