Is oil leaking in the Gulf from the BP spill site?

Reports of oil surfacing near the site of the Deepwater Horizon explosion are raising questions about its source and whether it is related to last year’s oil spill in the Gulf of Mexico – one of the worst environmental disasters in US history.

A patch of oil was documented last week about a quarter-mile northeast of the Macondo wellhead leased by BP. That site was plugged in July 2010 after about 4.9 million barrels (206 million gallons) of oil leaked into the Gulf.

On Wednesday, reporters from the Mobile, Ala., Press-Register published photographs and video of their discovery on the news organization’s website, which was in response to surveillance flights conducted the week before by two environmental groups – the Gulf Restoration Network and On Wings of Care. The Press-Register reported witnessing “blobs of oil rise to the surface and bloom into iridescent yellow patches” that later “expanded into rainbow sheens 4 to 5 feet across.”

The reporting expedition collected oil samples that later underwent chemical analysis at a Louisiana State University lab headed by Edward Overton, an oil chemist who was tapped by federal investigators to study the oil in the early weeks of the spill. Mr. Overton confirmed that the oil was south Louisiana crude, but because of the low concentration of samples, testing could not determine that it was MC252 – the specific oil that can be traced to the Macondo well.

“There is no way to say for sure whether the well is leaking, based on what is on the surface. Of course it is suspicious,” Overton told the Press-Register.

Other scientists involved in studying the oil spill echo Overton’s feelings, saying the large quantity of oil on the surface raises doubt the oil is the result of natural seeps – a phenomenon caused by the combination of oil and methane gas escaping from the seafloor. Natural seepage if often identified off the coasts of Louisiana and Texas and produces a much lower concentration of oil than spills caused by humans.

“Based on my experience in working and boating in this area, the amount of oil I have seen on the surface from recent photographs and videos is not normal,” wrote Bob Bea, a engineering professor at the University of California at Berkeley, in an e-mail. He organized an independent investigation of the spill that reported its findings to Congress.

Natural seepage from the seafloor typically occurs in shallow depths of 1,000 feet or less, says Michel Boufadel, chairman of the department of civil and environmental engineering at Temple University in Philadelphia, who worked with Overton following the BP spill. Since the Macondo site is 5,000 feet below the surface, the only way oil can get pushed to the surface is through a violent eruption on the seafloor, Mr. Boufadel says.

“It is possible the oil was brought up by a natural seep, but that’s not probable because the depth [of the Macondo site] is so significant.... The eruption has to be big enough,” he says.

BP is denying the oil originated from its wellhead or the two relief wells, which were permanently sealed with cement in September 2010. On Thursday last week, the company directed several remotely operated vehicles to the well and provided a live feed of the operation to officials from several agencies, including the US Coast Guard; the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE); the National Oceanic and Atmospheric Administration (NOAA); and state representatives from Louisiana, Mississippi, and Florida.

“All these people agreed that nothing from the video footage showed any indication there was leaking from the wellhead,” says Lt. Suzanne Kerver, a spokeswoman for the US Coast Guard’s Eighth District in New Orleans. Kerver says her agency also conducted multiple aerial flights to survey the area and found “no evidence” of oil on the surface of the water.

BP said in a press release that “small intermittent [nitrogen] bubbles were observed emanating from cement ports at the base of the wellheads.” This is a natural byproduct of the nitrified foam used to set the casing cement, says BP spokesman Daren Beaudo. The company does not regularly monitor the Macondo site for leaks, he says.

BP has also raised questions about the oil samples collected by the Press-Register. “We haven’t seen the samples that were reviewed that Mr. Overton looked at,” Mr. Beaudo says.

There are many reasons that oil appears on the surface in the Gulf of Mexico besides natural seepage, the Coast Guard says. They include leakage from pipelines, sunken platforms, active and abandoned wells, and vessels.

It is not uncommon that many cases involving surface oil remain unresolved. In 2010, the Coast Guard said that it received 2,231 reports of oil sheen in the Gulf; the origins of 372 cases remain unknown.

The disconnect between what environmental groups, media organizations, and academics are finding and the results from BP and federal authorities is causing some to say that an independent group is needed to monitor oil sheens in the region, particularly near the Macondo site.

“There’s still a ton of questions out there regarding where [the oil] is from, and it’s on the Coast Guard to figure it out and to let the public know,” says Dan Favre, communications director for the Gulf Restoration Network.

Professor Bea says it is difficult for independent investigators to verify assertions the leak did not originate on the seafloor or at the wellhead because BP, the Coast Guard, and BOEMRE are not releasing their evidence to the public.

“Purportedly, sea floor videos at and in the vicinity of the Macondo well have been gathered, not provided. Only ‘summary statements’ have been provided that have not given any definitive information on the sources of the oil escaping to the surface,” he wrote.

A BOEMRE spokeswoman said her agency would not comment on the situation.

Kerver of the Coast Guard said that she would “not speculate where these sheens came from,” but that the Coast Guard will soon post video feeds of the BP underwater surveillance on its website.