Alkoxy Groups of Sulfonated Natural Oil-Based Surfactant to Reduce Oil-Water Interfacial Tension for Chemical Flooding

Palm oil-based surfactant such as methyl ester sulfonates (MES) has been studied in laboratory scale as well as in field trials for enhanced oil recovery (EOR) technology due to its abundance as a raw material. However, optimization of the molecular structure of MES is required to obtain a uniquely tailor-made surfactant for a specific fluid reservoir characteristic. In the present study, MES was developed by inserting alkoxy groups between hydrophobic tail and hydrophilic sulfonates to attain ultralow oil-water interfacial tension (IFT) as well as to improve surfactant solubility in formation water. The effect of alkoxylation on reducing IFT as the main role of the surfactant was evaluated through IFT measurement. The EOR analysis including compatibility, phase behaviour, thermal stability and filtration test were also investigated to screen the ability of the alkoxy sulfonate (AES) surfactant to be used as a chemical for chemical flooding. The results showed that the presence of the alkoxy group in sulfonated surfactant decreased the IFT of oil water to as low as 0.003 dyne/cm and stable at reservoir temperature (60 degrees C) until 1 month. The alkoxylation also improved the solubilization of surfactant in brine associated with the ability of alkoxy group to achieve a smoother transition in the polarity at the interface. A filtration ratio of AES at 0.2-0.5% was less than 1.2, indicating that an AES injection will not plug oil mobilization in the reservoir pore throat. This study showed that optimization of palm oil-based sulfonated surfactant by alkoxilation improves the compatibility and ability of surfactant to obtain ultralow IFT which has potential for chemical injection application to recover oil production.