SPE Artificial Lift Systems 2 — Questions and Answers
Question 1: In a sucker rod pumping system, what does the term 'fluid pound' refer to?
- Excessive pump speed causing fluid hammer
- The pump plunger striking liquid with incomplete barrel fill (Correct answer)
- High wellbore pressure damaging the pump barrel
- Fluid leaking past the traveling valve
Correct answer: The pump plunger striking liquid with incomplete barrel fill
Fluid pound occurs when the pump barrel is not fully filled with liquid, causing the plunger to impact the fluid surface violently on the downstroke.
Question 2: Which artificial lift method is most suitable for high gas-liquid ratio (GLR) wells with deviated wellbores?
- Sucker rod pump
- Progressive cavity pump (PCP)
- Electric submersible pump (ESP)
- Plunger lift (Correct answer)
Correct answer: Plunger lift
Plunger lift is well-suited for high-GLR deviated wells because it uses the natural gas energy to lift a plunger slug of liquid to surface.
Question 3: What is the primary advantage of a gas-lift mandrel with a side-pocket configuration?
- Higher injection pressure capability
- Ability to retrieve and replace valves without pulling the tubing string (Correct answer)
- Larger gas injection orifice diameter
- Reduced annular pressure requirements
Correct answer: Ability to retrieve and replace valves without pulling the tubing string
Side-pocket mandrels allow gas-lift valves to be kicked over and retrieved by wireline without pulling the tubing, enabling workover-free valve changes.
Question 4: In ESP design, what does the term 'pump intake pressure' (PIP) represent?
- Surface wellhead pressure measured at the pump motor
- Bottomhole flowing pressure at the pump suction inlet (Correct answer)
- Pressure differential across the pump stages
- Maximum rated pressure of the pump housing
Correct answer: Bottomhole flowing pressure at the pump suction inlet
Pump intake pressure (PIP) is the flowing bottomhole pressure measured at the ESP pump suction, which determines the available net positive suction head.
Question 5: For a progressive cavity pump (PCP), what determines the volumetric displacement per revolution?
- Motor speed and torque output
- Rotor eccentricity and stator pitch length (Correct answer)
- Tubing diameter and pump setting depth
- Drive rod length and tensile strength
Correct answer: Rotor eccentricity and stator pitch length
PCP displacement per revolution is determined by rotor eccentricity and stator pitch length, which define the cavity volume swept per turn.
Question 6: Which gas-lift valve type opens when the casing (annulus) pressure exceeds a set value and is primarily used as an unloading valve?
- Production pressure-operated (PPO) valve
- Casing pressure-operated (CPO) valve (Correct answer)
- Differential pressure valve
- Throttling valve
Correct answer: Casing pressure-operated (CPO) valve
Casing pressure-operated (CPO) valves open when annulus injection pressure exceeds the bellows charge pressure, making them ideal for unloading operations.
Question 7: What is the purpose of a 'Y-tool' configuration in an ESP installation?
- To direct produced fluid through dual tubing strings
- To allow wireline access past the ESP for well intervention below the pump (Correct answer)
- To split electrical power between redundant motors
- To recirculate gas-laden fluid around the pump intake
Correct answer: To allow wireline access past the ESP for well intervention below the pump
A Y-tool bypasses the ESP string, providing a wireline access path to the perforations or below the pump for logging or other interventions without pulling the ESP.
SPE Artificial Lift Systems 2
In a sucker rod pumping system, what does the term 'fluid pound' refer to?