Sucker Rod Stress Calculation via Finite Difference Nodes
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Solution Overview
Problem
Sucker rod pumping systems face challenges in accurately monitoring pump fillage and controlling stress along the rod string, leading to potential failures due to uncertainty in inflow and stress distribution, which can result in suboptimal well production and increased failure rates.
Innovation Solution
A method and system for calculating stress values at finite difference nodes along a sucker rod string using measured rod displacement and load data, employing the Modified Everitt-Jennings algorithm and cubic spline interpolation to determine stress at any depth, enabling accurate stress analysis and prevention of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional stress calculation methods are used for sucker rod pumping systems, then the system design is simpler, but the accuracy of stress monitoring and failure prediction is insufficient
Solution Approach 1:
The patent replaces traditional mechanical stress analysis methods with a computational approach using the Modified Everitt-Jennings algorithm. This algorithm uses measured rod displacement and load data to calculate stress values at finite difference nodes, substituting complex mechanical modeling with a more accurate numerical method that can be implemented through sensors and processors.
Solution Approach 2:
The patent introduces finite difference nodes as intermediary calculation points along the sucker rod string. These nodes serve as mediators between the measured rod displacement/load data and the final stress distribution results, enabling precise stress calculation at any depth by dividing the rod string into discrete segments for numerical analysis.
2Reliability
If detailed stress analysis at any depth is implemented, then the reliability of the sucker rod system is improved, but the complexity of data processing and calculation increases
Solution Approach 1:
The patent divides the continuous sucker rod string into discrete finite difference nodes along its length. This segmentation allows stress to be calculated at multiple specific points rather than requiring continuous analysis, making the problem computationally manageable while still providing detailed stress distribution information at any depth for improved reliability assessment.
Solution Approach 2:
The patent uses measured rod displacement and load data from sensors as feedback inputs to the Modified Everitt-Jennings algorithm. This feedback mechanism continuously updates the stress calculations based on actual operating conditions, enabling real-time monitoring and prediction of rod failure risks while managing data processing complexity through established computational procedures.
3Measurement precision
If the Modified Everitt-Jennings algorithm with finite difference nodes is used, then the stress distribution accuracy is improved, but the computational requirements and processing time increase
Solution Approach 1:
By segmenting the rod string into finite difference nodes, the patent transforms a continuous differential equation problem into a discrete numerical calculation problem. This segmentation enables the use of the Modified Everitt-Jennings algorithm to achieve high stress distribution accuracy while keeping computational requirements manageable through standardized numerical procedures that can be efficiently implemented.
Data Source
AI summary
Techniques and apparatus are provided for stress calculations for sucker rod pumping systems. A method is provided for determining stress along a sucker rod string disposed in a wellbore. The method generally includes receiving, at a processor, measured rod displacement and rod load data for the sucker rod string, wherein the sucker rod string comprises a plurality of sections; and calculating stress values at a plurality of finite difference nodes for at least one of the plurality of sections based, at least in part, on the measured rod displacement and rod load data.