Unlocking shale gas potential in the Sembar Formation through multi-analytical assessment and basin modeling, Central Indus Basin, Pakistan

Understanding source-reservoir characteristics is essential for evaluating shale gas potential, yet the Sembar Formation in the Central Indus Basin remains underexplored in this regard, which limits accurate assessment of its hydrocarbon generation potential and regional energy significance. While earlier studies have focused mainly on basic source rock evaluation, a comprehensive geochemical-mineralogical-basin modeling framework has not yet been employed, leaving significant gaps in understanding the formation’s shale gas potential. This study bridges this gap by integrating novel multi-analytical techniques, including organic and inorganic geochemistry, vibrational spectroscopy, microscopy, and basin modeling, to comprehensively assess the shale gas potential of the Sembar Formation. The results reveal total organic carbon values ranging from 0.23 to 1.76 wt%, suggesting poor to good source rock potential, with Type III kerogen indicating gas-prone characteristics further corroborated by vibrational spectroscopy showing aromatic hydrocarbon dominance. Biomarker results indicate that the Sembar shale received mixed organic matter, primarily from higher plants, along with planktonic and bacterial inputs, deposited under open marine-suboxic conditions. Basin modeling results (up to 68% transformation ratio) and vitrinite reflectance values (Ro=1.05–1.16%) confirm late-stage maturity, consistent with gas generation. The combination of high quartz content, favorable clay assemblage, and stratigraphically controlled carbonates yields a high brittleness index (0.77–0.86), indicating strong mechanical competence and reservoir stability, while nanopores and microfractures enhance gas storage capacity. In conclusion, these findings demonstrate that the Sembar shale possesses favorable source-reservoir characteristics for unconventional gas development, underscore its regional energy significance, and highlight the effectiveness of an integrated multi-analytical approach for shale-resource evaluation in underexplored basins.