natural marine oil seeps
Posted by
alligatorob on 4/25/2010, 8:30 am
There are lots of sources where you can find good data on natural marine oil seeps, this one is probably better than the one in my original post: http://oils.gpa.unep.org/facts/natural-sources.htm
The source most folks cite for this statistic is the National Academy of Sciences book Oil in the Sea III, it costs about $50 but for anyone who really wants to understand the issues of marine oil spills and seeps it is a good resource ( http://www.amazon.com/Oil-Sea-III-Inputs-Effects/dp/0309084385/ref=sr_1_1?ie=UTF8&s=books&qid=1272198375&sr=1-1 ).
Specifically in the Gulf of Mexico studies have shown a lot of natural seepage, about 600 natural seeps have been mapped and on average they discharge as much oil in 6 months as the Exxon Valdez (http://www.sciencedaily.com/releases/2000/01/000127082228.htm). And probably a lot more than will be discharged by this most recent accident. Mapping natural seepage in the Gulf is one way the oil companies look for oil ( http://www.searchanddiscovery.net/documents/hood/images/hood.pdf ).
Natural oil seeps occur in most oil fields (http://www.npagroup.com/oilandmineral/offshore/oil_exploration/index.htm). One impact of offshore oil development that is not well known is that it can actually reduce the oil released by taking pressure off of the natural reservoirs. This has been very clearly demonstrated in southern California where as a result of the offshore oil production there is less oil on the beach today than there was historically before oil development (http://www.soscalifornia.com/ http://www.sciencedaily.com/releases/2009/05/090513130944.htm http://www.informaworld.com/smpp/content~content=a912055072&db=all). This is less well understood in the Gulf of Mexico where the seeps are much more widely spread and less well understood than in California, but it is unlikely current oil development is adding significantly to the natural seeps and certainly possible they have been reduced.
One interesting fact is that today most of the oil in the sediments of Prince William Sound are from natural sources, not the Valdez spill. This is fairly easy to determine as the natural oil seeps have a different hydrocarbon finger print from the North Slope crude the Valdez released. I do not mean to downplay the mess created by the Valdez, that oil was released suddenly and from a single spot. And the short term impact was significant and a big problem. On the other hand the natural seeps release oil slowly and are disbursed but over the time amount to a lot more than the Valdez.
This time I checked the links and did have a hard time making them all work. Maybe I am trying to put too many into a single post?? I think they do now all work, but some will have to be pasted into the browser rather than clicked on. |
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