Annulus
Also known as: Annuli (plural)
The annulus is the space between two concentric components in a well, such as between the drillstring and the wellbore, the casing and the wellbore, two casing strings, or the production tubing and casing. Fluids can flow or be placed in this space. During drilling, mud and cuttings normally return to the surface through the annulus. During completion and production, an annulus may contain cement or packer fluid, carry injected gas for gas lift, support circulation or well-control operations, and provide a monitored barrier for well integrity. The plural is annuli.
Frequently Asked Questions
Where is the annulus?
It is the ring-shaped space outside one pipe and inside the surrounding pipe or borehole.
What is the A-annulus?
Typically the space between the production tubing and the innermost casing string.
Why is annulus pressure monitored?
Unexpected or sustained pressure can indicate communication, leakage, or a compromised well barrier.
How is the annulus used in gas lift?
Compressed gas is commonly injected down the tubing-casing annulus and enters the tubing through gas-lift valves.
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