Thesis (M.C.E.)--University of Delaware, 2006. / Principal faculty advisor: Dov Leshchinsky, Dept. of Civil and Environmental Engineering. Includes bibliographical references.

The cleat permeability of coal, a key to the success of any coalbed methane (CBM) recovery operation, is a dynamic parameter impacted by changes in effective stress and desorption-induced "matrix shrinkage". Most commonly-used theoretical models developed to predict CBM production as a result of permeability changes are based on the assumption that the deformation of a depleting coalbed is limited to the vertical direction; that is, the coal is under uniaxial strain conditions. However, most laboratory studies completed to estimate the changes in coal permeability have used triaxial state of stress, thus violating the underlying principles of the models. An experimental study was, therefore, undertaken to estimate the permeability variation of coal with a decrease in pore pressure under replicated in situ conditions where flow through coal, held under uniaxial strain conditions, was measured. Three samples were tested, one from the San Juan basin and the other two from the Illinois basin. The experimental results showed that, under uniaxial strain conditions, decreasing pore pressure resulted in a significant decrease in horizontal stress and increased permeability. The permeability increased non-linearly with decreasing pore pressure, with a small increase in the high pressure range, which increased progressively as the pressure dropped below a certain value. The experimental results were used to validate two theoretical models, namely the Palmer and Mansoori and Shi and Durucan, commonly used to project permeability variation with continued production. The models failed to provide good agreement with the experimental results below 300 psi, suggesting a shortcoming in the modeling philosophy. Although the measured permeability and stress changes were in qualitative agreement with the modeling results, both models predicted negative horizontal stresses at low pore pressures for one coal type, which was not supported by experimental results. The sorption-induced strain was also found to be significantly higher in the low pore pressure range, clearly suggesting a direct relationship between the sorption-induced strain and permeability. Moreover, the increase in permeability was different for the three coal types tested, with the largest increase for the core taken from maximum depth. Finally, a gradual increase in the logarithm of permeability was measured with reduction in horizontal stress. These results suggest a distinct advantage for deeper coals, which have generated limited interest to date, primarily due to the low initial permeability. Extending the deformation of a cylindrical rock sample loaded axially, a hypothesis was developed where coal undergoes maximum deformation at the middle of its length. Using this hypothesis, permeability variation with decreasing pore pressure was estimated and the established trend was used to modify one of the existing models. The agreement between laboratory results and the modified model showed definite promise for improving permeability projection capability.

LKAB and Trafikverket want to increase the maximum allowed axial load from 30 tons to 32,5 tons for the northern part of Malmbanan. There are ongoing investigations of the condition of the railway with the current axial load of 30 tons. The investigations do not include one of Trafikverket's concerns about the condition of the railway. That question is how the periodical load from trains affect the stability and maintenance cost of the railway embankment. The aim of this thesis is therefore to do a preliminary investigation of how the excess pore pressure is developed in the railway embankment during periodical loading and an attempt to model it the help of PLAXIS2D, a finite element software. PLAXIS2D has been used to model a simplified section of section km 1449+820 that is subjected by periodical loading with an axial load of 30 tons. There are 6 created models in the thesis where model 2-6 origin from model 1 but with some minor changes. The changes between the models are the train speed, groundwater level, width of the embankment and load. The periodical load applied in all models has been assumed to load the embankment with a periodical shape of a sinus curve. From the models, the distribution of the effective stress and excess pore pressure have been measured. The total displacement and the magnitude of excess pore pressure in different measuring points in the embankment have also been measured. These results have been used to analyze why there are certain points in the embankment which accumulate excess pore pressure. In the models, measuring points have also been created beneath the sleeper and in the embankment toe where total displacement and effective stress have been measured to relate and see if the response in stress and displacements are trustworthy. It was concluded that accumulation of excess pore pressure is relative high in the embankment toe due to the stress distribution and slope stability. The embankment is developing large shear stresses in the embankment toe to resist against slope failure. The excess pore pressure is recommended to be measured in the embankment toe, but it is also recommended to develop the model further since it does not consider any dynamics and neither soil stiffening or soil softening which limit the possibility to analyze liquefaction in detail.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15393号 / 工博第3272号 / 新制||工||1493(附属図書館) / 27871 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 井上 正志, 教授 江口 浩一, 教授 大江 浩一 / 学位規則第4条第1項該当

