SPE Production Operations & Optimization 3 — Questions and Answers
Question 1: What does the Vogel equation describe in petroleum engineering?
- Pressure drop across a choke valve
- Inflow performance for solution-gas-drive reservoirs (Correct answer)
- Gas flow rate through a orifice meter
- Pressure transient response after a buildup test
Correct answer: Inflow performance for solution-gas-drive reservoirs
The Vogel equation provides an empirical dimensionless IPR relationship for solution-gas-drive reservoirs, relating flow rate to bottomhole flowing pressure.
Question 2: A surface processing facility is experiencing emulsion problems that increase treating time. Which chemical injection approach at the wellhead most effectively addresses this?
- Scale inhibitor injection
- Demulsifier injection (Correct answer)
- Corrosion inhibitor injection
- Biocide injection
Correct answer: Demulsifier injection
Demulsifiers injected at the wellhead break water-in-oil or oil-in-water emulsions before they reach the separator, reducing surface treating time.
Question 3: Which production optimization method involves temporarily shutting in low-productivity wells to raise reservoir pressure and then reopening them for improved production?
- Huff-and-puff stimulation
- Production cycling (Correct answer)
- Rate acceleration
- Pressure pulsing
Correct answer: Production cycling
Production cycling—periodically shutting in marginal wells—allows pressure buildup that can improve inflow when the well is reopened, extending economic life.
Question 4: In ESP system design, what is the significance of the pump's Best Efficiency Point (BEP)?
- It defines the maximum head the pump can generate
- It is the flow rate at which the pump operates with maximum efficiency and reliability (Correct answer)
- It marks the onset of cavitation in the pump stages
- It identifies the minimum frequency for variable speed drive operation
Correct answer: It is the flow rate at which the pump operates with maximum efficiency and reliability
Operating an ESP at or near its BEP minimizes vibration and heat generation, maximizing efficiency and extending pump run life.
Question 5: What is the primary purpose of a subsurface safety valve (SSSV) in a production well?
- To control water coning by restricting downhole flow rate
- To shut in the well in an emergency to prevent uncontrolled surface flow (Correct answer)
- To separate gas from oil downhole before entering the tubing
- To maintain minimum bottomhole pressure above bubble point
Correct answer: To shut in the well in an emergency to prevent uncontrolled surface flow
SSSVs are fail-safe valves installed in the tubing that automatically close if surface control pressure is lost, preventing blowouts.
Question 6: During a production test, a well shows a declining PI over successive flow periods with no skin increase. What is the most probable explanation?
- Mechanical skin from perforation damage
- Pressure-dependent permeability due to reservoir compaction (Correct answer)
- Chemical scale deposition on perforations
- Emulsion blocking near the wellbore
Correct answer: Pressure-dependent permeability due to reservoir compaction
In compacting reservoirs, permeability decreases as effective stress increases with pressure depletion, causing a genuine PI decline unrelated to skin.
Question 7: In gas lift design, what is the purpose of the unloading valves above the operating valve?
- They remain open continuously to supplement gas injection
- They allow the well to be unloaded of kill fluid during startup and then close sequentially (Correct answer)
- They act as backup operating valves if the primary fails
- They regulate injection pressure to prevent overinjection
Correct answer: They allow the well to be unloaded of kill fluid during startup and then close sequentially
Unloading valves open sequentially during well startup to displace completion fluid, then close as injection gas transfers to the deeper operating valve.
SPE Production Operations & Optimization 3
What does the Vogel equation describe in petroleum engineering?