Prats effective well radius

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Prats effective well radius equation

Effective well radius is a radius value at which well is draining the reservoir under the radial flow.

  • For stimulated wells the effective well radius is higher than the wellbore radius.
  • For damaged wells the effective well radius is lower than the wellbore radius.
  • For undamaged wells the effective well radius is equal to the wellbore radius.
It appears that the behavior of vertically fractured reservoirs can be interpreted in terms of simple radial-flow reservoirs of large wellbore.
— Prats, 1961
r_{w_{eff}}=r_w e^{-S}

Skin equation

S = ln \left ( \frac{r_w}{r_{w_{eff}}} \right ) = ln \left ( \frac{2 r_w}{X_f} \right )

Nomenclature

r_{w} = wellbore radius, length
r_{w_{eff}} = effective well radius, length
S = skin factor, dimensionless
X_f = fracture half length, length

References

  1. Prats, M., Hazebroek, P., and Strickler, W.R. 1962. Effect of Vertical Fractures on Reservoir Behavior--Compressible-Fluid Case. SPE J. 2 (2): 87-94.