oxidizing biocides and preservatives for microbiological control...oxidizing biocides •common...
TRANSCRIPT
Clear solutions for water treatment Clear solutions for water treatment.
Oxidizing Biocides and Preservatives
for Microbiological Control
Presentation Outline
• Introduction
– Oxidizing biocides
– Preservative biocides
• Comparative testing
• Oxidizing and preservative biocide
combinations
• Corrosion inhibition properties of
preservative biocides
• Conclusions
Oxidizing Biocides
• Common oxidizing biocides
– Bleach, chlorine dioxide, peracetic acid,
hydrogen peroxide
• Fast acting at low concentrations
• Highly reactive chemically
– Non-biocidal side reactions
– Short residual activity
• Can be corrosive
Field Water Sample
SRBs
0
1
2
3
4
5
6
7
Control Ox Biocide, 1ppm
Via
ble
Co
un
t (L
og 1
0 C
FU/m
L)
0.5 Hours 1 Hour 4 Hours 7 Days*
APBs
0
1
2
3
4
5
6
7
8
Control Ox Biocide, 1ppm
Via
ble
Co
un
t (L
og 1
0 C
FU/m
L)
0.5 Hours 1 Hour 4 Hours 7 Days*
* Indicates re-inoculation 24 hours prior to time point
No Long Term Protection
No Long Term Protection
Residual Activity of Oxidizing Biocides
Preservative Biocides
• Common preservative biocides – DMO, glute quat blends (GQ), phosphonium
polyammonium blend (PPAB), thione (DMTT)
• Can be either fast or slow acting
• Generally less chemically reactive than oxidizing biocides but can be unstable at/in: – High temperatures
– High pH
– Oxidizing environments
• Some are formaldehyde releasers
COMPARATIVE TESTING
Hydrothermal Stability of Preservative Biocides
0
1
2
3
4
5
6
7
Control DMO, 500ppm DMTT,2500ppm
GQ, 25ppm PPAB, 25ppm
Cell
Via
bilit
y, L
og
10 C
FU
/mL
Day 0 Day 7 Day 14 Day 21 Day 28 Day 56
Conditions: APB, 80°C, pH 9, 20K ppm TDS, 4 hour contact time
0
1
2
3
4
5
6
7
Control DMO, pH 8,400ppm
DMO, pH 10.5,400ppm
DMTT, pH 8,400ppm
DMTT, pH10.5, 400ppm
PPAB, pH 8,12.5ppm
PPAB, pH 10.5,12.5ppm
Via
ble
Co
un
t, L
og1
0 C
FU/m
L
1 Hour 4 Hours
Stability of Preservative Biocides vs pH
Conditions: SRB, RT, pH 8, 30K ppm TDS
Compatibility of Preservative Biocides with Chlorine
0
0.5
1
1.5
2
2.5
0 24 48 72 96 120 144 168 192 216 240
Ch
lori
ne
(p
pm
)
Time (min)
Chlorine, 2 ppm free DMO, 78 ppm ppm + Cl, 2 ppm DMTT, 50 ppm + Cl, 2 ppm
2:1 GQ, 25 ppm + Cl, 2 ppm PPAB, 12.5 ppm active + Cl, 2 ppm
OXIDIZING AND PRESERVATIVE
BIOCIDE COMBINATIONS
SRBs
0
1
2
3
4
5
6
7
Control Ox Biocide,1ppm
PPAB, 7.5ppm Ox Biocide,1ppm + PPAB,
7.5ppm
Via
ble
Co
un
t (L
og 1
0 C
FU/m
L)
0.5 Hours 1 Hour 4 Hours 7 Days*
APBs
0
1
2
3
4
5
6
7
8
Control Ox Biocide,1ppm
PPAB, 7.5ppm Ox Biocide,1ppm + PPAB,
7.5ppm
Via
ble
Co
un
t (L
og 1
0 C
FU/m
L)
0.5 Hours 1 Hour 4 Hours 7 Days*
* Indicates re-inoculation 24 hours prior to time point
Field Water Sample
Long Term Kill with Oxidizing/Preservative Biocide Combination
No Long Term Protection
Long Term Complete Kill
No Long Term Protection
Long Term Complete Kill
ClO2 company treated fracs using ClO2 and DMO. PPAB replaced the DMO at the same injection rate and was also used in the coil water.
