Electrofacies and Petrophysical Characterization of the Datta Formation in the Kohat Plateau, Northwest Pakistan
Keywords:
Heterogeneous Rock Analysis (HRA), Principal Component Analysis (PCA), Electrofacies, PetrophysicsAbstract
Understanding reservoir heterogeneity within the Datta Formation remains a key challenge for hydrocarbon exploration and development in the Kohat Plateau, northwestern Pakistan, due to laterally variable sandstone bodies interbedded with shale and limited subsurface control. This study aims to improve reservoir characterization by integrating petrophysical analysis with electrofacies classification to better resolve lithological variability and reservoir quality distribution better.
The study focuses on the Jurassic Datta Formation across the Kohat Plateau and utilizes wireline log data from seven wells distributed throughout the basin. The dataset includes gamma ray (GR), density (DEN), neutron porosity (NPHI), compressional slowness (DTC), and deep resistivity (Deep Res) logs, which collectively capture lithological and fluid-related responses within the formation.
We applied an integrated workflow combining conventional petrophysical evaluation with an unsupervised machine-learning approach. Principal component analysis followed by k-means clustering was implemented using the Heterogeneous Rock Analysis (HRA) module in Techlog to classify electrofacies without predefined lithological constraints.
The analysis identifies six distinct electrofacies ranging from clean, high-quality sandstone reservoirs to tight, non-reservoir siltstone and shale facies. The electrofacies classification was validated using a confusion matrix and accuracy metrics, resulting in an overall model accuracy of 79.5%, indicating reliable discrimination between reservoir and non-reservoir facies. These facies distributions are consistent with observed reservoir behavior across the basin. This study represents the first basin-scale integration of petrophysical analysis with HRA clustering for electrofacies characterization of the Datta Formation in the Kohat Plateau, providing a robust framework for improved reservoir prediction and development planning.
References
Abdi, H., & Williams, L. J. (2010). Principal component analysis. Wiley Interdisciplinary Reviews: Computational Statistics, 2(4), 433–459. https://doi.org/10.1002/wics.101
Ahmad, S., Ali, F., Sayab, M., Ahmad, I., & Hamidullah, S. (1999). Structural geometry of the Himalayan Frontal Thrust Zone: Surghar Range, Pakistan. Journal of Himalayan Earth Sciences, 32(1), 13–23. http://ojs.uop.edu.pk/jhes/article/view/1517
Asquith, G., & Krygowski, D. (2004). Basic well log analysis (2nd ed.). American Association of Petroleum Geologists.
Beck, R. A., Burbank, D. W., Sercombe, W. J., Khan, A. M., & Lawrence, R. D. (1996). Late Cretaceous ophiolite obduction and Paleocene India–Asia collision in the westernmost Himalaya. Geodinamica Acta, 9(2–3), 114–144. https://doi.org/10.1080/09853111.1996.11105281
Bilal, A., Yang, R., Janjuhah, H. T., Mughal, M. S., Li, Y., Kontakiotis, G., & Lenhardt, N. (2023). Microfacies analysis of the Palaeocene Lockhart limestone on the eastern margin of the Upper Indus Basin (Pakistan): Implications for the depositional environment and reservoir characteristics. The Depositional Record, 9(1), 152–173. https://doi.org/10.1002/dep2.222
Catuneanu, O. (2019). Principles of sequence stratigraphy. Elsevier.
Cherana, A., Aliouane, L., Doghmane, M. Z., Ouadfeul, S.-A., & Nabawy, B. S. (2022). Lithofacies discrimination of the Ordovician unconventional gas-bearing tight sandstone reservoirs using a subtractive fuzzy clustering algorithm applied to the well log data: Illizi Basin, the Algerian Sahara. Journal of African Earth Sciences, 196, 104732. https://doi.org/10.1016/j.jafrearsci.2022.104732
Dani, T. M., Khan, M. A., & Kakar, M. A. (1995). Structural style and stratigraphy of the Kohat Basin. Geological Bulletin, University of Peshawar, 28, 39–50.
Davis, J. C. (2018). Electrofacies in reservoir characterization. In B. D. S. Sagar, Q. Cheng, & F. P. Agterberg (Eds.), Handbook of mathematical geosciences. Springer. https://doi.org/10.1007/978-3-319-78999-6_11
Doghmane, M. Z., Ouadfeul, S.-A., Benaissa, Z., & Eladj, S. (2022). Classification of Ordovician tight reservoir facies in Algeria using neuro-fuzzy algorithm. In S.-A. Ouadfeul (Ed.), Artificial intelligence and heuristics for smart energy efficiency in smart cities: Case study: Tipasa, Algeria (pp. 889–895). Springer. https://doi.org/10.1007/978-3-030-92038-8_91
Doveton, J. H. (1994). Geologic log analysis using computer methods (Vol. 2). Published by the American Association of Petroleum Geologists.
