Gas-lift valve (external)
Mounted on the outside of tubing string
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Description
This valve type is used in intermittent gas-lift operation to reduce startup pressures by removing part of the liquid from the lift string. After liquid discharge, the valve closes and reopens only when liquid in tubing accumulates to a specified level.
Technical specifications
| Parameter | Value |
|---|---|
| Nominal valve diameter, mm | 25 |
| Seat orifice diameter, mm | 5.0, 6.5, 8.0, 9.5 |
| Operating pressure, MPa | 21 |
| Maximum stem stroke, mm | 4.5 |
| Maximum bellows charging pressure, MPa | 16 |
| Effective bellows area, cm2 | 16 |
| Working medium | natural gas, associated petroleum gas, oil, and produced water with CO2 content up to 0.2%, H2S up to 0.1% (by volume), and mechanical impurities up to 1 g/l. |
Operating principle
During operation, pressurized gas is injected into the annulus between casing and tubing and enters tubing through the open gas-lift valve. Fluid above the valve in tubing is displaced and/or lightened by gas mixing and can rise to surface with the expanding gas. At surface, gas is separated from oil, then recompressed and injected again to repeat the cycle.