Demolition of Offshore Wellhead Topsides - Weight Engineering Challenges

Some of the platforms installed in offshore fields in India have exceeded their design lifespan but continues to operate. For these platforms to continue operating safely and successfully, major revamp is required. As the wellheads are in operation beyond their intended lifespan and requires revamping due to their heavily corroded state, decommissioning, removal and replacement of existing offshore structures presents technical and economic challenges to Operating Company's and Contractors, alike. Due to the age of these platforms, availability of technical/engineering data is minimal and often needs to be developed from scratch. The focus of this paper is on Weight Engineering and challenges in developing such data for a platform without as built information. The paper also touches on the different stages of executing the project including demolition engineering strategies applied, use of different installation aids to facilitate demolition etc during successful execution of Brownfield works in Mumbai High field by National Petroleum Construction Company (NPCC).