There is an ever increasing need to extend the life of aging offshore structures beyond their original design life. Whether these structures are fixed offshore rigs or floating facilities, operators are continually looking for new inspection and mitigation techniques aimed at ensuring the integrity of the structure. Improved inspection techniques and mitigation when combined with a sophisticated Risk Based Inspection (RBI) program can serve to requalify and extend the life of offshore structures.

Degrading mechanisms such as corrosion and fatigue, overloading, excessive marine growth and accidental damage may affect the integrity of offshore facilities. Early Identification and addressing the degradation mechanisms can prevent a structural failure. Joint weld close visual inspection or MPI can provide assurance in fatigue performance of the joint and to be used in calibration of fatigue life and improve the inspection intervals requirements.

An oil field consisting of many well head platforms, a living quarter platform), a flare platform and a processing platform are the main focus of this paper. In-place, seismic, spectral fatigue and ultimate strength analyses were undertaken for the platforms to determine the criticality of members and joints. These analyses in combination with cathodic protection studies and available inspection data were used for requalification and life extension.

This paper documents the methodology for the development of the RBI program to support the requalification and life extension of the platforms. The RBI program was based on guidance from ISO 19902, with the likelihood and consequence of joint failure used establishing base line and to identify the number and intervals for scheduled inspections. The results of the baseline inspections and additional sensitivity studies were then used to optimise the RBI program.

This paper serves to highlight the finanacialfinancial benefits, efficiency and importance of developing an RBI program based on probability of failure and consequence to manage the inspection programs for platforms and other facilities, particularly where there is a requirement to requalify the facility and/or extend its life.

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