3D petroleum system modeling, Salina del Istmo: A regional approach in a geologically complex área.
'Petroleum system modeling in the Gulf of Mexico has been performed in diverse ways by many scientists. A combination of high structural complexity, salt tectonics, and variable stress-field changes makes the Gulf of Mexico a difficult setting to evaluate petroleum system evolution. Based on previous studies of the tectonostratigraphic evolution, regional structural restorations, and 2D petroleum system modeling, a new regional 3D petroleum system model was built for the Salina del Istmo Basin in the southern Gulf of Mexico. The structural framework for the model was obtained using a salt-piercing methodology in commercial petroleum systems modeling software, where the originally deposited sedimentary facies are later replaced by salt at different geologic times. Overall, the Tithonian source rock maturity in the area increases towards the west (varying from immature to gas-prone). Two salt movement alternative scenarios, namely allochthonous salt emplacement at 23 Ma and 11.6 Ma are presented. The younger emplacement is characterized by higher present-day maturity, mainly in areas with more allochthonous salt presence. Due to inherent uncertainties in seismic velocities used for depth imaging, as well as in the seismic interpretation calibration, a depth window of 1000 m for the Tithonian source rock was also considered as sensitivity analysis for maturity. We included several reservoir rocks at different stratigraphic levels that are offset by steeply dipping faults in some areas in the model. The 3D migration model analysis suggests charge at different reservoir levels, which is influenced by fault properties and timing in some areas. Using 3D petroleum system modeling provides a relatively fast and efficient way to predict source rock maturity, expected fluid type, and other salient characteristics of the petroleum system in this structurally very complex, salt-dominated frontier basin.