Detection of rod pump fillage from motor power

摘要

The extent to which a reciprocating pump for an oil well fills between successive pump strokes is determined indirectly from variations in the power consumption of an electric motor driving the pump. The power consumption is sampled numerically and a processor determines the phase of data in the samples from phase references defined by a peak and/or zero crossing in the cyclic operation of the pump and motor. When the pump fills incompletely between strokes, for example when the pump is operated at too high a frequency, the well rod moves against decreased resistance during the downstroke. The processor determines the point in the pump cycle at which the well rod encounters fluid from the increased power consumption, obtaining an indirect indication of fillage. The instantaneous power consumption preferably is measured by a module associated with an electrical contactor or motor starter included in an improved pump controller or "pump panel" that includes a programmable controller effecting the processor functions and also functioning as an off-pump control for regulating activation of the pump.