Structural health monitoring and the accuracy of different monitoring period for ageing fixed offshore platform in Malaysian water

The oil and gas industry began in Malaysia in the early 1900s and has evolved over 115 years. Since 1990, Malaysia's gasoline consumption has increased at an annual rate of 7.2 per cent, reaching 44.9 Mtoe in 2008. The expected demands of oil and gas are increasing from 2010 until 2026. However, the energy sector, specifically in oil and gas, faces challenges as the resources have been declining in recent years. The oil and gas operators are pressured to improve their recovery of oil and gas resources hence needs to extend the operation of the platform beyond its design life. In order to do that, reliability engineering has become a common practice in the Malaysian oil and gas industry to access the integrity and requalification of offshore platforms in the late 1990s. However, accidents involving maritime structures has been occurring for a long time. For example, the MS Estonia involved 852 fatalities in 1994, whereas the Ranger I reported 84 fatalities in 1970 (Gulf of Mexico Jack-Up), and the Alexander Kielland semisubmersible reported 123 fatalities in 1980 (North Sea). The standard design life of the fixed offshore structure ranges between 20-30 years. In 2019, PETRONAS operated over 200 fixed offshore structures in Malaysian waters, which over half of them have outlived their design lives. Various standards and guidelines are introduced globally to ensure the extended lifetime of the fixed offshore platforms are safe to be used. However, the current development of structural health monitoring focuses on developing the technology, and only limited guidelines and standards discuss the optimum or recommended duration for the monitoring. Therefore, this study aims to determine the optimum monitoring period for deploying structural health systems at the fixed offshore platform. In this study, structural health monitoring (SHM) and wave radar system are used to collect data for the acceleration of the platform and the wave height hitting the platform. The data is then converted using Fast Fourier Transform to convert the time domain signal into a frequency-domain signal. The output is then used to investigate the impacts of different SHM duration assessments on the accuracy of the results hence determining the most optimum duration for the SHM assessment period.