Page 247 - Air and gas Drilling Field Guide 3rd Edition

238 CHAPTER 9 Aerated Fluids Drilling

0.05

0.01
CN L

0.001
0.001 0.01 0.10 1.0
N L

FIGURE 9-7. Nondimensional CNL versus nondimensional NL [5].

where
2
3
Y ¼ 2:69851 þ 0:15841X 1 0:55100X þ 0:54785X 0:12195X 4
1 1 1
and
X 1 ¼ log N L Þ þ 3:
ð
Once the value of parameter CN L has been determined, it is used to calculate
the value of the nondimensional group (at depth and pressure position along the
annulus pressure gradient)
N vL ðCN L Þ P 0:1
;
0:575
N vG N D P a
2
2
where P a is the atmospheric pressure (lb/ft abs, N/m abs) and P is the pressure
2
2
at the calculation location at depth (lb/ft abs, N/m abs).
The second empirical correlation chart is given in Figure 9-8 [5]. Guo and col-
leagues [19] found that Figure 9-8 can be replaced by the following correlation
equation:

y L ¼ 0:10307 þ 0:61777 log X 2 Þ þ 6 0:63295 log X 2 Þ þ 6 2

c ð ð
3 4
þ 0:29598 log X 2 Þ þ 6 0:0401 log X 2 Þ þ 6 ; (9-16)
ð
ð
where
0:1
ð
N vL CN L Þ P
X 2 ¼ 0:575 : (9-17)
N vG N D P a