Drag bits are recommended for which formation type?

Drag bits are recommended for which formation type?

• A. Soft formations such as clay and silt
• B. Hard rock with high hardness
• C. Cemented sandstone
• D. Basaltic rock

Answer: (A)

Drag bits are best for soft, unconsolidated formations because their cutting action relies on scraping and plowing rather than crushing. In materials like clay and silt, the rock yields easily, so a drag bit can advance efficiently with less wear and heat, making it a good match for air rotary drilling where cuttings are carried out by the airflow. For harder formations—high-hardness rock, cemented sandstone, or basaltic rock—the same bit would wear rapidly and struggle to penetrate. Those conditions require more robust cutting elements or different bit designs (such as roller-cone or PDC-type bits) that can resist abrasion and provide the necessary aggressiveness to break strong, cemented, or highly abrasive material.

Drag bits are best for soft, unconsolidated formations because their cutting action relies on scraping and plowing rather than crushing. In materials like clay and silt, the rock yields easily, so a drag bit can advance efficiently with less wear and heat, making it a good match for air rotary drilling where cuttings are carried out by the airflow.

For harder formations—high-hardness rock, cemented sandstone, or basaltic rock—the same bit would wear rapidly and struggle to penetrate. Those conditions require more robust cutting elements or different bit designs (such as roller-cone or PDC-type bits) that can resist abrasion and provide the necessary aggressiveness to break strong, cemented, or highly abrasive material.