Improved control of SRB s in hydraulic fracture fluid using chlorine dioxide

Improved control of SRB s in hydraulic fracture fluid using chlorine dioxide

Hypothesis: Is ClO 2 an Effective O&G Water Treatment Option Why SRB Control is Important: Long term well production Scope of the Study: Investigate the efficacy of commonly used biocides for controlling Sulfate Reducing Bacteria (SRBs) in waters which could be used for hydraulic fracturing Loss of revenue from uncontrolled bacterial growth 2

ClO 2 is different from traditional oilfield biocides Traditional Biocides Generally liquids and solids General application rates; not specific to each water Relies on historical data to determine the dose No real time control feed back due to slow kill (hours) Bacterial resistance questions Pump off application technique Generally significantly higher quantities required Not usable in drinking water Chlorine Dioxide Dissolved gas in water Specific application rate; determined by demand test Specific to each site and water condition Real time control due to quick kill (minutes) No bacterial resistance questions On demand on site generation Generally significantly lower quantities required Drinking water approved; environmentally acceptable 3

Study Methods Conventional biocides Glute/Quat 2:1 ratio Glute THPS PAA Newer technology Chlorine dioxide (DuPont) All microbiology by modified API RP38 / NACE TM0194-2004 All bottles/dilutions were done in triplicate and reported as Most Probable Number estimates (MPN) Efficacy was studied in various ratios of production and fresh water Produced water was from Marcellus Shale (Washington County, PA) and Fayetteville Shale (Van Buren County, AR) Fresh water was collected just prior to each study from the Brandywine River in Wilmington, DE 4

Production of Chlorine Dioxide and Demand Study Chlorine dioxide was generated in the laboratory using sodium chlorite solution, sodium hypochlorite (bleach), and hydrochloric acid, in DI water to form a stock of ~3,000 mg/l. "The reactants and stoichiometry are the same used in DuPont Oxychlor MGIII chlorine dioxide generators used in field applications "The bleach was assayed and adjusted prior to use "DuPont ADOX 3125 used as the sodium chlorite source ClO 2 Demand Test Method 1. A subsample of production water was selected 2. ClO 2 was slug dosed at various concentrations 3. The ClO 2 treated water sample was held for 30 minutes This hold time simulates hold times in frac tanks with on the fly ClO 2 treatments 4. The ClO 2 residual was assayed using a procedure modified from Standard Methods 4500-ClO2 E 5. The dose that achieved a 1.0 to 5.0 ppm ClO 2 residual was used in the studies 5

Partial Analysis of Water Used Parameter 100% Fresh (Brandywine River water) Al <1 8 <1 B <1 14 6 Ba <1 1,680 10 Br - 0 473 <1 Ca 24 10,900 226 Cl - 39 59,420 1,750 Fe <1 45 18 K 3 245 8 Li <1 76 13 Mg 10 725 72 Mn <1 8 <1 Na 19 20,600 8,530 11 1 ND NO 3 - S 6 230 1 Si 6 9 10 Sr <1 2,645 91-2 SO 4 18 8 ND All values as parts per million (ppm) 100% Marcellus Produced Water ND = Not Done 100% Fayetteville Produced Water 6

Treatment Regime Water was used either neat or blended at the desired ratio Water/blended water was inoculated with a cocktail of bacteria to approximately 10e6/ml of each according to API RP38 Biocides were added at the target concentration " ClO 2 dosed to achieve a residual of 1.0 to 5.0 ppm (mg/l) after 30 minutes " Chemical biocides used at either their low or mid range specified on their US EPA label Treated water was allowed to stand for 30 minutes Hold time simulated the post-treatment hold in frac tanks prior to the blender Treated water was sampled and SRB bottles were inoculated (shot) 7

Biocide Dosages: Orders of Magnitude 100 90 80 70 60 50 40 30 20 10 0 MARCELLUS LOW DOSE 100 ClO 300 2 required considerably less volume of chemistry 50/50 200 20/80 100 ClO 10/90 2 is the only biocide that allows immediate validation of efficacy 0 CLO2 Glute/Quat THPS Glute 600 500 400 MARCELLUS MEDIUM DOSE 100 50/50 20/80 10/90 100 90 80 70 60 50 40 30 20 10 0 Residual Measurement FAYETTEVILLE LOW DOSE 100 50/50 20/80 10/90 FAYETTEVILLE MEDIUM DOSE 600 500 400 300 100 200 50/50 100 20/80 0 10/90 8

Representative bottle turns When Biocides work = zero turn When biocides don t work= >1 log 9

