DEM simulation of injection-induced micro-cracks behaviors in the heterogeneous glutenite by fluid–solid coupling

The fracture and mechanics response during fracturing simulation for the heterogeneous glutenite is crucial for reservoir stimulation. In this work, a non-overlapping algorithm for the generation of non-concave gravels is proposed to reproduce the heterogeneous glutenite models in the DEM. Based on heterogeneous glutenite models, the effect of gravel size distribution, gravel cementation strength and stress difference on micro-cracking response during injection were investigated. The micro-cracking mechanism and geological application of heterogeneous glutenite were discussed. The results show that the increasing of gravel size distribution and gravel cementation strength leads to an increase in breakdown pressure in hydraulic fracturing, with a decrease in stress difference. In terms of the interaction mechanism, the increase in gravel size distribution leads to a change from deflection, penetration to termination when cracks encounter the gravel, while gravel cementation strength is penetration to deflection, with penetration being dominated in the stress difference effect. It is mainly due to the uncoordinated deformation between the gravel and the matrix, the inter-gravel becomes the preferred direction of micro-cracks initiation and propagation, leading to the evolution of the interaction mechanism. The research results may improve understanding of the hydrocarbon exploitation for unconventional glutenite reservoirs.