A well is experiencing lost circulation problems at the bottom of the casing string. A liner will be run into the well. If the liner is lowered at a maximum rate of 93 ft/min, will the surge pressures exceed the fracture gradient? Use the Bingham model and assume laminar annular How. In addition, assume the peak pipe velocity is the same as the average value.
3. Compute the annular velocities around the drillpipe (Va„) and the liner tvj
Mud 16.6 lb/gal
k ^ 0.38 liner - ratio " 7/8.5 - 0.823 k = 0.45
5. The effective annular velocities around the pipe (V^) and the liner (V,c) are:
- 0.603 - 0.38 (-1.55) = 1.192 ft/sec Vlc - 1.349 ft/sec - (0.45)( - 1.55) = 2.046 ft/sec
6, The pressure surge caused by the drillpipe is as follows (use tiq. 18.27):
p 1,500 (dH- - dp2) 225 (dH - d„) (38)(6,400X1.192) ( I5)<6,400)
1,500 (8.52 - 4,5-) 225 ( 8.5 - 4.5) = 3.716 psi + 106 psi = 110 psi
7. The pressure surge caused by the liner is:
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