A gas-lift well is fitted with several valves stacked down the tubing, but at any moment only one of them, ideally, is passing the injection gas. That active valve marks the point of injection, and how deep it sits determines how efficiently the well lifts. This guide explains what the point of injection is, why the deepest single valve is the design target, how multipointing and shallow injection waste gas, and how surface pressure and rate readings tell you where the active point actually is.
Gas Lift Point of Injection in one line: The gas lift point of injection is the depth of the mandrel and valve through which injection gas is actually entering the tubing at a given time. The design goal is single-point injection through the deepest operating valve, because lifting from as deep as possible aerates the longest fluid column and returns the most oil per unit of injected gas.
A gas-lift string carries multiple valves in side-pocket mandrels at increasing depths. During unloading, the well transfers from valve to valve, each upper valve handing off to the next deeper one as the annulus is unloaded. Once the well reaches steady lift, gas should be entering through a single valve, the deepest one it can hold open under the available injection pressure. That valve's depth is the point of injection, and everything above it is just plumbing at that moment.
The point of injection is a property of the well's operating state, not a fixed number stamped on the completion. It moves if conditions change: a lower injection pressure, a valve that fails to reopen, or a shift in fluid level can cause the well to inject from a shallower valve than intended. Knowing which valve is currently active is therefore a live diagnostic, not a one-time design fact, and it is central to understanding how a well is performing today.
The design intent is captured in the valve spacing: the mandrels are spaced so that, with the expected injection-gas pressure and fluid gradients, the well can unload down to and operate from the deepest valve. When the well actually injects from that design valve, it is doing what the completion was built to do. When it injects from somewhere higher, something has changed and lift efficiency suffers.
Gas lift works by lightening the fluid column so the reservoir can push it to surface. The deeper the point of injection, the longer the section of column that gets aerated, and the more effectively the reservoir energy is used. Injecting from a shallow valve leaves a long, heavy, un-aerated column below the injection point that the well must lift with only formation pressure, so it produces less for the same gas. Depth of injection is one of the biggest levers on lift efficiency.
Single-point injection matters just as much as depth. Multipointing, where gas passes through two or more valves at once, splits the injection between a deep and one or more shallow points. The gas going in shallow does little useful work, and it can rob pressure from the deeper valve, sometimes pushing the well toward heading. A well that is multipointing is spending gas without buying much oil with it, which is why holding a single, deep point is the efficiency target.
There is a natural limit: you cannot inject deeper than the deepest valve the available pressure can hold open, and pushing a well to inject too deep with too little gas can leave it unable to unload. The objective is not simply maximum depth at any cost but the deepest stable single point the well can hold. Getting there is a balance of injection-gas pressure, gas rate, and valve design.
Downhole surveys can pinpoint the injection point directly, but for day-to-day operation the point of injection is usually inferred from surface signals. The casing head pressure a well settles at corresponds to the operating pressure of whichever valve is passing, so a casing pressure sitting near a shallow valve's setting, or trending upward toward one, indicates a shallow or shifting injection point. Tubing pressure and injection rate round out the picture.
Erratic pressure and pulsing flow suggest multipointing or heading rather than clean single-point injection, while a stable casing pressure near the deepest valve's design setting suggests the well is lifting where it should. These inferences depend on comparing the current surface behavior to what the valve design predicts, which is why keeping the valve settings and the live pressures side by side is so valuable. The trend over time, not a single reading, reveals a slowly rising injection point.
A cloud SCADA such as Merobix trends casing pressure, tubing pressure, and injection rate continuously and puts them next to the well's expected operating point, so a drift toward shallow or unstable injection shows up as a change in the traces. An engineer can spot a well that has moved off its deepest valve early, adjust injection to try to re-establish the deep point, or schedule an intervention, rather than discovering the efficiency loss only at the next well test.
It is the depth of the valve through which injection gas is actually entering the tubing at a given time. A gas-lift string has several valves, but in steady operation gas should pass through only one, ideally the deepest the injection pressure can hold open. That active valve's depth is the point of injection, and it largely sets how efficiently the well lifts.
Because gas lift works by aerating and lightening the fluid column, a deeper injection point lightens a longer section of column and uses reservoir energy more effectively, producing more oil for the same gas. A shallow injection point leaves a long heavy column below it that the well must lift on formation pressure alone. That is why the design target is the deepest single valve the well can stably hold.
Multipointing is when injection gas passes through two or more valves at once instead of a single deep valve. The gas entering through shallow valves does little useful lifting and can steal pressure from the deep valve, hurting efficiency and sometimes triggering heading. Because it spends gas without returning much oil, single, deep-point injection is preferred, and surface pressure and flow instability are the usual clues that a well is multipointing.
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