Gas Lifting is a secondary means of production. It is employed when formation pressure declines to the point where formation liquids can’t flow to the surface.
In a gas lift system gas is injected into the liquid in the tubing which decreases its density. Formation pressure can then flow the aerated column of liquid to the surface.
Although gas lifting is generally thought of as a method to assist a low-pressured oil well it is used extensively in low pressured gas wells that are prone to water production.
In a gas lift system gas is injected into the liquid in the tubing which decreases its density. Formation pressure can then flow the aerated column of liquid to the surface.
Although gas lifting is generally thought of as a method to assist a low-pressured oil well it is used extensively in low pressured gas wells that are prone to water production.
Gas Lift Equipment
The side pocket system is the most common. The well is initially completed with side pocket mandrels installed in the tubing string at pre-determined depths. Gas lift dummies are installed in the mandrels and are pulled and replaced with gas lift valves when the formation pressure has declined to a point where production is declining. The system can be set-up to be continuous lift or intermittent lift.A kickover tool with a pulling tool attached is used to extract the dummy. The kickover tool and running tool is used to install a gas lift valve in the mandrel.
After all the valves are installed, gas is injected into the casing and the system begins to function.
Chemical injection can also be accomplished with side pocket chemical injection valves. These can be set and retrieved the same way the dummies and valves are
The kickover tools pictured at right are used to orient a gas lift dummy or valve within a side pocket gas lift mandrel. A setting tool is installed below the kickover tool to complete the assembly.
The tools are from left to right: Camco KO Kickover Tool Camco L Kickover Tool Camco L-2D Kickover Tool.
Gas Lift Equipment – Tubing Retrievable Gas Lift Mandrel
This type of gas lift installation uses gas lift mandrels with fixed gas lift valves. Like the side pocket versions, the number of gas lift valves and their individual depths are predetermined prior to installation in the well.
- Servicing the valves requires removal of the tubing string. Should a valve fail a wireline pack-off can be placed across the mandrel until the tubing is pulled to repair or replace the valve.
Gas Lift Equipment – Annulus Safety Valve
The Annulus Safety Valve is installed above the upper gas lift mandrel. The purpose of this surface-controlled valve is to close off the annulus in the event of a catastrophic surface event.
The valve is designed to shut-in preventing the annular gas from escaping to the surface.
Circulation
A variety of devices and techniques are available to allow communication between the annulus and the tubing:
- Sliding Side Door (SSD) or Sliding Sleeve (SS).
- Side Pocket Mandrels (SPM) with shear or injection valve.
- Ported nipple.
- Exposed ports on extra long tubing seal receptacle after reciprocating seal receptacle.
- Perforating or tubing punch.
Circulation – Sliding Sleeves
- string and provide communication between the well production conduit and various annulus.Various applications include: Fluid Displacement Selective Testing Treating
Producing Multiple Zones Commingled Production
Well Killing (by fluid circulation) Kicking off wells (gas lift) Pressure Equalization Chemical Injection
The sleeve within an SSD may be shifted by: Wireline
Coiled tubing methods;
The plug is set and tested and then the sleeve is shifted. The opening of the sleeve creates a “U- tube” between the casing and the tubing allowing fluid to be circulated throughout.
The sleeve within an SSD may be shifted by: Wireline
Coiled tubing methods;
- Pressure application to the tubing after dropping or running a shifting dart; Pressure application to the annulus
- Sliding sleeves serve two purposes:
- A means of circulating fluids between the tubing and the annulus
- Accessing producing formations
The plug is set and tested and then the sleeve is shifted. The opening of the sleeve creates a “U- tube” between the casing and the tubing allowing fluid to be circulated throughout.