A process for the gasification of carbonaceous materials to produce a high B.T.U. gaseous product is disclosed. The process includes the partial oxidation of a fluid hydrocarbon to produce a gaseous mixture of carbon monoxide and hydrogen, followed by contacting the gaseous mixture with a relatively cool, finely-divided carbonaceous solid material. The resulting gas-solid mixture is then passed along with a carbonaceous feed into a high velocity transfer line reactor furnace, and the solid material is removed from the gas-solid mixture which emerges from the reactor furnace. The present invention is particularly well suited for the hydrogasification of high boiling, carbon-rich feedstocks such as reduced crude oils.