Single Point Mooring System for an Offshore LNG Import Terminal

Abstract

The paper describes the conceptual design of an offshore LNG import terminal based on the 'Bishop Process', sited on Vermilion, block 179, offshore Louisiana. It clarifies the Basis of Design for the complete terminal and describes the design and verification process followed for the Single Point Mooring ystem for offloading of LNG. The work done to date confirms the technical and economical feasibility of the concept. Although new in configuration, most of the individual components have been in use for LNG terminals and SPM systems for a long time. Introduction The US is currently by far the world's largest gas market. Of the current supply 85% is produced within the US, and 15% is imported; 98% from Canada and only 2% in the form of LNG. Whereas US demand is expected to grow with 2% per annum, the current U.S. gas production shows an increasing intrinsic decline rate and more undiscovered gas reserves are needed each year to keep up with demand. E&P operations in new frontier areas (e.g. the Alaskan North slope) are unlikely to be allowed in the near future and gradually the realization is dawning that only large scale LNG imports can meet the expected demand and stabilize the price of natural gas. In its annual outlook for 2004 the US Energy Information Administration predicts that LNG imports will grow from a modest 0.2 tcf in 2002 to 4.8 tcf or 15% of expected total supply by 2025[1]. Although new liquefaction projects for gas are being sanctioned, community concerns, congested ports, security and cost considerations are seen to frustrate the development of significant increases in capacities to receive LNG in the US but also in Europe. This paper describes the conceptual design for an offshore LNG import terminal based on the 'Bishop Process', which is developed as part of a research project sponsored by the US Department of Energy's National Energy Technology Laboratory. Ten companies, ranging from operators, mid stream companies, contractors and equipment vendors are participating in this project. The objective of this cooperative research is to design, construct, field test and evaluate the performance of key components of a salt cavern based LNG receiving facility and to describe their application in LNG receiving facilities in the Gulf coast and North-East US. Salt cavern based LNG import terminals have material advantages over tank design terminals in capital costs, operating costs, volume of storage, send out rates, security, and acceptance by the community[2]. As a consequence of the abundant appearance of salt formations found in the Gulf region in combination with hydrocarbon accumulations, the concept has very high potential in this region: not only is the connecting infrastructure to the US gas distribution system in place, it is also underutilized because of declining production and thus there is capacity available to handle large volumes of LNG imports.