Artificial Lift Pump Speed Control for Under Pumping Mitigation
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Solution Overview
Problem
Existing artificial lift systems face challenges in detecting and mitigating under pumping conditions, which can lead to reduced production rates, increased water cut, equipment damage, and increased operating costs.
Innovation Solution
The system includes a sucker rod pump connected to a sucker rod, a beam pumping assembly with a variable speed motor, and a controller that determines the pump fillage level and fluid level in the annulus to adjust the pumping speed and mitigate under pumping conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the maximum operating speed of the pump is limited to optimize equipment life, then equipment wear and stress are reduced, but under pumping conditions occur leading to reduced production rates and increased water cut
Solution Approach 1:
The system dynamically adjusts the pump operating speed based on real-time monitoring of fluid level and pump fillage. The controller continuously varies the speed within the predetermined maximum limit to maintain optimal pump fillage and prevent under pumping conditions, thereby maintaining high production rates without exceeding equipment stress thresholds.
Solution Approach 2:
The system implements a feedback control mechanism where surface measurements (pump fillage level and fluid level in the annulus) are continuously monitored and fed back to the controller. The controller uses this feedback to adjust the pump speed in real-time, ensuring the pump operates at the highest safe speed that prevents under pumping and maintains optimal production.
2Productivity
If the pump operating rate is increased to match reservoir production rate, then production rates are improved, but equipment wear and stress increase
Solution Approach 1:
The system uses dynamic speed adjustment rather than fixed high-speed operation. The pump speed is continuously varied based on actual reservoir production rate and pump fillage conditions, allowing the system to operate at high speeds when necessary while reducing speed to prevent equipment stress, thereby maintaining high productivity without excessive wear.
Solution Approach 2:
The system changes the operating parameters (speed) based on monitored conditions. By adjusting the pump speed parameter in real-time according to pump fillage and fluid level measurements, the system optimizes the balance between production rate and equipment stress, operating at higher speeds when conditions permit and reducing speed when approaching stress limits.
3Difficulty of detecting and measuring
If surface measurements are used to detect under pumping conditions, then detection capability is improved, but measurement precision is insufficient due to lack of clear correlation with under pumping state
Solution Approach 1:
The system introduces pump fillage level as an intermediary measurement that indirectly indicates under pumping conditions. Instead of relying on direct fluid level measurements at the surface which have poor correlation, the system measures pump fillage (the volume of fluid in the pump barrel during the stroke) which provides a more precise indirect indicator of reservoir fluid supply and under pumping conditions.
Solution Approach 2:
The system replaces direct mechanical measurement of fluid level in the wellbore with measurement of pump fillage using surface-based sensors and pressure transducers. This substitution allows detection of under pumping conditions through pressure differential measurements across the pump, providing sufficient measurement precision without requiring direct downhole fluid level measurement.
Data Source
AI summary
An apparatus and method for use in an artificial lift system to provide under pumping mitigation functionality in which a sucker rod pump's pumping speed is adjusted through the use of a controller that determines whether: (a) the fillage level of the pump is equal to or above a pre-determined fillage level and (b) whether the fluid level in the wellbore in which the pump is positioned is not decreasing and increases the pumping rate of the pump if, over a given period, both (i) the fluid level is not decreasing and (ii) the pump fillage level is above the predetermined fillage level.