1. n. [Well Completions]

The lowermost gas-lift valve in a gas-lift completion through which the lift gas is injected during normal production. During startup, the upper gas-lift valves open in sequence, from the top down, to enable the tubing fluids to be displaced. At predetermined pressures, each of the upper valves closes to eventually route all lift gas through the operating valve, which is placed at the optimal depth for the reservoir and completion conditions.

See: gas lift