Thermal Stability Studies of Modified Bio-Based Surfactants for Enhanced Oil Recovery

Abstract Natural surfactants have gained global attention due to their cost-effectiveness, biodegradability, and eco-friendly nature. They have been proven to increase oil recovery factors by 10 – 30% depending on the reservoir properties by reducing the interfacial tension. Research has shown that modifying these bio-based surfactants improves their phase behaviour and optimal performance making them less sensitive to higher temperatures, salinities, and divalent-ion concentrations and thus becoming a sustainable substitute to synthetic surfactants. In this study, cashew nutshell liquid (CNSL), a natural surfactant, was chemically modified using three different organic compounds namely triethanolamine, diethanolamine, and sulphonic acid that contain both hydroxyl (- OH) and amine (-NH2) functional groups. The extracted CNSL was divided into three portions for preparation of the derivatives (CNSL-TA2, CNSL-DA2, and CNSL-DA1S). The three CNSL- based modified surfactant solutions were characterized using Fourier-Transform-Spectrophotometer (FTIR) to evaluate their chemical compositions. Thermal stability to ascertain their temperature tolerance was analyzed using Thermogravimetric/ Differential Thermal Analyzer (TGA-DTA). The FTIR spectrum showed new peaks in the derivatives indicating the formation of new functional groups. Calcination temperatures of 582 °C, 562 °C, and 475 °C were obtained for CNSL-DA2, CNSL-DAISx, and CNSL- TA2, respectively, showing their high-temperature stability. This study affirms the suitability of CNSL-based surfactants in high-temperature reservoirs.