Abstract

Natural gas is one of the important energy resources and the worldwide consumption is rapidly increasing. To satisfy such a demand of the natural gas, a number of gas fields are under development in hostile conditions such as deep seas and arctic areas. However, due to the status of current technologies and economic situations, many gas fields in offshore are stranded. The estimated stranded gas reserves are above 4,500 TCF in offshore areas. The proven technology options available to the offshore for the natural gas exploitation and transportation are extremely limited. Currently, the most popular methods of bringing the natural gas to market from distant locations are LNG (Liquefied Natural Gas) and PNG (Pipelined Natural Gas) technologies. However, these technologies require expensive capital cost for infrastructure constructions and huge proved gas reserves. Thus, in many situations, they are not available for the stranded gas exploitation and transportation. There exist alternative technological options to LNG and PNG technologies that can be considered for exploiting and transporting the stranded gas in offshore. They are CNG (Compressed Natural Gas), NGH (Natural Gas Hydrate), GTL (Gas to Liquid), and GTW (Gas to Wire). In this paper, the available technologies of CNG, NGH, GTL, and GTW have been reviewed and compared to LNG and PNG technologies to derive the most economical one in selected regions such as Mediterranean, Caribbean, Arabian Seas, and Sakhalin Island.

Introduction

Natural gas is one of the important energy resources and the worldwide consumption is rapidly increasing. Recently, its consumption is being accelerated because of growing environmental concern. Table 1 and Fig. 1 show worldwide natural gas consumption.1,2 To satisfy such a demand of the natural gas, a number of gas fields are under development in hostile conditions such as deep seas and arctic areas. However, due to the status of current technologies and economic situations, many gas fields in offshore are stranded. The stranded gas reserves are those that cannot be economically transported to the consumer due to the distance from the gas field to market or the extreme water depth for laying pipelines.

According to Oil & Gas Journal, discovered global reserves of natural gas exceed 5,000 TCF.3 It is estimated that over the half of these reserves are stranded. Another estimates from Enron suggest that up to 9,000 TCF of natural gas may be stranded worldwide because of the prohibitive cost of transportation in the form of gas or LNG and the inherent limitations of the gas markets. If we assume that half of the stranded gas resides offshore, this would be something above 4,500 TCF.3

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