Evaluation of the Heat Flow in the Southern Alps during Mesozoic Extension: Implications for Hydrocarbon Exploration in the Po Plain Foredeep
Paolo Scotti, Roberto Fantoni, 2012. "Evaluation of the Heat Flow in the Southern Alps during Mesozoic Extension: Implications for Hydrocarbon Exploration in the Po Plain Foredeep", Analyzing the Thermal History of Sedimentary Basins: Methods and Case Studies, Nicholas B. Harris, Kenneth E. Peters
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We reconstructed the thermal history, and therefore the evolution of heat flow in the southern Alps region (northern Italy), using organic matter (OM) maturity data obtained from samples of sedimentary units outcropping along the entire mountain chain. Regional OM maturity patterns are largely controlled by a high geothermal gradient and differential burial during the Norian–Liassic extensional phase. Good results for thermal history calibrations from several locations were obtained using a large database of measured OM maturity, consisting of different maturity parameters, often all in agreement, for a wide range of lithostratigraphic sequences.
One-dimensional thermal modeling was applied to selected successions that were not overprinted by alpine evolution. Resulting heat-flow values were high and relatively uniform (85 to 105 mW/m2) throughout the southern Alps during the Lias–Early Dogger, and they progressively decreased after the Bajocian–Bathonian to values similar to the present-day heat flow (50 to 55 mW/m2) by the end of the Cretaceous. This heat-flow reconstruction is consistent with the known tectonic evolution of Mesozoic extension in the southern Alps, characterized by a rifting stage lasting to the Lias, followed by a drifting stage beginning in the Middle Jurassic.
Elevated heat flow in the southern Alps has important implications for hydrocarbon exploration. Upper Triassic source rocks in basinal successions attained high maturity during the Jurassic, and this is even more likely for the deeper Middle Triassic source rocks.
Improved definition of the heat-flow peak in the Jurassic helps to define the hydrocarbon charge risk associated with leads and prospects in the Po Plain subsurface, where traps formed in the Cenozoic. In areas characterized by little Rhaetian–Liassic burial, the source rocks retained their original petroleum potential prior to strong Neogene–Quaternary burial and heating.
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Thermal histories of sedimentary basins are critical sources of scientific and practical information. They provide us with windows into past and present tectonic processes and the configuration of the crust and mantle. Using records of present and past temperature distributions, we can identify and constrain interpretations of tectonic events, distinguish different basin types and interpret pathways of fluid flow. These insights can be used calibrate basin and petroleum system models and to interpret and predict the distribution of minerals and petroleum, diagenesis and reservoir quality, and the geomechanical properties of rock units. This volume summarizes the current state of the art for many modern approaches used to estimate paleotemperature. Many techniques are now available based on both organic and inorganic components in the rock. Even techniques that are now many years old, such as apatite fission track analysis, have und