Chapter from: M 66:  Hydrocarbon Migration And Its Near-Surface Expression
Edited By 
Dietmar Schumacher and Michael A. Abrams

Authors:
Ronert W. Potter II, Paul A. Harrington, Alan H. Sulliman, and James H. Viellenave

Geochemistry, Generation, Migration

Published 1996 as part of Memoir 66
Copyright © 1996 The American Association of Petroleum Geologists.  All Rights Reserved.
 

An independent evaluation of alternate technologies for petroleum exploration undertaken by Santa Fe Minerals selected the PETREX soil gas geochemical method. A subsequent exploration program involving 139 geochemical surveys led to drilling 141 wells in previously undrilled prospects. A total of 43 wells were drilled in negative geochemical anomalies and 41 of these encountered no hydrocarbons. A total of 98 wells were drilled in positive geochemical anomalies and 37 were commercial successes. The geochemical success rate was even higher, accurately predicting the presence of hydrocarbons 92% of the time. Surface soil gas hydrocarbon signatures were shown to be very similar to those of volatile gases from producing hydrocarbons in four new wells ranging in depth from 2000 to 15,000 ft. This evidence supports the vertical migration of reservoir hydrocarbons. Geochemical anomalies are apical and lateral shifts of anomalies are rare. A general trend of increasing anomaly strength with increasing porosity times reservoir thickness has been observed. The integration of seismic data and PETREX geochemical data results in prospect evaluation that is better than that available using either method alone.