Choosing a proper injection pressure is critical to a gas lift system design. Several factors may affect the choice of an injection-gas pressure. However, one primary factor stands out above all others. To obtain the maximum benefit from the injected gas, it must be injected as near the producing interval as possible.
A variety of other factors can affect the selection of the most efficient surface injection pressure including:
- Pressure/volume/temperature (PVT) properties of the crude
- Water cut of the producing stream
- Density of the injected gas
- Wellhead backpressure
- Pressure rating of the equipment
- Design of the well facility
The injection-gas pressure at depth must be greater than the flowing producing pressure at the same depth. Any compromise with this principle will result in less pressure drawdown and a less efficient operation. High volumes of gas injected in the upper part of the fluid column will not have the same effect as a much smaller volume of gas injected near the producing formation depth because the fluid density is reduced only above the point of gas injection.
Selection of higher injection pressure facilitates fewer gas lift valves as it results in a greater pressure differential between the injection pressure and the flowing tubing pressure; thereby, allowing a greater spacing between valves.
Injection gas volume is also a critical component to how the well performs. Too little injection gas may not unload the well to the deepest point of injection and will cause the well to underperform. Excessive injection gas will induce pressure losses due to friction which will cause the well to underperform as well. Once the injection depth is reached and the well stabilizes, the injection gas volume can usually be decreased to conserve horsepower.
Still experiencing issues or have questions? We can help. Our gas lift experts can work with your production team or create a custom well design. Contact us to coordinate with our local team and we will get back with you promptly.