The hull forms of the sanctioned FLNG projects are all ship-shape with either internal or external turret systems. The cylindrical hull for FLNG application without turret system has been studied for years. Recently, Sansom and Ankarsward (2016) presented a six-column rectangular shape Semi for medium FLNG. In this paper, a conceptual study of an alternative, a Paired-Column Semi-Submersible (PC Semi) platform with spread moorings, is presented for a 1.5 MTPA FLNG application in Western Australia.

This study is a generic one to design an economical small FLNG which can be achieved through modular topsides layout, robust hull configuration and turret-less mooring arrangement without scarifying safety and operability. The aim of this study was to explore an alternative option within current industry capability to reduce the overall investment, complexity and risk as much as possible.

A PC semi has low motion characteristics with eight columns suitable for large storage requirements and can efficiently support large deck area for production facility with gas processing, treatment and liquefaction facilities, offloading facilities and Living Quarter.

This conceptual study presents a generic exercise of efficient topsides and hull configuration and layout with considerations of its constructability, transportability, installability and operability. Advantages of a PC Semi vs. a ship-shaped hull are addressed and highlighted. Standardized and phased approach with multiple small FLNG units vs. a single mega FLNG unit is also discussed.

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