Pressure Drop Across Perforations in Gas Wells Formula
Pressure Drop Across Perforations in Gas Wells calculates sandface pressure for well performance workflows in production engineering.
How engineers use this formula
Use this formula when the listed inputs (q_g, n, mu_g, Z, T, L_p, k_pd, r_p, r_pd, gamma_g, p_wb) are known and the assumptions behind the cited well performance relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, p_sf equals 2,101.819712 psi.
5000
40
0.02
0.9
640
0.5
100
0.02
0.25
0.65
2000
Inputs
q_g
bbl/dayGas Flow Rate Through Perforations
n
countNumber of Perforations
mu_g
cPGas Viscosity
Z
dimensionlessGas Compressibility Factor
T
RReservoir Temperature
L_p
ftPerforation Tunnel Length
k_pd
mDDamaged-Zone Permeability
r_p
ftPerforation Radius
r_pd
ftDamaged-Zone Radius Around Perforation
gamma_g
dimensionlessGas Specific Gravity
p_wb
psiWellbore Pressure
Outputs
p_sf
Sandface Pressure
p_wb
Wellbore Pressure
Source and review
reviewedPerforating, Bell, W. T., Sukup, R. A., Tariq, S. M. (1995)
Bell, W.T., Sukup, R.A. and Tariq, S.M. 1995. Perforating, SPE Reprint Series, Page 62.