wastewater management for unconventional gas...

civil and environmental engineering 11

Wastewater Management for

Unconventional Gas Extraction

Radisav D. Vidic, Ph.D., P.E.

Department of Civil and Environmental Engineering

University of Pittsburgh, Pittsburgh, PA 15261

civil and environmental engineering

Wastewater Issues

Flowback water Produced water

Flowrate High Low (10-50 bbl/day)

Duration 1 – 2 weeks Life of the well

TDS < 200,000 mg/L > 300,000 mg/L

CompositionChemical additives

Naturally occuring constituents

Same as flowback +

oil and grease


Flowback Quantity vs. Time

Hayes, 2009


Flowback Water Quality evolves with Time

Regular TDS increase

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

200,000

0 5 10 15 20 25 30 35

Days after hydraulic fracturing

TD

S (

mg

/L)

Site A

Site B2

Site B1

Nearby locationsDrinking water

Partly flowback water reuse


Flowback Water Characterization

160 flowback water analyses (BOGM, MSC, E&P companies)


Flowback Water Quality

Constituent Low Medium High

Ba (mg/L) 2,300 3,310 13,500

Sr (mg/L) 1,390 2,100 8,460

Ca (mg/L) 5,140 14,100 41,000

Mg (mg/L) 438 938 2,550

Hardness (mg /L as CaCO3)

17,900 49,400 90,337

TDS (mg/L) 69,400 175,600 345,000

Gross Beta (pCi/L)

ND 43,415 597,000

Ra226 (pCi/L) ND 623 9,280

COD (mg/L) 850 12,550 36,600


Flowback Quality

y = 0.5773x

R2 = 0.9032

0

50,000

100,000

150,000

200,000

250,000

0 50,000 100,000 150,000 200,000 250,000 300,000 350,000

TDS (mg/L)

Cl c

once

ntra

tion

(m

g/L

)


Flowback Water Quality

North-East Central South-West

y = 8.4712x1.2947

R2 = 0.9291

y = 7.4939x1.2571

R2 = 0.9165

0

2,000

4,000

6,000

8,000

10,000

0 50 100 150 200

Chloride Concentration (g/L)

Str

on

tiu

m c

on

cen

tra

tio

n

(mg

/L)

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

0 50 100 150 200Chloride Concentration (g/L)

Ba

riu

m c

on

cen

tra

tio

n

(mg

/L)

y = 0.6679x0.8822

R2 = 0.8663

0

20

40

60

80

100

120

140

0 50 100 150 200 250


So

diu

m c

on

cen

tra

tio

n (

g/L

)

y = 0.0229x1.3229

R2 = 0.7658

y = 0.0571x1.185

R2 = 0.9643

0

10

20

30

40

50

0 50 100 150 200


Ca

lciu

m c

on

cen

tra

tio

n (

g/L

)


Flowback/Produced Water Quality: Ba trend

0 – 0.3

0.3 – 1.6

1.6 – 2.5

2.5 – 4.0

4.0 – 5.9

5.9 – 8.4

Ba/Cl ratio (%)


Wastewater Management Options

• Waste disposal

- Injection/disposal wells

- Discharge to POTWs/CWTs

• Treatment for reuse or surface discharge


Gas Drilling Wastewater Management

11

(Hart, P., 2011)


Disposal Wells

• Require demonstration that injected fluids remain

confined and isolated from fresh water aquifers

• Limited capacities (1200 to 3000 bpd)

• Substantial capital investment with uncertain life

span ($1M to $2M)

• Probably will only play a limited role


Disposal to Treatment Plants

(POTWs or CWTs )

• Used in the past

• POTWs use biological processes that cannot handle

high salinity

• Existing CWTs are not suitable to treat Marcellus

Shale wastewater


Oct 2010

Nov 2010

Dec2010

Jan2011

Feb2011

March2011

April2011

May2011

June2011

July2011

Aug2011

Sept2011

Oct2011

Upstream of Plant B 29 79 61 36 27 17 32 66 93 63 26 25Donwstream of Plant B 20 X 10 X 9 X 10 X 1.1 X 3 X 3 X 8 X 8 X 27 X 34 X 4 X 17X

Blue Spruce Bridge 57 39 64 87 37 38 13 53 83 116 114 56 25

Bridge St. Bridge 1130 345 639 774 42 111 44 414 640 3100 3900 214 427

Stitt Hill Rd. Bridge 280 467 396 173 74 53 112 258 578 582 426 103

CROOKED CREEK & McKEE RUNBromide Concentration (ppb)

