In oilfield development, accumulation of large amounts of aging oil is inevitable. In this paper, we study the properties of aging oil and consider the reasons for its accumulation. It has been shown that dehydration of this oil by only a chemical or an electrostatic method is inefficient. Combining these two methods provides a degree of demulsification for which the water content in the oil and the oil content in the water meet the industrial standard. We consider the details of operation of an electrostatic dehydrator in processing aging oil having high solids and iron contents and high emulsion stability. We select the optimal conditions and design an industrial process for dehydration of aging oil.