--> Salt Tectonics and Exploration Potential of the Deepwater Cuenca del Sur (Campeche) Salt Basin, Mexico

AAPG/SEG International Conference & Exhibition

Datapages, Inc.Print this page

Salt Tectonics and Exploration Potential of the Deepwater Cuenca del Sur (Campeche) Salt Basin, Mexico

Abstract

Abstract

This talk will review the geological history of the basin and summarise the prospectivity, especially where 6 very large blocks are currently on offer in the CNH Ronda Uno.

The deepwater Cuenca del Sur Basin is the least explored deepwater giant salt basin in the world; with only a handful of wells drilled in water depths greater than 1000 m. Diapirs initiated during Jurassic crustal extension, and continued to grow downbuilding due to sediment loading, thoughout the Cretaceous to Paleocene period. The Laramide Orogeny (Paleogene) produced NE-directed compression of salt diapirs and limited extrusion of salt sheets in the Eocene. This was followed by another compressive event in the Mid-Miocene which was associated with the development of the Nazca-Cocos spreading ridge (around 22-23 Ma). This led to rapid squeezing of salt and rapid extrusion of extensive allochthonous salt sheets, which reach up to 4 km in thickness. Contraction continued after salt extrusion and sediment burial, and the salt sheets were folded with variable fold axis orientations conditioned by the pre-existing salt bodies. The folding was disharmonic so that base and top allochthonous salt structures are very different. Potential Early Miocene to Eocene age sandstones are believed to be present in structural traps below the salt sheets, but poor sub-salt seismic imaging has hindered exploration.

The Miocene shortening produced folding and thrusting at the Mesozoic level, and large overthrusted Cretaceous carbonate sheets ramp up from depths of 8-10 km to near seabed. Salt was dragged up along the thrusts and then extruded at the seabed to produce characteristic bird's head structures. The location and vergence of overthrusting is probably determined by pre-existing asymmetric extensional salt rollers. Intense deformation of the thrusted carbonates at or near the seabed, coupled with leaching, may have enhanced the reservoir porosity.

Turbidite sandstone plays are important in the southern part of the Cuenca del Sur basin, where sand ponded in salt mini-basins during the Miocene. These sandstones were probably derived from the uplifted Chiapas massif. However, in the northern part of the salt basin there was no obvious local siliclastic sources as the Yucatan peninsula was covered by carbonates. Hence, the main reservoir target is expected to be Mesozoic carbonates, and the Eocene age carbonate breccias generated by massive landslips immediately after the Chicxulub meteorite impact.