Magnesium is encountered when seawater is used as makeup water. It has also been encountered as magnesium water flows. Magnesium has similar effects as calcium on mud properties such as increased flow properties and fluid loss.
Treatment - Magnesium can be precipitated with caustic soda as insoluble magnesium hydroxide Mg(OH)2. One-half pound of caustic per barrel of mud will precipitate approximately 430 mg/L of magnesium. Most of the magnesium ion will be precipitated when pH is increased to 10.0. Additional filtrate control agents, deflocculants and causticizing materials will be required to restore drilling fluid properties after magnesium contamination. In the case of massive magnesium contamination, it is impractical
to treat it out; therefore, options are: (1) to attempt to maintain a low pH system with Mg++ ion present, or (2) switch to a magnesium tolerant mud such as oil mud.
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