Abstract

On May 20, 2011 Shell announced final investment decision on the Prelude Floating LNG project in Australia. The decision means that Shell is now ready to start detailed design and construction of what will most likely be the world's largest floating offshore facility

Shell's approach to FLNG is to design for high reliability and availability. Based on safety, longevity, applicability over a wide range of anticipated feed gas compositions and met-ocean conditions.

Floating LNG is much more than just a liquefaction plant built on a ship. FLNG connects upstream gas processing directly with the liquefaction plant. Both processing and liquefaction effectively take place on top of the cryogenic LNG storage tanks. The same storage tanks from which the LNG will be pumped into the visiting LNG carrier which will moor along side. And all of this is built on a plot space one-quarter the size of an equivalent plant on land.

The overall availability of the upstream, processing, and the product offloading facilities is essential to obtain robust project economics. A series of availability studies for different elements of the chain have been performed to optimise hardware line up and sparing. For the upstream and the liquefaction part we could largely build on existing knowledge, however special attention had to be given to "close coupling" of the FLNG and the wells as well as to product offloading. Close coupling means that the traditional buffer capability of transmission lines is not present. Extensive dynamic modelling was performed to understand this in depth. For the offloading dedicated basin test were conducted. Numerical models were developed to understand the limits in offloading, and to quantify offloading limits because of weather constraints. The paper will focus on the studies performed and the resulting enhancements made to the design, which lead us to expect an overall availability for Floating LNG equivalent to a land-based facility.

The development of FLNG is complex, hundreds of engineers from across the world have combined their experience and expertise to design the world's largest floating offshore facility. We believe that Shell's 45 plus years experience in LNG technology, LNG shipping and offshore operations, provide us with a sound launch pad for commercialising and applying floating liquefaction technology.

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