Potential Sources of Salts from Water-Rock Interaction during Hydraulic Fracturing: An Experimental Study
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Date
2016-03-30
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Abstract
An on-going environmental issue from hydraulic fracturing of gas shale plays is the elevated salt content of flowback fluids. Studying this problem is important as the cost and method of disposal of the hydraulic fracturing fluids is dependent on their volume and composition. This study focuses on determining the potential source of salts to flowback fluids from a series of sequential water-rock interaction leach experiments on core samples from the Point Pleasant Formation (carbonate-rich (XRD)) and cuttings samples from the Utica Formation (clay-rich (XRD)). The objective is to determine how cation and anion concentrations evolve in solution. Rock and fluid samples from this study were analyzed by X-Ray diffraction (XRD) for determining bulk mineralogy, scanning electron microscopy (SEM) for mineral-textural and elemental data, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) for select major and trace elements, Ion Chromatography (IC) for anion concentrations, and the use of PHREEQC Geochemical Modeling for saturation indices. These experiments show that the total solute released from the solid phase was greater in 1mM HCl than in water; although, the rapid change in pH after ~1 day suggests neutralization by carbonate dissolution. Results where concentrations were much higher than expected are the result of the accidental addition of excess HCl. Overall, the leachates of the cuttings show much higher solute concentrations than core using both water and dilute acid. The release of the cations sodium, potassium, strontium and barium and the anions sulfate and chloride into solution all affect salt concentrations. The results of this study are important because they contribute to the understanding of results and support results from other studies of salt origin and increased salinity in flowback fluids such as Blauch (2009), Stewart (2015) and Wilke (2015).
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Mathematical and Physical Sciences (The Ohio State University Denman Undergraduate Research Forum)
Keywords
hydraulic fracturing, flowback waters, Point Pleasant Formation, Utica Formation, sequential leach experiments