A continuous process to upgrade heavy crude oil for producing more valuable crude feedstock having high API gravity, low asphaltene content, and high middle distillate yield, low sulfur content, low nitrogen content, and low metal co teat without external supply of hydrogen and/or catalyst. Heavy crude oil having substantial amount of asphaltene and heavy components is mixed with highly waxy crude oil having large amount of paraffinic components and water to decompose asphaltene compounds and remove sulfur, nitrogen, and metal containing substances under supercritical conditions. Product has higher API gravity, lower asphaltene content, high middle distillate yield, lower sulfur content, lower nitrogen content, and lower metal content to be suitable for conventional petroleum refining process.
