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API Bull 11L2-1969 (1999) – Catalog of Analog Computer Dynamometer Cards: Technical Overview
A Comprehensive Guide to Using API Bulletin 11L2 for Sucker Rod Pump System Analysis and Diagnostics
API Bulletin 11L2 (originally issued in 1969 and reaffirmed in 1999) is a foundational document in the field of sucker rod pumping analysis. It presents a comprehensive catalog of analog computer–generated dynamometer cards, which graphically depict the relationship between polished rod load and displacement under various operational conditions. This technical article examines the scope, key data categories, practical applications, and historical significance of Bulletin 11L2 in petroleum production engineering.
Scope and Purpose of API Bull 11L2
API Bull 11L2 was developed to provide engineers with a reference collection of dynamometer cards produced via analog computer simulation of the sucker rod pumping system. The catalog includes cards representing both normal and abnormal pumping conditions, enabling users to visually compare and diagnose the behavior of rod pump installations. The scope of the bulletin includes:
- Classification of cards by pump fillage, gas interference, valve leakage, rod friction, and other operational anomalies.
- Cards covering a range of pumping speeds (strokes per minute) and well depths.
- Simulations based on standard API rod string sizes and grades (C, D, K).
- Cards for common pumping unit geometries (conventional, air-balanced, etc.).
The primary purpose is to offer a visual baseline for interpreting field dynamometer traces, helping engineers identify pumping inefficiencies and mechanical problems without requiring access to full computer modeling in the field.
Technical Data and Organization of the Catalog
The catalog within Bulletin 11L2 is organized into condition groups, each containing numerous cards that vary parameters such as pumping speed, plunger diameter, pump depth, and fluid fillage. The analog computer used a dynamic model based on the one-dimensional wave equation, solving for the polished rod load and position over the pumping cycle. Key characteristics of each card are summarized in the following table:
| Condition Group | Representative Parameters | Typical Card Characteristics |
|---|---|---|
| Full Pump | Speed 8–16 SPM, fillage 100% | Near-rectangular shape; maximum load at top of stroke |
| Gas Interference | Fillage 40–80%, low gas fraction | Rounded corners; gradual load transition |
| Fluid Pound (Incomplete Fillage) | Fillage 20–60% | Sharp load drop during downstroke; reduced card area |
| Plunger or Valve Leakage | Varies by severity | Asymmetric shape; reduced area |
| Rod or Tubing Friction | Varies | Distorted shape; slanted sides |
Each card includes the simulated load and position data at small increments, and the bulletin provides guidance on how to interpret deviations from the full pump condition.
Application in Field Diagnostics and System Optimization
Field engineers traditionally use the printed catalog as a reference library to compare with actual dynamometer cards captured in the field. The process typically involves:
- Conducting a dynamometer run on the well.
- Obtaining a polished rod load vs. position trace (dynamometer card).
- Comparing the shape, load levels, and area of the card against the examples in Bull 11L2.
- Identifying the most likely condition (e.g., gas interference, leaking standing valve).
- Determining and implementing corrective actions (e.g., adjusting pump speed, replacing valves).
Best Practice: Use Bull 11L2 cards as qualitative references and training aids. Combine with modern digital analysis tools for quantitative diagnosis and to account for well-specific parameters.
Limitations: The analog computer cards assume idealized conditions (straight vertical well, constant damping factor, single-phase fluid). They may not accurately represent wells with viscous crude, deviated holes, severe rod friction, or multiphase flow. Always consider well-specific data.
Despite these limitations, Bulletin 11L2 remains a valuable educational resource and is often cited alongside API RP 11L (Recommended Practice for Design Calculations for Sucker Rod Pumping Systems) and API RP 11S (Operation, Maintenance, and Troubleshooting of Sucker Rod Pumping Systems).
Compliance Notes and Document History
API Bull 11L2 was originally published in 1969. It was reaffirmed in 1999, indicating that its content was considered technically valid at that time. While later standards (e.g., API 11L, API 11S, API 11W) have expanded and in some cases superseded parts of the knowledge covered, the 1969 (1999 scan) version of Bull 11L2 continues to be referenced as a historical and pedagogical tool.
Compliance considerations include:
- The bulletin cannot be used for design calculations; it is exclusively a diagnostic aid.
- It does not replace the need for modern dynamometer data acquisition and analysis.
- Users must be aware that the catalog is based on analog simulation assumptions (constant damping, uniform rod taper, etc.) that may not hold in all field conditions.
Warning: Do not rely solely on Bull 11L2 for critical operational decisions without field validation. Use it as a preliminary guide and confirm findings with digital analysis or other diagnostic methods.
For full system compliance, operators should follow API RP 11L for design and API RP 11S for operation and maintenance. Bulletin 11L2 is best used in conjunction with these and other contemporary standards.
Frequently Asked Questions
Q: What is an analog computer dynamometer card?
A: It is a graphical representation of polished rod load versus displacement, generated by an analog computer simulation of the sucker rod pumping system. The card visualizes the mechanical behavior at the surface over one complete pumping cycle.
A: It is a graphical representation of polished rod load versus displacement, generated by an analog computer simulation of the sucker rod pumping system. The card visualizes the mechanical behavior at the surface over one complete pumping cycle.
Q: How does API Bull 11L2 help in field operations?
A: The bulletin provides a catalog of typical card shapes corresponding to different pump conditions (full pump, gas interference, fluid pound, etc.). Field engineers compare actual cards to these references to diagnose issues and plan corrective measures.
A: The bulletin provides a catalog of typical card shapes corresponding to different pump conditions (full pump, gas interference, fluid pound, etc.). Field engineers compare actual cards to these references to diagnose issues and plan corrective measures.
Q: What are the limitations of using these catalog cards?
A: The cards are based on idealized analog models with specific assumptions (straight well, constant damping, single-phase fluid). They may not capture complexities like deviated wells, viscous fluids, or friction. Therefore, they should be used as qualitative guides.
A: The cards are based on idealized analog models with specific assumptions (straight well, constant damping, single-phase fluid). They may not capture complexities like deviated wells, viscous fluids, or friction. Therefore, they should be used as qualitative guides.
Q: Was API Bull 11L2 superseded?
A: As of 1999, the bulletin was reaffirmed and remained current. Later standards such as API RP 11S and API 11W complement it. While Bull 11L2 has not been formally withdrawn, modern digital tools have largely replaced the analog card catalog for routine troubleshooting.
A: As of 1999, the bulletin was reaffirmed and remained current. Later standards such as API RP 11S and API 11W complement it. While Bull 11L2 has not been formally withdrawn, modern digital tools have largely replaced the analog card catalog for routine troubleshooting.
Document reference: API Bull 11L2-1969 (1999). This article is provided for educational purposes. © 2026.