The difference between ideal Pwf and real Pwf is equal to what?

• A. The pressure drop due to skin.
• B. The pressure difference due to tubing friction
• C. The hydrostatic pressure
• D. The reservoir pressure drop

Answer: (A)

The difference comes from the near-wellbore resistance, known as the skin effect. In the ideal model, the flow sees no damage or abnormal conditions right around the well, so the pressure drop is due only to the broad reservoir flow. In reality, formation damage, drilling fluids, fines, or stimulation can create extra resistance in the skin zone, requiring additional pressure to push the same rate. That extra pressure drop is the skin-induced loss, and it’s exactly what makes real Pwf higher than the ideal Pwf. So the gap between the two Pwf values is the pressure drop caused by the skin effect.