Determination of Paleoheat Flux from Vitrinite Reflectance Data

A method is presented for determining paleoheat flux from the reflectance of vitrinite collected from wells. The maturation of vitrinite is modeled using a time-temperature integral that assumes pseudo-first-order kinetics. In testing the numerical algorithm, it was necessary to introduce a “critical temperature” of 295° K, below which vitrinite does not mature; this result is consistent with the latest findings of independent researchers. The degree of consistency obtained from a number of wells is not perfect; much of the inconsistency can be attributed to large uncertainties in the vitrinite reflectance readings. To test the method, heat-flow history was determined for the North Sea basin and the National Petroleum Reserve of Alaska. Quantitative results were obtained detailing the increase and/or decrease of heat flux with time, and were consistent with the qualitative behavior inferred for paleoheat flow from current geologic models.