# Pseudo-skin factor due to perforations

## Input(s)

\(h_{p}\): Perforation interval (ft)

\(\mathrm{h}\): Total pay thickness \((\mathrm{ft})\)

\(h_{1}\) : Distance from top of reservoir to top of open interval (ft)

\(k_{v}\) : Horizontal permeability \((\mathrm{mD})\)

\(k_{h}\): Vertical permeability \((\mathrm{mD})\)

\(r_{w}\) : Wellbore dia (ft)

## Output(s)

b: Penetration ratio (dimensionless)

A: Constant for calc (dimensionless)

B: Constant for calc (dimensionless)

\(h_{d}\) : Dimensionless payzone thickness (dimensionless)

\(s_{p}\): Skin due to partial penetration (dimensionless)

## Formula(s)

\[
\begin{gathered}
b=\frac{h_{p}}{h} \\
A=\frac{h}{r_{w}} * \operatorname{sqrt}\left(\frac{k_{h}}{k_{v}}\right) \\
B=\frac{h}{h_{1}+0.25 * h_{p}} \\
h_{d}=\frac{h}{h_{1}+0.75 * h_{p}} \\
s_{p}=\frac{1-b}{b} * \ln \left(\pi * \frac{h_{d}}{2}\right)+\frac{1}{b} * \ln \left(\frac{b}{b+2} * \operatorname{sqrt}\left(\frac{A-1}{B-1}\right)\right)
\end{gathered}
\]

## Reference(s)

Horizontal Well Technology, Joshi, Page: 499.