Maximum Allowable Annular Surface Pressure from Shoe EMW Calculator
Enter shoe EMW, current mud weight, and shoe TVD. The calculator returns the annular surface pressure margin in psi.
Calculation context and source notes
Maximum allowable annular surface pressure estimates the casing-shoe pressure limit by comparing shoe equivalent mud weight with current mud hydrostatic pressure.
Use it for well-control margin checks and pressure-limit awareness while circulating or shutting in a well. Compare the result with the current casing, shoe, and procedural limits before setting an operating limit.
Solves for
MAASP (psi)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns MAASP = 1,619.8 psi. Defaults demonstrate the implementation; they are not recommended field values.
13.95
9.5
7000
Input definitions
MW_max
ppgMaximum Allowable Equivalent Mud Weight at Shoe
MW
ppgCurrent Mud Weight
TVD_shoe
ftCasing Shoe True Vertical Depth
Output definitions
MAASP
Maximum Allowable Annular Surface Pressure
MW_max
Maximum Allowable Equivalent Mud Weight at Shoe
MW
Current Mud Weight
TVD_shoe
Casing Shoe True Vertical Depth
Engineering use, assumptions, and limits
Use it for well-control margin checks and pressure-limit awareness while circulating or shutting in a well. Compare the result with the current casing, shoe, and procedural limits before setting an operating limit.
Assumptions
- Shoe strength is represented by equivalent mud weight at shoe depth.
- Current mud weight is uniform to the shoe.
- The calculation uses US field units.
Limitations
- Does not replace leak-off, formation integrity, or well-control program limits.
- Does not include weak zones above or below the shoe.
Common mistakes
- Using bit depth instead of shoe depth.
- Confusing MAASP with allowable casing pressure at another depth.
- Ignoring safety factors required by the well program.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Drilling Manual. MAASP In Drilling Definition, Calculations.
Open source reference