A 2-D Numerical Method to Compute the Time- and Space-Dependence Evolution of the Surface Heat Flow by Inversion of Stratigraphic Data (Well Logs or Seismic Profiles): Application to the Prediction of Hydrocabon Generation in the Paris Basin

Le Solleuz, Antoine¹, Cedric Menetrier², Cecile Robin³, Marie-Pierre Doin⁴, Marcel Elie², François Guillocheau³, Luis Martinez² (1) Nancy School of Geology, ENSG-G2R, Vandoeuvre-les-Nancy, France (2) UMR 7566 G2R UHP Nancy I, Vandoeuvre les Nancy, France (3) University of Rennes, Rennes, France (4) Ecole Normale Supérieure, Paris Cedex, France

The maturation of organic matter is essentially controlled in sedimentary basins by the surface heat flow variations and its burial history. The thermal and the mechanical behav­iour of the lithosphere drive these two geological phenomenons. We propose here a 2D­backward method to constrain their evolution with a 2D thermo-mechanical model by inver­sion on stratigraphic data (well-logs or seismic profiles) in order to couple it with a numer­ical model of hydrocarbon generation. The 2D numerical model solves the heat equation in the lithosphere. It is based on a constant mantle heat flow at the bottom lithosphere. It takes into account phase transitions in the lithosphere and thermal- and pressure-dependent ther­mal properties which can induce thermal anomalies. The backward model adjusts thermal subsidence curves (model) with tectonic subsidence curves (from stratigraphic data) by optimization of three geophysical parameters, along stratigraphic profiles: i) extension, ii) Moho depth and iii) mantle heat flow (Le Solleuz & al., 2004). From this minimization, we determinate, along stratigraphic profiles, time-dependent evolutions of the surface heat flow that we inject into a 2D-kinetic model, to simulate the hydrocarbon generation in basins. We apply this integrated approach to the Paris Basin (France). Along correlated well-logs, the 2D numerical model inversed on stratigraphic data gives surface heat flow variations between Permian and the Present day (Ménétrier & al., this congress). Results indicate a strong hydrocarbon generation during Permian followed by a display of the organic matter maturation until Late Mesozoic.