GEOCHEMICAL CHARACTERIZATION OF THE CAMBRIAN-EOCENE HYDROCARBON SOURCE ROCKS IN THE INDUS BASIN, PAKISTAN

The hydrocarbon source rock potential of the Precambrian-Tertiary strata of the Indus Basin, Pakistan has been evaluated through the total organic content (TOC) and Rock Eval Pyrolysis techniques. Different geochemical parameters were plotted in different data sets to determine the TOC, Kerogen type, level of maturity and migration of hydrocarbons. Organic rich shale samples were collected from five key stratigraphic sections. The Precambrian, Salt Range Formation shows Type I kerogen with immature indigenous hydrocarbons potential. The Cambrian, Kussak and Baghanwala formations shows immature Type I and Type III kerogen, having a poor genetic potential. The Permian, Tobra, Dandot, Warchha, Sardhai, Wargal and Chhidru formations show a mature Type III kerogen and a poor genetic potential. The Triassic, Mianwali and Tredian formations show immature Type III kerogen and a poor genetic potential. The Jurassic Datta, Shinawari and Samana Suk formations have immature, Type III kerogen, exhibiting a poor genetic potential. The Cretaceous Sember, Moghal Kot, Fort Munro, Pab Sandstone, Chichali and Lumshiwal formations have immature-over mature, Type III kerogen having a poor genetic potential. The Paleocene Patala formation bears mature, Type III kerogen in the lower part and immature, Type III kerogen in the upper part. The Eocene Ghazij formation have shown immature, mature and over mature Type III kerogen and the Habib Rahi member of the Kirthar formation has immature, Type I kerogen showing a good genetic potential, while the Nammal formation source rock quality is good, Immature, Type I, Type III kerogen is recognized in upper and lower parts respectively and indigenous hydrocarbon occurs.

The analyzed samples suggest that there has been fluctuation in organic content cooking with fewer samples showing mature state while some with immature and over mature thermal state are also present. The organic content found in most organic rich shales were Type III kerogen, having a greater potential of generating gas while few samples contain Type I kerogen shows oil bearing organic content. The genetic potential with TOC has been analyzed thoroughly suggesting that most samples have poor genetic potential and few samples show very good genetic potential.