Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 67 p. : ill. (some col.), col. map. Includes abstract. Includes bibliographical references (p. 64-67).

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Gas hydrates are molecular host-guest mixtures where guest gas species are encapsulated in host water networks. They play an important role in gas storage in aqueous environments at relatively low pressures, and their stabilities are determined by weak interactions of the guest species with their respective host water frameworks. Thus, the size and the amount of the guest species vary, depending on the size of the empty space provided by the host water structures. The systems studied here are noble gas (He, Ne, Ar) and diatomic (H2) hydrates. Because of the similarity of the guests' sizes between the noble gases and the di-atomic gases, the noble gas hydrates act as simple models for the di-atomic gas hydrates. For example, He, Ne and H2 have approximately the same size. Density functional theory calculations are used to obtain the ground state formation enthalpies of each gas hydrate, as a function of host network, guest stoichiometry, and pressure. Dispersion effects are investigated by comparing various dispersion corrections in the exchange-correlation functionals (semi-local PBE, semi-empirical D2 pair correction, and non-local density functionals i.e. vdW-DF family). Results show that the predicted stability ranges of various phases agree qualitatively, although having quantitative difference, irrespective of the methods of the dispersion corrections in the exchange-correlation functionals. Additionally, it is shown in gas-water dimer interaction calculations that all DFT dispersion-corrected functionals overbind significantly than the interaction acquired by the coupled-cluster calculations, at the CCSD(T) level, which is commonly accepted to provide the most accurate estimation of the actual interaction energy. This could lead to an overestimation of the stability of the hydrate mixtures. Further study in the gas-water cluster indicates that less overbinding effect is found in the cluster than in the dimer. This implies that the overbinding energy caused by DFT might become less pronounce in the solid phase. Graph invariant topology and a program based on a graph theory are used to assign protons based on the 'ice rule' to fulfill the incomplete experimental structural data such as unknown/unclear positions of protons in the host water lattices. These methods help constructing host water networks for computational calculations. Several configurations of the host water structures are tested. Those configurations having lowest enthalpies are used as the host water networks in this research. Furthermore, the enthalpic spread between the configurations having the highest and the lowest enthalpy in the pure water ice network is very small (about 10 meV per water molecule). Nevertheless, it is still unclear to conclude that this protonic effect is also trivial in the gas-water compound. Therefore, this study also calculates the enthalpies of the gas-water mixtures having various proton configurations in the host water networks. Results indicate that very small enthalpic distributions among the proton configurations are found in the compounds as well. Furthermore, the enthalpic spread is almost constant as pressure increases. This suggests there is no pressure effect in the enthalpy gap amoung the proton distributions in both pure water ice and the gas-water compounds. Predicted stable phases for the noble gas compound systems are based on four host water networks, namely, ice Ih, II and Ic, and the novel host water network S!. The He-water system adopts ice Ih, II and Ic network upon increasing pressure. In the Ne-water system, a phase sequence of Sx/ice-Ih, II and Ic with a competitive hydrate phase in the S! host network at very low pressure is found. This is similar to the phase evolution of the H2-water system. For the Ar-water mixture, only a partially occupied hydrate in the Sx host network is found stable. This Sx phase becomes metastable if taking the traditional clathrates (sI and sII) into account. This result agrees very well with the experiment suggesting only two-third filling is found the large guest gases i.e. CO2. For the diatomic guest gas compound systems, the traditional clathrate structure (sII) that found to be existed experimentally in the H2-H2O system is also included in this study together with those four host water networks. Predicted phase stability sequence as elevated pressure is as follows: Sx, ice-Ih, II and Ic. This computationally prediction agrees very well with experiment. Results in this work suggest that the compound based on the traditional clathrate structure II (sII) host water framework is found to be metastable with respect to the decomposition constituents - in this case, they are pure water ice and the S!. The metastability of the hydrogen hydrates based on the sII structure might due to zero-point motions or other dynamic/entropic mechanisms uncovered in this research. Dynamic studies concerning the transition states of the hydrogen guest molecules in three competitive phases at very low pressure (less than 10 kbar), based on Sx, ice-Ih, and ice-II host water network, are considered. The energy barriers required by the hydrogen guest molecules in those three host frameworks are calculated by using Nudged Elastic Band (NEB) method. Results suggest that the hydrogen molecules are more mobile in the Sx than the other two host structures significantly. In the S! host water network, the energy barrier is about 25 meV/hydrogen molecule. This energy is about the room temperature suggesting that the hydrogen guest molecules are easily mobile in the Sx host water network if there is an empty site adjacent to them.

As hydrocarbon exploration and development moves into deeper water and onshore arctic environments, it becomes increasingly important to quantify the drilling hazards posed by gas hydrates. To address these concerns, a 1D semi-analytical model for heat and fluid transport in the reservoir was coupled with a numerical model for temperature distribution along the wellbore. This combination allowed the estimation of the dimensions of the hydratebearing layer where the initial pressure and temperature can dynamically change while drilling. These dimensions were then used to build a numerical reservoir model for the simulation of the dissociation of gas hydrate in the layer. The bottomhole pressure (BHP) and formation properties used in this workflow were based on a real field case. The results provide an understanding of the effects of drilling through hydratebearing sediments and of the impact of drilling fluid temperature and BHP on changes in temperature and pore pressure within the surrounding sediments. It was found that the amount of gas hydrate that can dissociate will depend significantly on both initial formation characteristics and bottomhole conditions, namely mud temperature and pressure. The procedure outlined suggested in this work can provide quantitative results of the impact of hydrate dissociation on wellbore stability, which can help better design drilling muds for ultra deep water operations.

This article provides a comprehensive reference list to the extensive studies of marine natural gas hydrate surveys and studies on the northern Cascadian margin of Western Canada. The references are divided into each of the major study methods, surveys, analyses and conclusions. A number of MSc and PhD theses are included. We first refer to the articles that address the local tectonics and sedimentary accretionary prism in which the hydrate forms, then those that describe the numerous geophysical and geological surveys and studies, and finally the articles that address the most important conclusions that have resulted from this work on the distribution , concentrations, and amounts of hydrates, and on the processes of hydrate formation and dissociation.

The oil and gas industry is often plagued by the formation of clathrate hydrates in oil pipelines. While the industry originally had a heuristic of avoidance of clathrate hydrates they are moving to a heuristic of risk management. To successfully implement a risk management heuristic, time dependent phenomena of clathrate hydrate formation and flowline plugging must be known. The study of time dependent phenomena of formation and agglomeration are investigated using a TA Instruments AR-G2 rheometer with a pressure cell capable of operating at up to 13.8 MPa. Pressurized rheological experiments examine clathrate hydrates formed in situ. Both shear and oscillatory experiments have been conducted on the samples, giving flow and viscoelastic parameters. Shear experiments show sharp increases in viscosity upon clathrate hydrate formation indicating rapid aggregation. Transient oscillation experiments show a sharp increase in the elastic and loss moduli followed by a decrease in the loss moduli. Thus, both in situ clathrate hydrate formation and annealing are quantified. In addition these oscillatory measurements provided a novel technique for non-destructive investigation of clathrate hydrate aggregation over time.