Abstract:
Kohat basin is present in the northwest extension of Indus basin KPK, Pakistan.
It is the main hydrocarbon producing basin of the province. It has numerous petroleum
plays in production and potential categories from Cambrian to Miocene. Detailed
geochemical analyses of well cutting of Tolanj-01 were carried out to understand the
Paleocene (Patala, Lockhart and Hangu Formation) potential in the basin. The
geochemical analysis included total organic carbon (TOC), rock Eval pyrolysis (RE)
and organic petrography (vitrinite reflectance). These results were used to evaluate
organic richness, thermal maturity, kerogen type, hydrocarbons type and environment
of deposition were determined. Well cuttings of Hangu Formations (0.08-1.8) shows
poor to Good, Lockhart limestone (0.05-0.5) poor to fair and Patala Formation (0.8-
0.19) shows poor to fair TOC content. The present kerogen appears to be Type III.
Thermal maturity of the extracts shows high thermal maturity and mature oil zone. GP
is generally poor but some of Lockhart limestone and Hangu Formation shows Fair
potential. Vitrinite reflectance of all these formations exist in oil window. Ro values are
in the range of 0.82 to 0.95 %. Pr/Ph values are greater than 1 which indicates the
presence of sub-oxic environment of deposition. Pr/n-C17 versus Ph/n-C18 shows that
the extracts falls in the category of mixed organic matter deposited in transitional
depositional settings. C19TCT/C19TCT+C23TCT ratio, C24TeCT/ C24TeCT+ C23TCT
ratio indicate source as marine. Ternary diagram shows as higher plant input for
Lockhart and Hangu Formation while Patala shows higher marine input. CPI, 2-MP
and 3-MP show higher thermal maturity. Pr/n-C17 versus Ph/n-C18, shows higher
thermal maturity. Moretane index, extracts fall in thermally mature window. Ts/Ts+Tm
ratio shows more thermal maturity. Steranes value shows extracts as mature and fall in
oil window.
