Sand-carrying thresholds of viscous slickwater: Weissenberg number–based prediction and field application

Abstract

The complex viscoelastic and shear-thinning behavior of slickwater fracturing fluids imposes competing effects on proppant transport, complicating the prediction of sand-carrying capacity and increasing the sand plugging risk. This study quantifies slickwater elasticity over a range of shear rates using the Weissenberg number (Wi) and establishes a fracture-scale shear-rate calculation method to estimate elastic energy at different flow velocities. The results show that: (1) the Wi strongly correlates with sand-carrying capacity, demonstrating its effectiveness in characterizing elastic-dominated transport behavior; (2) fracture experiment identify distinct settling-rate thresholds for slickwater systems with different polymer concentrations; (3) at these thresholds, fluids transporting equivalent proppant volumes exhibit identical elastic energies, indicating a the existence of a critical elastic-energy requirement for stable proppant suspension; (4) elastic-energy thresholds are established for three sand concentrations, allowing rapid prediction of sand-carrying capacity across slickwater systems with different viscosities; and (5) a field construction strategy derived from the predicted operating window is validated through field trials conducted both within and outside this window, with close agreement observed between the predicted and actual proppant-transport performance. This study provides a quantitative and practical framework for optimizing slickwater fracturing operations.