Shallow Geothermal Anomalies Overlying Deeper Oil and Gas Deposits in Rocky Mountain Region

Abstract

Eight of nine Rocky Mountain area oil and gas fields surveyed by shallow geothermic methods show hot spots or positive shallow temperature anomalies at depths ranging from 500 ft (150 m) to as shallow as 10 ft (3 m). The magnitudes of these anomalies generally range from 1 to 3F° (0.5 to 1.5C°), but in one case reached 16F° (8.9C°) at 500 ft (150 m). Similar shallow thermal anomalies associated with oil or gas fields are reported in Russian and other literature. The methodology of drilling shallow holes and recording accurate temperatures therein is fairly simple, inexpensive, and rapid. The primary cause of the observed temperature anomalies at and above oil and gas fields is unknown, but the writers believe that lateral and upward fluid movements through subsurface rocks are an important contributing factor. Because four of the fields that show both shallow and deep positive temperature anomalies are stratigraphically controlled and are not on or near crests of structural features, the commonly held belief that positive temperature anomalies over oil and gas fields simply reflect structural highs is not supported by our data. The addition of shallow geothermal surveys to the suite of conventional exploratory methods should improve exploratory efforts to find new oil and gas fields.