GEOCHEMICAL INVESTIGATION OF THE EARLY EOCENE LAKI FORMATION SHALES IN THE SELECTED REGIONS OF SOUTHERN INDUS BASIN PAKISTAN

Abstract

A systematic geochemical investigation of the Laki Formation from the selected regions of Southern Indus Basin Pakistan Basin has been carried out. This paper presents the characterization of hydrocarbon potential, type of kerogen, thermal maturity, the origin of organic matter, depositional environment, and bulk mineralogy of the Laki Formation shales. The total organic carbon (TOC) content of the Laki shale ranges from 0.53 to 2.66 wt. %. The values indicate that Laki shales have fair to very good hydrocarbon potential. Type III kerogen is identified in the Laki shale based on TOC and residual potential (S2) data. Maturity parameters (Tmax & Methyl phenanthrene index) suggest that Laki shales are thermally immature for the generation of hydrocarbons. Normal alkane data and stable carbon (δ13C) isotopic value (-9.67 ‰ PDB) of the Laki shale indicates the predominantly marine origin of the organic matter. Dibenzothiophene/phenanthrene (DBT/P) ratio (0.08), Phytane (Ph)/n-C18 versus Pristane (Pr)/n-C17, and Pr/Ph versus DBT/P data suggest a marine environment of the Laki shale. The marine setting of the Laki Formation shale is further evident by coralline algae and Alveolina oblonga. X-ray diffraction (XRD) data reflect that Laki shale is brittle since it is dominated by high quartz and carbonates.