There has been a dramatic increase in both the amount and type of geophysical well log data acquired in gas hydrate saturated rocks. Data has been acquired in both offshore and Arctic environments; its availability has shed light on the applicability of current tools and the potential usefulness of recently developed and developing technologies. Some of the more interesting areas of interest are related to the usefulness of nuclear elemental spectroscopy data and the comparison of thermal and epithermal neutron porosity measurements, the measurement of in-situ permeability, the interpretation of electrical borehole image and borehole sonic data. A key parameter for reservoir characterization and simulation is formation permeability. A reasonable understanding of this property is key to the development of future gas hydrate production. Typical applications of borehole image data are an appreciation of a reservoir’s geological environment. In hydrate saturated reservoirs, borehole images can also be used to assist in the understanding of the gas migratory path to the hydrate bearing formation. This paper presents a review of some of the current state of the art geophysical log measurements and their application in hydrate saturated reservoirs..

Downhole acoustic data were acquired in very low-velocity, hydrate-bearing formations at five sites drilled on the Cascadia Margin during the Integrated Ocean Drilling Program (IODP) Expedition 311. P-wave velocity in marine sediments typically increases with depth as porosity decreases because of compaction. In general, Vp increases from ~1.6 at the seafloor to ~2.0 km/s ~300 m below seafloor at these sites. Gas hydrate-bearing intervals appear as high-velocity anomalies over this trend because solid hydrates stiffen the sediment. Logging-while-drilling (LWD) sonic technology, however, is challenged to recover accurate P-wave velocity in shallow sediments where velocities are low and approach the fluid velocity. Low formation Vp make the analysis of LWD sonic data difficult because of the strong effects of leaky-P wave modes, which typically have high amplitudes and are dispersive. We examine the frequency dispersion of borehole leaky-P modes and establish a minimum depth (approx 50-100 m) below the seafloor at each site where Vp can be accurately estimated using LWD data. Below this depth, Vp estimates from LWD sonic data compare well with wireline sonic logs and VSP interval velocities in nearby holes, but differ in detail due to local heterogeneity. We derive hydrate saturation using published models and the best estimate of Vp at these sites and compare results with independent resistivity-derived saturations.

Temporal variations in gas hydrate related geochemical signatures under different deposition conditions are the primary purposes of this study. Accreted wedge located offshore Southwestern Taiwan receives high terrigenous river materials, 100 MT/yr, at present time. It is not clear how seep environment varied during the past glacial. A 25 meters long piston core was taken offshore Southwestern Taiwan on r/v Marion DuFresne. Short piston cores and box cores were also taken on r/v OR-1. Samples were analyzed for pore water dissolved sulfide, sulfate, methane, chloride, del O18, calcium, magnesium, alkalinity, pH, and sediment AVS, pyrite, inorganic carbon, del O- 18, C13. Changes in deposition environment play a major role in the study area. Three stages of geochemical processes are identified in the 25 meters long core, interchange between reduce and oxic depositional environments, with reducing condition in the top 10 m, oxic in between 10-20 meter and reducing below the 20 meter. High concentrations of dissolved sulfide, rapid sulfate depletion, increase of methane, decrease of calcium were found in pore water in the top 10 m of sediments together with high concentrations of pyrite, relatively higher proportion of coarsegrained sediment. Concentrations of pyrite were very low in sediments between 15 to 20 meters but increased rapidly from 20 to 25 meters with a maximum concentration at 400 umol/g. Chloride concentrations also increased to a maximum concentration of 630 mM at 20 m. The rapid increase of chloride indicated gas hydrate formation at this depth. Authigenic carbonate nodules were found in sediments below 20 m. The carbonate content also increased rapidly beneath this depth. Stable isotopic carbon composition of the carbonate varied rapidly beneath 20 m with a low at -28 per mil. The existence of oxic/reducing alterations indicates that methane seep may vary in the past in the study area.

