A method of determining terrestrial heat flow in oil fields from bottom‐hole temperatures, electric logs, and thermal conductivity of core samples has been tried in six Reco⁁ncavo Basin oil fields in Brazil. The average heat‐flow value so determined for the Reco⁁ncavo Basin is [Formula: see text]. The technique can be used for calculating heat flow in continental areas elsewhere. A more significant outcome of our experiment is that it demonstrates an inexpensive method of obtaining terrestrial heat‐flow values in the sedimentary basins of the world.