Well conditions at which the annulus pressure is building up after bleed-off.
This is normal behaviour if the annulus is connected to tubing by completion design (through the tubing shoe or an open valve).
In case the annulus has a packer installed then SAP indicates that there is a breach in the packer or the inner/outer pipes of the annulus leading to a fluid leakage.
Important Notice
Not all the downhole fluid leaks expose themselves as Sustainable Annulus Pressure (SAP), like for example the casing leak below the tubing packer.
See Also
Petroleum Industry / Upstream / Petroleum Well / Well completion
[ Well & Reservoir Surveillance / Leak Detection]