A techno-economic framework for mitigating environmental liabilities from unconventional oil and gas operations in the United States
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Unconventional oil and gas (O&G) activity is associated with many environmental liabilities including 1) high water use, 2) substantial volumes of generated wastewater, and 3) flaring of co-produced natural gas. The work in this dissertation aims to holistically examine and find strategies to mitigate these environmental challenges through three studies: 1. Designing a method to select the most appropriate wastewater treatment technology or product based on numerous metrics and across many potential options. 2. Conducting an inventory and engineering assessment of the flared gas and wastewater. 3. Building a decision tree model to investigate and compare the economic feasibility of several potential traditional and nontraditional produced water management pathways, including treatment, disposal, discharge, and crop production. Based on the results of these analyses, the following general conclusions are drawn: The first study shows, through the tremendous number of technologies and products that claim to handle wastewater associated with O&G activities, mechanical vapor recompression, and to a lesser extent, reverse osmosis are the top contenders when treating to freshwater standards is desired. In the process, a down-selection tool that can be tailored to an operator’s specific requirements and a database containing many of the available technologies and products were created. The second study shows that from the seven prominent shale regions included in this analysis, Marcellus/Utica (in the Northeast), Bakken (North Dakota), and Niobrara (Rocky Mountains) flared between 2 and 48 times the amount of natural gas needed to provide energy for treatment of their wastewater volumes. The Permian Basin, Eagle Ford, and Haynesville did not have sufficient flared gas to treat wastewater produced in each respective region. As such, these regions would require additional energy sources for wastewater treatment. The third study shows that several nontraditional produced water management pathways might be economically feasible depending on the realized 1) price for the commodities produced and 2) cost associated with implementing the strategy. In this case, the traditional pathway to minimally treat and discharge to a nearby stream had the highest expected value by a slim margin over growing switchgrass onsite. This result suggests that further investigation should be considered to determine, with greater certainty, the attainable price for switchgrass. These general conclusions, along with further details, provide insight into the challenges and mitigation strategies with some of the environmental liabilities associated with unconventional O&G activity. As onsite resources (e.g., available water) become more constrained and regulations become more stringent (e.g., curtailment of flaring), implementing these or similar approaches to the industry’s waste streams will become increasingly imperative.