API Drilling and Production 2 — Questions and Answers
Question 1: What is the primary purpose of a blowout preventer (BOP) stack in drilling operations?
- To increase drilling fluid weight
- To seal the wellbore and control well pressure (Correct answer)
- To guide the drill string into the formation
- To circulate drilling mud to the surface
Correct answer: To seal the wellbore and control well pressure
A BOP stack is designed to seal the wellbore and prevent uncontrolled release of formation fluids during drilling.
Question 2: In directional drilling, what does the term 'dogleg severity' refer to?
- The total depth of the wellbore
- The rate of change in wellbore angle and direction per 100 feet (Correct answer)
- The weight applied on the drill bit
- The friction factor between casing and formation
Correct answer: The rate of change in wellbore angle and direction per 100 feet
Dogleg severity measures the rate of change in wellbore inclination and azimuth, typically expressed in degrees per 100 feet.
Question 3: What is the function of a 'mud motor' (downhole motor) in drilling?
- To pump drilling fluid from the surface
- To convert hydraulic energy of drilling fluid into rotational energy to turn the bit (Correct answer)
- To measure formation pressure downhole
- To cement casing strings in place
Correct answer: To convert hydraulic energy of drilling fluid into rotational energy to turn the bit
A mud motor uses the hydraulic power of circulating drilling fluid to rotate the drill bit independently of the drill string rotation.
Question 4: Which type of casing is set first when drilling an oil or gas well?
- Production casing
- Intermediate casing
- Conductor casing (Correct answer)
- Liner
Correct answer: Conductor casing
Conductor casing is the first and shallowest casing set to prevent shallow formation collapse and direct returns to the surface.
Question 5: What does 'WOB' stand for in drilling engineering?
- Well Operation Baseline
- Weight on Bit (Correct answer)
- Wellbore Orientation Bearing
- Water Oil Boundary
Correct answer: Weight on Bit
WOB (Weight on Bit) is the amount of downward force applied to the drill bit to facilitate penetration of the formation.
Question 6: In production operations, what is the purpose of a 'choke' on a wellhead?
- To prevent corrosion in the tubing string
- To control flow rate and pressure from the producing well (Correct answer)
- To inject chemicals into the wellbore
- To measure the gas-oil ratio of production
Correct answer: To control flow rate and pressure from the producing well
A choke is a flow restriction device used to control production rate and regulate wellhead pressure.
Question 7: What is 'equivalent circulating density' (ECD) in drilling?
- The density of formation water in porous media
- The effective mud weight at a given depth accounting for annular pressure losses during circulation (Correct answer)
- The density difference between oil and gas at surface conditions
- The weight per foot of drill collars used in the BHA
Correct answer: The effective mud weight at a given depth accounting for annular pressure losses during circulation
ECD represents the total equivalent mud weight felt at the bottom of the hole, including both static mud weight and friction pressure from circulation.
API Drilling and Production 2
What is the primary purpose of a blowout preventer (BOP) stack in drilling operations?