Page 199 - Well Control for Completions and Interventions

192 Well Control for Completions and Interventions

Table 5.2 Brine expansion coefficients (Krook and Boyce)
Brine type Density Expansion coefficient Density decrease in
(ppg) (vol/vol/ F) lb/gal/100 F

NaCl 9.49 2.54 3 10 24 0.24
11.46 2.39 3 10 24 0.27
CaCl 2
NaBr 12.48 2.67 3 10 24 0.33
14.3 2.33 3 10 24 0.33
CaBr 2
ZnBr 2 /CaBr 2 / 16.0 2.27 3 10 24 0.36
CaCl 2
19.27 2.54 3 10 24 0.48
ZnBr 2 /CaBr 2
At 12,000 psi between 76 and 345 F

Table 5.3 Brine compressibility coefficients (Krook and Boyce)
Brine type Density Compression coefficient Density increase in

(ppg) (vol/vol/ F) lb/gal/1000 psi
NaCl 9.49 1.98 3 10 26 0.019
11.46 1.50 3 10 26 0.017
CaCl 2
NaBr 12.48 1.67 3 10 26 0.021
14.3 1.53 3 10 26 0.022
CaBr 2
ZnBr 2 /CaBr 2 / 16.0 1.39 3 10 26 0.022
CaCl 2
19.27 1.64 3 10 26 0.031
ZnBr 2 /CaBr 2

At 198 F from 2000 to 12,000 psi
coefficients were derived experimentally by Krook and Boyce in 1984. 1
They are the coefficients listed in American Petroleum Institute (API)
Recommended Practices 13J; “Testing of Heavy Brines.” 2
Although the Krook and Boyce coefficients are widely used, they rep-
resent expansion coefficients at a given pressure; 12,000 psi. At lower
pressure coefficients are significantly different, resulting in higher expan-
sion ratios.
Tetra in their “Engineered Solutions Guide for Clear Brine Fluids” 3
4
use expansion and compression coefficients compiled by Bridges. The
values used are calculated at atmospheric pressure and 77 F, and are repro-

duced in Table 5.4.
Comparing Tables 5.2 and 5.3 (Krook and Boyce) with Table 5.4
(Bridges) reveals significant differences between the expansion coefficients
of a brine under pressure and one at atmospheric pressure.
Using the relevant data, calculating density loss and an adjusted
(increased) surface brine density is relatively straightforward. Two different
equally valid methods are described: