Truss semi-submersible offshore floating structure

Abstract

A semi-submersible structure. The hull includes four columns that are supported by two pontoons. The columns support the topsides and the topsides structural framing serves as horizontal framing between the columns. A truss frame is attached to the columns. The truss frame preferably includes heave plates. The truss frame extends downward below the pontoons a sufficient distance in the water such that it minimizes motions caused by environmental forces. The hull section and the truss space frame are constructed separately and assembled together at the offshore site where the structure is used for drilling and/or production.

1 . A semi-submersible floating offshore structure, comprising: 
 a. a buoyant hull; and    b. a truss frame rigidly attached to said buoyant hull.    
     
     
         2 . The semi-submersible floating offshore structure of  claim 1 , wherein said hull is comprised of a plurality of columns supported at their lower ends by at least two pontoons and topside structural framing connecting the columns together at their upper ends.  
     
     
         3 . The semi-submersible floating offshore structure of  claim 1 , further comprising at least one horizontal plate attached to said truss frame.  
     
     
         4 . The semi-submersible floating offshore structure of  claim 3 , wherein the horizontal plate on said truss frame spans across the horizontal plane of said truss frame.  
     
     
         5 . The semi-submersible floating offshore structure of  claim 1 , further comprising adjustable ballast means included on said truss frame.  
     
     
         6 . The semi-submersible floating offshore structure of  claim 5 , wherein said adjustable ballast means comprises a keel tank.  
     
     
         7 . A semi-submersible floating offshore structure, comprising: 
 a. a buoyant hull;    b. a truss frame rigidly attached to said buoyant hull; and    c. adjustable ballast means included on said truss frame.    
     
     
         8 . The semi-submersible floating offshore structure of  claim 7 , wherein said hull is comprised of a plurality of columns supported at their lower ends by at least two pontoons and topside structural framing connecting the columns together at their upper ends.  
     
     
         9 . The semi-submersible floating offshore structure of  claim 7 , wherein said adjustable ballast means comprises a keel tank.  
     
     
         10 . The semi-submersible floating offshore structure of  claim 7 , further comprising at least one horizontal plate attached to said truss frame.  
     
     
         11 . The semi-submersible floating offshore structure of  claim 10 , wherein said horizontal plate spans across the horizontal plane of said truss frame.  
     
     
         12 . A semi-submersible floating offshore structure, comprising: 
 a. a buoyant hull;    b. a truss frame rigidly attached to said buoyant hull; and    c. at least one horizontal plate attached to said truss frame.    
     
     
         13 . The semi-submersible floating offshore structure of  claim 12 , wherein said horizontal plate spans across the horizontal plane of said truss frame.  
     
     
         14 . The semi-submersible floating offshore structure of  claim 12 , wherein said hull is comprised of a plurality of columns supported at their lower ends by at least two pontoons and topside structural framing connecting the columns together at their upper ends.  
     
     
         15 . The semi-submersible floating offshore structure of  claim 12 , further comprising adjustable ballast means included on said truss frame.  
     
     
         16 . The semi-submersible floating offshore structure of  claim 15 , wherein said adjustable ballast means comprises a keel tank.  
     
     
         17 . A semi-submersible floating offshore structure, comprising: 
 a. a buoyant hull;    b. a truss frame rigidly attached to said buoyant hull;    c. at least one horizontal plate attached to said truss frame; and    d. means included on said offshore structure for adjusting the ballast of said offshore structure.    
     
     
         18 . The semi-submersible floating offshore structure of  claim 17 , wherein said hull is comprised of a plurality of columns supported at their lower ends by at least two pontoons and topside structural framing connecting the columns together at their upper ends.  
     
     
         19 . The semi-submersible floating offshore structure of  claim 17 , wherein said means for adjusting ballast comprises a keel tank.  
     
     
         20 . The semi-submersible floating offshore structure of  claim 17 , wherein said horizontal plate spans across the horizontal plane of said truss frame.  
     
     
         21 . A method for attaching offshore equipment together, comprising the steps: 
 a. floating a first equipment piece into position;    b. floating a second equipment piece into position near the first equipment piece;    c. moving the first and second equipment pieces into alignment with each other;    d. adjusting the ballast of at least one of the equipment pieces to cause the first and second equipment pieces to move closely adjacent each other; and    e. rigidly attaching the first and second equipment pieces together.