Dynamics of proppant particle settling within low Reynolds numbers: Roles of particle shape, surface wettability, wall factor, and fluid elasticity

Characterizing proppant settling in fracturing fluids is essential for optimizing hydraulic fracturing operations. However, the dynamics of proppant settling in viscoelastic fluids within low Reynold numbers remain unclear. In this work, we investigate the settling behavior of real proppants in a narrow space filled with viscoelastic partially hydrolyzed polyacrylamide (HPAM) solutions to quantify the effects of proppant shape, surface wettability, fracture walls, and fluid elasticity on settling dynamics. Experimental results indicate wall factors lower than studies in literature and negligible influence of particle surface wettability on settling despite different contact angles between resin-coated and non-coated proppants. Fluid elasticity reduces the drag on proppants exponentially, which supports an observation that making thicker HPAM solutions does not always lead to slower proppant settling. New correlations of drag coefficient and terminal settling velocities are developed to quantify the effects of wall retardation and fluid elasticity on particle settling in viscoelastic fluids. • Wall factors are inferred from measured velocities against Renaud correlation. • Fluid elasticity reduces the drag exponentially regarding relaxation time variation. • Proppant shape and surface wettability show negligible impact on proppant settling. • New correlations of drag coefficient and terminal velocity are developed.