Comparative flow behavior of oil sludge and crude oils from algerian storage tanks

Abstract

This study investigates the flow behavior of tank bottom sludge and two crude oil samples by analyzing the variation of viscosity and shear stress with shear rate and temperature. The flow curves reveal that all samples exhibit non-Newtonian, shear-thinning behavior characterized by a distinct yield stress, particularly prominent in the sludge due to its high content of heavy fractions such as asphaltenes, resins, and solid particulates. Viscosity and shear stress consistently decrease with increasing temperature, a result of the thermal disruption of intermolecular forces and breakdown of microstructural networks. At low shear rates, sludge displays more pronounced shear-thinning behavior than crude oils, while at high shear rates, all samples approach Newtonian flow regimes due to molecular alignment and structural degradation. Model fitting shows the Herschel-Bulkley model best describes the sludge's rheology, whereas the Casson model better fits the crude oils under specific temperature conditions. Temperature sensitivity analysis (10–40 °C) indicates that crude oils experience greater viscosity reduction than sludge, with crude 1 showing the highest response due to its thermally labile composition. Yield stress also diminishes with temperature, reflecting the weakening of internal structural rigidity. These findings underscore the critical influence of composition and temperature on the flow properties of petroleum-derived fluids, with implications for pipeline transport and sludge management