The geochemical analysis and hydrocarbon generation potential of source rocks from upper Cretaceous to Eocene sedimentary sequences (southwest Iran)

Abstract

ABSTRACT The Zagros sedimentary basin in Iran is one of the most significant basins worldwide due to its potential for petroleum generation. This study assessed the hydrocarbon generation potential of the Gurpi and Pabdeh Formations as potential source rocks. For this purpose, ten samples were taken from the Pabdeh and Gurpi Formations and analyzed using Rock-Eval® 6 Turbo. The Rock-Eval data indicated that the Pabdeh and Gurpi Formations had hydrocarbon generation potential. Two of the samples from the Pabdeh and Gurpi Formations showed fair and high potential for hydrocarbon generation, respectively. Organic matter in the Gurpi Formation showed a type II kerogen, while types II and III kerogens of oil and gas prone hydrocarbons were determined in the Pebdeh Formation, respectively. Samples of the both formations were in the thermally immature stage. In addition, the determination of organic facies indicated that the sedimentary facies of the Pabdeh Formation were deposited with rapid sedimentation rates in deep marine environments due to adjoining orogenic points. Moreover, the sedimentary facies of the Gurpi Formation were an indicator of the rate of relatively reductive marine environment conditions to relatively oxidative environments with average sedimentation. The maximum and minimum organic matter content was 2.5 and 0.26 for the Pabdeh Formation and 0.88 and 0.54 for the Gurpi Formation, respectively. Moreover, the dead organic carbon content was 0.1682 wt% for the Gurpi Formation and 0.6734 wt% for the Pabdeh Formation. The determination of hydrocarbon uptake (absorption) using the rock matrix suggested that the uptake rate was higher in the samples of the Gurpi Formation than in those of the Pabdeh Formation. This indicated that the rock matrix had more clay minerals in the Gurpi Formation than in the Pabdeh Formation.