Hydraulic fracturing operations utilized for shale gas production result in the generation of a large volume of flowback and produced water that contain suspended material, salts, hydrocarbons, metals, chemical additives, and naturally-occurring radioactive material. The water is impounded at drilling sites or treated off-site, resulting in significant generation of residual solids. These are either buried on site or are disposed in lined landfills. The objective of this study was to determine the levels of heavy metals and other elements of concern that will leach from these residual solids when placed in typical disposal environments. For this purpose, laboratory leaching experiments were employed wherein representative samples were brought into contact with a liquid to determine the constituents that would be leached by the liquid and potentially released into the environment. The samples used included sludge resulting from the physicochemical treatment of process water (TS), sludge solidified with cement kiln dust (SS), raw solids obtained by gravity separation of process water (RS), and drilling mud (DM). The samples were subjected to both single extraction (i.e. Shake Extraction Test, SET) and multiple extraction (i.e. Immersion Test, IT) leaching tests. For the shake extraction test, samples were mixed with a specific amount of leaching solution without renewal over a short time period. In the immersion test, samples were immersed in a specific amount of leaching solution that was periodically renewed over a longer period of time. For both these tests, analyses were performed on the filtered eluate. The tests were performed as per standards with modifications. Distilled de-ionized water, synthetic acid rain (pH ~ 4.2), weak acetic acid (pH ~ 2.88), and synthetic landfill leachate were used as leaching solutions to mimic specific disposal environments. Alkali metals (Li, K, Na), alkaline earth metals (Ba, Ca, Mg, Sr) and a halide (Br), which are typically associated with Marcellus shale and produced waters, leached at high concentrations from most of the residual solids sample. The SS sample, due to its stabilization with CKD, had a lower extraction efficiency as compared to the unconsolidated TS and RS samples. In EF 2.9 and EF SLL, the leaching took place under acidic conditions, while for EF DDI and EF 4.2, the leaching occurred in alkaline conditions. EF 2.9 and EF SLL were determined to be the most aggressive leaching solutions, causing the maximum solubility of most inorganic elements. Thus, high amounts of most EOCs may leach from these residual solids in MSW landfills disposed under co-disposal conditions. Agitation, pH and composition of the leaching solution were determined to be important variables in evaluating the leaching potential of a sample. The results of this study should help with the design of further research experiments being undertaken to develop environmentally responsible management/disposal strategies for these residual solids and also prove useful for regulatory authorities in their efforts to develop specific guidelines for the disposal of residuals from shale gas production operations. / Master of Science

