What is the area near a perforation where permeability may be reduced, typically about 50% less than undamaged permeability?

• A. Radius of influence
• B. Crush Zone
• C. Annulus
• D. Damaged zone

Answer: (B)

In perforated wells, the perforation creates localized mechanical damage in the rock right around it. This region becomes a crush zone, where grains are crushed and pore throats bridged by fines, sharply reducing the rock’s ability to transmit fluids. That near-wellbore damage typically lowers permeability by a significant amount—often around half of the undamaged value—making this zone the key factor in early post-perforation flow performance. The other terms describe different ideas: radius of influence is about how far pressure or stress effects extend, the annulus is the hollow space between casing or strings, and a damaged zone is a generic label that doesn’t specify the mechanical crushing that characterizes the near-perforation area.