FIG. 3a
FIG. 3
FIG. 3b
VISCOSITY PROFILE, HEATED HYDRAULIC FRACTURING GEL
Chlorine dioxide
Biocides
Vi
s
co
si
t
y
1
,0
0
0
cp
Vi
s
co
si
t
y
1
,
00
0
cp
0
20
40
60
80
100
0.35
0.55
0.75
0.95
1. 15
1. 35
1. 55
1. 75
0 20 40 60 80 100 120
Tem
perat
ure,°
C
Time, min
Control
200 ppm hypochlorous
acid
100 ppm hydantoin
derivative
100 ppm 2,2-Dibromo-
3-nitrilopropionamide
Temperature
0
20
40
60
80
100
0.00
0.20
0.40
0.60
0.80
1.00
1. 20
1. 40
1. 60
1. 80
0 20 40 60 80 100 120
T
emp
er
a
tu
re
,
°
C
Time, min
Control
10 ppm
20 ppm
50 ppm
100 ppm
Temperature
jor concern when using a guar-based
fluid. Among these microbes are ac-id-producing bacteria (APB), sulfur-reducing bacteria (SRB), and general-heterotrophic bacteria (GHB). These
can be free-floating, attached to a surface, or dormant. 3
A guar-based fluid without biocides can lead to biofilms that can
damage a formation through bioclogging (caused by GHB), microbially-in-duced corrosion (caused by APB and
SRB), or H2S production (caused by
SRB), and reduce output.
This bioclogging may require bio-film treatment or more hydraulic fracturing to increase production, either
of which raise both cost and environmental concerns about possible excessive use of chemicals. 4
Biocides can be added to stored water or as part of the pad: a high-viscos-ity fluid containing water, polysaccharide derivatives, pH control additives,
surfactants, crosslinking chemicals,
breakers, and other additives. 5 Treatment concentration depends on the
type of biocide, the method of application, contact time available, and costs.
This article evaluates chlorine dioxide solutions and three biocides
containing hypochlorous acid, hydantoin derivatives, and 2,2-dibromo-
3-nitrilopropionamide. Testing used
APB anaerobic, thioglycolate anaerobic, API SRB anaerobic, phenol red aerobic, and API aerobic microbial broth
bottles (Fig. 1) to determine the biocide concentration needed to achieve a
100% and immediate kill of microbes,
minimizing the risk of bacterial proliferation in a formation during fracturing. This level and rate of kill is difficult to achieve with commonly used
biocides.
The article also looks at the effects
of biocides on the viscosity of hydrau-lic-fracturing gels and slick water at
elevated temperature and pressure.
Biocides can affect the structure of
fracturing fluids, rendering them ineffective. 6
Total kill may not be achieved by
some biocides because of low efficacy
