Determination of Viscosity and Density of Selected Nigerian Crude Oil Fractions

The physical properties of crude oil fractions, particularly viscosity and density, are critical parameters for pipeline transport design, refinery process engineering, and petroleum product characterisation. Nigeria's onshore crude oil fields in the Niger Delta produce oils with varying API gravity and composition depending on reservoir origin. This study determines the dynamic viscosity and density of five crude oil fractions obtained from the Warri Refining and Petrochemical Company in Delta State, South South Nigeria. Viscosity is measured at temperatures of 20, 30, 40, and 50 degrees Celsius using a Cannon-Fenske glass capillary viscometer, and density is determined using a pycnometer and calibrated hydrometer. The Walther viscosity-temperature relationship is fitted to each sample's data. Results indicate dynamic viscosity ranging from 3.2 to 28.7 mPa.s at 20 degrees Celsius across the five fractions, reflecting differences in hydrocarbon chain length distribution. Density values range from 0.821 to 0.872 g per cubic centimetre, corresponding to API gravity indices of 31 to 40 degrees. The heaviest fraction shows a strong viscosity-temperature dependence with a Walther slope coefficient of 3.81. These physical property data are relevant to pipeline flow assurance calculations and support the work of process engineers in Nigeria's downstream petroleum sector. Keywords: crude oil viscosity, density, API gravity, viscometry, Nigeria petroleum