Using the least accurate of temperature data types, temperature anomalies, "hot spots" believed to be hydrocarbon anomalies have been defined by application of a new analytical technique. To date, the technique has been successful to a significant degree when applied to known fields using only dry hole data and, in some places, only dry hole data for wells drilled prior to field discovery as initial steps toward before-the-fact analysis. Technique testing by the drill remains undone.

The theory accepted herein is that heat flows from the earth's hot interior toward its colder surface in nature's attempt to establish temperature equilibrium. Three facts are accepted: (1) hydrocarbon fluids have very low thermal conductivities (oil about one-fifth that of water and gas about one-fourteenth that of water); (2) equal heat input elevates the temperature of a largely hydrocarbon fluid volume relative to a laterally equivalent volume of largely water-filled porosity; and (3) there are fewer grams of hydrocarbon fluids to warm than water filling an essentially equal porosity volume.

Hydrocarbon fluids insulate more (fact 1) and their temperatures are elevated more easily (facts 2 and 3) than contiguous waters. Hydrocarbon reservoirs whose heat flow effects are not obscured by the anisotropic effects of adjacent water reservoirs, should be potentially definable temperature anomalies.

The technique formulated involves the following steps: (1) calculation of geothermal gradient values; (2) creation of a geothermal gradient field areally; (3) vector analysis or contouring of created data; and (4) anomaly definition. Technique application to ten fields representative of a range of complexities shows promise for this up-the-odds exploration tool. Results for three examples (Black Lake field, Louisiana; Haverhill field, Kansas; and Salt Creek field, Texas) may demonstrate principal use as a grading method for prospects based initially on classical study.

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