Method and system to volumetrically control additive pump
A chemical/additive injection controller, system and method (i.e., utilities) are provided that control when an injection pump turns on and off in order to inject a predetermined volume of additives into a hydrocarbon production conduit over a predetermined number of cycles per day. The controller determines when to activate and deactivate (i.e., turn on and turn off) an injection pump to provide a desired total additive injection volume over an injection period (e.g. 24 hours). More specifically, the utilities incorporate a flow meter that monitors the actual amount of additive that is injected during a pump cycle. Once an injected volume meets or exceeds a target injection volume the pump is deactivated. The flow meter continues to monitor the injection volume including amounts injected after power to the pump is deactivated to provide an accurate measure of the total injection. Subsequent injections are varied based on the actual measured volume of one or more previous injections.
1. An injection system operative to controllably inject an additive into a hydrocarbon production conduit, comprising:
a pump fluidly connected to an additive source and a hydrocarbon production conduit, said pump being operative to inject additive from said additive source into said hydrocarbon production conduit;
a flow meter disposed in a fluid conduit connecting said additive source and said hydrocarbon production conduit, said flow meter providing output signals representative of fluid volumes pumped by said pump during and after a pump cycle, wherein activation and deactivation of said pump defines the pump cycle;
a controller operatively connected to said pump and said flow meter and configured to inject a total injection volume of the additive over an injection period and in a plurality of discrete pump cycles, said controller being further operative during each discrete pump cycle to:
activate said pump;
deactivate said pump upon a volume of additive pumped during said discrete pump cycle equaling or exceeding a pump cycle target volume for said discrete pump cycle as indicated by a first output signal of said flow meter;
calculate an actual volume of said additive pumped once fluid flow in said fluid conduit ceases as indicated by a second output signal of said flow meter; and
adjust said pump cycle target volume based on a difference between said actual volume and a fixed cycle target volume to produce an adjusted pump cycle target volume, wherein:
said pump cycle target volume is reset to said adjusted pump cycle target volume for a subsequent discrete pump cycle if the difference is less that said fixed cycle target value; and
wherein the pump is inactive during the subsequent discrete pump cycle if the difference between said actual volume and said fixed cycle target volume exceeds said pump cycle target volume.
2. The system of claim 1 , wherein said fixed cycle target volume comprises said total injection volume divided by said number of pump cycles for said injection period.
3. The system of claim 1 , wherein said flow meter is disposed in said fluid conduit upstream of said pump.
4. The system of claim 1 , further comprising;
a pulsation dampener disposed between said flow meter and said pump.
5. The system of claim 1 , wherein said flow meter comprises a positive displacement flow meter.
6. The system of claim 1 , wherein said pump comprises a brushed motor pump.
7. The system of claim 1 , wherein said controller is further operative to:
receive user inputs identifying a total injection volume of said additive for an injection period and a number of pump cycles for said injection period.
8. The system of claim 1 , wherein said flow meter is reset once fluid flow in said fluid conduit ceases.
9. The system of claim 1 , wherein said hydrocarbon production conduit comprises one of:
a well bore; and
a pipeline.
10. A controller operative to controllably inject an additive into a hydrocarbon production conduit, the controller being operatively connected to a pump and a flow meter measuring additive passing through the pump, comprising:
a user interface providing communication between a user and the controller, wherein said user interface is operative to receive user inputs;
a pump control output module operative to activate and deactivate a pump;
a system interface operatively connected to a flow meter for receiving signals from the flow meter indicative of volumes of additive passing through the pump;
a computer connected to said user interface, said pump control output module and said system interface, the computer further comprising a stored program containing instructions to:
calculate a pump cycle target volume and pump activation schedule;
generate a pump activation signal to activate the pump according to said pump activation schedule;
generate a pump deactivation signal to deactivate the pump upon a volume of additive pumped during a discrete pump cycle equaling or exceeding said pump cycle target volume as indicated by a first output signal received from said flow meter, wherein activation and deactivation of the pump defines a discrete pump cycle; and
calculate an actual volume of said additive pumped during the pump cycle once fluid flow in said fluid conduit ceases as indicated by a second output signal received from said flow meter; and
adjust said pump cycle target volume based on a difference between said actual volume and a fixed cycle target volume to produce an adjusted pump cycle target volume, wherein said pump cycle target volume is reset to said adjusted pump cycle target volume for a subsequent discrete pump cycle; and
upon calculating the difference between the actual volume and the fixed cycle volume exceeding said pump cycle target volume, setting the adjusted pump cycle volume to zero, wherein the pump is inactive during the subsequent pump cycle.
11. The controller of claim 10 , wherein said controller calculates said fixed cycle target volume as a ratio of a total injection volume for an injection period divided by a number of pump cycles for the injection period, wherein the total injection volume and the number of pump cycles are received from the user interface.
12. The controller of claim 11 , wherein the pump cycle target volume for an initial pump cycle is set to the fixed cycle target volume.
13. A method for controllably injecting an additive into a hydrocarbon production conduit, comprising:
activating a pump fluidly connecting an additive supply and the hydrocarbon production conduit;
deactivating the pump upon a volume of additive pumped during activation of the pump equaling or exceeding a pump cycle target volume as indicated by a first output signal of a flow meter disposed in a fluid conduit connecting the additive supply and the hydrocarbon production conduit, wherein activating and deactivating the pump defines a pump cycle;
calculating an actual volume of said additive pumped during the pump cycle once fluid flow in said fluid conduit ceases as indicated by a second output signal of said flow meter; and
adjusting said pump cycle target volume based on a difference between said actual volume and a fixed cycle target volume to produce an adjusted pump cycle target volume, wherein said pump cycle target volume is reset to said adjusted pump cycle target volume for a subsequent pump cycle; and
upon calculating the difference between the actual volume and the fixed cycle volume exceeding said pump cycle target volume, setting the adjusted pump cycle volume to zero, wherein the pump is inactive during the subsequent pump cycle.
14. The method of claim 13 , during the subsequent pump cycle further comprising:
activating the pump; and
deactivating the pump upon a volume of additive pumped during activation of the pump exceeding the pump cycle target volume, wherein the pump cycle target volume represents the adjusted pump cycle target volume calculated after a previous pump cycle.
15. The method of claim 13 , further comprising calculating the fixed cycle target volume as a ratio of a user set number of pump cycles for an additive injection period divided by a user set additive volume for the injection period.
16. The method of claim 15 , further comprising receiving user inputs identifying at least one of:
said additive volume for said additive injection period;
said additive injection period; and
said number of pump cycles for said additive injection period.