Understanding the phase separation behaviour of microemulsions for enhanced oil recovery processes

winsorcourtesy of DataPhysicis

Microemulsion mixtures are commonly used for enhanced oil recovery (EOR) processes due to their high crude oil extraction efficiency. Generally, such mixtures consist of a thermodynamically stable dispersion of crude oil, surfactant, and water or brine. The phase behaviour of the mixture changes from Winsor I to Winsor II by the way of Winsor III when adjusting temperature, salinity, and pressure. The Winsor III state is the most desirable during the EOR process. The dispersion stability analysis system MultiScan MS 20 from DataPhysics Instruments (Fig. 2) is a compact and versatile measuring device for the optical stability and aging analysis of a variety of multi-phase dispersions. The phase behaviour of a crude oil, surfactant, and water mixture will be presented in this application note

 winsor2In order to extract crude oil from increasingly difficult-to-access reservoirs, a multitude of new extraction methods have been developed for enhanced oil recovery (EOR) processes. A very successful and popular technique is based on the recovery of crude oil using a water-surfactant-mixture. A common classification of such mixtures into three different types was established by P. A. Winsor[1] (see Fig. 1). In a Winsor I mixture, oil droplets are emulsified in the water phase. In a Winsor II mixture, water droplets are emulsified inside the oil phase. Finally, in a Winsor III mixture, a bicontinous phase of a network of water and oil is stabilised by surfactants.

All three types are thermodynamically stable. By adjusting the temperature and salinity of the water phase the system alternates between the three different types. For enhanced oil recovery processes, the Winsor III phase is the most desirable, as it has the lowest interfacial tension (10−2…10−4 mN/m) and the surfactants are used most efficiently. Hence, the phase behaviour is extensively researched to find the right surfactants, salinity and temperature to generate ideal extraction conditions[2][3][4].

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