Flow coupling during three-phase gravity drainage

Area of Science:

• Petroleum Engineering
• Multiphase Flow in Porous Media
• Fluid Dynamics

Background:

• Accurate measurement of three-phase oil relative permeability (k(ro)) is crucial for reservoir simulation and enhanced oil recovery.
• Existing models often assume k(ro) independence from water flow and saturation, which may not hold under certain conditions.
• Unsteady-state experiments are necessary to capture dynamic flow couplings not observable in steady-state measurements.

Purpose of the Study:

• To measure three-phase oil relative permeability (k(ro)) under specific experimental conditions.
• To investigate the dependence of k(ro) on water saturation, oil saturation, and water flow.
• To explore the underlying physical mechanisms responsible for observed flow behaviors and develop a predictive model.

Main Methods:

• Conducted unsteady-state drainage experiments in a 0.8 m water-wet sand pack.
• Focused on scenarios starting from capillary-trapped oil conditions.
• Analyzed the relationship between k(ro), water saturation, oil saturation, and water flow rate.

Main Results:

• Observed a strong dependence of k(ro) on water flow and water saturation when starting from capillary-trapped oil.
• Found a weak dependence of k(ro) on oil saturation, contradicting conventional models.
• Demonstrated that flow coupling between water and oil is more pronounced in three-phase than two-phase flow.

Conclusions:

• Three-phase oil relative permeability is significantly influenced by water flow dynamics and saturation, particularly from trapped oil states.
• The observed phenomena suggest oil transport via moving interfaces (form drag) or momentum transfer (friction drag).
• A proposed friction drag model shows good agreement with the experimental data, offering a new approach to modeling three-phase flow.