--> Abstract: Successful Surface Geochemical Surveys: Seven Pitfalls to Avoid, by Dietmar Schumacher; #90078 (2008)

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Successful Surface Geochemical Surveys: Seven Pitfalls to Avoid

Dietmar Schumacher
Terralliance, Newport Beach, CA

It has been long known that most oil and gas accumulations leak hydrocarbons, that this leakage is predominantly vertical, and that it can be reliably detected and mapped with various direct and indirect geochemical and non-seismic geophysical methods. It has also been documented that the areal extent of the surface geochemical anomaly can approximate the productive limits of the reservoir(s) at depth. How reliably this can be done depends on the geologic setting, the choice of analytical method, survey design, and sample spacing.

How can we improve the probability of success for our surface geochemical surveys? A review of several hundred geochemical surveys identifies seven major pitfalls that contribute to survey failures or interpretation ambiguity. These surveys were conducted in geologically and environmentally diverse settings, and used a variety of survey and analytical methods. The seven pitfalls to avoid are:
1. Too Few Samples
2. Improper Survey Design
3. Wrong Method for Survey Objectives or Survey Terrain
4. Poor Data Quality
5. Interpretation Errors
6. Absence of Good Analogs
7. Data Integration Poor or Incomplete

For a successful surface geochemical survey one must select the right survey method, use the proper survey design, calibrate with a good geologic analog or recent discovery, and fully integrate surface and subsurface data. Although the discovery of a surface geochemical anomaly does not guarantee the discovery of commercially significant volumes of hydrocarbons, it has been well documented that prospects associated with such seepage anomalies are 4-6 times more likely to result in a commercial discovery than similar prospects lacking such anomalies. This presentation will be illustrated with examples from US and International surveys.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas