An integrated palynofacies, geochemical and petrophysical analysis for characterizing mixed organic-rich carbonate and shale rocks of Dhulian oilfield Potwar Basin, Pakistan: Insights for multiple source and reservoir rocks evaluation

Abstract

The current study aimed to evaluate potential of multiple source and reservoir rocks of Potwar Basin, Pakistan. This study presents palynological, geochemical, and petrophysical data from source and reservoir rocks of Eocene and Paleocene sequences of the Dhulian oilfield. A total of 34 well cutting samples from two wells and four fresh outcrop samples were studied. Results of total organic carbon and Rock-Eval pyrolysis of the Sakesar Formation sediments shows good to very good TOC contents, whereas the Patala Formation sediments from well A shows very good to excellent and very good TOC contents in well B. S2 values of both formations’ samples showed fair to good generation potential. Both formations appear mature and have primarily type III and mixed type II-III kerogen with good gas-generation potential. Palynological analyses are in agreement with the pyrolysis data and showed that sediments have type III kerogen in the oil/gas window having excellent gas generation potential. Three kerogen assemblages were identified: palynomorphs, phytoclasts, and amorphous organic matter. Petrophysical analysis of the Chorgali Formation limestone showed an average porosity of ∼10.6%, with an average water saturation of ∼33.72%, and an average hydrocarbon saturation of ∼66.28%, thus indicating average to good reservoir potential. The findings of this research will help and guide exploration and production companies in the Potwar Basin in terms of source rock organic richness and maturity.