Quantifying formation damage and improvement
Input(s)
\(p_{w f}\): Pressure of Wellflow (psi)
p: Pressure of Reservoir (psi)
s: Skin Factor (dimensionless)
\(r_{s}\): Radius of skin (ft)
\(r_{w}\): Radius of Wellbore (ft)
q: Flow Rate (STB/day)
\(\mathrm{k}\) : Permeability of Formation (mD)
\(\mu\) : Viscosity of Oil \((\mathrm{cP})\)
B: Volume factor \((\mathrm{RB} / \mathrm{STB})\)
\(\mathrm{h}\) : Thickness of reservoir \((\mathrm{ft})\)
Output(s)
\(k_{s}\): Permeability of altered zone \((\mathrm{mD})\)
\(r_{w a}\): Effective Radius of Wellbore (ft)
E: Flow Efficiency (fraction)
Formula(s)
\[
\begin{gathered}
k_{s}=\frac{k}{1+\frac{s}{\ln \left(\frac{r_{s}}{r_{w}}\right)}} \\
r_{w a}=r_{w} * 2.71828^{-s} \\
E=\frac{p-p_{w f}-\left(141.2 * q * B * \mu * \frac{s}{k * h}\right)}{p-p_{w f}}
\end{gathered}
\]
Reference(s)
Pressure Transient Testing, Lee, Rollins & Spivey, Page: 43.