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civil and environmental engineering
Use of Abandoned Mine Drainage for Hydraulic Fracturing in Marcellus
ShaleRadisav D. Vidic
Department of Civil and Environmental EngineeringUniversity of Pittsburgh, Pittsburgh, PA 15261
civil and environmental engineering
Why AMD?
Well permitsAMDReclaimed AMD
• Proximity of AMD to Marcellus wells• Significantly lower transportation costs (reduce truck traffic)• Environmental benefit (if every Marcellus well is fracked with
AMD, discharge to PA rivers could be reduced by about 30%)
civil and environmental engineering3
Hydraulic fracturing
Abandoned mine drainage (AMD)
Abandoned mine drainage (AMD)Flowback waterFlowback water
Co-treatment of Flowback Water and AMD
Barium, Strontium, Calcium Sulfate
Enables the reuse of flowback water for hydraulic fracturing with limited treatment => decreases the treatment and transport cost of flowback water
Finished water should meet industry limit of 100-200 ppm of sulfate
civil and environmental engineering4
AMD and Flowback Water Chemistry
Site A Site B Site C Site D
pH 5.7 7.03 6.14 7.56
Alkalinity 62 394 40.5 47.5
SO4 696 242.5 709 328
Fe 27 0 32.1 0
TDS - 1574 1328 1127
FB 1 FB 2
Cl 104,300 29,000
Na 38,370 11,860
Ca 15,021 2,224
Mg 1,720 249
Sr 1,800 367
Ba 236 781
AMD Flowback
AMD from sites a and B are available in the vicinity of FB1 while C and D are found close to FB2
Selected actual AMD that are available in the vicinity of well sites in Washington and Westmoreland Counties in Southwest Pennsylvania for experiments aimed at understanding relevant chemical reactions, kinetics and solids generation to enable the design of realistic treatment process.
civil and environmental engineering
Adjusting the Mixing Ratio to Achieve Desired Effluent Sulfate Limit
Depending on the initial quality of flowback and AMD, adjustment of the mixing ratio is needed to achieve desired finished water quality in terms of sulfate concentration (100-200 ppm) to allow unrestricted use for fracking
civil and environmental engineering6
Crystal Characteristics
SO4 ≈ 250 mg/L SO4 ≈ 600 mg/L
Ba = 35 mg/LSr = 270 mg/L
I ≈ 0.5 M
Ba0.78Sr0.22SO4 Ba0.68Sr0.32SO4
Ba = 75.9 mg/LSr = 36 mg/L
I ≈ 0.1 M
Ba0.9Sr0.1SO4 Ba0.84Sr0.16SO4
2
1
2
1
0 100 200 300 400 500 6000
100
200
300
400
500
600
f(x) = 1.00534368983659 x − 15.757626951492f(x) = 1.02074051999766 x − 11.6420231627783
Measured sulfate concentration (mg/L)
Pre
dic
ted
su
lfa
te c
on
ce
ntr
ati
on
(m
g/L
) Predicting the Finished Water
Quality
• TCLP tests revealed no leaching of Ba or Sr
• Sludge generated in this process is non-hazardous
civil and environmental engineering7
Optimizing Coagulation/Flocculation Process
Optimum coagulant dose: 20 mg/LOptimum pH: 6.0 Slow mixing time: 30 minSettling time: 30 min
civil and environmental engineering8
Sulfate Removal is Governed by the Ba2+/SO42- ratio
Very low turbidity of the finished water
civil and environmental engineering
Process Design for 1 MGD Plant
• Simple, conventional process with sludge recycle• Sludge passes TCLP test for Ba, Sr and Ra• Capital cost for 1 MGD plant: $1.5 million • Cost of treatment estimated at $1.5/1,000 gal ($0.063/bbl)
Q = 0.4 MGDCo = 1,000 ppm
Q = 0.15 MGDC = 70,000 ppm
Q = 0.6 MGDCo = 1,000 ppm
Q = 1.15 MGDC = 9,625 ppm
Q = 1 MGDC < 5 ppm