NGWA Air Rotary Drilling Certification
Exam (Exam C) – 100 Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of the air rotary drilling method?
A. To circulate drilling mud
B. To maintain borehole stability
C. To remove cuttings using compressed air
D. To control formation water flow
Rationale: Air rotary drilling uses compressed air to lift cuttings to
the surface while drilling, rather than relying on mud circulation.
2. Which component is essential for creating a seal at the bottom of the
borehole in air rotary drilling?
A. Drill collar
, B. Drill bit
C. Kelly bar
D. Casing
Rationale: The drill bit creates a seal at the bottom to help lift
cuttings with the compressed air.
3. What is the typical range of air pressure used in air rotary drilling?
A. 10–20 psi
B. 30–50 psi
C. 100–250 psi
D. 300–500 psi
Rationale: Air rotary drilling commonly uses compressed air
pressures in the range of 100–250 psi to effectively remove cuttings.
4. Which type of drill bit is most commonly used in air rotary drilling of
unconsolidated formations?
A. Diamond bit
B. Roller-cone bit
C. Core bit
D. Drag bit
Rationale: Roller-cone bits are designed to crush and break
formations efficiently and are common in air rotary drilling.
5. What is the main disadvantage of air rotary drilling in water-bearing
formations?
A. Bit wear
, B. Loss of borehole stability due to lack of fluid support
C. High cost
D. Slow penetration
Rationale: Without drilling mud, formations can collapse or cave in,
making air rotary less suitable for unconsolidated, water-saturated
zones.
6. What is the purpose of a swivel in an air rotary drilling rig?
A. To circulate mud
B. To measure borehole depth
C. To allow the drill string to rotate while supplying compressed air
D. To anchor the rig
Rationale: The swivel connects the drill string to the air supply while
allowing rotation.
7. When drilling through a hard formation, which adjustment can
increase penetration rate?
A. Reduce air pressure
B. Increase bit rotation speed
C. Increase downward weight on the bit
D. Reduce bit size
Rationale: Applying more weight on the bit helps it break harder rock
formations faster.
8. What is a common method to stabilize the borehole in air rotary
drilling?
, A. Circulating water
B. Using casing or temporary liners
C. Increasing air flow
D. Reducing rotation speed
Rationale: Casing or liners prevent loose formations from caving into
the borehole in the absence of drilling fluid.
9. Which type of air rotary drilling is specifically designed to collect rock
core samples?
A. Standard air rotary
B. Air core drilling
C. Reverse circulation
D. Mud rotary
Rationale: Air core drilling uses a hollow drill bit to recover rock cores
while lifting cuttings with compressed air.
10. Which factor primarily affects the lift capacity of air in an air
rotary system?
A. Drill string length
B. Air pressure and volume
C. Bit type
D. Casing diameter
Rationale: Higher air pressure and volume increase the ability to lift
cuttings to the surface.
Exam (Exam C) – 100 Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of the air rotary drilling method?
A. To circulate drilling mud
B. To maintain borehole stability
C. To remove cuttings using compressed air
D. To control formation water flow
Rationale: Air rotary drilling uses compressed air to lift cuttings to
the surface while drilling, rather than relying on mud circulation.
2. Which component is essential for creating a seal at the bottom of the
borehole in air rotary drilling?
A. Drill collar
, B. Drill bit
C. Kelly bar
D. Casing
Rationale: The drill bit creates a seal at the bottom to help lift
cuttings with the compressed air.
3. What is the typical range of air pressure used in air rotary drilling?
A. 10–20 psi
B. 30–50 psi
C. 100–250 psi
D. 300–500 psi
Rationale: Air rotary drilling commonly uses compressed air
pressures in the range of 100–250 psi to effectively remove cuttings.
4. Which type of drill bit is most commonly used in air rotary drilling of
unconsolidated formations?
A. Diamond bit
B. Roller-cone bit
C. Core bit
D. Drag bit
Rationale: Roller-cone bits are designed to crush and break
formations efficiently and are common in air rotary drilling.
5. What is the main disadvantage of air rotary drilling in water-bearing
formations?
A. Bit wear
, B. Loss of borehole stability due to lack of fluid support
C. High cost
D. Slow penetration
Rationale: Without drilling mud, formations can collapse or cave in,
making air rotary less suitable for unconsolidated, water-saturated
zones.
6. What is the purpose of a swivel in an air rotary drilling rig?
A. To circulate mud
B. To measure borehole depth
C. To allow the drill string to rotate while supplying compressed air
D. To anchor the rig
Rationale: The swivel connects the drill string to the air supply while
allowing rotation.
7. When drilling through a hard formation, which adjustment can
increase penetration rate?
A. Reduce air pressure
B. Increase bit rotation speed
C. Increase downward weight on the bit
D. Reduce bit size
Rationale: Applying more weight on the bit helps it break harder rock
formations faster.
8. What is a common method to stabilize the borehole in air rotary
drilling?
, A. Circulating water
B. Using casing or temporary liners
C. Increasing air flow
D. Reducing rotation speed
Rationale: Casing or liners prevent loose formations from caving into
the borehole in the absence of drilling fluid.
9. Which type of air rotary drilling is specifically designed to collect rock
core samples?
A. Standard air rotary
B. Air core drilling
C. Reverse circulation
D. Mud rotary
Rationale: Air core drilling uses a hollow drill bit to recover rock cores
while lifting cuttings with compressed air.
10. Which factor primarily affects the lift capacity of air in an air
rotary system?
A. Drill string length
B. Air pressure and volume
C. Bit type
D. Casing diameter
Rationale: Higher air pressure and volume increase the ability to lift
cuttings to the surface.
