Experimental investigation of particle transport and distribution in a vertical nonplanar fracture.

Particle transport in a vertical nonplanar fracture is a typical but poorly understood element in hydraulic fracturing. Particle-fluid flow in a nonplanar fracture with a narrowing width is investigated experimentally by a laboratory-scale slot, and the relevant transport mechanisms are compared with that in the planar slot. The effects of fluid flow rate, particle density, particle size, and particle volume fraction on particle distribution are investigated. The results indicate that the narrowing width complicates the slurry flow and lowers the bed coverage area. The vortex flow appears at the contraction of the cross-section as the bed grows to a threshold height and resuspends more particles further into the slot. An irregular bed with a descending stepped surface is formed due to non-uniform placement. Smaller size sands injected at a high flow rate and a low particle volume fraction build up a smaller bed. Larger and denser particles would reverse the trend. A rational model expressed by four dimensionless numbers is developed by the linear regression method to predict the coverage percentage of the particle bed. The model and experimental results provide directions to quantitatively evaluate the particle transport and distribution in a nonplanar fracture. [Display omitted] • The particle transport in a nonplanar fracture with a narrowing width is investigated by the experiment. • The dimensionless parameters are used to describe the particle distribution in nonplanar fractures. • The irregular bed with a descending stepped surface is smaller than the regular bed in the planar slot. • A correlation is developed for predicting the coverage percentage of the particle bed. [ABSTRACT FROM AUTHOR]