Discovery of the Lower-Middle Jurassic high potential source rocks based on the geochemical investigation from the Indus Basin, Pakistan

The Lower to Middle Jurassic sedimentary succession of the Indus Basin, Pakistan represents thick strata of shale, siliciclastic and carbonate rocks. The shale is subjected to the experimental methods of total organic carbon contents (TOC), rock-eval (TM), vitrinite reflectance, and x-ray diffraction with clay mineralogy for identification of high potential source rock. This set of black shale having well-defined kemgen types I and II, an abundance of organic matter >= 2%, HI >= 150 or 200 mg HC/g TOC, T-max <= 465 degrees C, good maturity such as 1.3-2.0 Ro%, thermal alteration index >= 2, and spore color index >= 5, and illite-smectite clay is strong enough (60-80%) to produce hydrocarbon. Furthermore, the stratigraphic thickness is <= 100 m in studied strata in a depth of 3500-4500 m in the Indus Basin feasible for future exploration. The chemical composition of black shale is siliceous mudstone, calcareous mudstone, argillaceous mudstone, and siliceous marlstone. The cross plot of CH versus HI and T max versus HI shows mature types II and I kerogen while the cross plots of TOC versus S-1 + S-2 with TOC versus generative potentials (GP) showing good to high potentials of indigenous hydrocarbons. The plotting of the T-max versus productive index (PI) exhibits that the kerogen mostly lies in the mature zone, having the capacity of oil generation. Besides the geochemical properties, the studied rock is thick and widely disturbed across the Indus Basin deposited under the dysoxic-anoxic setting. Moreover, the Lower to Middle Jurassic strata are correlated with the equivalent stratigraphic formations in India and China for their importance in the regional context.