<p>Human activities represent a significant burden on the global water cycle, with large and increasing demands placed on limited water resources by manufacturing, energy production and domestic water use. In addition to changing the quantity of available water resources, human activities lead to changes in water quality by introducing a large and often poorly-characterized array of chemical pollutants, which may negatively impact biodiversity in aquatic ecosystems, leading to impairment of valuable ecosystem functions and services. Domestic and industrial wastewaters represent a significant source of pollution to the aquatic environment due to inadequate or incomplete removal of chemicals introduced into waters by human activities. Currently, incomplete chemical characterization of treated wastewaters limits comprehensive risk assessment of this ubiquitous impact to water. In particular, a significant fraction of the organic chemical composition of treated industrial and domestic wastewaters remains uncharacterized at the molecular level. Efforts aimed at reducing the impacts of water pollution on aquatic ecosystems critically require knowledge of the composition of wastewaters to develop interventions capable of protecting our precious natural water resources.</p><p>The goal of this dissertation was to develop a robust, extensible and high-throughput framework for the comprehensive characterization of organic micropollutants in wastewaters by high-resolution accurate-mass mass spectrometry. High-resolution mass spectrometry provides the most powerful analytical technique available for assessing the occurrence and fate of organic pollutants in the water cycle. However, significant limitations in data processing, analysis and interpretation have limited this technique in achieving comprehensive characterization of organic pollutants occurring in natural and built environments. My work aimed to address these challenges by development of automated workflows for the structural characterization of organic pollutants in wastewater and wastewater impacted environments by high-resolution mass spectrometry, and to apply these methods in combination with novel data handling routines to conduct detailed fate studies of wastewater-derived organic micropollutants in the aquatic environment. </p><p>In Chapter 2, chemoinformatic tools were implemented along with novel non-targeted mass spectrometric analytical methods to characterize, map, and explore an environmentally-relevant “chemical space” in municipal wastewater. This was accomplished by characterizing the molecular composition of known wastewater-derived organic pollutants and substances that are prioritized as potential wastewater contaminants, using these databases to evaluate the pollutant-likeness of structures postulated for unknown organic compounds that I detected in wastewater extracts using high-resolution mass spectrometry approaches. Results showed that application of multiple computational mass spectrometric tools to structural elucidation of unknown organic pollutants arising in wastewaters improved the efficiency and veracity of screening approaches based on high-resolution mass spectrometry. Furthermore, structural similarity searching was essential for prioritizing substances sharing structural features with known organic pollutants or industrial and consumer chemicals that could enter the environment through use or disposal.</p><p>I then applied this comprehensive methodological and computational non-targeted analysis workflow to micropollutant fate analysis in domestic wastewaters (Chapter 3), surface waters impacted by water reuse activities (Chapter 4) and effluents of wastewater treatment facilities receiving wastewater from oil and gas extraction activities (Chapter 5). In Chapter 3, I showed that application of chemometric tools aided in the prioritization of non-targeted compounds arising at various stages of conventional wastewater treatment by partitioning high dimensional data into rational chemical categories based on knowledge of organic chemical fate processes, resulting in the classification of organic micropollutants based on their occurrence and/or removal during treatment. Similarly, in Chapter 4, high-resolution sampling and broad-spectrum targeted and non-targeted chemical analysis were applied to assess the occurrence and fate of organic micropollutants in a water reuse application, wherein reclaimed wastewater was applied for irrigation of turf grass. Results showed that organic micropollutant composition of surface waters receiving runoff from wastewater irrigated areas appeared to be minimally impacted by wastewater-derived organic micropollutants. Finally, Chapter 5 presents results of the comprehensive organic chemical composition of oil and gas wastewaters treated for surface water discharge. Concurrent analysis of effluent samples by complementary, broad-spectrum analytical techniques, revealed that low-levels of hydrophobic organic contaminants, but elevated concentrations of polymeric surfactants, which may effect the fate and analysis of contaminants of concern in oil and gas wastewaters. </p><p>Taken together, my work represents significant progress in the characterization of polar organic chemical pollutants associated with wastewater-impacted environments by high-resolution mass spectrometry. Application of these comprehensive methods to examine micropollutant fate processes in wastewater treatment systems, water reuse environments, and water applications in oil/gas exploration yielded new insights into the factors that influence transport, transformation, and persistence of organic micropollutants in these systems across an unprecedented breadth of chemical space.</p> / Dissertation

Master of Science / Department of Chemical Engineering / James Edgar / In the past decade the technique of horizontal drilling and hydraulic fracturing has been improved so much that it has become a cost effective method to extract natural gas from shale formations deep below the earth’s surface. Natural gas extraction has boomed in the past few years in the United States, enough that it has driven prices to an all time low. The amount of natural gas reserves in the U.S. has led to claims that it can lead the country to energy independence. It has also been touted as a cleaner fuel for electricity generation and to power vehicles. This report explains hydraulic fracturing and horizontal drilling particularly with regards to utilizing the techniques for natural gas extraction from shale gas. It also discusses the environmental impact due to the drilling and gas extraction. It demonstrates that although the natural gas beneath the U.S. is a valuable resource, the impacts to the planet and mankind are not to be taken lightly. There is the potential for the effects to be long term and detrimental if measures are not taken now to control them. In addition although on the surface natural gas seems to be a greener fuel, particularly in comparison to gasoline, it is also considered worse for the environment.

