Metal naphthenate is removed from a crude hydrocarbon mixture by a process. The process includes mixing the crude hydrocarbon mixture comprising metal naphthenate with an acid in the presence of water, wherein the acid converts the metal naphthenate to naphthenic acid and metal salt; allowing the metal salt to partition into a water phase; and separating the crude heavy hydrocarbon mixture comprising naphthenic acid and the water phase comprising the metal salt.