LNG Tandem Offloading - A Qualified Technology Now Ready for FLNG Project

Abstract LNG offloading operations are critical for the FLNG deployment on fields subject to medium or harsh environmental conditions. In the oil industry, tandem offloading operations are routinely performed using flexible marine hoses in various project specific configurations. The challenge of offshore LNG transfer lies in the combination of constraints from both the cryogenic operational requirements and the aggressive marine environment. From 2006 onwards SBM Offshore has developed an EN1474-2 compliant flexible cryogenic marine hose for offshore transfer of LNG. In 2010, the hose design and fabrication received a Type Approval certification from both ABS and DNV. SBM then completed the qualification of both the cryogenic coupling and the LNG tandem transfer system. The LNG transfer system is located on the stern of the FLNG and is connected to a dedicated bow manifold on the LNG carrier. The line configuration is suitable to handle the boil-off gas and transfers the vapour back to the FLNG boil-off gas management system. For the safety of operations and to increase the operability weather window, this system is designed to be operated without support vessels or tugboats. The line deployment and retrieval operations are carried out in a similar fashion to oil transfer systems and benefit from years of field expertise. This paper describes the system and outlines the main operating procedures. It summarizes the qualification roadmap including concept review, design assessment and associated testing program. It also presents the design analyses that were carried out, concludes on the generic system performances and operations limitations, and highlights key integration issues.