FIG. 4
FIG. 4a
FIG. 4b
SLICK-WATER VISCOSITY
Control
200 ppm
hypochlorus acid
100 ppm hydantoin
100 ppm 2,2-dibromo-
3-nithrilopropionamide
Chlorine dioxide
Biocides
Vi
s
co
sit
y,
cp
Vi
s
co
sit
y,
cp
5.0
4. 5
4.0
3. 5
3.0
2. 5
2.0
1. 5
1.0
0.5
0.0
4. 6
3. 2
3. 8
1. 6
Anionic friction reducer Cationic friction reducer
Anionic friction reducer Cationic friction reducer
Control 10 ppm chlorine dioxide
5
4
3
2
1
0
3. 3
4. 6
4. 8
4. 3 4. 2
3. 8
4. 2
2. 7
was tightened for a closer fit to prevent
air suction during operation. At least 2
ml of the water was collected into the
syringe, gas bubbles removed, any remaining gas and some water displaced
to 1 ml remaining, and injected into
the first broth bottle.
Filling and re-injecting 3 ml of the
fluid a few times without removing
the syringe from the bottle vigorously
mixed the broth-water. Serial dilutions
then moved 1 ml of inoculated broth
from Bottle 1 to Bottle 2, 2 to 3, 3 to
4 and 4 to 5, after mixing each bottle. These dilutions were the control
group. 7
Researchers determined the microbial demand and remaining free (
residual) chlorine dioxide to be tested.
The biocides (10-400 ppm) were injected in 100 ml of lake water and 1
ml of the treated water was placed into
different types of broth bottles.
Serial dilutions followed the same
procedures as the control group above.
The broth bottles were left at room
temperature and observed for 2 hrs- 2
weeks. Color changes, an increasingly
cloudy appearance, and the number of
colony-forming units (CFU) indicated
microbial growth.
The control group exhibited about
105 CFU/ml in thioglycolate anaerobic,
API SRB anaerobic, phenol red aerobic,
and API aerobic broths. The APB anaerobic broth showed up to 104 CFU/
ml.
Chlorine dioxide (residual concentration of 10 ppm plus
27. 5 ppm microbe demand, total 37. 5 ppm) prevented all
bacterial growth, rapidly reaching 100% kill. The biocide
broths containing hypochlorous acid, hydantoin derivatives,
and 2,2-dibromo-3-nitrilopropionamide did not reach 100%
kill. In some cases, however, they decreased the number of
CFU/ml- 1 as shown in the accompanying table.
Frac gel, slick-water test
The viscosity profile of frac fluid and slick water when heated shows if these components are affected by a biocide.
To prepare a test frac gel, potassium chloride (KCl) (4g,
2% solution) is added to tap water (200 ml) in a Waring
blender and mixed at 500 rpm to dissolve the KCl. The
blending speed is reduced to 300 rpm and biocide, a buffer,
and a gelling agent are added and mixed for 30 min. Adding
a cross-linker precedes determination of vortex closure and
or the need for a higher concentration, significantly increas-
ing costs or negatively affecting the gel or slick water.
Antimicrobial efficacy test
Water for the antimicrobial test came from a lake in Central
Alberta, Canada. Efficacy tests were done in the previously
mentioned bacteria broth bottles: APB anaerobic, thioglycolate anaerobic, API SRB anaerobic, phenol red aerobic, and
API aerobic. Samples were tested quickly to ensure accurate
results.
Researchers arranged each type of nutrient broth bottle
in a dilution series of five bottles. The metal stoppers of the
broth bottles were sterilized with ethanol in order to prevent
contamination of the media during inoculation. Presteril-ized 3-ml syringes were removed from their packaging without contamination of the tips. The needle of each syringe
