Page 216 - Well Control for Completions and Interventions

Completion, Workover, and Intervention Fluids 209

where:
Q is flow (or injection)rate,
7.08 3 10 23 is a correction factor for oilfield units,
k is permeability in millidarcy,
h is the net height of the formation in feet,
P r is reservoir pressure,
P wf is bottom hole flowing pressure (or kill weight hydrostatic
pressure),
μ is fluid viscosity in cp,
B is formation volume factor,
r e is drainage radius (ft),
r w is wellbore radius (ft), and
S is skin.
Example calculation:
A 10,000 ft vertical well is filled with a 9.7 ppg brine with a viscosity
of 1.2 cp and a formation volume factor of 1.
Reservoir pressure: 4750 psi.
Formation permeability: 120 mD.
Formation thickness (height): 135 ft.
Drainage radius: 2000 ft.
Wellbore diameter: 6 inches.
Skin: 0.
What loss rate could be expected if no loss circulation material is spot-
ted across the reservoir?
7:08 3 10 23 120 3 135 4750 2 5044Þ
ð
Q 5 5 3411 bbls=day
2000
1:2 3 1 3 ln 2 0:75 1 S
0:25
3411 bbls=day 5 142 bbls=h

What loss rate could be expected if a 200 cp viscous pill is spotted
across the reservoir?
7:08 3 10 23 120 3 135 4750 2 5044Þ
ð
Q 5 5 20 bbls=day
200 3 1 3 ln 2000=0:25 2 0:75 1 S
20 bbls=day 5 0:83 bbls=h
Viscous fluids make excellent loss control pills. However, viscosity
decreases as temperature increases and will degrade over time.