[pt] A técnica para estimulação de um campo de petróleo através de fraturamento hidráulico inclui a injeção, com o fluido de fraturamento, de um material para sustentação da abertura da fratura, denominado propante. Uma das dificuldades deste processo é o refluxo do material de sustentação para o interior do poço durante a fase de produção de óleo, ocasionando diversos problemas que podem chegar, em situações extremas, à interrupção definitiva da produção. O controle do fluxo de propante representa, portanto, um grande desafio para a indústria do petróleo. Alguns modelos empíricos - correlação Stimlab, modelo de cunha livre, modelo da velocidade mínima de fluidificação, modelo semi- mecânico - foram desenvolvidos para a previsão desse fenômeno, mas não contemplam todas as variáveis que influenciam no refluxo do material de sustentação da fratura. Uma alternativa aos modelos empíricos é utilizar o método dos elementos discretos para simular computacionalmente a instabilidade do pacote granular. Nesta dissertação busca-se modelar o comportamento do refluxo do propante utilizando uma modelagem 3D da fratura, partículas e fluxo de óleo com auxílio do programa computacional PFC3D baseado no método dos elementos discretos. Os dados das análises (tipos de propante, temperatura, características do fluido e do propante, etc) se referem a 4 cenários principais considerando fraturas sob diversos níveis de tensão e forças de arraste. Foram feitas discussões considerando os resultados numéricos obtidos por análises computacionais bi e tridimensionais, bem como comparações com modelos empíricos de previsão do refluxo do material de sustentação. / [en] The technique for stimulating an oil field through hydraulic fracturing consists of pumping into the oil bore the fracturing fluid mixed with a material to hold the fracture open, called proppant. One of the difficulties in this process is the occurrence of proppant flowback into the well bore during oil production, causing several problems that can result, in critical situations, in a definitive interruption of the oil production. Control of proppant flowback represents a great challenge for the petroleum industry. Some empirical models - Stimlab correlation, propped- free wedge model, minimum fluidization velocity, semi-mechanistic model - were developed for prediction of proppant flowback, yet they do not encompass all variable that play a role in this complex phenomenon. An alternative is to employ the discrete element method in order to computationally simulate the instability of the granular package. The main goal of this thesis is to investigate the proppant flowback phenomenon, through a 3D model of the fracture, particles and flow conditions using the computational program PFC3D, a code based on the discrete element method. The input data (type of proppant, temperature, characteristics of the fluid and proppant, etc.) relate to 4 main scenarios that consider fractures under several levels of stress closure and drag forces. The numerical results computed from 2D and 3D analyses were discussed, as well as comparisons were done with the predictions obtained with empirical methods.

Cette thèse presente des travaux et résultats d'expériences de fracturation dont l'origine est une génération interne de fluides induite par des réactions chimiques dans des échantillons de roches et des matériaux analogues. Les deux premiers articles portent sur une expérience avec des échantillons de schistes imagés par tomographie aux rayons X au cours du temps. Le premier article décrit la formation de fractures créées par l'augmentation de pression induite par la décomposition de matière organique lorsque les schistes sont chauffés. Le deuxième article porte sur la procédure expérimentale et l'analyse d'images, utilisées pour obtenir les résultats du premier article. Les deux autres articles concernent la fracturation d'une couche de gélatine contenant de la levure et du sucre, ce qui génère du CO2. Le troisième article décrit le mécanisme de formation d'un réseau de fractures au cours du drainage du CO2 contenu dans la gélatine. Le quatrième article concerne l'évolution du réseau de fractures au cours de ce drainage, ainsi que les mécanismes d'ouverture et fermeture des fractures. Le dernier article porte sur une étude par tomographie aux rayons X de la distribution de porosité d'échantillons endommagés d'andésite. Les méthodes développées dans ce projet peuvent s'appliquer à la déshydratation de sédiments, la formation de volcans de boue, l'exploration d'hydrates de méthane, la séquestration de CO2 et la fracturation de réservoirs non conventionnels. / This thesis presents the experimental work and the results on fracturing of rock samples and analogue materials due to internal fluid generation during chemical reaction. The first two papers concentrate on time-resolved 3D X-ray imaging experiment on organic-rich shale samples. Paper 1 describes fracture formation due to hydrocarbon generation in the shale induced by organic matter decomposition during heating. Paper 2 gives an overview of the experimental procedure and image analysis workflow, which were used to obtain results presented in the first paper. The other two papers are focused on fracturing of gelatin mixed with yeast and sugar, which generates CO2. Paper 3 describes the mechanism of fracture network formation during draining of CO2 out of a gelatine layer. Paper 4 focuses on the temporal evolution of the drainage network and the mechanism of fracture opening and closing. The last paper presents a study in which X-ray microtomography was used to characterize porosity distribution in weathered andesite samples. The scientific methods developed in this project have potential application in studying dehydration of sediments, formation of mud volcanoes, methane hydrate exploration and assessment, geological sequestration of carbon dioxide CO2 and hydraulic fracturing of unconventional reservoirs.

