NGWA CABLE TOOL DRILLING EXAM (A/B) – COMPLETE
PRACTICE QUESTION BANK (1–250)
. What is the primary reason cable tool drilling is classified as a "percussion"
method?
A) It uses continuous rotation to grind rock
B) It relies on the weight of the tools falling to fracture rock
C) It uses high-pressure water to erode formations
D) It uses chemical reactions to dissolve rock
Correct Answer: B) It relies on the weight of the tools falling to fracture rock
Rationale: Percussion drilling operates by repeatedly lifting and dropping a heavy bit. The
impact force, not rotation or abrasion, is the primary mechanism that fractures the rock.
2. Which of the following best describes the role of the "drilling line" on a cable
tool rig?
A) It carries electrical power to downhole tools
B) It serves as the main hoisting and suspension cable for the drill stem
C) It pumps drilling fluid into the borehole
D) It measures the depth of the hole
Correct Answer: B) It serves as the main hoisting and suspension cable for the drill
stem
Rationale: The drilling line (wire rope) runs from the bull reel, over the crown sheave, and
down to the swivel. It is responsible for raising, lowering, and suspending the entire drill
stem during operations.
, 3. What is the primary advantage of using a cable tool rig in a fractured bedrock
formation?
A) It seals fractures with drilling mud
B) It does not use drilling fluids that could plug the fractures
C) It drills faster than any other method
D) It requires less fuel
Correct Answer: B) It does not use drilling fluids that could plug the fractures
Rationale: Cable tool drilling uses minimal water and no circulating mud. This prevents
the fine particles from sealing the natural fractures in the bedrock, which could otherwise
reduce the well's yield.
4. What is the function of the "crown sheave" at the top of the derrick?
A) To rotate the drill bit
B) To guide the drilling line and reduce friction
C) To pump water into the hole
D) To measure the weight of the drill string
Correct Answer: B) To guide the drilling line and reduce friction
Rationale: The crown sheave is a grooved pulley mounted at the top of the derrick. It
changes the direction of the drilling line from the bull reel to a vertical path down to the
swivel, while minimizing wear on the line.
5. When bailing a hole, what is the purpose of the "valve" at the bottom of the
bailer?
A) To allow water to escape on the way down
B) To trap cuttings and water inside the bailer during lifting
C) To rotate the bailer
D) To measure the temperature of the slurry
Correct Answer: B) To trap cuttings and water inside the bailer during lifting
, Rationale: The valve (either a flap or dart type) opens when the bailer hits the bottom,
allowing slurry to enter. When the bailer is lifted, the valve closes, trapping the cuttings
inside for removal.
6. Why is it important to "sound" the borehole before lowering the drill tools back
in?
A) To ensure the hole is still open and to measure the depth of accumulated cuttings
B) To listen for water flow
C) To check the temperature of the hole
D) To test the casing for leaks
Correct Answer: A) To ensure the hole is still open and to measure the depth of
accumulated cuttings
Rationale: Sounding (measuring depth with a weighted tape) confirms that the hole has
not caved in and tells the driller how much cuttings have settled at the bottom, allowing
proper adjustment of the feed.
7. What type of bit is most effective for drilling through hard, abrasive quartzite?
A) A fishtail bit
B) A blunt-nosed steel bit with a hardened cutting edge
C) A star bit with sharp points
D) A drag bit
Correct Answer: B) A blunt-nosed steel bit with a hardened cutting edge
Rationale: In extremely hard and abrasive rock, a bit with a robust, hardened, blunt profile
is used. The blunt edge spalls (shatters) the rock under impact rather than trying to cut it,
which would dull a sharp bit instantly.
8. What is the primary purpose of "drilling jars" in the drill stem?
, A) To add extra weight to the bit
B) To act as a shock absorber
C) To deliver a sharp blow to free stuck tools
D) To increase the drilling stroke length
Correct Answer: C) To deliver a sharp blow to free stuck tools
Rationale: Drilling jars are telescoping tools that store energy as they are stretched. When
they snap shut, they deliver a powerful upward impact to help dislodge tools that have
become wedged or stuck.
9. What is a "sinker bar" typically made of, and why?
A) Aluminum, to reduce weight
B) Solid steel, to provide maximum weight and momentum
C) Plastic, to reduce cost
D) Copper, for electrical conductivity
Correct Answer: B) Solid steel, to provide maximum weight and momentum
Rationale: Sinker bars are solid, heavy steel bars. Their mass provides the necessary
downward inertia to the bit, ensuring each impact delivers sufficient energy to fracture the
rock.
10. In cable tool drilling, what does "stroke length" refer to?
A) The distance the bit is lifted off the bottom before dropping
B) The total depth of the well
C) The length of the drill bit
D) The distance between the walking beam and the derrick
Correct Answer: A) The distance the bit is lifted off the bottom before dropping
Rationale: Stroke length is the vertical distance the walking beam raises the drill stem. This
distance directly affects the impact energy of the bit and is adjustable based on the
formation hardness.
