CRUDE PETROLEUM from a producing oil field is stored in lease stock tanks prior to delivery to a pipeline company. The crude oil, although passing through a gas-oil separator and/or emulsion treater, still contains appreciable quantities of hydrocarbon gas. In addition the produced gas may contain large volumes of hydrogen sulfide and carbon dioxide gases.
When the produced crude oil containing both free and solution gases enters the lease storage facility, it is still under line temperature and pressure. The agitation of the oil as it enters the stock tank, coupled with the reduction in pressure within the tank, results in release of gases which rise into the vapor space of the stock tank. When the stock tank oil is withdrawn near the tank bottom, a partial vacuum results in the vapor space of the tank and considerable quantities of oxygen are drawn through the tank vent lines into the...