The role of surface chemical effects in hydraulic fracturing of shale is studied using the results of unconfined compression tests and Brazilian tests on Mancos shale- cored at depths of 20-60 ft. The rock mineralogy, total organic carbon and cation exchange capacity were determined in order to characterize the shale. Adsorption tests to study the interaction of the shale and aqueous fluid mixture were also carried out using surface tension measurements. The uniaxial compressive strengths and tensile strengths of individual shale samples after four hours exposure to water, 2.85 x 10^-3 M cationic surfactant (dodecyltrimethylammonium bromide-DTAB) and 2.81 x 10^-3 M anionic surfactant (sodium dodecylbenzenesulfonate-SDBS) were analyzed using ANOVA and Bonferroni tests. These mechanical strengths were largely reduced on exposure to the aqueous environments studied, despite the relatively low clay and low swelling clay content of the Mancos shale. Further comparison of the uniaxial compressive strengths and tensile strengths of the shale on exposure to water, to the strengths when exposed to the surfactant solutions showed that their difference was not statistically significant indicating that exposure to water had the greatest effect on strength loss. The surface tension measurement of 2.85 x 10^-4 M DTAB and 2.81 x 10^-4 M SDBS solutions before and after equilibration with shale showed about 80% increase in surface tension in the DTAB solution and 10% increase in surface tension in the SDBS solution. The probable sorption mechanism is electrostatic attraction with negatively charged sites of the shale as shown by significant loss of the cationic surfactant (DTAB) to the shale surface, and the relatively minor adsorption capacity of the anionic surfactant (SDBS). Although these adsorption tests indicate interaction between the shale and surfactant solutions, within the number of tests carried out and the surfactant concentration used, the interaction does not translate into a significant statistical difference for impacts of surfactants on mechanical strength of this shale compared to the impact of water alone. The relevance of this work is to facilitate the understanding of how the strength of rock can be reduced by the composition of hydraulic fracturing fluids, to achieve improved fracture performance and higher recovery of natural gas from shale reservoirs.

This thesis looks at the current fracking debate on a national scale, before focusing specifically on how this debate is playing out in the landscape of Central Arkansas. Focusing on the lack of national regulation, the unique array of state regulations that have popped up are assessed in their effectiveness on the ground through speaking with residents of the area. The demographics of these residents are analyzed within an assessment of environmental injustice vulnerability. This ethnographic approach also compares the de jure v. de facto outcomes of these regulations through the narratives of residents working with organizations across the political spectrum, and specifically seeks to gauge their own personal stories and experiences with regulators and the fracking industry. Other key actors are identified. This thesis concludes that agency capture is a reality for these residents, and their perceived powerlessness drastically increases the power of the gas companies that monopolize the political agenda in the region.

The large amount of produced oil and gas come from conventional resources all over the world and these resources are being depleted rapidly. This fact and the increasing oil and gas prices force the producing countries to find and search for new methods to recover more oil and gas. In order to meet the demand, the oil and gas industry has been turning towards to unconventional oil and gas reservoirs which become more popular every passing day. In recent years, they are seriously considered as supplementary to the conventional resources although these reservoirs cannot be produced at an economic rate or cannot produce economic volumes of oil and gas without assistance from massive stimulation treatments, special recovery processes or advanced technologies. The vast increase in demand for petroleum and gas has encouraged the new technological development and implementation. A wide range of technologies have been developed and deployed since 1980. With the wellbore technology, it is possible to make use of highly deviated wellbores, extended reach drilling, horizontal wells, multilateral wells and so on. All of the new technologies and a large number of new innovations have allowed development of increasingly complex economically marginal fields where shale gas and coal bed methane are found. In this study, primary target is to compare different production methods in order to obtain better well performance and improved production from different types of reservoirs. It is also be given some technical information regarding the challenges such as hydraulic fracturing and multilateral well configuration of the unconventional gas reservoir modeling and simulation. With the help of advances in algorithms, computer power, and integrated software, it is possible to apply and analyze the effect of the different well trajectories such as vertical, horizontal, and multilateral well on the future production performance of coal bed methane, shale gas, and tight gas reservoirs. A commercial simulator will be used to run the simulations and achieve the best-case scenarios. The study will lead the determination of optimum production methods for three different reservoirs that are explained above under the various circumstances and the understanding the production characteristic and profile of unconventional gas systems.

