4D Regional Evolution of Gravity Driven Systems: Comparison between Salt and Shale Tectonics and Petroleum Implications

Philippe de Clarens¹, Xavier du Bernard², Jean-Loup Montenat², and Stephane Raillard^2
1 Total, Paris La Defense, France
² Total, Pau, France

The 4D deformation propagation triggered by gravity driven processes, gravity spreading and/or gliding, above Shale or Salt decollement levels shows clear differences controlled by:

• decollement levels efficiency
• sedimentary overload distribution through times
• basement geometry changes linked with tectonic events.

2D regional cross sections and maps restorations on several basins located on the West African margin, are used in order to characterise:

• geometrical and kinematics differences between shale and salt gravity driven systems
• petroleum implications.

Main results show forward deformation propagation for Shale gravity driven systems implying central area of structural inversion, from compression to extension deformation. On the contrary a general backward deformation evolution is evidenced for salt gravity driven systems triggering central area structural inversion, from extension to compression.

As a consequence, deep buried paleo-thrust and fold belts are likely to be exploration targets within the central part of any Shale gravity driven systems. Backward compression propagation in Salt Gravity driven systems allows thick early basin poorly deformed to be involved into large folds and thrust.