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Integrated facies analysis and diagenetic impact on carbonate reservoirs: a case study from Jurassic shallow marine carbonate platform, NW Himalayas, Pakistan.

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Title: Integrated facies analysis and diagenetic impact on carbonate reservoirs: a case study from Jurassic shallow marine carbonate platform, NW Himalayas, Pakistan.
Authors: Ullah, Ihsan1 (AUTHOR), Jamil, Muhammad1 (AUTHOR) jamil287@gmail.com, Rahim, Hamad ur2,3 (AUTHOR), Khan, Imran1,4 (AUTHOR) imrankhan@cuiatd.edu.pk, Abbas, Wahid1 (AUTHOR), Ali, Asad1 (AUTHOR), Rehman, Mohib Ur1 (AUTHOR)
Source: Carbonates & Evaporites. Jun2026, Vol. 41 Issue 2, p1-22. 22p.
Abstract: Carbonate reservoirs exhibit diverse depositional backgrounds linked with distinct diagenetic evolution that impart reservoir characteristics due to the development of secondary pore network. Hence, it is indispensable to evaluate the impact of various diagenetic events on depositional architecture of carbonates. The present work encompasses shallow marine Jurassic carbonates which are considered deeper subsurface targets for petroleum reservoirs in the Upper Indus Basin, Pakistan. Sedimentological field observations complemented by petrographic studies, scanning electron microscopy and porosity permeability measurements define the reservoir intervals in these carbonate rocks. Outcrop observations reveal thick-bedded to massive limestone units with occasional marl, dolomitic patches, and shale laminae. These lithological units exhibit diagenetic expressions including stylolites, fractures and dolomitization at mesoscopic level. The microfacies include mudstone, bioclastic dolowackestone, bioclastic dolopackstone, dolomitic grainstone, and bioclastic peloidal ooidal grainstone deposited in intertidal, inner to middle ramp settings that were later diagenetically altered by dolomitization, fracturing, dissolution, and stylolitization thereby enhancing the pore network distribution. However, cementation, micritization, and mechanical compaction had an adverse impact by reducing the reservoir pore spaces. The porosity types include vuggy, mouldic, fenestral, and dissolution porosity having porosity values ranging from 2.5 to 5.5% and permeability from 0.2-6.5mD primarily developed by bedding planes, fracturing, stylolitization and dissolution. Based on these studies, it has been inferred that Chichali Nala and Kahi Section (NE) have better reservoir potential depositionally which has been further enhanced by diagenetic features and fractures. Reservoir potential of Paniala Section (SW) on the other hand is primarily attributed to the diagenetic features. The study emphasizes the role of diagenetic processes as the key factor that determines the reservoir pore spaces for petroleum potential in carbonate reservoirs. Hence, it is essential to integrate the diagenetic evolution and sedimentary architecture of the carbonate reservoirs to interpret reservoir intervals for petroleum exploration and production. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Carbonate reservoirs exhibit diverse depositional backgrounds linked with distinct diagenetic evolution that impart reservoir characteristics due to the development of secondary pore network. Hence, it is indispensable to evaluate the impact of various diagenetic events on depositional architecture of carbonates. The present work encompasses shallow marine Jurassic carbonates which are considered deeper subsurface targets for petroleum reservoirs in the Upper Indus Basin, Pakistan. Sedimentological field observations complemented by petrographic studies, scanning electron microscopy and porosity permeability measurements define the reservoir intervals in these carbonate rocks. Outcrop observations reveal thick-bedded to massive limestone units with occasional marl, dolomitic patches, and shale laminae. These lithological units exhibit diagenetic expressions including stylolites, fractures and dolomitization at mesoscopic level. The microfacies include mudstone, bioclastic dolowackestone, bioclastic dolopackstone, dolomitic grainstone, and bioclastic peloidal ooidal grainstone deposited in intertidal, inner to middle ramp settings that were later diagenetically altered by dolomitization, fracturing, dissolution, and stylolitization thereby enhancing the pore network distribution. However, cementation, micritization, and mechanical compaction had an adverse impact by reducing the reservoir pore spaces. The porosity types include vuggy, mouldic, fenestral, and dissolution porosity having porosity values ranging from 2.5 to 5.5% and permeability from 0.2-6.5mD primarily developed by bedding planes, fracturing, stylolitization and dissolution. Based on these studies, it has been inferred that Chichali Nala and Kahi Section (NE) have better reservoir potential depositionally which has been further enhanced by diagenetic features and fractures. Reservoir potential of Paniala Section (SW) on the other hand is primarily attributed to the diagenetic features. The study emphasizes the role of diagenetic processes as the key factor that determines the reservoir pore spaces for petroleum potential in carbonate reservoirs. Hence, it is essential to integrate the diagenetic evolution and sedimentary architecture of the carbonate reservoirs to interpret reservoir intervals for petroleum exploration and production. [ABSTRACT FROM AUTHOR]
ISSN:08912556
DOI:10.1007/s13146-026-01253-x