MINERALOGICAL AND GEOCHEMICAL ANALYSIS OF STRONTIUM AND BARIUM SOURCES IN THE POINT PLEASANT FORMATION Senior Research Thesis Submitted in partial fulfillment of the requirements for graduation With Research Distinction in Earth Sciences in the undergraduate colleges of The Ohio State University By Matthew Gordon Edgin The Ohio State University 2016 T ABLE OF C ONTENTS Abstract…………………………………………………………………………….ii Acknowledgements………………………………………………………………...iii List of Figures……………………………………………………………………...iv List of Tables……………………………………………………………………......v Introduction………………………………………………………………………..1 Geologic Setting………………………….………………………………………...3 Methods Leica DMS 1000 Microscope……………………...…….…………………..4 FEI Quanta 250 FEG SEM………………………….……………………...4 ICP-MS-LA……...…………..……………..……………………………….5 Data interpretation………....……………………...………………………...5 Results Leica images prior to SEM and ICP-MS-LA…..………….………………….8 SEM and EDXS………………………………………………………..…...9 Barite Estimation Calculation……………………………………...13 Induced Coupled Plasma Mass Spectrometry………………...……………14 Carbonate Shell Site A……………………………………………..15 Carbonate Shell Edge Site A……………………………………….18 Short Axis Carbonate Shell Site C………………………………….20 Bowtie Carbonate Short Axis Site D……………………………….23 Molar Sr/Ca vs Mg/Ca……………………………………………25 Discussion Barium……. …………………….………………………………………..27 Barium Mobilization……....……………………………………………….27 Strontium…………………………………………………………………28 Carbonate Crystal Structure Effects on Strontium Accommodation…...........29 Magnesium’s Influence on Strontium Incorporation into Calcite…………..30 Conclusions……………………………………………………………………….32 Recommendations for Future Work…………………………………………….…33 References Cited….……….…………………………………………………….....34 Appendices.………………….…………………………………………………....36 i A BSTRACT Analysis of trace elements in rocks from the Utica-Point Pleasant gas shale play is important because elevated concentrations of trace elements in flowback fluids derived from hydraulic fracturing may be an environmental hazard. Previous reports show high levels of barium and strontium associated with flowback fluids, with no clear explanation as to their origin. The goal of this study is to determine potential sources of Sr and Ba from Utica-Point Pleasant mudrocks that could be released into hydraulic fracturing fluids with which they interact. Polished sections of core were analyzed to determine the concentrations and distribution of trace elements across selected mineralogical/textural regions of the samples. Samples provided by Chesapeake Energy were observed with light and scanning electron microscopy (SEM) to identify areas of interest for analysis by inductively coupled plasma mass spectrometry laser ablation (ICP-MS-LA). SEM backscattered electron images and QEMSCAN mineral mapping helped determine the spatial distribution of the sulfide, sulfate, and carbonate minerals of interest. Energy dispersive spectroscopy was used to obtain semi-quantitative spot chemical analyses of minerals. SEM images show significant quantities of carbonates (CaCO3), barite (BaSO4) and celestite (SrSO4) which may be the sources of high levels of Ba and Sr in flowback fluids previously reported. Analysis from ICP-MS-LA line profiles across a pyrite/carbonate mineral assemblage and surrounding silt and clay-size carbonate/silicate matrix show major elements Mg, Ca, Sr, Ba, Al, Na, Ti, Fe, S, Si and trace elements Mo, Mn, Ni, Zn, La, Ce, U, Th, Rb. Barium concentrations were low in the pyrite and carbonate shells but ranged from 50 to 500 ppm in aluminosilicate clays in the matrix and up to 500,000 ppm in barite. Strontium concentrations ranged from 100 to 500 ppm in the pyrite but range 4000-6000 ppm in the carbonate shells and finer-grained clay-carbonate matrix. ii A CKNOWLEDGEMENTS I would like to thank the following individuals and organizations who made my entire project possible: Steve Chipera and Chesapeake Energy for providing the samples and well data for this study, everyone associated with the Subsurface Energy Materials Characterization and Analysis Lab (SEMCAL), Dr. Dave Cole, Dr. Julie Sheets, Dr. Susan Welch, Alex Swift, Derek Foley, and Edwin Buchwalter for use of their facilities, knowledge, guidance, and collaboration. I would also like to thank Dr. John Olesik for his expertise and guidance with inductive coupled plasma mass spectrometry laser ablation (ICP-MS-LA). Appreciation goes to the entire faculty, students, and staff of The Ohio State University’s School of Earth Sciences for being a truly special place to spend time pursuing my second bachelor’s degree. I would like to thank all the professors that have imparted their knowledge in the classes I have taken and contributed to my overall understanding of the Earth Sciences: