Aker Philadelphia Shipyard Inc. began work this morning on the 12th vessel being built at the South Philadelphia yard since it began production in 2000 on the site of the old Philadelphia Naval Shipyard.

This ship will be the eighth in a series of 12 tankers built under a $1 billion agreement signed in 2005.

Under that deal, Aker American Shipping Inc., an affiliated company, buys the ships and leases them to Overseas Shipholding Group Inc. of New York, which then charters them to major oil companies.

The ship will be the same basic design as the others in the series but with additional equipment and modifications to make it highly maneuverable so that it can dock at floating offshore oil-well platforms.

It will carry crude oil from deepwater wells in the Gulf of Mexico to pipeline terminals onshore.

The previous ships in the tanker series were designed to carry finished petroleum products. The yard's first four ships, purchased by the Matson Navigation Co. of Oakland, now carry cargo packed in truck-size containers between California and Hawaii, Guam and two ports in China.