Method and apparatus for delivering chemicals to a well head

Abstract

A pump controller for electrical connection between a source of chemical supply and a DC powered chemical injection pump of the type having a reciprocating piston or diaphragm for delivering a quantity of chemical to a well head after each compression stroke of the pump, the controller including: a switch operable to sequentially deliver activation current to the pump; a voltage sensor between the pump and the switch to extract DC voltage signals indicative of activation of the pump, an analogue-to-digital convertor for converting the sensed DC voltage signals into digital format; a digital signal processor operative to differentiate DC stroke voltage signals from the sensed voltage signals, thereby to indicate the occurrence of each stroke; and a switch controller programmed with pump parameters and target chemical delivery dosages to sequentially deliver activation current to the pump, measured or calculated from the digital DC stroke voltage signals, and hence chemical delivery to the well via the injection pump at required intervals.

1 . A pump controller for electrical connection between a source of chemical supply and a DC powered chemical injection pump of the type having a reciprocating piston or diaphragm for delivering a quantity of chemical to a well head after each compression stroke of the pump, the controller including:
 a switch operable to sequentially deliver activation current to the pump;   a voltage sensor between the pump and the switch to extract DC voltage signals indicative of activation of the pump,   an analogue-to-digital convertor for converting the sensed DC voltage signals into digital format;   a digital signal processor operative to differentiate DC stroke voltage signals from the sensed voltage signals, thereby to indicate the occurrence of each stroke; and   a switch controller programmed with pump parameters and target chemical delivery dosages to sequentially deliver activation current to the pump, measured or calculated from the digital DC stroke voltage signals, and hence chemical delivery to the well via the injection pump at required intervals.   
     
     
         2 . The pump controller of  claim 1 , wherein said voltage sensor is a shunt resistor. 
     
     
         3 . The pump controller of  claim 1  wherein said voltage sensor is a Hall-effect device. 
     
     
         4 . A pump controller according to  claim 1  wherein the pump controller is battery operated, such as by being connected directly or indirectly to a battery supplying activation current to the pump motor. 
     
     
         5 . A pump controller according to  claim 1  wherein the digital signal processor includes one or more band-pass filters whereby to differentiate stroke voltage signals from background voltage signals from the pump motor. 
     
     
         6 . A method of controlling delivery of chemicals from a DC powered reciprocating chemical injection pump to a well head, the method including the steps, in any convenient order, of collecting voltage analogue signals indicative of activation of the pump from the DC motor of the chemical injection pump, thereafter converting the voltage signals to digital signals and analysing the digital signals to identify successive strokes of the pump, using the counted strokes to indicate when a required amount of chemical has been delivered to the well head, and thereafter deactivating the current to the pump for a selected time period, the sequence continuing whereby to regularly provide measured or calculated volumes of chemical to the well head via the injection pump. 
     
     
         7 . A method of delivering a required amount of chemical to a well head from a chemical storage tank having an associated chemical volume gauge graduated to provide an indication of volume of chemical deliverable to the well head via an associated displacement pump, the method including the steps of disconnecting the chemical storage tank from the gauge, taking a reading of the gauge as to quantity of chemical in the gauge and thereafter activating the pump for a given number of pump strokes measured or calculated in accordance with the second aspect of the invention, thereafter taking another reading of the gauge to determine the volume of chemical remaining in the gauge and hence quantity of chemical delivered to the well head per stroke from the gauge, thereafter reconnecting the chemical storage tank to the pump and sequentially delivering the required volume of chemical to the well head at predetermined intervals by reference to pump strokes over time. 
     
     
         8 . A method according to  claim 7  wherein the chemical volume gauge is a graduated sight glass.