Effect of ionic strength on crude emulsification and EOR potential of micellar flood for oil recovery applications in high saline environment

Micellar flooding is one of the chemical oil recovery techniques in which micelle action emulsifies the crude oil to be mobilized in form of emulsion from a subsurface porous media. However, the subsurface conditions such as high ionic strength and temperature are challenges to the successful use of micellar flood owing to the deterioration of micelle action suggesting no crude emulsification. The ionic compounds dissociate into different ions that may further affect micelle action via loss in viscosity and pressure drop, increased water cut, and mobility contrast between micellar flood and displaced oil. Thus, investigation leading to the successful use of micellar flood, context to crude emulsion, in extreme salinity and temperature is vital to extend the use of chemical methods in new reservoirs. In this work, a typical surfactant sodium dodecyl sulfate (SDS) solution with critical micelle concentration (0.8 wt%) was tested to emulsify a fresh crude oil in the presence of varying ionic strength (0-4 wt%, NaCl/CaCl2 and temperature (40-98 °C). The efficacy of SDS micelles to produce crude emulsion significantly reduced with increasing salt concentration as reported through microscopic, rheological, and flooding experiments, particularly for divalent salt (CaCl2) than monovalent salt (NaCl). The increase in temperature (>40 °C) further curtailed the growth of crude emulsion, mainly due to enhanced droplet coalescence; thus the use of micellar flood is critical in a reservoir enriched with high salinity and high temperature. Salinity effect on emulsion viscosity is reported through rheological measurements. The study highlighted important aspects of surfactant flooding and is a forward step towards the use of SDS based micellar flood at complex reservoir conditions.