Will At-Shore FLNG Drive Low Cost Monetization and Export of Pipeline Gas? An Examination of Concept Features, Opportunities and Challenges

摘要

The context of the paper is the emergence of material gas resources available as pipeline gas in North America. Russia and Australia, which has led to the evaluation of liquefied natural gas (LNG) liquefaction as an attractive route for monetization. At-shore or inshore floating liquefaction is under serious consideration as a scalable, cost effective, risk mitigated architecture for the development and export of such reserves. Onshore liquefaction projects have many challenges including regulatory, social license to operate, First Nations consents, in addition to challenging geotechnical and topographical suitability of sites. At-shore or inshore FLNG, the paper will demonstrate, provides an attractive development option for the export of pipeline gas to global markets. The remote construction possible with the FLNG option offers potential reduction in investment outlay, and reduced dependence on incountry skilled labour pool often stressed by projects in a parallel time frame. The FLNG feed gas will be sourced from pipeline grids flowing conditioned gas and this alleviates the feed gas treatment required prior to liquefaction. The benign metocean at-shore offers the added benefit of designing fractionators, cryogenic exchangers and other sensitive equipment with reduced design margins and allows adoption of more conventional design of storage and offloading systems. Further topsides simplification can be achieved by locating power generation, control room and living quarters off the floating unit and adjacent to the jetty. The paper contrasts this with the metocean challenged, and now commercialized, offshore FLNG concept where the feed gas is typically sourced from subsea wells/subsea gathering system. The raw gas must be fully treated on the FLNG in readiness for liquefaction. The flow assurance issues - reception of slugs, pulsating gas flow - and the motions arising from the offshore metocean environment adversely impact topsides process performance and hence reliability. The paper will draw on recent studies and projects to demonstrate the following: 1. The potential benefits arising from the scalability of the architecture, including the potential for capacity development in line with reserves and market growth. 2. Key differences in process line-up for gas reception, gas treatment, NGL extraction and choice of liquefaction circuits relative to offshore FLNG. 3. Measurable simplification in technology and design feasible for at-shore FLNG arising from the reduced motion envelope. 4. Mitigation of nearshore environmental impact arising from deployment of FLNG at-shore or inshore (via site selection, choice of cooling medium e.g. air-cooling versus sea water-cooling to eliminate inshore seawater temperature rise) 5. Credible TIC metrics ($/mta) for at-shore floating liquefaction, expected economic payback and implementation schedule advantage relative to onshore deployment Through the above critical assessment the paper provides key inputs and insights as development guidance to the evaluation of at-shore FLNG for monetization and export of pipeline gas.