Hot water injection is a production technique proposed to gas recovery from methane hydrate reservoirs. However, from a practical point of view, the injected water experiences a drop in temperature and re-formation of hydrates may occur in the reservoir. In this work, we proposed a model expressing permeability hysteresis in the processes between hydrate growth and dissociation, and studied hydrate dissociation behavior during hot water injection. The model of permeability hysteresis was incorporated into the simulator MH21-HYDRES (MH21 Hydrate Reservoir Simulator), where the decrease in permeability with hydrate saturation during hydrate growth process was assumed to be much larger than the decrease during hydrate dissociation process. Laboratory hydrate dissociation experiments were carried out for comparison. In each experiment, we injected hot water at a constant rate into a sand-packed core bearing hydrates, and the histories of injection pressure, core temperature, and gas/water production rates were measured. Numerical simulations for the core experiments showed the re-formation of hydrates led to the increase in injection pressure during hot water injection. The simulated tendencies of pressure increase varied markedly by considering permeability hysteresis. Since the experimental pressure increases could not be reproduced without the permeability hysteresis model, the influence of permeability hysteresis should be considered to apply hot water injection to hydrate reservoirs.

Structure I and II gas hydrates were observed in the same sediment cores of a mud volcano in the Kukuy Canyon, Lake Baikal. The sII gas hydrate contained about 13-15% of ethane, whereas the sI gas hydrate contained about 1-5% of ethane and placed beneath the sII gas hydrate. We measured isotopic composition of dissociation gas from both type gas hydrates and dissolved gas in pore water. We found that ethane δD of sI gas hydrate (from -196 to -211 ‰) was larger than that of sII (from -215 to -220 ‰), whereas methane δ13C, methane δD and ethane δD in both hydrate structures were almost the same. δ13C of methane and ethane in gas hydrate seemed several permil smaller than those in pore water. These results support the following idea that the current gas in pore water is not the source of these gas hydrates of both structures. Isotopic data also provide useful information how the “double structure” gas hydrates formed.

Phase change materials (PCMs) are a viable option for compact thermal energy storage. Effective designs using PCMs require accurate knowledge of the thermal and physical properties, but for many PCMs these are not well known, and when known the knowledge is sometimes contradictory. Therefore, physical characteristics of several promising PCMs (K3PO4·7H2O, FeCl3·6H2O, Mn(NO3)2·4H2O) were determined. In addition, a life cycle assessment (LCA) of dodecanoic acid in a solar thermal energy storage system was carried out to determine the environmental impact for energy storage. This LCA showed that dodecanoic acid in a solar energy system would save energy and facilitate CO2 reductions. However, the economic cost is high and is unlikely to be implemented without incentives. Finally an experimental testbed for a solar thermal system utilizing dodecanoic acid was built. Preliminary measurements demonstrated the utility of this system.

