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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Characterisation of natural radioactivity in Karoo Basin groundwater prior to shale gas exploration

Botha, Ryno January 2017 (has links)
Magister Scientiae - MSc / The prospect of unconventional shale-gas development in the Karoo Basin (South Africa) has created the need to obtain baseline data on natural radioactivity in Karoo groundwaters. The Karoo Basin groundwater radiological baseline developed through this study could serve as a reference to research potential future radiological contamination effects due to hydraulic fracturing. The major naturally occurring radioactive material (NORM) studied was radon (222Rn), in particular in-water activity concentrations; however, supplementary radium (226Ra and 228Ra) in-water activity concentrations and uranium (238U) in-water concentrations measurements were also made. A total of 53 aquifers across three provinces were sampled for groundwater and measured, with three measurement series from 2014 to 2016. The aquifers were categorized as shallow, mixed, or deep source. The radon-in-water baseline of the Karoo Basin can be characterised by a minimum of 0.6 ± 0.9 Bq/L, a maximum of 183 ± 18 Bq/L and mean of 41 ± 5 Bq/L. The radon-in-water levels from shallow sources (with water temperature < 20 °C) were systematically higher (40 Bq/L) than for deep sources (with water temperature > 20 °C). The natural fluctuations in radon-in-water levels were predominantly associated with shallow aquifers compared to almost none observed in the deep sources. The uranium in-water baseline can be characterised by a minimum of below detection level, a maximum of 41 μg/L, and the mean of 5.10 ± 0.80 μg/L. Similar to radon-in-water levels, uranium in-water levels for shallow sources were systematically higher than for deep sources. The limited (six aquifers) radium (228Ra and 226Ra) in-water activity-concentration measurement results were very low, with a maximum of 0.008 Bq/L (226Ra) and 0.015 Bq/L (228Ra). The 228Ra/226Ra ratio baseline were characterised by a minimum of 0.93, a mean of 3.3 ± 1.3, and a maximum of 6.5. The radium isotopes’ activity concentration ratio is an isotopic tracer for hydraulic fracturing wastewater. Pollution and contamination (radiological), due to unconventional shale gas development, in water resources has been noticed in the Marcellus Basin (United States). Consequently, developing and improving continuous baseline monitoring are of importance to study the environmental radiological effect of hydraulic fracturing.
42

Transporting and Disposing of Wastewater from North Dakota Oil Producers

Yin, Qingqing January 2012 (has links)
North Dakota’s oil boom is aided by a new technology, fracking. But this technology implies large amounts of wastewater. The methods of dealing with this wastewater are now an issue. Currently, North Dakota locks it into deep injection wells in the Bakken formation. With the development of membrane technologies to treat wastewater, it may be feasible to treat the wastewater and reuse it. This study uses a mathematical programming model to minimize the total cost of dealing with wastewater using three methods - deep well injection, on-site treatment, and off-site treatment. The model results show it is cost-effective to use on-site and large capacity off-site treatment to treat the 20% of the wastewater that flows back within the first 30-60 days after a well is drilled.
43

Modeling Impact of Hydraulic Fracturing and Climate Change on Stream Low Flows: A Case Study of Muskingum Watershed in Eastern Ohio

Shrestha, Aashish January 2014 (has links)
No description available.
44

Fully coupled fluid flow and geomechanics in the study of hydraulic fracturing and post-fracture production

Aghighi, Mohammad Ali, Petroleum Engineering, Faculty of Engineering, UNSW January 2007 (has links)
This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.
45

Fully coupled fluid flow and geomechanics in the study of hydraulic fracturing and post-fracture production

Aghighi, Mohammad Ali, Petroleum Engineering, Faculty of Engineering, UNSW January 2007 (has links)
This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.
46

Poststructuralist Critical Rhetorical Analysis as a Problem Analysis Tool: A Case Study of Information Impact in Denton’s Hydraulic Fracturing Debate

Sykes, Jason 05 1900 (has links)
Energy and the natural environment are central concerns among stakeholders across the globe. Decisions on this scale often require interaction among a myriad of institutions and individuals who navigate a complex variety of challenges. In Denton, Texas in 2014, voters were asked to make such a decision when tasked with a referendum to determine whether the city would continue to allow hydraulic fracturing activity within its borders. For social scientists, this situation requires further analysis in an effort to better understand how and why individuals make the decisions they do. One possible approach for exploring this process is a method of poststructuralist critical rhetorical analysis, which is concerned with how individuals’ identities change through interaction with institutions. This study reflects upon the texts themselves through a poststructuralist critical rhetorical analysis of images employed by those in favor of and those against Denton’s ban on hydraulic fracturing in an attempt to identify images that alter the grid of intelligibility for the audience. The paper includes deliberation about the relative merits, subsequent disadvantages, and possible questions for further study as they relate to the theoretical implications of critical rhetorical analysis as information science. Ultimately, the study identifies poststructuralist critical rhetorical analysis as a method for solving information science problems in a way that considers closely the way identity is shaped through engagement with institutions.
47

