Numerical simulation of the effect of weak shale bedding on fracture propagation through strata

Abstract

Bedding strength is one of the key factors affecting the propagation of hydraulic fractures through beddings, which is mainly determined by cohesion, internal friction angle and tensile strength. However, there are few researches on this. Therefore, in order to further study the influence mechanism of bedding strength on the propagation of hydraulic fractures through beddings. Based on the three-dimensional block discrete element method, this paper simulated the propagation morphology of hydraulic fractures under different cohesion, tensile strength and internal friction angle. The simulation results show that bedding cohesion has a significant influence on the propagation of hydraulic fractures through beddings. Under low cohesion, hydraulic fractures mainly shows transverse propagation, accompanied by a larger degree of bedding activation, however, at high bonding strength, the permeability of hydraulic fractures is strong, and the propagation is nearly circular. The tensile strength of bedding has no obvious effect on the propagation capacity of hydraulic fracture and can be ignored in practical engineering. The penetration of hydraulic fractures increases with the increase of internal friction angle, and the hydraulic fractures are easy to diffuse along bedding at low internal friction angle.

Keywords

• bedding strength
• hydraulic fracturing
• three-dimensional block discrete element method
• shale
• fracture propagation