New gas carrier concept

DUTCH specialist ship designer Sea of Solutions, partner in the Offshore Ship Designers group (OSD), has developed what it claims is a technically feasible and low-cost concept to exploit stranded gas fields. Stranded gas is in fields too far from main pipeline routes to make them economically viable.

Sea of Solutions has developed the concept of a long pipeline coiled inside a ship rather than laid out on the seabed; the continuous pipe CNG carrier. The gas comes out of the ground into a coiled pipeline in the ship and is delivered to the shore facility without need for expensive offshore installations or shipborne installations. The CNG carrier can cope with unprocessed gas direct from the well and the coiled pipe design avoids the need for large complex pressure vessels built into the ship.

Nick Wessels, sales engineer at Sea of Solutions, writes in the September edition of the OSD newsletter DESIGN Waves, “The advantage of this concept is that the investment is in the vessel itself and is not related to a specific offshore field. It is an attractive means to develop fields for which the production rate or total volume cannot be easily predicted.”

Sea of Solutions says it has worked out the optimum vessel size, cargo pipeline size and temperature and pressure of the stored natural gas for a typical stranded gas field. Optimal storage conditions are met with a cargo pressure of around 130 bar and temperatures as low as possible without cooling equipment other than using seawater. With an overall length of 240 m the ship can carry a coiled pipeline of about 218 km length at speeds of 15 knots. Typically, one load would equate to 515 MMscf of saleable gas.