Surficial geochemical case history 1: structural traps

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Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Predicting the occurrence of oil and gas traps
Chapter Surface geochemical exploration for petroleum
Author Dietmar Schumacher
Link Web page
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Meyer et al.[1] published an excellent but little-known case history documenting vertical migration and microseepage from undisturbed structural traps. In the early 1980s, a series of microseepage surveys were conducted over 49 proposed well locations in Kansas and Colorado.

Sampling[edit]

Soil samples were collected at one-tenth-mile intervals within one-half mile of each proposed drilling site and analyzed for the presence of hydrocarbon-oxidizing microbes. All samples were collected and analyzed prior to drilling, and the results were placed in escrow until after the wells were drilled.

Survey vs. drilling results[edit]

Figure 1 Ten representative seismic prospects surveyed and later drilled. Based on Meyer et al.[1] Copyright: Barringer Technologies Inc.

When compared with the subsequent drilling results, the soils overlying productive reservoirs contained microbial populations that were readily distinguishable from those of samples that were collected from nonproductive sites. The 39 wells subsequently drilled yielded three producers, three wells with uncommercial shows, and 33 dry holes. The microbial survey correctly predicted all 33 dry holes and identified the three producing wells and two of the three wells with uncommercial shows. The one show well that was not recognized tested 9 BO/D with a very low gas-oil ratio (GOR).

Figure 1 illustrates ten representative seismic prospects surveyed and later drilled. Each prospect displays good four-way dip closure on a Cretaceous horizon, and each is located in a productive basin. Only one was associated with a surface geochemical anomaly; it was the only one of the ten shown that resulted in a commercial discovery.

See also[edit]

References[edit]

  1. ↑ 1.0 1.1 Meyer, W., T., Lovell, J., S., Hale, M., 1983, Detection of concealed mineral and energy resources by vapor geochemistry, in Thornton, I., Howarth, R. J., eds., Applied Geochemistry in the 1980s: London, Graham and Trotman, p. 86–102.

External links[edit]

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gas-oil ratio

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