Alan H. Silliman, Paul A. Harrington
A passive soil gas surface geochemical survey was conducted in a frontier basin in Latin America. The survey was conducted in two phases in the early 1990s. Hydrocarbon data in the mass range from C2 to C11 was acquired. The data were analyzed by thermal desorption mass spectrometry. Geochemical interpretation and modeling of this data were performed using principal components analysis. During the first phase, a generic oil model was developed which mapped multiple geochemical anomalies in the basin. Subsequent drilling found that these anomalies were associated with two types of oil, a high gravity oil and a low gravity oil.
During the second phase, the previous survey was expanded. The objective of the second phase was to define areas of high gravity oil influence only. Geochemical models were developed to separate areas of high gravity oil influence from low gravity oil influence. Subsequent drilling on two anomalies confirmed the presence of high gravity oil accumulations.
This project illustrates the ability of passive soil gas geochemistry to distinguish between two different types of oil at depth using geochemical modeling techniques. This project also demonstrates the effectiveness of integrating multiple phases of geochemical sampling in an exploration program.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela