Semi-submersibles, by necessity of the high platform containing large and varying masses, require large metacentric heights which, in turn, require the water plane areas of the support columns to be large enough to provide positive stability in every conceivable loading and sea condition. The heave resonance of these platforms occurs in seas having periods in the 14-30 second range which is about the lowest resonance obtainable given the physical constraints imposed by safety, size limitations and structural considerations. This is adequate for most conditions but, unfortunately, the heavier seas are associated with these lower frequencies giving rise to platform responses in heave as high as forty percent of wave height. These motions are objectionable from several points of view and frequently cause all operations to cease. It is suggested that a "Below the Interface Platform" vertically structured with only a small cross section surface piercing element will present several advantages over the present day semi-submersible. It is further recommended that this platform be designed using submarine rather than surface ship technology and that it be capable of either vertical orientation for drilling operations or horizontal for transit. In either mode gas turbines using air drawn through one of two surface piercing "snorkel" valves will provide power for drilling as well as for propulsion and station keeping maneuvering. Propulsion and control may be provided by one of several methods, however, for this paper the TANDEM PROPELLER system will be presented as being the most appropriate.

  • Supplemental Notes:
    • Presented at the 3rd International Ocean Development Conference.
  • Corporate Authors:

    Japan Marine Association

    1-22, 3-Chome, Shiba Park, Minato-Ku
    Tokyo 103,   Japan 
  • Authors:
    • Haselton, F R
  • Publication Date: 1975-8

Media Info

  • Pagination: 10 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00099953
  • Record Type: Publication
  • Source Agency: Haselton (FR)
  • Files: TRIS
  • Created Date: Oct 18 1975 12:00AM