An Approach to the Economic Optimization Of LNG Marine Transp9rtation
Authors: Reed E.E. , Johnson F.M. 
Published: October 2008

An approach to the economic optimization of LNG marine transportation is described and the practical limitations discussed. The importance of the effect of the shore facilities on the optimized system is emphasized. Inter-relationships of key variables are analyzed and graphically illustrated. Practical aspects of optimization such as "standard ship" designs and physical limitations are discussed. The quality of the results of optimization are shown to depend a great deal on accurate information from shipbuilders.

Introduction

The increasing demand for a clean energy fuel, along with recent advances in materials technology, has led to the rapid development of the Liquefied Natural Gas (LNG) carrier. In just a few years, these unique vessels have increased in size from a few thousand cubic meters cargo capacity to vessels on order of over 120,000 cubic meters. LNG carriers of up to 200,000 cubic meters capacity are being considered and can be expected in the foreseeable future.

The growing shortage of this premium energy in such places as the United states and Japan has made .importation of LNG into these areas an economically feasible venture. As the energy crisis intensifies, along with the concern for ecology, the demand for LNG importation can be expected to create a worldwide boom in LNG carrier construction.

The specialty nature of the cargo containmentand handling systems (LNG is handled atabout -258°F) makes the investment cost of an LNG carrier in the order of 2 to 3 times that of a conventional crude tanker of comparable dimensions. This high investment cost can make the marine transportation a very high portion of the overall delivered cost of LNG. And, since the marine transportation is logically integrated with the shore facilities, it can exert a strong influence on the size and subsequently the cost of the overall LNG project. Thus, the selection of the optimum marine transportation system is an important aspect of an LNG project.

How does one determine the optimum LNG maine transportation system? What is the magnitude of the problem? -What degree of accuracy can be expected? What are the practical limitations and critical areas? It is these and other questions dealing with the practical aspects of the optimization process that this paper attempts to answer.

Scope

It is, of course, necessary to define precisely the scope of the task. It should be first recognized that the marine transportation of LNG is usually a dedicated subsystem of an overall system which can include all facilities from the well-head at the source of the natural gas to the pipeline through which the regasified LNG is delivered to its final destination. All of the subsystems are, generally, interdependent and dedicated to the overall system. Thus, it follows that the best marine transportation system is the one that results from the optimum overall LNG system. All phases of the LNG project should be included in the optimization process. The wide range and specialized nature of the required expertise for each subsystem, along with the need for continuous updating of information, makes it convenient to develop an analysis process for each subsystem independently.