Integrated approach and insights into shale gas potential: Geological, petrophysical, geochemical, and geomechanical evaluation of the Khatatba Formation (Western Desert, Egypt)

This study provides a comprehensive assessment of the shale gas potential of the Middle Jurassic Khatatba Formation in the Obaiyed Field, Western Desert, Egypt, by integrating geological, petrophysical, geochemical, and geomechanical datasets into a unified workflow. The multidisciplinary approach allows for the identification of shale gas “sweet spots” and addresses critical operational risks associated with drilling and completion. Petrophysical evaluation indicates heterogeneity, with total porosity ranging from 6–12%, effective porosity between 4–8%, shale volume often exceeding 40% but locally decreasing below 30%, and permeability within 0.01–0.1 mD. Gas storage capacity is enhanced at depths greater than 3800 m, where free gas contents are significant and adsorbed gas reaches 1.5–2.0 cm 3 /g in Total Organic Carbon (TOC)-rich intervals. Geochemical analysis confirms that the Upper Safa Member is thermally mature within the gas window, with TOC averaging ∼4 wt.% and mixed Type II–III kerogens, while traces of CO 2 (0.8–2.0 mol%) and H 2 S (25–80 ppm) raise concerns about casing corrosion and necessitate careful material selection. Geomechanical results reveal brittle intervals with high Young’s modulus and low Poisson’s ratio, fracture gradients ranging from 25–30 MPa/km, and maximum horizontal stress (σHmax) typically 1.2–1.5 times the minimum horizontal stress (σhmin), defining a narrow safe mud weight window. Seismic inversion delineates TOC-rich, low-impedance intervals as optimal drilling targets, while fault-bounded compartments highlight both opportunities for hydrocarbon trapping and risks of reservoir compartmentalization. The integration of reservoir quality (RQ) and completion quality (CQ) with stress and pressure profiles enables optimized well orientation and trajectory planning, particularly recommending horizontal wells perpendicular to σHmax in the lower Upper Safa Member. This integrated evaluation confirms the Upper Safa Member as the most promising shale gas target within the Khatatba Formation and establishes a transferable workflow for unconventional reservoir development worldwide.