Sample Site

Crooked Creek

McKee Run

(Casson, L., 2012)


Treatment for Reuse in Fracking

Operations

• Reduce O&G industry needs for surface water

• Reduce overall management costs

– Volume reduction

– Transportation costs

– Disposal costs

• Reduce potential liability


Flow scheme 1: Conventional Water Management

Well 1

Class II WellDisposal

“Fresh”Water

Flowback

� Represents Maximum Water Demand

(No Water Reuse)

� Conventional approach in Barnett and other plays

� Difficult in Marcellus (only 7 Class II wells)


Flow scheme 2: On-Site Primary Treatment for Reuse

Well 1

Well 2

Blend

Makeup Water(Fresh Water)

On-SiteSettling

SS & FR Removal

High TDSReuse Water


Flow scheme 3: Off-Site Primary Treatment for

Reuse

Well 1

Rapid Mixw/ chemicals

Sedimenta-tion & Hard-ness Rem

Rapid SandFilter

Belt PressDisinfect

Solids to Landfill

On-SiteSettling SS Removal

Near-Field Primary Treatment

Well 2

Blend


High TDS WaterFor Reuse


Flow scheme 4: Off-Site Primary Treatment and

Demineralization

Well 1

On-SiteSettling SS Removal

Well 2

Blend


Distilled WaterFor Reuse

Near FieldPrimaryTreatment

Demineral-Ization

MechanicalVapor Recomp Disposal

(Class II Well)OrBy-ProductRecovery (Crystallizer)

ConcentratedBrine


Flow Scheme FS 1 FS 2 FS 3 FS4

Method Transport to Class II Well for Disposal

“In Field” Primary Treatment for Reuse

“Near Field” Precipitation

for Reuse

“In-Field” Evaporation

for Reuse

Treatment $ - 71 83 119

Transport $ 75 1 24 24

Brine Disposal $ 60 - - 19

Sludge Disposal $ - 2 6 6

Total Cost ($x1000) 135 74 113 168

Cost per barrel 5.67 3.10 4.75 7.05

Hardness Removal 100% 0% 97% 100%

Ba removal 100% 0% 99% 100%

Salt Removal 100% 0% 0% 100%

Water reused 0 99% 97% 90%

Basis: 1 million gallons of flowback (23,800 barrels)

Economic Comparison of Flow Schemes


Recycling/Reuse

- Works for 12-15 yrs

- Eventually net water production in a filed

• 4800 wells on 625 mi2

• 3 refractures/well

• 33% water reuse


Total Water Balance Within a Gas Field

23

(Kujivenhoven et al., 2011)


Treatment Options

Total Dissolved Solids (mg/L)

Wat

er R

eco

very

(%

)

50

100

75

25,000 50,000 100,000 300,000

Limited recoveryat high TDS

Evaporation

Crystallizers


Thermal Treatment

• Only alternative if there is a need to produce

water suitable for disposal

• Suitable for remote locations without

infrastructure or for centralized treatment

plants

• Can be followed by a crystallizer for enhanced

water recovery and salt production


WATER SOURCE

FRACOPERATIONS

WASTE BRINE

STORAGE

FLOWBACK

PRODUCED WATER

ROAD DEICING

SALT

PURGE TO DISPOSAL

BRINE CRYSTALLIZER

BRINE CONCENTRATORVolume

ReductionBased on

TDS

RECOVERED WATER Pretreatment

95% Volume Reduction

Complete Treatment Process


Zero Liquid Discharge

20 to 400 gpm

685 to 13570 bpd

Inlet 300,000 mg/l

Outlet Water/Salts

Crystallization


Salt production

• 100,000 wells

• 10 barrels/day/well of produced water

• 300,000 mg/L salinity of produced water

• 80% salt recovery

• Total NaCl produced in PA = 8 million tons

• Total salt use for deicing in the US = 12-15 million tons


Gas Drilling Wastewater Management

29

(Hart, P., 2011)


Summary and Conclusions

• No viable disposal options for gas drilling wastewater

in PA and very few treatment options for disposal

• Flowback water reuse appears to be the most

effective option

• Water reuse has a finite shelf life

• Need to develop technologies that would enable

final disposal of wastewater

• Salt management will become a major issue in PA


Thank You for

Your Attention

Questions?

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