Hydrocarbon source rocks in Kazhdumi and Pabdeh formations—a quick outlook in Gachsaran oilfield, SW Iran

Majid Safaei-Farouji,Mohammad Hail Hakimi,Mohammadreza Kamali

doi:10.1007/s13202-021-01413-w

Majid Safaei-Farouji, Mohammad Hail Hakimi + Show 1 more

Open Access

https://doi.org/10.1007/s13202-021-01413-w

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Abstract

Geochemical study of Kazhdumi and Pabdeh Formations as potential source rocks in Gachsaran Oilfield demonstrates that the Kazhdumi Formation has a fair to good capability of hydrocarbon generation and predominately contains type II-III kerogen. On the other hand, the Pabdeh Formation has a poor to good petroleum potential and contains different kerogen types, including type II, type II-III, type III and even for one sample, type IV, indicating different depositional conditions for this formation. The geochemical log of the Kazhdumi Formation shows that there is a close correlation between different geological parameters as noticed prominently in well number 55, which suggests the more extensive the anoxic condition, the higher the petroleum potential is for Kazhdumi Formation. By contrast, a poor correlation between TOC and other Rock–Eval-derived parameters for the Pabdeh Formation at a depth of more than 2100 m may demonstrate the inert organic matter and mineral matrix effects at this depth interval. However, biomarkers show differences in lithology and depositional environment for the Kazhdumi Formation in well numbers 55 and 83. On the other hand, the Pabdeh Formation has a mixed lithology (carbonate-shale) deposited in a marine setting under suboxic–anoxic condition. Moreover, thermal maturity indicators suggest that Pabdeh and Kazhdumi Formations are immature and early mature, respectively.

Highlights

The middle Cretaceous to early Miocene petroleum system is the most prolific petroleum system (PS) in the Dezful Embayment and contains many Iranian oil reserves
It can be inferred that the Kazhdumi Formation is more productive than the Pabdeh Formation, which may represent a lower amount of inert organic matter, less mineral matrix effect as well as more anoxic condition during deposition of the Kazhdumi Formation
Geochemical log of the Kazhdumi Formation (Fig. 8) shows that there is a close correlation between different parameters, the relationship between petroleum potential and redox variation, especially in well number 55 (Fig. 8a)

Summary

Introduction

The middle Cretaceous to early Miocene petroleum system is the most prolific petroleum system (PS) in the Dezful Embayment and contains many Iranian oil reserves. In this embayment, Kazhdumi and Pabdeh Formations are principal organic-rich source rocks with great lateral extension. Geochemical characterization of these formations is bringing a better understanding of the depositional setting and their hydrocarbon source rock potential These formations have been studied frequently from organic geochemistry point of perspective (Bordenave and Huc 1995; Kamali et al 2006; Alizadeh et al 2012; Sfidari et al 2016). Safaei-Farouji et al (2021) and Safaei Farouji et al (2021) geochemically investigated the Kazhdumi and Pabdeh Formations along with oil samples in the Gachsaran Oilfield; detailed geochemical study of these super important formations is missing

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