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Drilling engineering formulas and calculations Chapter 2 139
2.153 Mudcake permeability—Formation invasion
Input(s)
m: Viscosity (cP)
h(t): Filtrate Height (in.)
x c (t): Mudcake Growth by time (in./s)
Dp: Pressure Change (psi)
t: Time (s)
Output(s)
2
k: Viscous Shear Stress at the outer Mudcake boundary (lb/in. )
Formula(s)
m htðÞx tðÞ
c
k ¼
ð 2tDpÞ
Reference: Chin, W. C. (1995). Formation Invasion, Page: 95.
2.154 New pump circulating pressure
Input(s)
P p : Present Circulating Pressure (psi)
q n : New Pump Rate (spm)
q o : Old Pump Rate (spm)
Output(s)
P c : New Circulating Pressure (psi)
Formula(s)
2
q n
P ¼ P
c p
q o
Reference: Lapeyrouse, N. J., 2002, Formulas and Calculations for Drilling, Production and Workover, Second Edition,
Gulf Professional Publishing, Page: 27.
2.155 Nozzle area calculation
Input(s)
F: 1st Nozzle Size (in.)
C: 2nd Nozzle Size (in.)
B: 3rd Nozzle Size (in.)
Output(s)
2
N a : Nozzle Area (in. )
