The Ships
The Regas Vessel that will serve Port Dolphin is a highly sophisticated ship designed to transport, store and regasify liquid natural gas. The vessel will receive LNG cargos from various specialized carriers when moored at Port Dolphin to allow uninterrupted flow of gas into the market, while it could alternatively pick up cargos at liquefaction terminals if needed. This vessel will be equipped with a dedicated regasification plant mounted on deck. Regasification involves warming the LNG to turn it back from a liquid into a gas.
The Concept
The Regas vessel is a modified standard LNG vessel. The main additions to a standard LNG vessel will be:
- A cylindrical trunk forward of tank no.1 to accommodate the submerged turret mooring buoy and swivel system
- Skid mounted regasification units on deck
- Bow and stern thrusters
- Supplementary electrical power supply
- Supplementary steam production for regasification
- The ship can be a converted LNG carrier or a new building, and will also be capable of traditional delivery of LNG. Conversion studies of our own vessels have been performed and no show stoppers have been identified.
LNG is pumped from the tanks and sent to regasification units mounted on the vessel’s deck. Pressure is boosted by large cryogenic LNG pumps. Steam generated by auxiliary boilers in the vessel main engine room produces the heat necessary to regasify the LNG in the regasification unit’s heat exchanger. The regasification units design has been developed by Hamworthy Gas Systems in Norway.
Regasified LNG is discharged via a turret and swivel through a mooring and unloading buoy connected to a riser and subsea pipeline, designed by Advanced Production Loading (APL) and based on their North Sea proven STL technology.
The containment system can be either reinforced membrane type, Moss spherical tank type or SPB type. The important issue is to ensure that the containment system is designed to allow for maximum operational flexibility with regards to filling levels to ensure that sloshing does not occur during operation in exposed offshore locations with partially filled cargo tanks.
Unloading Buoy
Unloading Buoy in Moon-pool
The Benefits
By discharging the LNG through a Regas Vessel the need for a land based receiving and regasification terminal will be redundant. This offers many obvious benefits, some of which are:
- No land or port requirements for the receiving terminal
- No physical encroachment to the local land based environment
- No visual impact from shore
- Shorter overall time to market
- Enhanced safety
- Higher delivery regularity, even in harsh weather conditions
The economics of the floating storage and regas ship system compares very favourably to traditional LNG receiving terminals for small to medium regasification volumes and short to medium shipping distances (up to 4000 miles/6480 km). The terminal may be used in harsh (and benign) environment worldwide.