One of the advantages of a floating LNG (floating Liquified Natural Gas) plant compared to an onshore plant is its capability to relocate from one location to another. For better economic opportunity, an existing FLNG plant is relocated to a new offshore location, 450 km away. Several studies are conducted prior to commencement of the relocation. One of them is to evaluate flow assurance issues before, during reconnection to the new facility, commissioning, start-up and subsequent operations. These aspects are evaluated through steady state and transient simulations, in particular to identify major issues that may require additional equipment or significant operational changes to mitigate the consequences arising from conditions at the new location.
The main objective of flow assurance study at the initial project stage is to identify and specify Long Lead Items (LLI). Two of the LLI aspects that had to be finalised early are pipeline size and distance between the gas exporting platform and FLNG vessel to meet FLNG's feed gas arrival temperature specification. At design flowrate, it is observed that Joule-Thomson (J-T) cooling resulted in fluid temperature arriving at FLNG riser below ambient temperatures. Parametric studies are also performed for commissioning, black start-up and gas ramp-up, based on operational experience at the first location. Recommended optimum start-up sequence is successfully employed during commissioning and recorded data is found to be comparable with results from simulations. Flow assurance is one of the critical considerations to relocate an FLNG vessel and associated systems to a new location. This paper explains how the study was done and shares the start-up experience for industry's first operational FLNG.