Ellis, D. V., & Singer, J. M. (2007). Well logging for earth scientists (2nd ed.). Springer.
Everitt, B. S., Landau, S., Leese, M., & Stahl, D. (2011). Cluster analysis (5th ed.). Wiley.
Fatmi, A. N. (1973). Lithostratigraphic units of the Kohat–Potwar Province, Indus Basin, Pakistan (Geological Survey of Pakistan Memoir No. 10). Geological Survey of Pakistan.
Ghani, H., Ahmad, I., Ahmad, S., Ali, F., & Irum. (2015). Structural evolution of southern Kohat fold and thrust belt, a case study from Karak area, Pakistan. Journal of Himalayan Earth Sciences, 48(2), 1–8. http://ojs.uop.edu.pk/jhes
Guo, Q.-J., Strauss, H., Liu, C.-Q., Zhao, Y.-L., Pi, D.-H., Fu, P.-Q., Zhu, L.-J., & Yang, R.-D. (2005). Carbon and oxygen isotopic composition of Lower to Middle Cambrian sediments at Taijiang, Guizhou Province, China. Geological Magazine, 142(6), 723–733. https://doi.org/10.1017/S0016756805001202
Hartigan, J. A., & Wong, M. A. (1979). A K-means clustering algorithm. Journal of the Royal Statistical Society: Series C (Applied Statistics), 28(1), 100–108. https://doi.org/10.2307/2346830
Hotelling, H. (1933). Analysis of a complex of statistical variables into principal components. Journal of Educational Psychology, 24(6), 417–441 https://doi.org/10.1037/h0071325
Iqbal, S., Jan, I. U., Akhter, M. G., & Bibi, M. (2015). Palaeoenvironmental and sequence stratigraphic analyses of the Jurassic Datta Formation, Salt Range, Pakistan. Journal of Earth System Science, 124(4), 747–766. https://doi.org/10.1007/s12040-015-0572-y
Jain, A. K. (2010). Data clustering: 50 years beyond K-means. Pattern Recognition Letters, 31(8), 651–666. https://doi.org/10.1016/j.patrec.2009.09.011
Jain, A. K., Murty, M. N., & Flynn, P. J. (1999). Data clustering: A review. ACM Computing Surveys, 31(3), 264–323. https://doi.org/10.1145/331499.331504
James, G., Witten, D., Hastie, T., & Tibshirani, R. (2013). An introduction to statistical learning: With applications in R. Springer.
Jolliffe, I. T. (2002). Principal component analysis (2nd ed.). Springer. https://doi.org/10.1007/b98835
Kadri, I. B. (1995). Petroleum geology of Pakistan. Pakistan Petroleum Limited.
Kafayatullah, K., Arif, M., & Shah, M. T. (2006). Petrography of sandstones from the Kamlial and Chinji formations, southwestern Kohat Plateau, NW Pakistan: Implications for source lithology and paleoclimate. Journal of Himalayan Earth Sciences, 39, 1–13. http://ojs.uop.edu.pk/jhes
Kaufman, L., & Rousseeuw, P. J. (1990). Finding groups in data: An introduction to cluster analysis. Wiley. https://doi.org/10.1002/9780470316801
Kazmi, A. H., & Jan, M. Q. (1997). Geology and tectonics of Pakistan. Graphic Publishers.
Khan, N., & Rehman, K. (2019). Petrophysical evaluation and fluid substitution modeling for reservoir depiction of Jurassic Datta Formation in the Chanda oil field, Khyber Pakhtunkhwa, northwest Pakistan. Journal of Petroleum Exploration and Production Technology, 9(1), 159–176. https://doi.org/10.1007/s13202-018-0513-9
Kohavi, R., & Provost, F. (1998). Glossary of terms. Machine Learning, 30(2–3), 271–274. https://doi.org/10.1023/A:1017181826899
Kumar, B., & Kishore, M. (2006). Electrofacies classification—A critical approach. In 6th International Conference and Exposition on Petroleum Geophysics, Kolkata, India (pp. 822–825).
