Use of Abandoned Mine Drainage for Hydraulic Fracturing

Use of Abandoned Mine Drainage for Hydraulic Fracturing in Marcellus Shale Radisav D. Vidic Department of Civil and Environmental Engineering University of Pittsburgh, PA 15261 civil and environmental engineering

Why AMD? Well permits AMD Reclaimed 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 engineering

Co-treatment of Flowback Water and AMD Flowback water Abandoned mine drainage (AMD) Barium, Strontium, Calcium Sulfate Hydraulic fracturing 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 engineering 3

AMD and Flowback Water Chemistry Flowback AMD Site A Site B Site C Site D p. H 5. 7 7. 03 6. 14 7. 56 Alkalinity 62 394 40. 5 SO 4 696 242. 5 Fe 27 - TDS FB 1 FB 2 Cl 104, 300 29, 000 47. 5 Na 38, 370 11, 860 709 328 Ca 15, 021 2, 224 0 32. 1 0 Mg 1, 720 249 1574 1328 1127 Sr 1, 800 367 Ba 236 781 AMD from sites a and B are available in the vicinity of FB 1 while C and D are found close to FB 2 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 4

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 engineering

Predicted sulfate concentration (mg/L) 600 500 Predicting the Finished Water Quality 400 300 200 100 0 0 200 400 600 Measured sulfate concentration (mg/L) Crystal Characteristics • TCLP tests revealed no leaching of Ba or Sr • Sludge generated in this process is non-hazardous SO 4 ≈ 250 mg/L SO 4 ≈ 600 mg/L Ba = 35 mg/L Sr = 270 mg/L I ≈ 0. 5 M Ba 0. 78 Sr 0. 22 SO 4 Ba 0. 68 Sr 0. 32 SO 4 Ba = 75. 9 mg/L Sr = 36 mg/L I ≈ 0. 1 M Ba 0. 9 Sr 0. 1 SO 4 Ba 0. 84 Sr 0. 16 SO 4 civil and environmental engineering 6

Optimizing Coagulation/Flocculation Process Optimum coagulant dose: 20 mg/L Optimum p. H: 6. 0 Slow mixing time: 30 min Settling time: 30 min civil and environmental engineering 7

Sulfate Removal is Governed by the Ba 2+/SO 42 - ratio Very low turbidity of the finished water civil and environmental engineering 8

Process Design for 1 MGD Plant Q = 0. 4 MGD Co = 1, 000 ppm Q = 1. 15 MGD C = 9, 625 ppm Q = 1 MGD C < 5 ppm Q = 0. 15 MGD C = 70, 000 ppm Q = 0. 6 MGD Co = 1, 000 ppm • • 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) civil and environmental engineering