Long-Stroke Pumping Unit Control to Reduce Rod Jarring
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Solution Overview
Problem
Conventional control philosophies for long-stroke pumping units, particularly hydraulic pump-jacks, are ill-suited due to their non-responsive drive mechanisms, leading to inefficiencies and potential damage from sudden acceleration of counterweight assemblies, and fail to account for the unique operational geometry of these units.
Innovation Solution
A dynamic control system for long-stroke pumping units incorporating a counterweight, electric motor, variable speed driver, sensors, and a controller that adjusts stroking parameters based on sensor measurements to optimize operation and prevent failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional drive mechanisms are used in long-stroke pumping units, then the unit can operate with standard geometry, but the drive mechanism is not responsive to speed changes and causes jarring of the rod string during turnaround
Solution Approach 1:
The patent applies dynamics by making the drive mechanism's operational characteristics variable rather than fixed. The system dynamically adjusts the speed and acceleration profiles of the counterweight assembly and rod string during operation, particularly during turnaround phases, to prevent jarring while maintaining responsiveness to speed changes. This transforms the static, inertial gear-driven system into a dynamically controllable one that can adapt its motion characteristics in real-time.
Solution Approach 2:
The patent changes key operational parameters such as speed, acceleration, and position of the counterweight assembly and rod string during the pumping cycle. By actively modifying these parameters during turnaround and other critical phases, the system achieves responsive speed control while preventing the jarring that would otherwise occur in conventional fixed-geometry units.
2Reliability
If the speed of the rod string is greatly decreased at the end of upstroke and downstroke to prevent jarring, then rod string damage is reduced, but the speed of fluid pumping decreases and well cost increases
Solution Approach 1:
The system uses dynamic control to maintain higher rod string speeds during the majority of the upstroke and downstroke while only applying speed reduction during critical turnaround phases. This dynamic speed management prevents jarring and rod string damage without significantly compromising overall fluid pumping speed and productivity.
Solution Approach 2:
The patent applies periodic action by implementing speed control specifically during the turnaround phases of the pumping cycle rather than maintaining reduced speed throughout the entire cycle. This allows the system to achieve rod string protection during critical moments while maintaining high productivity during the productive upstroke and downstroke portions of the cycle.
3Device complexity
If conventional control philosophy is used assuming historical rod dynamics, then control is simplified, but it is ill-suited for long-stroke pumping units with different operational geometry
Solution Approach 1:
The patent implements feedback control by using sensors to monitor the actual position, speed, and acceleration of the rod string and counterweight assembly, then using this information to dynamically adjust control parameters. This feedback mechanism allows the system to adapt to the specific geometry and operational characteristics of long-stroke pumping units while maintaining systematic and manageable control through automated real-time adjustments.
Solution Approach 2:
The control system performs self-service by automatically adjusting its own parameters based on real-time measurements of rod string dynamics. Rather than requiring manual tuning or complex external control, the system uses its own sensor data to automatically optimize its operation for long-stroke geometry, making the control adaptable without proportionally increasing operational complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances operational efficiency, reduces wear and tear, and prevents damage by dynamically controlling the pumping unit's stroking, thereby improving the longevity and performance of the lifting system.
Implementation Method 1
an electric motor configured to reciprocate the rod string
Implementation Method 2
a counterweight assembly movable along the tower
Data Source
AI summary
A long-stroke pumping unit includes a tower; a counterweight assembly movable along the tower; a crown mounted atop the tower; a sprocket supported by the crown and rotatable relative thereto; and a belt. The unit further includes a motor having a stator mounted to the crown and a rotor torsionally connected to the sprocket; and a sensor for detecting position of the counterweight assembly. The pumping unit may include a dynamic control system for controlling a speed of a motor.