The Nen 2 Shale Formation within the Nenjiang Formation of the Daqing Oilfield has frequently encountered casing damage during recent development activities, significantly impeding the stable and efficient progression of the oilfield. This study employs core observations for rock classification, investigates the correlation between rock mineral composition and mechanical strength through rock mechanics experiments, examines the effects of hydration on rock mechanical properties, and systematically analyzes the primary factors and mechanisms influencing casing damage using well-logging curve analysis. The findings indicate that the peak strength and elastic modulus of shale and mudstone are positively correlated with the ratio of feldspar to clay minerals. The maximum variation in elastic modulus between layers in the Nen 2 is 2.1 times, which induces shear stress at the interlayer interface and results in a 2.4-fold stress differential exerted on the casing by the formation. As stress increases, the permeability of shale exhibits a nonlinear decline, with permeability increasing post-failure. Permeability in the vertical bedding direction is consistently lower than that parallel to the bedding, suggesting that the bedding direction is the primary pathway for water intrusion. However, vertical fractures may also become pathways for water intrusion following fracturing. These results enhance our understanding of the geomechanical characteristics of the Nen 2 shale reservoir and clarify the factors contributing to casing damage in this reservoir, offering theoretical support for optimized casing design and damage prevention strategies in the development of the Nen 2 shale reservoir.