## Utilizing Ultraviolet Light to Minimize Biocide Usage During Stimulation Operations Joseph Sinnott Supervisor, Completions Engineering

### Seeking a Cleaner, Greener Kill  Motivation for UV trial  EQT’s bacteria baseline  Overcoming initial concerns  Implementation  Results and limitations  Path forward

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### Environmental & Economic Motivation  172 planned horizontals in 2013  Increased use of recycled water • 98% of flowback water • 90% of drilling water • 60% of produced water  Over 1 billion gallons of frac water in 2013  500,000 gallons of biocide at standard loadings • 3% of stimulation costs • 12-15% of chemical volumes

www.eqt.com 3www.eqt.com 4 SRB Present Serious Issues in Production and Water Quality  SRB – Sulfate Reducing Bacteria • Sulfates reduced; sulfides produced  Why to avoid bacteria • H 2 S • Microbiologically influenced corrosion • Downhole scaling ( FeS ) • Nasty flowback water SRB

“Effects of Sulfate Reducing Bacteria on the

Corrosion of X-65 Pipeline Carbon Steel,” NACE Corrosion 2012 Conference Multi- Chem Marcellus Shale Biotechnology Presentation, Sept 2012Few Red Flags in Produced Water  Two independent studies demonstrate efficacy • Up to 3 years of production • Under 2 ppm H 2 S • 2 or less SRB bottles turned

 Goal: Achieve comparable results via greener means www.eqt.com 5Baseline Biocide Treatment During Frac 

###  Tributyl tetradecyl phosphonium chloride • TTPC • Quarternary Amine • 0.5 gpt under standard conditions 

###  Effective at surface and downhole • Kill study confirmations • Reduced performance as chlorides increase 

###  On-the-fly blending of impaired water • 100 bpm • Up to 100% recycled water www.eqt.com 6Avoiding the Light  What about our nasty water?  Can we treat at 100 bpm?  Real-time confirmation of effectiveness?  Where is the long-term protection?

www.eqt.com 7Transmittance: Will the Light Penetrate?

www.eqt.com 8 UV Treatment Operation Range Operating Range ExceededEnhanced Clarity Through Testing  Bacteria bottles run every 2-3 stages

• Tanks • Post-UV treatment • Post-blender  Blender contamination  Transmittance measured throughout stage  Biocide added downstream as needed www.eqt.com 9Implementation and Results  Initial trials in July 2012  Transmittance has limited usage to 53%  650 stages and 190,000,000 gal treated • 70,000 less gal of biocide • 22% cost reduction  Equivalent kill to standard biocide loadings • Moderate  slight SRB concentrations • 2 bottle reduction targeted

www.eqt.com 10The Challenges of On-the-Fly Treatments  Incubation lag times  Continuous testing  Mechanical limitations • Physical footprint • Diesel-based equipment  Extremely variable water quality • Cannot “set it and forget it” • Approaching the ceiling of effectiveness  Potential effects on treatment pressures • Biocide allows faster hydration of friction reducer • 100 to 200 psi treating pressure variations www.eqt.com 11Stage-to-Stage Transmittance Variations

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0 0.2 0.4 0.6 0.8 1 1.2 1.4

1 4 7 10 13 16 19 22 25% TransmissionFR and Biocide concentration (gpt)

Stage Greene County Marcellus Well - 48% Treated

FR- calc conc Biocide-calc conc Transmission Average UV Cut-OffReduced Biocide and Increased Treating Pressures Have Not Affected Fracs to Date

www.eqt.com 13 0 0.2 0.4 0.6 0.8 1 1.2 1.4

3 8 14 20 25 30 35 41 47 65 83 88Biocide and FR Concentration (gpt)

% Transmittance Average of FR concentration Average of Biocide ConcentrationA Cleaner, Greener, and Part-Time Killer  UV treatment + biocide is current EQT SOP  Minimal pre-treatment (and cost) a top priority • Logistical benefits to minimal treatment • No short or long-term effects observed  35% reduction in biocide a great first step • Technological advances to handle nastier water • Cost-effective pre-treatment options

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