Global Ultimate Strength Assessment (GUSA) for Lifetime Extension of Ageing Offshore Structures
E. Mat Sooma, M.K. Abu Husainb, N.I. Mohd Zakib, M.N.K. Mohd Nora, M.S. Ayoba and G. Najafianc
aPetronas Carigali Sdn Bhd, Petronas Twin Tower, Kuala Lumpur City Centre, Kuala Lumpur, Malaysia
bUTM Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, Kuala Lumpur, Malaysia
cSchool of Engineering, The University of Liverpool, Liverpool, United Kingdom.
Abstract:
Malaysia is the second largest oil and gas producer in Southeast Asia. The majority of jacket platforms in Malaysia have exceeded their design lifetime with various types of underwater structure irregularities. Therefore, it is essential to address the reliability of the jacket platforms in Malaysia due to ageing and increasing environmental loading. Global Ultimate Strength Assessment (GUSA) methodology was established to support detailed re-assessment applied in managing safety, integrity analysis and reliability by evaluating the ageing and existing offshore platform. It is a tool for the high-end analysis of structures risk based assessment and has been accepted by most of the major marine operator in offshore industry. The main purposes of this analysis are to manage the structure’s risk level over its remaining service life and to initiate cost efficient inspection or mitigation actions if found required. Probabilistic models which derived from structural reliability methods with the result from pushover analysis are used to derive the annual probability of failure of the structure over its remaining service life. The outcome of these analyses can efficiently assist in understanding the structure failure mechanism and correctly define relevant type of mitigation required. In this paper, the re-assessment of ageing platform over 30 years old, still in production is presented. Due to demand to prolong the production for another 25 additional years of design life, it has been evaluated in design level analysis in early stage. With the major modifications such as extension deck for multipurpose pump and outboard conductors have gave impact to overstressed and fatigue issues.
For more details: ISOPE [ISBN 978-1-880653-89-0; ISSN 1098-6189]
