PetroChina Tarim Oilfield has established China’s largest ultra-deep hydrocarbon production base, with over 180 wells drilled to depths exceeding 6,000 m. Ultra-deep reservoirs in this region are typically subjected to intense tectonic compression, resulting in elevated present-day in-situ stress, abnormal overpressure, and pronounced heterogeneity. Conventional evaluation methods prove inadequate for characterizing inter-well variations in reservoir quality and productivity within these ultra-deep clastic sequences, leading to challenges in optimal well placement and inconsistent stimulation performance. To address these limitations, this study presents a geomechanics-based sweet spot prediction methodology tailored for ultra-deep clastic reservoirs, and further investigates the coupling mechanisms among shear slip potential, natural fracture propagation, and reservoir quality. The findings are as follows: (a) In-situ stress state, rock strength, and the development and effectiveness of natural fractures constitute critical controls on reservoir quality and productivity, particularly in fractured ultra-deep reservoirs. (b) Fractures exhibiting high shear slip tendency and favorable propagation characteristics are defined as possessing elevated fracture effectiveness. (c) Based on three-dimensional geomechanical modeling and integrated analysis, sweet spots are delineated as intervals characterized by moderate rock strength, relatively low in-situ stress magnitude, high natural fracture density, and enhanced fracture effectiveness. This approach improves the predictability of ultra-deep reservoir performance and demonstrates a methodology for evaluating “strongly altered” ultra-deep reservoirs, thereby advancing the integration of intelligent geology-engineering workflows in deep hydrocarbon exploration.