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The present study is focused on formation evaluation of the Lockhart Limestone in two wells (Meyal-05P and Meyal-10P) located in Northern Deformed Potwar Zone of the Potwar sub-basin, Pakistan. The geological formations ranging from Triassic to Pliocene have been drilled in these wells. The formation evaluation of the Lockhart Limestone mainly involves reservoir potential evaluation, interpretation of depositional environment and transgressive-regressive sequences using petrophysical logs. In either wells, the reservoir characterization is steered by various petrophysical parameters including calculation of volume of shale, porosity, permeability and hydrocarbon saturation. The thickness of the Lockhart Limestone is 50 m and 77 m in the Meyal-05P and Meyal-10P wells, respectively. In Meyal-05P and Meyal-10P wells, the average petrophysical parameters values and ranges are given as follows: volume of shale 48% and 20%; density porosity 1-5.6% and 1-31.7%; neutron porosity 1-23% and 1-42.9%; sonic porosity 1-29% and 1-39%; effective porosity < 1-> 5% and 1-21%; and hydrocarbon saturation 92.21-99.8% and 97-99.6%. The petrophysical parameters indicate that the Lockhart Limestone of Meyal-10P well is quantitatively better reservoir than that of the Meyal-05P. In Lockhart Limestone of either wells, the permeability is < 0.1 mD. The bulk volume water deciphered the presence of vuggy and intercrystalline porosity in the Lockhart Limestone. Similarly, the lithological interpretation using logs shows mainly limestone with minor shales. Different electrofacies are interpreted from the log trends of gamma ray log such as aggrading, prograding and retrograding depositional sequences deposited in tidal channel fill, shallow water, shore line and offshore buildup and regressive-totransgressive shore face depositional setting.

Copies of Supplementary Papers may be obtained from the Geological Society of Australia's website (www.gsa.org.au), the Australian Journal of Earth Sciences website (www.ajes.com.au) or from the National Library of Australia's Pandora archive (https://pandora.nla.gov.au/tep/150555).

The present study aims to evaluate the Paleocene to Early Eocene carbonates of the Dungan Formation in the Kirthar Fold and Thrust Belt, Pakistan for its paleo-depositional environment, sequence stratigraphy, and diagenetic effects on reservoir potential. The utilization of outcrop data for faunal identification and microfacies techniques helped in interpreting the paleo-environments and sequence stratigraphic framework. The microfacies analysis revealed that carbonates of the Dungan Formation in the Kirthar Fold and Thrust Belt represent a distal middle shelf-deep basinal settings of deposition. We documented a sea-level rise of second-order (spanning from Middle Danian to Ypresian) that in turn consists of a Transgressive Systems Tract (TST) and a Regressive Systems Tract (RST) of third-order cyclicity, spanning from Danian-Selandian and Thanetian-Early Ypresian respectively. The comparison with published data, the sea-level oscillations is influenced by eustacy and local tectonics. The hydrocarbon reservoir rock characterization of the carbonates is achieved by recording marine, burial, and meteoric diagenetic phases. The processes of cementation, micritization, neomorphism, and compaction occluded the effective porosity while dissolution and fracturing have enhanced the porosity and permeability of the rock unit. The petrographic evidence augmented by quantitative plug porosity and permeability data suggest poor to moderate reservoir potential of the carbonates of the Dungan Formation.

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The Middle Jurassic carbonate succession (Samana Suk Formation) in Kala Chitta Range, North Pakistan was studied in detail to investigate the impact of diagenesis on reservoir potential of the rock unit. The current study integrates detailed geological field, petrographic, scanning electron microscopic, and advance geochemical studies to reconstruct the diagenetic history of Jurassic carbonates and to evaluate its role in re‐shaping the reservoir potential. Based on field observations, five lithological units along with diagenetic features are recorded. Furthermore, various microfacies are defined within each lithological unit. Based on petrographic studies, it is observed that various diagenetic features including micritization, neomorphism, dissolution, compaction (mechanical and chemical), dolomitization, and cementation have played a crucial role in the porosity modification of various lithological units. The paragenetic sequence established in this study reveals modification of the carbonates in various diagenetic phases, for example, marine, meteoric, and burial (shallow and deep) diagenesis, followed by a phase of uplifting. Based on different types of microscopic porosities generated during various diagenetic phases, mudstone to wackestone carries good reservoir potential while the grainstone has moderate to poor potential. The plug porosity and permeability data further corroborate these findings. At outcrop, various large‐scale dissolution activities and dense network of inter‐connected fractures in all lithological units may have further enhanced the reservoir potential of the studied strata.

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In this paper, we present the palynostratigraphy, petrography, scanning electron microscopy (SEM) and X-ray diffraction (XRD) investigations to evaluate hydrocarbon reservoir potential of the Jurassic clastic-carbonate mixed sequence of the Kala Chitta Range, northwest Pakistan. The chronostratigraphic sub-divisions of the diverse lithologies within the sequence were made by using palynostratigraphy. The clastic dominated sequence of Datta Formation was assigned Toarcian-Bajocian age, while the Shinawari Formation was deposited during the Bajocian-middle Bathonian. The carbonate shoal facies of the Samana Suk Formation showed late Bathonian-Tithonian time of deposition. The primary and secondary porosities augmented by the plug porosity and permeability data suggest that the sandstone of Datta Formation is an excellent reservoir. The dominance of diverse matrix within the Shinawari Formation occluded the primary porosity. However, based on dissolution and dolomitization, the Shinawari Formation is categorized as a moderate reservoir. The dominance of various types of matrix and cement with superimposed burial diagenesis has occluded the primary porosity within the Samana Suk Formation. However, the diagenetic dissolution and dolomitization during the telogenetic stage were supported by the SEM and bulk geochemical data. Such diagenetic overprinting has significantly enhanced the reservoir potential of the unit.