The shape and size of sand grains, as well as the saturating fluid, influence the mechanical properties of unconsolidated sands and need to be considered in frac-pack design. These mechanical properties of unconsolidated properties of unconsolidated sands play an important role in determining the geometry of frac-pack treatments. Stress-strain curves obtained for unconsolidated sands at elevated stresses show highly nonlinear hysteretic behavior. The impact of these findings on frac-pack design can be significant. The nonlinear elastic properties of unconsolidated sand can give rise to some unique features in the pressure response and in the fracture geometry that may not be observed in hard rocks. This article focuses on the impact of mechanical properties of poorly consolidated and unconsolidated sands on the geometry of frac packs. The paper discusses frac packs, mechanical properties (Young‘s modulus, shear failure) and effective treatments