Gas lift is a process where high-pressure gas is reinjected into the well riser to mix with the fluid, thus helping with lifting oil from a well by making the weight of the fluid column lighter in weight.

A gas lift compressor injects gas into an oil well to aerate the crude oil, increasing production . The gas is introduced from the surface into the tubing-casing annulus and introduced into the tubing at the desired depth. This gas injection decreases the fluid density in the tubing, thereby increasing the well pressure at the surface. The application may be combined with a gas gathering operation, and some offshore operators use the same compressor train to both feed a gas lift service and export compression to feed gas into a pipeline.

We will show you how gas lift can be used to unload a gas well or prevent a gas well from loading. An unconventional gas well is shown with a high rate initially and then quickly declining to lower rates. It is shown that for gas wells, early addition of gas lift to a high-rate gas well adds pressure drop to the tubing and is useful only as the well approaches low rates and critical velocity or rate. This is contrasted to an oil well where it is shown that addition of gas lift can be beneficial even for high production rates and also down near the point of instability or loading. For an oil well, gas lift can be a high rate method, but for a gas well, it cannot.

Gas lifting can lift high volumes of fluid from moderate to deep well depths. In gas lifting, the reservoir fluids are lifted from the wellbore by injection, intermittent or continuous,of a high-pressure gas to supplement the reservoir's energy.

Gas lift is an artificial lift method that is the closest to natural flowing production. Firstly inject compressed gas into the bottom of the tubing, where it mixed with fluid that oil layers produce. So both the density of fluid that oil layers produce and the weight of fluid column in the oil tubing decrease, which lead the flow pressure gradient in the oil tubing to decrease. And then pressure difference between the bottom hole and the layer increases, which is the power that fluid in the oil tubing flows. So the method of the gas lift is the same as the natural flowing production. And the difference is that the gas lift comes out by the artificial method.

Gas lift is a long-established method for flowing liquid from water- and oil-producing wells. Geothermal wells generally require a lower gas:water ratio than cold water wells because of the additional lift created by steam from boiling. A workover rig or coiled tubing unit will normally be needed to insert the gas injection tubing and then remove it under pressure once flow starts.The result of a successful gas lift initially produces a gas-water flow at the wellhead. As cold fluid is removed from the wellbore by the gas lift, it is replaced by hot water flowing at the feed zone. Provided this fluid is hot enough, it will boil as it flows up the wellbore and create a sustained discharge. Self-sustained discharge may not occur if there is a feed of cold water in the upper part of the production zone since the airlift may simply bring more of this cold water into the well without disturbing the deeper, hotter fluid.

Gas lift  is a predominant artificial lift method used in the offshore environment to date; however, as operators progressively move into deepwater, it applications become more limited due to higher operating pressures and ESPs applications become more suitable.