A system for attaining and maintaining a pre-determined fluid level in a petroleum-producing well having a pump, such as a progressive-cavity pump, and a pump motor having a variable-frequency drive control using two sensors: a pump pressure sensor located at the pump depth and a casing pressure sensor located at the casinghead of the well. A programmable computer is connected to the first and second pressure sensors and the motor speed control so that the programmable computer controls the operation of the pump motor to attain and maintain a target fluid level in the well over a predetermined time interval for reaching the target fluid level in the well. The programmable computer computes an error signal to control a variable frequency drive motor, where the error signal is computed periodically from the difference between in the actual fluid level in the well and the target fluid level in the well according to a rate reference curve. In general, the rate reference curve is generated according to an exponential or hyperbolic function.