Fate of Radium in Marcellus Shale Flowback Water

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Vanessa Boone
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1 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: US Department of Energy, National Energy Technology Laboratory

Bi-214 would have significant γ emissions; Ra-226 in FB water ranges from 100s to 1,000s

2 Ra-226 issues in FB water Ra-226 is a stable isotope due to its very long half-life (1620 years); Even though Ra-226 is not a significant γ-emitter, its progeny Pb-214 and Bi-214 would have significant γ emissions; Ra-226 in FB water ranges from 100s to 1,000s pci/l; EPA limits for Ra-226 in drinking water is 5 pci/l; limits for discharge is 50 pci/g.

3 Radium content in FB water in PA 18,045 pci/l Citation: NY Times February 26,2011. Toxic Contamination From Natural Gas wells

4 Radium in Flowback Water USGS, 2011.

5 Ra 228 /Ra 226 in FB water 800 Low Ra-228/Ra-226è Low Th/U ratio of the reservoir lithologies. Ra228 (pci/l) y = x R² = Ra228: Ra226 Uranium isotope conc. in FB water are very low, and often show as 0 pci/l Ra226 (pci/l) Ra-228 / Ra-226 in flowback waters in PA Uranium and thorium, unlike Radium, are poorly soluble in reducing conditions, and likely to be more concentrated in mineral phases or organic matter than solution.

6 Origin of Radium in FB water Radium Origin Decay Equations: Dissolution of Shale Formation water in interspace of shale Natural Decay Series: Thorium-232 Thorium billion y Radium years 6 hours Actinium-228 Actinium y Radium d A Th-232 =! Th-232! N Th-232 dn Ra-228 dt = -! Ra-228! N Ra A Th-232 dn Ac-228 dt = -! Ac-228! N Ac-228 +! Ra-228! N Ra-228 Radon s Polonium s dn Pb-212 dt = -! Pb-212! N Pb-212 +! Ac-228! N Ac-228 A Pb-212 =! Pb-212! N Pb-212 Lead-212

7 Origin of Radium in FB water -Implication of Th 232 decay chain Initial state: There is 10,000 pci of Th-232 and activities of its progenies are 0 pci It takes ~30 years to reach equilibrium between Pb-212 and Ra Ac>vity (pci) Th232 Ra228 Ac228 Pb Time (years) Activity of Th-232 Progeny by Natural decay Radioac>ve ra>o Ac228/Ra228 Pb212/Ra Time (years) Activity ratio of Ac-228 and Pb-212 to Ra-228

8 Origin of Radium in Flowback water Ra-228 Pb-212 Ra228/ Pb212 Ac>vity (pci/l) Ra- 228 Pb- 212 Ra228 : Pb Ra228: Pb212 Ra>o Equilibrium has been achieved in Flowback water Ra-228 has been present in liquid phase for more than 30 years Sample Number Ra-228 vs. Pb-212 in different FB water *BOGM data 0 Ra originates from the formation brine

detection time. ICP-MS: Detection limit: 0.

9 Ra-226 Detection method -spectrometry: Detection limit:1pci Challenge: Very long detection time (~24h per sample) Accuracy depends on detection time. ICP-MS: Detection limit: 0.1ppt=100pCi/L Ra-226 Challenge: TDS limitation; Polyatomic effect. Gamma Spectrometer (Left) and ICP-MS (Right)

10 Radium preconcentration & Extraction for ICP-MS measurement Radium recovery from real flowback water Gammaspec ICP-MS Ra-226 (pci/l) Ra-226 (pci/l) Flowback A Flowback A with Ra-226 spike Flowback B Flowback B with Ra-226 spike RSD Recovery 81.7% 77.7% 81.2% 89.6%

11 Fate of Ra- 226 during FB treatment Regional and mobile treatment faciliges use sulfate and carbonate precipitagon to adjust the chemistry of flowback water for reuse in hydraulic fracturing. Ligand (Sulfate, Carbonate) Ra 2+ + Ba 2+ + Sr 2+ + Ca 2+ Lab-Scale studies of Co-precipitation experiment

Ra removal by Co- Precipita>on K sp,raso4 = 10-10.

