Which of the following is NOT a method used to clean the hole of cuttings in air rotary drilling in unconsolidated formations?

• A. Airflow
• B. Foam injection
• C. Polymer use
• D. Water flushing

Answer: (D)

In air rotary drilling for unconsolidated formations, removing cuttings relies primarily on the lifting action of the air column. The base method is airflow, which physically blows cuttings up to the surface. Foam injection is used to improve that lifting by creating a gas–liquid mixture that carries cuttings more effectively and helps stabilize them in the borehole. Polymers can be added to adjust the fluid’s rheology, helping to suspend cuttings and control fluid behavior, which also supports keeping the hole clean. Water flushing, however, would introduce liquid water into the system and disrupt the air-driven carrying efficiency; it can cause instability, washouts, and formation damage in unconsolidated sands, so it is not used as a method to clean the hole in this drilling mode.