Patent ID: 7870900

Claim:
A method of controlling pump speed of a progressing cavity pump ( 10 ) to increase liquid production from a well ( 80 ) while avoiding operation of the well ( 80 ) in a pumped-off state, said method comprising the steps of: controlling a variable speed drive ( 46 ) with a controller ( 50 ) to drive said progressing cavity pump ( 10 ) at a set pump speed for producing liquid production from said well ( 80 ); measuring a current flow rate of liquid production from the well ( 80 ) using a flow measurement device ( 56 ) arranged and designed to generate a current flow rate signal representative of current flow rate of liquid production from the well ( 80 ) and to transmit said current flow rate signal to said controller ( 50 ); receiving said current flow rate signal in said controller ( 50 ); determining a differential flow rate signal with said controller ( 50 ), said differential flow rate signal representative of the difference between said current flow rate signal representative of current flow rate and a previous flow rate signal representative of previous flow rate of liquid production from the well ( 80 ); controlling said variable speed drive ( 46 ) with said controller ( 50 ) to adjust the set pump speed of the progressing cavity pump ( 10 ) in response to the differential flow rate signal, increasing said set pump speed by a step change when the differential flow rate signal indicates an increase in the current flow rate, decreasing said set pump speed by a step change when the differential flow rate signal indicates a decrease in the current flow rate, increasing said set pump speed by a step change when the differential flow rate signal indicates no change in current flow rate and said set pump speed was previously decreased, and decreasing said set pump speed by a step change when the differential flow rate signal indicates no change in current flow rate and said set pump speed was previously increased.