A small boat collided with an inactive oil and gas well about 50 miles south of New Orleans on Tuesday night, causing a small oil spill, the U.S. Coast Guard and the operator of the well said on Wednesday.
The accident occurred at about 7 p.m. local time on Tuesday, when a 42-foot (13-metre) offshore oil service boat, the Sea Raider, struck a wellhead owned by Swift Energy in inland water off Plaquemines Parish.
Swift said the well had not been used since 2008. It said the last test of the well, taken shortly before it was shut down, showed it was producing about 18 barrels of oil and 59,000 cubic feet of natural gas a day.
Swift said the collision had damaged the wellhead but that it "appears to be primarily releasing water and a small amount of oil."
The company said containment booms and skimming equipment had been deployed around the well to protect nearby shorelines.
A Coast Guard spokesman, Ensign Tanner Stiehl, said a small sheen had developed around the accident site. "We don't know the specific oil content," said Stiehl.
The Coast Guard was working with federal, state and local agencies plus Swift Energy on the response.
P.J. Hahn, director of Coastal Zone Management for Plaquemines Parish, said he had seen video shot by the Coast Guard during an overflight and that the wellhead appeared to be leaking "pure sea water" rather than oil.
The incident occurred about nine miles southwest of Port Sulphur, a small town along the lower Mississippi River some 50 miles south of New Orleans.
There has been a heightened awareness of spills of any magnitude since the Deepwater Horizon disaster that killed 11 rig workers and spilled millions of barrels of oil into the Gulf of Mexico in 2010.
Oil company BP is currently on trial in a civil case in New Orleans over the spill.
Potential liabilities stretch into the tens of billions of dollars if the judge determines BP or the other defendants were grossly negligent. Oil came ashore from Texas to Florida, threatening livelihoods and state economies dependent on seafood and tourism.
Swift Energy is an independent oil and gas driller based in Houston. The company pumps oil and gas in Texas and Louisiana and reported total production of around 35,000 barrels per day of oil and gas equivalent during the last quarter of 2012.