MAASP / MASP Calculator

    Calculate Maximum Allowable Annular Surface Pressure (MAASP) and Maximum Allowable Shut-In Pressure (MASP) for well control operations.

    Calculation Inputs

    Current drilling fluid weight.

    Vertical depth from surface to the point of interest.

    Depth of the last casing shoe (true vertical depth).

    Leak-off or FIT pressure at the casing shoe (optional).

    What Is MAASP in Well Control?

    Maximum Allowable Annular Surface Pressure (MAASP) is the highest surface pressure you can safely hold on the wellbore without breaking down the formation at the casing shoe. It is a critical limit during kick detection, shut-in, and well kill operations.

    The calculator uses the selected mud weight, true vertical depth (TVD), casing shoe depth, and optional FIT/LOT data to estimate the pressure window available at the casing shoe. If no formation integrity test is provided, a default 0.8 psi/ft formation gradient is applied.

    MAASP Calculation Example

    As an example, assume:

    • Mud weight = 10.0 ppg
    • Casing shoe depth = 5,000 ft
    • True vertical depth (TVD) = 8,000 ft
    • FIT pressure at shoe = 3,000 psi

    Hydrostatic pressure at the shoe is:

    Pshoe = 0.052 × 10.0 × 5,000 ≈ 2,600 psi

    The available MAASP at surface is then:

    MAASP = 3,000 − 2,600 ≈ 400 psi

    Any planned shut-in or kill operation must keep surface pressure at or below this value to avoid fracturing the formation at the casing shoe.

    Assumptions and Limitations

    • Static conditions (no circulating friction) are assumed.
    • Uniform mud weight is used between surface and TVD.
    • Formation strength is represented by FIT/LOT data or a default gradient when not available.
    • Always compare calculated values with company procedures and well-specific engineering limits.

    This tool is intended as a quick engineering reference. Always follow your company's well control guidelines and verification process when setting operational limits.

    Basic Formula:

    MAASP = FIT − Pshoe

    Maximum safe surface pressure at casing shoe

    Hydrostatic Pressure:

    Pshoe = 0.052 × MW × CSD

    If no FIT provided, uses 0.8 psi/ft gradient

    MAASP: Maximum Allowable Annular Surface Pressure
    FIT: Formation Integrity Test pressure (psi)
    MW: Mud Weight (ppg)
    CSD: Casing Shoe Depth (ft)
    TVD: True Vertical Depth (ft)

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