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Gas Lift
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About Gas Lift

Gas lift is a method used to artificially lift fluid from wells without sufficient reservoir pressure. High pressure gas is injected down the casing tubing annulus which aerates the fluid to reduce its density. The addition of the gas into the production tubing lowers the flowing pressure which allows the existing formation pressure to lift the fluid column to the surface.

All of the gas injected is recovered from the well as it produces and can be re-used for the lift process. A high pressure gas source or compressor is required to compress the gas for re-injection.

The primary equipment for gas lift installations are the gas lift mandrels and the gas lift valves. The gas lift mandrel which houses the gas lift values is installed in the tubing string of a producing well. There are two common types of gas lift mandrels.

  • A Conventional Mandrel (valve is fitted into a lug on the outside of the mandrel)
  • A Side Pocket Mandrel (has the valve installed in a pocket inside the mandrel)

The conventional mandrel is said to be tubing retrievable, which means the tubing must be extracted to retrieve the mandrel & valve. The side pocket mandrel is said to be wireline retrievable meaning that the valve can be installed or removed using a wireline without pulling the tubing.

The Gas lift process resembles a naturally flowing well. The amount of gas injected will vary depending upon existing well & formation characteristics. Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing , which lightens the gradient of the fluid column and allows the fluid to rise to the surface. Before the valves are placed into the mandrels, they are set at certain pressures based upon the gas lift design. The valves also allow fluid in the casing to escape through the valves and into the production string for initial unloading of the annulus.

A gas lift valve is a device installed on or in a gas lift mandrel, which in turn is put into the production tubing string of a gas lift well. Tubing and casing pressures cause the valve to open and close, thus allowing gas to be injected into the fluid in the tubing , which lightens the gradient of the fluid column and allows the fluid to rise to the surface. Before the valves are placed into the mandrels, they are set at certain pressures based upon the gas lift design.

Advantages of Gas Lift

There are many advantages to using gas lift to produce your well. Gas lift is very flexible to changes in production rates, water cut percentages, and gas liquid ratios (GLRs). An abundance of existing gas in the formation can be detrimental to other artificial lift methods such as sucker rod pumps and electric submersible pumps, however an abundance of formation gas is an advantage to any gas lift system (The more gas the formation produces means less gas is needed for injection). Gas lift wells can be designed to accommodate almost any production volume thus making it more flexible to changes in well conditions throughout the entire life of the well. Initial cost of downhole equipment in gas lift wells is much less than for other artificial lift methods. The main advantages of gas lift are:

  • Very flexible to changes in well conditions and producing rates
  • Low downhole equipment costs
  • Not adversely affected by deviated or horizontal wellbores
  • Reduced production costs over other artificial lift methods
  • Long service life for downhole equipment due to relatively fewer moving parts
  • Major equipment item (gas compressor) is installed at the surface for easy maintenance
  • Ideally suited to supplement formation gas for artificially lifting wells where moderate amounts of gas are present in the produced fluid
Design to Installation

The first step to implementing any gas lift system is a carefully engineered design using specific well data and equipment specifications. After the design is completed, the valves are then set to prescribed design pressure settings, which determine the pressures that the valves will open and close at. The valves are then placed in the gas lift mandrels and are ready to be installed in the production string at the well location. The valves also allow fluid in the casing to escape through the valves and into the production string for initial unloading of the annulus. These valves are then put into the gas lift mandrels and are ready to be installed in the production string at the well location. When the well is ready for the valves to be installed, a Production Service Company representative delivers the valves to the location and supervises the installation process to ensure completions to the design specifications.

Gas Lift Equipment

PSC offers a full range of downhole gas lift equipment.


Mandrels
  • Available to fit any size production tubing
  • Same ID as tubing for maximum flow capability
  • Guard plates are mounted on the mandrel to protect the valves during installation
  • Available in various materials and thread connections to suit your tubing specifications
  • Special coatings available for corrosive & high temperature environments
  • CGM-1 mandrel is made to house 1.0” OD gas lift valves & check valves
  • CGM-2 mandrel is made to house 1.5” OD gas lift valves & check valves

Gas Lift Valves and Check Valves
Gas lift valves are the heart of the gas lift installation. The designed pressure settings of the valves & installation depths determine the ultimate success of the gas lift installation. The gas lift valves & check valves are designed to meet API specifications & can be manufactured in stainless steel or Monel materials to suit specific well conditions. Gas lift valve characteristics:
  • Large nitrogen charged dome for efficient operation
  • Range of port sizes to optimize gas passage through valves
  • Monel bellows for increased valve life
  • Replaceable Monel seats
  • 5/8”, 1.0”, & 1.5” OD valve sizes available
Gas lift check valves are spring loaded valves that eliminate the possibility of fluid back flow from the tubing back into the annulus through the gas lift valve.
  • Stainless steel or Monel material
  • Iconel springs for high temperature protection
  • Stack valves for additional protection from back flow
Multiple Well Pad Sites
Gas lift can be particularly useful on multiple well pad sites by using one compressor to lift all the wells on the location.

Gas Lift Site Schematic
Gas Lift Summary
A properly designed & installed gas lift system can be one of the most effective & economical means of artificially lifting oil & gas wells. The relatively low downhole and operational costs make this a very attractive means of producing wells. The abundance of formation gas in the Bakken play is ideal for use of the gas lift process. The large amount of gas in this particular formation can cause operational problems for other means of artificial lift, but is beneficial to producing horizontal wells by gas lift. The Bakken formation also produces fluid with high alkalinity. Gas lift valves are not adversely affected by injecting fresh water down the annulus to combat the salt issues from the formation fluid.