Exam C/D – Air Rotary Drilling Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of using compressed air in air rotary
drilling?
A) To cool the drill bit
B) To lubricate the drill string
C) To lift cuttings from the borehole
D) To reduce water consumption
Answer: C) To lift cuttings from the borehole
Rationale: Compressed air is primarily used to lift drill cuttings to the
surface, clearing the borehole and maintaining drilling efficiency.
While air can provide some cooling, its main function is the removal of
cuttings.
, 2. In air rotary drilling, which component directly supports the drill
bit and transfers rotational energy from the rig?
A) Kelly
B) Drill collar
C) Drill string
D) Rotary table
Answer: C) Drill string
Rationale: The drill string transmits rotational energy from the rig to
the drill bit and supports the bit’s weight. The drill collar adds weight
on the bit but does not transmit rotation independently.
3. Which factor primarily affects the rate of penetration (ROP) in air
rotary drilling?
A) Borehole diameter
B) Drill bit type and formation hardness
C) Mud density
D) Air temperature
Answer: B) Drill bit type and formation hardness
Rationale: The ROP is most influenced by the combination of drill bit
type and the hardness of the formation being drilled. Softer
formations and appropriate bit selection increase penetration.
, 4. What is a major hazard associated with air rotary drilling in
unconsolidated formations?
A) Formation collapse
B) Gas hydrate formation
C) Excessive torque
D) Mud contamination
Answer: A) Formation collapse
Rationale: In unconsolidated formations, the borehole walls may
collapse due to insufficient support. Air alone does not stabilize the
hole, so casing or liners may be needed.
5. What does the term "annular velocity" refer to in air rotary
drilling?
A) The rotation speed of the drill bit
B) The speed of air or fluid up the annular space
C) The rate at which cuttings enter the drill string
D) The torque applied to the drill stem
Answer: B) The speed of air or fluid up the annular space
Rationale: Annular velocity is the upward speed of air or fluid in the
space between the drill string and the borehole wall, crucial for
efficient cutting removal.
, 6. Which type of drill bit is most commonly used in air rotary drilling
of hard rock formations?
A) Drag bit
B) Tricone bit
C) Diamond core bit
D) Auger bit
Answer: B) Tricone bit
Rationale: Tricone bits are versatile and effective in hard rock
formations, providing higher ROP and durability compared to drag or
auger bits.
7. What is a typical indication that a borehole has lost circulation
during air rotary drilling?
A) Decreased air pressure and excessive cuttings in the hole
B) Increase in torque
C) Faster ROP
D) Drill bit overheating
Answer: A) Decreased air pressure and excessive cuttings in the hole
Rationale: Loss of circulation occurs when air escapes into the
formation, leading to lower pressure in the annulus and irregular
cuttings transport.
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of using compressed air in air rotary
drilling?
A) To cool the drill bit
B) To lubricate the drill string
C) To lift cuttings from the borehole
D) To reduce water consumption
Answer: C) To lift cuttings from the borehole
Rationale: Compressed air is primarily used to lift drill cuttings to the
surface, clearing the borehole and maintaining drilling efficiency.
While air can provide some cooling, its main function is the removal of
cuttings.
, 2. In air rotary drilling, which component directly supports the drill
bit and transfers rotational energy from the rig?
A) Kelly
B) Drill collar
C) Drill string
D) Rotary table
Answer: C) Drill string
Rationale: The drill string transmits rotational energy from the rig to
the drill bit and supports the bit’s weight. The drill collar adds weight
on the bit but does not transmit rotation independently.
3. Which factor primarily affects the rate of penetration (ROP) in air
rotary drilling?
A) Borehole diameter
B) Drill bit type and formation hardness
C) Mud density
D) Air temperature
Answer: B) Drill bit type and formation hardness
Rationale: The ROP is most influenced by the combination of drill bit
type and the hardness of the formation being drilled. Softer
formations and appropriate bit selection increase penetration.
, 4. What is a major hazard associated with air rotary drilling in
unconsolidated formations?
A) Formation collapse
B) Gas hydrate formation
C) Excessive torque
D) Mud contamination
Answer: A) Formation collapse
Rationale: In unconsolidated formations, the borehole walls may
collapse due to insufficient support. Air alone does not stabilize the
hole, so casing or liners may be needed.
5. What does the term "annular velocity" refer to in air rotary
drilling?
A) The rotation speed of the drill bit
B) The speed of air or fluid up the annular space
C) The rate at which cuttings enter the drill string
D) The torque applied to the drill stem
Answer: B) The speed of air or fluid up the annular space
Rationale: Annular velocity is the upward speed of air or fluid in the
space between the drill string and the borehole wall, crucial for
efficient cutting removal.
, 6. Which type of drill bit is most commonly used in air rotary drilling
of hard rock formations?
A) Drag bit
B) Tricone bit
C) Diamond core bit
D) Auger bit
Answer: B) Tricone bit
Rationale: Tricone bits are versatile and effective in hard rock
formations, providing higher ROP and durability compared to drag or
auger bits.
7. What is a typical indication that a borehole has lost circulation
during air rotary drilling?
A) Decreased air pressure and excessive cuttings in the hole
B) Increase in torque
C) Faster ROP
D) Drill bit overheating
Answer: A) Decreased air pressure and excessive cuttings in the hole
Rationale: Loss of circulation occurs when air escapes into the
formation, leading to lower pressure in the annulus and irregular
cuttings transport.
