Surfactant injection faces a great challenge due to severe conditions in the reservoir including high salinit y and temperature which results in surfactant precipitation and/or surfactant degradation. Considering the local reservoirs conditions, a surfactant which is stable under harsh conditions, reduce residual oil saturation, and provide viscosity to the water phase is highly desirable. Most of the commercially available surfactants for EOR are anionic in nature that could have very high retention on carbonate rocks.
To overcome the challenges, a variety of gemini cationic and conventional zwitterionic surfactants were synthesized and characterized by NMR (1H and 13C), FTIR and elemental analysis. The solubility tests were conducted for all gemini cationic and conventional zwitterionic surfactants. The heat stability was investigated by putting surfactants in an oven at 90oC for 15 days followed by structural elucidation.
The characterization data exhibited excellent heat stabilities of the surfactants. The NMR (proton and carbon) and FTIR analysis of the before and after aging samples showed no major difference which indicated the excellent heat stability of the surfactants. The solubility tests revealed that the majority of the gemini cationic and conventional zwitterionic surfactant were soluble in water. Surfactants containing carbon-carbon double bond in the hydrophobic tail exhibited good solubility in water.
The tested surfactants revealed excellent solubility and found to be stable in high temperature conditions and have great potential especially in carbonate reservoirs in order to avoid adsorption issues related to anionic surfactants.