Ken Stickney

kstickney@theadvertiser.com

Shell Oil Co. and the U.S. Coast Guard have finished their "skimming" operation in the Gulf of Mexico clean-up that began with an oil spill last week.

The oil recovery effort, which involved five vessels and 150 people, ended Monday afternoon, the Coast Guard said. Some 84,000 gallons of an oil-and-water mix was recovered.

Shell said one vessel would remain in the area to assess environmental impacts of the discharge, which began late Thursday morning with a broken pipe in the Glider Field, about 97 miles south of the Louisiana coast.

How much oil was recovered in the operation was not immediately revealed.

Discharge occurred Thursday

Shell said Thursday that a discharge of about 88,200 gallons of oil occurred late that morning, creating an initial oil sheen of about 2 miles by 13 miles. The company identified the source of the problem as a flow line that connects to a tension leg platform at the Glider Field.

The Glider Field lies 165 miles south-southwest of New Orleans in around 3,400 feet of water.

Shell bought the lease there in 1995 for $725,000, and held a 75 percent working interest in Glider then; Newfield held the rest. Newfield said Tuesday that it sold its interest to Shell in 2012. An earlier version of this story said Newfield still held the 25 percent interest. Development costs were about $150 million, according to offshoretechnology.com.

The website said the well was drilled in 1996 to about 16,000 feet.

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Production was shut in initially Friday, but resumed Sunday at the nearby Brutus Field. No additional discharges were reported following inspection of subsea infrastructures at the Glider Field, where production remained closed Monday. There was no loss of well control.

Sheen was moving westward

Shell said in an issued statement Monday that the sheen was moving westward but was not expected to reach shore. Air support tracked the movement.

No fisheries were closed Monday, the company said, and the Coast Guard said there have been no reported impacts to wildlife.

The skimming operation involved the use of infrared technology, the company said. ​Skimming involves trapping the oil within booms and collecting it off the surface.

The Bureau of Safety and Environmental Enforcement confirmed Monday that it approved Shell’s plan to recover the damaged flowline segment. A BSEE spokeswoman said the agency would review "any subsequent repair plans" before production restarts.

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BSEE also said late Monday it has appointed a team of BSEE engineers, inspectors and investigators to probe the incident to identify causes and "contributing influences" behind the discharge. The panel will make recommendations in a final report. No timeline was presented.

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Professor: Spill 'relatively minor'

The spill itself was characterized as being "on the low side" for volume of oil lost, a "relatively minor spill," according to Eric Smith, a professor at Tulane University and associate director of the Tulane Energy Institute in the A.B. Freeman School of Business in New Orleans.

The rupture occurred in what Smith said was likely an insulated 6-inch pipe along a pipeline fairly new in the Gulf of Mexico, which has some 31,000 miles of pipe, some more than six decades old.

Smith said skimming is something like using a vacuum cleaner on the water. He said some of the light, sweet crude oil found in the Gulf will evaporate in the sun; some oil will also be consumed by bacteria.

Oily water collected by skimming will probably be separated into oil and water components, with the water returned to the Gulf. How much oil was recovered is determined through the oil and water collection and separating process.

Oil may cause some risk to sea life — whales, porpoises — found far off shore, but probably does not pose a risk to shell fish, which are found close to shore, or shrimp, found mostly within 50 miles of shore.