Treatment for upgrading heavy crude oil

A method for upgrading heavy crude oil, wherein said method comprises applying, to the heavy crude oil, a yeast-based composition comprising a fermentation broth in which a Wickerhamomyces anomalus or Starmerella bombicola yeast was cultivated and a sophorolipid biosurfactant, wherein the sophorolipid biosurfactant is present in the fermentation broth and/or is added to the composition and/or is applied to the heavy crude oil separately from the yeast-based composition,

• wherein the fermentation broth does not comprise live yeast cells, and, further comprising applying an ionic liquid in a concentration of 1% to 5% by weight to the heavy crude oil, wherein the ionic liquid is selected from ethyl ammonium nitrate and glycerol magnesium sulfate heptahydrate,
• and wherein upgrading the heavy crude oil comprises increasing the API gravity of the heavy crude oil and/or reducing the impurities content of the heavy crude oil, wherein the impurities are selected from heavy metals, sulfur, nitrogen, ash, olefins, aromatics, naphthenes and asphaltenes.