Single Ventricle congenital heart defects with cyanotic mixing between systemic and pulmonary circulations afflict 2 per 1000 live births. The total cavo-pulmonary connection (TCPC), where the superior and inferior vena cavae are sutured to the left and right pulmonary arteries, is the current procedure of choice. It is believed that reducing the fluid mechanical power losses in the TCPC will relieve strain on the single functional ventricle. It is hypothesized that a proposed idealized TCPC design, decreases power losses to a level below that of any other TCPC designs, while providing other advantages and increased flexibility. Physical models with slightly different geometries of the proposed design were created, and in vitro experiments carried out with particle image velocimetry (PIV), phase contrast magnetic resonance imaging (PC-MRI), and control volume flow analysis at physiological flow rates. Computational fluid dynamics (CFD) was used for numerical studies of the same geometries as in the physical models. Power losses were calculated using the control volume method and the viscous power dissipation function. The latter method incorporated registration of high-resolution PC-MRI velocity vectors to tetrahedral meshes followed by inverse interpolation of the vectors onto the meshes. Detailed flow structures were analyzed. Results show that the new design is more energy efficient than any other idealized models. Furthermore, a tool was developed to extract flow and vessel information from PC-MRI datasets obtained from patients with Fontan connections. The tool utilized a display algorithm, which was developed for optimal noise detection in PC-MRI images. This enabled accurate segmentation. Comparing PC-MRI images before and after this accurate segmentation showed that the standard deviations of the pixels at the perimeter of the segmented vessel were statistically significantly smaller after the segmentation in 94.1% of the datasets investigated. The developed tool was able to extract flow, flow in the quadrants of vessels, area of the segmented vessel, velocities and pulsatility indices. The velocity vectors were exported for use as CFD boundary conditions in models reconstructed from patient anatomies. A database was created with patient PC-MRI data from approximately 140 patients, which is probably the largest database in the world.

Hydraulic fracturing plays an important role in increasing production rate in tight reservoirs. The performance of the reservoir after fracturing can be observed from the productivity index. This parameter is dependent on the fracture geometry; height, length and width. Unified fracture design (UFD) offers a method to determine the fracture dimensions providing the maximum productivity index for a specific proppant amount. Then, in order to achieve the maximum productivity index, the treatment schedules including the amount of liquid and proppant used for each stage must be determined according to the fracture dimensions obtained from the UFD. The proppant number is necessary for determining the fracture geometry using the UFD. This number is used to find the maximum productivity index for a given proppant amount. Then, the dimensionless fracture conductivity index corresponding to the maximum productivity index can be computed. The penetration ration, the fracture length, and the propped fracture width can be computed from the dimensionless fracture conductivity. However, calculating the proppant number used in UFD requires the fracture height as an input. The most convenient way to estimate fracture height to input to the UFD is to assume that the fracture height is restricted by stress contrast between the pay zone and over and under-lying layers. In other words, the fracture height is assumed to be constant, independent of net pressure and equal to the thickness of the layer which has the least minimum principal stress. However, in reality, the fracture may grow out from the target formation and the height of fracture is dependent on the net pressure during the treatment. Therefore, it is necessary to couple determination of the fracture height with determination of the other fracture parameters. In this research, equilibrium height theory is applied to rigorously determine the height of fracture. Solving the problem iteratively, it is possible to incorporate the rigorous fracture height determination into the unified fracture design.