Impact of mechanical stratigraphy on fracture growth and propagation

Mechanical stratigraphy plays an important role in controlling the nucleation, propagation, and development of fractures. The fracture development pattern and development mode were defined in this study via a detailed description. Fracture growth and evolution in bedded rocks were numerically simulated. The results show that fracture growth and propagation are controlled by the mechanical layer. Fractures are divided into bed-confined fractures and throughgoing fractures based on their spatial configuration with the mechanical layer. Fractures preferentially nucleate and expand in the mechanical layer and terminate at mechanical contact. After that, new fractures are generated between two adjacent fractures. No new fractures are further developed when stress reaches a certain value, indicating a saturation state. Finally, throughgoing fractures are developed. Under the same stress field, the bed-confined fracture density is positively correlated with Young's modulus of the mechanical layer and is negatively correlated with its thickness. Bed-confined fractures can extend to another mechanical layer to develop throughgoing fractures only under significant stress fields or at mechanical contact with small thickness or minor difference in mechanical properties. Exploring the impact of mechanical stratigraphy on fracture development and propagation in bedded rocks is of great significance to investigate the fracture distribution in hydrocarbon reservoirs.