Abstract
FLNG (Floating Liquefied Natural Gas) as a means of monetizing offshore gas is now a reality with Technip being involved in the first two major projects. Both these projects incorporate side-by-side offloading of LNG from the FLNG to the LNGC (LNG Carrier) using loading arm technology. As FLNGs move into more severe environments, the side-by-side operation is no longer applicable and a solution providing greater environmental thresholds is required. Several tandem LNG offloading systems are proposed by the industry. They provide great safety separation distance between the vessels and high environmental thresholds, but they require the use of a dedicated LNGC fleet with Bow Loading Systems or the deployment of at least three floating LNG flexible lines of sufficient length, more than 300 meters, to reach the midship manifold of conventional LNGCs.
Since early 2015, Technip has worked with HiLoad LNG AS to develop a LNG loading system that combines the advantages of tandem stern-to-bow and side-by-side offloading solutions. The system is based on already proven or qualified technologies, allows a vessel separation greater than 100 m, high environmental thresholds and minimum length of LNG transfer lines without any modification to the LNGC. The system uses the HiLoad LNG DP (dynamically positioned) vessel for the position keeping of the LNGC parallel to the FLNG and Technip's cryogenic flexible pipes for the transfer of LNG and vapor.
The main focus areas in the studies have been the risk assessment of the parallel loading configuration and the assessment of the DP station keeping capabilities within predefined operating sectors, with the system being exposed to both steady and dynamic/changing environmental conditions. Black-out scenarios have also been investigated as part of the simulation work. The HiLoad DP system was able to keep the LNGC inside a tight operating ‘green' envelope during all investigated challenging metocean conditions. The HiLoad LNG Parallel Loading System has been concluded as a feasible, well suited solution, enabling a safe and robust LNG loading method with use of conventional LNGCs.
