Effects of Oil Saturation and Bedding Orientation on Crack Propagation and Wake Zone in Laminated Tight Sandstone

Abstract

Fracture‐induced deformation and energy dissipation in laminated tight sandstones are strongly influenced by structural anisotropy and fluid saturation. Although the fracture process zone develops ahead of the crack tip during propagation, the wake zone trailing the crack accommodates post‐fracture irreversible deformation but remains largely unquantified. Systematic fracture experiments were conducted on oil‐saturated laminated tight sandstones. A quantitative framework was developed to characterize the crack‐induced wake zone. This framework is based on full‐field displacement and strain measurements obtained using digital image correlation. An automatic crack identification algorithm was first implemented to ensure stable extraction of fracture geometry. Subsequently, a wake zone half‐width was defined and quantified by analysing the spatial distribution of crack opening displacement. This approach enables consistent comparison under different structural and saturation conditions. The wake zone dimensions exhibit a clear dependence on bedding orientation, reflecting the controlling role of bedding in fracture processes. In addition, fluid saturation systematically modifies the development of the wake zone, suggesting a transition towards post‐fracture deformation and energy dissipation. The proposed methodology provides a quantitative basis for characterizing wake zone features and offers insights into fracture dissipation mechanisms in laminated tight sandstones under varying saturation states.