Compressed Natural Gas (CNG) marine transportation is poised to be a viable solution to bring stranded and associated gas to markets. This is being driven in large part by high gas prices and declining gas production in North America and high liquid fuel prices elsewhere in the world. CNG marine transport has a market niche between the volumes and distances that pipelines and LNG can economically transport. New technologies have emerged and become commercially viable to provide a CNG marine transportation solution, including TransCanada's ASME approved Gas Transport Module (GTM). There are a number of challenges with the CNG technologies and regulations that must be overcome before general acceptance is gained.
TransCanada PipeLines, being one of North America's largest transporters of natural gas, brings a unique perspective to this emerging technology. With over 50 years experience in high pressure gas handling and transportation systems, including experience operating a fleet of CNG transport trucks, TransCanada provides a different viewpoint than other marine company proponents.
This paper gives an overview of the challenges and advantages of CNG marine transport from a gas transportation system operator point of view. These include cost/reliability issues, risks, technical challenges, and the safety and operability issues for high pressure gas systems, all with regard to the economic realities of CNG delivered into the North American gas grid or other world markets.
With the increase in prices for oil and natural gas in recent years appearing to be a trend not a spike as in the 1970s, methods for transporting natural gas from either stranded reserves or to stranded markets are receiving increased attention. One method that has generated a lot of interest and development is Compressed Natural Gas or CNG marine transport.
While CNG transport is not new, the large scale application to marine transport has not been demonstrated. Proponents investigating marine CNG transport face obstacles to incorporate an "untried technology" into energy infrastructure plans. It is important in the development of these types of projects to rely as much as possible on simple, proven processes and equipment in similar operating environments. While the complete CNG marine transport system has not been demonstrated, most components are in operation in similar environments and this experience, when applied to the project, should alleviate most concerns.
The bases for "new" CNG transportation systems are not really new. In their paper "Marine Transportation of Compressed Natural Gas, A Viable Alternative to Pipeline or LNG"1 the authors from Fluor reference an early CNG marine operation, that of Columbia Gas Company, who in the 1960s developed and tested a CNG carrier using vertical steel pressure vessels (Figure 1).
In the late 1970s Texas Gas Transport Company was granted several patents for CNG truck transport and operated a fleet of CNG transport trailers. This technology was licensed to a Nova Pressure Transport, a subsidiary of Nova Corporation, predecessor to TransCanada that also operated a fleet of CNG transport trucks (Figure 2).