Sedimentology and reservoir characterization of Upper Cretaceous Kawagarh Formation, Upper Indus Basin, Lesser Himalayas, Pakistan: inferences from petrography, SEM-EDS and petrophysics.

Tight carbonate reservoirs are complicated by their vast heterogeneity, which is attributed to diagenetic and depositional processes. The new discovery of natural gas in the tight carbonate reservoir of the Upper Cretaceous Kawagarh Formation (KF− UC) in Pakistan makes it crucial to study the factors controlling reservoir properties. This study investigated the sedimentology and reservoir characteristics of KF− UC using integrated petrography, scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), and petrophysical techniques. The microfacies analysis of KF− UC indicates mudstone and wackestone, identified in the proximal and distal outer ramp settings of the homoclinal carbonate ramp. Diagenetic processes such as compaction, micritization, dolomitization, cementation, neomorphism, and dissolution, which represent meteoric and marine phreatic mixing zones and burial diagenetic settings, have modified the reservoir characteristics of KF− UC. The net porosity of KF− UC could be enhanced by dolomitization, dissolution, and fracturing, making it a better petroleum reservoir. With an average porosity of 2.3%, microporosities such as intercrystalline/interparticle, intracrystalline/intraparticle, vuggy, and fracture were identified in KF− UC, designating it as a tight carbonate reservoir. The outcrop and well data exhibit excellent correlation; nevertheless, the well’s net pay is inadequate due to the influence of complex tectonic structures along significant faults within the study area. Furthermore, the results of this study were compared with the Gurpi Formation of Zagros Basin, Iran, and the Aruma Formation of Central Saudi Arabia, highlighting similar sedimentological characteristics, thus emphasizing the need to initiate such projects in other regions with similar settings to further strengthen petroleum exploration. [ABSTRACT FROM AUTHOR]