Liz Chapman, PhD, Geochemist ECHELON Applied Geosciences. Copyright 2014 EchelonAGC

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1 Liz Chapman, PhD, Geochemist ECHELON Applied Geosciences 1

2 For a variety of fluids (fresh water, brines, AMD-impacted and coproduced waters) And many geologic rock types and materials Coal, shale, permeable limestone and sandstone aquifers Deep and shallow units Cements/grouts/combustion byproducts (coal fly ash) Must be able to identify contaminant source as well as provide ongoing monitoring Introduced tracers Major and trace element geochemical signatures Natural isotopic signatures

3 Four naturally-occurring stable isotopes, including 87 Sr and 86 Sr 87 Sr is supplemented by the slow decay of 87 Rb ( radiogenic isotope ) Half-life: 48.8 Ga 87 Sr/ 86 Sr increases with time Capo et al., 1998

Rocks with different compositions and geological histories develop distinct 87 Sr/ 86 Sr ratios Reflect sources of Sr available during formation

4 Rocks with different compositions and geological histories develop distinct 87 Sr/ 86 Sr ratios Reflect sources of Sr available during formation Waters which interact with these units can inherit their 87 Sr/ 86 Sr 87 Sr/ 86 Sr in geologic materials is an indicator of both age and geochemical origin

5 (RIVERS) Sr/ 86 Sr Millions of Years

6 ε SW =10 4 Sr 87 Sr/ 86 Sr sample 87 Sr/ 86 1 Sr seawater

7 Ubiquitous and abundant One of the most abundant trace elements in crustal rocks Systematics understood Proxy for calcium Sr substitutes for Ca in feldspars, carbonates, sulfate minerals

8 Does not fractionate appreciably during physical, chemical, or biological processes (e.g. evaporation, mineral dissolution/precipitation, oxidation, sorption, plant/animal uptake) Isotopic composition not affected by dilution or mixing

9 ~2 µg (10-6 g) Sr Minimum amount of sample to process: Carbonate: < 10 mg Shale: mg Groundwater: 0.5 1L Produced water: <500 ml AMD: <500 ml Brines: <500 ml Capo et al., 1998

Can be diagnostic of specific environmental reservoirs, both natural and anthropogenic Allows for sensitive quantification of source inputs,

10 Can be diagnostic of specific environmental reservoirs, both natural and anthropogenic Allows for sensitive quantification of source inputs, especially if source 87 Sr/ 86 Sr are very different Quantifies amount of mixing Can be used to understand processes along migration pathways

11 To use Sr isotopes as a tracer, you must have: The isotopic composition of all sources of Sr to the system The extent of isotopic variation within individual sources

Since some samples might have very low Sr concentrations, it is important to have very clean sample bottles for collection HDPE bottles (Nalgene) Acid-washed (ex. p. 22-27, http://water.usgs.

12 Since some samples might have very low Sr concentrations, it is important to have very clean sample bottles for collection HDPE bottles (Nalgene) Acid-washed (ex. p , chapter3/final508chap3book.pdf) Samples for Sr isotope analysis should not be acidified in the field unless ultrapure acids are available When possible, separate aliquots should be taken for major/trace element concentrations, and Sr isotopes

13 Solid samples (cores, well cuttings, ash, soil, rocks) must be pulverized and leached to release Sr Simulate fluids that may be interacting with the rock

14 Sr concentrations must be accurately measured before processing for Sr isotopes Sr separation performed in Class 100 clean lab

15 Rapid Sr separation (5x faster than traditional methods) Vacuum-assisted Disposable columns Isotope measurement by multicollector ICP-MS (4-5 samples/hr) Typical measurement uncertainty: 0.002% See Wall et al., 2013

16 Marcellus produced waters Four Pennsylvania counties Bradford Westmoreland Washington Greene Different sample types: Individual well single samples Impoundment samples Produced water time series Chapman et al., 2012; Kolesar et al., 2013; Capo et al., 2014

17 16 87 Sr/ 86 Sr n Washington Co. Greene Co. Bradford Co. Westmoreland Co Chapman et al., 2012 ε SW Sr

