초록 ▼

An ocean platform has a negatively buoyant pontoon suspended from the balance of the platform to increase the heave resonant period to at least 25 seconds. Tendons suspend the pontoon to a depth where dynamic wave forces do not materially act directly on it in seas of normally occurring periods of u

An ocean platform has a negatively buoyant pontoon suspended from the balance of the platform to increase the heave resonant period to at least 25 seconds. Tendons suspend the pontoon to a depth where dynamic wave forces do not materially act directly on it in seas of normally occurring periods of up to about 15 seconds but do in seas of periods above about 15 seconds. Columns and an upper pontoon provide buoyancy for the platform.

대표청구항 ▼

An exploration or production platform comprising; (a) deck; (b) buoyancy means including a plurality of buoyant columns attached to the deck for keeping the platform afloat at sea with the upper portion of the columns being above the sea surface and the deck spaced from the sea surface; (c) negative

An exploration or production platform comprising; (a) deck; (b) buoyancy means including a plurality of buoyant columns attached to the deck for keeping the platform afloat at sea with the upper portion of the columns being above the sea surface and the deck spaced from the sea surface; (c) negatively buoyant pontoon means for providing negative buoyancy and having a displaced mass and an added mass of sea water of at least about 45% of the total effective mass of the platform, the added mass being substantially the same for both directions of vertical motion of the negatively buoyant pontoon; (d) flexible tendon means for suspending the negatively buoyant pontoon means from below the balance of the platform to a depth above the sea bottom and where wave induced dynamic forces on the pontoon are small and do not materially contribute to the heave response of the platform at commonly experienced wave periods but where wave induced dynamic forces do act on the pontoon at higher wave periods below resonance of the platform, the negatively buoyant pontoon means being capable of having a negative buoyancy sufficient to keep tension in the tendon means during all sea conditions; and (e) the platform having natural period in heave of at least about 25 seconds. An exploration or production platform comprising: (a) a deck; (b) buoyancy means including at least four columns in a square pattern attached to the deck for keeping the platform afloat at sea with the upper portion of the columns above the sea surface and the deck spaced from the sea surface; (c) a negatively buoyant pontoon for providing negative buoyancy and a large displaced and added mass, the negatively buoyant pontoon in plan view being generally square shaped with an open center and having a displaced mass and added mass of sea water at least about 60% of the total effective mass of the platform, the added mass being substantially the same for both directions of vertical motion of the negatively buoyant pontoon; (d) flexible tendon means for suspending the negative buoyant pontoon from below the balance of the platform to a depth above the sea bottom and where wave induced dynamic forces on the pontoon are small and do not materially contribute to the heave response of the platform in waves of normally occurring periods, but where wave induced dynamic forces do act on the negatively buoyant pontoon at higher wave periods below resonance of the platform the negative buoyancy of the negatively buoyant pontoon means maintaining the tendons in tension during all sea periods up to about 25 seconds or wave heights of 30 meters; and (e) the platform having a natural period of heave of at least about 25 seconds.