This thesis explores two ways of developing a fracture diagnostics tool capable of estimating hydraulic fracture propped length and orientation. Both approaches make use of an electrically conductive proppant. The fabrication of an electrically conductive proppant is believed to be possible and an option currently on the market is calcined petroleum coke. The first approach for tool development was based on principles of antenna resonance whereas the second approach was based on low frequency magnetic induction. The former approach had limited success due to the lack of resonant features at the stipulated operating conditions. Low frequency induction is a more promising approach as electromagnetic fields showed measurable changes that were dependent on fracture length in simulations. The operation of a logging tool was simulated and the data showed differences in the magnetic field magnitude ranging from 2% to 107% between fracture sizes of 20m, 50m, 80m, and 100m. Continuing research of the topic should focus not only on simulating more diverse fracture scenarios but also on developing an inversion scheme necessary for interpreting field data. / text

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.

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.

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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

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

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

This analysis focused primarily on three main treatment methods which were re-use, recycle, and disposal wells. The re-use treatment option is when wastewater is mixed with source water in order to meet fracturing water requirements. With this option, the hope is that the wastewater for re-use will require little or no treatment at all. The second treatment option is the recycle option. This option provides high quality water for re-use or discharge to the environment using a recycling technology. The credibility of this option is heavily dependent on its ability to recycle almost all of the wastewater with little or none left for disposal or treatment. The third option is well disposal. This entails disposing all of the wastewater into a deep formation. The software used for building the model is called @Risk. The model’s costs were estimates from recent research to capture the risks and uncertainties associated with wastewater disposal. The model revealed that re-use option remains the most cost effective treatment method to reduce overall water management cost in the Marcellus. The re-use option is most viable when a hydraulic fracturing schedule is continuous (no significant storage requirement) and infrastructure is available to transport wastewater from one fracturing operation to the other. The recycle option is the second most viable disposal option. This option is most effective when the hydraulic fracturing schedule is staggered in both time and distance because distilled water from recycling facilities can be easily discharged into the environment or stored. The most unfavorable option for wastewater management at the Marcellus is the well disposal option due to the high cost of trucking wastewater to disposal wells in neighboring states or counties. It also requires the highest usage of fresh water. A well disposal option can be favorable at the onset of a hydraulic fracturing schedule when there are low levels of infrastructure, hydraulic fracturing programs are not continuous or localized in proximity, and the volume of wastewater does not exceed the capacity for injection. In this case, disposal wells can be more favorable than recycle or re-use if they are in close proximity to drilling sites. / text

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa, in fulfilment of the requirements for the degree of Doctor of Philosophy, 2013. / The aim of the thesis is to derive group invariant, exact, approximate analytical and numerical solutions for a two-dimensional laminar, non-Newtonian pre-existing hydraulic fracture propagating in impermeable and permeable elastic media. The fracture is driven by the injection of an incompressible, viscous non-Newtonian fluid of power law rheology in which the fluid viscosity depends on the magnitude of the shear rate and on the power law index n > 0. By the application of lubrication theory, a nonlinear diffusion equation relating the half-width of the fracture to the fluid pressure is obtained. When the interface is permeable the nonlinear diffusion equation has a leak-off velocity sink term. The half-width of the fracture and the net fluid pressure are linearly related through the PKN approximation. A condition, in the form of a first order partial differential equation for the leak-off velocity, is obtained for the nonlinear diffusion equation to have Lie point symmetries. The general form of the leak-off velocity is derived. Using the Lie point symmetries the problem is reduced to a boundary value problem for a second order ordinary differential equation. The leak-off velocity is further specified by assuming that it is proportional to the fracture half-width. Only fluid injection at the fracture entry is considered. This is the case of practical importance in industry. Two exact analytical solutions are derived. In the first solution there is no fluid injection at the fracture entry while in the second solution the fluid velocity averaged over the width of the fracture is constant along the length of the fracture. For other working conditions at the fracture entry the problem is solved numerically by transforming the boundary value problem to a pair of initial value problems. The numerical solution is matched to the asymptotic solution at the fracture tip. Since the fracture is thin the fluid velocity averaged over the width of the fracture is considered. For the two analytical solutions the ratio of the averaged fluid velocity to the velocity of the fracture tip varies linearly along the fracture. For other working conditions the variation is approximately linear. Using this observation approximate analytical solutions are derived for the fracture half-width. The approximate analytical solutions are compared with the numerical solutions and found to be accurate over a wide range of values of the power-law index n and leak-off parameter β. The conservation laws for the nonlinear diffusion equation are investigated. When there is fluid leak-off conservation laws of two kinds are found which depend in which component of the conserved vector the leak-off term is included. For a Newtonian fluid two conservation laws of each kind are found. For a non-Newtonian fluid the second conservation law does not exist. The behaviour of the solutions for shear thinning, Newtonian and shear thickening fluids are qualitatively similar. The characteristic time depends on the properties of the fluid which gives quantitative differences in the solution for shear thinning, Newtonian and shear thickening fluids.

A dissertation submitted to the Faculty of Science,University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science. December 2016. / This research is concerned with the analysis of a two-dimensional Newtonian fluid-driven fracture in a permeable rock. The fluid flow in the fracture is laminar and the fracture is driven by the injection of a Newtonian fluid into it. Most of the problems in litera- ture involving fluid flow in permeable rock formation have been modeled with the use of Darcy's law. It is however known that Darcy's model breaks down for flows involv- ing high fluid velocity, such as the flow in a porous rock formation during hydraulic fracturing. The Forchheimer flow model is used to describe the non-Darcy fluid flow in the porous medium. The objective of this study is to investigate the problem of a fluid-driven fracture in a porous medium such that the flow in the porous medium is non-Darcy. Lubrication theory is applied to the system of partial di erential equations since the fracture that is considered is thin and its width slowly varies along its length. For this same reason, Perkins-Kern-Nordgren approximation is adopted. The theory of Lie group analysis of differential equations is used to solve the nonlinear coupled sys- tem of partial differential equations to obtain group invariant solutions for the fracture half-width, leak-o depth and length of the fracture. The strength of fluid leak-off at the fracture wall is classi ed into three forms, namely, weak, strong and moderate. A group invariant solution of the traveling wave form is obtained and an exact solution for the case in which there is weak fluid leak-off at the interface is found. A dimensionless parameter, F0, termed the Forchheimer number was obtained and investigated. Nu- merical results are obtained for both the case of Darcy and non-Darcy flow. Computer generated graphs are used to illustrate the analytical and numerical results. / MT2017