Floating LNG Systems - Export and Import Terminals
Authors: Denney Dennis 
Published: February 2015

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 17547, "Floating LNG - A Look at Export and Import Terminals," by G. Gervois, L. Daniel, N. Jestin, and A. Kyriacou, Saipem S.A., prepared for the 2005 Offshore Technology Conference, Houston, 2-5 May.

The liquid-natural-gas (LNG) market is experiencing unprecedented growth. Under certain conditions, a floating liquefaction terminal, or LNG floating processing, storage, and offloading (FPSO) vessel could make more sense than a distant onshore liquefaction terminal. Similarly, with the difficulty to set up a new onshore regasification plant, floating storage regasification units (FSRUs) make sense.

Introduction

Floating LNG systems combine LNG and cryogenic-fluid handling (processing and storage) with deepwater offshore experience (floating units). Floating LNG systems can be LNG FPSO export terminals or FSRU import terminals. LNG FPSOs address the need to monetize associated gas or the possibility to develop large standalone gas fields. FSRUs address increased gas needs from highly populated areas associated with the difficulty to set up new onshore LNG terminals.

The full-length paper details key aspects of LNG FPSOs and FSRUs. This LNG FPSO focuses on a concrete hull and how it accommodates the LNG containment system. The paper provides a technical overview of two FSRUs, one being a converted unit and the other being a large new-build, and some of the key parameters that differ between these facilities.

Gas Market

The long-term trend for the energy market shows a shift from heavy-carbon molecules (coal, then oil) to lighter molecules (methane). The gas market has been slightly more complex than the oil market because of the absence of a spot trading market. Operators must negotiate long-term sale agreements as part of the development scheme. Many types of projects have been conceived, but very few will actually be built. Placing a new terminal has many obstacles.

Floating LNG Systems. The size of a floating LNG project, compounded with the required technical expertise to bring such a project to fruition, tends to limit the number of providers. Because of the size of the projects, the number of operators able to develop a floating LNG system also is limited. Reasons for selecting a floating solution rather than an onshore solution include the following.Limited onshore infrastructure.Limited cost premium for going off-shore.Improved safety.Strong opposition to a shore-based terminal.Distance from shore or distance from infrastructures (specific to FPSO).

Concrete LNG FPSO

Most development projects have considered that topside facilities and storage capacities will need to be large to make the project economical. However, technologies have evolved to meet the requirements for floating LNG systems. Both steel and concrete hulls have been developed. Concrete is not new to marine structures, and the installation of LNG facilities on a floating structure is possible with several improvements in the design of the structure, in the process facilities in the LNG-containment system, and in the LNG offloading equipment.