Summary
The two-century-old Young’s equation has been widely used in petroleum
engineering to depict the reservoir wettability in terms of contact angle,
which is a function of surface free energies of the system. For
solid/liquid/vapor (S/L/V) systems, Young's equation has been modified in the
recent literature to include a line-tension term. This modification was sought
to accommodate the imbalance of intermolecular forces experienced by the
three-phase confluence zone. Also, Young's equation does not account for the
vertical component of liquid/vapor surface tension. The present study aims to
experimentally investigate the applicability of the line-tension-based
modification of Young’s equation to solid/liquid/liquid (rock/oil/brine)
(S/L/L) systems of interest to the petroleum industry.
Both the ambient- and reservoir-condition optical cells were used, with
stock-tank and live oil, respectively, to determine the drop-size dependence of
dynamic contact angle subtended by the oil/brine interface with the rock
surface. The experimental data were correlated with the modified Young's
equation to determine the magnitude of line tension for different
rock/oil/brine systems. To the best of our knowledge, this is the first attempt
to apply the modified Young's equation to rock/oil/brine systems and to measure
line tension for a rock/live-crude-oil/brine system at reservoir conditions of
pressure and temperature.
The measured line tension for S/L/L systems, while being positive and of the
same order of magnitude as in S/L/V systems, correlates well with the
water-advancing contact angle and the adhesion number, a ratio of adhesion
force to capillary force. This experimental study indicates that the extent of
deviation from Young's equation exhibited by rock/oil/brine systems may be
directly related to the rock/oil adhesion interaction. This study reinforces
the need to include the rock/oil adhesion force in our consideration of
rock/fluid interactions, wettability, and their impact on enhanced-oil-recovery
(EOR)/improved-oil-recovery (IOR) processes.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
12 February 2008
- Meeting paper published:
20 April 2008
- Revised manuscript received:
23 December 2008
- Manuscript approved:
26 April 2009
- Published online:
28 October 2009
- Version of record:
28 October 2009
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