The present invention is directed to the upgrading of heavy petroleum oils of high viscosity and low API gravity that are typically not suitable for pipelining without the use of diluents. The method comprises introducing a particulate heat carrier into an up-flow reactor, introducing the feedstock at a location above the entry of the particulate heat carrier, allowing the heavy hydrocarbon feedstock to interact with the heat carrier for a short time, separating the vapors of the product stream from the particulate heat carrier and liquid and byproduct solid matter, collecting a gaseous and liquid product mixture comprising a mixture of a light fraction and a heavy fraction from the product stream, and using a vacuum tower to separate the light fraction as a substantially bottomless product and the heavy fraction from the product mixture.