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.