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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?