18 Capo et al., 2014

19 Combination of ε Sr and Sr/Ca likely to distinguish between sources in nearly all cases Even small amounts (<0.1%) of Marcellus produced waters can significantly shift stream ε Sr Sr/Ca Chapman et al., 2012 ε SW Sr Bradford Co. PW Westmoreland Co. PW Greene Co. PW Washington Co. PW Pittsburgh Coal AMD Stream water to Venango brine (0.015, +111)

20 87 Sr/ 86 Sr of Marcellus produced waters allow for extremely sensitive tracking Potential applications: Verification of safe water disposal Determination of origin of dissolved constituents in surface and ground waters affected by multiple sources Quantification of mixing

21 Produced water reflects: Original composition of injection water Mobilized constituents from shale Formation waters liberated by fracing Sr measured in flowback up to 27 months post-frac Capo et al., 2014

22 Strontium concentrations plateau within the first year of flowback Capo et al., 2014

23 ε Sr continue to increase even after 2 years Greene A Greene B Greene C Capo et al., 2014

24 Linear correlations indicate the increase in ε Sr is due to mixing of two endmembers Capo et al., 2014

25 Higher- ε Sr endmember most likely pore/formation water rather than soluble salts Produced water Leachates Stewart et al., in press 25

26 Sr isotopes show a change over time from frac fluid + formation water primarily formation water Mixing models combined with leachate geochemistry suggest that dissolved salts in produced water originate in formation water rather than as soluble salts within the shale

27 Greene County site with: Six Marcellus laterals One vertical Marcellus well Four Upper Devonian (UD) gas wells One shallow groundwater spring Sr measured before and after hydraulic fracturing of laterals Kolesar Kohl et al., 2014

$Most UD wells show no change after fracturing (p values >0.$

29 Most UD wells show no change after fracturing (p values >0.05) For isotopic shifts to be considered significant enough to suggest Marcellus fluid incursion, ε Sr would need to decrease by 1-3 units Kolesar Kohl et al., 2014

30 Sr isotope values fall between Marcellus and Upper Devonian values Values shift on a semiannual basis (±0.8 from the mean) Spring water contains very little Sr Very sensitive to any potential mixing with produced water Kolesar Kohl et al., 2014

31 The only well in the study that showed a significant change in Sr isotope values after horizontal wells were fractured (from to +35.9) Sr concentration also increased by ~200 mg/l New pathways within the Marcellus were opened up by fracturing Kolesar Kohl et al., 2014

32 Calculated mixing models between produced waters and spring water Most sensitive elements: Ba, Br, Cl, Sr Elemental ratios (Sr/Ca, Br/Cl) less sensitive than absolute concentrations Kolesar Kohl et al., 2014

33 Greater sensitivity than elemental conc., especially in waters with natural seasonal variation Unlike elemental concentration, Sr isotopes can distinguish between UD and Marcellus produced waters Kolesar Kohl et al., 2014

34 Subsequent to hydraulic fracturing, no significant migration of Marcellus-derived fluids was observed in Upper Devonian or shallow groundwater units Shift in Sr isotopes of vertical Marcellus well suggests fracturing opened new flowpaths within the unit Sr isotopes show greater sensitivity to potential brine migration than elemental concentrations or ratios

35 History of fossil fuel activities: Oil and gas extraction since mid-1800 s, Upper Devonian sands (Bradford, Venango) Hilltop strip mines (Clarion, Brookville coals) Chapman et al., 2013

36 Unplugged wells Artesian flow (>20 gpm) High total dissolved solids (TDS) Sulfate-dominated >100 mg/l iron

37 Gas well discharges: High sulfate, iron Low sodium, chloride AMD: High sulfate Low iron Oil and gas brines: High sodium High chloride

38 Siderite nodules (FeCO 3 ) Coal overburden Siderite cement Shallow sandstone drinking water aquifers

39 1-3: Gas well discharges 4-7: AMD 8: Unaffected aquifer water 9-10: Venango oil and gas brines 11-13: Siderite nodules 14-16: Siderite cement Chapman et al., 2013

