The core function of iron ion stabilizers is to prevent the formation of precipitates by iron ions through chemical reactions or to maintain the dispersed state of already formed precipitates. Their mechanisms of action are diverse and synergistic, mainly including chelation, reduction, dispersion, and coordination. Different mechanisms play a role in different stages of iron ion conversion.

（1） Chelating effect: forming stable complexes to prevent precipitation formation

This is currently the most widely used and effective mechanism of action. The chelating agents in iron ion stabilizers (such as EDTA, citric acid, amino polycarboxylate compounds) contain multiple coordinating atoms (such as O, N, S) in their molecular structure, which can form stable chelates with Fe ² ⁺ and Fe ³ ⁺ in a cyclic structure. This chelate has extremely high stability and is not easily decomposed under a wide pH range (usually pH 1-12) and high temperature conditions, thereby avoiding the formation of precipitates by the combination of iron ions with anions (such as OH ⁻, S ² ⁻, CO ∝ ² ⁻) in formation water.

（2） Reduction effect: maintain ferrous form, delay oxidative hydrolysis

Reduced iron ion stabilizers reduce oxidized Fe ³ ⁺ to Fe ² ⁺ by providing electrons, while inhibiting the oxidation of Fe ² ⁺, thereby delaying the hydrolysis and precipitation process of iron ions. Common reducing agents include sodium sulfite, sodium thiosulfate, ascorbic acid, hydroxylamine compounds, etc. For example, the reaction between sodium sulfite and Fe ³ ⁺ is: 2Fe ³ ⁺+SO3 ² ⁻+H ₂ O → 2Fe ² ⁺+SO3 ² ⁻+2H ⁺. By reducing Fe ³ ⁺ to Fe ² ⁺, which is more stable in a neutral and slightly acidic environment, the stability period of iron ions is extended.

This type of stabilizer is particularly suitable for hypoxic or low oxygen environments (such as deep oil reservoirs), and the cost is relatively low. However, the disadvantage is that the reduction effect is easily affected by temperature and pH values, and the action time is short under aerobic conditions. It needs to be used in combination with other types of stabilizers to improve the effect.

（3） Dispersing effect: prevents particle aggregation and maintains a suspended state

Dispersed iron ion stabilizers are mostly anionic surfactants (such as sulfonic acid salts, carboxylic acid salts) or polymers (such as polyacrylic acid, polymaleic anhydride). Their mechanism of action is to adsorb on the surface of iron ion precipitation particles, and through electrostatic repulsion or steric hindrance effect, prevent particles from aggregating and growing together, keeping them in a small dispersed state and avoiding deposition on reservoir pores or equipment surfaces.

（4） Complexation: Weak interaction assists in stabilization

Complex type iron ion stabilizers form relatively loose complexes with iron ions (rather than the cyclic structure of chelates), mainly through intermolecular coordination bonds or hydrogen bonds to achieve stabilization. Common types include alcohol amines, polyhydroxy compounds (such as ethylene glycol, glycerol), etc. This type of stabilizer has low cost and good compatibility, and can inhibit iron ion precipitation to a certain extent, but its stability is weak. It is usually used as an auxiliary ingredient in combination with chelating and reducing stabilizers to reduce overall costs.