Abstract-Experimental Study of Hydraulic Fracturing Fracture Propagation in Deep Shale in Southern Sichuan Basin, SW China

ABSTRACT: Due to the complex and strong heterogeneous geomechanics of deep shale gas reservoir in southern Sichuan basin, the hydraulic fracturing results present a significant difference among wells and sections. The uneven fracturing treatment results limits the efficient development of deep shale gas. To study the hydraulic fracture propagation characteristics under the complex geomechanics, true triaxial physical simulation tests were conducted on the 400×400×400mm artificial rock samples. The samples were made under different media characteristics based on the similarity criterion. The sensitivity analysis was carried out, including brittleness, natural fractures and in-situ stress condition. The results show that under the same stress condition, the brittle sample behaves a lower breakdown pressure and a faster propagation rate, while plastic sample generates an appear asymmetric fracture. Natural fracture in plastic sample more easily induced the hydraulic fracture than that in brittle one, the hydraulic fracture can be a bifurcation when it countering the natural fracture. Within the high stress difference, the difference between breakdown pressure and propagation pressure along the fracture direction is larger (about 10MPa), and the fracture initiation and propagation are faster. 1. INTRODUCTION The Sichuan Basin is rich in shale gas resources and is the main position of shale gas development in China (Zou Caineng et al., 2021). At present, a number of shale gas production demonstration zones such as Fuling, Weiyuan and Changning - Shaotong have been built, which has achieved a major breakthrough in shale gas exploration and development (Wang Jian et al., 2023). However, the complex geological structures in Sichuan Basin, such as extensive development of natural fractures and significant differences in horizontal principal stresses, result in difficult fracturing reconstruction, high critical net pressure required for fracture opening, uneven hydraulic fracture propagation, and low complexity (Huang et al,2024; Zang et al.,2022) has become an important factor restricting the efficient development of shale gas in Sichuan Basin. At the same time, reservoir lithology difference, in-situ stress state and natural fracture development have great influence on the migration direction and fracture geometry characteristics in the process of hydraulic fracture propagation (Renshaw et al.,1995; Gao et al,2018; Tan et al.,2018), which directly affects the fracturing effect.