Determination and control of wellbore fluid level, output flow, and desired pump operating speed, using a control system for a centrifugal pump disposed within the wellbore
First Claim
1. A method of determining a fluid level Xc in a wellbore, where the wellbore extends downward from a surface and has a centrifugal pump disposed therein for transferring fluid within the wellbore using a controller operatively connected to the centrifugal pump, the method comprising:
- determining the value of the zero-flow input speed Uz using the controller to the centrifugal pump at which the output flow from the centrifugal pump is substantially zero, without using output flow from the centrifugal pump;
determining the zero-flow input speed Uz, by monitoring input torque T to the centrifugal pump as input speed Up is reduced, and detecting the zero-flow input speed Uz as an input speed Up at which an incremental reduction in input speed Up is not accompanied by a corresponding incremental reduction in input torque T, and using the zero-flow input speed Uz to calculate, with the controller, the fluid level Xc in the wellbore; and
monitoring a change in torque dT and a change in input speed dU and calculating a quotient dT/dU of the change in torque dT divided by the change in input speed dU, as the input speed Up is reduced, and determining Uz to be substantially a speed at which dT/dU achieves a maximum, using the controller.
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Accused Products
Abstract
A method and apparatus for determining a fluid level and/or output flow during operation of a centrifugal pump, are provided, which may be used for production of gas and/or oil from a well, and include a vector feedback model to derive values of torque and speed from signals indicative of instantaneous current and voltage drawn by the pump motor, a pump model which derives values of the fluid flow rate and the head pressure for the pump from torque and speed inputs, a pumping system model that derives, from the estimated values of the pump operating parameters, an estimated value of fluid level and other pumping system parameters. Controllers responsive to the estimated values of the pumping system parameters control the pump to maintain fluid level at the pump input, near an optimum level, or within a safe operating range and/or output flow from the pump.
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Citations
5 Claims
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1. A method of determining a fluid level Xc in a wellbore, where the wellbore extends downward from a surface and has a centrifugal pump disposed therein for transferring fluid within the wellbore using a controller operatively connected to the centrifugal pump, the method comprising:
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determining the value of the zero-flow input speed Uz using the controller to the centrifugal pump at which the output flow from the centrifugal pump is substantially zero, without using output flow from the centrifugal pump; determining the zero-flow input speed Uz, by monitoring input torque T to the centrifugal pump as input speed Up is reduced, and detecting the zero-flow input speed Uz as an input speed Up at which an incremental reduction in input speed Up is not accompanied by a corresponding incremental reduction in input torque T, and using the zero-flow input speed Uz to calculate, with the controller, the fluid level Xc in the wellbore; and monitoring a change in torque dT and a change in input speed dU and calculating a quotient dT/dU of the change in torque dT divided by the change in input speed dU, as the input speed Up is reduced, and determining Uz to be substantially a speed at which dT/dU achieves a maximum, using the controller. - View Dependent Claims (2, 3, 4, 5)
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Specification