September 2015 Understanding and Managing Environmental Roadblocks to Shale Gas Development: An Analysis of Shallow Gas, NORM, and Trace Metals Final Report June 14, 2013 to September 30, 2015 RPSEA Award No 11122-56 by J.-P. Nicot, P. Mickler, T. Larson, M.C. Castro R. Darvari, R. Smyth, K. Uhlman, C. Omelon with participation of L. Bouvier, Tao Wen, Z.L. Hildenbrand, M. Slotten, J.M. Aldrige, C.M. Hall, R. Costley, J. Anderson, R. Reedy, J. Lu, Yuan Liu, K. Romanak, S.L. Porse, and Texas Water Development Board Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin Austin, Texas 78713-8924 Understanding and Managing Environmental Roadblocks to Shale Gas Development: An Analysis of Shallow Gas, NORM, and Trace Metals Jean-Philippe Nicot1, Patrick Mickler1, Toti Larson2, M. Clara Castro3 Roxana Darvari1, Rebecca Smyth1, Kristine Uhlman+1, Christopher Omelon2 with participation of L. Bouvier+3, Tao Wen3, Z.L. Hildenbrand4, M. Slotten+5, J.M. Aldrige+5, C.M. Hall3, R. Costley1, J. Anderson1, R. Reedy1, J. Lu1, Yuan Liu+1, K. Romanak1, S.L. Porse+1, and TWDB6 1: Bureau of Economic Geology, The University of Texas at Austin 2: Department of Geological Sciences, The University of Texas at Austin 3: Department of Earth and Environmental Sciences, University of Michigan at Ann Arbor 4: Inform Environmental LLC, Dallas, TX 5: Environmental Management and Sustainability Program, St. Edwards University, Austin, TX 6: Texas Water Development Board, Austin, TX +: previously at Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin Austin, Texas 78713-8924 Disclaimer From DOE/NETL: “This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.” From RPSEA: “Funding for this project is provided by RPSEA through the “Ultra-Deepwater and Unconventional Natural Gas and Other Petroleum Resources” program authorized by the U.S. Energy Policy Act of 2005. RPSEA (www.rpsea.org) is a nonprofit corporation whose mission is to provide a stewardship role in ensuring the focused research, development and deployment of safe and environmentally responsible technology that can effectively deliver hydrocarbons from domestic resources to the citizens of the United States. RPSEA, operating as a consortium of premier U.S. energy research universities, industry, and independent research organizations, manages the program under a contract with the U.S. Department of Energy’s National Energy Technology Laboratory.” i Abstract The main objective of the project was to document occurrences of shallow gas in fresh-water aquifers in Texas either dissolved or free phase and identify controlling processes. A secondary somewhat independent objective was to contribute to the understanding of the nature and variability of flowback and produced water associated with hydraulic fracturing in the context of rock-water interactions. We undertook a large sampling campaign of aquifers in the footprint of major Texas plays (900+ water samples): Barnett in north-central Texas (555 unique locations), Eagle Ford in South Texas (118 unique locations), Haynesville in East Texas (70 unique locations), and in the Delaware Basin of West Texas (40 unique locations). Most of the wells (2/3) are relatively shallow residential wells sampled at or as close as possible to the wellhead but many wells are irrigation, municipal, or rig-supply wells. All samples were analyzed for major ions, dissolved gases, and, when CH4>0.1 mg/L, for methane and light alkanes carbon isotopes and trace elements. The vast majority of wells show some measurable methane and ~100 wells show methane >0.1 mg/L. A total of ~20 wells have methane concentrations >10 mg/L, these high concentrations were observed in all plays and present at least a thermogenic component. Some wells, generally with a <10 mg/L concentration, show a clear microbial origin for methane. A number of samples show mixing between the two origins but also more complex behavior such as methane degradation. Samples with thermogenic methane are generally spatially organized in clusters. Overall the source of the dissolved methane is likely natural sourced from shallow natural gas accumulations in the Barnett Shale, lignite beds associated with a fault in the Haynesville shale, and lignite and degradation of oil and deep organic matter associated with a fractured zone in the Eagle Ford Shale. The Delaware Basin samples show no dissolved methane other than associated to a recent blowout. We also performed autoclave experiments in controlled conditions exposing shale core fragments to various fluids, examining reacted and unreacted rocks and documenting chemical composition of the evolving fluid through time. The experiments demonstrated that shales undergo typical geochemical processes during hydraulic fracturing such as carbonate and feldspar dissolution as well as ion exchange resulting in an increase in dissolved solids. Observations suggest that rock permeability is increased two to –three-fold and that porosity is increased by 50%. Baseline sampling as it is currently practiced is not sufficient to resolve ambiguity of the source of the dissolved methane even if of thermogenic origin because it still could be natural. Additional analyses such as noble gases and isotopes are needed to better constrain origin of the methane. iii Executive Summary The main objective of the project was to enhance our understanding of shallow natural gas which is sometimes found unexpectedly in groundwater wells. The visibility of this topic has considerably increased in the past few years because of a possible connection with hydraulic fracturing (HF). A second objective, only loosely connected to the first one, was to understand the nature of the flowback and produced water flowing from wells stimulated by HF. We addressed the first objective by sampling hundreds of water wells across the state of Texas and performing detailed chemical analysis of the water. The second objective was accomplished by performing rock-water interaction experiments at high temperature and pressure in a laboratory autoclave. Methane is a nontoxic but explosive gas that has been documented to exist in many groundwater aquifers. Methane in the subsurface is formed through two major types of processes: biodegradation of organic material (for example, organic matter from soil, oil, lignite debris), termed microbial, or abiotic maturation of organic matter when it is buried to form coal of various rank, oil and gas; this methane is termed thermogenic. The two endmembers can be identified through their isotopic signature and other geochemical characteristics. At the onset on the project it was expected that several methane studies already existed in the state and that the project would focus on understanding mechanisms of its migration. It turned out that a large sampling campaign was needed. We focused the sampling on the footprint of some major unconventional plays: the Barnett Shale in northcentral Texas (only its section with condensate- and gas-producing wells), the Haynesville Shale in East Texas, the Eagle Ford in South Texas, and the plays of the Delaware Basin in West Texas. Autoclave experiments were done using Barnett Shale core fragments that were exposed to water of various salinities (0, 2000, and 20,000 ppm) and composition (either sodium, potassium, or calcium chloride) for three weeks. Unreacted and reacted samples were examined using classic (SEM, EDS, XRD) and more recent (ion-milling) technologies. A few flowback water and produced gas samples were also taken in the Barnett Shale footprint. Chemical analyses of the groundwater samples and rock-water interactions samples were performed at UT (IC for major ions and ICP for trace metals). Dissolved gas (CH4 and other light alkanes, 13 15 N2, O2, Ar) and isotopic ( C –if CH4>0.1 mg/L, D, N) analyses were also performed at UT. All the dissolved gas samples were carefully taken at the wellhead and shipped promptly to Austin. Dissolved noble gases were sampled following the copper tube approach and analyses were performed at the University of Michigan. A few microbial mass samples were also taken to better document methane production or attenuation in the areas with high methane concentrations. We sampled 555 unique water wells in the Barnett Shale footprint (shale at ~6000 ft below ground surface), sometimes sampling several times the same well. See opposite map showing gas wells (small red dots) and sampled water wells. Most water wells sampled on the v western edge of the project area were domestic wells tapping the Trinity aquifer but towards the east in the direction of more populated area and increasing depth of the producing aquifers, many sampled water