Physical simulation of hydrocarbon migration and accumulation in transport systems of allochthonous salt sheet development zone: a case study of Perdido Fold Belt in Burgos Basin, Gulf of Mexico

The Burgos Basin is a typical salt passive continental margin basin in the western Gulf of Mexico, rich in oil and gas resources. The allochthonous salt sheet development zone in the Perdido Fold Belt of the Burgos Basin has formed an oil and gas transport system comprising the underlying structures of allochthonous salt sheets, faults, and the Paleocene to Eocene Wilcox Formation. Due to the deep-water environment and complex salt tectonics, the hydrocarbon transport characteristics and efficiency in these allochthonous salt sheet development zones remain unclear. Therefore, to reduce exploration risks, it is important to quantitatively evaluate the transport efficiency of hydrocarbon transport systems in the allochthonous salt sheet development zone of the Perdido Fold Belt and to clarify transport efficiency differences among various types of transport systems and their influencing factors. Based on seismic, well drilling, and well logging data, the hydrocarbon migration and accumulation physical simulation experiments were carried out on three types of transport systems—downdip, wavy, and updip-developed in the allochthonous salt sheet zone of the Perdido Fold Belt. The results showed that compared to the sand and mudstone at the base of the salt sheets, the Wilcox Formation exhibited higher transport efficiency in all three transport systems, serving as the primary channel for hydrocarbon migration. The transport efficiency varied during different migration periods. Specifically, the downdip system demonstrated the highest transport efficiency at the end of the Eocene, and the updip system had the highest efficiency at the end of Oligocene. During these two periods, the study area experienced strong fault activities, facilitating hydrocarbon migration. The hydrocarbon transport efficiency in the allochthonous salt sheet development zone of the Perdido Fold Belt was affected by factors such as the physical properties of transport systems, hydrocarbon migration distance, and the pressure difference between source rock and reservoir. Among these, the pressure difference is the main controlling factor, followed by the migration distance, with the physical properties of transport systems having a relatively minor effect.