Natural gas is an important energy source that contributes up to 25% of the total US energy reserves (DOE 2011). An increase in natural gas demand spurs further development of unconventional resources, including methane hydrate (Rajnauth 2012). Natural gas from methane hydrate has the potential to play a major role in ensuring adequate future energy supplies in the US. The worldwide volume of gas in the hydrate state has been estimated to be approximately 1.5 x 10^16 m^3 (Makogon 1984). More than 230 gas-hydrate deposits have been discovered globally. Several production technologies have been tested; however, the development of the Messoyakha field in the west Siberian basin is the only successful commercial gas-hydrate field to date. Although the presence of gas hydrates in the Messoyakha field was not a certainty, this current study determined the undeniable presence of gas hydrates in the reservoir. This study uses four models of the Messoyakha field structure and reservoir conditions and examines them based on the available geologic and engineering data. CMG STARS and IMEX software packages were used to calculate gas production from a hydrate-bearing formation on a field scale. Results of this analysis confirm the presence of gas hydrates in the Messoyakha field and also determine the volume of hydrates in place. The cumulative production from the field on January 1, 2012 is 12.9 x 10^9 m^3, and it was determined in this study that 5.4 x 10^9 m^3 was obtained from hydrates. The important issue of pressure-support mechanisms in developing a gas hydrate reservoir was also addressed in this study. Pressure-support mechanisms were investigated using different evaluation methods such as the use of gas-injection well patterns and gas/water injection using isothermal and non-isothermal simulators. Several aquifer models were examined. Simulation results showed that pressure support due to aquifer activity was not possible. Furthermore, it was shown that the water obtained from hydrates was not produced and remained in the reservoir. Results obtained from the aquifer models were confirmed by the actual water production from the field. It was shown that water from hydrates is a very strong pressure-support mechanism. Water not only remained in the reservoir, but it formed a thick water-saturated layer between the free-gas and gas-hydrate zone. Finally, thermodynamic behavior of gas hydrate decomposition was studied. Possible areas of hydrate preservation were determined. It was shown that the central top portion of the field preserved most of hydrates due to temperature reduction of hydrate decomposition.

The sedimentary wedge of the northern Gulf of Mexico is extensively deformed and faulted by salt tectonics. Industry 2-D multichannel seismic data covering a large area (33,800 km2) of the lower Texas continental slope [96 degrees 40'- 93 degrees 40'W; 27 degrees 10N - 26 degrees N] were examined to evaluate the interplay of salt, faults and gas. Seismic interpretation revealed the study area has two different styles of faulting and two different types of salt bodies that vary east to west. The eastern region of the study area has a thin sedimentary section and a massive, nearly continuous salt sheet characterized by minibasins and local salt highs. Faulting in this area appears to be the result of salt tectonism. The western region of the study area has a thick sedimentary wedge, and a few isolated salt diapirs. Long, linear faults are parallel to slope and imply some degree of gravitation sliding. The difference in faulting styles and salt bodies can be attributed to different depositional environments, different styles and amounts of sediment loading and different amounts of salt initially deposited. While there is a widespread occurrence of gas throughout the study area, little evidence of continuous bottom simulating reflectors (BSRs), a widely accepted geophysical indicator of gas hydrate, has been found. The gas hydrate stability zone (GHSZ) was modeled to provide information on the thickness and variability of the stability zone, and provide a baseline in a search for BSRs. The dataset was analyzed for multiple seismic expressions of BSRs, however only a few small and isolated examples were found. Potential fluid escape structures were seen in the seismic data. Despite the great number of potential features found in the seismic data only seven active seeps were found in a seep study by I. R. MacDonald. Seeps were seen in far less abundance than the number of seeps found offshore Louisiana. This may imply a lack of source offshore Texas.

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.