12 Ra removal by Co- Precipita>on K sp,raso4 = , If [SO 4 2- ]=6 mmol/l è [Ra 2+ ] > pci/l Since the [Ra 2+ ] < 2x10 4 pci/l, Ra would not directly precipitate with sulfate. Ra 2+ + BaSO4 = Ba 2+ + RaSO4 Precipitation Lattice Replacement K d = [RaSO 4 ][M 2+ ] [MSO 4 ][Ra 2+ ]

13 Co- precipita>on of Ra- BaSO 4 / SrSO 4 Theoretical Distribution coefficient of Ra- Carriers Ra-BaSO 4 Ra-SrSO 4 Theoretical K d K d = [RaSO 4 ][M 2+ ] [MSO 4 ][Ra 2+ ] Correlation between Carrier (Ba 2+ /Sr 2+ ) and Ra 2+ removal by Co-precipitation

14 Impact of Ionic Strength on Co- precipita>on Ra-BaSO4 Co-precipitation Composi>on: Ba 2+ 6mmol/L; SO 4 6mmol/L Ra-SrSO4 Co-precipitation Composi>on: Sr 2+ 5mmol/L; SO 4 5mmol/L 100% 100% 80% 80% Ra removal 60% 40% I=3 I=0 Ra removal 60% 40% I=3 I=0 20% 20% 0% Time (h) 0% Time (h) Barite formation has a much faster kinetics than Strontium. In real FB water co-precipitation, Barite is likely the main sink for Ra 2+. Molar volume of minerals Formula V 0 (cm 3 /mol) RaSO Barite- BaSO Celestite- SrSO civil and environmental 14 engineering

15 Barite is the main sink for Ra 2+ Desorption of Ra 2+ from Co-precipitate at ph=0.8 Solid (Prepared by Radium Co- precipita>on) Ba 2+ dissolu>on Sr 2+ dissolu>on Radium released % Ra- BaSO 4 3% / 3.60% Ra- SrSO 4 / 36% 69.10% Ra- SrSO 4 + BaSO 4 3% 34% 4.31% During solid preparation, Ba 2+ /Sr 2+ : SO 4 2- =1. Ionic strength was not adjusted. Faster kinetics of BaSO 4 formation BaSO 4 is the main sink for Ra 2+

16 Radioactive solid waste handling Radium concentration (pci/l) in solid Material type Radium-226 (pci/g) Shale Cutting 2.1±1.2 Impoundment Sludge 70 ~90 Co-precipitation of Ra-BaSO ~ 5000 Disposal Costs (excluding transportation) Disposal Option RCRA-D Nonhazardous Landfill Low-Level Radioactive Waste (LLRW) UIC (Deep well injection) Maximum Ra226 pci/g Naturally Occurring Radioactive Materials, such as drill cuttings, can be disposed in landfills. Sludge in impoundment can be disposed by mixing with other waste to satisfy total landfill limits. Deep well injection seems to be the cheapest option for waste handling, but sites are limited. Disposal Cost: $/ short ton 25 (in PA) 50 10,000 6,

$Ra-226 in FB water originates from the mixing of frac fluid with formation water; Co-precipitation with$ BaSO 4 is a good treatment option for Ra removal.

BaSO 4 is a good treatment option for Ra removal.

17 Summary Radium-226 is the main component and good indicator of NORM in Marcellus shale flowback water; Ra-226 in FB water originates from the mixing of frac fluid with formation water; Co-precipitation with BaSO 4 is a good treatment option for Ra removal. Radium removal is proportional to Ba 2+ removal in synthetic FB water. Co-precipitation potentially creates low level radioactive waste that needs to be disposed properly

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