Patent ID: 7553106
Filing Date: 2009-06-30
Classification: B63B,E02D

Abstract:
1. A method for making a semi submersible drilling/production vessel comprising: constructing a plurality of buoyant individual columns each having a variable ballast compartment and a fixed ballast compartment, and an emergency ballasting system; forming a plurality of trusses; connecting together a first column with a second column using at least a first top truss; connecting a first bottom truss to the first and second columns; maintaining the columns a distance of at least 1.5 times a diameter of one column apart to reduce vortex induced vibration amplitude of the group of columns to that of the individual columns when the semi submersible is in a righted position; floating the connected first and second columns horizontally in water; installing at least a second top truss to the first column floating in water; installing at least a second bottom truss to the first column floating in water; installing at least a third top truss and a third bottom truss to the second column floating in water; installing a third column to the second top truss and the second bottom truss; connecting the third top truss and third bottom truss to the third column; connecting a horizontal plate on the bottom of the columns, forming an upendable, self righting semi submersible structure with a shallow draft of less than 30 feet; floating the semi-submersible structure horizontally in less than 40 feet of water to a location for installation; upending the semi-submersible structure; installing a deck over the upended semi-submersible structure; connecting the deck to the upended semi-submersible structure; and deballasting the semi-submersible structure with connected deck forming a semi submersible drilling/production vessel having a center of gravity below its center of buoyancy with a draft between 300 and 500 feet.