Oxygen Scavenger
Oxygen dissolved in water can cause corrosion in the drill string. Oxygen scavenger reacts and neutralizes the dissolved oxygen to reduces corrosive effects of the fluid on metal components of downhole equipment. When fluid returns to surface, it again comes in contact with the atmosphere and begins to pick up oxygen, thus reducing effective concentration of scavenger. Hence oxygen scavenger level is measured and continuously injected at the pump suction. Common oxygen scavengers have sulfite (SO3–2) or bisulfite (HSO3–) ions, which combine with dissolved oxygen in the fluid system to form sulfate (SO4–2). Nickel or cobalt based catalysts are used for this reaction.