Abstract: A method for removing sludge from a petroleum storage tank is based on a two-step approach utilizing solvent extraction to dissolve organic components of the sludge followed by water wash to remove inorganic materials. Sludges contain both organic-based solids (e.g., waxes and asphaltenes) as well as inorganic-based solids (known to exist as salts such as chlorides, carbonates, and oxides). The organic components of the sludge are dissolved using petroleum-based solvent streams that have been identified to possess high solvent power. The dissolved material can then be processed and recovered in the refinery using conventional refining operations. A water wash following removal of the organic materials is effective to remove the inorganic materials that can then be disposed of without the complications of the having to treat the oily organics along with them. A beneficial part of the method includes mixing and heating to improve the dissolution of soluble materials in both steps of the process.