SPE Production and Operations 3 — Questions and Answers
Question 1: What is the main operational risk associated with hydrate formation in subsea flowlines?
- Increased corrosion rate of the pipeline
- Plugging of the flowline, potentially causing loss of production or structural damage (Correct answer)
- Reduction of crude oil API gravity
- Excessive pressure drop across the wellhead choke
Correct answer: Plugging of the flowline, potentially causing loss of production or structural damage
Gas hydrates can form ice-like plugs in subsea flowlines under high pressure and low temperature, blocking flow and risking line rupture.
Question 2: Which inflow performance relationship (IPR) model accounts for turbulent flow near the wellbore in gas wells?
- Vogel's method
- Standing's correlation
- Darcy's linear flow equation
- Forchheimer's non-Darcy flow equation (Correct answer)
Correct answer: Forchheimer's non-Darcy flow equation
Forchheimer's equation adds a velocity-squared turbulence term to Darcy's law, capturing the non-Darcy pressure drop near high-rate gas wells.
Question 3: In sucker rod pump design, what does 'fluid pound' indicate?
- Excessive gas bubbles causing the pump to strike incompressible liquid with impact (Correct answer)
- High wellhead tubing pressure causing backflow
- Rod parting due to excessive tensile stress
- Scale buildup on the pump barrel
Correct answer: Excessive gas bubbles causing the pump to strike incompressible liquid with impact
Fluid pound occurs when the pump barrel partially fills with gas so the plunger slams into liquid on the downstroke, causing mechanical shock.
Question 4: What is the purpose of a downhole safety valve (DHSV) in a production well?
- To regulate injection gas pressure in gas lift operations
- To automatically shut off well flow if surface conditions indicate loss of control (Correct answer)
- To prevent scale deposition on the tubing walls
- To measure bottomhole flowing pressure continuously
Correct answer: To automatically shut off well flow if surface conditions indicate loss of control
A DHSV (or SCSSV) closes automatically if surface equipment fails or is damaged, preventing an uncontrolled blowout from the wellbore.
Question 5: Which completion technique involves perforating multiple isolated zones and fracturing each separately in a horizontal well?
- Gravel packing
- Multi-stage hydraulic fracturing (Correct answer)
- Selective inflow control with ICD
- Coiled tubing clean-out
Correct answer: Multi-stage hydraulic fracturing
Multi-stage fracturing uses packers or plug-and-perf systems to isolate and fracture individual zones sequentially along a horizontal wellbore.
Question 6: In production chemistry, iron sulfide scale often forms when which two conditions coexist?
- High CO2 partial pressure and low pH water
- H2S gas and iron ions in the produced water (Correct answer)
- High temperature and supersaturated barium sulfate brine
- Low flow velocity and oxygen contamination
Correct answer: H2S gas and iron ions in the produced water
Iron sulfide (FeS) precipitates when H2S reacts with ferrous iron from corrosion or formation water, forming scale that can plug perforations and equipment.
Question 7: What operational parameter is typically monitored to detect liquid loading in a gas well?
- Increasing gas-oil ratio (GOR)
- Declining wellhead tubing pressure with falling production rate (Correct answer)
- Rising formation water salinity
- Increasing bottomhole temperature
Correct answer: Declining wellhead tubing pressure with falling production rate
Liquid loading manifests as a declining tubing pressure and erratic or declining gas rate as liquids accumulate and can no longer be lifted by gas velocity.
SPE Production and Operations 3
What is the main operational risk associated with hydrate formation in subsea flowlines?