Outboard pontoon semi-submersible offshore platform

Abstract

An “outboard pontoon” semisubmersible floating platform for the use of offshore applications has a hull configuration including vertical deck support columns and a horizontally disposed pontoon structure. The vertical columns support the deck structure at upper ends and adjoin pontoon at their lower ends. Under the premise of ensuring platform stability, structural feasibility, and structural cost efficiency, the pontoon is horizontally extrapolated as far as possible radially outward from platform center in the horizontal plan while the elevation of the bottom of columns ranges anywhere from the pontoon bottom to the top surface of the pontoon. The vertical columns are adjoined to the pontoon from its inner periphery and the central vertical axis of each column resides a distance inward from the closest point of the center line of the pontoon. This arrangement makes part of pontoon become the “outboard pontoon” which is the important concept introduced by this invention. The “outboard pontoon” and the raised bottom elevation of the vertical columns will play an important role to reduce the vertical motion response of the platform to the sea waves, which has solid theoretical basis in hydrodynamics. Risers can be supported on the pontoon and columns, be extended to the deck, and the structure can be anchored by mooring lines extending along the outboard face of the outboard columns extending radially outward and downward from their lower ends.

What is claimed is: 
     
         1 . It will be observed in the eight preferred embodiments that the columns ( 11 ) are depicted as substantially square/rounded square or circular members and the pontoon-ring ( 12 ) configuration is depicted as substantially circular, rounded triangle, rounded square or square with extension. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms and not intended to be limiting. While eight preferred embodiments of the invention have been shown and described, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follows:
 1. An “outboard pontoon” semisubmersible floating platform, comprising of:
 a) a horizontal pontoon connected by the bottom of columns with auxiliary reinforcing structures as needed to form a sustainable pontoon-ring. The said pontoon-ring is horizontally extrapolated as far as possible radially outward from the center of the platform in the horizontal plan to form parts of the pontoon-ring as the “outboard pontoon” as illustrated in these eight preferred embodiments; 
 b) at least three support columns that extend upwards from their bottom parts where the pontoon ring is connected, and a deck which is supported by the columns above the water surface on the upper ends of said columns. The bottom elevation of said columns can ranged from the pontoon-ring's bottom elevation to the pontoon ring's top surface elevation. While the preferred elevation of the bottom of the column is at the same elevation of the pontoon's top surface, other elevations within the range may be used as well depending on circumstances. 
 c) Vertical columns in which said column's lower ends are adjoined to the pontoon's inner ring. And, there exists a distance between the central vertical axis of each column and the closest center line of the pontoon. The bottom portion of said columns may be partially imbedded into said pontoon-ring as illustrated as in the preferred embodiments for the safety and convenience of structural design and for the reduction of overall dimension in the horizontal direction of the platform. 
   2. The platform of  claim 1  where said pontoon-ring may have the horizontal cross-section of, but not limiting to, a circular, rounded triangular, rounded square or other polygon form, or have extended portions as illustrated in the preferred embodiments.   3. The platform of  claim 1 , wherein said columns have at least three of them. The number of said columns may be four, five, six, seven or eight that have the same features as claimed in the  claim 1  and distributed along said pontoon-ring.   4. The platform of  claim 1 , wherein said columns have horizontal cross-sections of, but not limited to, circular, square/rounded square, rectangular/rounded rectangular or other forms of polygons.