Geochemical characterization of cretaceous sediments—Sindh Basin, Pakistan.

This study includes geochemical characterization of source rock samples from the Upper shale, Lower shale, Talhar shale units of Sembar Formation and Badin shale, Turk shale units of Lower Goru Formation. Fourteen (14) sediment samples have been obtained from various wells located in Badin area of Lower Indus Basin and were analyzed to evaluate thermal history, depositional settings and generative potential. The bitumens obtained by soxhlet extraction were fractionated into saturates, aromatics, NSOs and asphaltenes/resins by column chromatography on silica gel. Saturated fractions isolated by column chromatography were analyzed by Gas Chromatography-Flame Ionization Detector. TOC determined by wet combustion titration method revealed fair to good source rock potential. Pr/Ph ratios and hydrocarbons distributions show anoxic to oxic depositional environment. The TAR ratio,nC31/nC19ratio, and odd carbon number predominance suggest land plant organic matter input. The values of CPI, OEP and Bit/TOC suggest that these Cretaceous sequences of Sembar and Lower Goru formation are of intermediate maturity and lie within the onset of oil genesis zone. [ABSTRACT FROM PUBLISHER]