What the reading means
Sustained casing pressure is pressure in a casing annulus that rebuilds after it is bled off, and it signals a potential leak path in the well's barrier envelope. The well's barriers are casing, cement, tubing, and packers, and each annulus is a pressure vessel with its own story. A gauge that holds pressure after bleed-off is not a number to log and forget; it is the well reporting that a barrier is under stress. The wells that fail catastrophically almost always gave the same warning earlier, in a pressure trend that was read and filed instead of read and acted on.
The program API RP 90 describes
API RP 90 is the API recommended practice for annular casing pressure management, the industry reference for monitoring and managing pressure in casing annuli. A monitoring program means regular gauge reads, bleed-off records, trend tracking, and investigation when pressure appears or changes. The practice is built on diagnosis: identify the annulus, measure the pressure, bleed it down, watch the rebuild, and classify the source before deciding the response. The operator who tracks the trend can schedule the intervention; the operator who logs the number reacts to the failure.
The record is the program
Federal rules for OCS wells address well integrity and casing pressure under 30 CFR 250 Subpart D; on land, operator programs and state rules govern. The common thread is the record: gauge readings with dates, bleed-off events, pressure rebuild rates, and the reasoning behind each decision. An inspector cannot verify a monitoring program without the log, and an operator cannot see the trend without the data. The gap is usually the same: pressure is checked, the number goes in a notebook, and nobody compares this month's reading to last year's.
Annular pressure connects to the rest of the production record: remote monitoring, beam pump care, and well test data. If gauge reads and bleed-off events are not comparable over time, an operations audit will show which wells have a trend and which have a stack of numbers.