ADVANCES IN RESEARCH OF HYDRAULIC FRACTURES IN UNCONSOLIDATED SANDS

The typical features of hydraulic fracturing of unconsolidated sands are the large number of branch fractures and micro cracks,and a certain dullness of crack tips and some shear zones. This paper analyzes the influence of the tensile shear on the fracture morphology (initiation, reorientation and dilatation). Some experimental study of hydraulic fracturing of the unconsolidated sands indicates that the filtration process is mainly affected by the fracture tip area, and the filtration commonly occurs before the crack propagation. The confining stress around the fracture tip is often the leading parameters to influence the fracture initiation and the crack opening, and the crack characteristics are integrated effects of the stress, the permeability and the flow state, which explains the hydraulic fracture characteristics.