1. Introduction

With an increasing diversification of LNG supply sources, caused by a growing number of liquefaction plants around the world, an increase in short-term trade and a general trend toward a worldwide liberalization of gas markets, reception terminals need to deal with a greater variety of incoming LNG qualities.

With the need to reduce capital and operating costs, existing storage capacity must be used to its maximum extent and the capacity of new storages must be optimized.

It is within this context, and as a response to the above mentioned trends, that GAZ de FRANCE has developed a software model called LNG MASTER which can accurately predict the behavior of LNG in storage tanks.

Gaz de France itself found its use invaluable when it agreed to receive on a regular basis from 1999 on, at the Montoir-de-Bretagne LNG receiving terminal, LNG from Nigeria for the ENEL Italian company.

The structure of this paper is the following :

  • In a first step, the French context with a diversification of LNG sources is given for memory.

  • In a second step, we will explain the challenges which are often faced by the terminal operators who need to handle different qualities of LNG concurrently in the same storage tanks. Effects such as stratification, rollover, or flashing will be explained. Some practical rules to manage such cases will be given.

  • In a third step, we will present the LNG MASTER software developed by GAZ de FRANCE, a real operational tool allowing operators to optimize LNG tank management.

To conclude, typical case studies will be presented as examples of the use of LNG MASTER at the design stage or when operating an LNG terminal.

2. French context, The level of importations are increasing at the two French LNG receiving terminals within a context diversification of LNG sources of diversification of LNG sources, in particular at the Montoir-de-Bretagne terminal where LNG tank management has been optimized while simultaneously undertaking modifications works at the terminal.

A long term contract was signed in 1992 between the Nigeria LNG Company and Gaz de France for the reception of 0.5 bcm/y of natural gas. Moreover, Gaz de France signed a "swap" contract with ENEL in 1997 to receive Nigerian LNG in exchange for gas redeliveries from Gaz de France's existing basket of supplies. The map hereafter shows the swaps. As a consequence, the Montoir-de-BLOCK 3 - - FORUM 17 257


Bretagne LNG receiving terminal, on the Atlantic coast of France, required some adaptations in order to receive these additional quantities of LNG.

ENEL CONTRACT: Swaps dash lines: previous exchanges 0.3 Bcm/y Norvegian befor

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