Results: Surviving SRBs After 30 Minute Contact Time Microbial Efficacy: Marcellus Shale Water Sulfate-Reducing Bacteria (SRB) 8 100% MSW- lo 100% MSW- mid 50:50- lo 50:50- mid 80:20- lo 80:20- mid 90:10- lo 90:10- mid 7 Log 10 MPN/ml 6 5 4 3 2 1 0 ClO2 Test Inoc Glut/Quat THPS Glut All ClO 2 test results were below the level of detection (i.e., <3.0 CFU/ml or 0.48 log 10 /ml) 10

Results: Surviving SRBs After 30 Minute Contact Time Microbial Efficacy: Fayetteville Shale Water Sulfate-Reducing Bacteria (SRB) 100% FSW-lo 100% FSW-mid 50:50-lo 50:50-mid 80:20-lo 80:20-mid 90:10-lo 90:10-mid 9 8 Log 10 MPN/ml 7 6 5 4 3 2 1 0 ClO2 Test Inoc Glut/Quat THPS Glut PAA 11

Results ClO 2 Mechanism: Cell destruction " Sulfate-reducing bacteria and acid producing bacteria are especially vulnerable to chlorine dioxide oxidation " Chlorine dioxide attacks the fundamental physiology of bacteria therefore prohibiting both anaerobic and aerobic bacteria from developing resistance and eliminates the need to alternate biocide treatments " Chlorine dioxide is not only an effective biocide, its oxidizing properties will destroy hydrogen sulfide (H 2 S) and iron sulfide (FeS) contaminants in the system and is ideal for impounded produce water treatment " Reminder: ClO 2 is not Chlorine 12

CLO2 effect on WV Produced water " Raw Water " Treated with CLO2 & polymers " Settled Solids with measurable CLO2 residual 13

Conclusion ClO 2 least bottle turns by 12x ClO 2 PAA Glut/Quat THPS Glut Marcellus 1 ND 4 3 2 Fayetteville 1 2 4 3 5 " The above results are based on the average log 10 reduction for the eight studies (i.e., 8 different blends of production and river water) " Biocide Rankings for SRB Efficacy only (1= best performer, 5=poorest performer) " ClO 2 was the best performer in all studies (the only antimicrobial to have 13 zero bottle turns; next closest were PAA & Glut/Quat each with 1) " Key Learning: Water source & blend percentage DOES impact biocide performance 14

Results from a Marcellus Hydraulic Fracture Green = Acceptable; Yellow = Questionable; Red = High Bacteria Parameter Stage Treatment SRB (CFU/ml) 12/29/2011 1 ClO 2 0 12/29/2011 2 ClO 2 0 12/30/2011 3 ClO 2 0 12/31/2011 4 ClO 2 0 12/31/2011 5 ClO 2 0 1/1/2012 6 ClO 2 0 1/7/2012 7 Glut/Quat 10 1/8/2012 8 ClO 2 0 1/9/2012 9 Glut/Quat n/a 1/10/2012 10 Glut/Quat 100 1/11/2012 11 Glut/Quat 0 1/12/2012 12 Glut/Quat 10 1/13/2012 13 Glut/Quat 0 1/14/2012 14 Glut/Quat n/a 1/15/2012 15 ClO 2 0 1/15/2012 16 Glut/Quat 0 1/16/2012 17 Glut/Quat 1,000 1/17/2012 18 Glut/Quat 1,000 1/17/2012 19 Glut/Quat 100 15 Copyright 2012 DuPont. All rights reserved. The DuPont Oval Logo, DuPont, The miracles of science, Adox, Headline, and Oxychlor are trademarks

Study Summary No other biocide provided similar kills When applied so that the residual is >1.0 ppm, ClO 2 provides 99.999% kill of SRBs within 30 minutes of contact The efficacy of ClO 2 was not impacted by large variations in water quality The efficacy of ClO 2 has been demonstrated at multiple wells in the Marcellus play DuPont believes similar efficacy will occur in all other plays Why SRB Control is Important: Increased Profitability Increasing long term well production Lower corrosion rates (SRB s controlled) 16 Copyright 2012 DuPont. All rights reserved. The DuPont Oval Logo, DuPont, The miracles of science, Adox, Headline, and Oxychlor are trademarks

Beyond SRB s: ClO 2 Effect on FeS in Oil/Water Emulsion Control After ClO 2 17

Safe & Effective CLO2 Systems Implementation Choosing the right application partner is critical. Look for (at a minimum): " Safety Training, Technical Support, Analytical, and Logistic infrastructure ClO 2 Operator Training Transport and resupply of precursors Preplanning water chemistry analysis " Mobile equipment integration and rigging safety requirements Monitoring for ClO 2 emissions Mixing header integration and sample/control points Rigging sub-surface discharge into frac tanks and ponds Rigging to balance ClO 2 addition to multiple water sources " Compliance Reporting Real time control variable trends Confirmation real time analytical results 18

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