Characterization of interfacial interactions and emulsification properties of bicarbonate solutions and crude oil and the effects of temperature and pressure

An extensive study of fluid/fluid interactions of bicarbonate solutions and crude oil from Danish North Sea has been carried out. Interfacial tension (IFT) measurements, and oil/brine contact tests were conducted. Brine with salinity of 0.05 M was shown to be the optimum salinity in emulsification at basic pH of bicarbonate solution.

ATR-FTIR spectra of oil and formed emulsions were recorded to characterize the nature of the emulsion. Information about the content of polar molecules and the water content of the emulsions was provided by the IR analysis. The emulsion structure and drop size which correspond to the optimum salinity were characterized using cryo-scanning electron microscopy (Cryo-SEM) images.

The emulsion drop size was comparable to carbonate pore size. This suggests that flow diversion by emulsion formation is possible as a mechanism with an impact on oil recovery. In flow diversion mechanism, formed emulsions will plug fractures and bigger pores and redirect the injected brine to the non-flooded zones.

IFT was measured at reservoir pressure (200 bar) and different temperatures (23, 60, 90 and 120 °C). Overall, the change in interfacial tension values in compared to formation water was up to 30% and rarely exceeded that. At each temperature, the IFT has been reduced to the lowest achievable value and no further reduction was observed by increasing the salinity.

Furthermore, an increase in temperature led to additional reduction in IFT for each salinity.