A gas hydrate refers to the state in which hydrogen-bonded water molecules form a rigid lattice structure of so-called "cages", wherein "guest" molecules of natural gas are entrapped. Not unlike ice, gas hydrates are prone to form at low temperatures and high pressures; however, their crystalline structure allows them to remain stable at temperatures and pressures under which the phase limits of ice would otherwise be exceeded. To date, a number of instances of gas hydrates forming in the subsurface of Arctic climates below layers of permafrost have been identified, however the challenge of identifying past occurrences of methane hydrates during episodes of global cooling and glacial advance remains relatively unmet. During these periods of glacial/permafrost cover, the presence of hydrates could have a significant impact on the groundwater flow system due to the significant reduction of the porosity and permeability of hydrate saturated sediments. The purpose of this study is to investigate whether there is evidence to suggest that methane hydrates could have formed in the sedimentary units of the Michigan Basin at the Bruce nuclear site near Kincardine, Ontario, particularly when subjected to the impacts of glacial ice sheet loading. This study aims to provide insight into whether the potential impact of gas hydrates should be considered in the design of the proposed deep-geologic repository (DGR) for low- and intermediate-level nuclear waste. This study presents a framework employing regional-scale numerical modelling to estimate the evolution of temperature, pressure and salinity profiles across the study area, combined with thermodynamic predictive modelling to identify potential paleo-methane hydrate stability zones in the subsurface at the Bruce nuclear site. This study represents the first step to ultimately assess the extent of paleo-methane hydrates and their impact on subsurface conditions at the site. Transient subsurface conditions at the Bruce nuclear site were modelled over a period of 120,000 years (120 ka), encompassing episodes of glacial advance and retreat during the Pleistocene epoch. The spatial and transient outputs from numerical modelling of the study area were then used as inputs to thermodynamic predictive modelling of methane hydrate stability. The results of this study show that, based upon the subsurface temperature, pressure and salinity histories determined using a three-dimensional regional-scale numerical modelling approach, paleo-conditions at the Bruce nuclear site become conducive with methane hydrate stability during the study period. Two separate episodes of methane hydrate stability were identified - lasting from 62.5 to 56 thousand years before present (kaBP) and from 23 to 13.5 kaBP, respectively - which were found to correspond to periods of glacial advance across the study area. The vertical extent of the estimated hydrate stability zones varied across the site, however it generally followed the limits of the Upper Silurian units, penetrating to deeper elevations towards the south west end of the study area.

A gas hydrate refers to the state in which hydrogen-bonded water molecules form a rigid lattice structure of so-called "cages", wherein "guest" molecules of natural gas are entrapped. Not unlike ice, gas hydrates are prone to form at low temperatures and high pressures; however, their crystalline structure allows them to remain stable at temperatures and pressures under which the phase limits of ice would otherwise be exceeded. To date, a number of instances of gas hydrates forming in the subsurface of Arctic climates below layers of permafrost have been identified, however the challenge of identifying past occurrences of methane hydrates during episodes of global cooling and glacial advance remains relatively unmet. During these periods of glacial/permafrost cover, the presence of hydrates could have a significant impact on the groundwater flow system due to the significant reduction of the porosity and permeability of hydrate saturated sediments. The purpose of this study is to investigate whether there is evidence to suggest that methane hydrates could have formed in the sedimentary units of the Michigan Basin at the Bruce nuclear site near Kincardine, Ontario, particularly when subjected to the impacts of glacial ice sheet loading. This study aims to provide insight into whether the potential impact of gas hydrates should be considered in the design of the proposed deep-geologic repository (DGR) for low- and intermediate-level nuclear waste. This study presents a framework employing regional-scale numerical modelling to estimate the evolution of temperature, pressure and salinity profiles across the study area, combined with thermodynamic predictive modelling to identify potential paleo-methane hydrate stability zones in the subsurface at the Bruce nuclear site. This study represents the first step to ultimately assess the extent of paleo-methane hydrates and their impact on subsurface conditions at the site. Transient subsurface conditions at the Bruce nuclear site were modelled over a period of 120,000 years (120 ka), encompassing episodes of glacial advance and retreat during the Pleistocene epoch. The spatial and transient outputs from numerical modelling of the study area were then used as inputs to thermodynamic predictive modelling of methane hydrate stability. The results of this study show that, based upon the subsurface temperature, pressure and salinity histories determined using a three-dimensional regional-scale numerical modelling approach, paleo-conditions at the Bruce nuclear site become conducive with methane hydrate stability during the study period. Two separate episodes of methane hydrate stability were identified - lasting from 62.5 to 56 thousand years before present (kaBP) and from 23 to 13.5 kaBP, respectively - which were found to correspond to periods of glacial advance across the study area. The vertical extent of the estimated hydrate stability zones varied across the site, however it generally followed the limits of the Upper Silurian units, penetrating to deeper elevations towards the south west end of the study area.

