Page 47 - A Practical Companion to Reservoir Stimulation

PRACTICAL COMPANION TO RESERVOIR STIMULATION

EXAMPLE C-5
From Fig. 5-4, the shear rate is 50 sec-' at 100 ft and 60
Shear and Temperature Effects on sec-' at 250 ft.
Apparent Viscosity During Fracturing Thus,

Given the rheological properties in Table C-2 and the simu- pu = (47,880) (0.350) (50-0.597) = 1621 cp (C-26)
lated shear rate and temperature properties shown in Figs.
5-4 and 5-5, determine the apparent viscosities at 100 and 250 at 100 ft, and
ft along the fracture after 25% and 75% of the fluid has been p, = (47,880) (0.1169) (60-0"s7) = 506 cp (C-27)
pumped.
at 250 ft.
Solution (Ref. Section 5-3)
A. 25% offluidpumped
From Fig. 5-5 the temperature at 100 ft is 185°F and at Temp Time
250 ft is 200°F (the maximum temperature). Fromkble C-2, (OF) (hr) n' K'
the n' and K'are 0.392 and 0.258 (interpolation) and 0.4133
and 0.1 169, respectively.
From Fig. 5-4, the shear rate is 130 sec-' at 100 ft and
300 sec-' at 250 ft.
The apparent viscosity is given by 0.4145 0.3384
p(, = 47,880 K'v" -', (C-23)

and thus at 100 ft,
p,, = (47,880) (0.258) (130-" 602) = 660 cp; (C-24)
whereas at 250 ft,

p(, = (47,880) (0.1 169) (300-" 5x7) = 197 CP. (c-2-51
This is a substantial reduction in the viscosity, and it has a
major effect on the expected role of the pad fluid, which is to
generate the desired fracture widths.

B. 75% of fluid pumped
Again, from Fig. 5-5 the temperatures are 155°F and 200"F, 0.41 33 0.1 169
respectively, for the 100-ft and 250-ft locations. From Table
C-2 the rheological properties for 155°F are 0.350 and 0.403, 0.5686 0.0339
respectively. 0.6895 0.01 39
Table C-2-Flheology of a borate crosslinked fluid
containing 40-lb/lOOO gal hydroxypropyl guar.

C- 8