Desalting Crude Oils

Abstract

The treatment of emulsified crude oils has been a problem for years in thepetroleum industry. Until comparatively recently various methods of settlingwith and without chemicals have been used with indifferent success. Since wellshave been acidized, emulsified crudes have been produced, which addconsiderably to the need for improved methods of treatment. The presence oflarge quantities of salts in the oils from acidized wells has presented severalnew problems to the industry. The use of hydrochloric acid in well treatmentshas caused the formation of sodium, magnesium, and calcium chlorides byinteraction with the dolomitic limestones. These salts dissolve readily in thewater normally present in the oil, and they. are therefore incorporated in theemulsified oil. The crystalline salts have also been found in the oil, prevented from settling by protective films such as asphalt, resins andpetrolatum. In some instances, free hydrochloric acid has been found. The saltsmay be present in crude oil in amounts ranging from a few pounds to over 1000lb. per 1000 bbl. of oil. The transportation of these crude oils through pipe lines has led to erosiveand corrosive effects, which are a tremendous cost to the petroleum industry. During 1937, more than 1,200,000,000 bbl. of crude oil was transported throughpipe lines. Of this quantity approximately 10,000,000 bbl. was water, andconsiderably more than 50,000,000 lb. was salts. If the crude oils were treatedat the producing wells to remove the salts and water, an appreciable savingwould be possible. The treatment would not be difficult, since it has beenfound that these oils are more easily treated at the time they are producedthan after the aging and more stable emulsification that occur before theyreach the refinery. Since great costs are involved in the use of.these saltycrudes at the refinery, treated oils essentially free of salts would naturallycommand a premium. The real added costs lie in refining salt-containing crude oils. Severecorrosion of refinery equipment in both topping and cracking installations hasappeared in many refineries. T.P. 915