Deep draft semi-submersible offshore floating structure

Abstract

A deep draft semi-submersible floating offshore structure. Interconnected buoyant pontoons form a center well. Buoyant columns attached to the pontoons extend upwardly therefrom. A topside structure is supported on the upper end of the columns. A first heave plate is located in the center well of the pontoons. A second heave plate is positioned above the first heave plate between the columns. Risers may be positioned to be received through the heave plates, the pontoons, or a center well in the columns. The columns of the structure are sized to provide an operational draft that is deeper than a typical semi-submersible structure. The arrangement of the structure provides dampened vertical motions, is structurally efficient, has no extendable moving parts, provides better structural integrity, and is construction friendly.

1 . A deep draft semi-submersible floating offshore structure, comprising: 
 a. a plurality of interconnected buoyant pontoons that define an open center well between said pontoons;    b. a first heave plate located in the center well between said pontoons;    c. a plurality of buoyant columns attached to said pontoons and extending upwardly therefrom;    d. a topside structure supported on said columns; and    e. a second heave plate connected to said columns between said pontoons and said topside structure.    
     
     
         2 . The deep draft semi-submersible floating offshore structure of  claim 1 , wherein said first and second heave plates are provided with a plurality of apertures therethrough sized to receive risers.  
     
     
         3 . The deep draft semi-submersible floating offshore structure of  claim 1 , wherein said hull is provided with a plurality of vertical apertures therethrough sized to receive risers.  
     
     
         4 . The deep draft semi-submersible floating offshore structure of  claim 1 , wherein at least one of said columns is provided with a center well.  
     
     
         5 . The deep draft semi-submersible floating offshore structure of  claim 4 , further comprising a buoyancy can received in said center well in the column, said buoyancy can designed to receive and support risers.  
     
     
         6 . The deep draft semi-submersible floating offshore structure of  claim 4 , further comprising top tensioned risers received in the center well in said column.  
     
     
         7 . The deep draft semi-submersible floating offshore structure of  claim 1 , wherein said structure has an operational draft of approximately two hundred feet.  
     
     
         8 . A deep draft semi-submersible floating offshore structure, comprising: 
 a. a plurality of interconnected buoyant pontoons that define an open center well between said pontoons;    b. a first heave plate located in the center well between said pontoons;    c. a plurality of buoyant columns attached to said pontoons and extending upwardly therefrom, at least one of said columns having a center well therethrough;    d. a buoyancy can received in each center well in said columns, said buoyancy can designed to receive and support risers;    e. a topside structure supported on said columns; and    f. a second heave plate attached to said columns between said pontoons and said topside structure.    
     
     
         9 . A deep draft semi-submersible floating offshore structure, comprising: 
 a. a plurality of interconnected buoyant pontoons that define an open center well between said pontoons;    b. a heave plate located in the center well between said pontoons;    c. a plurality of buoyant columns attached to said pontoons and extending upwardly therefrom;    d. a topside structure supported on said columns.    
     
     
         10 . The deep draft semi-submersible offshore structure of  claim 9 , wherein said heave plate is provided with a plurality of apertures therethrough designed to receive risers.  
     
     
         11 . The deep draft semi-submersible offshore structure of  claim 9 , wherein said hull is provided with a plurality of vertical apertures therethrough sized to receive risers.  
     
     
         12 . The deep draft semi-submersible offshore structure of  claim 9 , wherein at least one of said columns is provided with a center well.  
     
     
         13 . The deep draft semi-submersible offshore structure of  claim 12 , further comprising a buoyancy can received in said center well in the column, said buoyancy can designed to receive and support risers.  
     
     
         14 . The deep draft semi-submersible offshore structure of  claim 12 , further comprising top tensioned risers received in the center well in said column.