Abstract: The invention involves the demulsification and liquefaction of hydrocarbon based sludges. A demulsifier and a liquefaction agent and methods of using the same are disclosed. In a preferred embodiment, the demulsifier contains a salt of DDBSA, polypropylene glycol, and citrene. In a preferred embodiment, the liquefaction agent contains a glycol ether and sodium silicate. In another preferred embodiment, the liquefaction agent contains a glycol ether and citrene. In preferred practice, the sludge is treated with the liquefaction agent, circulated, treated with the demulsifier, and circulated further. An object of the invention is to provide a hydrocarbon based sludge that is sufficiently liquefied to be pumped and which is sufficiently demulsified to allow the waters, oils, and solids in the sludge to separate.