Experimental Investigation of Foam Stability under Various Salinity Levels, Oil Types, and Surfactant Conditions: Effect of Natural Polymer Lignin

Gas injection is a widely applied enhanced oil recovery (EOR) technique, but its efficiency is often limited by gas channeling and gravity override in high-permeability zones. To address these issues, this study explores the use of natural polymer lignin as a novel foam stabilizer in gas-injected EOR systems. Lignin’s amphiphilic nature enables it to improve foam stability under harsh conditions, including high salinity and oil contamination. Laboratory experiments were conducted using two surfactants (CTAB and SDS), three oil types (heptane, toluene, heptol), and aqueous systems with varying salinity (distilled water and synthetic seawater). Surface tension measurements, static foam generation, and foam stability assessments were performed. Results showed that lignin significantly enhances foam stability, particularly when combined with CTAB. In distilled water, increasing lignin concentration from 100 to 2000 ppm led to a more than threefold increase in foam half-life, from 241 to 801 minutes. Moreover, CTAB–lignin systems showed superior performance compared to SDS or lignin alone, especially under saline and oily conditions. These findings suggest that lignin-enhanced foams are promising, cost-effective, and environmentally friendly candidates for improving gas mobility control in EOR operations, particularly in complex reservoirs.