Abstract: Source Identification of Beach Tars within Southern California Borderland

Thomas J. O'Neil

Determination of stable and unique properties of crude oil are important for reservoir identification and pollution studies. In this study, the high-molecular-weight-asphaltene fraction of crude oil was evaluated as a tracer for beach tars. Crude oils were collected from 12 natural seeps and 28 producing wells within the southern California borderland. Beach tars were collected routinely over a 14-month period from 120 mi (192 km) of the adjacent coastline. Asphaltenes were isolated and analyzed for trace elements by atomic-absorption and neutron-activation analysis, for molecular-size distribution by gel-permeation chromatography for sulfur by X-ray fluorescence and for nitrogen by Kjeldahl. The most unique characteristics of the asphaltenes, trace element concentrations and molecular-size distributions enable tracing of the crude oil from natural seeps to beach tars. Simulated marine-weathering experiments show the asphaltene component to be stable for a period of four months.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA