Hydraulic fracturing (or fracking) is a well stimulation technique for unconventional oil and gas extraction. Approximately, a volume of 8-38 million cubic meters per day of fracking fluids containing water, chemicals, and proppant is injected into shale formations in the U.S. During production, in conjunction with the gas, a hypersaline brine (i.e., flowback and produced water) containing heavy metals and radionuclides, such as barium (Ba2+), strontium (Sr2+), and radium (Ra2+), is extracted. Spills of flowback and produced water into the subsurface may occur during operation, handling, and storage with potential negative impact on shallow potable aquifers. However, it is not well understood the fate of the hazardous elements within the brines upon a leakage into a reactive porous medium of various mineralogy. Previous work in our group showed that the transport of Ba2+ (congener of Ra2+) through a goethite-coated porous medium is significantly affected by pH and salinity becoming negligible its retardation at the produced water conditions. Here, we present an experimental work to describe the transport of the major cations i.e., Ba2+, Ca2+, Mg2+, Sr2+, Ra2+, and Co (Cobalt) in the produced water. We selected porous media containing either sand, goethite-coated sand, or alumina (as an analog for clay) because ubiquitous in aquifers. Column-flood experiments were performed with both natural and synthetic produced water. Preliminary results show that under the conditions of a spill all cations move with negligible retardation in all cases suggesting that in a case of a spill of produced water within an aquifer a fast migration of the major metals and radionuclides may occur with a potential negative impact on aquifer water quality.

Transport of heavy metals and radionuclides in produced water through porous media

256th National Meeting (2018)

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