Over time, the bottom of oil tanks accumulates hydrocarbons that are processed and
recycled for the refining process. Sludge causes various issues in the tanks, such as
lessening of storage capacity and custody transfer issues. Sludge also contains
valuable hydrocarbons that are extracted through various methods. When tanks are
cleaned, sludge is removed from the bottom using several methods, such as
mechanical method, chemical method, and automated systems.