Skin estimation type-1 (pressure buildup test)
Input(s)
\(P_{h r}\): Pressure After One Hour of Well Shut-in (psi)
\(P_{w f}\): Well Flowing Pressure (psi)
\(\mathrm{m}\): Slope of Horner Plot (psi/cycle)
k: Permeability \((\mathrm{mD})\)
\(\emptyset\): Porosity (fraction)
\(c_{t}\): Total Compressibility (1/psi)
\(r_{w}\): Wellbore Radius (ft)
\(\mu_{o}\): Oil Viscosity \((\mathrm{cP})\)
Output(s)
s: Skin Factor (dimensionless)
Formula(s)
\[
s=1.151 *\left(\left(\frac{\left(P_{h r}\right)-P_{w f}}{m}\right)-\log \left(\frac{k}{\not *_{0} * c_{t} * r_{w}^{2}}\right)+3.23\right)
\]
Notes: Skin Estimation from Horner Plot (Semi Log Plot).
Reference(s)
Lee, J., Rollins, J. B., & Spivey, J. P. (2003). Pressure Transient Testing (Vol. 9). Richardson, Texas: Society of Petroleum Engineers, Page: 104.