civil and environmental engineering 1 

# Reuse%of%Produced%Water%for% Hydraulic%Fracturing%

Radisav%D.%Vidic,%Ph.D.,%P.E.% Department!of!Civil!and!Environmental!Engineering! University!of!Pi7sburgh,!Pi7sburgh,!PA!15261!civil and environmental engineering 

# Produced Water Reuse Considerations

• Quantity

– Large: justify effort to reduce fresh water needs in drought-sensitive areas

– Small: blend to reduce disposal challenges


### • Quality

– Impact on water quality after mixing with makeup water


### • Legal issues

- Many lease arrangements require purchase of groundwater from landowner

- Groundwater wells are drilled by operators and water is sold to operators by landowner 2civil and environmental engineering 

# Early Produced Water ( Flowback )

3 Formation Initial (10 days) Water Volume % Needed for Next Well Mississippi Lime, Permian basin > 30,000 bbl > 50% Barnett, Eagle Ford, Niobrara, Utica, (Marcellus) 8,000-30,000 bbl 10-40 % Haynesville, (Marcellus) 8,000 bbl < 10% Mantell , M. SPE Workshop, Ft. Worth, TX, March 2013.civil and environmental engineering 

# Long-Term Produced Water

4 Formation Produced Water Volume ( bbl /MMCF) Remarks Mississippi Lime, Permian basin > 200 Very high produced water generating play Barnett 70-200 High volumes of natural formation water present in/near target Niobrara, Eagle Ford 25-70 Relatively desiccated formation Marcellus, Utica, Haynesville < 25 Highly desiccated formation, capillary pressure binds water (imbibition) Mantell , M. SPE Workshop, Ft. Worth, TX, March 2013.civil and environmental engineering 

# Produced Water Quality Considerations

• Defining the optimal fresh to flowback water ratio to identify the maximum percentage of flowback that can be used in the frac fluid • Determining the optimal chemical composition of frac fluid using flowback water to ensure an effective frac without over spending on treatment • Identifying the maximum TDS, bacteria, barium, chloride and pH levels that can be present without causing scaling, corrosion or friction • Evaluating the optimal water chemistry for polymer based frac gels to achieve a fluid that can carry optimal volumes of proppant whilst still being cost effective 5civil and environmental engineering 

# Frac Fluid Design

6 Parameter Limit Consideration pH 6.0 – 8.0 Fluid stability, Scaling Chlorides < 20,000 mg/L Fluid stability Iron < 20 mg/L Fluid stability Ca , Mg, Ba, SO 4 , CO 3 f(P, T, pH) (~350 mg/L) Scaling Bacteria Count < 100/100 mL Bacterial growth Suspended Solids < 50 mg/L Well plugging Oil and Soluble Organics < 25 mg/L Fluid stability Hydraulic Fracturing Expert Panel, 9/26/07civil and environmental engineering 

# Water Quality Considerations
• Fresh water was the dominant source for many years • These limits represent the least common denominator (everyone was comfortable) • No tests with actual fluids to establish true chemical limits • Product manuals were often an exercise of “copy and paste”

7 Water quality established when: • One rig, one well, one frac (one lateral, few stages) • Fresh water widely available • Ample disposal capacity • Reuse of produced water not even on the radar screen Present situation: • One rig, multiple wells • Each lateral with many (10-25) stages • Fresh water under scrutiny • Reuse of produced water is a necessity in some playscivil and environmental engineering 

# Water Quality Considerations
• Who makes the decision?

- In-house engineer, completions engineer, sales engineer

• Water quality requirements should be developed based on actual water chemistry

• Economics drives the choices

- Focus on minimal water treatment to promote reuse

• Key driver for water quality requirements is the frac fluid performance 8civil and environmental engineering 

# Hydraulic Fracturing Systems

9 

# Slickwater Linear Gel Cross-linked Gelcivil and environmental engineering 10 

# Slickwater System

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00

0 10 20 30 40 50 60 70psi/ft
Rate (L/min) Pressure in a 0.5" Pipe vs. Rate Pure Water Goal with FR 

### Friction reduction is the key issue with pure slickwater fracturingcivil and environmental engineering 0 10 20 30 40 50 60 70 80

