NOVELTY - Petroleum residua is converted to methane comprises preheating feedstock to 300-800 degreesF; injecting preheated feedstock into reaction vessel set at 1100-1440degreesF and pressure between 300-1000 psig; withdrawing from reactor a gaseous product mixture; recovering methane from gaseous product mixture; and recovering and recycling hydrogen and carbon monoxide to fluidizing gas mixture.    USE - For converting petroleum residue to methane.    ADVANTAGE - The invention provides improved mechanism of contacting feed with catalyst that reduces catalyst usage by more than 95% and eliminates the need for catalyst recovery, mechanism of significantly reducing the effects of gas back mixing, and controls the size distribution of particulate solids.    DETAILED DESCRIPTION - Conversion of petroleum residua to methane comprises preheating petroleum residue feedstock to temperature between 300-800degreesF; injecting preheated feedstock into reaction vessel maintained at temperature between 1100-1440degreesF and pressure between 300-1000 psig; withdrawing from reactor a gaseous product mixture including unreacted steam, methane, carbon dioxide, hydrogen, carbon monoxide, hydrogen sulfide, or ammonia; recovering methane from gaseous product mixture; and recovering and recycling hydrogen and carbon monoxide to fluidizing gas mixture. The reaction vessel contains fluidized solid particles having (mass%) petroleum coke (more than 50), alkali metal (more than 30 but less than 50), inorganic constituents (less than 10), steam (more than 50), hydrogen (more than 20 and less than 40), and carbon monoxide (more than 3 and less than 20). The alkali metal is potassium, rubidium, and/or cesium. The gaseous mixture is preheated to temperature in excess of 1300degreesF. The mass flow rate of steam is maintained between 1.8-2.0 times of the mass flow rate of injected preheated feedstock. The hourly mass flow rate is injected preheated feedstock is maintained between 0.3-0.6 times the mass of alkali metal.    DESCRIPTION OF DRAWING(S) - The figure is a schematic diagram showing the key features of the gasifier configuration.    Riser (1)    Lower stage (2)    Upper stage (3)    Standpipes (6, 8)    Inlet (13)    Cyclone separators (14, 17)    Pipe dipleg (15)    Jet ejector (20)