Contribution of Anisotropic Features of an Organic-Rich Shale Gas Reservoir on Hydraulic Fracturing

Abstract

Shale gas reservoir plays a significant part in the global energy scene and serves as a valuable addition to the natural gas resource base. The main challenge in the exploration and extraction of shale gas is the effective application of hydraulic fracturing. Shale exhibits a characteristic anisotropy due to the presence of a bedding structure. Shale rock’s anisotropic features have a significant effect on the development of intricate fracture networks, the stability of wellbore joints, and the spreading of hydraulic fractures. This paper provides a brief overview of earlier research on the relationship between hydraulic fracturing in shale reservoirs and the anisotropic mechanical features. This paper emphasizes the issues surrounding anisotropic mechanical behavior under laboratory tests and numerical simulation models, with a focus on the detailed discussion of shale brittleness evaluation based on mechanical characteristics. Other issues are raised, including how the bedding plane affects the failure pattern, crack growth, and hydraulic fracturing failure strength. The results indicate that the anisotropy behavior of organic-rich shale is primarily caused by the combination of kerogen and clay distribution. A weak relationship between the P-wave anisotropies and quartz contents is found, and it appears that there is no linear relationship between the P-wave anisotropy and clay minerals. Additionally, the P-wave anisotropy exhibited a positive correlation with the kerogen and clay combination. The findings indicate that the initiation and spread of hydraulic fractures in anisotropic shale are influenced by the interplay between the stress state and rock fabric. This broadens our understanding of the basic behavior of fractures and could help develop effective hydraulic fracture approaches for real-world use.