Facies Analysis, Sequence Stratigraphy and Diagenetic Studies of the Jurassic Carbonates of the Kohat Basin, Northwest Pakistan: Reservoir Implications

The present study deals with the depositional facies, diagenetic processes and sequence stratigraphy of the shallow marine carbonates of the Samana Suk Formation, Kohat Basin, in order to elucidate its reservoir quality. The Samana Suk Formation consists of thin to thick‐bedded, oolitic, bioclastic,...

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Published in:Acta geologica Sinica (Beijing) 2022-10, Vol.96 (5), p.1673-1692
Main Authors: KHAN, Emadullah, NASEEM, Abbas Ali, KHAN, Suleman, WADOOD, Bilal, REHMAN, Faisal, SALEEM, Maryam, MEHMOOD, Mubashir, AHMAD, Waqar, AHMED, Zubair, AZEEM, Tahir
Format: Article
Language:English
Subjects:
Biofacies
Carbonates
Cementation
Diagenesis
Dissolution
Dissolving
Dolomite
Dolomitization
Dolostone
Jurassic
Kohat Basin
Limestone
Mudstone
Outcrops
Permeability
Porosity
reservoir
Reservoirs
Samana Suk Formation
Sedimentary facies
Sequence stratigraphy
Sequencing
Shoals
Stratigraphy
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Summary:The present study deals with the depositional facies, diagenetic processes and sequence stratigraphy of the shallow marine carbonates of the Samana Suk Formation, Kohat Basin, in order to elucidate its reservoir quality. The Samana Suk Formation consists of thin to thick‐bedded, oolitic, bioclastic, dolomitic and fractured limestone. Based on the integration of outcrop, petrographic and biofacies analyses, the unit is thought to have been deposited on a gentle homoclinal ramp in peritidal, lagoonal and carbonate shoal settings. Frequent variations in microfacies based sea‐level curve have revealed seven Transgressive Systems Tracts (TSTs) and six Regressive Systems Tracts (RSTs). The unit has undergone various stages of diagenetic processes, including mechanical and chemical compaction, cementation, micritization, dissolution and dolomitization. The petrographic analyses show the evolution of porosity in various depositional and diagenetic phases. The fenestral porosity was mainly developed in peritidal carbonates during deposition, while the burial dissolution and diagenetic dolomitization have greatly enhanced the reservoir potential of the rock unit, as is further confirmed by the plug porosity and permeability analyses. The porosities and permeabilities were higher in shoal facies deposited in TSTs, as compared to lagoonal and peritidal facies, except for the dolomite in mudstone, deposited during RSTs. Hence good, moderate and poor reservoir potential is suggested for shoal, lagoonal and peritidal facies, respectively.
ISSN:1000-9515
1755-6724
DOI:10.1111/1755-6724.14938