Thermal modeling of the Garau (Aptian-Cenomanian) Formation as a formation with potential rock source of gas shales in the west of Kermanshah

The Garou Formation (Aptian – Cenomanian) is one of the hydrocarbon-generating formations in the Zagros Basin. The lithology of the Garou Formation in the study area has been alternative to clay-limestone and shale which is dominated by shale facies. This study has been selected as the source rock of gas shale for organic geochemistry studies of Garou Formation and 26 intact and non-aerated rock samples were taken through the water transfer tunnel of this formation, NW Kermanshah. The samples were analyzed by Rock-Eval 6 pyrolysis method. Based on studies, the dominant kerogen type III is the Garau Formation was recognized. In terms of genetic potential, the Garu Formation is poor to relatively good source rock, but its hydrocarbon potential ranks poor. The reflection of vitrinite in most of the Garau Formation specimens is more than 1.3 percentage and indicating a source rock in the gas production stage, which is confirmed by Tmax more than 440 C°. Furthermore, the thermal history model of the Garau Formation in the study area suggests that this formation entered to catagenetic range in Paleogene and reached high thermal maturity in the late Neogene. The existing methane and carbon dioxide in the tunnel with a concentration of more than 1800 ppm can be attributed to the generation of gaseous hydrocarbons according to the results of thermal history modeling that this volume of exhaust gas is related to the shales of the Garau Formation.