NGH Chain: Gas-Transportation Concept

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 12807, "NGH Chain: A New Gas Transportation Concept," by T. Kawasaki, K. Bando, and Y. Suehiro, SPE, Japan Oil, Gas, and Metals National Corporation, prepared for the 2008 International Petroleum Technology Conference, Kuala Lumpur, 3-5 De cem ber. The paper has not been peer reviewed. In general, long-distance liquefied natural gas (LNG) transportation projects are economically feasible for very large natural-gas reserves volumes. Japan Oil, Gas, and Metals National Corporation and Japanese engineering companies have focused on natural-gas hydrate (NGH) as a gas-transportation concept. It is important to consider optimizing the process and to understand the effect on the chain and optimize the entire NGH chain. Background Many medium and small gas fields within 6000 km of Japan are difficult to develop by conventional techniques, such as LNG and pipelines. NGH may be an economical gas-transportation method. NGH contains 170 times the gas volume compared with liquid or gaseous states. Therefore, initial cost of the NGH process is estimated to be less than that for LNG. LNG transportation is economically feasible for long-distance transportation. Pipelines are suitable for relatively-short-distance transportation because of higher capital cost. NGH transportation is a solution for small-to-medium-scale or remote gas fields, as shown in Fig. 1. Feasibility studies shown in Fig. 2 indicate that NGH transportation has an economic advantage for suitably sized gas reserves and transportation distance. Several systems have been developed to form NGH, including the bubbling/stirring-type formation reactor, the water-spraying-type formation reactor, and a hydrate-formation system that uses microbubbles with a tubular reactor, which obtains a higher formation rate than the other systems. Further improvement is needed in the precision of the feasibility study along with advances in technology. Conceptual Design The purpose of this study was the life cycle carbon dioxide (LCCO2) analysis of natural-gas transportation to Japan as NGH. In the selected model, natural gas is converted to NGH at the production plant and delivered to Japan by an NGH-carrier ship from existing undeveloped natural-gas fields in coastal areas of Southeast Asia. The base case production rate was 1×106 tonnes/a of LNG equivalent with a transport distance of 6000 km. The study presumed that the gas would be used in a power plant. LCCO2 Analysis The scope of investigation includes processes between the production facilities (including inlet-gas treatment) and the regasification facilities.