Loading-Out Mega Offshore Platforms from China: The Challenges and Solutions

Abstract Substantial tidal variations and limited quayside water depths for fabrication yards along the Yellow Sea impose considerable constraints on the loadout workability of heavy offshore structures constructed in the Far-East. Loadout describes the process of moving a completed structure from its construction location in-land to its final position on the deck of a Heavy Transport Vessel (HTV) ready for sailaway. This paper presents a case study for the skidded loadout of two 20,000-ton mega offshore topsides in China. The mega topsides are two out of six facilities making-up Marjan Gas-Oil Separation Plant No. 4 (MRJN GOSP-4) in the Arabian Gulf. To overcome low-tide restrictions and potential vessel grounding during loadout, an innovative solution was implemented whereby the HTV stern was retrofitted with removable external buoyancy tanks during this safety critical operation. The paper shows that this unique solution improved loadout workability from a few days to a few weeks per month over the course of the year. Clients and operators building similar assets in the Far-East can utilize this solution to enhance flexibility in their scheduled sailaway dates. For Marjan project, this innovative approach helped achieve timely sailaway and mechanical completion of the whole offshore GOSP complex.