Preventing Iron Sulfide from Precipitation in Immersion Electric Pumps as a Result of Hydrogen-Sulfide Corrosion of Oil-Well Equipment

The study shows that, in oil wells, it is the moist hydrogen-sulfide corrosion of the casing string (especially of its longest section—from the electric immersion-pump's intake port to the well collar), the products of which fall immediately to the pump, thus irreversibly clogging it with iron sulfides. Two ways of preventing the clogs are proposed: (1) regularly and completely cleaning the inner surface of the string from the corrosion products and (2) creating a filter-accumulator in the form of a sufficiently tall layer of thickened oil, which floats above the dynamic level of the oil-pool liquid between the casing and tubing strings. The layer is opportunately pumped out together with sulfide–carbonate sediments fallen in it, and replaced with another one. Both methods were successfully applied to working oil wells in Bashkortostan.