One problem in the modern oil refining industry is associated with involvement of unconventional oil stock in the processing: heavy high-viscosity crude oils and native bitumens. Flexibility in processing heavy oil stock, an increase in the yield of light distillates, and an improvement in their quality is achieved by the combined use of thermal and catalytic processes. Gasification of oil residues is a promising process that makes it possible to obtain syngas suitable for producing synthetic oil, hydrogen, petrochemicals, electric power, or steam. In this paper, we analyze the advantages of the gasification process. We consider existing technologies for gasification of heavy oil stock and the major types of gasifiers.