Hydrocarbon Source Rock Potential of the Late Paleocene Patala Formation, Kohat Basin, Pakistan

Abstract

The Late Paleocene Patala Formation shales exposed at Tarkhobi Nala, Kohat Basin, Pakistan were geochemically studied in detail for hydrocarbon evaluation. A total of 09 shale samples of the studied formation were analyzed in G & R Labs, Oil & Gas Development Company Limited (OGDCL), Islamabad, Pakistan for TOC and Rock-Eval pyrolysis. The TOC results were low ranging from 0.36 wt. % to 1.25 wt. % indicating poor to fair petroleum potential except a sample falling in the good source rock category. The generating potential values (< 2 mg HC/ g. rock) also show poor ability for hydrocarbon production. The different cross plots between Rock-Eval pyrolysis parameters (HI vs OI; HI vs Tmax; S₂ vs TOC) were used to describe the types of kerogen and thermal maturity of the evaluated samples. All these plots confirmed the presence of type IV kerogen which has no capability to generate hydrocarbon except minor gas upon thermal maturation. The thermal maturity of the organic matter was assessed by Tmax (444 °C to 459 °C) which shows that the studied formation is falling in the oil window but due to the presence of type IV (oxidized & reworked) organic matter not able to generate commercial hydrocarbons.