This dissertation presents results from a complex seismic study using Ocean Bot¬tom Seismometers (OBS) conducted at a site of deep sea gas hydrate occurrence. The site is located on the accretionary margin of the northern Cascadia subduction zone offshore Vancouver Island. Canada. The major objectives for this study were the construction of a 3-D velocity model around the Bullseye vent zone by the means of travel time inversion tomography and the analysis of the amplitude data for reflections from the water-sediment interface and the bottom simulating reflector (BSR). Secondary objectives included the integration of the results from this study with previous knowledge about the vent zone for further clarification of its structure and evolution. The OBS seismic data set consisted of 22 parallel lines at 200 in spacing with three perpendicular crossing lines recorded on five OBS stations. Multichannel and single channel conventional seismic data along these lines were also acquired. The OBS experiment geometry required corrections for the coordinates of sources and receivers initially obtained in the field. A new comprehensive source and receiver localization technique was developed for the case of stationary hydrophones and multiple seismic lines. The horizontal size of the created 3-D velocity model is 3 km x 2.7 km. The modelled volume is limited by the seafloor at the top and by the BSR at the bottom. The size of a grid cell is 50 m x 50 m x 20 m. The uncertainty for the velocity value of individual cells was as low as 20 m/s. although the resolution of the model was reduced by the sparse receiver geometry. The inversion results indicate a fairly uniform velocity field around and inside the vent zone. Velocities are nearly equal to values expected for sediments containing no hydrate, which supports the idea that the bulk concentrations of gas hydrates are low at the site. The largest velocity anomaly with an amplitude of +25 m/s is spatially associated with the limits of the blank zone. The anomaly suggests greater gas hydrate concentrations inside the vent zone than outside. Low vertical resolution of the model did not provide information on the depth distribution of the hydrate. However, the combination of the information from the velocity inversion with previous studies suggests that the zone of high hydrate concentration (15-20% of the pore space) associated with a hydrate lens, located at the top of the sediment section. The vent site is characterized by a negative anomaly of the seafloor reflection coefficient, outlined by a high amplitude rim. The low reflection coefficient is believed to be the result of the processes taking place above the hydrate lens, methane venting in particular. and the high amplitude rim to be the effect of carbonate formation. The seafloor reflection coefficient zonation appears to be correlated with the distribution of low magnetic susceptibility zone in the first 8 in of the sediment section. Both phenomena can be related to the distribution of upward fluid flow at the vent site. The cause of the blanking phenomena is likely different for different frequencies of the seismic signal. The blanking at high frequencies is an effect of near-surface disturbed sediments due to active venting and, possibly. free gas presence at the top of the vent zone. The blanking for the middle range of seismic frequencies is mostly the effect of reduced impedance contrast between the sediment layers inside the blank zone due to local presence of gas hydrates in small concentrations (2-3%). It is concluded that. the Bullseye vent zone, which shows very low activity presently, was probably much more active in the past (similar to a mud volcano). The past ac¬tivity may have led to the formation of the bathymetric expression of the vent site (a mound), together with the hydrate lens and authigenic carbonates.

A number of MIR sensing platforms and methods were developed in this research work demonstrating potential applicability of MIR spectroscopy for studying hydrocarbon systems in extreme environments. First of all, the quantitative determination of the diamondoid compound adamantane in organic media utilizing IR-ATR spectroscopy at waveguide surfaces was established. The developed analytical strategy further enabled the successful detection of adamantane in real world crude oil samples. These reported efforts provide a promising outlook for detection and monitoring of diamondoid constituents in naturally occurring crudes and petroleum samples. IR-ATR spectroscopy was further utilized for evaluating and characterizing distribution, variations, and origin of carbonate minerals within sediment formations surrounding a hydrocarbon seep site - MC 118 in the Gulf of Mexico. An analytical model for direct detection of 13C-depleted authigenic carbonates associated with cold seep ecosystems was constructed. Potential applicability of IR-ATR spectroscopy as direct on-ship - and in future in situ - analytical tool for characterizing hydrocarbon seep sites was demonstrated. MIR evanescent field absorption spectroscopy was also utilized to expand the understanding on the role of surfactants during gas hydrate formation at surfaces. This experimental method allowed detailed spectroscopic observations of detergent-related surface processes during SDS mediated gas hydrate formation. The obtained IR data enabled proposing a mechanism by which SDS decreases the induction time for hydrate nucleation, and promotes hydrate formation. Potential of MIR fiberoptic evanescent field spectroscopy for studying surface effects during gas hydrate nucleation and growth was demonstrated. Next, quantifying trace amounts of water content in hexane using MIR evanescent field absorption spectroscopy is presented. The improvement in sensitivity and of limit of detection was obtained by coating an optical fiber with layer of a hydrophilic polymer. The application of the polymer layer has enabled the on-line MIR detection of water in hexane at low ppm levels. These results indicate that the MIR evanescent filed spectroscopy method shows potential for in-situ detection and monitoring of water in industrial oils and petroleum products. Finally, quantification of trace amounts of oil content in water using MIR evanescent field absorption spectroscopy is reported. Unmodified and modified with grafted hydrophobic polymer layer silver halide optical fibers were employed for the measurements. The surface modification of the fiber has enabled the on-line MIR analysis of crude oil in water at the low ppb level. Potential application of MIR fiber-optic evanescent field spectroscopy using polymer modified waveguides toward in-situ low level detection of crude oil in open waters was demonstrated.