Masters of Science / The Bredasdorp basin is situated off the south coast of the Republic of South Africa, southeast of Cape Town and west-south-west of Port Elizabeth. It covers approximately 18,000 sq. km beneath the Indian Ocean along the southern coast of South Africa, which is in the southwest of Mosselbay. Bredasdorp basin contains South Africa’s only oil and gas production facilities and has been the main focus for oil and gas exploration in South Africa. It is one of the largest hydrocarbon producing block in South Africa, rich in gas and oil prone marine source rocks of kimmeridgian to berriasian age. The wells of interest for this study are located within block 9 which is made up of 13 wells but for this study the focus is only on 3 wells, which are well F-01,F-02 and F-03. The goal of this study is to predict as accurately as possible the areas within and around the sandstone reservoir intervals of these wells with abnormal pressure, using well logs and production test data. Abnormal pore pressure which is a major problem for drillers in the oil industry can cause serious drilling incidents and increase greatly drilling non-production time if the abnormal pressures are not predicted accurately before and while drilling. Petrophysics log analysis was done to evaluate the reservoirs. The intervals of the reservoir are the area of interest.Pore pressure gradient, fracture gradient, pore pressure and fracture pressure model were run. Pressures of about 6078.8psi were predicted around the zone of interest in well F-01, 7861 psi for well F-02 and 8330psi for well F-03. Well F-03 was the most pressured of the three wells. Abnormal pressures were identified mostly at zones above and below the area of interest and predicted pressure values were compared to actual pressure values to check for accuracy.

This study presents the synthesis of polymers of intrinsic microporosity and the investigation of their microporosity using gas sorption and adsorption of liquids and vapours. Microporous polymeric materials PIM-1, TAPIM-1, PIM-2 and PIM-7 were synthesised using step-growth polymerisation. The microporosity of these materials was studied using gas sorption and adsorption of molecules in the liquid phase. A procedure to validate gas sorption methods was undertaken before being used to characterise microporous materials. The sorption methodology was validated using standard reference materials (SRMs) and collaborative testing, and the PSD evaluation was validated using a well defined crystalline material. Different approaches to obtaining pore size distribution (PSD) data were dealt with. Gas sorption methods that use CO2 at 273 K and at 303 K, N2 at 77 K, H2 at77 K, and Xe (298 K) to determine PSD were compared. The Horvath-Kawazoe(HK) model was presented as the preferred model and the N2, CO2 and H2 sorption data were treated under this approach. CO2 PSD data at 273 K and at303 K was compared against N2 PSD data and a novel complementary relationship established. PIM-1 samples in film form and powder form were used to investigate the effect of sample form on the sorption properties of the material. PIM-1, PIM-2, TAPIM-1, ethano-anthracene PIM-1 copolymers, and triptycene based PIMs were used to investigate the influence of polymer structure on gas sorption properties. The free volume properties of a PIM-1 ethano-anthracene copolymer (PIM-CO1-40), was compared against PIM-1. A number of independent techniques, namely N2 sorption, Xe sorption, Positron annihilation lifetime spectroscopy (PALS), and 129Xe NMR were used to probe the free volume. The time dependence of free volume and its bearing on diffusivity of PIM-1 membranes was investigated. Water, chloroform and simple alcohols were used to investigate adsorption in the liquid and vapour phases. Interaction with PIM-1 the aromatic ether linkage and the nitrile group produced frequency shifts in ATR-FT-IR spectra. These frequency shifts were used to compare relative strengths of the hydrogen bonds.

It goes without saying that water scarcity is a widespread and increasingly pressing global challenge. One of the methods which can mitigate water shortage is to increase freshwater production via desalination of saline waters. Seawater and saline aquifer sources represent 97.5% of all water on Earth. Hence, treating even a small portion of saline water could significantly reduce water shortage. Although reverse osmosis is one of the state-of-the-art pressure-driven membrane desalination technologies, it is incapable of desalinating high-salinity streams due to the very high osmotic pressure to overcome. Membrane distillation (MD) is one of the emerging methods, which has attracted much attention for desalinating highly saline brines. MD is a thermally driven process in which only vapor molecules pass through the pores of a microporous hydrophobic membrane. This process, however, has not been fully commercialized due to a number of challenges, including “pore wetting”. Pore wetting refers to the presence of liquid, instead of just water vapor, inside the membrane pores, which may cause a decrease in MD flux and/or deterioration of distillate quality. Herein, a comprehensive review on pore wetting is presented, and then this phenomenon is investigated from four aspects. In the first phase of this project, a theoretical model is presented according to which the pore size distribution of membrane, a parameter affecting pore wetting risk, is estimated by employing only a few experimental data points in accordance with the wet/dry method, reducing the number of data required to be recorded largely. In the next phase, an equation is presented for the estimation of liquid entry pressure (LEP), a membrane parameter closely related to pore wetting, using computational fluid dynamics (CFD) tools and genetic programming (GP) as an intelligent technique. This equation can estimate LEP in closer agreement to experimental values in comparison to the Young-Laplace equation. In the third phase, movement of liquid-gas interface inside the membrane pore is tracked using a well-founded model, and consequently, the pressure and velocity at the interface and the required time for replacement are studied. Finally, in the last phase, a model is developed for pore wetting in vacuum MD, considering heat and mass balances at the vapor-liquid interface. This model assumes that heat only enters the pore inlet and is removed due to liquid vaporization at the vapor-liquid interface, with heat transfer through the pore wall neglected. This model shows that partial pore wetting is possible since the vapor-liquid interface might remain within the pore at the steady-state condition. Further, this model can predict the decrease in temperature from the pore inlet to the vapor-liquid interface, a phenomenon that has been reported in the literature without any proof.

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