Abstract:
The Punjab Platform in Pakistan's Central Indus sub-basin faces challenges in unlocking significant hydrocarbon reserves due to variability in source rock properties and uncertainty in mapping hydrocarbon migration pathways. In this study, seismic and geochemistry data were utilized for source rock characterization and hydrocarbon migration pathways mapping. Geochemistry techniques involving rock eval pyrolysis, organic petrography and basin modeling were performed for source rock evaluation and mapping of hydrocarbon migration pathways. The kerogen type was determined by using the Van Krevelen diagram (modified) and the hydrogen index (HI) versus oxygen index (OI) plot determines that the Cretaceous age (Chichali Formation) in Bahu-01, Nandpur- 01, and Zakria-01 wells has kerogen type III. Total organic content (TOC, wt.%) is measured using two unique approaches: direct laboratory analysis based on core data of 34 samples by organic geochemistry and an indirect technique employing stochastic poststack seismic inversion on 2D seismic data. Both techniques yielded TOC values, indicating fair to good source rock richness. Maturity estimation from organic petrography and seismic inversion reveals that the Bahu-01, Panjpir-01, and Nandpur-01 wells have average TOC values below 0.50, indicating immature source rock. However, the average TOC value for the Zakria-01 well is 0.63, confirming maturity and putting it in the oil window, with peak generation occurring during the Eocene age. 2D basin modeling results shows the Chichali Formation in the Sulaiman Foredeep area has a (%Ro) range of 1 to 1.5, representing source rock maturity in the late oil to wet gas window. In most western parts (Sulaiman Fold Belt), the %Ro ranges from 1 to 1.3, representing source rock maturity in the wet gas window. However, the eastern side (Punjab Platform), where three producing fields were present, shows the (%Ro) ranges from 0.4 to 0.48%. The 3D hydrocarbon generation map in Sulaiman Foredeep reveals that the entrance to the early oil window occurs between 65 and 50 Ma, with the main oil window occurring from 65 to 35 Ma. The central part of the study area enters the main all window between 50 and 25 Ma, with early oil windows between 15 to 20 Ma, and late oil windows between 10 Ma. The eastern part remained barren and did not contribute to the hydrocarbon's bulk generation potential. The study introduces novel lateral long path migration pathways in a region using an integrated approach including source rock richness, maturity, ID, 2D basin modeling and 3D hydrocarbon charge modeling. The DHI’s confirms the presence of hydrocarbon particularity gas and authenticates our work about the establishment ofvii migration pathways. It has addressed a previously unresolved issue and is contributing to successful hydrocarbon exploration. It will also help in the mitigation of risks associated with hydrocarbon exploration in other basins worldwide
