With many of the offshore platforms around the globe well past their design life, developing targeted and cost-effective approaches to reassess and manage the life extension of these facilities is critical for operators. Although standards such as API RP 2SIM and ISO 19901-9 provide an excellent framework for management of the structural integrity of individual platforms, operators that manage a significant number of facilities need to develop strategies for overseeing the life extension of a fleet of aging multidiscipline assets, with the objective of maximizing return while maintaining an acceptable level of risk.
The paper presents a systematic risk matrix based approach to provide a predictive assessment of the residual lives of the offshore facilities using the available design and condition data, re-assessment results based on asset specific or grouped approaches, and existing inspection results and strategies. Weighting of the influence of each parameter, adapted for different asset classes to capture state-of-the-art approaches within each discipline or system, is used to predicted residual life. This method has the ability to handle sparse data and incorporate recent or planned modifications. The increased likelihood of failure with time due to damage or degradation, as well as other threats such as obsolesce, is captured through time dependent factors to provide an estimate of the residual life.
The method used provides a flexible assessment of the health and residual life estimates for assets from a sub-system through to a full field perspective based on the existing risk tolerance and management strategies of the operator. This provides operators with a valuable tool to assist in optimizing the life cycle costs for the field. If the overall risk profile is not acceptable, then high level what-if analyses can be performed and incorporated into the risk model to review likelihood or consequence reducing measures as the facilities age. This may include additional assessments (e.g. platform specific ultimate strength or fitness-for-service assessments of major equipment), changes to fabric maintenance or risk based inspection plans, load reductions, upgrading of instrumentation and control systems, implementation of strengthening, modification or repair programs, or decommissioning. Advisian has successfully applied this approach for both offshore and onshore assets.
Unlike most life extension programs which are typically limited to a single discipline, this method provides a flexible multidisciplinary approach with the ability to incorporate findings covering topside structures, pipelines, piping, rotating and static equipment, electrical and instrumentation for a whole of field assessment.