Justification of the feasibility of use of frequency converters in control stations of submersible centrifugal pumps

Abstract

The article considers the problem of determining the conditions under which the use of a frequency converter in a submersible pump control station leads to a reduction in electrical energy costs and becomes efficient from an energy point of view. Analytical expressions are given that allow calculating the specific costs of electrical energy during artificial lift oil production for the case when the operating mode and well flow rate are provided by wellhead choke throttling. At the same time, special attention is paid to determining the rotation speed of the submersible asynchronous motor, which ensures the required location of the operating point on the pump pressure characteristic. Formulas are also given that make it possible to calculate the specific costs of electrical energy during artificial lift oil production for the case when the operating mode and well flow rate are set by the frequency converter of the control station. An analytical expression has been found to determine the rotation speed and frequency of the supply voltage, which provide the required operating point of the pump with frequency regulation of the submersible motor. It is proposed, using the above analytical expressions, to use the iterative method to calculate the pump performance, at which the specific energy costs for the production of a cubic meter of liquid will be equal both in the case of using a frequency converter in the control station and without it. An example of calculating such a boundary value of pump performance for a hypothetical well is given. It is shown that a decrease in the required flow rate relative to the limiting value of the pump performance leads to a decrease in the specific consumption of electrical energy during artificial lift oil production in the case of using a frequency converter in the submersible pump control station.