Average upstroke load for a sucker-rod pump in a drilling operation depends on several factors, including the depth of the well, the fluid being pumped, the pump size, rod string design, and operating conditions like pump speed and stroke length. In sucker-rod pumping systems, the upstroke load is typically the maximum load experienced by the rod string as it lifts the fluid column and the pump plunger against gravity.
Average Upstroke Load (Sucker-Rod Pump) Formula |
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\( AUL \;=\; C \cdot \dfrac{ A \cdot a }{ L } \) (Average Upstroke Load) \( C \;=\; \dfrac{ AUL \cdot L }{ A \cdot a } \) \( A \;=\; \dfrac{ AUL \cdot L }{ C \cdot a } \) \( a \;=\; \dfrac{ AUL \cdot L }{ C \cdot A } \) \( L \;=\; \dfrac{ C \cdot A \cdot a }{ AUL } \) |
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| Symbol | English | Metric |
| \( AUL \) = Average Upstroke Load | \(lbf\) | \(kg\) |
| \( C \) = Calibration Constant of Dynamometer Card | \(lbf\;/\;in\) | \(kg\;/\;mm\) |
| \( A \) = Area of Upper Card | \(in^2\) | \(mm^2\) |
| \( a \) = Lower Area of Card | \(in^2\) | \(mm^2\) |
| \( L \) = Length of Card | \(in\) | \(m\) |
The upstroke is one of the two main phases of a sucker-rod pumping cycle (the other being the downstroke). The pumping unit (a beam pump or "nodding donkey") lifts the polished rod, which is connected to the sucker-rod string. This motion is driven by the surface equipment, typically a motor and crankshaft system. The sucker-rod string is connected to a plunger (or pump piston) located downhole in the pump barrel. As the rod string moves upward, the plunger also rises, creating a low-pressure zone below it. The traveling valve, attached to the plunger, closes due to the pressure differential. This prevents fluid above the plunger from flowing back down into the pump barrel.
The standing valve, located at the bottom of the pump barrel, opens as the plunger rises. This allows fluid from the well (oil, water, or a mixture) to enter the pump barrel from the reservoir due to the suction created by the plunger’s upward movement. The fluid already trapped above the traveling valve (from the previous cycle) is lifted toward the surface through the production tubing. This is the primary work of the upstroke, raising the fluid column against gravity.
During the upstroke, the rod string bears the maximum load, which includes: The weight of the fluid column being lifted. The weight of the rods themselves (adjusted for buoyancy in the fluid). Dynamic forces due to acceleration and friction. The mechanical energy from the surface pumping unit is transferred through the rod string to lift the fluid, making the upstroke the energy, intensive phase of the cycle.
- See Article - Average Downstroke Load (Sucker-Rod Pump)
