Organic Geochemistry and Source Rock Characteristics of Salt Range Formation, Potwar Basin, Pakistan.

The hydrocarbon source potential of Precambrian Salt Range Formation was assessed by analysis of 91 outcrop and core samples using Leco (total organic carbon contents), pyrolysis, liquid column chromatography, gas chromatography, gas chromatography mass spectrometry,vitrinite reflectance spectroscopy and low carbonisation analysis (Fisher Assay). The formation is exposed along the outer periphery of the Salt Range from Kalabagh in the west to the eastern Salt Range. The oil shales found near the top of the Precambrian Salt Range Formation of eastern Salt Range are extremely rich in organic carbon, with TOC of upto 30 % and have excellent geochemical source rock parameters (HI upto 879 mg/kg and Extractable Organic Matter (EOM)/TOC upto 255 mg/kg). Also the low grade oil shales found in the central and western salt range are excellent potential source rocks having TOC 2.5-8%, HI upto 746 mg/kg and EOM/TOC mg/kg upto 204. The EOM of most of the surface samples from Salt Range Formation co nt ai ns le ss than 20% satu ra ted hydrocarbons (SHC), which suggests their low maturity. However, the oil shale extracts have SHC portion slightly more than 40%. The organic matter cons is ts predominantly of prebitumen and solid bitumen, and partly contains major proportions of liptinite. The oil yield of high-grade oil shales varies from 15 to 20% of rock weight.