Foundation Design and Installation for Ichthys Structures

Carl Erbrich and Ian Finnie, Fugro AG

Presented by AGS WA together with EA Oil & Gas Group

Abstract

The Ichthys field is located about 220 kilometres offshore from the North West coast of Western Australia in average water depths of 250m. The field comprises a semi-submersible central processing facility (CPF), a floating production storage and offloading vessel (FPSO), subsea wells, umbilicals, risers, flowlines and an 885km gas export pipeline to Darwin.

The Ichthys Riser Support Structure (RSS) is a large subsea structure consisting of a 110m tall tower with a 130m wide arch supporting up to 25 flexible risers as they transition from the seabed to the CPF. The foundation for the RSS comprises a raft approximately 69m x 38m in plan with a central cut-out and 6.5m deep skirts installed in uncemented carbonate sediments through a combination of self penetration and suction assistance.

This presentation will include an overview of the Ichthys project and the foundation design considerations for the CPF and FPSO anchor piles and subsea structure foundations at the Ichthys field. It will follow on to describe in more detail the innovations adopted in the foundation design of the RSS to withstand the design load combinations and its validation during the installation.

About the Speakers

Carl Erbrich is the Technical Director for Fugro AG (previously Advanced Geomechanics). Carl provided technical leadership for design of the foundation for the Ichthys Riser Support Structure (RSS) and also the driven piles used to anchor the CPF and FPSO. Carl is Fugro’s lead technical authority on the behaviour of calcareous soils and has been central to development of diverse analytical and numerical models that capture their wide ranging and challenging properties. Carl has also authored many technical papers concerning offshore foundations and anchors, has developed a range of analysis software that are routinely used for design, and is considered to be a global authority on a number of geotechnical issues, including the design of suction installed skirted foundations, such as the foundation for the RSS.

Dr Ian Finnie was the Project Director for AG’s involvement in the Ichthys Project, from initially supporting JP Kenny with the FEED, going on to supporting McDermott with the detailed design of the URF component of the project. From before FEED and through to the current installation phases Ian has facilitated support directly to Inpex on many matters relating to the seabed at Ichthys and along the export pipeline route to Darwin. Ian is currently helping Inpex with further phases of the project, building on the knowledge gained during the foundation project. Ian is a chartered civil engineer and Vice-Chairman of the Society of Underwater Technology. Amongst other things, Ian has previously been the CEO of a State-funded research collaboration, Design Appraisal Manager of Lloyd’s Register and is currently Integrated Geosciences Lead for Fugro AG.

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