Characterization of Doba–Chad heavy crude oil in relation with the feasibility of pipeline transportation

A heavy crude oil was characterized in view of the recent commercial exploitation of Doba oilfield in landlocked Chad from where the crude oil is extracted and expected to be routed to the Atlantic shore through pipeline transportation. The elemental composition of Doba feedstocks is 86.25% C, 12.10% H, 0.25% N, 0.14% S and 1.16% O. Atmospheric distillation indicated an initial boiling point at 85 °C, a 10 vol% fraction distilling before 250 °C and an onset of crude thermal cracking at 300 °C. Crude API gravity is 18.8° API, corresponding to a specific gravity of 0.94 at 15.6 °C. The Doba crude oil was found to exhibit non-elastic purely viscous Newtonian behavior over the temperature range typical of crude transportation by pipeline. The crude was fractionated into 97.4% maltenes (n-pentane solubles), 1.8% asphaltenes (n-pentane insolubles), and 0.1% toluene insolubles. The maltenes were subsequently split into four sub-fractions: 45.0±1.2% saturates (MF1), 11.0±0.3% mono and diaromatics (MF2), 26.8±1.2% polyaromatics (MF3), and 12.8±0.8% polars (MF4). FT-IR characterization and proton nuclear magnetic resonance identification of the maltenic and asphaltenic fractions provided evidence of the chemical nature of the different fractions. The high values of the kinematic viscosity of crude oil (184.4cSt at 50 °C) and deasphalted crude oil (152.4cSt at 50 °C) suggest that partially upgrading the oil would be necessary to comply with the viscosity specifications recommended for crude transportation by pipeline.