The quick recipe for a soup of black gold.

The quick recipe for a soup of black gold

In the standard geologic recipe for crude oil, buried organic molecules must simmer for millions of years before they transform into raw petroleum. But oceanographers have found spots on the seafloor that circumvent such a long cooking time. Near superhot vents, organic sediments turn into petroleum-like oil in less than 5,000 years, two researchers report.

"This is the youngest oil we know of on the Earth," says BErnd R.T. Simoneit of Oregon State University in Corvallis. He and Borys M. Didyk of the Chilean national petroleum refinery in Concon suggest this fast oil-formation process may have generated commercially important reserves that remain undiscovered.

Simoneit and his colleagues first discovered oil seeping out of the seaflor in the early 1980s while exploring the Guaymas Basin in the Gulf of California. Seafloor spreading in the region is slowly opening the gulf, generating volcanic activity that heats the crust and causes hot fluids to spew out of ocean-bottom chimneys. Investigators have found similar oil seeps near Antarctica, off the coast of California and elsewhere.

During dives in the submersible Alvin, Simoneit's group removed vent chimneys from the Guaymas Basin for analysis. Chemical studies revealed that oil in the chimneys contains hydrocarbons closely resembling those in petroleum. Now, carbon-14 dating indicates the oil is extremely young, Simoneit and Didyk report in the Nov. 2 NATURE.

From laboratory experiments, scientists know that oil forms fastest when buried organic molecules cook at h igh temperatures. Didyk and Simoneit suggest the Guaymas oil develops so quickly because hydrothermal-vent fluids percolate up through a thick blanket of sediments and alter the buried organic molecules. These fluids can reach temperatures of 350[degrees]C.

After the oil forms in the Guaymas Basin sediments, it migrates up to the seafloor and then into the water. Scientists on Alvin reported seeing suspended globules of oil as large as dimes.

Yet there may exist some locations where young oil does not escape, Didyk and Simoneit suggest. If a thick layer of sediments trapped the oil, this fast production process might create a significant reservoir, either on land or under the ocean floor.

Conventional theories hold that oil reservoirs form only in quiet, stable basins where sediments can accumulate over millions of years. But Didyk and Simoneit propose that reservoirs may develop in areas where thermal activity has heated sediments and formed oil over thousands of years.

Richard Millerer, a geochemist with the Department of Energy in Washington, D.C., agrees that such reservoirs may exist. "I'm not optimistic that's the case, though," he says. Millerer and others contend it would be difficult to find structures that would trap migrating oil in a geologically active region.