Drilling rig Falrig 78 after completion of repairs ready to be lowered back into the water

Project Summary

With limited dry dock capability in the Gulf of Mexico, the possibility of dry docking the submersible drilling rig Falrig 77 on a Crowley 400 class submersible barge was investigated. Given the draft of the rig, including its mud skirt, the required barge submersion draft was well over its original design limit. Structural analysis of the barge bulkheads however showed that the barge could safely be submersed to the required draft. Structural analyses of the barge deck and rig bottom frames showed that the cribbing block loads were acceptable.

Late December 1996, the Falrig 77 was loaded onto the barge 400-7 in Mobile, Alabama, for maintenance and repair of the mat structure. Upon completion of the work, the rig was safely lowered back into the water and floated off.

Scope of Work

The project scope included:

• Structural analysis barge bulkheads, subjected to hydrostatic pressure;

• Structural analysis barge main deck, subjected to large local block loads;

• Design cribbing arrangement, using available wood blocks;

• Structural analysis of rig bottom frames, subjected to large block loads;

• Structural analysis of the unsupported rig overhang;

• Design ballast procedures for loading and offloading;

• On-site assistance during the offloading of the rig.

This project was a joint venture between Argonautics Marine Engineering and Technical Salvage Advisors, Inc. After completion of the Falrig 77 dry docking, Falcon Drilling Company decided to also dry dock its rig Falrig 78.

Project Photographs

Details of cribbing blocks at barge deck edge.	Rig mat overhanging the barge on both sides.	Barge slowly ballasted under water with a small list and a large trim.	Rig free floating again, under control of pusher boats.