SHUTTLE TANKERS IN THE GULF?
IT'S AS EASY AS ATB

SIZES REQUIRED
Most operators considering ATB shuttle tankers for deepwater Gulf of Mexico service are looking at designs of at least 300,000 bbl and up to 500,000 bbl. These units are, size-wise, equivalent to 40,000 dwt and 70,000 dwt ships, respectively.

The 300,000 bbl size was calculated using a production level of about 80, 000 to 100,000 bbl per day production and multiplying by 3 days to account for any possible problems, delays, etc. and to reduce the overall number of vessels required, helping to reduce overall ship and barge traffic.

The 500,000 bbl size was determined using the fact that the existing refineries and infrastructure are set up to handle cargoes of 500,000 bbl. The larger units would also help to further reduce the numbers of vessels required and the number of connections and disconnections.

Both sizes seem to have merit as well as advantages and disadvantages.

Another consideration when discussing the connection system is size. Technologically speaking, according to manufacturers of these systems and designers of ATBs, it is possible to build a coupling system for ATBs up to and possibly beyond the 500,000 bbl size. There is a least one 380,000 bbl ITB currently in service. However the largest ATBs now in service are 250,000 bbl capacity units.

One major issue in both the design and operation of ATBs as shuttle tankers is of course how these larger ATB units will be viewed by the Regulatory Bodies involved. Shuttling is very similar to the tanker lightering already being done in the Gulf that has a proven safety record. Also, shuttling is already being done in other locations worldwide including the North Sea. Hence getting approval for shuttling of some sort when the environmental impact study is completed seems relatively certain. ML

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