(535c) Fluoro- Vs Hydrocarbon Surfactants: Synthesis and Application in Enhanced Oil Recovery

Hydrocarbon-based surfactants show high surface tension and high critical micelle concentration (cmc). Moreover, hydrocarbon-based surfactants decompose at high temperatures in oilfield reservoirs and also face stability issues when encountering monovalent and divalent reservoir ions. The harsh environment of oilfield reservoirs causes surfactant degradation and minimizes their ability in lowering surface/interfacial tension and changing the wettability of reservoir rocks.

To address the stability issues related to hydrocarbon-based surfactants, fluorosurfactants were synthesized by a one-step reaction, which was confirmed by NMR, FTIR, and ESI-MS analysis. The heat stability and water solubility tests were performed by Thermal Gravimetric Analysis (TGA) and aging methods. The interfacial tension was measured using the spinning drop method. The cmc and surface tension at cmc were calculated by a force tensiometer (Biolin Scientific). The rheological parameters were identified with the aid of a discovery hybrid rheometer (DHR-3).

The in-house synthesized fluorosurfactants were found to be soluble in water and TGA results exhibited a degradation temperature above 100 ^oC which is superior to real oilfield temperature (≥90^oC). In addition, the aging technique revealed no precipitation by visual observation after putting the surfactant samples in the oven at 90 ^oC for 30 days and it was further confirmed by chemical structure analysis of fluorosurfactant using NMR and FTIR techniques. The surface/interface properties of the fluorosurfactants were comparable to or higher than industrially applied surfactants. Rheological results showed that the storage modulus was decreased by enhancing the surfactant concentration at a lower rate of shear and frequency due to polymer interaction and charge screening.

The in-house synthesized fluro surfactants displayed excellent thermal stability and water solubility and established huge potential in severe conditions of oilfield reservoirs.