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US 4,034,808 AGranted
Method for pump-off detection
AssigneeShell Oil Company
InventorMaurice M. Patterson
Life of this patent
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Abstract
A method and apparatus for measuring the energy input to the rod string of a well pumping unit in real time wherein the load on the rod string is multiplied by the velocity of the rod string and the result integrated over at least a portion of the pump stroke. The change in the energy input to the well is used to determine when the well has pumped-off.
Claims7
A method for measuring the energy input to the rod string in a rod pumping unit comprising:
- measuring the load on the rod;
- obtaining the velocity of the rod;
- and
- multiplying the load times the velocity and integrating the product to obtain the energy input for each stroke in real time.
1 more element
A method for determining when a rod pumped well has pumped-off comprising:
- measuring the load on the rod string and producing an analog electrical signal;
- simulating the velocity of the rod string by a sine wave electrical signal having a period equal to the time required for the pump to make a complete stroke;
- multiplying the load signal by the simulated velocity;
- integrating the negative values of said multiplication to obtain the negative energy input to the rod string;
- and
- comparing said negative energy input with predetermined value to determine when said well is pumped-off.
3 more elements
Dependencies are inferred from the claim text.