Lignosulfonates can improve their performance in oilfield applications through chemical modification, physical modification, and composite modification methods, especially in terms of drilling fluid stability, tertiary oil recovery and displacement efficiency, and temperature and salt resistance. Among them, chemical modification is currently the most effective and widely used technological path.

1、 Chemical modification: Introducing functional groups to enhance interfacial activity
By introducing or transforming specific functional groups on lignin molecules, their surface activity, water solubility, and temperature resistance can be significantly enhanced.
Sulfonation and sulfomethylation
Introducing sulfonic acid groups (- SO3H) into alkaline lignin improves water solubility and anion charge density, enhancing its dispersibility to cement particles or clay.
The sulfomethylation reaction can graft - CH ₂ SO3H groups onto the aromatic ring, further enhancing its stability in high mineralization environments.
Alkylation and ethoxylation
By reacting epoxyethane or epoxypropane with phenolic hydroxyl groups, propoxylated lignosulfonates are generated, giving them a better hydrophilic oleophilic balance (HLB value) and significantly reducing the interfacial tension between oil and water to the order of 10 ⁻ mN/m.
The modified product can still maintain ultra-low interfacial tension and strong resistance to divalent ions in 1% NaCl and Ca ² ⁺ solutions.
Mannich reaction (amine methylation)
Under the action of formaldehyde and amines, alkylamine groups are introduced adjacent to the phenolic hydroxyl group to generate nitrogen-containing cationic structures, enhancing their adsorption capacity and flocculation performance on sandstone surfaces, suitable for oily wastewater treatment.
The decolorization rate of the modified product can reach 70%, and it can be used as an efficient flocculant for oilfield wastewater treatment.
Oxidation modification
Using air, oxygen, or ozone to oxidize lignosulfonates converts methoxy groups to phenolic hydroxyl groups, partially oxidizes - CH3 to - COOH, increases carboxyl content, thereby enhancing chelating metal ion ability and antioxidant properties.
The product of ozone oxidation has been proven to be an efficient sacrificial agent for tertiary oil recovery, which can reduce the adsorption loss of main surfactants by more than 60%.