Why run a Packer with Intermittent Gas Lift?

Why run a Packer with Intermittent Gas Lift?
 
A few operators try saving money by not running a packer in a gas lift well producing less than 300 barrels of fluid per day, where natural plunger lift is not possible and Intermittent Gas Lift (IGL) is needed.
 
These Packerless gas lift installations lose revenue and lease asset value for the following reasons:

·      Packerless installations in early applications of gas lift were found to be inefficient for low liquid level – low bottom hole pressure wells. High pressure gas in the casing annulus, acting directly against the exposed reservoir prevented satisfactory operation. A packer was therefore installed between the tubing and casing for holding the annulus gas off the formation between injection cycles.
 
·      IGL efficiency in low-volume wells was enhanced by adding a standing valve in the tubing as a supplement to the annulus packer to further prevent exposing the low pressured reservoir to high pressure injection gas.
 
·      Operators commonly run Packerless IGL installations in pressure depleted reservoirs and it is highly likely that excessive injection gas is blown around the bottom of the tubing string during operation. Some operators do not run gas lift valves with their packerless installations. This worse case scenario results in the tubing pressure being blown down near separator pressure after the liquid slug has been produced at the surface. This increases the intermittent cycle’s gas requirement and leads to excessive gas usage.
 
·      For Packerless IGL installations with gas lift valves, each time the well is shut down, well fluids rise in the annulus and the well must again be unloaded to the depth of the operating valve at the next startup. During repeated unloading operations, gas lift valves are exposed to liquid flow across the ports. These ports can be gradually eroded by fines carried within the liquid. Such damage may result in leakage of gas lift valves in the tubing string, multipoint gas injection, excessive gas usage, elevated inflow bottom hole pressures, and poor producing volumes.
 
·      “During the period when gas is injected into the annulus, injection gas can directly act on the formation and thus prevent the required reduction in bottom hole pressure. This condition is more pronounced for low reservoir pressured intermittent gas lift wells, than wells producing on continuous lift. A packerless installation, therefore, restricts the increase in liquid production: that is why wells near abandonment cannot be produced with this type of installation”. (Prof. Gabor Takacs-Legend of Artificial Lift, SPE inducted).

The use of a Packerless installation for Intermittent Gas Lift is therefore not recommended. The attachment describes the downhole equipment for Intermittent Gas Lift using best gas lift industry practice.