Surfactants and enhanced oil recovery
A large number of commercial and some novel Brunel synthesised surfactants have been studied with a view to their potential usefulness for enhanced oil recovery (EOR) application. Ethoxylated phenols and their sulphonated derivatives were given especially high priority. The surfactants were well-characterised in order to understand their EOR potential. High pressure liquid chromatography, mass spectrometry, Raman spectrometry, nuclear magnetic resonance spectrometry and other quantitative techniques were used. Aspects of their behaviour (as single components and as blends with co-surfactants and co-solvents) which have been considered in terms of: (i) phase behaviour with brine and hydrocarbons (ii) adsorption onto various oxide surfaces (iii) interfacial properties such as surface tension, wetting, contact angles and viscosity (iv) stability Three different blends using sulphonated surfactants which: (i) produce a microeinulsion which is stable to high salinity brines over a large temperature range (ii) exhibit low adsorption onto reservoir rock (iii) interfacial tension as low as 10-2mNm-1 have been subsequently optimised. Core flooding tests carried out under reservoir conditions produced an additional 20% of the original-oil-in-place.