Concrete Offshore LNG Terminals - A Viable Solution and Technical Challenges
Authors: Jiang Dajiu , Wang Ge , Montaruli Bret C. , Richardson Kenneth L. 
Published: October 2008

This paper discusses the feasibility of concrete offshore LNG terminals with a focus on applications in the Gulf of Mexico and other coastal areas of the United States.

There is an ever growing need to import more natural gas into the United States. Yet, this need is limited by the lack of infrastructure for receiving liquefied natural gas (LNG) from LNG carriers. In the search for safe, economical and environmental-friendly installations, concrete offshore LNG terminals are emerging as a very promising solution. A prestressed concrete structure has many advantages over steel installations, such as high resistance to cryogenic temperatures, high resistance to thermal shock, good durability in the marine environment, extended fatigue life, strong resistance against boat impact, fire, explosion, etc. There are, however, many challenges in design, construction, transportation and installation. Complicating the situation are the concerns over consequences of LNG leakage, boat impacts, fire explosions, etc., which are not fully discussed in the existing design codes.

Aiming at the feasibility of building concrete offshore LNG terminals, the paper presents in detail the major advantages and technical challenges in design aspects, construction, transportation and installation. It reviews the state-of-the-art technology, and refers to the successful experience of an offshore concrete platform in more harsh environmental conditions, the Hibernia concrete platform in Newfoundland, Canada.

Recently, ABS issued its ABS Guide for Building and Classing Offshore LNG Terminals, which provides a comprehensive guidance for design, construction and survey of concrete offshore LNG terminals. This paper highlights the ABS Guide, and addresses the regulatory requirements and class interface with the regulatory agencies.

1. Introduction

There is an ever-growing need to build offshore LNG import terminals in the Gulf of Mexico and other coastal areas of the United States. In the search for safe, economical and environmental-friendly installations, concrete offshore LNG terminals are emerging as a very promising solution. Figure 1 shows a concept of an offshore LNG terminal. ABS has approved it in principle. This LNG terminal is a concrete gravity base structure (GBS). Prestressed concrete structures have many advantages over steel installations [9,10,11]:Large volume to accommodate LNG tanks and topside facilities,Durable life in marine environment,Low maintenance cost,Variety of structural configuration,Excellent resistance to cryogenic temperature,Better resistance to fatigue and buckling,Stronger resistance against accidents of boat/vessel impact, missile attack, fire and explosion,Good sea station keeping capability.

Figure 1: Offshore LNG concrete GBS terminal [14] (Available in full paper)

There still remain many challenges in design, construction, transportation, and installation [9 to 13]:Relatively less experience,Only a few design codes and rules specifically devoted to concrete offshore LNG terminals,Design of high performance concrete,Material deterioration,Difficulties in quality control of field construction,Possible catastrophic shear failure,Lack of design experience about various accident scenarios, i.e., accidental LNG leakage, vessel impact, fire, explosion, etc.,Procedure of transportation and installation.