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studies, data analysis, synthesis of historical records, and careful searches for existing 

 scientific literature. Our work has been funded through the peer-review process and 

 results fi"om our research will be published in the peer-reviewed literature. 



The preliminary findings of this work indicate that there has been a reduction in 

 natural hydrocarbon seepage over the past twenty years near an oflfshore oil platform in 

 the Santa Barbara Channel. This reduction has occurred during a time of oil production at 

 the platform and we hypothesize that this production has lowered natural seepage rates. 

 We are working to verify this hypothesis and to accurately quantify changes that have 

 occurred. We are also working to understand the implications of our findings. To the best 

 of our knowledge, this is the most detailed study to ever examine a change in seepage over 

 time in the marine environment. 



I will continue my presentation by showing you some of the evidence that a 

 reduction in hydrocarbon seepage has occurred. I will end by elaborating on the possible 

 consequences and significance of this finding. 



The Santa Barbara Channel is an area of intense natural hydrocarbon seepage 

 (Wilson et al., 1974 and Allen et al., 1970). As far as we are aware, the only area of 

 greater natural marine seepage in the world is in the Caspian Sea in the former Soviet 

 Union. The abundant tar found on southern California beaches is due to this natural 

 seepage. All of the tar on Santa Barbara's beaches and half of the tar on Los Angeles 

 beaches comes fi-om the natural seeps offshore fi-om Coal Oil Point (Hartmond and 

 Hammond, 1981), near the UCSB campus. The volatile hydrocarbons fi"om these seeps 

 are also a significant source of air pollution in Santa Barbara and Ventura Counties (Killus 

 and Moore, 1991). The smell of hydrocarbon compounds fi^om the natural seeps is often 

 present on the UCSB campus. 



Our research group has been studying these seeps in order to quantify the total 

 amount of hydrocarbon emissions and to determine if there has been any change in 

 emissions due to offshore oil production. Each oil field in the Santa Barbara Channel has 

 some associated natural hydrocarbon seepage. This figure (#1) shows the oil fields in the 

 Santa Barbara Channel. We have focused our initial efforts on the seeps above the South 

 EUwood Offshore Field, because the seeps are extremely intense at this location. There is 

 also an offshore platform that has been producing oil fi"om a portion of the natural seep 

 field since 1967. The seepage is coming fi-om oil in the Monterey Formation, which has 

 been produced fi-om Platform Holly since 1972. 



This figure (#2) shows a map of the seep activity on the South EUwood Field in 

 1994 that was measured with a sonar survey. The total gas seepage fi-om this field is about 

 5 million cubic feet per day. In addition, about 6 thousand gallons of oil is naturally 

 seeping into the ocean every day. About 8% of the gas seepage is being captured by seep 

 containment devices ("seep tents") that were placed on the seafioor one mile east of 

 Platform Holly in 1982. The surprising result of this survey is how little seepage was 

 occurring within one mile of Platform Holly in 1994 and 1995. The area around Platform 



