Geochemical Analysis and Source Rock Evaluation of Paleocene Formations in Kohat sub-basin, Pakistan

Abstract

The present study deals with the geochemical analysis and source rock evaluation of Paleocene strata in Chanda-01 well of Kohat sub-basin, Pakistan. The Kohat Basin is located KPK region of Pakistan, which is northwestern part of the Indus Basin, which include multiple active petroleum fields and prospective strata ranging from the Cambrian to the Miocene. To evaluate the Paleocene (Hangu, Lockhart and Patala formations) potential in the basin, a thorough geochemical investigation and source rock evaluation of Chanda-01's well cuttings was conducted. Total organic carbon (TOC), Rock Eval-Pyrolysis (RE) and Organic Petrography (Vitrinite Reflectance) techniques were employed. Apart from common traditional methods of (TOC) determination, Density Log and ΔlogR methods were also chosen to estimate TOC for correlation. The conclusions were utilized to assess the degree of organic richness, thermal maturity, kerogen type and hydrocarbon type. The TOC values of Hangu Formation is 0.9 to 4.2 % lies in fair to excellent, Lockhart Formation (1.7 %) lies in good and Patala Formation 0.82 to 2.7 % shows fair to good TOC content. Schmoker and Hester method TOC averages are 5.3 %, 3.23 % and 2.34 % with in Hangu, Lockhart and Patala Formation respectively. Passey method TOC averages are 1.56 %, 1.67 %, 1.88 % with in Hangu, Lockhart and Patala Formation respectively. The kerogen currently seems to be of Type III. The extracts represent mature oil zone and high thermal maturity. Generation Potential is mostly poor but at some points of Patala and Hangu shows Fair to good potential. The Vitrinite Reflectance of all the formations exist in oil window. Ro values are in the range of 0.78 to 0.94 %, which represents vitrinite is the dominant maceral in Paleocene strata. The second principal maceral is inertinite and third maceral is solid bitumen. Pyrite is observed as the main accessory mineral in Paleocene strata. In conclusion, the Paleocene formations showing poor to moderate source rock potential in Chanda-01 well.