Rod Lift - UniStar Downhole Protection VSD System | Schlumberger

UniStar

Downhole protection variable speed drive system

Maximize rod lift performance

Maximize production and equipment performance through the sophisticated modeling of the UniStar downhole protection variable speed drive (VSD) system that makes use of all available parameters, with particular focus on protecting downhole equipment.

At any instant during well operations, in particular within a pump cycle, there is a single constraint that limits production. Production can be maximized by “automating” the system to operate at the particular limiting constraint at each instant of time. Determining the applicable limits and operating smoothly across them in real time is the key differentiator of the UniStar system.

Downhole equipment protection

Polished rod and downhole pump loads, velocities, and positions are continuously measured and displayed. Downstroke speed is automatically adjusted to eliminate rod float, a potential source of equipment problems. Rod load limits can be preset to reduce stress, while load damping can be used to suppress oscillations and improve pumping system efficiency without the need for specific limits.

UniStar VSD
UniStar downhole protection VSD system optimizes production and maximizes efficiency and reliability.
UniStar downhole protection variable speed drives are now part of Sensia.
To learn more visit www.sensiaglobal.com.
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UniStar VSD
Various key parameters and event logs can be displayed at the wellsite or accessed remotely.

Improved energy management

Cumulative energy consumption and the effectiveness of input energy in delivering useful lift work are continuously monitored and considered. Power limiters allow the maximum and regenerative power supplied by the drive to be conserved. The UniStar system instructs power flow control to smooth power flow, reduce gearbox stress, increase pumping efficiency, and maximize production for highly variable inflows.

Pump fill optimization

Managing pump fill is important to protect downhole equipment. The UniStar system accurately determines and regulates the percentage of pump fill. Rather than stop a pump completely during a pumpoff condition, the system adjusts upstroke and downstroke speeds to maintain a target fill value and maximize production. This allows the pump to automatically adapt to changing well inflows, eliminating fluid pound, reducing peak rod load, preventing standstill sand infiltration, eliminating stresses associated with start/stop cycling, and improving pumping efficiency.

Sensor-free operation

A number of unique methods precisely determine polished rod and downhole pump position, velocity, and load without requiring external sensors. A range of system variables can be observed through monitor displays or recorded as time-based graphical plots. For operators who prefer to minimize sensors, the UniStar system is able to optimize performance across a range of operating conditions.

Gearbox protection

Gearbox torque is monitored and can be limited by the UniStar system to protect against damaging overload conditions. Excessive drive belt slippage or breakage is quickly detected, while a starting-torque manager eliminates inrush currents and extends the life of the system by reducing the violence associated with starting the pump. A counterbalance monitor and associated counterbalance assistant make it easy to adjust the counterweights to minimize gearbox stress and energy consumption.

UniStar VSD
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