Patent ID: 7891909

Claim:
A semi-submersible offshore structure, comprising: an equipment deck disposed above the surface of the water; a buoyant hull coupled to the equipment deck and extending below the surface of the water; wherein the hull comprises: a plurality of vertical columns, each column having an upper end proximal the deck and a lower end disposed subsea; a plurality of elongate horizontal pontoons, each pontoon having a longitudinal axis, a first end, and a second end opposite the first end; wherein each pontoon includes a first node disposed at the first end and positioned below the lower end of one of the plurality of columns, a second node disposed at the second end and positioned below the lower end of one of the plurality of columns, and an intermediate section extending axially from the first node to the second node; wherein the first node of each pontoon has a width W 1 measured perpendicular to the longitudinal axis of the pontoon in bottom view, the second node of each pontoon has a width W 2 measured perpendicular to the longitudinal axis in bottom view, and the intermediate section of each pontoon has a width W 3 measured perpendicular to the longitudinal axis in bottom view; wherein the width W 3 of each pontoon varies moving axially from the first node to the second node; wherein the intermediate section of each pontoon includes a first transition portion, a second transition portion, and a middle portion extending axially from the first transition portion to the second transition portion; wherein the first transition portion of each pontoon extends axially from the first node to the middle portion, and the second transition portion of each pontoon extends axially from the second node to the middle portion; and wherein the width W 3 of the intermediate section of each pontoon decreases in the first transition portion moving axially from the first node to the middle portion, and the width W 3 of the intermediate section of each pontoon decreases in the second transition portion moving axially from the second node to the middle portion.