Evaluation of shale gas reservoirs in complex structural enclosures: A case study from Patala Formation in the Kohat-Potwar Plateau, Pakistan

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Date
2021
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Journal of Petroleum Science and Engineering
Abstract
Breakthroughs in shale gas exploration and production technology in China point to a possible solution to Pakistan’s current energy crises. In this study, we evaluate the shale gas prospects in the Kohat-Potwar Plateau of Pakistan by establishing an integrated approach involving the analysis of fundamental elastic and petrophysical properties, Rock-Eval pyrolysis, and the sealing mechanism of shale. Detailed geochemical and petrophysical evaluation of the Patala Formation in the Kohat-Potwar Plateau indicates the good potential for shale gas with the following characteristics similar to the Longmaxi shale of Sichuan Basin China, i.e., (i) complex structural types sandwiched by tight limestone strata with low porosity (less than 3%), ultra-low permeability, high density, and large thickness which provides strong sealing capacity for gas preservation and enrichment; (ii) multiphase tectonic evolution of Patala Formation allowed various slippage processes to develop fractures and enhance the porosity and permeability; (iii) high organic matter content and thermal maturation stage (TOC >2%, 416–445 ◦C); (iv) high brittle minerals content (e.g., calcite and dolomite > 40%); and (v) large formation thickness (>30 m) at shallow burial depth < 2500 m. This study emphasizes the critical role of the sealing mechanism in shale gas reservoirs. Furthermore, the results suggest that the evaluation and development of shale gas potential using petrophysical and geochemical analysis may be inadequate. Further scrutiny of the roof and floor of reservoirs’ efficient sealing capacities is essential to understand the extent of shale gas preservation and enrichment. The study results provide valuable insights for identifying the sweet spots and preservation condition of shale gas in the Kohat-Potwar Plateau of Pakistan.
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This article is published in Journal of Petroleum Science and Engineering 198 (2021) 108225; https://doi.org/10.1016/j.petrol.2020.108225
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Journal of Petroleum Science and Engineering 198 (2021) 108225; https://doi.org/10.1016/j.petrol.2020.108225
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