A perforated height less than reservoir height can lead to which skin effect?

• A. Positive Skin Effects
• B. Negative Skin Effects
• C. No Skin
• D. Neutral Skin

Answer: (A)

The main idea is that skin represents extra pressure drop caused by changes in the near-well region. When perforations only cover a portion of the reservoir height, the flow into the well can come from a smaller vertical drainage area. That limited opening creates more disturbance and friction near the wellbore, increasing the resistance to flow compared with the undisturbed formation. The resulting additional pressure drop is what we call a positive skin effect. If the perforated interval were as tall as the reservoir (or if stimulation across a larger area occurred), the near-well resistance would be lower, reducing skin.