A regional microseep survey of a 1280 mi² area of the Wyoming-Utah thrust belt clearly identified anomalously high surface occurrences of light hydrocarbons associated with productive trends that include the Clear Creek, Ryckman Creek, and Whitney Canyon-Carter Creek fields. The ethane-to-propane ratios of these anomalies are very similar to those of the hydrocarbons produced from the associated fields.

Anomalies were identified by individually calculating, for each light hydrocarbon, the percentage of samples within a moving window which were above the median value of the entire survey, and by stacking them to create a composite map. This technique smoothes the spatial information and transforms the data from an unknown distribution into a binomial distribution. This permits statistical tests of significance, which have been substantiated with Monte Carlo simulations. The anomalies are both stronger and spatially more extensive than would be expected on a random basis.

The use of regional microseep data emphasizes the identification of broad areas of interest, rather than the direct identification of drilling locations often associated with surface geochemical surveys. The resulting broad surface patterns must then be combined with available subsurface data to develop probable plays. This technique is one of the few tools that analyze directly for hydrocarbons. It provides the explorationist with unique information to help reduce economic and geologic risk in frontier areas.