Abstract
For about a century, steam injection has been widely used as the most popular thermal recovery method for heavy-oil in sandstone reservoirs. In order to achieve higher recovery efficiency, which corresponds to the lowest possible value of residual oil saturation and economic success of steam injection projects, an accurate laboratory measurement of the interfacial tension between steam and heavy-oil is essential. However, laboratory investigation and visualization of the effects of steam injection on the interfacial tension between heavy-oil and steam as a function of saturation temperature and pressure is not well documented in the literature. The objective of this study is to investigate the influences of the two main factors which affect the interfacial tension of heavy-oil and steam namely saturation pressure and temperature. An optical cell, which was fitted with a goniometer system and a procedure to generate steam for the measurement of interfacial tension have been used. The difference between the density of heavy-oil and steam, which was used for pendant drop measurements, was calculated at specific temperature and pressure conditions using Katz’s method. Meanwhile, the density of steam was obtained from an international steam table. The interfacial tension of heavy-oil/steam was measured in small intervals, ranging from 115 to 181 Celsius and 25 to 150 pounds per square inch. The results show that the interfacial tension decreases when the saturation temperature and pressure increases. This finding might be useful as an important reference for understanding and visualization the mechanism of interfacial tension during steam injection.
Highlights
Injection of steam into a heavy-oil sandstone reservoir has become an important and successful oil recovery process in the last few decades because this method is capable of enhancing the oil production by reducing its viscosity and residual oil saturation in the swept zones of the reservoirs
The objective of this study is to investigate the influences of the two main factors which affect the interfacial tension of heavy-oil and steam namely saturation pressure and temperature
The findings demonstrated by these results may provide a good indicator of the relationships between heavy-oil/steam interfacial tension, saturation pressure, and saturation temperature under reservoir conditions
Summary
Injection of steam into a heavy-oil sandstone reservoir has become an important and successful oil recovery process in the last few decades because this method is capable of enhancing the oil production by reducing its viscosity and residual oil saturation in the swept zones of the reservoirs. This lower oil saturation, in turn, is related to the interfacial tension between the displacing fluid and the oil, which approaches zero. Interfacial tension exists when there are two immiscible fluids (gas-liquid or liquid-liquid), which are in contact with a few large-diameter molecules It is normally measured in dynes/cm (Donaldson & Alam, 2008). The interfacial tension between the displacing and the displaced fluids in the reservoir is of importance for understanding the oil recovery mechanism (Guo & Schechter, 1997), and it might affect the efficiency of the oil recovery process
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