Abstract
Iwaki-Oki Gas field which operated by OIP (Offshore Iwaki Petroleum Co., Ltd.) located at Pacific Ocean of Naraha-Chou offing. OIP started natural gas production from 1984, and finished operation at end of July 2007. After finishing operation, OIP needed decommissioning work of Iwaki-Oki Platform, and started study for it from 2004. This study consisted with several engineering, several preparation works of Platform decommissioning, procurement of HLV (Heavy Lift Vessel) and discussion with related governments.
OIP carried out deconstruction work for Platform decommissioning from December 2009 to July 2010. This deconstruction work included topside removal and Jacket toppling. Topside removal is dividing topside on Jacket into 16 blocks, lifting them by HLV respectively, and moving to a working table ship by HLV. And, Jacket was cut in depth-sounding the part of 92.5 meters, and was performing toppling.
One of key works of this deconstruction was subsea-cutting, and this key work was Jacket legs and main piles cutting by ROV (Remotely Operated Vehicle). In Japan, it was first case to use ROV for subsea-cutting. Another one was unique work, and it was made use of Jacket leg buoyancy for Jacket toppling.
This Platform decommissioning was completed by the time necessary for completion about 10 working days shorter than a plan. This work was also no-disaster.
