Maximum Allowable Annular Surface Pressure for the A, B or C annulus, with your choice of units (default m, psi and SG). It checks every limit along the annulus and shows which one governs, with MOP and API RP 90 MAWOP.
MAASP — Maximum Allowable Annular Surface Pressure is the highest pressure that can be held at the wellhead on a given annulus (A, B or C) without exceeding the rating of any part of that annulus. It is worked out at the weakest point, then corrected for the fluid column in the annulus and the pressure backing it up.
Each annulus has its own MAASP. It is set by whichever of these runs out first: burst of the outer string, collapse of the inner string, the packer, the formation at an open shoe, the wellhead and valves, or any other component in the annulus.
The number changes when anything in the well changes: fluid swap, depletion, corrosion, a workover. Recalculate it every time.
The tool checks every depth along the annulus every few feet and reports the lowest value and where it is.
Use TVD, not MD. Hydrostatic pressure depends on vertical depth. Take packer, TOC and shoe depths from the survey.
Take the weaker of pipe body and connection. Premium connections are often rated at 100% of the pipe body, but API buttress and LTC can be lower in burst or have a leak resistance limit.
Backup pressure is the minimum case. For burst, use the lowest backup you can justify: degraded mud base fluid above the TOC, and depleted pore pressure below it.
Minimum inside pressure for collapse. Use the worst case, such as an evacuated tubing, gas-filled tubing, or a gas-lift well at low tubing head pressure.
MOP sits below MAASP. Operate below MOP and set alarms there. If you reach MAASP, the annulus is at its design limit and needs investigation.
This tool is only as accurate as the data you put in. The final MAASP and MOP for a well should be checked and approved by the well integrity engineer to your company standard.
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