Study of polymer-surfactant interactions for chemical enhanced oil recovery in carbonate reservoir

The global demand for oil has increased while the number of newly discovered oil reservoirs has decreased. Only one third of the oil in the existing oil fields is economically recoverable with primary and secondary recovery methods. The objective of this work is to study and investigate the interactions between polymer and fluoro-surfactants for their use in enhanced oil recovery applications in carbonate reservoirs. The rheological properties of surfactant-polymer solutions are studied. Fluoro-surfactant FS-61 showed relatively small effect on both the viscosity and the elasticity of the polymer solution while surfactant FS-50 showed no effect. Salts caused major reduction in the polymer viscosity. Both fluoro-surfactants showed good thermal stability at temperature higher than 150°C during short and long period tests. Adsorption experiments showed that sulfate ions in brine have major adsorption on the precipitated calcium carbonate. Surfactant FS-50 showed low adsorption density. Fluoro-surfactants showed slightly high interfacial tension and ultralow IFT values were measured when co-surfactants were added. Phase behavior experiments showed the inability of fluoro-surfactants in forming microemulsions. Core flooding experiment was performed for one SP solution of 0.25 wt% HPAM and 0.1 wt% of FS-50 at 90°C. After brine flooding, oil recovery was 44% and it was improved to 86.5% after SP flooding.