Organic geochemical investigations of the Triassic Mianwali Formation in Surghar Range, Upper Indus Basin, Pakistan
Keywords:
Geochemical analyses, Mianwali Formation, Surghar Range, PakistanAbstract
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 OI, 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 °C to 429 °C showing insufficient temperature to produce
hydrocarbon at present condition. The overall high values of oxygen index (OI) 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.
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