Lee, S. H., Khargoria, A., & Datta-Gupta, A. (2002). Electrofacies characterization and permeability predictions in complex reservoirs. SPE Reservoir Evaluation & Engineering, 5(3), 237–248. https://doi.org/10.2118/78662-PA
MacQueen, J. (1967). Some methods for classification and analysis of multivariate observations. In Proceedings of the Fifth Berkeley Symposium on Mathematical Statistics and Probability (Vol. 1, pp. 281–297). University of California, Berkeley.
Mahmood, M. N., & Guo, B. (2019). An analytical method for optimizing fracture spacing in shale oil reservoirs. SPE Liquids-Rich Basins Conference–North America. Society of Petroleum Engineers. https://doi.org/10.2118/197083-MS
Meissner, C. R., Master, J. M., Rashid, M. A., & Hussain, M. (1974). Stratigraphy of the Kohat Quadrangle, Pakistan (U.S. Geological Survey Professional Paper 716-D). U.S. Geological Survey. https://doi.org/10.3133/pp716D
Miall, A. D. (2010). The geology of fluvial deposits: Sedimentary facies, basin analysis, and petroleum geology. Springer.
Pearson, K. (1901). LIII. On lines and planes of closest fit to systems of points in space. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 2(11), 559–572. https://doi.org/10.1080/14786440109462720
Pivnik, D. A., & Sercombe, W. J. (1993). Compression- and transpression-related deformation in the Kohat Plateau, NW Pakistan. In P. J. Treloar & M. P. Searle (Eds.), Himalayan tectonics (Geological Society, London, Special Publications, Vol. 74, pp. 559–580). Geological Society, London. https://doi.org/10.1144/GSL.SP.1993.074.01.37
Posamentier, H. W., & Walker, R. G. (Eds.). (2006). Facies models revisited (SEPM Special Publication No. 84). Society for Sedimentary Geology. https://doi.org/0.2110/pec.06.84
Radhy, J., & Nasser, M. (2017). Role of cluster analysis in logfacies and depositional environments recognition from well log response for Mishrif Formation in southeast Iraq. International Journal of Engineering and Advanced Research, 3. https://doi.org/10.25125/engineering-journal-IJOER-DEC-2017-5
Reading, H. G., & Collinson, J. D. (1996). Clastic sedimentary environments. Blackwell Science.
Rider, M. H. (1996). The geological interpretation of well logs (2nd ed.). Gulf Publishing.
Rojas, L. J., Tveritnev, A., & Pinillos, C. E. (2020). A multidisciplinary approach for rock typing characterization in a highly heterogeneous carbonate reservoir in Abu Dhabi, UAE [Poster presentation]. 2020 AAPG Middle East Region Geoscience Technology Workshop, 3rd Edition: Carbonate Reservoirs of the Middle East, Abu Dhabi, United Arab Emirates.
Rousseeuw, P. J. (1987). Silhouettes: A graphical aid to the interpretation and validation of cluster analysis. Journal of Computational and Applied Mathematics, 20, 53–65. https://doi.org/10.1016/0377-0427(87)90125-7
Schlumberger. (1989). Log interpretation principles/applications. Schlumberger Wireline & Testing.
Serra, O. (1984–1986). Fundamentals of well-log interpretation (P. Westaway & H. Abbott, Trans.; Vols. 1–2). Elsevier.
Serra, O., & Abbott, H. T. (1982). The contribution of logging data to sedimentology and stratigraphy. SPE Journal, 22(1), 117–131. https://doi.org/10.2118/9270-PA
Shah, S. M. I. (2009). Stratigraphy of Pakistan (Geological Survey of Pakistan Memoirs No. 22). Geological Survey of Pakistan.
Tiab, D., & Donaldson, E. C. (2015). Petrophysics: Theory and practice of measuring reservoir rock and fluid transport properties (3rd ed.). Gulf Professional Publishing.
Willis, B. (2013). Heterogeneous Rock Analysis (HRA) technical notes. Schlumberger.
Wandrey, C. J., Law, B. E., & Shah, H. A. (2004). Patala-Nammal composite total petroleum system, Kohat-Potwar geologic province, Pakistan (U.S. Geological Survey Bulletin 2208-B). U.S. Geological Survey. https://doi.org/10.3133/b2208B
Yeats, R. S., & Thakur, V. C. (2008). Active faulting south of the Himalayan front: Establishing a new plate boundary. Tectonophysics, 453(1–4), 63–73. https://doi.org/10.1016/j.tecto.2007.06.017
