Detection of rod pump fillage from motor power

An oil well arrangement, comprising:

• a well pump having an electric motor operable to reciprocate a piston and chamber structure disposed in a well bore;
• a pump controller coupled between the well pump and an electric power line, the controller including a watt transducer coupled to an analog to digital converter, for measuring an instantaneous power consumption of the motor from the power line, a processor being coupled to an output of the analog to digital converter, and operable to identify periodic cycles of the pump from periodic variations in said instantaneous power consumption, the processor comparing the instantaneous power consumption for successive periodic cycles, at least at one predetermined phase region of the periodic cycles, for identifying variation in power consumption of the well pump characteristic of operation at less than a maximum capacity of the pump per stroke.

A method for monitoring a well having a cyclic well pump driven by an electric motor, comprising the steps of:

• repetitively measuring an instantaneous electric power level applied to the motor to obtain successive samples;
• identifying in the successive samples a periodic variation in power consumption occurring with an upstroke and a downstroke of the pump;
• comparing the power consumption during successive downstrokes to determine a fillage level of the pump between successive downstrokes.