0 20 40 60 80 100 120 140 160 180% DR Time (sec) 11 

# Friction Reduction Testing (FR Loop)
% D R = ! P w a t e r 

## - ! P f r a c f l u i d 

## ! P w a t e r 

## " 1 0 0
Decrease due to shear degradation in the pump Delay due to FR hydrationcivil and environmental engineering 12 

# Friction Reducer Performance Criteria based on Friction Loop Performance

Kidder, M. SPE Workshop, Ft. Worth, TX, March 2013. Hydration Time to Sustained Drag Reduction (seconds) Sustained %DR for 3 min < 30 <45 <60 <90 > 70 Best Good Maybe Poor > 60 Good Maybe Poor Not Acceptable > 50 Maybe Poor Not Acceptable Not Acceptable > 40 Poor Not Acceptable Not Acceptable Not Acceptable > 30 Not Acceptable Not Acceptable Not Acceptable Not Acceptablecivil and environmental engineering 13 FR at 0.033% in synthetic Marcellus produced water Ferguson, M.L. and Johnson, M.A., JPT, November 2009



# Testing of Friction Reducer for Compatibility with Water Quality

FR at 0.05% in actual Marcellus produced watercivil and environmental engineering FR at 0.5 gal/1,000 gal Fresh Water System Moderate Brine System Heavy Brine System TDS (mg/L) < 10,000 < 20,000 ~ 100,000 (limit not yet defined) Total Multivalent

Cations (mg/L) < 1,000 < 5,000 ~ 15,000 (limit not yet defined) pH > 5 Temperature 1-2 min to hydrate when T < 50F 30-45 s when T < 50F (increase FR conc. to improve hydration time)
14 Kidder, M. SPE Workshop, Ft. Worth, TX, March 2013. 

# Friction Reducer Compatibility Criteriacivil and environmental engineering 

## Chemical%Criteria%for% Frac %Water%Makeup% Chemical Parameter Maximum Value, mg/L TDS 50,000 Hardness 26,000 HCO 3 300

SO 4 50

Cl 45,000 Na 36,000 Ca 8,000 Mg 1,200

K 1,000 Fe 10 Ba 10 Sr 10 Mn 10 15 Industry Contact Group Final Report, WVU (DOE Award #: DE-FE0001466), June 2012 

### Another consensus pollcivil and environmental engineering 

## Chemical%Criteria%for% Frac %Water%Makeup% Chemical Parameter Maximum Value, mg/L TDS 50,000 Hardness 26,000 HCO 3 300

SO 4 50

Cl 45,000 Na 36,000 Ca 8,000 Mg 1,200

K 1,000 Fe 10 Ba 10 Sr 10 Mn 10 16 Industry Contact Group Final Report, WVU (DOE Award #: DE-FE0001466), June 2012civil and environmental engineering 17 

# Sulfate%Concern%due%to% Downhole %PrecipitaDon%

Scaling on production Casing (+NORM?)
“Homogeneous “ scaling Formation of plugs Biological activity (SRB)??civil and environmental engineering 18 

# Sulfate%PrecipitaDon% Downhole

SO 4 %(mg/L)% BaSO 4 %volume% (m 3 )% Volume% percentage% compared%with% proppant 200! 0.98! 0.1%! 800! 4.9! 0.5%! 2000! 9.8! 1.3%! 

### Calculations performed using:

- Fracturing fluid volume = 3 million gal

- 9% w 

### proppant

- Proppant density = 1201 kg/m 3


### Negligible volume compared with the volume of proppant injectedcivil and environmental engineering 19 

# Linear Gel System

• Guar gum or its derivatives

– Hydroxy -propyl-guar (HPG)

– Carboxy -methyl- hydroxy -propyl-guar (CMHPG) 

### • Cellulose derivatives

– Hydroxy -ethyl-cellulose (HEC) 

### • Require moderate pH (6-8) to ensure proper hydration • Guar is insensitive to:

– High TDS

– Multivalent (hardness) ions 

### • Crosslinkers (aluminum, boron, titanium, zirconium) should be minimized to reduce the risk of accidental cross-linking in the event of unexpected pH increasecivil and environmental engineering 

# Guar – Borate System • Generally adaptable to a variety of water conditions • Desirable characteristics for proppant placement (early viscosity, shear recovery) • Requires high pH (8.5 to >12)

- Low temperature (8.5 to 10.0)

- High temperatures require higher pH (10.0 to >12) 

## • Limited performance above 300°F 20 

# Cross-linked Gel Systemcivil and environmental engineering 

# Metallic crossl ink system • More potential issues with challenging waters • Flexible pH (4 to 11) • Must be properly delayed (shear degrading) • Balancing delay and early crosslinking/viscosity is difficult • Existing crosslinked packages developed for fresh water • Adapting fluids to more challenging conditions 21 

# Cross-linked Gel Systemcivil and environmental engineering 22 

### Ideal Viscosity Response (High Performance Fluid)

0 200 400 600 800 1000

0:00 0:30 1:00 1:30 2:00 Time (HH:MM)Apparent Viscosity (cp) and ShearRate (1/s)

50 100 150 200 250 300Temperature (degF) Shear Rate Apparent Viscosity Fluid Temperature

