Early in the history of geochemical prospecting, it was recognized that more intense soil-hydrocarbon anomalies occur in the near-surface soil over newly discovered petroleum accumulations than over those that are depleted or nearing depletion. The first convincing confirmation of this effect was obtained in 1968 after resurveying the Hastings oil field, Brazoria County, Texas, which previously was sampled in 1946. The outstanding soil hydrocarbon anomaly of the earlier survey did not reappear in the 1968 study.

Surveys conducted in 1970-71 over new and old oil and gas producing areas in Jackson County, Texas, furnished additional support to the thesis that removal of hydrocarbons from subsurface reservoirs affects near-surface soil hydrocarbon anomalies.

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