Numerical simulation study on the effects and mechanisms of bedding plane mechanical parameters on hydraulic fracture propagation in shale

Abstract

[Objective] The mechanical parameters of bedding planes have a significant influence on the initiation and propagation of hydraulic fractures in shale. However, current research on the effects and mechanisms of bedding plane inclination angle and strength on fractures remains limited. [Methods] ABAQUS finite element software was utilized in this study to conduct two-dimensional numerical simulations by adopting the global zero-thickness cohesive element. Python programming was employed to extract the mechanical parameters of hydraulic fractures, and the effects of bedding plane inclination angle, bedding plane strength, and in-situ stress difference on fracture propagation were analyzed. [Results] The result indicated that:(1) the bedding plane inclination angle had a significant impact on the propagation patterns of hydraulic fractures. Within the range of 0° to 90°, when the bedding plane inclination angle was 45°, the fracture length was the longest, and the number of fractures was the largest.(2) Weaker bedding plane strength result ed in more significant effects of the bedding plane on the propagation path of hydraulic fractures, making it easier for narrow-width shear fractures to develop along the bedding plane.(3) When the difference in stress increased from 2 MPa to 8 MPa, the deflection effect of hydraulic fracturing fractures became more prominent, meaning that the fractures were more likely to propagate in the direction of the major principal stress.(4) Compared with bedding plane strength and in-situ stress difference, the bedding plane inclination angle had a more significant impact on hydraulic fractures.(5) Based on the interaction between hydraulic fractures and bedding plane, fracture patterns were divided into four types: penetration, deflection, bifurcation, and capture. As the bedding plane inclination angle increased, hydraulic fractures transitioned from penetration to bifurcation or deflection. [Conclusion] Among the three influencing factors, namely bedding plane inclination angle, bedding plane strength, and in-situ stress difference, bedding plane inclination angle has the most significant effect on the hydraulic fractures.

Keywords

hydraulic fracture / bedding plane / shale / numerical simulation / influencing factors