Thermal reconstruction in extension tectonics: coupling geodynamic modelling with petroleum system modelling, the South Atlantic conjugate margins as a case study

Author(s):	A. Beniest	,
	Evgenii Burov
	Sierd Cloetingh
	W. Sassi
	X. Guichet

Deep offshore oil exploration deals with petroleum systems situated in basins with a syn-rift and sag- basin history. The hydrocarbon potential of such a setting is still very uncertain, due to risks concerning too early maturation and subsequent hydrocarbon leakage. Progress in the field of geodynamics can be used to better predict the maturation history and petroleum system development. The thermal evolution of the South-Atlantic sedimentary basins has been studied with the use of a thermo-mechanical model that covers a time span of 100 Ma. The basins formed under pulsed extension during the Early Cretaceous. Absolute extensional velocities are determined from plate reconstruction software. Moho-temperature evolution over time, retrieved from the thermo-mechanical model, are implemented in a petroleum system modelling software. The Orange basin (offshore Namibia) and its conjugate the Colorado basin (offshore Argentina) are used as reference basins to investigate the effect of lithosphere scale processes on the source rock maturation of conjugate basins. Coupled phenomena between large-scale asthenospheric ascent, lateral flow of ductile materials in the lower crust and brittle structure of the upper crust are at the base of the thermal evolution. The thermal evolution of the basins resulting from crustal stretching, syn-rifting and continental break-up happen very fast in only few ten millions of years. With this study we suggest that fast, large-scale thermal processes have a yet to be quantified influence on the thermal evolution of sedimentary basins in the South Atlantic.