A Combined IFT–TGA
Assessment of Anionic Surfactants for Chemical EOR Applications
Barman Joyshree, Saikia Bhaskar Jyoti, Bora Gauri Sankar and Gogoi Gaurav
Res. J. Chem. Environ.; Vol. 30(1); 64-70;
doi: https://doi.org/10.25303/301rjce064070; (2026)
Abstract
This study presents a comparative evaluation of five anionic surfactants: Sodium
Dodecyl Sulfate (SDS), Alpha-Olefin Sulfonate (AOS), Linear Alkylbenzene Sulfonate
(LAS), Petroleum Sulfonates (PS) and Dioctyl Sulfosuccinate Sodium Salt (AOT) with
respect to their interfacial tension (IFT) reduction efficiency and thermal stability,
under conditions representative of Enhanced Oil Recovery (EOR). IFT measurements
were performed using a spinning drop tensiometer at 70 °C in synthetic brine (6000
ppm NaCl), simulating saline reservoir environments. All surfactants showed a decrease
in IFT with increasing concentration until reaching their Critical Micelle Concentration
(CMC). AOT achieved the lowest IFT (6.9 × 10⁻² mN/m at 0.3 w/v%), followed by PS,
SDS, AOS and LAS. Thermogravimetric analysis (TGA) further revealed distinct decomposition
behaviours linked to surfactant molecular structures. SDS and AOT displayed sharp,
clean degradation with negligible residues, indicating minimal risk of solid deposition.
PS exhibited the broadest decomposition profile with significant residue (~10–15%),
reflecting higher stability but a tendency toward char formation.
AOS and LAS showed intermediate behaviour with minor residues. By integrating IFT
and TGA insights. The study identifies AOT as the most promising candidate for high-efficiency
EOR due to its superior interfacial activity and clean thermal breakdown, while
PS offers robust salinity tolerance and stability despite fouling risks. SDS and
AOS represent economical alternatives for moderate conditions, whereas LAS holds
potential as a co-surfactant in blended formulations. These findings provide a framework
for the rational selection of surfactant systems tailored to reservoir-specific
conditions in chemical EOR applications.
