Thermal Maturity, Organic Petrography, Bulk and Compositional Kinetic of Hydrocarbon Generation in Cretaceous-Paleogene Source Rocks from Western Dezful Embayment, SW Iran

Abstract

In this study, in order to know the effective petroleum system in charging reservoirs in oilfields located in the west of Dezful Embayment, the cutting shales from Pabdeh, Kazhdumi, and Garau formations (Cretaceous-Paleogene Source Rocks) were selected for Rock-Eval Pyrolysis, Organic Petrography, Bulk, and Compositional kinetic. Furthermore, the Pabdeh shale samples are described as a mixture of kerogen types II and III with lower thermal maturity. The Kazhdumi shale samples show Type III and Type II/III kerogens and fall within the oil window zone. In addition, the Garau shale samples are determined to have Type III and Type II/III kerogens with high thermal maturity in the zone of the oil window. The bulk and compositional kinetic parameters reveal that the organic facies of the Kazhdumi and Garau formations indicate thermally mature kerogens able to generate and expel mature oils, but the Pabdeh Formation does not have enough maturity for oil generation. The composition kinetic model demonstrates that the Pabdeh and Kazhdumi formations are very similar in pyrolysate composition to the Garau Formation (due to the high sulfur in the kerogen of the Garau Formation). Finally, the Garau Formation is the main source rock, and the Kazhdumi Formation is the second one for filling hydrocarbon reservoirs in the studied area.