Gas Pretreatment Considerations for Floating LNG

Global LNG demand is expected to continue to grow over the next two decades. Some of the new projects required to meet this demand will be developed with floating LNG (FLNG) technologies, to monetize mid-sized offshore reservoirs, eliminating the costly and technically challenging pipeline to a land based LNG facility. FLNG facilities have the potential of serving multiple fields over the life of the facility, reducing the minimum size field that can be economically monetized. The market has affirmed these benefits and projected LNG demand growth with the start of construction of several floating LNG facilities. Much recent attention has been given to offshore LNG ship-to-ship transfer, topsides layout and liquefaction technology selection for FLNG with lesser coverage of support systems, particularly gas treatment. This paper will address this void by providing an overview of gas treatment for FLNG, highlighting the pretreatment requirements for cryogenic processing that may be unfamiliar to those more grounded in FPSO technology. Cryogenic processing requires removal of water and carbon dioxide to prevent solids formation. The use of brazed or welded aluminum equipment, common in cryogenic processing, requires the removal of mercury. Gas treatment technology selection is impacted by constraints on safety, weight, space, maintainability, flexibility in modularization, and insensitivity to both tilt and motion. Candidate technologies will be explored.