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)

Flowback 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)

Pred

icte

d su

lfate

con

cent

ratio

n (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