In-situ Stress State of the Shushan Basin, Western Desert, Egypt: Implications for Developing Tight Cretaceous and Paleozoic Reservoirs

The Shushan Basin in Egypt’s Western Desert hosts hydrocarbon-bearing sandstones within the Cretaceous Alam El Bueib and Cambro-Ordovician Shifa formations, representing significant yet underexplored reservoir potential. This study presents a comprehensive geomechanical analysis of the Paleozoic–Mesozoic sequence to characterize the in situ stress state and its implications for drilling and completion strategies. The reservoirs, primarily quartz-rich with micro-mesoporosity, exhibit tight characteristics, with porosity below 10% and permeability under 1 mD and follow a hydrostatic pore pressure gradient (0.43 psi/ft). The geomechanical modeling reveals a dominant strike-slip faulting stress regime (SHmax > Sv > Shmin). Borehole breakout analysis from multi-arm caliper and resistivity image logs indicates a mean maximum horizontal stress azimuth of approximately N160°E. The estimated Shmin and SHmax gradient ranges are 0.8–0.9 psi/ft and 1.1–1.3 psi/ft, respectively. Cretaceous shales were identified as particularly susceptible to mechanical instability when drilled with < 0.55 psi/ft drilling fluid gradient. Analyzing collapse pressure sensitivity to wellbore trajectory shows that the wells deviated towards Shmin azimuth would require a mud gradient 0.12 psi/ft higher than SHmax parallel wells, emphasizing strong azimuthal influence. Additionally, the assessment of solid production indicates that the sand-free drawdown threshold in Paleozoic sandstones is ~ 1000–1200 psi lower compared to the Cretaceous reservoirs. The critical drawdown pressures required to mitigate sanding risks were quantified for various wellbore trajectories and depletion scenarios. Overall, this research provides a geomechanical framework of Shushan Basin, offering practical insights for optimizing drilling operations, mitigating wellbore instability, and improving completion strategies for the development of tight sandstone reservoirs.