EGU21-12555
https://doi.org/10.5194/egusphere-egu21-12555
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Lithofacies, Depositional Environment and Diagenetic Evolution of the Paleocene Patala Formation, Potwar Basin, Pakistan: Implication for Shale Gas Potential

Nasar Khan1,2, Rudy Swennen1, Gert Jan Weltje1, and Irfan Ullah Jan3,4
Nasar Khan et al.
  • 1KU Leuven, Earth and Environmental Sciences, Geology, Belgium (nasar.khan@kuleuven.be)
  • 2Department of Geology, University of Malakand, Chakdara 18800, Khyber Pakhtunkhwa, Pakistan
  • 3National Centre of Excellence in Geology, University of Peshawar, Peshawar 25130, Pakistan
  • 4University of Regina, Geology 3737 Wascana Parkway Regina, SK, CAN S4S 0A2, Canada

Abstract: Reservoir assessment of unconventional reservoirs poses numerous exploration challenges. These challenges relate to their fine-grained and heterogeneous nature, which are ultimately controlled by depositional and diagenetic processes. To illustrate such constraints on shale gas reservoirs, this study focuses on lithofacies analysis, paleo-depositional and diagenetic evolution of the Paleocene Patala Formation at Potwar Basin of Pakistan. Integrated sedimentologic, petrographic, X-ray diffraction and TOC (total organic carbon) analyses showed that the formation contained mostly fine-grained carbonaceous, siliceous, calcareous and argilaceous siliciclastic-lithofacies, whereas carbonate microfacies included mudstone, wackestone and packstone. The silicious and carbonaceous lithofacies are considered a potential shale-gas system. The clastic lithofacies are dominated by detrital and calcareous assemblage including quartz, feldspar, calcite, organic matter and clay minerals with auxiliary pyrites and siderites. Fluctuations in depositional and diagenetic conditions caused  lateral and vertical variability in lithofacies. Superimposed on the depositional heterogeneity are spatially variable diagenetic modifications such as dissolution, compaction, cementation and stylolitization. The δ13C and δ15N stable isotopes elucidated that the formation has been deposited under anoxic conditions, which relatively enhanced the preservation of mixed marine and terrigenous organic matter. Overall, the Patala Formation exemplifies deposition in a shallow marine (shelfal) environment with episodic anoxic conditions.

Keywords: Lithofacies, Organic Matter, Paleocene, Potwar Basin, Shale Gas, Shallow Marine.

How to cite: Khan, N., Swennen, R., Weltje, G. J., and Jan, I. U.: Lithofacies, Depositional Environment and Diagenetic Evolution of the Paleocene Patala Formation, Potwar Basin, Pakistan: Implication for Shale Gas Potential, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12555, https://doi.org/10.5194/egusphere-egu21-12555, 2021.

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