Seismic Imaging of Strata Truncating to Base Miocene Unconformity Integrated with Petrophysical Analysis of Mianwali Re-entrant, Pakistan: a Case Study from the Upper Indus Basin of Pakistan

This study aims to delineate the truncating subsurface horizons of the northwestern Indus foreland basin by using seismic imaging. 2D seismic data interpretation identifies the deepening of the basement in the north and west directions. Moreover, the seismic sections extended to the southeast, reveal the Cretaceous-Oligocene successions are missing in the eastern part of the Mianwali Re-entrant area. Flexural subsidence in the northwestern collisional regime has caused the thickening of the sedimentary layers in western regimes as compared to the eastern part. Seismic data revealed that the Precambrian basement rocks are exposed towards the S–E direction in the uplifted Sargodha High. Re-entrant’s boundary faults, i.e., Jehlum, Kalabagh, and Kundal, have the strike-slip movement and are believed to control the arcuate settings of Salt and Trans-Indus Ranges. Cambrian and younger rocks show low reflection time and depth values in the southeast. However, the Triassic, Jurassic, and Paleogene formations truncate to base Miocene unconformity at different shot points of the available seismic sections. Reservoir parameters at different reservoirs are evaluated using well-log data. Petrophysical analysis of the Cambrian and Jurassic formations shows fair to very good effective porosities. Hydrocarbon saturation for Khewra Sandstone is about 54%, while that of Shinawri Formation is 72% from the respective pay zones.