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INPUT   DATA

Title

Horizontal length		ft
Wellbore radius		ft
Drainage radius		ft
Formation thickness		ft
Horizontal permeability		mD
Vertical permeability		mD
Formation volume factor
Viscosity		cp

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OUTPUT   VARIABLES

Productivity Index	STB/day/psi
♦  Borizov's Method
♦  Giger-Reiss-Jourdan Method
♦  Joshi's Method
♦  Renard-Dupuy Method
◊  Vertical Well

Horizontal Well Productivity Index (Oil)

The steady-state flow equation for a horizontal well is represented by:

     Q_oh = J_hΔp

where Q_oh = horizontal well oil flow rate, STB/day

     Δ p = pressure drop from drainage boundary to wellbore, psi

     J_h = productivity index.

The four commonly-used methods for predicting horizontal well productivity index from fluid properties and reservoir properties are:

Borizov’s method applies to the isotropic reservoir case where horizontal permeability equals vertical permeabilty. The other three methods apply to the more general anisotropic case.

The equations for each method is given below:

Where:

   J_h = productivity index, STB/day/psi
   h = thickness, ft
   k_h= horizontal permeability, md
  k_v = vertical permeability, md
  L = length of horizontal well, ft
  r_eh = drainage radius of horizontal well
  r_w = wellbore radius, ft
  a = half the major axis of the drainage ellipse, ft
  B_o = formation volume factor of oil
   μ _o = oil viscosity

For comparison, the corresponding equation for Vertical Well without skin is given by:

Note that drainage radius (ft) is derivable from drainage area A (acres) as follows:

  r_eh = √[43560A/π]

The output Graph will show the sensitivity of PI to drainage radius.

BIBLIOGRAPHY

• Ahmed T.; Reservoir Engineering Handbook; Pennwell Publ Co, Tulsa, Oklahoma, 2000, chap. 7.
• Joshi S.; Horizontal Well Technology; Pennwell Publ Co, Tulsa, Oklahoma, 1991.
• Economides M.J., Hill A.D. & Ehlig-Economides C.; Petroleum Production Systems; PTR Prentice Hall Inc. Englewood Cliffs, NJ, 1994, chap. 2.