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Abstract: The Role Previous HitOilNext Hit and Previous HitGasNext Hit Seeps Played in Petroleum Exploration in California

MAGOON, LESLIE, U.S. Geological Survey, Menlo Park, CA; SUSAN HODGSON, California Division of Previous HitOilNext Hit, Previous HitGasNext Hit, and Geothermal Resources, Sacramento, CA

Fifty (16%) of the 315 Previous HitoilNext Hit fields and two (1%) of the 176 Previous HitgasNext Hit fields in California have been discovered because of nearby seeps. However, there are almost twice as many Previous HitoilNext Hit fields as Previous HitgasNext Hit fields in the state. Comparing these numbers with 482 Previous HitoilNext Hit and 97 Previous HitgasNext Hit seeps reported in California, we see that there are five times more Previous HitoilNext Hit than Previous HitgasNext Hit seeps; and clearly, because Previous HitoilNext Hit seeps are easier to find than Previous HitgasNext Hit seeps, they are a more useful tool for petroleum exploration. The Wheeler, Trask and Coleman Tunnel dug near seeps in 1861 resulted in the first California Previous HitoilNext Hit discovery---Santa Paula field in Ventura County. The most recent field discovered near seeps is Livermore field, discovered in 1967 by McCulloch Previous HitOilNext Hit near the town of Livermore in Alameda County. Only two Previous HitgasNext Hit fields, La Goleta (1932) and Sutter Buttes (1933) were found because of nearby Previous HitgasNext Hit seeps.

The difficulty of attributing a single geologic parameter, such as petroleum seeps, to the discovery of a field is an over-simplification considering that most explorationists employ more than one line of evidence before drilling a wildcat well. For example, surface geology in California frequently reveals anticlinal features or topography indicating four-way closure at depth. However, whenever Previous HitoilNext Hit and Previous HitgasNext Hit seeps are present in the area of interest, tangible evidence exists that petroleum has been generated in sufficient quantity to migrate to the surface. Also, for small companies or individuals closely watching exploration expenditures, the presence of seeps is tangible evidence to investors that Previous HitoilNext Hit is nearby, thereby facilitating funding. Several exploration case histories will be examined where seeps played a dominant role in field discoveries.

 

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California