Certified Drilling Operator Licensing
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary function of the drill bit in rotary drilling?
a) To circulate drilling fluid
b) To cut and crush rock formations
c) To stabilize the borehole
d) To control formation pressure
Rationale: The drill bit’s main function is to cut, crush, and grind rock to
advance the borehole.
2. What is the purpose of drilling mud?
a) To lubricate the bit only
b) To cool the bit, carry cuttings, and control formation pressure
,c) To cement the casing
d) To measure formation pressure
Rationale: Drilling mud maintains borehole stability, removes cuttings, cools
and lubricates the bit, and balances formation pressure.
3. Which device prevents blowouts during drilling operations?
a) Drill collar
b) Kelly
c) Blowout preventer (BOP)
d) Mud pump
Rationale: The BOP seals the wellbore to prevent uncontrolled fluid flow.
4. The primary function of casing in a well is to:
a) Provide drilling fluid circulation
b) Support drill string
c) Prevent borehole collapse and isolate formations
d) Increase drilling speed
Rationale: Casing stabilizes the wellbore and isolates different pressure
zones.
5. What is the purpose of cementing operations in drilling?
a) To lubricate the drill string
,b) To secure casing and isolate formations
c) To remove drill cuttings
d) To increase bit life
Rationale: Cement bonds casing to the borehole wall and prevents fluid
migration.
6. What unit measures the density of drilling mud?
a) PSI
b) Gallons per minute
c) Pounds per gallon (ppg)
d) Cubic feet
Rationale: Mud weight is expressed in pounds per gallon to reflect its density
and pressure control ability.
7. The term “kick” in drilling refers to:
a) Sudden bit movement
b) Influx of formation fluids into the wellbore
c) Casing pressure loss
d) Drill string vibration
Rationale: A kick indicates formation fluid entering the well due to
underbalanced pressure.
, 8. Which of the following is a sign of an impending kick?
a) Decrease in mud flow
b) Increase in mud viscosity
c) Increase in pit volume
d) Decrease in pump pressure
Rationale: An increase in mud pit volume signals fluid entering the wellbore.
9. The rotary table’s function is to:
a) Rotate the drill string
b) Control mud pressure
c) Measure formation pressure
d) Provide circulation
Rationale: The rotary table turns the drill string to cut through formations.
10. The top drive replaces which traditional component?
a) Mud pump
b) Kelly and rotary table
c) Casing
d) Drill collar
Rationale: A top drive rotates the drill string without requiring a Kelly.
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary function of the drill bit in rotary drilling?
a) To circulate drilling fluid
b) To cut and crush rock formations
c) To stabilize the borehole
d) To control formation pressure
Rationale: The drill bit’s main function is to cut, crush, and grind rock to
advance the borehole.
2. What is the purpose of drilling mud?
a) To lubricate the bit only
b) To cool the bit, carry cuttings, and control formation pressure
,c) To cement the casing
d) To measure formation pressure
Rationale: Drilling mud maintains borehole stability, removes cuttings, cools
and lubricates the bit, and balances formation pressure.
3. Which device prevents blowouts during drilling operations?
a) Drill collar
b) Kelly
c) Blowout preventer (BOP)
d) Mud pump
Rationale: The BOP seals the wellbore to prevent uncontrolled fluid flow.
4. The primary function of casing in a well is to:
a) Provide drilling fluid circulation
b) Support drill string
c) Prevent borehole collapse and isolate formations
d) Increase drilling speed
Rationale: Casing stabilizes the wellbore and isolates different pressure
zones.
5. What is the purpose of cementing operations in drilling?
a) To lubricate the drill string
,b) To secure casing and isolate formations
c) To remove drill cuttings
d) To increase bit life
Rationale: Cement bonds casing to the borehole wall and prevents fluid
migration.
6. What unit measures the density of drilling mud?
a) PSI
b) Gallons per minute
c) Pounds per gallon (ppg)
d) Cubic feet
Rationale: Mud weight is expressed in pounds per gallon to reflect its density
and pressure control ability.
7. The term “kick” in drilling refers to:
a) Sudden bit movement
b) Influx of formation fluids into the wellbore
c) Casing pressure loss
d) Drill string vibration
Rationale: A kick indicates formation fluid entering the well due to
underbalanced pressure.
, 8. Which of the following is a sign of an impending kick?
a) Decrease in mud flow
b) Increase in mud viscosity
c) Increase in pit volume
d) Decrease in pump pressure
Rationale: An increase in mud pit volume signals fluid entering the wellbore.
9. The rotary table’s function is to:
a) Rotate the drill string
b) Control mud pressure
c) Measure formation pressure
d) Provide circulation
Rationale: The rotary table turns the drill string to cut through formations.
10. The top drive replaces which traditional component?
a) Mud pump
b) Kelly and rotary table
c) Casing
d) Drill collar
Rationale: A top drive rotates the drill string without requiring a Kelly.
