Low Heave Semi-Submersible Offshore Structure

Abstract

A semi-submersible structure with buoyant vertical columns and a buoyant pontoon. Unlike the typical semi-submersible where the pontoons are attached directly between the columns, the pontoon of the invention encircles the columns and is arranged outside of the columns. The pontoon encircling the columns simplifies construction and attachment of the pontoon and columns and improves the heave characteristics of the structure.

What is claimed as invention is: 
     
         1 . A semi-submersible floating offshore structure, comprising:
 a. a plurality of buoyant columns spaced apart from each other;   b. a buoyant pontoon attached at the lower end of the columns by a column-to-pontoon connector, with the pontoon arranged outside of the exterior perimeter of the columns; and   c. a topside attached to and supported at the top of the columns.   
     
     
         2 . The semi-submersible floating offshore structure of  claim 1 , wherein the pontoon is offset from the columns such that none of the vertical surfaces of the columns are in the same plane as the vertical surfaces of the pontoon. 
     
     
         3 . The semi-submersible floating offshore structure of  claim 1 , wherein the cross section of the columns is rectangular. 
     
     
         4 . The semi-submersible floating offshore structure of  claim 1 , wherein the cross section of the columns is circular. 
     
     
         5 . The semi-submersible floating offshore structure of  claim 1 , further comprising a heave plate that extends horizontally from the pontoon. 
     
     
         6 . The semi-submersible floating offshore structure of  claim 1 , wherein the corners of the pontoon are beveled. 
     
     
         7 . The semi-submersible floating offshore structure of  claim 1 , wherein the corners of the pontoon form a right angle. 
     
     
         8 . A semi-submersible floating offshore structure, comprising:
 a. a plurality of buoyant columns spaced apart from each other;   b. a buoyant pontoon attached at the lower end of the columns by a column-to-pontoon connector, with the pontoon arranged outside of the exterior perimeter of the columns; and   c. a heave plate extending horizontally from the pontoon.   d. a topside attached to and supported at the top of the columns.   
     
     
         9 . The semi-submersible floating offshore structure of  claim 8 , wherein the pontoon is offset from the columns such that none of the vertical surfaces of the columns are in the same plane as the vertical surfaces of the pontoon. 
     
     
         10 . The semi-submersible floating offshore structure of  claim 8 , wherein the cross section of the columns is rectangular. 
     
     
         11 . The semi-submersible floating offshore structure of  claim 8 , wherein the cross section of the columns is circular. 
     
     
         12 . The semi-submersible floating offshore structure of  claim 8 , wherein the corners of the pontoon are beveled. 
     
     
         13 . The semi-submersible floating offshore structure of  claim 8 , wherein the corners of the pontoon form a right angle.