Rod Pump Overview

Introduction

Sucker rod pumping (beam pumping) is the most widely used artificial lift method worldwide, accounting for over 80% of artificially lifted wells. The system uses a surface pumping unit to reciprocate a downhole plunger pump via a string of sucker rods.

Rod pumping is preferred when:

• Low to moderate production rates — typically < 1,000 STB/d
• Moderate depths — typically < 10,000 ft
• Onshore locations — requires surface footprint for beam unit
• Mature fields — well-understood, reliable technology
• Variable rates — easily adjustable via speed and stroke length

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System Components

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Design Parameters

Key Variables

Pump Displacement

The theoretical pump displacement:

$$PD = 0.1166 \times A_p \times S_p \times N$$

Where:

• $PD$ = pump displacement (STB/d)
• $A_p$ = plunger area (in²)
• $S_p$ = effective plunger stroke (inches)
• $N$ = pumping speed (strokes/min)

The actual production rate is less than theoretical due to:

• Fillage — incomplete barrel filling
• Volumetric efficiency — gas interference, leakage
• Effective stroke — rod stretch reduces plunger travel

📖 Full Documentation: Pump Displacement

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Rod String Analysis

Rod Weight and Stretch

The rod string is the critical link between surface unit and downhole pump. Key calculations:

Effective Plunger Stroke

$$S_p = S - \delta_{fluid} - \delta_{rod} + \delta_{dynamic}$$

Where:

• $S$ = polished rod stroke length
• $\delta_{fluid}$ = stretch due to fluid load
• $\delta_{rod}$ = stretch due to rod weight
• $\delta_{dynamic}$ = dynamic effects (acceleration, vibration)

📖 Full Documentation: Rod String Analysis

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Polished Rod Loads

API 11L Method

The API 11L method accounts for dynamic effects using acceleration factors:

Peak Polished Rod Load (PPRL):

$$PPRL = W_f + W_r + W_r \cdot F_1$$

Minimum Polished Rod Load (MPRL):

$$MPRL = W_f - W_r \cdot F_2$$

Where:

• $W_f$ = fluid load on plunger
• $W_r$ = buoyant rod weight
• $F_1$, $F_2$ = dynamic factors depending on $N/N_0$ ratio
• $N_0$ = natural frequency of rod string

Simplified Method

For quick estimates without dynamic factors:

$$PPRL_{simple} = W_f + W_{r,buoyant}$$ $$MPRL_{simple} = W_{r,buoyant} \cdot (1 - S_f)$$

Where $S_f$ = submergence factor.

📖 Full Documentation: Rod String Analysis

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Counterbalance and Power

Ideal Counterbalance Effect

$$CBE_{ideal} = \frac{PPRL + MPRL}{2}$$

The counterbalance should be set to equalize upstroke and downstroke torque on the gear reducer.

Polished Rod Horsepower

$$PRHP = \frac{(PPRL - MPRL) \times S \times N}{33,000 \times 12}$$

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Design Workflow

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Comparison with Other Artificial Lift

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Related Documentation

Rod Pump Details

• Pump Displacement — Fillage, volumetric efficiency, effective stroke
• Rod String Analysis — Loads, stress, stretch, API 11L

Related Topics

• ESP Overview — Alternative artificial lift for higher rates
• GL Overview — Gas lift as alternative artificial lift
• IPR Overview — Inflow performance for lift design

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References

1. Takacs, G. (2015). Sucker-Rod Pumping Handbook. Gulf Professional Publishing.

2. Brown, K.E. (1980). The Technology of Artificial Lift Methods, Vol. 2a. PennWell Books.

3. API Recommended Practice 11L (2008). "Design Calculations for Sucker Rod Pumping Systems (Conventional Units)." American Petroleum Institute.

4. Gipson, F.W. and Swaim, H.W. (1988). "The Beam Pumping Design Chain." In Petroleum Engineering Handbook, Chapter 9. SPE.

5. Clegg, J.D., Bucaram, S.M., and Hein, N.W. (1993). "Recommendations and Comparisons for Selecting Artificial-Lift Methods." Journal of Petroleum Technology, 45(12), 1128-1167. SPE-24834-PA.