Gas Lift complies with the dual barrier policy
Many types of equipment are used to produce a Gas Lift well. It is important to mention that a Gas Lift well easily accommodates a packer and a downhole safety valve. Hence, it is compliant with the dual barrier policy that any major oil & gas company follows.
Regulate the flow of Gas Lift in the well
To inject gas lift in a well, first you need to have a valve to regulate the flow of gas injected in your tubing-casing annulus. This valve is called a gas lift choke or a flow control valve. Once your gas lift is in your casing, it needs to find its way to the tubing. For that, you need to have gas lift mandrels equipped with gas lift valves. The combination of the two will allow communication between the casing and the tubing.
Conventional Gas Lift Mandrels and Side Pocket Mandrels
There are 2 main types of gas lift mandrels:
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- The conventional gas lift mandrels, for which the gas lift valve is screwed on the mandrel. Hence, replacing a valve requires pulling the entire completion out of hole.
- The side pocket mandrels, for which the gas lift valve is installed with a kickover tool using a slick line unit. The advantage of this system is that you can replace the valve in the mandrel without pulling out the entire tubing. You only need to pull the valve out of hole and run a new one.
Main types of Gas Lift Valves
There are 3 main types of gas lift valves:
- Dummy valves which act as a plug when you do not need to inject gas lift across your mandrel. This is often the case as a gas lift completion using side pocket mandrels can work for more than a decade. Hence, as the production conditions change (for instance due to reservoir pressure depletion over time), you need to adapt your gas lift design and may want to stop injecting gas lift across a specific mandrel
- Orifice valves are used as continuously open valves. One is usually installed in the lowest mandrel through which you want to inject your gas lift at the end of your unloading sequence. This is called the service valve. The most common type is square edge orifice, but you also have a fancier version where your orifice has a venturi shape (aka Nova valve by Schlumberger).
- Unloading valves which are calibrated to open and close under certain conditions. Injection Pressure Operated (IPO) valve is the most common type of unloading valve. In this case, the valve will open once the casing pressure has reached a certain value and will close once it decreased below another value.
A good understanding of your gas lift well requires precise knowledge of all these equipment and many other. This is the necessary first step to find solutions to maximize gas lift well production.
