Multidimensional geophysical insights into hydrocarbon prospectivity in structurally complex fold-and-thrust belt system
摘要
Hydrocarbon reservoirs within structurally complex fold-and-thrust belt (FTB) systems present significant challenges for exploration and characterization due to complex tectonic deformation and stress regimes. This study integrates multidimensional geophysical approaches, including seismo-stratigraphic, petrophysical, and rock-physical analyses to assess hydrocarbon prospectivity within the eastern Potwar fold-and-thrust belt, a region shaped by the Indo-Eurasian Plate collision. Our findings reveal that compressional tectonics have driven the formation of thrust-faulted anticlines, out-of-sequence thrusts, and duplex structures, which act as effective hydrocarbon traps. Three-dimensional fault system modelling highlights the critical fault offsets in F1 (~800 m) and F2 (~600 m), identified as major barriers or conduits for hydrocarbon migration. Lithological discrimination cross-plots show that clean sands, with neutron porosity of 0.2–0.3 v/v and bulk density of 2.0–2.2 g/cm3, represent the primary hydrocarbon storage units in the Middle Eocene Sakessar Formation, while cemented sandstones exhibit lower reservoir quality. Rock-physical parameters including significant reductions in density (from ~2.4 to ~1.9 g/cm3), P-wave velocity (from ~2100 to ~1300 m/sec), S-wave velocity (from ~1400 to ~800 m/sec), and Poisson’s ratio (from ~0.33 to ~0.23), confirm hydrocarbon presence in the Middle Eocene Sakessar Formation across multiple wells. Petrophysical analysis indicates effective 15–25% porosities in deeper sections of wells R-4 and H-1, with minimal hydrocarbon displacement and low water saturation (Sw < 20%), identifying these zones as prime extraction targets. This integrated geophysical framework provides a template for hydrocarbon exploration in structurally complex FTBs, thus improving exploration outcomes and resource extraction efficiency.