A World First – The Pohokura Project

SAL was appointed by Technip to design and execute a unique transportation concept for a 420 mtons steel jacket and an offshore wellhead platform.

The installation of this jacket and platform in the Taranaki Basin off New Zealand was a complex process that required a complete transport analysis and offshore operation procedures. Thus, SAL – in cooperation with their client Technip – engineered a method to rotate the 56 metre long steel jacket during the lifting process, keeping the structure 1 metre off the ground at all times. In a world first, the complex structure was turned from a horizontal to a vertical position, being placed into SAL’s MV Annegret, where it extended 42 metres out of the hatch into the sky.

The journey, that took 7 days travelling at a ‘reduced’ service speed of 18 knots through some of the most treacherous oceans, was managed in compliance with the rigid safety requirements of the Classification Society Germanischer Lloyd. In addition, the sensitive voyage was continuously monitored for changes in weather conditions via satellite by the Houston Weather Bureau.

"The challenge for the safe passage of the steel jacket has been analysing and predicting the sea, swell, wind and current patterns of the ocean, and chartering the smoothest course. This is only possible when you have a highly experienced, specialist scientific team including engineers, technical researchers and seagoing personnel. SAL is fortunate to have this team including Captains with extensive experience in Heavy Lift Shipping."

Master Mariner, Captain Hajo Bäker, Heavy Lift 
Superintendent / Offshore Loading Master.

Compared with traditional methods for sea transport utilising barges, SAL’s MV Annegret averaged a speed 3 times that of a barge, resulting in less fatigue on the structure and increasing its lifespan by around 10 years. 

For the offshore uploading of the structure, MV Annegret moored just 4 metres from the installation rig up which lowered the jacket to the ocean floor. In the past, similar operations have only been completed by barges. To ensure the viability of the first time procedure, a motion mooring analysis system including model simulations to predict mooring line tensions was conducted by the Classification Society GL in Germany and MARIN Maritime Research Institute in Netherlands.