Determination of system tract, kerogen type and hydrocarbon production potential, using Rock-eval parameters (examples from Pabdeh Formation, Razan/Ab-e-Garm subzone and Persian Gulf bed sediments)

      Abstract   In order to determine kerogen type, system tract and hydrocarbon production potential three different regions, including Pabdeh Formation in folded Zagros zone, Razan/Ab-e-Garm subzone (Jurassic sediments of Dehlyan and Ghameshlo sections) and 15m core of the Persian Gulf bed sediments in Bushehr region were investigated using Rock-eval parameters. Field studies and examinations on Jurassic facies of Razan/Ab-e-Garm subzone indicate that Ghameshlo section contains four parts (lower sandstone, sandy shale, upper sandstone and alternation of sandstone and mica-bearing shale), and Dehlyan section has five parts (shale, siltstone, lower sandstone, sandy limestones and upper sandstone). Based on similar studies on Pabdeh Formation facies (mudstone, packstone, wackestone and shale), seven group of microfacies were studied. Based on granulometry analysis on studied core of the Persian Gulf in the coastal area of Bushehr, five sedimentary types comprising clayey silt, sandy mud, Gravelly mud, gravelly muddy sand were determined. Based on organic geochemistry studies, 65% of bitumen-bearing samples in of middle and lower parts of pabdeh formation are in mature (oil-prone), and 35% in immature stages. Based on these studies, samples of Razan/Ab-e- Garm subzone produce gas. But these mentioned samples are poor in hydrocarbon generation. Studied kerogens indicate the following results kerogen types II and II-III are the most abundant in Pabdeh Formation, kerogen types II,III and mixture of II-III are in majority in Bushehr core, and kerogen types III and IV are the commonest in Razan/Ab-e-Garm subzone. Based on hydrogen index versus TOC (total organic carbon) diagram, the results are as follows.In Bushehr core, 73% of studied samples indicate transgressive systems tract, and 27% of them are placed in low stand system tract. Meanwhile, Pabdeh Formation samples indicate transgressive systems tract, and Razan/Ab-e-Garm samples exhibit low stand system tract.