Barge-Assisted Draft Reduction of Semi-Submersible Drilling Unit GSF Development Driller I for Tow-Out From Ingleside to Offshore Gulf of Mexico

Abstract

Because of its DP thrusters, the free-floating draft of the semi-submersible drilling rig GSF Development Driller I was too deep for a safe tow-out from Ingleside, TX, to open waters. In order to reduce the semi’s draft, a large cargo barge was used to lift the rig 1.0 m (3.3 ft) and thus create a reasonable ground clearance. The barge was selected, based on dimension, ballast capability, deck strength, price, and availability. Eight support brackets were welded to the barge sides and strong diaphragms welded inside the four rig braces. Detailed time domain motion analyses were performed to study the behavior of the combined units during the tow and barge removal operation offshore. In April of 2006, during a favorable weather window, the combined units were successfully towed through the channels and once in deeper waters, the barge was ballasted down and pulled out from under the rig.