Heavy steel casing would best be used in what rotary process?

• A. Air rotary process
• B. Mud rotary process
• C. Cable tool drilling
• D. Diamond core drilling

Answer: (A)

Heavy steel casing is most appropriate for air rotary drilling because this method uses only air to lift and remove cuttings, with no drilling fluid to support the borehole walls. Without mud or water to buoy and stabilize the hole, the formation can collapse if the walls aren’t braced. Installing heavy steel casing provides the necessary structural support to prevent caving, helps isolate aquifers, and allows unrestricted air circulation down the bore, which is essential for efficient air drilling.

In mud rotary, the drilling fluid itself supports the hole and carries cuttings, so heavy casing is less critical for wall stability. Cable tool and diamond core drilling have different operating requirements and typically do not rely on heavy casing for the same stabilization purpose as in air rotary, making them less suitable contexts for this use.