Dr. Panero, Dr. Barton, Dr. Krissek, Dr. Cox, Dr. Royce, Dr. Lyons, Dr. Cook, Dr. Carey, Dr. Wilkins, Dr. Wilson, and Dale Gnidovec. I also would like to thank the School of Earth Sciences for maintaining their Field Geology program. Particularly, I want to thank Dr. Kelley, Dr. Wilson, Dr. Judge, Dr. Millan, and Dr. Darrah, the states of Utah & Nevada, and my TA’s Trish Hall & Will Blocher for their hard work, time, and commitment. Likewise, I would like to recognize my roommates Alex Grady, Sam Perry, and Murvin Morrow for making field camp one of the best experiences in my life. In addition, I would like to thank Mario Gutierrez, John Daniele, Lienne Sethna, Drew Sabula, Laura Miller, Abbie Bowman, Megan Mave, Ken Peterman, and Myles Moore for satiating all the great clichés about geologists. Special thanks to my undergraduate advisor, Dr. Anne Carey for her help, support, and patience. The utmost appreciation goes to my research advisor, Dr. Dave Cole, for his wealth of knowledge, top-notch facilities, and advice. Lastly, I would like to thank my parents and the rest of my family for being incredibly supportive of my decision to pursue a second bachelor’s degree. iii L IST OF F IGURES 1. Leica Images……………………………………………………………………………...8-9 2. SEM Images…………………………………………………………………………...10-11 3. Laser Ablation Graphs………………………………………………………………....15-25 4. Laser Ablation Site E SEM images..…………………………………………………....36-38 5. Laser Ablation Site E Graphs………………………………………………………….86-87 iv L IST OF T ABLES 1. Chesapeake Mineralogical and Petrophysical Data……………………………..…………...7 2. EDX Carbonate Analysis………………………………………………………………….12 3. Barite Estimation Calculation……………………………………………………………...13 4. Calculations of barium in bulk mineralogy…………………………...……………………27 5. Sr/Ca ratios relation with Kd……………………………………………………………...29 6. Laser ablation raw data………………………………………………………………...39-85 v I NTRODUCTION Since the shale gas boom began, there has been immense concern about the fluids and chemicals associated with hydraulic fracturing. Flowback water is defined as water that has returned to the surface when pressure is released on a hydraulically fractured well. Most of the flowback water returns to the surface within the first few days to weeks after the wells are hydraulically fractured. The remainder of the returns overtime during the production phase, when hydrocarbons are extracted from the wellsite. The water quality of the flowback waters can be affected by the chemistry of fluids in contact with the formation, fluids within the formation water, the formation itself, the amount of time the fluid was retained in the well, and the initial quality of the fluids used in the process (Vazquez et al., 2014). Although the interactions with dissolved substances in the subsurface is still being studied, it is important to note that when flowback waters return to the surface, an immense amount of water-rock interaction has taken place. These interactions have the potential to mobilize many different types of chemical compounds, which is why understanding the trace element composition of the Utica/Point Pleasant formation is important. Monitoring of trace element concentrations has been used to assess the potential environmental impact of flowback water and design strategies for how to process and dispose of the fluids. Trace elements are defined as elements with concentrations less than 0.1% in the Earth's crust (Harris et al., 2013). They are utilized to identify associations among trace elements themselves, and to identify paleoceanographic conditions and depositional processes (Harris et al., 2013). They can also be used to investigate the composition of the fluids associated with gas shale systems and detect substances potentially harmful to human health and the environment. The trace element composition of the Utica/Point Pleasant formations are of particular interest because these organic carbon rich formations are a major source of hydrocarbons. Previous studies have examined flowback waters to measure trace elements compositions and have shown high concentrations of total dissolved salts (TDS), Cl, Br, Na, Ca, Sr, Ba, Ra, and other elements. The levels of TDS, Cl and other elements are as much as 5-10 times the concentration of seawater (Haluszczak et al., 2013). Concentrations of 226Ra, 228Ra, and Ba have been found to be significantly higher than what is allowed for drinking water limits (Haluszczak et al., 2013). Flowback waters from wellsites located in or near the Appalachian Basin have been shown to contain elevated levels of barium and strontium levels as high as 3g/L (Rozell and Reaven, 2012). The levels deviate from normal water near wellsites which have Sr/Ca ratios of about 1/100 mg/L and Sr/Mg ratios of about 1/50 mg/L for water (Rozell and Reaven, 2012). Barium in high concentrations