Adsorbed, free, and headspace soil-gas samples collected from the Patrick Draw field, Wyoming, were analyzed by routine geochemical techniques. Gas chromatography was used to determine the light-hydrocarbon (C1 to C7 paraffins) concentrations in the samples. Anomalous hydrocarbon concentrations appear in those areas near lineaments mapped from Landsat images of the Patrick Draw field. These lineaments represent extensional faults and fractures produced during development of the Rock Springs uplift to the west. Because several of these mapped lineaments extend to depth, they are able to serve as conduits allowing the preferential microseepage of hydrocarbons to the surface from the reservoir rock. These effusive soil gases, in the Patrick Draw area, indicate the nature of the expected hydrocarbons at depth. Further, by targeting easily observable, pervasive lineaments, studies of this nature might be useful as a fast and economical means to screen out or high-grade areas of potential hydrocarbon plays. This approach should prove particularly helpful in frontier areas where predictive information would be valuable.

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