Thermal Transfer and Pressure Regime Across a Rifted Margin in the Presence of Evaporites, with Consequences for the Hydrocarbon Potential: A Modeling Approach in the Provencal Basin

Jean Burrus, F. Audebert

Modeling the hydrocarbon potential of a sedimentary basin requires one to at least reconstruct the burial, the thermal history, and the pressure regime in the sediments. This is complicated, in the case of the western Mediterranean basins, by two problems: (1) Reconstruction of the temperature history is dependent on the rifted nature of these basins and on the particular distribution of thermal gradients linked with the presence of the high-conductivity evaporitic layers deposited in the late Miocene. (2) Reconstruction of pore pressure must account for the high sedimentation rate generally observed in the Pliocene-Quaternary and the presence of hydraulic barriers which correspond to the evaporitic layers. The negligible permeability of these rocks created a significant ndercompaction of the sediments underneath, associated with high excess pressures.

We present the result of a modeling study of these effects using a 2-D code (Themis) developed at IFP. The model describes simultaneously the geodynamic evolution of the margin during and after rifting and the phenomena of heat redistribution and abnormal compaction in the sediments. This is applied to the evolution of the Gulf of Lions margin (Provencal basin, northwestern Mediterranean). The effects of these processes for the level of maturation of organic matter and pattern of migration are discussed.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.