High Shear Period Early Time

Viscosity (Wellbore) Thermal Stability for Pump Time 

### Ideal Viscosity Response (High Performance Fluid)

0 200 400 600 800 1000

0:00 0:30 1:00 1:30 2:00 Time (HH:MM)Apparent Viscosity (cp) and ShearRate (1/s)

50 100 150 200 250 300Temperature (degF) Shear Rate Apparent Viscosity Fluid Temperature

High Shear Period Early Time

Viscosity (Wellbore) Thermal Stability for Pump Time 

# Performance Testing

Bjornen , K. et al. SPE Workshop, Ft. Worth, TX, March 2013.civil and environmental engineering 23 Property Acceptable Range Affected TDS < 30,000 mg/L FR / Hydration Total Hardness ( Ca + Mg + Ba + Sr ) < 10,000 mg/L FR / Hydration Sulfates < 200 mg/L Scaling tendency pH 6-8 Hydration Carbonates < 200 mg/L Scaling tendency Bicarbonates < 400 mg/L Scaling tendency Reducing agents 0 ppm Hydration / Breaker Silica < 1 mg/L Crosslinking Iron < 10 mg/L Crosslinking / Hydration Phosphates < 5 mg/L Crosslinking Bacteria < 10 5 /mL Gel / Crosslinking 

# Water Quality Requirements

Chesapeake Energy Corporationcivil and environmental engineering 24 

# High%Alkalinity%Water%Challenging%for%GuarOBorate%%

0.00 0.20 0.40 0.60 0.80 1.00

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 pH!i H 3 BO 3 H 2 BO 3 - HBO 3 -2

BO3 -3

0.00 0.20 0.40 0.60 0.80 1.00

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 pHαi H 2 CO 3 HCO 3 - CO 3 -2 High pH is necessary for borates to crosslink guar gel

High pH accelerates scaling

Bjornen , K. et al. SPE Workshop, Ft. Worth, TX, March 2013.civil and environmental engineering 

### • High pH to achieve borate cross-linking drives CaCO 3 

### , and Mg(OH) 2 

### scale formation

– No blending • 3,000 – 7,000 lb solids



### – 90/10 produced water/fresh water blend • 4,900 - 9800 lb solids 

### • 250,000 lb of proppant used per stage

– 10% fines translates into 25,000 lb 

### • Impact of calcite solids and other scaling solids on proppant conductivity not well understood

– Do the these solids flow back due to small micron size?

– Do they stay downhole ? 25 

# Impact%of%Precipitates%–%Eagle%Ford%

Calcite solids
Bjornen , K. et al. SPE Workshop, Ft. Worth, TX, March 2013.civil and environmental engineering 26 Parameter Typical Standard Elevated Success Iron < 10 ppm Up to 200 ppm Magnesium < 50 ppm Up to 150 ppm Calcium < 200 ppm Up to 2,000 ppm Bicarbonate < 500 ppm No upper limit

Chlorides < 10,000 ppm No upper limit Oil < 10 ppm or no oil Oil does not interfere BUT other contaminants inside of the oil may Kidder, M. SPE Workshop, Ft. Worth, TX, March 2013. 

# Water%Quality%Criteria%%

- Frac fluid compatibility testing should be done if water quality is approaching the prescribed limits

- Impact of salt on scaling propensity in the proppant pack or production linescivil and environmental engineering 27 

# Hybrid Systems

- Lead off with a simple slickwater fluid with 100 mesh proppant

- Switch to a linear guar gel and larger proppant

- Finish with a higher proppant loading and Xlinked gel 

## Need to satisfy ALL water quality criteriacivil and environmental engineering 28 

## • Dissolved ions (chlorides and TDS)

– Generally not looking to remove; blending with fresh water is the control strategy 

## • Other dissolved constituents

• Suspended solids (turbidity and TSS)

– Can decrease biocide effectiveness

– Remove by filtration 

# Treatment/Management Selection

Constituent Above Ground In-well Hardness Softening Complexation Barium Sulfate precipitation Complexation Iron Aeration Complexationcivil and environmental engineering 

### • Produced water reuse depends on both quantity and quality • Old water quality criteria need to be revised based on specific applications and compatibility tests • New chemical formulations extend water reuse • Water compatibility with frac fluid design governs treatment requirements

– Slickwater : easy to reuse water by choosing the right friction reducer; scaling concerns may be important

– Linear Gels: as long as pH does not increase above 8, similar criteria as for slickwater

– Cross-linked Gels: Multivalent cations and crosslinker concentration in the produced water are important criteria; scaling concerns may be important 29 

# Summarycivil and environmental engineering 

# Thank!You!for!! Your!A7enKon! QuesKons?!