The return of the BP disaster?

Oil is resurfacing again not far from the location of the BP Macondo Well off the Gulf of Mexico, 15 months on.

Fifteen months after BP’s crippled Macondo Well in the Gulf of Mexico caused the worst environmental disaster in US history, oil and oil sheen covering several square miles of water are surfacing not far from BP’s well.

According to oil trackers with the organisation On Wings of Care who have been monitoring the oil since early August, rainbow-tinted slicks and thicker globs of oil have been visible.

"BP and NOAA have had all these ships out there doing grid searches looking at things, so hopefully now they’ll take a look at this," Bonny Schumaker, president and pilot of On Wings of Care, told Al Jazeera.

Schumaker, who has logged approximately 500 hours of flight time monitoring the area around the Macondo well for oil, said during her August 30 overflight of the area "we saw the slick cover roughly 10 miles in one direction and four miles in another".

Schumaker has flown scientists from NASA, USGS, and oil chemistry scientists to observe conditions resulting from BP’s oil disaster that began in April 2010.

BP, whose Macondo well gushed at least 4.9 million barrels of crude oil into the Gulf of Mexico after the Deepwater Horizon rig exploded and sank to the bottom, has denied that the oil is coming from their well.

On August 18 reports surfaced that a large swath of oil sheen was reported near the site of last year's oil disaster. BP officials, in coordination with the US Coast Guard, deployed two submersibles to investigate the site.

BP said their visual inspection confirmed there wasn't any oil released from the Macondo well, and that it observed bubbles from cement ports near the site of some of its Gulf wells.

"These observations are consistent with testing and sampling performed last year that detected nitrogen bubbles, a residual byproduct of the nitrified foam used in setting the wells' surface casing cement," the company said in a statement.

Aerial survey

After the report in Mobile Alabama’s Press-Register newspaper, the Coast Guard deployed a boat to Mississippi Canyon 252, the federal block about 40 miles off the Louisiana coast where the well is located, and also conducted an aerial survey of the site by helicopter.

"Both observed nothing," said Captain Jonathan Burton, who is based in Morgan City, Louisiana.

BP, in addition, said neither a vessel it had on the scene late in the day nor a science vessel on site throughout the day reported seeing any oily sheen.

However, a reporter from the Press-Register took samples of the sheen and sent them to Louisiana State University for analysis.

Edward Overton, a professor emeritus at Louisiana State University’s environmental sciences department examined data from the samples.

Overton, who is also a National Oceanic and Atmospheric Administration (NOAA) contractor, told Al Jazeera, "After examining the data, I think it’s a dead ringer for the MC252 oil, as good a match as I’ve seen."

He explained that the samples were analysed and compared to "the known Macondo oil fingerprint, and it was a very, very close match."

While not ruling out the possibility that oil could be seeping out of the giant reservoir, which would be the worst case scenario, Overton believes the oil currently reaching the surface is likely from oil that was trapped in the damaged rigging on the seafloor.

Al Jazeera asked BP to comment on Prof Overton’s findings.

"We can tell you that we recently sent a remote operated submarine down to inspect the Macondo well cap and the relief well cap," Tom Mueller, a press officer for BP America told Al Jazeera, "Both are intact and show no evidence of any oil leak. So no oil is leaking from the Macondo well."

Mueller said it is possible the oil is from natural seeps, "but that is not known yet".

BP’s Gulf of Mexico disaster is, to date, the largest accidental marine oil spill in the history of the petroleum industry. BP has used at least 1.9 million gallons of toxic dispersants to sink the oil, in an effort the oil giant claimed was aimed at keeping the oil from reaching shore.

The dispersants are banned in at least 19 countries, including the UK.

Sightings of the oil continue as independent groups continue to monitor the situation.

Phantom islands

Oil has been surfacing all over the northern quadrant of the Gulf of Mexico for several weeks now, according to residents.

Reports of slicks that meander for kilometres and huge expanses of oil sheen that look like phantom islands are becoming common again.

Fresh oil, only slightly weathered, has been washing ashore in areas hit hardest by last year’s disaster. These areas include Breton Island, Ship Island, the Chandeleur Islands, and northern Barataria Bay, Louisiana.

BP has reactivated its Vessels of Opportunity (VOO) Program to handle clean-up operations.

Natural oil seepage has occurred in the Gulf of Mexico for millennia, making it possible that these could cause new sheens. But scientists said their location, this close to the Macondo well, is intriguing.

There are some explanations beyond natural seeps, including the possibility that oil has been leaking from the broken riser pipe that connected the Deepwater Horizon to the well itself.

Another possibility is that heavier hydrocarbon constituents could have settled on the bottom during the disaster, and as bacteria have broken them down, lighter-density hydrocarbons are now slowly making their way to the surface.

The most troubling possibility is that the oil is leaking out of the ground beneath the capped wellhead, a situation that could be impossible to stop.