The Biodegradability of Polypropylene Glycols and Ethoxylated Surfactants within Hydraulic Fracturing Fluids

Heyob, Katelyn M. January 2015 (has links)
No description available.
48

The potential for using energy from flared gas or renewable resources for on-site hydraulic fracturing wastewater treatment

Glazer, Yael Rebecca 18 September 2014 (has links)
The oil and gas well completion method of hydraulic fracturing faces several environmental challenges: the process is highly water-intensive; it generates a significant volume of wastewater; and it is associated with widespread flaring of co-produced natural gas. One possible solution to simultaneously mitigate these challenges is to use the energy from flared natural gas to power on-site wastewater treatment, thereby reducing 1) flared gas without application, 2) the volumes of wastewater, and 3) the volumes of freshwater that need to be procured for subsequent shale production, as the treated wastewater could be reused. In regions with minimal flaring a potential solution is to couple renewable electricity (generated from solar and wind energy) with on-site wastewater treatment, thereby 1) reducing the volumes of wastewater, 2) reducing the volumes of freshwater that need to be procured for subsequent shale production, and 3) displacing fossil fuel energy for treatment. This study builds an analytical framework for assessing the technical potential of these approaches. In this research, the hydraulic fracturing wastewater characteristics (such as quality, quantity, and flow rates) were considered along with various treatment technologies best suited to utilizing natural gas and renewable electricity, using the Permian Basin in west Texas as a geographic test bed for analysis. For the analysis looking at using flared natural gas energy for on-site treatment, the required volume of gas to meet the thermal energy requirements for treatment was calculated on a per-well basis. Additionally, the volume of product water (defined here as the treated water that can be reused) based on the technology type was determined. Finally, the theoretical maximum volume of product water that could be generated using the total volume of natural gas that was flared in Texas in 2012 as a benchmark was calculated. It was concluded that the thermal energy required to treat wastewater that returns to the surface over the first ten days after a well is completed is 140–820 Million British Thermal Units (MMBTU) and would generate 750–6,800 cubic meters of product water depending on the treatment technology. Additionally, based on the thermal technologies assessed in this study, the theoretical maximum volume of product water that can be generated statewide using the energy from the flared gas in 2012 is 180–540 million cubic meters, representing approximately 3–9% of the state’s annual water demand for municipal purposes or 1–2.4% of total statewide water demand for all purposes. This is enough gas to treat more water than was projected would be used for the entire mining sector in 2010 in Texas. For the analysis coupling renewable electricity with on-site treatment, the necessary energy for water management upstream and downstream of a well site was calculated and compared with the current energy requirements and those of a proposed strategy where a portion of the wastewater is treated on-site and reused on a subsequent well. Through this analysis, it was determined that implementing on-site treatment using renewable electricity could reduce freshwater requirements by 11–26%. Finally, it was calculated that this approach could displace approximately 16% of the fossil fuel energy requirements for pumping freshwater, trucking that water to the well site, and trucking wastewater to a disposal well. / text
49

The drill down

Friel, Katherine Dailey 14 October 2014 (has links)
The town of Millerton, Pa., has always been a small, rural farming community. Settled atop of the famed Marcellus Shale in the foothills of the Appalachians, there have always been rumors of natural gas in the hills around town. In 2008, natural gas companies arrived and began drilling. For a select few lucky enough to have property around the gas wells, their arrival means big money. But not all residents will get so lucky. For many folks in Millerton, the arrival of the gas companies means more traffic, more pollution, more crime and more inconvenience without a monthly royalty check to buffer the pain. The sheer amount of natural gas scientists predict is in the Marcellus Shale will forever change how the U.S. and the rest of the world use energy. Politicians tout it as liberation from foreign oil. Scientists see it as an alternative to “dirty” coal. For this small town, natural gas means change. The money the natural gas companies are pumping into this local economy will change the lives of the townsfolk- and the town itself- forever. / text
50

An examination of state regulations of hydraulic fracturing

Perkins, Adam Reed 14 October 2014 (has links)
As hydraulic fracturing gains popularity in the energy industry, the state of Texas finds itself in a very advantageous position. With multiple regions which could have great potential for oil and natural gas extractable via the production technique, Texas has assumed a new importance for the energy industry. However, in order to fully utilize its advantages, the state of Texas should revise its oil and gas regulations, particularly with regard to groundwater use and contamination, air emissions, and discretion for municipal regulation of oil and gas operations, insofar as they may apply to hydraulic fracturing. This course of action only will this allow the state to efficiently utilize the production method while better balancing against the technique's risks. / text

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