Research paper Geochemical characteristics and hydrocarbon generation modeling of the Kazhdumi (Early Cretaceous), Gurpi (Late Cretaceous) and Pabdeh (Paleogene) formations, Iranian sector of the Persian Gulf Zahra Sadat Mashhadi a , Ahmad Reza Rabbani a, * , Mohammad Reza Kamali b a Petroleum Engineering Department, Amirkabir University of Technology, Hafez Street, Tehran,15875-4413, Iran b Research Institute of Petroleum Industry (RIPI), West Blvd. Azadi Sport Complex, Tehran,14665-37, Iran article info Article history: Received 29 October 2014 Received in revised form 27 July 2015 Accepted 5 August 2015 Available online xxx Keywords: Persian Gulf Kazhdumi Formation Gurpi Formation Pabdeh Formation RockeEval pyrolysis Organic petrography Hydrocarbon generation modeling abstract The marls and argillaceous limestones of the Early Cretaceous Kazhdumi, Late Cretaceous Gurpi and Paleogene Pabdeh formations are considered as potential source rock candidates in this area. The present study characterizes hydrocarbon potential, type of organic matter and thermal maturity of these three formations in the Iranian sector of the Persian Gulf. Also, 1D basin modeling was used to analyse the burial history and timing of hydrocarbon generation in these formations. A total of 179 cutting samples from 25 wells were evaluated through RockeEval pyrolysis and organic petrography. Average total organic carbon (TOC) content for the samples of the Kazhdumi, Gurpi and Pabdeh formations that were analyzed for the current study is 1.2, 0.9 and 1 wt.%, respectively. All three formations show lower TOC contents in central part relative to eastern and western parts of the study area. RockeEval pyrolysis and organic petrography show that the organic matter in all three formations is mainly composed of Type II and mixed Type IIeIII kerogen. This study shows that the Kazhdumi, Gurpi and Pabdeh formations in Iranian offshore areas are not as rich as onshore areas, and specifically in the Dezful Embayment, in terms of organic matter quantity and quality. Thermal history modeling indicates that constant heat flow values in the range of 64e73 mW/m 2 gives the best fit between measured and calculated vitrinite reflectance and bottom hole temperature. The RockeEval T max , vitrinite reflectance and the generated models suggested that in the eastern parts of the study area, the Kazhdumi Formation is at the last stage of oil generation and the Gurpi and Pabdeh formations are within the main oil generation window. Hydro- carbon generation began in the Early Eocene, Middle Eocene and Early Miocene in the Kazhdumi, Gurpi and Pabdeh formations, respectively. In the western parts of the Persian Gulf, the Kazhdumi Formation is within the main oil window with hydrocarbon generation took place during the Oligocene and the Gurpi and Pabdeh formations are early mature and immature, respectively. All three formations are thermally immature in the central part of the Persian Gulf. The Kazhdumi Formation shows positive correlation with the crude oils of the Cretaceous and Tertiary reservoirs taken from the northwestern Persian Gulf. The Pabdeh and Gurpi formations show no correlation with crude oils produced in the northwestern and southeastern Persian Gulf. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The Persian Gulf and neighboring countries contain approxi- mately two thirds of the world's oil proven reserves, and one third of the global gas reserves due to coexistence of several layers of excellent source rocks, porous and permeable limestone and sandstone reservoirs, excellent cap rocks, huge anticlinal and salt- related domes (Fig. 1). Bordenave and Hegre (2005, 2010) identified several petroleum systems in the Zagros Foldbelt and adjacent Persian Gulf, among them, the prolific Middle Cretaceous to Early Miocene Petroleum system. Early Cretaceous Kazhdumi, Late Cretaceous Gurpi and Paleogene Pabdeh formations are important source rock candidates of this petroleum system. For this system, the Asmari and Bange- stan carbonates are the main reservoirs; the Asmari reservoir is efficiently capped by evaporites of the Gachsaran Formation of the * Corresponding author. E-mail address: Rabbani@aut.ac.ir (A.R. Rabbani). Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo http://dx.doi.org/10.1016/j.marpetgeo.2015.08.008 0264-8172/© 2015 Elsevier Ltd. All rights reserved. Marine and Petroleum Geology xxx (2015) 1e20 Please cite this article in press as: Mashhadi, Z.S., et al., Geochemical characteristics and hydrocarbon generation modeling of the Kazhdumi (Early Cretaceous), Gurpi (Late Cretaceous) and Pabdeh (Paleogene) formations, Iranian sector of the Persian Gulf, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/j.marpetgeo.2015.08.008