Suspension of proppants in hydraulic fracturing applications can be strongly affected by the cross-sectional shapes and lengths of the fibers present in the wellbore treatment compositions. For instance, it has been observed that crimped cellulose ester fibers with a trilobal cross-section and an optimized length can provide enhanced suspension of proppants in aqueous fracturing fluids. Furthermore, the present invention demonstrates that non-round cellulose ester fibers can provide superior proppant suspension properties relative to polylactic acid fibers with a round cross-section.