Module 4: Progressive Cavity Pumps (PCP)

Helical rotor • Elastomer stator • Viscous fluids & solids handling.

⏱ 50–60 minutes🎯 Beginner–Intermediate🎁 Free

🎯 Learning Objectives

  • Explain PCP displacement principles and slip behavior.
  • Select stator elastomer grades based on temperature & fluids.
  • Compare top-drive, ground-drive, and ESPCP configurations.
  • Identify torque, dogleg severity, and solids limits in design.

📘 Key Terms

Displacement Slip Elastomer swell Torque Dogleg severity (DLS) ESPCP

📎 Prerequisite

Module 3 — Electrical Submersible Pumps (ESP)
Time: ~50–60 min Level: Beg–Int Format: Reading + configs + quiz

ℹ️ What & Why

PCPs use a single-helix metallic rotor turning inside a double-helix elastomer stator. Cavities progress axially, conveying fluid with low shear—ideal for viscous, sand-laden, or emulsified production where other lift methods struggle.

⚙️ Principles of Operation

  • Displacement is set by geometry; rate scales with RPM × displacement × efficiency.
  • Slip increases with ΔP and wear; higher viscosity lowers slip.
  • Continuous free gas reduces volumetric efficiency and increases heat.

🧩 System Components

  • Rotor: chrome-plated/coated; corrosion & abrasion resistant.
  • Stator: elastomer (HNBR/FKM/NBR blends) selected for temperature, aromatics, H2S/CO2, and swell.
  • Drive: Top-drive (surface motor + rod string), Ground-drive (gear reducer at wellhead), or ESPCP (downhole motor).
  • Surface/VSD: RPM control, torque monitoring, and backspin braking.

📏 Operating Considerations

💡
Field Tip
Ramp RPM slowly after startups; verify intake pressure and temperature to avoid elastomer blistering.
⚠️
Common Pitfall
High dogleg severity causes rod wear and stator damage in top-drive PCPs—use tapered rods, guides, and conservative RPM.

🧪 Worked Example — Estimating PCP Rate

Formula

Q ≈ (Displacement per rev) × RPM × ηvol

Given: Displacement = 0.12 bbl/rev; RPM = 200; ηvol=0.8 (20% slip).

Compute: Q ≈ 0.12 × 200 × 0.8 = 19.2 bbl/h → ×24 ≈ ~460 bpd.

Adjust for temperature-dependent elastomer swell, solids wear, and produced-gas fraction.

🧩 Configuration Patterns

Standard PCP Layout

Baseline arrangement with PCP intake at the pump and discharge up the tubing. Works in most vertical and moderate-deviation wells when intake submergence is adequate and free gas is manageable. Best suited to viscous, solids-laden fluids with low shear requirements.

Standard PCP configuration: rotor/stator downhole with discharge to tubing
Figure 4.1 — Standard PCP arrangement.

Top-Driven PCP (Surface Motor + Rod String)

A surface motor and VSD rotate a sucker-rod string that drives the rotor. Simple surface maintenance and good for shallow to medium depths. Watch rod/tubing wear in deviated sections; manage backspin with braking and use tapered rods and guides where DLS is high.

Top-driven PCP with surface motor driving rod string
Figure 4.2 — Top-driven PCP.

Ground-Drive PCP (Wellhead Gear Reducer)

A gear reducer at the wellhead transmits torque to the rod string with smoother rotation and reduced torsional oscillations—useful on longer strings and higher torque applications. Heavier wellhead and seal maintenance are trade-offs.

Ground-drive PCP with wellhead gearbox
Figure 4.3 — Ground-drive PCP.

ESPCP (Downhole Motor + PCP)

The PCP is driven by a downhole motor—no rod string—improving reliability in deviated/horizontal wells. Powered via cable and controlled by a VSD like ESPs. Consider motor cooling, solids tolerance at the intake, cable protection, and retrieval complexity.

ESPCP configuration with downhole motor driving PCP
Figure 4.4 — ESPCP layout (no rod string).

✅ Quick Knowledge Check

1) Which factor most directly reduces PCP slip?
More viscous fluids leak less through clearances, reducing slip.
2) In top-drive PCPs, which risk rises with high dogleg severity?
Bending cycles and contact increase at high DLS, accelerating wear.
3) ESPCP is preferred over top-drive PCP mainly because…
No rod string reduces wear in deviated wells; rates depend on design.

🧾 Summary & Takeaways

  • PCPs excel in viscous, solids-laden production with low shear.
  • Rate ≈ displacement × RPM × η; slip ↑ with ΔP and wear, ↓ with viscosity.
  • Elastomer choice is critical—match chemistry & temperature to fluids.
  • Top-drive vs. ground-drive vs. ESPCP: choose for deviation, torque, and surface layout.
  • Monitor torque, temperature, and vibration; ramp RPM conservatively.

➡️ What’s Next

Up next: Module 5 — Gas Lift Systems
Suggested prep: review free-gas handling and compressor basics.
Go to Module 5 →
Last updated: Aug 2025 • Author: Atlas ESP Academy
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