SPE Drilling & Well Completion 2 — Questions and Answers
Question 1: What is the primary purpose of a diverter system installed at the wellhead during top-hole drilling?
- Prevent blowouts by closing the BOP stack
- Divert shallow gas flows away from the rig floor to protect personnel (Correct answer)
- Control mud weight during drilling
- Seal the annulus against formation fluids
Correct answer: Divert shallow gas flows away from the rig floor to protect personnel
Diverter systems redirect unexpected shallow gas influxes away from the rig floor, protecting personnel since BOPs are not yet installed.
Question 2: In a horizontal well, what is the primary function of a rotary steerable system (RSS)?
- Increase weight on bit
- Provide continuous rotation while steering the bit to the target trajectory (Correct answer)
- Reduce equivalent circulating density
- Circulate cuttings out of the wellbore
Correct answer: Provide continuous rotation while steering the bit to the target trajectory
An RSS allows the drillstring to rotate continuously while a steering mechanism deflects the bit toward the planned trajectory.
Question 3: Which cement slurry additive is used to prevent gas migration through unset cement?
- Retarder
- Dispersant
- Expanding agent or anti-gas migration additive (Correct answer)
- Weighting material
Correct answer: Expanding agent or anti-gas migration additive
Anti-gas migration additives (e.g., expanding agents or latex) reduce cement permeability and control gel strength development to block gas channels.
Question 4: What does the term 'equivalent circulating density' (ECD) represent in drilling operations?
- The density of the drilling fluid at surface conditions
- The effective mud weight at a given depth accounting for annular friction pressure losses (Correct answer)
- The weight of cuttings suspended in the mud
- The density required to prevent wellbore collapse
Correct answer: The effective mud weight at a given depth accounting for annular friction pressure losses
ECD equals static mud weight plus the additional pressure from annular friction losses, expressed as an equivalent fluid density at depth.
Question 5: A perforating gun is fired with an underbalanced condition. What is the main benefit of underbalanced perforating?
- Increases perforation penetration depth
- Creates immediate inflow that cleans perforation tunnels of crushed zone debris (Correct answer)
- Reduces casing damage during perforation
- Allows higher shot density
Correct answer: Creates immediate inflow that cleans perforation tunnels of crushed zone debris
Underbalanced perforating draws formation fluids into the wellbore immediately upon firing, cleaning crushed zone damage from the perforation tunnels.
Question 6: Which well control method involves pumping a heavier kill fluid down the drillpipe while holding constant casing pressure?
- Driller's method
- Wait-and-weight (engineer's) method (Correct answer)
- Volumetric method
- Bullheading
Correct answer: Wait-and-weight (engineer's) method
The wait-and-weight method mixes kill-weight mud before pumping, circulating it in one continuous cycle while holding constant casing pressure.
Question 7: What is the purpose of a packer in a production completion?
- Prevent sand production
- Isolate the tubing-casing annulus to direct production through the tubing (Correct answer)
- Stimulate the formation
- Control water-oil contact
Correct answer: Isolate the tubing-casing annulus to direct production through the tubing
A packer seals the annulus between the tubing and casing, forcing production fluids up the tubing and protecting the casing from wellbore pressures.
SPE Drilling & Well Completion 2
What is the primary purpose of a diverter system installed at the wellhead during top-hole drilling?