Organic geochemical investigations of the Triassic Mianwali Formation in Surghar Range, Upper Indus Basin, Pakistan

The Shales of Mianwali Formation in Surghar Range, Pakistan has been analyzed and studied geochemically to assess its hydrocarbon potential, types of organic matter and thermal maturity. Organic geochemical analyses were carried out on fifteen outcrop samples of the studied formation. Various screening techniques including TOC measurement, Rock Eval pyrolysis were used to evaluate the hydrocarbon potential, types of organic matter and thermal maturity of the studied formation. The average total organic carbon values and genetic potential (GP) are < 0.5 wt. % & < 2 kg/ton respectively, indicated that the sediments has poor source rock potential. The different cross plots including hydrogen & oxygen indices HI vs CH, HI vs Tmax and S2 vs TOC indicated that the formation is dominated by type IV kerogen. The Tmax values of analyzed samples ranges from 418 degrees C to 429 degrees C showing insufficient temperature to produce hydrocarbon at present condition. The overall high values of oxygen index (0I) and low values of hydrogen index (HI) represents the organic matter of the studied samples are poorly preserved and oxidized consisting type IV kerogen in the studied section. The source rocks geochemistry is a best tool to identify a petroleum system in an area, as multiple source rocks are present in Surghar Range and most wells are abandoned in the study area. So, this study was aimed to geochemically analyzed and study the outcrop samples of this formation, and correlate with the subsurface.