Gasification of oil sludge (OS) from crude oil refinery and biomass was investigated to evaluate hydrogen production and its potential use in diesel oil hydrodesulphurization process. Gasification process was studied by Aspen Hysys (R) tools, considering different kinetic model for main OS compounds. Air and superheated steam mixtures as gasifying agents were simulated. Gasification parameters like: temperature, syngas chemical composition and gas yield were evaluated. Results showed OS thermal conversion needs a working temperature above 1300 degrees C to ensure a high conversion (>90%) of OS compounds. Thermal energy requirement for gasification was estimated between 0.80 and 1.25 kWh/kg OS, considering equivalence air (ER) and steam/oil sludge (SOS) ratio between 0.25-0.37 and 0.2-1.5 kg steam/kg OS, respectively. The gas yield was 2.28 Nm(3)/kg OS, with a H-2 content close to 25 mol%, for a H-2 potential production about 1.84 Nm(3) H-2/kg OS; nevertheless, when OS and biomass mixtures are used, hydrogen production increases to 3.51 Nm(3) H-2/kg OS, meaning 37% of H-2 (from natural gas) required for diesel oil hydrodesulphurization could be replaced, becoming an added value technological alternative for OS waste conversion as a source of H-2, inducing a considerable reduction of greenhouse gases and non-renewables resources. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.