Hydrocarbon potential and organic geochemistry of the Pabdeh Formation in the SW of Kermanshah Province (Gilan-e Gharb county)

The Pabdeh Formation was deposited during late Paleocene- early Oligocene in the Zagros Basin. Considerable parts of the formation comprise fine-grained sediments particularly variegated shale beds which were deposited in platform margin to deep sea environments. These depositional setting may promoted preservation of OM in these sediments. Hence, hydrocarbon potential and organic geochemistry of the Pabdeh Fm. were examined in a surface section located around the Sarhal-e Shirzadi village near the Gilan-e Gharb town. After sampling, a suite of 12 selected samples were analyzed by Rock-Eval. ΙΙΙ in the geochemistry lab. of the Research Institute for Petroleum Industry (RIPI). Low average TOC content of the samples (ave. 1.2 %) imply a poor source potential of the Pabdeh Fm. in this region. Furthermore, data revealed a mixture of various kerogen types including type Ι, ΙΙ, and ΙΙΙ as well, among which type ΙΙ is more frequent. This may reflect virtual marine nature of the Pabdeh Fm. Ro of most samples varies between 0.5 to 1.35 %, which means the Pabdeh Fm. reached the oil generation window. Cross-plot of Tmax vs. HI revealed the Pabdeh Fm. experienced catagenesis (Tmax > 435 OC). However, according to the calculated Tmax are not reliable, so do not reflect realistic thermal maturity of the Pabdeh Fm. In other words, Tmax and PI values calculated from Rock-Eval data suggest that only one sample passed into oil window. Organic facies of the Pabdeh Fm. comprising both platform and slope facies, which were probably deposited in the platform margin.