As LNG continues its resurgence as a means of moving natural gas between supply and market areas (OGJ, Aug. 12, 2002, p.56), another oceangoing technology has moved closer to commercial use.
A consortium of EnerSea Transport LLC, Houston, Hyundai Heavy Industries Co. Ltd., Korea, and Kawasaki Kisen Kaisha Ltd. announced last month it had chosen ABS, Houston, to assist in developing standards for oceangoing vessels carrying compressed natural gas (CNG).
In late 2001, EnerSea had announced plans to commercialize its CNG-vessel technology, VOTRANS (volume optimized transport storage). ABS will provide "class approval in principle" for this technology, said the classification society.
In addition, the consortium has chosen the risk management and risk-assessment services of ABS affiliate ABSG Consulting Inc. to address the overall risks associated with the design, construction, and operation of the vessels, using both quantitative and qualitative studies, said ABS.
The society claims to have pioneered the classification of LNG vessels and to be the only one to have approved all accepted LNG-containment systems.
Seagoing pipeline
EnerSea Transport's VOTRANS concept provides the capability of moving up to 2 bcf/vessel of CNG over as much as 4,000 miles at, says the company, significantly lower total costs than LNG.
The company says VOTRANS is a "virtual sea-going pipeline" consisting of long, large-diameter pipes contained within an insulated, nitrogen-filled cold-box structure integrated onto a ship (diagram).
EnerSea says VOTRANS improves on previous CNG concepts by combining optimal storage efficiency, the ability to transport both lean and rich gas, an innovative offloading process, and significantly lower (~40%) compression requirements to increase vessel capacities and reduce costs.
Independent engineering, naval architecture, and economic analyses performed last year by Paragon Engineering Corp., Houston, Alan C. McLure Associates, and Groppe, Long & Littell confirmed technical viability, says EnerSea, and indicated the company could sell natural gas into US markets for substantially less than $3/Mcf.
Advantages of VOTRANS over LNG, according to the company, include:
- Lower total capital costs.
- Terminal facilities that make up less than 15% of total capital cost, compared with more than 60% for LNG.
- Gas losses minimized during processing and transportation to less than 7% compared with up to 20% for LNG.
EnerSea's development program calls for gas transportation and sales via VOTRANS by 2004 after obtaining regulatory approvals this year.
