A chemical injection system for controlling injection of an injection fluid from an injection fluid supply at a surface location into a production tubing assembly having an upper flow path, a first flow zone, and a second flow zone. The chemical injection system comprises a first fluid injection line configured to inject the injection fluid into the first flow zone and a second fluid injection line configured to inject the injection fluid into the second flow zone. A main fluid supply line is configured to fluidly connect both the first fluid injection line and the second fluid injection line to the injection fluid supply.