Total of 44 wells were treated with the combination of ClO2 and PPAB. 2 wells were fraced in conjunction with a high pH x-link gel system. 2 wells were fraced in conjunction with a low pH x-link gel system. The remaining wells were fraced using a standard slick water design.
Average Pre treated APB bottle turns- 4.25 Average Pre treated SRB bottle turns- 3.75
Average bottle turns during 6 weeks of follow up flow back monitoring are less than one for average 99.99% kills. 0.62 APB 0.27 SRB No compatibility or fluid integrity issues reported from pressure pumping compan .
Significant improvement in emulsion control during flowback sampling. Overall, PPAB showed improvement in quick and long term bacteria control and fluid quality versus the previous biocide program.
Compatibility of Preservative Biocides with Chlorine
CORROSION INHIBITION
Experimental Parameters
• Linear polarization resistance (LPR) corrosion rate measurement every 5 minutes
• 3% NaCl – simple brine for screening
• 65 ˚C
• 100% water cut
• CO2 saturated, 14.7 psi
• RCE – rotating cylinder electrode simulating fluid dynamics of fluid flow in a pipeline
• 1018 carbon steel
• 1000 rpm, Reynolds Number ~1200, 3 Pa wall shear stress
LPR Background A small potential of ± 10 mV is applied around the OCP and current is measured. This polarization resistance or slope (Rp) is related to the corrosion current measured by the Stern-Geary equation (1).
Rp = Β/Icorr (1) Where Β is the proportionality constant and is calculated from the slopes of the anodic and cathodic Tafel slopes, ba and bc, as in equation (2).
Β = ba • bc / 2.3 • (ba + bc) (2) While the slopes can be calculated from actual Tafel polarizations, it is general practice to use a slope of 120, which provides a Β constant of 26.1. A potentiostat is used to run the electrochemical experiments to obtain the polarization resistance. Then knowing Rp and Β, the corrosion current can be calculated by the Stern-Geary equation. Once Icorr is known, it can be converted into a corrosion rate using equation (3), which is based on Faraday’s law.
CR = Icorr • K • EW / d • A (3) where CR is the corrosion rate. Icorr is the corrosion current in amps. K is a constant that defines the units for the corrosion rate EW is the equivalent weight of the metal in grams/equivalent d is the density of the metal in grams/cm3 A is the sample area in cm2
0.0
50.0
100.0
150.0
200.0
250.0
0.0 3.5 7.0 10.5 14.0 17.5
Co
rro
sio
n R
ate
(m
py)
Time (hours)
DMO @ 65 ˚C, 1000 rpm
and 3% NaCl
78 ppm active
0
50
100
150
200
250
300
0.0 3.5 7.0 10.5 14.0 17.5 21.0
Co
rro
sio
n R
ate
(m
py)
Time (hours)
TTPC @ 65 ˚C, 1000 rpm
and 3% NaCl
12.5 ppm active
0.0
50.0
100.0
150.0
200.0
250.0
300.0
0.0 3.5 7.0 10.5 14.0 17.5 21.0
Co
rro
sio
n R
ate
(m
py)
Time (hours)
PPAB @ 65 ˚C, 1000 rpm
and 3% NaCl
25 ppm active
ppm active dosage
TTPC reduces
the corrosion
rate by more
than 3.3 times
compared to
an untreated
well
Compatibility of Preservative Biocides with Chlorine
+ TTPC @ 10ppm
+ TTPC @ 25ppm
+ TTPC @ 10ppm
Conclusions
• Oxidizing biocides while fast acting at low concentrations are not persistent.
• Preservative biocides vary in their stability and compatibility under hydraulic fracturing conditions.
• The preservative biocide PPBA has good stability and compliments the biocidal activity of oxidizing biocides
• PPAB can protect metal from the corrosive properties of brine and oxidizing biocides
Thank you
Questions?