Gas Lift Installations design

Different types of gas lift installations are used in the industry depending on well conditions.

 They fall into four categories: 

(1) open installation  (2) semiclosed installation (3) closed installation (4) chamber installation 

 (1) open installation 

As shown in Fig.a no packer is set in open installations.This type of installation is suitable for continuous flow gas lift in wells with good fluid seal. Although this type of installation is simple, it exposes all gas lift valves beneath the point of gas injection to severe fluid erosion due to the dynamic changing of liquid level in the annulus. Open installation is not recommended unless setting packer is not an option.

 (2) semiclosed installation

Figure b demonstrates a semi closed installation. It is identical to the open installation except that a packer is set between the tubing and casing. This type of installation can be used for both continuous- and intermittent-flow gas lift operations. It avoids all the problems associated with the open installations. However, it still does not prevent flow of well fluids back to formation during unloading processes, which is especially important for intermittent operating.

(3) closed installation

  Fig.c is a closed installation where a standing valve is placed in the tubing string or below the bottom gas lift valve. The standing valve effectively prevents the gas pressure from acting on the formation, which increases the daily production rate from a well of the intermittent type.

 (4) chamber installation

Chamber installations are used for accumulating liquid  volume at bottom hole of intermittent-flow gas lift wells .A chamber is an ideal installation for a low BHP and high PI well.

The chambers can be configured in various ways 

    (A) standard two-packer chamber (B)insert chamber (C) reverse flow chamber. 

 (A) standard two-packer chamber

This type of chamber is installed to ensure a large storage volume of liquids with a minimum amount of backpressure on the formation so that the liquid production rate is not hindered.

(B)insert chamber

It is normally used in a long open hole or perforated interval where squeezing of fluids back to formation by gas pressure is a concern. It takes the advantage of existing bottom-hole pressure. The disadvantage of the installation is that the chamber size is limited by casing diameter.

 (C) reverse flow chamber

It ensures venting of all formation gas into the tubing string to empty the chamber for liquid accumulation. For wells with high formation GLR, this option appears to be an excellent choice.