Investigation of Hydraulic Fracture Propagation Characteristics in the Shale Reservoir With Natural Fractures and Bedding Plane

Abstract

Hydraulic fracturing is the principal technical method about the generation of sophisticated fracture system in shale gas development; there are still significant challenges in enunciating the origination and extension of hydraulic fracture and optimizing design methods about hydraulic fracturing. The manuscript builds a small-scale shale reservoir model that containing randomly complex natural fractures and bedding by means of the continuous–discontinuous element method (CDEM); it provides detailed investigation of the effects including the shale reservoir burial depth along with the fracturing fluid viscosity, and flow rate on the generation and growth of fracture systems. The simulated findings suggest that hydraulic fractures are more likely to be captured by bedding planes and tend to extend along the bedding planes when the burial depth is shallow. The phenomenon of fractures penetrating bedding planes increases obviously under high flow rate conditions, resulting in more branching and interlacing in the vertical direction. The guiding effect of bedding planes on the propagation direction of hydro fractures gradually weakens as the viscosity of the fracturing fluid increases. Increasing the flow velocity of fracturing fluid enlarges outer boundary of hydraulic fracture system, and hydraulic fracture system’s propagation length and aperture grow substantially within the same period of injecting time. The high-viscosity fracturing fluid will lead to relatively single propagation of hydraulic fracture branches that is in favor of forming a single main fracture. This research puts forward a novel perspective for understanding the expansion characteristics of elaborate hydraulic fracture systems and persistent refinement of hydraulic fracturing operations in shale reservoirs.