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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

Well radius		ft
Horizontal permeability		mD
Vertical permeability		mD
Perforation radius		ft.
Perforation spacing		ft
Perforation length		ft
Perforation phasing angle		°
Perforation orientation angle		°

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OUTPUT   VARIABLES   &   GRAPHS

PseudoSkin, due to:	Skin Factor	Totals
♦  Perforation: 2D planar flow, s2D
♦  Perforation: 3D convergence flow, s3D
♦  Perforation: wellbore blockage, swb
♦♦  Perforation sp

Skin Factors In Perforated Horizontal Completions

The analysis of the different skin effects in a well completion is a necessary step in the optimization of completion and stimulation designs. The total skin is usually determined by the conventional transient pressure test analysis.

In a cased-hole perforated completion for a horizontal well, the perforation process depends mainly on the following parameters (shot density, hole-size, penetration, phasing, and perforation orientation). The perforation skin s_p is comprised of 3 sub-components: 2D plane flow s_2D , 3D convergence flow s_3D and wellbore blockage effects s_wb.

s_p = s_2D + s_3D + s_wb.

Herein is presented the means for estimating the completion-dependent skin factors for a horizontal well, based on the semi-analytic models by Furui et al. As an example of the model, a set of equations (for the 360-degree phasing scenario) is given below.

Skin Due To 2D planar flow:

Skin Due To Wellbore blockage of flow:

Skin Due To 3D convergent flow:

where
     h_p = perforation spacing = reciprocal of shots-per-ft
     r_w = wellbore radius, ft
     r_p = radius of tunnel created by perforation bullet, ft
     l_p = length of perforation tunnel, ft
     l_pD = l_p/r_w
     k_h = horizontal permeability of formation, mD
     k_v = vertical permeability of formation, mD
     α = perforation orientation = azimuth of perforation with respect horizontal direction, degrees
     θ = angle of perforation phasing, degrees
     a_m, b_m, c_m, d_m, e_m, f_m, g_m = Phasing-dependent coefficients tabulated in Furui et al and Karakas & Tariq.

Tips

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BIBLIOGRAPHY

• Furui K., Zhu D. & Hill A.D.; A new skin factor model for perforated horizontal wells; paper SPE-77363, 2002.
• Furui K.; A comprehensive skin factor model for well completions based on finite element simulations; PhD dissertation, The University of Texas at Austin, Texas, May 2004.
• Karakas M. & Tariq S.M.; Semianalytical productivity models for perforated completions; SPEPE, Feb., 1991, p. 73-82.
• Economides M.J., Hill A.D. & Ehlig-Economides C.; Petroleum Production Systems; PTR Prentice Hall Inc. Englewood Cliffs, NJ, 1994, chap. 5.