wastewater management for unconventional gas...
TRANSCRIPT
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
civil and environmental engineering
Flowback Quantity vs. Time
Hayes, 2009
civil and environmental engineering
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
civil and environmental engineering
Flowback Water Characterization
160 flowback water analyses (BOGM, MSC, E&P companies)
civil and environmental engineering
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
civil and environmental engineering
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
)
civil and environmental engineering
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
Chloride Concentration (g/L)
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
Chloride Concentration (g/L)
Ca
lciu
m c
on
cen
tra
tio
n (
g/L
)
civil and environmental engineering
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 (%)
civil and environmental engineering
Wastewater Management Options
• Waste disposal
- Injection/disposal wells
- Discharge to POTWs/CWTs
• Treatment for reuse or surface discharge
civil and environmental engineering
Gas Drilling Wastewater Management
11
(Hart, P., 2011)
civil and environmental engineering
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
civil and environmental engineering
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
civil and environmental engineering
civil and environmental engineering
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)
civil and environmental engineering
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
civil and environmental engineering
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)
civil and environmental engineering
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
civil and environmental engineering
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
Makeup Water(Fresh Water)
High TDS WaterFor Reuse
civil and environmental engineering
Flow scheme 4: Off-Site Primary Treatment and
Demineralization
Well 1
On-SiteSettling SS Removal
Well 2
Blend
Makeup Water(Fresh Water)
Distilled WaterFor Reuse
Near FieldPrimaryTreatment
Demineral-Ization
MechanicalVapor Recomp Disposal
(Class II Well)OrBy-ProductRecovery (Crystallizer)
ConcentratedBrine
civil and environmental engineering
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
civil and environmental engineering
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
civil and environmental engineering
Total Water Balance Within a Gas Field
23
(Kujivenhoven et al., 2011)
civil and environmental engineering
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
civil and environmental engineering
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
civil and environmental engineering
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
civil and environmental engineering
Zero Liquid Discharge
20 to 400 gpm
685 to 13570 bpd
Inlet 300,000 mg/l
Outlet Water/Salts
Crystallization
civil and environmental engineering
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
civil and environmental engineering
Gas Drilling Wastewater Management
29
(Hart, P., 2011)
civil and environmental engineering
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
civil and environmental engineering
Thank You for
Your Attention
Questions?