TECHNICAL INFORMATION
ClO2: COMPATIBLE WITH FRAC CHEMISTRY
Benefits of using ClO2 for on-the-fly treatment of
hydraulic fracturing water:
• Highly effective on both vegetative bacteria and
bacterial spores
• Effective at lower dosages than other biocidal
technologies
• Allows real time dosage monitoring and residual control
• Has a proven and sustainable environmental footprint
ClO2 offers excellent compatibility with chemicals
commonly used in hydraulic fracturing operations (e.g.,
friction reducers, scale inhibitors, pH adjusters, corrosion
inhibitors, chelating agents).
NO IMPACT ON FRICTION REDUCERS
Figure 1 shows standard friction loop test results using an
anionic polyacrylamide friction reducer in a blend of 40%
produced water and 60% surface water. Over a wide
range of flow rates, the percent friction reduction is not
significantly affected at two elevated levels of residual
chlorine dioxide. Furthermore, even an extremely high
level of residual chlorite ion does not have a negative
impact on percent friction reduction. (Note: For biocidal
efficacy, 1-5 ppm of residual chlorine dioxide is effective,
and residual chlorite ion levels are typically less than 50 ppm.)
Figure 1. Effect of residual chlorine dioxide and chlorite ion
on friction reducer performance.
Anionic Friction Reducer in 40% Produced Water, 0.5 gpt, pH 5.7-6.0
100
10 gpm
80
% Friction Reduction
Chlorine dioxide (ClO2) is a powerful biocide that has
been used commercially for over 25 years to treat
water in oilfield applications to control microbiological
activity, prevent souring, and improve flow assurance.
Recently, with the rapid development of unconventional
shale gas plays, ClO2 has emerged as a leading
microbiological control technology for hydraulic
fracturing water disinfection.
15 gpm
20 gpm
10 gpm
25
30
60
Control, no ClO2
40
125 ppm chlorite ion
6.8 ppm residual ClO2
20
0
31.5 ppm residual ClO2
0
5
10
15
20
Time (min)
35
ClO2: A SELECTIVE OXIDANT FOR HYDRAULIC
FRACTURING FLUID TREATMENT APPLICATIONS
There is a potential for increased formation fouling from the
progressive precipitation of soluble metal ions in downhole
fracturing fluids. Typically, a portion of the iron and
manganese in top side produced waters reused downhole
react with atmospheric oxygen to form insoluble precipitates.
These precipitates can be removed through filtration, but
typically aren’t because they form too slowly. A ClO2
treatment program allows soluble iron (Fe) and manganese
(Mn) to be more quickly and completely precipitated top
side, so the precipitates can be removed from the water using
simple filtration or enhanced settling methods.
Fe AND Mn OXIDATION BY ClO2
ClO2 oxidizes soluble Fe2+ and Mn2+ to insoluble Fe3+
and Mn4+, and these ions rapidly hydrolyze to produce
insoluble hydroxide and oxide precipitates. Free mineral
acidity (H+) is also formed in this reaction process.
Depending upon the concentration of oxidizable transition
metal ions and the natural buffering potential in the water,
the pH of the treated water may be significantly lowered
when transition metal ions are oxidized by any oxidizer,
including atmospheric oxygen. Soluble metal ions, the
precipitates of oxidized metal ions, and pH suppression
associated with soluble metal ion oxidation all have
potential negative impact on friction reducer performance
in fracturing fluids.
A ClO2 treatment program allows soluble metal ions to be
more quickly precipitated top side and removed via
filtration or enhanced settling methods. The pH of the
treated water can then be easily adjusted to optimize
friction reducer performance in the frac fluids.
Table 1 shows data for the oxidation of Fe2+ by ClO2 in
buffered deionized water. It can be seen that in moderately
buffered water, ClO2 oxidation of Fe2+ concentrations at
or above about 50 ppm causes the solution pH to be
lowered into the range of 3.0-3.5.
Table 1. ClO2 Demand After 30 minutes with Fe2+ in 80 ppm Total Alkalinity Deionized Water
Added Fe2+ (ppm)
Initial pH
ClO2 Applied Dose
(ppm)
pH after ClO2
Addition
ClO2 Residual (ppm)
ClO2 Demand (ppm)
0
6.1
30
6.0
28.1
1.9
25
6.1
30
5.5
15.9
14.1
50
6.1
30
3.4
13.2
16.8
75
6.1
30
3.2
10.5
19.5
100
6.0
30
3.0
4.2
25.8
SUMMARY
• Residual ClO2 and chlorite ion in fracturing fluids will
not impact friction reducer performance.
• Soluble metal ions, the precipitates of oxidized metal
ions, and pH suppression associated with metal ion
oxidation can each have a negative impact on friction
reducer performance.
•ClO2 provides a rapid and effective means to oxidize
soluble metal ions and remove them from fracturing
fluids via top side filtration or conventional settling
methods.
• The pH of fracturing fluids treated with ClO2 can be
easily adjusted to the optimal pH for friction reducer
performance.
For more information, contact us at
1.800.477.6071 or visit
www.chlorinedioxide.dupont.com
The information set forth herein is furnished free of charge and based on technical data that DuPont believes to be reliable. It is intended for use by persons having technical skill, at their own
risk. Because conditions of use are outside our control, we make no warranties, express or implied, and assume no liability in connection with any use of this information. Nothing herein is to be
taken as license to operate under or a recommendation to infringe any patents.
Copyright © 2014 DuPont. All rights reserved. The DuPont Oval Logo, DuPont™, and The miracles of science™ are registered trademarks or trademarks of E.I. du Pont de Nemours and Company
or its affiliates.
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