Prerecorded Information

Prerecorded Information

Maximum anticipated surface pressure

Two methods are commonly used to determine maximum anticipated surface pressure:

Method 1: Use when assuming the maximum formation pressure is from TD:

Step 1

Determine maximum formation pressure (FPmax):

Step 2

Assuming 100% of the mud is blown out of the hole, determine the hydrostatic pressure in the wellbore:

Step 3

Determine maximum anticipated surface pressure (MASP):

• Example: Proposed total depth = 12,000 ft

• Maximum mud weight to be used in drilling well = 12.0 ppg

• Safety factor = 4.0ppg

• Gas gradient = 0.12psi/ft

Assume that 100% of mud is blown out of well.

Step 1

• FPmax = (12.0 + 4.0) 0.052 12,000 ft

• FPmax = 9984psi

Step 2

• HPgas = 0.12 12,000ft

• HPgas = 1440psi

Step 3

• MASP = 9984 ? 1440

• MASP = 8544psi

Method 2: Use when assuming the maximum pressure in the wellbore is attained when the formation at the shoe fractures:

Step 1

Determine fracture pressure, psi:

Step 2

Determine the hydrostatic pressure of gas in the wellbore (HPgas):

Step 3

Determine the maximum anticipated surface pressure (MASP), psi:

• Example: Proposed casing setting depth = 4000 ft

• Estimated fracture gradient = 14.2 ppg

• Safety factor = 1.0 ppg

• Gas gradient = 0.12 psi/ft

Assume 100% of mud is blown out of the...