World’s First CNG Carrier Ship Approved for Construction

19 September 2006

The compressed gas carrier uses multiple coselles to store the gas.

Sea NG Corporation announced that the American Bureau of Shipping (ABS) has approved for construction its coselle compressed natural gas (CNG) ship. This is the first ship and cargo system in the world for the transport of CNG to be so approved by ABS or any other international marine classification society.

Coselle CNG ships will be deployed to carry moderate volumes of natural gas (30 to 500 mmscf) over medium distances (200 to 2,000 km), a segment of the marine gas transportation market that has not been economically served by pipelines or liquefied natural gas (LNG—the current mode of ocean-going transportation).

The coselle is a system for storing high-pressure gas in a coil of small diameter pipe. A typical coselle consists of ten miles of small-diameter pipe coiled into a carousel structure (coil + carousel = coselle).

Coselle cross-section.

Coselles range in size from 15-20 meters in diameter and 2.5-4.5 meters in height, and can weigh about 550 tonnes. A single coselle carries about 3.0 million standard cubic feet (mmscf) of natural gas, depending on coselle dimensions, and gas temperature, pressure and composition.

Sea NG has developed several coselle ship designs, ranging from a 16-coselle ship transporting about 50 mmscf of gas up to a 144-coselle ship transporting about 450 mmscf of gas. By contrast, a large LNG carrier can transport more than 140,000 cubic meters of LNG—which, when re-gasified, expands to about 84 million cubic meters, or about 3 billion cubic feet of natural gas.

Unlike LNG terminals, the Coselle CNG System requires minimal on-shore facilities. Gas can be loaded and discharged at simple port-side pipeline facilities, which greatly reduces environmental, land-use and financial concerns. Gas can also be trans-shipped at offshore buoys if a port is not accessible.