Organofacies heterogeneity of the Aptian–Albian source rock (Kazhdumi Formation) in selected oilfields from the Zagros Basin

Organic geochemical data for the Aptian–Albian Kazhdumi Formation of SW Iran were reviewed to better understand its organic geochemical characteristics. Rock-Eval pyrolysis data from ۳۸۲ samples, sourced from both published literature and proprietary data, were used in this study. Prior to interpreting the geochemical data, a robust screening procedure was applied to eliminate anomalous values. The refined dataset, consisting of ۱۳۵ samples from ۲۲ different oilfields, was subsequently used to evaluate the variation of Kazhdumi source rock organofacies in a regional context. Our results indicate that different stratigraphic horizons within the Kazhdumi Formation are represented by different organofacies characteristics. This organofacies heterogeneity was most likely controlled by the palaeo-depositional environments in which strongly anoxic conditions (e.g., during times of relative sea-level high) were intervened by suboxic conditions (e.g., at times of sea-level fall) during Kazhdumi deposition. This organofacies heterogeneity is an important risk factor for containing the Kazhdumi-Ilam/Sarvak petroleum system of the Zagros Basin, as it controls the ultimate generative capacity and expulsion characteristics of the Kazhdumi source rock. In addition, the results of this study further emphasize the importance of considering source rock effective thickness in future basin and petroleum system modeling studies.

Organofacies heterogeneity of the Aptian–Albian source rock (Kazhdumi Formation) in selected oilfields from the Zagros Basin Keywords:

Kazhdumi Formation , Source rock evaluation , Organofacies variation , Palaeo-environments , Dezful embayment