Page 259 -

222 Part III Underbalanced Drilling Systems

Illustrative Example 10.1 (Continued )

3
100 gpm
200 gpm
2.5
Instability Factor (ΔP BH /ΔP S ) 1.5
300 gpm
2

1

0.5

0
0 2000 4000 6000 8000 10000
Depth (ft)
Figure 10.10 Effect of the liquid pumping rate on the instability factor. Gas
injection rate 500 scfm, backpressure 50 psia.

1.6

1.4
Instability Factor (Δ P BH /ΔP S ) 0.8 1
1.2

0.6

0.4
0.2 500 scfm
750 scfm
1000 scfm
0
0 2000 4000 6000 8000 10000
Depth (ft)
Figure 10.11 Effect of the gas injection rate on the instability factor. Gas
injection rate 200 gpm, backpressure 50 psia.