Floating LNG (FLNG) technologies are being deployed to monetize mid-sized offshore gas reservoirs, avoiding constructing a sub-sea gas pipeline to a land-based LNG facility and export jetty. Containing the processing to an oceanic environment also reduces the impact on indigenous peoples as well as terrestrial flora and fauna. FLNG facilities also have the potential of serving multiple offshore fields over the life of the facility, thereby reducing the minimum size field that can be economically monetized. Three major decisions for FLNG topsides are pretreatment, liquefaction and driver technology selections, with major impacts on safety, weight, space, maintainability and sensitivity to motion. A fourth decision is selection of a new build hull or LNG carrier revamp. The take-away from this work is an understanding of the tradeoffs inherent in these selections, supporting tailoring an FLNG facility to business constraints. Cryogenic processing requires pretreatment for removal of water and carbon dioxide to prevent solids formation. The use of brazed or welded aluminum equipment, common in cryogenic processing, also requires the removal of mercury. Candidate pretreatment technologies will be covered with an emphasis on the advantages and drawbacks regarding weight, space, and sensitivity to both tilt and motion. Offshore liquefaction technologies are often novel and have few or no offshore references. The available offshore liquefaction technologies and Licensors will be presented. Because of the diversity of liquefaction technologies, the technologies will be grouped by refrigerant, and then these liquefaction categorizations will be compared with an emphasis on safety, scale, weight, and sensitivity to motion and efficiency. Application of mechanical drives for centrifugal compressors in an offshore environment is well-practiced. Given this maturity, types of technologies will be compared on power ratings, availability, maintainability, flexibility and weight, without referring to individual suppliers.
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