Difference between the actual wellbore pressure and a pressure model of a full-entry vertical well with homogeneous reservoir and non-damaged near-reservoir zone:
| S=\frac{2 \pi \sigma }{q_t} \, \delta p |
By definition the skin-factor is a pressure adjustment at the well wall and does not affect pressure distribution in reservoir away from wellbore.
Dimensionless value characterising permeability change in a thin layer around the well cased by stimulations or deteriorations, represented by Hawkins' equation:
| (1) | S = \left ( \frac{k}{k_s} - 1 \right ) \ \ln \left ( \frac{r_s}{r_w} \right ) |