Lithofacies, paleoenvironments and sequence stratigraphic modelling of the Wargal Limestone: Implication for reservoir characterization in the Salt Range, northwest, Pakistan
Keywords:
Wargal limestone; Sequence stratigraphy; Permian; Salt Range; Hydrocarbon potential.Abstract
In this paper a detailed stratigraphic analysis of the Middle to Late Permian Wargal Limestone in the Western Salt Range area of the Potwar Basin in north Pakistan is presented. The outcrop data and microfacies analysis suggested that deposition of the Wargal Limestone occurred in the inner shelf to middle shelf-lagoon setting. A regional sequence stratigraphic model of the study unit, with a particular emphasis on the diagenetic fabric of different microfacies has been developed. In this study four, third order depositional sequences (1-4) are recognized. These sequences constituted three Transgressive Systems Tracts (TST 1-3) and four Regressive Systems Tract (RST 1-4). Based on the facies criteria a relative sea level curve is constructed and a comparison with the global sea level curves is made. The relative sea level fall at the 259.6 Ma and 254 Ma in the study area have a global signature, while the 263 Ma fall might be related to the interplay of the local tectonics and sediment supply. The synergy of the diagenetic fabric, results of the XRD, porosity/permeability analysis revealed that best hydrocarbon reservoir qualities exists in the dolomite facies in the middle and upper part of the study unit. The overall hydrocarbon reservoir potential of the Wargal Limestone is moderate to high.
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