Iron control additives

Iron from the wellbore or iron-containing minerals in the formation can react with acid systems, and acid spending can cause the precipitation of ferric hydroxide, formed from ferric iron ions, which occurs at a pH above 3.2. Furthermore, reactions between acids, ferric iron and asphaltene in crude can cause sludge, which can plug the formation and is generally difficult to remove.

Ferrous hydroxide precipitate does not occur until a pH of more than 7.7 is reached, therefore is not generally a concern in acidizing treatments. Iron control additives work to reduce ferric iron to ferrous iron, or chelating agents can be used to keep ferric iron in a soluble form, reducing precipitation.