Investigation on the Propagation Mechanisms of a Hydraulic Fracture in Glutenite Reservoirs Using DEM

The geometry heterogeneity induced by embedded gravel can cause severe stress heterogeneity and strength heterogeneity in glutenite reservoirs, and subsequently affect the initiation and propagation of hydraulic fractures. Since the discrete element method (DEM) can accurately describe the inter-particle interactions, the macromechanical behavior of glutenite specimen can be preciously represented by DEM. Therefore, the initiation and propagation mechanisms of hydraulic fractures were investigated using a coupling seepage-DEM approach, the terminal fracture morphologies of hydraulic fractures were determined, and the effects of stress differences, permeability, and gravel strength were studied. The results show that the initiation and propagation of hydraulic fractures are significantly influenced by embedded gravel. In addition, the stress heterogeneity and strength heterogeneity induced by the gravel embedded near the wellbore increase local initiation points, causing a complicated fracture network nearby. Moreover, due to the effect of local stress heterogeneity, gravel strength, and energy concentration near the fracture tip, four interactions of attraction, deflection, penetration, and termination between propagating fractures and encountering gravel were observed.

Automated summary

The presence of embedded gravel induces heterogeneity in stress and strength in glutenite reservoirs, affecting the initiation and propagation of hydraulic fractures. Using a coupled seepage-DEM approach, this study investigates the mechanisms of fracture initiation and propagation, determines the terminal fracture morphologies, and studies the effects of stress differences, permeability, and gravel strength. The results show that the initiation and propagation of hydraulic fractures are significantly influenced by embedded gravel. The stress and strength heterogeneity near the wellbore increase the complexity of the fracture network, and interactions between propagating fractures and encountering gravel are observed.