Stability of the Deepwater Horizon

Discussion in 'Stability' started by Earl Boebert, Apr 28, 2013.

  1. listlad
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    listlad Junior Member

    Hi Artichoke. For the Nautilus and Horizon, below operating draft the columns are vertical but above they are diagonal. That is unusual for a semisub, where the columns are normally vertical. My guess is that design gives them more stability in the water than their sisters whose columns are vertical all the way up?
     
  2. NavalSArtichoke
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    NavalSArtichoke Senior Member

    The diagonal portion of the columns gives a wider separation to the pontoons and to the parts of the columns which are immersed when the rig is anchored, thus increasing stability in the transverse direction.

    You're never entirely sure how some of these design features come to be. The rig might have run into stability problems during the initial design and the columns and pontoons needed a wider separation to regain stability. Or the designer wanted to make this rig stand out visually from all the other rigs out there with plain vertical columns.
     
  3. listlad
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    listlad Junior Member

    Its leg design is similar if not the same as the Nautilus - splayed.
     
  4. NavalSArtichoke
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    NavalSArtichoke Senior Member

    That's not surprising. Because of the cost of building a typical rig, shipyards and rig designers have developed basic rig designs, the top works of which can be customized to a customer's drilling needs. These rigs can be built as near sisters of one another, as far as the floaty bits are concerned, much like conventional cargo or naval vessels are built in series production as different classes.

    Both the Nautilus and the Horizon were built to the same design (about), the Reading & Bates RBS-8D design, by Hyundai Heavy Industries. Reading & Bates were well-known drilling consultants and contractors in the States. After a series of mergers within the drilling industry, R & B were eventually acquired by Transocean.
     

  5. listlad
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    listlad Junior Member

    Think I might have found the answer to my question. With a wider and thus splayed column arrangement I gather, both rigs would be more stable in swells associated with deeper water.
     
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