When is gravel packing usually necessary in air rotary wells?

• A. To prevent gas migration
• B. To prevent sand intrusion
• C. To improve flow
• D. To reduce drilling times

Answer: (B)

Gravel packing is used when a well is in a formation that tends to produce sand. The gravel-packed screen acts as a filtration layer around the production path, allowing fluids to flow while stopping the sand grains from entering the wellbore. This is especially important in air rotary wells where unconsolidated or loosely cemented sands can cause sand intrusion that erodes equipment, plugs small passages, and shortens the life of the production string. So the primary purpose is to prevent sand intrusion, not to stop gas entering the well, improve flow by itself, or shorten drilling time.