Estimating Radium Activity in Shale Gas Produced Brine

Area of Science:

• Environmental Science
• Geochemistry
• Nuclear Science

Background:

• Shale gas brines often contain naturally occurring radioactive material (NORM), primarily radium-226 and radium-228.
• Radium mobilization from shale into produced brines is influenced by shale properties like cation exchange capacity (CEC) and brine salinity (total dissolved solids - TDS).

Purpose of the Study:

• To investigate the relationship between shale characteristics, brine salinity, and radium activity in produced brines.
• To develop a predictive model for radium activity in shale gas wastewaters.

Main Methods:

• Evaluated uranium (U) content and CEC of shale samples from Antrim, Utica-Collingwood, and Marcellus formations.
• Analyzed produced brine from Antrim shale gas wells to correlate Ra-226 activity with TDS and shale U content.

Main Results:

• Developed an empirical correlation between Ra-226 activity and produced water TDS for a given shale U content.
• Demonstrated that U content and TDS are key factors controlling radium variability in produced brines.

Conclusions:

• The established correlation allows for a priori estimation of expected Ra-226 activity in produced brines.
• This predictive capability can guide optimal wastewater treatment and disposal strategies for shale gas operations, mitigating risks associated with NORM.