Design of salinity tolerant in alkaline surfactant systems for high salinity reservoirs

Chemical oil recovery from offshore reservoirs which are usually characterised by harsh conditions such as high salinities have remained a source of concern. This study assesses chemical compatibilities alkalis –surfactant systems under salinity and divalent ions (Ca2+ Mg2+). It analysed the synergy between alkali-surfactant slugs crude oil, leading to design an optimal low-cost alkaline- surfactant flooding. Three alkali systems: sodium hydroxide, metaborate ethylene-diamine-tetracetic acid-(EDTA/NaOH) were evaluated with two synthetic brines; one without (soft brine) other containing (hard brine). Compatibility these commercial-grade was based on fluid-fluid interaction. Phase behaviour experiments conducted determine alkali–surfactant compatibility brine. Solutions free precipitation used for interfacial-tension (IFT) phase separation analysis, obtained level readings calculate salinity. Results showed that all compatible soft brine, while hard brine highly controlled pH. Alkali-crude failed produce Type III micro-emulsion; however, addition achieved ultra-low IFT. EDTA/NaOH effectively sequestered like hence increasing solubilisation at higher Comparison both commercial surfactant, alcohol alkoxy sulphate pH exhibited optimum than metaborate. shows ≥ 11 increased above salinity, occurs resulting in reduced recovery.