The effect of hydrogen sulphide on ammonium bisulphite when used as an oxygen scavenger in aqueous solutions

The effectiveness of ammonium bisulphite (ABS) as oxygen scavenger and the behaviour of H2S in brine/ABS solutions are examined. Deionised water, 1 wt.% NaCl and 3.5 wt.% NaCl with different ABS concentrations are bubbled with H2S gas, while the dissolved oxygen, sulphide, EH and pH are measured. With the exception of natural seawater, ABS concentration much greater than 100 ppmw (parts per million by weight) is needed to completely scavenge dissolved oxygen in all the solutions considered. The reaction between ABS and H2S leads to increase in sulphide. The implications of the results for environment assisted cracking of oil and gas production tubings are discussed.

► 100 ppm ABS or less does not fully scavenge dissolved oxygen in NaCl solutions.
► At low pH, the sulphide level increased with increasing ABS concentration.
► There were more sulphides in deionised water with ABS compared to NaCl solutions.
► Material qualification test programs of well production tubing should include ABS.
► Sulphite-free oxygen scavengers should be considered for use in oil and gas wells.