Sucker-Rod Pump Drive

1 Sucker-Rod Pump DriveSRPSRPS ucker-RodPump DriveUnico's Sucker-Rod Pump Drive (SRP ) provides superior control of conventional,air-balanced, beam-balanced, phased-crank, Mark II, Reverse Mark, and Rotaflexartificial lifts. The Drive integrates motor control, speed optimization, logic, pump fillcontrol, and rod load control into a single, compact solution that increases production,improves energy efficiency, and enhances the reliability of both new and existingpumping Constraint OptimizationAt any instant during the life of a well, and even within a pump cycle, there is a singleconstraint that limits production.

2 Production can be maximized without compromisingefficiency or reliability by forcing the system to operate at the particular constraintlimiting production at each instant of time. Determining the applicable limits andmoving smoothly between them in real time is a key advantage of the Unico of all the system elements are run in real time at the wellhead to detectappropriate limits and enforce associated control strategies. At different points inthe pump cycle, the system may be limited by maximum motor speed, motorthermal capacity, power demands, gearbox maximum torque, rod maximum load,rod fall velocity, or pump fill.

3 Multiple constraint optimization is particularly beneficialin applications with variable inflow conditions, such as those found in coal-bedmethane, high gas/oil ratio, and thermally stimulated ModelingEmbedded mathematical models of Drive , motor, pump unit, rod string, pump, flowline, tubing, casing,fluid, and reservoir use component specifications and wellcompletion information along with field setup parameters to monitor pumping routines automatically determine installation-dependentsystem parameters, including those of the electric motor, pumping unit, rod string,and downhole pump.

4 The models capture the thermal, mechanical, electrical,and hydraulic behavior of the pumping system to control the pumping processwith greater precision than ever OperationThe Drive uses a number of unique methods for precisely determining polishedrod and downhole pump position, velocity, and load without requiring externalrod position or load sensors. These sensorless system variables can be observedthrough monitor displays or recorded as time-based graphical plots of motorvelocity, motor torque, pump speed, gearbox torque, rod velocity, rod position,rod load, pump velocity, pump position, and pump load, as well as dynamometerplots of surface and downhole Pump Speed ControlThe Drive provides a number of options for controlling pump speed.

5 Speed commandscan be selected from a number of sources, including potentiometer adjustments,keypad presets, serial data communications, and internal optimization , dual-, and triple-speed control options allow pump upstroke, downstroke,and cornering speeds to be adjusted independently. Rotaflex corneringspeedcontrol automatically calculates braking distances to get from straightaway tocornering speeds as well as points for accelerating out of the corners. The motorcan be operated at up to twice base speed at constant power. This allows theoverall gear ratio to be increased, thereby providing increased low-speed torquewhile smoothing gearbox torque at high pumping Fill ControlThe Drive accurately determines and regulates the percentage of pump fill withoutrequiring separate sensors or control hardware.

6 Rather than simply stop a pumpcompletely during a pump-off condition, the Drive adjusts upstroke and downstrokespeeds to maintain a target fill value and maximize production. This allows the pumpto automatically adapt to changing well inflow characteristics. This control eliminatesfluid pound, reduces peak rod load, prevents standstill sand infiltration,eliminatesstresses associated with start/stop cycling, and improves pumping efficiency byreducing viscous friction. In optimize mode, the Drive automatically slows down priorto fluid impact for a soft landing. A pump-off controller allows the pump to dwellfor a period for wells with low inflow.

7 The off time is optimally selected by the dwell period minimumpump speed can be used to prevent sanding in the Load ControlA rod string calculator establishes rod load and resonance parameters forcontinuous, coupled, straight, and tapered rod configurations. Rod load is correctedfor deviated completions, and rod friction is automatically identified. Rod and pumpmonitors continuously measure and display polished rod and downhole pumploads, velocities, and positions. Rod force can be measured directly from a loadcell or internally computed without the need for external instrumentation.

8 A rodload limiter automatically adjusts downstroke speed to eliminate rod float bymaintaining minimum road load while maximizing production. Independent maximumand minimum rod load limits can be preset to reduce rod stress. Rod load dampingcan be used to suppress oscillatory rod force excursions and improve the efficiencyof the pumping system without the need for specific rod load Separation ControlA bridle separation limiter prevents rod float by automatically adjusting downstrokespeed for minimum rod load. A limit switch can be used to detect bridle separationto automatically correct the pump speed and record a separation GeneratorA motor torque monitor and pumping-unit geometry are used in place of a loadcell to plot actual surface dynamometer graphs using either a personal computeror smart phone.

9 No external load cell is required. The Drive also estimatesdown-hole pump stroke and pump flow. Predicted surface and downhole dynamometergraphs are available for diagnosing well and pump problems on Monitoring and ControlThe Drive provides detailed information on energy usage within the pumping system,including system input power, motor output power, polished rod power, and pumplift power. An input power meter displays cumulative energy consumption, whilea pumping efficiency monitor shows the effectiveness of input energy utilizationfor production of useful lift work.

10 Peak and regenerative power limiters allow themaximum and regenerative power supplied by the Drive to be conserved. Power flowcontrol can be used to smooth power flow, reduce gearbox stress, and increase theefficiency of the pumping without specifying specific pump power limits. A power flowoptimizer maximizes production for highly variable inflow conditionsby operatingthe Drive and motor at their maximum thermal capacities. Special provisionsoptimize performance with generators and solar cells in alternative power Pump DriveSRPO verview(continued) Sucker-Rod Pump DriveSRPO verview(continued)Production MonitorsA pump flow monitor provides a continuous estimate of flow without the need foradditional instrumentation.