SPE Drilling & Well Completion 3 — Questions and Answers
Question 1: During a pressure test of a casing string, what does a 'pressure bleed-off' observed after shutting in the pump typically indicate?
- The casing passed the test
- A leak in the casing, connection, or shoe (Correct answer)
- Normal pressure equalization with formation
- Thermal expansion of mud
Correct answer: A leak in the casing, connection, or shoe
Pressure bleed-off after pumping stops indicates a leak path in the casing system, which fails the integrity test.
Question 2: What drilling fluid property is most critical for preventing differential sticking?
- Plastic viscosity
- Yield point
- Filter cake quality and thickness (Correct answer)
- pH level
Correct answer: Filter cake quality and thickness
A thin, low-permeability filter cake reduces the contact area and friction coefficient that cause differential sticking against permeable formations.
Question 3: In hydraulic fracturing, what is the 'closure stress'?
- Pressure required to initiate a fracture
- Minimum horizontal stress that acts to close an induced fracture (Correct answer)
- Friction pressure loss in the fracture
- Net pressure inside the fracture
Correct answer: Minimum horizontal stress that acts to close an induced fracture
Closure stress equals the minimum principal stress perpendicular to the fracture plane and is the pressure at which an induced fracture closes after pumping stops.
Question 4: What is the function of a float collar installed above the float shoe during primary cementing?
- Prevent cement from contaminating pay zones
- Provide a secondary check valve to prevent cement backflow and act as a landing seat for wiper plugs (Correct answer)
- Increase cement slurry density
- Guide the casing to bottom
Correct answer: Provide a secondary check valve to prevent cement backflow and act as a landing seat for wiper plugs
The float collar contains check valves that prevent backflow of cement up the casing and serves as a landing seat for the top wiper plug.
Question 5: Which log is most commonly used to evaluate cement bond quality behind casing?
- Gamma ray log
- Resistivity log
- Cement bond log (CBL) (Correct answer)
- Caliper log
Correct answer: Cement bond log (CBL)
The cement bond log uses acoustic attenuation to assess the quality of the cement-casing and cement-formation bonds.
Question 6: A kick is detected while drilling. Which surface indicator is typically the FIRST to be observed?
- Increase in mud pit volume (Correct answer)
- Decrease in pump pressure
- Increase in rate of penetration
- Change in mud weight
Correct answer: Increase in mud pit volume
An increase in mud pit volume is usually the first and most reliable kick indicator, as formation fluids entering the wellbore displace mud at surface.
Question 7: What is the purpose of 'wash over' operations in fishing?
- Clean the borehole of cuttings
- Mill or wash over stuck fish to free it by removing surrounding formation or debris (Correct answer)
- Pump cement around the fish
- Circulate kill-weight mud around fish
Correct answer: Mill or wash over stuck fish to free it by removing surrounding formation or debris
A washover tool mills or washes material stuck around the fish, creating an annular space that allows the fish to be retrieved.
SPE Drilling & Well Completion 3
During a pressure test of a casing string, what does a 'pressure bleed-off' observed after shutting in the pump typically indicate?