INTEGRATED CORE BASED AND WELL LOG STUDIES TO BETTER CHARACTERIZE FACIES AND DIAGENETIC PHASES OF EOCENE SAKESAR FORMATION, POTWAR SUB-BASIN, PAKISTAN

Abstract

The Sakesar Limestone of Early Eocene is studied for facies characterization and diagenetic studies using core of Balkasar-7, Potwar sub-basin. The Sakesar Limestone in the studied core is mainly comprised of Limestone, Dolomitic limestone and Argillaceous / Shaly Limestone. For petrographic study 26 samples were selected and on the basis of petrographic obeservation seven microfacies are identified which include, Larger Foraminiferal Wackestone-Packstone, Bioclastic-Nummulitidae Wackestone, Assilina Nummulitic Packstone, Planktonic Miscellania Wackestone-Packstone, Bioclastic Wackestone, Nummulitic - Lockhartia dolomitic Wackestone-Packstone and Ranikothalia – Assilina dolomitic Wackestone-Packstone. In microfacies, the abundance of the different fossils relative to the matrix ratio suggest that the depositional settings of the Sakesar Limestone are lie in proximal Inner ramp to the Middle ramp, while one facie extends up to the outer ramp settings. Different diagenetic features are identified during studies which contain compaction, cementation, micritization, neomorphism, dissolution and dolomitization. Micritization is the most common phenomena observed in the diagenetic studies. The dolomitization in the Sakesar Limestone found along fracture veins, stylolites and within matrix indicating the deep burial diagenetic conditions. The presence of fenestral porosity and vugs in the core studies provide evidence of the late stage diagenesis. These features suggest that the Sakesar Limestone has faced early stage diagenetic to late diagenetic changes. The electrofacies analysis are conducted by K mean Clustering method using well log of Balkasar Oxy-1. The electrofacies shows the dominant lithology of the Limestone in well which is followed by the Shaly limestone and Calcareous shale. The correlation of both wells and their lithological data shows same pattern of facies distribution