An isobaric flow loop added to the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) is being investigated as a means of rapidly forming methane hydrate in watersaturated sand from methane dissolved in water. Water circulates through a relatively warm source chamber, dissolving granular methane hydrate that was pre-made from seed ice, then enters a colder hydrate growth chamber where hydrate can precipitate in a water-saturated sand pack. Hydrate dissolution in the source chamber imparts a known methane concentration to the circulating water, and hydrate particles from the source chamber entrained in the circulating water can become nucleation sites to hasten the onset of hydrate formation in the growth chamber. Initial results suggest hydrate grows rapidly near the growth chamber inlet. Techniques for establishing homogeneous hydrate formation throughout the sand pack are being developed.

This dissertation investigates the nature of submarine landslides along the deformation front of the northern Cascadia subduction zone. As the first slope stability analysis on the west coast of Vancouver Island, this study covers a variety of large-scale tectonic to small-scale, site-specific factors to investigate the nature of slope failure. Slope failure occurred mainly on the steep slopes of frontal ridges that were formed by compressive forces due to the subduction of the Juan de Fuca plate. Multi-beam swath bathymetry data are used to study the morphology of the whole margin and the geometry of two Holocene landslides that serve as representative examples. The overall margin stability is estimated using the critical taper theory, and a first-order limit equilibrium slope stability analysis provides threshold values for external forces to cause slope failure. The present-day pore pressure regime at different sites of the Cascadia margin is estimated from log-density data and expected ground accelerations are calculated via ground motion attenuation relationships. A comparison to threshold values derived from the limit equilibrium analysis suggests that, at present, slope stability is more sensitive to overpressure than to earthquake shaking. Differences in power spectral density derived from OBS-velocity data imply a slightly amplified ground response at the ridge crest compared to sites along the continental shelf and abyssal plain. Apart from estimating the trigger mechanisms of submarine landslides offshore Vancouver Island, a particular consideration is given to the potential link between slope failure and methane hydrate occurrence. The history of the gas hydrate stability zone (GHSZ) boundaries is investigated using information on regional sea-level history. Assuming colder ocean-bottom temperatures during the Holocene, a gradual shoaling of the BSR is inferred, which potentially could have caused hydrate melting. Pore pressure due to hydrate dissociation, as estimated by a previously developed method, varies over several orders of magnitude. Depending on sediment permeability, overpressure ratios can be comparable to threshold values. The two Holocene landslides are modeled numerically using a two-dimensional finite difference code in order to recreate the along-strike variability in ridge geometry and slide morphology observed along the northern Cascadia margin. Geometry and morphology correlate with the two prevalent slide mechanisms and model results suggest that sediment yield strength and average slide thickness are associated with the slide mechanism as well. / Graduate / 0373 / nscholz@uvic.ca

