The paper describes the assurance processes followed to verify the installation and in-place seismic performance of a jack-up rig operating on several sites as part of the Tangguh development offshore Papua Barat, Indonesia. The jack-up rig will operate in Berau/Bintuni Bay which is characterised by strong tidal and estuarine conditions that control the distribution of shallow sediments contributing to very significant vertical and lateral variability and active seabed transport. Papua Barat is classified as an ISO seismic zone 3 of moderate to high seismic risk. The combination of high seismicity and complex seabed conditions and the requirements to operate a MODU cantilevered over fixed platforms increased the level of modelling complexity required to determine the seismic response of the structures and their foundations. Initial leg penetration analyses were carried out following conventional approaches to determine the viability of the selected sites for rig installation followed by initial seismic soil-structure interaction analyses with equivalent linearised yield surface decoupled models that tried to demonstrate compliance with ISO 19901-5 recommendations. The outcome of these analyses was found to be non-conservative and a more sophisticated analysis method was implemented. This paper reports the site setting, site investigation data acquired including soil borings and dynamic in-situ testing, associated advanced dynamic laboratory testing and the Probabilistic Seismic Hazard Analysis including time history selection. It includes an overview of the non-linear 2-D, large displacement and 3D continuum finite element dynamic analysis undertaken, implementation of the analysis in the BP High Performance Computing facility and an overview of the results. The companion papers (Erbrich et al., 2020a, and Erbrich et al., 2020b) provide a detailed description of the full 3D continuum numerical modelling that was conducted. The analyses performed successfully demonstrated the structural conformance of the jack-up with the relevant requirements under design earthquake loading conditions.
Hugo Galanes-Alvarez, Armedito Ramadhan, Philippe Jeanjean, Kevin M. Hampson, Carl Erbrich and Kok Kuen Lee
Keywords: seismic, soil-structure, interaction, jack-up, Tangguh
Publisher: DFI