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INPUT   DATA

Title

Oil column thickness		ft
Perforated interval		ft
GOC to perf. top		ft
Wellbore radius		ft
Drainage radius		ft
Permeability		mD
Oil relative permeability
Oil density		lb/ft3
Gas density		lb/ft3
Water density		lb/ft3
Formation volume factor
Oil Viscosity		cp

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OUTPUT   VARIABLES

Critical Oil Flow Rate	STB/day
♦  Meyer-Garder's Method

Optimal Perforation Placement	ft
♦  GOC to top of Perf.

Combined Gas & Water Coning In A Vertical Oil Well

For an isotropic reservoir with a gas-cap above, a water-zone below, and the perforated interval somewhere in between, Mayer & Garder proposed the following equation for determining the Critical oil flow rate (Q_oc):

Where:

   Q_oc = critical oil well rate, STB/day
   h = oil column thickness, ft
   h_p= perforated interval, ft
   k_o= effective oil permeability, md
   (k_o= rock permeability x oil relative permeability)
  r_e = drainage radius of well, ft
  r_w = wellbore radius, ft
  B_o = formation volume factor of oil
   μ _o = oil viscosity, cp
   ρ _o = oil density, lb/ft³
   ρ _g = gas density, lb/ft³
   ρ _w = water density, lb/ft³

Note that the critical rate is the oil rate below which water or gas breakthrough will never occur; this rate may be too low for practical and economic reasons.

The optimal placement of the perforated interval is given by the following expression:

Where:

   D_t = distance from gas-oil contact to top of perforation, ft

BIBLIOGRAPHY

• Ahmed T.; Reservoir Engineering Handbook; Pennwell Publ Co, Tulsa, Oklahoma, 2000, chap. 9.
• Pirson S.J.; Oil Reservoir Engineering; Robert E. Krieger Publ. Co., Huntington, NY, 1977, chap. 8.