Bleeding the annulus and checking up if the annulus pressure builds-up again, which is called Sustainable Annulus Pressure or SAP.

This is a primary check-up for a possible fluid leakage in the annulus.

It's a simple and cheap procedure but it only reveals the leakage and can not locate it.

It only works if the surface pressure in the annulus is above surface air pressure so that it can be detected by a wellhead pressure gauge.

Otherwise it will need Annulus Pressure Testing @ Leak Detection to check for the possible leakage.

See Also

Petroleum Industry / Upstream /  Data Acquisition / Well & Reservoir Surveillance / Leak Detection