PRACTICE QUESTION BANK (1–250)
. What is the primary reason cable tool drilling is classified as a "percussion"
method?
A) It uses continuous rotation to grind rock
B) It relies on the weight of the tools falling to fracture rock
C) It uses high-pressure water to erode formations
D) It uses chemical reactions to dissolve rock
Correct Answer: B) It relies on the weight of the tools falling to fracture rock
Rationale: Percussion drilling operates by repeatedly lifting and dropping a heavy bit. The
impact force, not rotation or abrasion, is the primary mechanism that fractures the rock.
2. Which of the following best describes the role of the "drilling line" on a cable
tool rig?
A) It carries electrical power to downhole tools
B) It serves as the main hoisting and suspension cable for the drill stem
C) It pumps drilling fluid into the borehole
D) It measures the depth of the hole
Correct Answer: B) It serves as the main hoisting and suspension cable for the drill
stem
Rationale: The drilling line (wire rope) runs from the bull reel, over the crown sheave, and
down to the swivel. It is responsible for raising, lowering, and suspending the entire drill
stem during operations.
, 3. What is the primary advantage of using a cable tool rig in a fractured bedrock
formation?
A) It seals fractures with drilling mud
B) It does not use drilling fluids that could plug the fractures
C) It drills faster than any other method
D) It requires less fuel
Correct Answer: B) It does not use drilling fluids that could plug the fractures
Rationale: Cable tool drilling uses minimal water and no circulating mud. This prevents
the fine particles from sealing the natural fractures in the bedrock, which could otherwise
reduce the well's yield.
4. What is the function of the "crown sheave" at the top of the derrick?
A) To rotate the drill bit
B) To guide the drilling line and reduce friction
C) To pump water into the hole
D) To measure the weight of the drill string
Correct Answer: B) To guide the drilling line and reduce friction
Rationale: The crown sheave is a grooved pulley mounted at the top of the derrick. It
changes the direction of the drilling line from the bull reel to a vertical path down to the
swivel, while minimizing wear on the line.
5. When bailing a hole, what is the purpose of the "valve" at the bottom of the
bailer?
A) To allow water to escape on the way down
B) To trap cuttings and water inside the bailer during lifting
C) To rotate the bailer
D) To measure the temperature of the slurry
Correct Answer: B) To trap cuttings and water inside the bailer during lifting
, Rationale: The valve (either a flap or dart type) opens when the bailer hits the bottom,
allowing slurry to enter. When the bailer is lifted, the valve closes, trapping the cuttings
inside for removal.
6. Why is it important to "sound" the borehole before lowering the drill tools back
in?
A) To ensure the hole is still open and to measure the depth of accumulated cuttings
B) To listen for water flow
C) To check the temperature of the hole
D) To test the casing for leaks
Correct Answer: A) To ensure the hole is still open and to measure the depth of
accumulated cuttings
Rationale: Sounding (measuring depth with a weighted tape) confirms that the hole has
not caved in and tells the driller how much cuttings have settled at the bottom, allowing
proper adjustment of the feed.
7. What type of bit is most effective for drilling through hard, abrasive quartzite?
A) A fishtail bit
B) A blunt-nosed steel bit with a hardened cutting edge
C) A star bit with sharp points
D) A drag bit
Correct Answer: B) A blunt-nosed steel bit with a hardened cutting edge
Rationale: In extremely hard and abrasive rock, a bit with a robust, hardened, blunt profile
is used. The blunt edge spalls (shatters) the rock under impact rather than trying to cut it,
which would dull a sharp bit instantly.
8. What is the primary purpose of "drilling jars" in the drill stem?
, A) To add extra weight to the bit
B) To act as a shock absorber
C) To deliver a sharp blow to free stuck tools
D) To increase the drilling stroke length
Correct Answer: C) To deliver a sharp blow to free stuck tools
Rationale: Drilling jars are telescoping tools that store energy as they are stretched. When
they snap shut, they deliver a powerful upward impact to help dislodge tools that have
become wedged or stuck.
9. What is a "sinker bar" typically made of, and why?
A) Aluminum, to reduce weight
B) Solid steel, to provide maximum weight and momentum
C) Plastic, to reduce cost
D) Copper, for electrical conductivity
Correct Answer: B) Solid steel, to provide maximum weight and momentum
Rationale: Sinker bars are solid, heavy steel bars. Their mass provides the necessary
downward inertia to the bit, ensuring each impact delivers sufficient energy to fracture the
rock.
10. In cable tool drilling, what does "stroke length" refer to?
A) The distance the bit is lifted off the bottom before dropping
B) The total depth of the well
C) The length of the drill bit
D) The distance between the walking beam and the derrick
Correct Answer: A) The distance the bit is lifted off the bottom before dropping
Rationale: Stroke length is the vertical distance the walking beam raises the drill stem. This
distance directly affects the impact energy of the bit and is adjustable based on the
formation hardness.
