Exam Practice Questions And Correct

Certified Drilling Operator Licensing Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• 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.

• What is the purpose of drilling mud?

a) To lubricate the bit only

b) To cool the bit, carry cuttings, and control formation pressure 1 / 4

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.

• 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.

• What is the purpose of cementing operations in drilling?

a) To lubricate the drill string 2 / 4

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.

• 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.

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• 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.

• 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.

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