Ice recrystallization during cryopreservation results in cell death and decreased cell viabilities due to cellular damage. This is a significant problem particularly in regenerative medicine where decreased cell viabilities post-thaw affect the success of the therapy. Given the success of these therapies to treat various diseases, the development of novel cryprotectants which have the ability to inhibit ice recrystallization during freezing and thawing are urgently required. Current cryoprotectant such as dimethyl sulfoxide, is associated with cytotoxicity in the clinical settings and thus are not optimal cryoprotectants. Our laboratory is interested in the rational synthesis of non-cytotoxic small molecules which possess the property of ice recrystallization inhibition (IRI) activity. Previously, the Ben laboratory has demonstrated that simple monosaccharides possess moderate ice recrystallization inhibition activity and that this activity is linked to hydration. The “compatibility” of the carbohydrate within the three-dimensional hydrogen bonded network of water is inversely proportional to its IRI activity. Hydration has previously been directly linked to the stereochemical relationship of individual hydroxyl groups on the carbohydrate. Additionally, it has been proposed that intramolecular hydrogen bond formation and hydrogen bonding cooperativity has a large effect on the water structure thus impacting hydration. Structure-function work has suggested that the presence of an amine as a hydrogen donor at the endocyclic position within the pyranose ring maybe beneficial to IRI activity. Thus, the first part of this thesis describes the synthesis and IRI activity of D-glucose and D-galactose based azasugars and its analogues. These azasugars have replaced the endocyclic ring oxygen with an amine. These azasugars and their analogues were found to possess moderate to potent IRI activity suggesting that hydrogen bond donation may be important for hydration and thus, IRI activity at the endocyclic ring oxygen. During the development of these azasugars, the Ben laboratory developed carbohydrate-based surfactants and hydrogelators possessing unprecedented IRI activity. A potential use of molecules possessing IRI activity is towards the inhibition of gas hydrate formation. Gas hydrates are ice-like solids containing gases within a highly ordered network of water molecules. These gas hydrates tend to accumulate in oil and gas pipelines posing significant dangers as the build-up of solid material leads to blockages in the pipeline reducing flow. Previous work had demonstrated the use of antifreeze proteins possessing potent IRI activity in inhibiting gas hydrate formation. However, their complex structure limits commercial use. Thus, the second part of the thesis describes the use of the azasugars, carbohydrate-based surfactants and hydrogelators in inhibiting gas hydrate formation. The effectiveness of the small molecules is compared to a commercial inhibitor PVP 10. Some of these small molecules were significantly better inhibitors of gas hydrate formation than the currently utilized inhibitor PVP 10. The low molecular weights of these small molecules, easy synthesis and potency make them excellent alternatives to PVP 10. However it was found that while some of the structural features in the small molecules may be amenable to both activities, it seems that the ability to inhibit ice recrystallization is not a good indicator of a compounds ability to inhibit gas hydrate formation. In a continuing effort to develop novel small molecule IRIs, the Ben laboratory has develop three classes of compounds. These include: carbohydrate-based surfactants and hydrogelators, lysine-based surfactants and truncated C-linked glycopeptides. Structure-function work utilizing these compounds revealed that presence of long alkyl chains, an amide linkage and the presence of an open-alditol chain are all important to IRI activity. However, the surfactant-like nature limits their use in cryopreservation and thus prompted the discovery of phenoxyglycosides as IRI active molecules. The structural features of these recently developed small molecules were combined to generate novel small molecule IRIs which do not resemble surfactants. These novel small molecules included “disaccharides” which possessed an aryl group at the anomeric position of a pyranose ring and an open-alditol chain linked via an amide bond. Additionally, N-cycloalkyl-D-aldonamides and N-phenyl-D-aldonamides were also synthesized. Of these novel small molecules, two very potent IRI active molecules were discovered: a “disaccharide” possessing an aryl group at the anomeric position with the open-alditol chain of D-galactose linked via an amide bond at C3 and N-phenyl-D-arbonamide. Both of these small molecules were assessed for their ability to cryopreserve hematopoietic stem cells. Unfortunately, the additional of these compounds failed to improved percent cell viabilities as compared to DMSO.

Kinetics of hydrate formation and decomposition of methane hydrate formed in silica sand particles were studied in detail at three temperatures of 7.0, 4.0 and 1.0°C, respectively. A new apparatus was setup to study the decomposition behavior of the methane hydrate formed in the bed of silica sand particles. Six thermocouples are placed in different locations to study the temperature profiles during hydrate formation and decomposition experiments. Gas uptake measurement curves for the formation experiments and the gas release measurement curves for the decomposition experiment were determined from the experimental data. Percent conversion of water to hydrates was significantly higher for the experiments conducted at 4.0 and 1.0°C compared to 7.0°C. Recovery of methane occurred in two stages during the decomposition experiments carried out with a thermal stimulation approach at constant pressure. Methane recovery in the range of 95 to 98% was achieved.

In the present study the effect of one commercially available anionic surfactant on the formation/dissociation of hydrate from a gas mixture of 90.5 % methane – 9.5% propane mixture was investigated. Surfactants are known to increase gas hydrate formation rate. Memory water was used and the experiments were carried out at three different degrees of undercooling and two different surfactant concentrations. In addition, the effect of the surfactant on storage capacity of gas into hydrate was assessed. The morphology of the growing crystals and the gas consumption were observed during the experiments. The results show that branches of porous fibre-like crystals are formed instead of dendritic crystals in the absence of any additive. Finally, the addition of 2200 ppm of SDS was found to increase the mole consumption for hydrate formation by 4.4 times.