Maximum Initial Shut-In Casing Pressure (MISICP) or Maximum allowable shut in casing pressure is the initial shut-in casing pressure that will exceed formation strength at the casing shoe resulting in broken formation at the shoe.
How can we know and calculate the MISICP?
Leak Off Test (LOT) will tell you the maximum pressure which the shoe can withstand before breaking formation at the shoe. The LOT is the combination of surface pressure and hydrostatic pressure therefore you can apply this principle to calculate the MISICP.
The MISICP formula is listed below:
MISICP, psi = (LOT, ppg – Current Mud Weight, ppg) x 0.052 x TVD of shoe, ft
Please see the example demonstrating how to calculate the MISCIP by using the following information:
LOT = 15.0 ppg
Current mud weight = 10.0 ppg
Casing shoe depth = 4526’MD/4200’TVD
MISICP, psi = (15 – 10) x 0.052 x 4200
MISICP = 1,092 psi
Note: Please ensure that you use the TVD for calculating the MISICP.