Reservoir attributes of a hydrocarbon-prone sandstone complex: case of the Pab Formation (Late Cretaceous) of Southwest Pakistan

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  • Muhammad Umar, Department of Earth Sciences, COMSATS Institute of Information Technology, University of Balochistan, Pakistan
  • Abdul Salam Khan, Centre of Excellence in Mineralogy, University of Balochstan, Quetta, Pakistan
  • Gilbert Kelling, School of Physical and Geographical Sciences, University of Keele, Storbritannien
  • Henrik Friis
  • Akhtar Muhammad Kassi, Department of Geology, University of Balochistan, Quetta, Pakistan
The link between reservoir architecture and parameters such as stratigraphy, facies associations, texture, diagenesis of sandstones is investigated and tested in the late Cretaceous Pab Formation in southwestern region of Pakistan. Excellent stratigraphic trapping conditions prevail in the region, where the Formation rests on the proven source rocks like Mughal Kot and Sembar formations and underlies the impervious dark grey, black, greenish grey and olive grey mudstone/shale of lower part of Paleocene Rani Kot Group. The facies and facies associations of the formation are significant to predict its reservoir characteristics; for instance thick to very thick, vertically connected and laterally continuous sand packets hold high average porosities in fluviodeltaic (12.75%), delta shelf (11.08%), shoreface (10.43%) and submarine slope channels-fan lobe (9.82%) facies associations. Whereas deeper shelf and basin floor sand bear low porosities and ranges from 4.39% to 6.41%. Porosity has direct relation to grain size and sorting e.g., coarse to pebbly and moderate to well sorted sands are more porous than finer ones.
Diagenetic investigations of Pab sand reveal that intense mechanical compaction and cementation impart negative affect on reservoir quality and reduced primary porosity, whereas, dissolution of feldspar and volcanic lithics produced secondary porosity during later stages. Sand-shale ratios of measured sections are also compared. The section with high sand refers high porosity e.g., in sections 1, 2, 5, 6, 7, 11, 13 and 14. But higher shale imparts negative impact on reservoir characteristics of the sandstone for example in sections 8, 9, 19 and 20.
TidsskriftArabian Journal of Geosciences
Sider (fra-til)1-15
StatusUdgivet - jan. 2016


  • Porosity, Sandstone, Facies associations, Diagenesis, Stratigraphic Traps, Texture

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