--> Allochthonous Salt Sheet Growth: Implications for Thermal History and Source Rock Maturation in the Burgos and Perdido Basins, Mexico
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Allochthonous Salt Sheet Growth: Implications for Thermal History and Source Rock Previous HitMaturationNext Hit in the Burgos and Perdido Basins, Mexico



Allochthonous salt sheets cover large portions of the Burgos and Perdido basins in Mexico. Salt extrusion began in Eocene times with extensive run out, probably triggered by the Laramide orogenic compression. Rapid sedimentation in the Oligocene/Miocene dammed the salt sheets at the seaward edge. However, salt continued to advance in periodic surges and thickened up to 4 km at the landward side of the sheet. The basin fill was folded and uplifted and eroded in the Oligocene to Miocene period, which created attractive truncation and anticlinal traps in the sub-salt strata.

Tithonian age source rocks are currently buried to depths of 8-12 km (below seabed) underneath the allochthonous salt sheets. Despite this deep burial, thermal modelling (using Zetaware 1 D Genesis software) suggests that the thick shallow-buried salt sheets retard source rock Previous HitmaturationTop and some of the anticlines have access to source rocks which are still in the oil window. Peak oil generation is predicted to have been reached in the Eocene at the thick rear end of the salt sheets, but there was nowhere for the oil to escape into the shallower section until the Oligocene age folding occurred. Continued folding in the Early Miocene may have caused breaching of earlier folded traps at Wilcox (Eocene) reservoir level. However, our model results indicate there was a second peak of oil generation in the late Miocene caused by thermal recovery after increased burial below the frontal edge of the allochthonous salt sheets. This should have refilled any previously-emptied sub-salt fold structures. We will discuss these results in relation to the hydrocarbon prospectivity of the deepwater blocks currently on offer in the CNH Deepwater Round 2016.