[pt] Uma combinação de fatores geológicos e econômicos exige que as empresas produzam petróleo e gás em campos com profundidades de água cada vez maiores. Muitas das vezes não é econômico, ou no pior dos casos impraticável, instalar uma plataforma sobre os cabeçotes dos poços, por isso acaba se tornando comum transportar petróleo e gás através de amarras submarinas que podem ser de até 145km ou mais. Geralmente isso significa que as temperaturas são baixas o bastante e as pressões altas o suficiente para tornar aquele ambiente dentro do que chamamos de envelope de formação de hidrato e ações deverão ser tomadas afim de evitar os plugs de hidrato. Como resultado, a indústria foi forçada a intensificar sua pesquisa em químicos e sistemas que evitasse a formação da estrutura cristalina. Uma dessas pesquisas em estudo é a avaliação de um fluido modelo, emulsão A/O, analisando suas principais características e verificando as propriedades reológicas da estrutura cristalina em formação. Para tornar a pesquisa viável, este hidrato é formado a pressão atmosférica utilizando moléculas hóspedes que proporcionam essa formação em tal pressão e baixa temperatura. Logo, é utilizada uma substância líquida chamada ciclopentano, que substituirá o gás natural e irá proporcionar a formação do hidrato nestas novas condições. Dessa forma, este trabalho apresentou diferentes emulsões A/O, de acordo com a porcentagem de água, e reologia do hidrato formado para cada uma delas. / [en] A combination of geological and economic factors requires companies to produce oil and gas in fields with increasing water depths. It is often impractical to install a platform over the heads of the wells, so it is becoming common to transport oil and gas through underwater moorings that can be up to 145 km or more. Usually this means that the temperatures are low enough and the pressures high enough to make that environment into what we call a hydrate formation envelope and actions should be taken to avoid the hydrate plugs. As a result, the industry was forced to intensify its research into chemicals and systems that prevented the formation of the crystalline structure. One of these researches is the evaluation of a model fluid, A / O emulsion, analyzing its main characteristics and checking the rheological properties of the crystalline structure in formation. To make the search feasible, this hydrate is formed at atmospheric pressure using guest molecules that provide such formation at such pressure and low temperature. Therefore, a liquid substance called cyclopentane is used, which will replace the natural gas and will provide the formation of the hydrate under these new conditions. In this way, this work presented different A / O emulsions, according to the percentage of water, and rheology of the hydrate formed for each of them.

A straightforward means to include explicit hydrogen bonds within the Universal Force Field (UFF) is presented. Instead of treating hydrogen bonds as non-bonded interaction subjected to electrostatic and Lennard-Jones potentials, we introduce an explicit bond with a negligible bond order, thus maintaining the structural integrity of the H-bonded complexes and avoiding the necessity to assign arbitrary charges to the system. The explicit hydrogen bond changes the coordination number of the acceptor site and the approach is thus most suitable for systems with under-coordinated atoms, such as many metalorganic frameworks; however, it also shows an excellent performance for other systems involving a hydrogen-bonded framework. In particular, it is an excellent means for creating starting structures for molecular dynamics and for investigations employing more sophisticated methods. The approach is validated for the hydrogen bonded complexes in the S22 dataset and then employed for a set of metal-organic frameworks from the Computation-Ready Experimental database and several hydrogen bonded crystals including water ice and clathrates. We show that the direct inclusion of hydrogen bonds reduces the maximum error in predicted cell parameters from 66% to only 14%, and the mean unsigned error is similarly reduced from 14% to only 4%. We posit that with the inclusion of hydrogen bonding, the solvent-mediated breathing of frameworks such as MIL-53 is nowaccessible to rapid UFF calculations, which will further the aim of rapid computational scanning of metal-organic frameworks while providing better starting points for electronic structure calculations.