Sodium Sulfite - An Oxygen Scavenger for Drilling Fluids

Sodium Sulfite

Sodium Sulfite – Catalyzed is an inorganic compound with the chemical formula Na₂SO₃. It is also known as Salt Cake. Sodium Sulfite is primarily used as an oxygen scavenger in water-based oil drilling fluid systems.

Sodium sulfite has a white/ pale yellow appearance and is odorless. It is soluble in water and is catalyzed using a cobaltous compound.

Sodium Sulfite increases the lifespan of organic polymers. It achieves this by eliminating the conditions that encourage their thermal degradation. It saves companies money as it reduces the amount of use of these polymers.

As an oxygen scavenger, Sodium Sulfite is added continually until the residual sulfite (SO3) concentration in the mud filtrate reaches or exceeds the levels required. After that, this level can be sustained with daily treatments. The amounts required will depend on the severity of the dissolved oxygen content in the drilling mud.

Sodium Sulphate is used as a drilling mud additive to assist in borehole stability while drilling through evaporated beds and stringers such as anhydrite. The Sodium Sulphate reduces the anhydrite solubility, thus decreasing the hole enlargement through evaporation.

Sodium Sulfite can be used in some brine muds and completion fluids to reduce corrosion resulting from dissolved oxygen. During the enhanced oil recovery process (EOR), Sodium Sulfite can increase specific polymers’ stability at high temperatures.

Sodium sulfite exhibits bleaching, de-sulfurizing, and dechlorinating activities

Preparation & Procedures

Sodium Sulfite can quickly breakdown. It is usually added at a concentration of one to two sacks to a barrel of water. After mixing, the mixture should be covered with an appropriate cover to reduce the amount of oxygen from the air that the mixture might absorb. It should be added to the drilling fluid system with an injection pump.

Those working with Sodium Sulfite should wear appropriate Personal Protective Equipment, including dust masks and eye protection while mixing chemical products. Always try to avoid skin contact and do not inhale dust or allow contact with eyes.