Meeting Your Customized Natural Gas Supply and Delivery Needs
EnerSea offers its marine CNG delivery service to clients based on their specific needs. The VOTRANS™ marine gas delivery service can be provided through fit-for-purpose ships or barges which are tailored to meet the project’s needs. EnerSea’s technology provides the ability to move as much as 1 Bcf or as little as 20 MMscf per vessel, at significantly lower costs than other gas export alternatives.The selection of ship type is dependent on several factors with the most significant factors being:
Rate and volume of gas to be transported
Distance to market
Vessel design drivers
Distance from supply to market
Vessel Gas Capacity 70-1000 MMscf 20-100 MMscf
Daily Deliverability 50-300+ MMscf/d 7-100 MMscf/d
Economic Range 250-2500 nm 50-750 nm
CNG offers clients great flexibility to meet gas supply and delivery objectives. For example, loading and offloading terminal facilities can be located at traditional port jetties at or near shore. If gas supply is offshore, buoys can be utilized. Gas compression and cooling can be located either at the client’s production facilities or onboard EnerSea’s vessels or, if onshore, at port. Offloading facilities can be located either at port or on EnerSea’s vessels, if offloading offshore.
EnerSea can also provide VOLANDS (Volume Optimized Land Storage), an innovative, above-ground compressed natural gas land-based storage system. VOLANDS can be integrated into a marine gas transport project, or can be provided as a stand-alone storage solution for clients in geologically constrained areas worldwide.
The heart of EnerSea’s ship-based marine gas transport service is its VOTRANS™ gas carrier. EnerSea has developed preliminary designs for ships with natural gas capacities ranging from 70 million cubic feet (2 million cubic meters) up to 1 billion cubic feet (30 million cubic meters) to provide clients with an optimum gas delivery solution. These vessels may be further tailored to confidently meet a project’s unique and demanding field requirements, such as capacity, supply conditions, gas composition, sea conditions and loading and offloading rates. These project specific requirements are normally defined in enough detail during FEED (Front-end Engineering and Design) to allow EnerSea to develop detailed ship designs. A typical VOTRANS CNG ship General Arrangement is shown.
The cylinders will be manufactured using 48” dia. high strength micro-alloy carbon steel with low temperature toughness and having a wall thickness that ranges from 22 to 25mm. The cylinders will be capped with semi-elliptical heads on each end. EnerSea has qualified pipe materials from Nippon Steel Corporation, JFE and Sumitomo during its Prototype Test Program, the results of which were approved by ABS and DNV-GL.
EnerSea’s CNG cargo containment system consists of an array of storage cylinders configured into multiple tanks (several cylinders manifolded together in a common pressure environment and controlled by the same valving) and tiers (two or more tanks configured to load and offload together). The numbers of cylinders, tanks and tiers are dependent on vessel carrying capacity and loading and offloading durations. The storage cylinders will typically reside in multiple insulated cargo holds, the number of which is determined by the overall ship capacity. The holds are inerted with dry nitrogen and equipped with refrigeration coils located at the top of each hold to offset environmental heat gain and thus preserve the internal temperature at 30°C (-22°F). This arrangement is inherently scalable and provides segregated gas storage.
The vessel has been designed to the ABS Guide for Vessels Intended to Carry Compressed Natural Gases in Bulk for structure and marine systems while the cargo containment system has been designed using API, ABS and IGC codes where applicable. The cargo loading and offloading systems have been designed to comply with ABS, IMO, API and other rules as applicable.
The ship’s lightship draft is designed to ensure that the vessel can be constructed and the cargo containment system installed entirely in dry dock. More importantly, this also allows the vessel to be dry docked in numerous ports worldwide for servicing and maintenance.
EnerSea has worked closely with globally recognized ship operators, shipyards and engineering and naval architecture firms in the development of the vessel designs, ship specifications and ship operating and maintenance plans.