40 Chapman et al., 2013

41 Unaffected aquifer Venango brines AMD Gas well discharges ε SW Sr Siderite cement Sr/ 86 Sr Siderite nodules

42 Siderite cement Sr/ 86 Sr Chapman et al., 2013

43 Supported by saturation indices generated by PHREEQc modelling software Chapman et al., 2013

44 Variety of sample types are often necessary to understand subsurface processes Strontium isotopes able to: Differentiate between coal- and oil/gas-related inputs Distinguish mineralogically identical but genetically different sources

45 Inactive coal mine partially filled by injection of grout to mitigate AMD 98% coal utilization byproducts (CUB) 2% Portland cement Mine sealing unsuccessful AMD still leaking 3 years later Major/trace element chemistry not sufficient to distinguish between discharges which interacted with grout and those that did not Hamel et al.,

46 Eight sites sampled over a period of 2 years Hamel et al.,

47 Hamel et al.,

48 Sr isotopes show that discharges received 30-40% of their total Sr from grout material Grout is chemically eroding at a rate of approx. 0.04% (3 x 10 4 kg) per year Hamel et al.,

49 Sr isotopes able to distinguish waters interacting with grout material vs waters with no interaction Major/trace element chemistry unable to differentiate Sr isotopes used to calculate rate of grout dissolution Hamel et al.,

50 Capo, R.C., Stewart, B.W., Rowan, E., Kolesar, C., Wall, A.J., Chapman, E.C., Hammack, R.W., and Schroeder, K.T., The strontium isotopic evolution of Marcellus Formation produced waters, southwestern Pennsylvania. International Journal of Coal Geology, available online 28 Dec Capo, R.C., Stewart, B.W., and Chadwick, O.A., Strontium isotopes as tracers of ecosystem processes: theory and methods. Geoderma, v. 82, p Chapman, E.C., Capo, R.C., Stewart, B.W., Hedin, R.S., Weaver, T.J., and Edenborn, H.M., Strontium isotope quantification of siderite, brine and acid mine drainage contributions to abandoned gas well discharges in the Appalachian Pleateau. Applied Geochemistry, v. 31, p Chapman, E.C., Capo, R.C., Stewart, B.W., Kirby, C.S., Hammack, R.W., Schroeder, K.T., and Edenborn, H.M., Geochemical and strontium isotope characterization of produced waters from Marcellus Shale natural gas extraction. Environmental Science & Technology, v. 46, p Chapman E.C., Capo, R.C., Stewart, B.W., Johnson, J.D., Graney, J.R., Hammack, R.W., Geochemical and strontium isotope study of sequentially extracted metals from Marcellus Shale drill core. Geol. Soc. Am. Abstr. Prog., #

51 Hamel, B.L., Stewart, B.W., Kim, A.G., Tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine: Strontium isotope study of the inactive Omega Coal Mine, West Virginia (USA). Applied Geochemistry, v. 25, p Kolesar Kohl, C.A., Capo, R.C., Stewart, B.W., Wall, A.J., Schroeder, K.T., Hammack, R.W., and Guthrie, G.D., Strontium isotopes test long-term zonal isolation of injected and Marcellus Formation water after hydraulic fracturing. Environmental Science & Technology, v. 48, p Kolesar, C.A., Capo R.C., Wall, A.J., Stewart, B.W., Schroeder, K.T., Hammack, R.W., Using strontium isotopes to test stratigraphic isolation of injected and formation waters during hydraulic fracturing, AAPG Search and Discovery Article # Stewart, B.W., Chapman, E.C., Capo, R.C., Johnson, J., Graney, J.R., Kirby, C.S., and Schroeder, K.T., in press. Origin of brines, salts and carbonate from shales of the Marcellus Formation: Geochemical and Sr isotope study of sequentially extracted fluids, Applied Geochemistry. 51

52 University of Pittsburgh: Rosemary Capo, Brian Stewart, Courtney Kohl, Andrew Wall, James Gardiner Department of Energy: Karl Schoeder, Rick Hammack, Hank Edenborn Hedin Environmental: Bob Hedin, Ted Weaver 52

Fate of Radium in Marcellus Shale Flowback Water

Fate of Radium in Marcellus Shale Flowback Water Tieyuan Zhang 1, Daniel Bain 2, Radisav Vidic 1 Civil & Environmental Engineering 1, Geology & Planetary Science 2, University of Pittsburgh Project funding: