NGWA REVIEW PACK 2026 SOLVED
QUESTIONS AND ACCURATE ANSWERS
◉ What conditions could call for more air volume in hard rock
drilling?
Answer: Deeper holes, larger hole diameter, and increased cuttings
in hard or fractured rock.
◉ How do RPMs differ between roller cone and DHH bits in hard
rock drilling?
Answer: RPMs for roller cone bits are typically lower (50-75 RPM)
DHH bits operate at higher RPMs (100-200 RPM) in hard rock
drilling.
◉ Compare speed/feed relationships in hard rock drilling using
roller cone bits.
Answer: Low RPM requires higher down pressure (feed) for
effective penetration.
Higher RPM with too much feed can cause bit wear or failure, while
too little feed can reduce drilling efficiency.
,◉ Fracture zones can cause crooked holes. What are some
indications that fracture zones are encountered?
Answer: Sudden changes in penetration rate, loss of air pressure,
hole deviation, or sudden drop in drill string weight
◉ The size of cuttings are indications that the bit is operating
properly. Explain this statement.
Answer: larger, uniform cuttings indicate efficient drilling, while
small or powdery cuttings suggest bit wear or improper function.
◉ How do roller cone bits differ for different formations?
Answer: Soft formations: Larger, wider teeth for faster cutting.
Hard formations: Smaller, tougher teeth with more durability.
◉ After cutting several hundred feet of hard rock the rate has slowed
down. What is the probably cause?
Answer: Bit wear or dulling, reducing cutting efficiency.
◉ What purpose does a Kelly saver sub serve?
Answer: A Kelly saver sub protects the Kelly from excessive wear by
absorbing the torque and stress during drilling operations.
, ◉ What type of lubrication system is used for DHH drilling?
Answer: a mist or oil injection lubrication system to reduce wear
and cool the hammer mechanism.
◉ Explain these terms: misting. dusting.
Answer: Misting: Injecting water or fluid into the air stream to
control dust and cool the bit.
Dusting: Drilling without sufficient fluid, resulting in excessive dust
and potential bit overheating.
◉ What is a surfactant? When is it needed?
Answer: Reduces surface tension; needed to create foam in drilling
fluids for effective cuttings removal.
◉ Explain the difference between high and low pressure air rotaries.
Answer: High-pressure air rotary: Faster drilling, better cuttings
removal, used in hard formations.
Low-pressure air rotary: Slower drilling, more controlled, used in
softer or unstable formations.
◉ Explain the difference between high and low volume air rotaries.
QUESTIONS AND ACCURATE ANSWERS
◉ What conditions could call for more air volume in hard rock
drilling?
Answer: Deeper holes, larger hole diameter, and increased cuttings
in hard or fractured rock.
◉ How do RPMs differ between roller cone and DHH bits in hard
rock drilling?
Answer: RPMs for roller cone bits are typically lower (50-75 RPM)
DHH bits operate at higher RPMs (100-200 RPM) in hard rock
drilling.
◉ Compare speed/feed relationships in hard rock drilling using
roller cone bits.
Answer: Low RPM requires higher down pressure (feed) for
effective penetration.
Higher RPM with too much feed can cause bit wear or failure, while
too little feed can reduce drilling efficiency.
,◉ Fracture zones can cause crooked holes. What are some
indications that fracture zones are encountered?
Answer: Sudden changes in penetration rate, loss of air pressure,
hole deviation, or sudden drop in drill string weight
◉ The size of cuttings are indications that the bit is operating
properly. Explain this statement.
Answer: larger, uniform cuttings indicate efficient drilling, while
small or powdery cuttings suggest bit wear or improper function.
◉ How do roller cone bits differ for different formations?
Answer: Soft formations: Larger, wider teeth for faster cutting.
Hard formations: Smaller, tougher teeth with more durability.
◉ After cutting several hundred feet of hard rock the rate has slowed
down. What is the probably cause?
Answer: Bit wear or dulling, reducing cutting efficiency.
◉ What purpose does a Kelly saver sub serve?
Answer: A Kelly saver sub protects the Kelly from excessive wear by
absorbing the torque and stress during drilling operations.
, ◉ What type of lubrication system is used for DHH drilling?
Answer: a mist or oil injection lubrication system to reduce wear
and cool the hammer mechanism.
◉ Explain these terms: misting. dusting.
Answer: Misting: Injecting water or fluid into the air stream to
control dust and cool the bit.
Dusting: Drilling without sufficient fluid, resulting in excessive dust
and potential bit overheating.
◉ What is a surfactant? When is it needed?
Answer: Reduces surface tension; needed to create foam in drilling
fluids for effective cuttings removal.
◉ Explain the difference between high and low pressure air rotaries.
Answer: High-pressure air rotary: Faster drilling, better cuttings
removal, used in hard formations.
Low-pressure air rotary: Slower drilling, more controlled, used in
softer or unstable formations.
◉ Explain the difference between high and low volume air rotaries.
