This article presents the following Formation Strength Tests Calculations:

– Formation Intake Gradient (FIG)

– Effective Mud Gradient (EMG)

– Maximum Allowable Annular Surface Pressure (MAASP)

Formation Intake Gradient (FIG)

FIG (psi/ft) = LOP + (CSD x MG)

                      (CSD – RKB)

Effective Mud Gradient (EMG)

EMG (psi/ft) = LOP + (CSD x MG)

                            CSD

Maximum Allowable Annular Surface Pressure (MAASP)

MAASP (psi) = LOP – (CSD x MG)   (@ initial condition)

 

Where:

• CSD = Shoe Depth last set casing (ft TVD – RKB)
• MG = Mud Gradient (psi/ft)
• RKB = Rotary Kelly Bushings Elevation above ground level (ft)
• FBP = Formation Breakdown Pressure (psi)
• LOP = Leak – Off Pressure = Surface pressure recorded during the test (psi)