<p>Wellbore stability in horizontal drilling through unconsolidated sandstone is often mischaracterized using shale-based elastic criteria, leading to overly conservative mud weight design and increased lost circulation risk. This study presents an integrated, decision-driven workflow for mud weight optimization that combines analytical screening, laboratory-derived strength characterization, and large-deformation numerical simulation. The approach accounts for confinement-dependent strength mobilization and plastic stress redistribution around the wellbore. A deformation-controlled stability criterion limiting plastic deformation to 2–4% of the borehole diameter is established and calibrated using three field case studies from the Gulf of America. Results demonstrate that traditional elastic-based models overpredict collapse pressure, whereas the proposed workflow enables more accurate and operationally efficient mud weight selection. The methodology provides a practical framework for improving drilling safety, reducing non-productive time, and minimizing lost circulation in weak, poorly consolidated sand reservoirs.</p>