Normalised dimensionless difference between the actual drawdown wellbore pressure  $//<![CDATA[ \begin{array}{l}p_{wf}(t)\end{array} //]]>$ and a model of a full-entry vertical well with homogeneous reservoir and non-damaged near-reservoir zone $//<![CDATA[ \begin{array}{l}p^*_{wf}(t)\end{array} //]]>$:

where

$//<![CDATA[ \begin{array}{l}q_t\end{array} //]]>$ – total sandface rate

$//<![CDATA[ \begin{array}{l}\sigma\end{array} //]]>$ – formation transmissibility

By definition the skin-factor is a pressure adjustment at the well wall and does not affect pressure distribution in reservoir away from wellbore $//<![CDATA[ \begin{array}{l}r > r_s\end{array} //]]>$.

The total skin is usually decomposed to geometrical skin $//<![CDATA[ \begin{array}{l}S_G\end{array} //]]>$, related to deviation of the well-reservoir contact from the simplest model and mechanical skin $//<![CDATA[ \begin{array}{l}S_M\end{array} //]]>$, related to pressure drop caused by the near-reservoir zone formation damage:

Motivation