Enhanced oil recovery using the ionic liquid trihexyl(tetradecyl)phosphonium chloride: phase behaviour and properties

With a decrease in world oil reserves and a higher demand for petroleum and its derived products, the effective exploitation of oil reservoirs has become increasingly important. Enhanced oil recovery (EOR) assisted by surfactants is an effective method for recovering the oil from reservoirs that have lost their drive after the application of primary and secondary recovery methods. This research is aimed at showing the suitability of several ionic liquids as effective replacements for conventional surfactants in EOR. The reservoir fluid has been modelled as a ternary system of water (pure water or aqueous solution of NaCl) plus the ionic liquid trihexyl(tetradecyl) phosphonium chloride plus dodecane. Determination of its liquid-liquid phase equilibrium indicates the formation of a Winsor type III system, with a triphasic region and adjacent biphasic regions. The interfacial tensions in the system corroborate the ability of the ionic liquid to act as a surface active agent, as desirable for its use in an EOR process. A relevant transport property such as viscosity, in addition to density, has been experimentally measured for the equilibrium phases.