A gas lift valve is the small but critical device that decides where injection gas enters the tubing on a gas-lifted well. It sits in a side-pocket mandrel down the string and opens or closes in response to pressure, controlling the depth at which compressed gas aerates the fluid column. This guide focuses on the valve itself - how a nitrogen-charged bellows valve works, how a string of valves unloads a well, and what its pressures tell an operator watching from SCADA.
Gas Lift Valve in one line: A gas lift valve (GLV) is a pressure-operated valve mounted in a side-pocket mandrel on the production tubing that admits compressed injection gas from the annulus into the tubing at a set depth. Most operating valves use a nitrogen-charged metal bellows as the closing force, so the valve opens when annulus (injection) pressure overcomes the dome charge, letting the well be unloaded and lifted from the deepest practical point of injection.
The heart of a conventional gas lift valve is a sealed metal bellows charged with nitrogen to a set dome pressure. That charge pushes a stem onto a seat, holding the valve closed. Injection gas in the casing-tubing annulus presses on the effective bellows area from the outside; when that annulus pressure rises enough to overcome the nitrogen dome charge, the bellows compresses, the stem lifts off the seat, and gas flows through a port into the tubing. Because the dome charge is temperature-sensitive, valve designs and setting calculations account for the downhole temperature at the valve's depth.
Valves are classified by what pressure dominates their opening. An injection-pressure-operated (IPO) valve responds mainly to casing (injection) pressure and is the common choice for continuous lift and for the unloading string. A production-pressure-operated (PPO), or fluid-operated, valve responds mainly to tubing pressure and is used where the design needs the valve to sense the fluid in the tubing rather than the annulus. A plain orifice valve has no bellows at all - it is simply a calibrated port used as the operating point once the well is unloaded, sized to pass the target injection rate.
A well is normally full of kill fluid or produced liquid when gas lift starts, and that liquid is too heavy for gas at the deepest valve to displace immediately. So a string of gas lift valves is spaced from shallow to deep, each set to a slightly different pressure, to unload the well in stages. Injection gas first enters through the top valve, lightening the column above it and pushing liquid up and out until the fluid level drops below the second valve. Gas then reaches the second valve, which takes over while the top valve closes, and the process repeats down the string.
The goal is to walk the point of gas injection down to the deepest valve or the orifice, because injecting as deep as possible gives the reservoir the most help. Once the well is unloaded, the upper unloading valves stay shut and lift continues steadily through the deepest operating valve or orifice. Correct valve spacing and pressure settings are what make this handoff clean; a poorly designed string can stall the unloading partway, leaving the well lifting from a shallow, inefficient depth. Multipointing - gas leaking through more than one valve at once - wastes gas and destabilizes the well.
You cannot see a downhole valve directly, but its behavior is written all over the surface pressures. Casing (injection) pressure, tubing (production) pressure, and injection gas rate together reveal which valve is passing gas and whether the well is unloading, stable, or heading. During unloading, each handoff from one valve to the next shows up as a characteristic step in casing pressure; after unloading, a steady casing pressure and smooth injection rate indicate the well is lifting cleanly from the operating point.
A cloud SCADA such as Merobix reads injection controllers, casing and tubing transmitters, and gas meters over Modbus and trends them for every gas-lifted well in a field from a browser. Alarms on casing pressure and injection rate flag a valve that has failed to close, a well that has fallen back to a shallow injection point, or multipointing that is wasting compression. Trending injection and production pressure over days also helps an engineer confirm the well is still injecting through the intended valve rather than an unloading valve upstring, which is the difference between an optimized well and one quietly leaving barrels behind.
Gas lift is the artificial-lift method - lightening the fluid column by injecting compressed gas so reservoir pressure lifts the well. A gas lift valve is a single component of that system: the pressure-operated valve in a mandrel that decides at what depth injection gas enters the tubing. A gas-lifted well typically runs a string of several valves plus an operating orifice.
An injection-pressure-operated (IPO) valve opens mainly in response to casing (injection) pressure and is the usual choice for continuous lift and unloading strings. A production-pressure-operated (PPO), or fluid-operated, valve responds mainly to tubing (production) pressure. The distinction is which pressure the valve is designed to sense as its dominant opening force.
A well full of liquid is too heavy for gas to displace from the deepest valve right away, so a string of valves spaced from shallow to deep unloads the well in stages. Gas enters through the top valve first, then progressively through deeper valves until injection reaches the deepest operating valve or orifice, where it gives the reservoir the most lift.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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