LIFETIME EXTENSION OF AGEING OFFSHORE STRUCTURES BY GLOBAL ULTIMATE STRENGTH ASSESSMENT (GUSA)

Abstract

Malaysia is the second largest oil and gas producer in Southeast Asia. Majority ofjacket platforms in Malaysia have exceeded their design life with various types of underwaterstructure irregularities. Therefore, it is essential to address the reliability of the jacket platformsin Malaysia due to ageing, increasing environmental loading and demand to prolong theproduction for a further 25 years. The main purpose of this analyses is to determine thestructure’s risk level over its remaining service life which is a vital information in managingageing facilities to cater for the demand of continuous production. Global Ultimate StrengthAssessment (GUSA) methodology was used to support detailed reassessment applied inmanaging safety, integrity analyses and reliability by evaluating the existing platform’s loading.It is a tool for high-end analysis of structures for Risk-based Assessment (RBA). In this paper,the reassessment of an ageing platform over 30-year-old, still in production is presented todemonstrate GUSA capability to perform the platform’s life extension evaluation. The outcomefrom these analyses can effectively assist in understanding the structure platform’s failuremechanism and correctly identify mitigation actions required. As part of the analyses, non-linearanalysis and probabilistic model as practiced in the industry were used in order to get ReserveStrength Ratio (RSR) and Annual Probability of Failure (POF) results. The accuracy andcomprehensiveness of this method will assist the industry, especially oil and gas fields’ operators,in decision-making, specifically in identifying problem-oriented-solutions as part of theirbusiness risk management in managing ageing facilities.