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Results of Surface Geochemistry Survey over the Vernon Field, Isabella County, MI

T. J. Bornhorst1, J. R. Wood1, S. D. Chittick1, W. B. Harrison2, and D. Barnes2
1Michigan Tech. Univ., Houghton, MI
2Western Michigan Univ., Kalamazoo, MI

Four surface geochemical techniques have been tested at the Vernon Field in support of a demonstration project partially sponsored by the U.S. Department of Energy to detect and recover bypassed oil. The techniques included surface iodine, enzyme leach, microbial and soil gas. The most extensive sampling (350+ samples) was for the microbial oil survey technique in which microorganisms are cultured from soil taken 20 cm beneath the surface. Results from a smaller number of iodine samples (collected from soil within an inch of the surface), headspace soil gases (collected from 1 meter beneath the surface) and selectively extracted trace elements (from the top of the B-horizon) and soil gas hydrocarbons (extracted from soil of the top of the B-horizon) will be presented as well.

The detection of subsurface accumulation of oil and/or gas by surface geochemical techniques is based on microseepage of reservoired hydrocarbons to the surface and has been used elsewhere in combination with other data to reduce drilling risk. Except for the enzyme leach techniques, the surface geochemical signal recorded is transient (i.e. not cummulative) and will respond to changes in the reservoir. Only transient techniques are useful to detect by-passed oil. The microbial anomaly was apical while the others are best interpreted as edge anomalies or halos around the target.

The initial collection of geochemical samples was completed during the summer of 2000 and sampling will be continued during the summer of 2001. The challenge with all of the surface geochemical techniques is definition of anomalies and their interpretation. The cause of the surface geochemical anomaly can be from a variety of depths beneath the surface. The initial results demonstrate that hydrocarbon microseepage from the Dundee reservoir is detectable by surface soil geochemical techniques.

AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan