Experimental Study of Produced Fluid Emulsification during Water/Steam Flooding for Heavy Oil Recovery

Abstract

Active substances such as asphaltene and resin in heavy oil tend to absorb on the oil–water interface. Thus, heavy oil and water would easily emulsify into water-in-oil (W/O) emulsion under the shared action of formation porous media. Emulsification of produced fluid during heavy oil recovery is important for accurately calculating the oil recovery. Studies on the properties of produced fluid can effectively forecast the reservoir production dynamics. Therefore, water/steam flooding experiments at different permeabilities, heavy oil viscosity, and varying temperature were performed using long sand-packed tubes. Accordingly, the flooding dynamics, emulsification states, viscosity, droplet size distribution, and oil recovery deviation rate (ORDR) were analyzed. The results show that produced oil is W/O emulsion during water/steam flooding heavy oil. The water content of the produced oil is mainly affected by temperature and can be as high as 30% in the middle and late stages when the temperature is higher than 150 °C. Because the layered stacking structure of asphaltene and resin weakens as temperature increases, they absorb more easily on the oil–water interface. The water content of produced oil the in middle stages is as high as 40% when the temperature is 250 °C, and the ORDR is as high as 50.28%. Furthermore, the water droplet size increases with increase in permeability and temperature, but it is not obviously affected by heavy oil viscosity. The evaporation of light components is significant when the temperature is higher than 150 °C. In particular, the percentages of asphaltene and resin would increase with the evaporation of light components. Thus, W/O emulsion would form more easily during water/steam flooding, and hence, the efficient development of heavy oil would become difficult in the middle and late stages.

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