Extend the Service Life
The objective of the life extension process is to document acceptable system integrity or risk of failure to the end of the extended service life to conclude if the subsea system is fit for purpose of the extended life beyond the original service life for the structure, component or the complete subsea production systems.
A subsea design life extension study is normally done in two phases, first a condition assessment and then evaluation of possible degradation of the subsea parts and components.
The methodology of the life extension follows the guide lines in NORSOK U-009 Life Extension of Subsea Systems, however as the condition and/or degradation models are generally unknown, a risk based approach using the OREDA database failure rates could be applied to establish the degradation model of each system component.
Why the need for life time extension?
The technology for linking subsea wells to fixed and floating installations had evolved dramatically over the last decades. Subsea fields that were too small to defend the construction of a separate process platform could now instead be expanded with reasonable standard subsea wells that were linked to a process platform, a float or even to a land processing plant.
The multi-phase technology made it possible to send untreated well stream over ever longer distances. The development of smaller satellite fields became a profitable affair – which came in handy for the oil companies around the turn of the millennium when oil prices were at a very low level. One advantage of the subsea wells was that they were quick to install and put into production. The life time extension of the host platform and the subsea structures infrastructure will hence be the same as installed and with the standard design life of 20 or 25 years, these no need life time extension.