Electrical Submersible Pump (ESP)

Principle of ESP

ESPs operate by connecting an electric motor directly to a centrifugal pump module. The electric motor shaft is directly linked to the pump shaft, causing the pump to rotate at the same speed as the motor. This direct connection ensures efficient energy transfer and consistent pumping performance.

ESP Components

i) Subsurface Components:

• Pump: The main component that moves fluids to the surface. The pump is a multi-staged centrifugal pump. Each stage consists of a rotating impeller and a stationary diffuser. The type of stage used determines the volume of the fluid to be produced.
• Motor: Drives the pump, typically an electric motor.
• Seal Electric Cable: Protects the electrical connections from well fluids.
• Gas Separator: Removes gas from the fluid to prevent pump damage and maintain efficiency.
  • Dynamic Gas Separator: Utilizes inducers and centrifuges (e.g., KGS) to impart energy for vapor-liquid separation.
  • Advance Gas Handler (AGH): If gas is present, an AGH is installed and attached to the pump suction to condition the gas, enhancing the pump's ability to handle gas without separating it. The AGH does not separate gas but conditions it for better pump performance by:
    • Homogenizing the mixture
    • Reducing bubble size
    • Reintegrating gas back into the liquid
    • Assisting gas movement into the main stream

ii) Surface Components:

• Motor Controller (or Variable Speed Controller): Regulates the motor's speed and power.
• Transformer: Converts electrical power to the required voltage for the motor.
• Junction Box: Provides electrical connections and protection for the system.
• Surface Electric Cable: Transmits electrical power from the surface to the subsurface motor.

ESP Applications

• Booster Service Submersible Pump Configuration: Enhances fluid production in existing wells.
• Bottom Intake Submersible Pump Configuration: Optimizes fluid intake directly from the well bottom.
• Bottom Discharge Submersible Pump Configuration: Facilitates efficient discharge of fluids from the well.
• Shrouded Submersible Pump Configuration: Protects the pump and motor in harsh well conditions.

Limitations of ESP

• Available Electric Power: Requires a reliable power source, limiting use in remote areas.
• Limited Adaptability to Major Reservoir Changes: Less flexible in responding to significant changes in reservoir conditions.
• Difficult to Repair in the Field: Repairs often require specialized equipment and expertise.
• Free Gas and/or Abrasives: Can cause pump damage and reduce efficiency.
• High Viscosity: Struggles with pumping highly viscous fluids.
• Higher Pulling Costs: Increased costs associated with installation and maintenance.

Advantages of ESP

• High Volume and Depth Capability: Effective for deep wells and high-production rates.
• High Efficiency Over 1,000 BPD: Maintains efficiency even at large production volumes.
• Low Maintenance: Requires minimal upkeep compared to other artificial lift methods.
• Minor Surface Equipment Needs: Compact surface setup reduces space and infrastructure requirements.
• Good in Deviated Wells: Performs well in wells that are not perfectly vertical.
• Adaptable in Casings > 4-1/2": Suitable for larger casing sizes, enhancing versatility.
• Use for Well Testing: Facilitates effective testing of well performance and reservoir characteristics.