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Mud Hydraulics Fundamentals 59

Surface equipment: Combination 2
Mud weight: 9.5 ppg
Consistency index: 25 eq. cp
Behavior index: 0.85
Mud flow rate: 300 gpm
2.5 Predict the surge pressure generated by a 5½-in casing string under
the following conditions, and predict whether the total borehole
pressure will exceed the formation fracture gradient. Assume that the
casing is effectively “closed” with a float shoe and laminar flow in
the annulus.
Casing depth: 4,100 ft (1,250 m)
Fracture gradient: 0.80 psi/ft
Hole diameter: 7⅞ in
Mud weight: 15 ppg
Plastic viscosity: 30 cp
Yield point: 12 lb/100 ft 2
Pipe velocity: –100 ft/min (the negative sign denotes downward
velocity)
2.6 Run the computer program Cuttings Slip Velocity.xls to perform
sensitivity analyses with various cuttings and fluid properties. What
can you conclude?