1. n. [Well Completions]

A dimensionless factor calculated to determine the production efficiency of a well by comparing actual conditions with theoretical or ideal conditions. A positive skin value indicates some damage or influences that are impairing well productivity. A negative skin value indicates enhanced productivity, typically resulting from stimulation.

2. n. [Well Testing]

The zone of reduced or enhanced permeability around a wellbore, often explained by formation damage and mud-filtrate invasion during drilling or perforating, or by well stimulation.