Mobility Ratio

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Brief

Mobility Ratio determines the relative rate of one fluid to another (etc. water to oil).

 M \le 1 oil is dominant flowing phase, stable flow.
 M > 1 water preferentially flows in the reservoir, unstable flow, fingering.

Equation

 M = \frac{k_w/ \mu_w}{k_o/ \mu_o}=\frac{k_{rw}/ \mu_w}{k_{ro}/ \mu_o}=\frac{q_w B_w}{q_o B_o}

where[1]

 \mu_o = oil viscosity, cP
 \mu_w = water viscosity, cP
 B_o = oil formation volume factor, m3/m3
 B_w = water formation volume factor, m3/m3
 k_{rw} = relative water phase permeability, function of the phase saturation, fraction
 k_o = oil phase permeability, function of the phase saturation, fraction
 k_o = relative oil phase permeability, function of the phase saturation, mD
 k_w = water phase permeability, function of the phase saturation, mD
 q_o = oil rate, cc/sec
 q_w = water rate, cc/sec

Related definitions

Dimensionless injected pore volume:

 W_{iD} = \frac{W_i * B_{wi}}{PV} = \frac{W_i * B_{wi}}{A * h * \phi}

Injected movable pore volume:

 MOPV_{inj} = \frac{W_i * B_{wi}}{MOPV} = \frac{W_i * B_{wi}}{A * h * \phi *(1-S_{wc}-S_{orw})}

where

 S_{wc} = Connate water saturation, fraction
 S_{orw} = Residual oil saturation to water, fraction

See Also

References

  1. Wolcott, Don (2009). Applied Waterflood Field DevelopmentPaid subscription required. Houston: Energy Tribune Publishing Inc.