Natural Oil Seeps in the Gulf Make BP's Task Even Harder

BP executives and government representatives are acknowledging that oil is now seeping from the sea floor near the original leak caused by the April 20 Deepwater Horizon rig explosion.

But whether the leak is a result of the well that BP claims it has successfully capped or a natural oil seep is debated.

Scientists have detected a "seep a distance from the well and undetermined anomalies at the well head," according to a July 18 letter from Thad Allen, the federal government's oil spill response director, to BP's Chief Managing Director Bob Dudley. In his letter, Allen did not provide information regarding where exactly the leak is located, how big it is or where the leak may be coming from.

While BP spokesman Mark Proegler told Reuters Monday that "Scientists have concluded that the seep was naturally occurring," Coast Guard officials aren't as sure. During today's press conference, Allen said that they are still analyzing the seep and trying to distinguish between the oil released naturally and the oil released from the well.

Officials are worried that the newfound seep may be the result of the cap placed on the well to keep the oil from pouring into the Gulf of Mexico. Underground leakage could signify that the well would not be able to withstand the pressure of being shut off, if oil it is already beginning to leak from a secondary seep as a result of the well being capped.

Based on recent studies, there are possibly several thousand natural oil seeps located in the Gulf alone, according to Dave Valentine, a marine sediment geochemistry professor at the University of California, Santa Barbara who co-authored a study on the presence of natural petroleum seeps off Santa Barbara, Calif.

Most of these natural seeps only release a trickle of oil, Valentine told Life's Little Mysteries. Those trickles do add up however, as the National Research Council estimated that, annually, about 660,000 tons of oil seep naturally into the ocean. A sizable fraction of this is from the Gulf, according to Valentine.

Scientists can determine whether a seep is natural or man-made based on several factors, Valentine said. These include the context of where the seepage occurred, the chemistry of the seep fluids, the timing of when the seepage was first noted and whether there is a reasonable way for the oil to get from a well to the seep.

• What Were the Worst Oil Spills in History?
• Why Is the Gulf Oil Slick Red?
• Graphic: Anatomy of the Gulf Oil Spill

This article was provided by LifesLittleMysteries, a sister site to LiveScience.