Geochemical characteristics and hydrocarbon potential of Cretaceous Upper Shale Unit, Lower Indus Basin, Pakistan

Abstract

This study focuses on the geochemical investigation of source rock samples from three different wells of upper shale unit (Lower Goru Formation; Lower Indus Basin). Samples were powdered to very fine particle size and extracted soluble organic matter (SOM) was fractionated using column chromatography. The saturated hydrocarbon fraction was further analyzed to evaluate source rock potential and organic matter type. Total organic carbon reflected fair source rock potential. The values of Pr/Ph, Pr/n-C17 vs. Ph/n-C18, C31/C19 show that organic matter is mainly terrestrial and depositional conditions varies from anoxic to the dysoxic. Different maturity parameters including Bit/TOC ratio, carbon preference indices revealed mature organic matter input and peak oil-window for the samples. Furthermore, bitumen transformation ratio indicates increase in thermal maturity with increasing depth. Based on these data, it may be said that the shale unit is probably fair candidate for hydrocarbon generation perspective.