Electric Submersible Pump (ESP) Product

Overview

When a reservoir can no longer push oil to surface on its own pressure, the well needs artificial lift, and for high-volume wells the electric submersible pump dominates: roughly one in five producing oil wells worldwide runs one. The entire machine — pump, gas separator, seal section, motor and gauge — is a slim tandem typically 10–30 m long and under 14 cm in diameter, bolted together and hung on the production tubing thousands of meters down the casing, with power arriving through an armored cable strapped to the tubing. Everything about the design follows from one constraint: the well casing fixes the diameter, so capability must come from length.

The string, bottom to top

At the bottom hangs the Downhole Sensor Sub, a gauge that telemeters intake pressure, motor temperature and vibration to surface by superimposing a DC signal on the power conductors through its Telemetry Module — no dedicated signal wire exists.

Above it, the Downhole Motor is a two-pole induction machine stretched to fit the hole: a wound Motor Stator up to 10 m long, with several short Rotor Section stacked on the shaft and a bearing between each because a single long rotor would whip. The motor is flooded with Motor Dielectric Oil for insulation and heat transfer, and it has no cooling system of its own — it relies on produced fluid flowing up past the housing, which is why an ESP must never be set below the perforations without a shroud, and why a well that stops flowing cooks its own motor. Power enters at the Pothead Connector, statistically the weakest electrical point in the string.

The Seal Section (Protector) sits between motor and pump and does three jobs: its Elastomer Expansion Bag and Labyrinth Chamber stages let the motor oil breathe with temperature while keeping well fluid out; its Mechanical Face Seal seal the spinning shaft in series-redundant stages; and its Protector Thrust Bearing absorbs the tonnes of downthrust generated by the pump stack. Most "motor failures" begin here, as seal degradation lets conductive well fluid migrate down into the windings.

The Intake & Gas Separator admits fluid through screened Intake Ports; in gassy wells a Rotary Gas Separator centrifuges out up to ~90% of free gas and vents it to the annulus via the Crossover Sub, because a centrifugal stage handling much more than 10–15% free gas loses head and eventually gas-locks.

The Multistage Pump Section itself is brute-force repetition: each Pump Impeller and Stage Diffuser pair adds only 5–8 m of head, so a 2,000 m lift takes hundreds of stages in stacked Pump Housing sections, with carbide Stage Bearing spaced along the Pump Shaft to survive sand-laden fluid. The Discharge Head threads to the tubing and the flow path to surface.

Power delivery

The Round Power Cable runs the full well depth — EPDM insulation, lead sheath against gas permeation, galvanized armor against the trip in and out — and necks down to a flat Motor Lead Extension where it must squeeze through the annulus beside the pump. Steel Cable Band every 4.5 m strap it to the tubing. At surface it passes through the wellhead in a pressure-sealed Wellhead Penetrator to a vented Vented Junction Box (venting matters: gas migrating up the cable has exploded drive cabinets), then to the Step-Up Transformer and Variable Speed Drive. Variable-speed operation, sweeping 35–70 Hz, lets the operator match pump rate to well inflow; running a fixed speed against a declining well drags the pump off its curve into downthrust wear or cycling.

Run life

An ESP cannot be repaired in place — every failure means a workover rig and a full string replacement, often costing more than the equipment itself. Median run life is two to five years; dismantle inspections per API RP 11S1 attribute most failures to the electrical system (cable, pothead, windings), with abrasion and scale on the pump stack next. The downhole gauge and Pump Controller exist mainly to stretch that number: underload trips catch gas locking and pump-off, winding temperature trends flag cooling loss, and vibration picks up wear months before failure.