Natural gas can be brought to the consumer by a fleet of ships with compressed natural gas (CNG) technology.
Different proposals for transportation of gas by ship directly from the field to the consumer without the use of costly liquefaction, re-gasification and storage plants have been evaluated for many years. A new type of ship has been introduced having a large number of vertical pipes, designed according to enhanced pipeline design principles transporting compressed natural gas. The weight of the containment system is 50% less of the weight required by con-ventional pressure vessel design codes, making possible a large storage volume. Ships have so far been designed to transport up to 34 MSm3 gas on each voyage. The presented concept for compressed natural gas was introduced by Knutsen OAS Shipping and has been developed with assistance from EUROPIPE GmbH and Det Norsk Veritas.
Economic evaluations show that the new Knutsen PNG® is able to fill the gap in the medium range transportation between pipelines and LNG transport for distances up to 3,000 nautical miles. The advantage is less investment in infrastructure and greater flexibility. This new solution is best suited for so called stranded gas fields which are either to small or to far away from the marked to be connected economically by the so far known technologies, pipe line and/or LNG. The potential market for CNG carriers is large as more than half of the world’s known reserves are associated and stranded gas. These ships will serve as both storage and transport vehicles discharging directly into a land based gas grid via an on/offshore discharge terminal, an offshore platform or offshore buoys.
This paper outlines the principles, the development process of the containment design, the qualification testing and the PNG economics for different transport scenarios.